28868 Federal Register / Vol. 63, No. 100 /Tuesday, May 26, 1998 / Proposed Rules

ENVIRONMENTAL PROTECTION

AGENCY

40 CFR Part 136

[FRL–6100–5]

RIN 2040–AD07

Guidelines Establishing Test

Procedures for the Analysis of

Pollutants; Measurement of Mercury in

Water

AGENCY: Environmental Protection

Agency (EPA).

ACTION: Proposed rule.

SUMMARY: This proposed regulation

would amend the guidelines

establishing test procedures for the

analysis of pollutants under the Clean

Water Act by adding Method 1631:

Mercury in Water by Oxidation, Purge

and Trap, and Cold Vapor Atomic

Fluorescence. EPA Method 1631 was

developed in order to measure mercury

reliably at the low levels associated with

ambient water quality criteria (WQC).

EPA has promulgated WQC for mercury

at 12 parts-per-trillion (ppt) in the

National Toxics Rule, and published

guidance criteria for mercury at 1.8 ppt

in the Water Quality Guidance for the

Great Lakes System. EPA Method 1631

would need to be used in conjunction

with clean sampling and laboratory

techniques to preclude contamination at

the low ppt levels necessary for mercury

determinations. EPA has developed

guidance documents on sampling and

clean rooms for trace metals, including

mercury.

DATES: Comments on this proposal must

be submitted on or before July 27, 1998.

ADDRESSES: Send written comments on

the proposed rule to ‘‘Method 1631’’

Comment Clerk (Docket # W–98–15);

Water Docket (4101); Environmental

Protection Agency; 401 M Street, SW;

Washington, DC 20460. Commenters are

requested to submit any references cited

in their comments. Commenters are also

requested to submit an original and

three copies of their written comments

and enclosures. Commenters that want

receipt of their comments acknowledged

should include a self addressed,

stamped envelope. All comments must

be postmarked or delivered by hand. No

facsimiles (faxes) will be accepted.

Data availability: A copy of the

supporting documents cited in this

proposal is available for review at EPA’s

Water Docket; 401 M Street, SW, East

Tower Basement, Washington, DC

20460. For access to docket materials,

call (202) 260–3027 between 9:00 a.m.

and 3:30 p.m. for an appointment. An

electronic version of Method 1631 is

available via the Internet on EPA’s

Internet home page at http://

www.epa.gov/OST.

FOR FURTHER INFORMATION CONTACT:

Maria Gomez-Taylor, Ph.D., Engineering

and Analysis Division (4303), USEPA

Office of Science and Technology, 401

M Street, SW, Washington, DC 20460; or

call (202) 260–1639.

SUPPLEMENTARY INFORMATION:

Potentially Affected Entities

EPA Regions, as well as States,

Territories and Tribes authorized to

implement the National Pollutant

Discharge Elimination System (NPDES)

program, issue permits that comply with

the technology-based and water qualitybased requirements of the Clean Water

Act. In doing so, the NPDES permitting

authority, including authorized States,

Territories, and Tribes, make a number

of discretionary choices associated with

permit writing, including the selection

of pollutants to be measured and, in

many cases, limited in permits. If EPA

has ‘‘approved’’ standardized testing

procedures (i.e., promulgated through

rulemaking) for a given pollutant, the

NPDES permit must include one of the

approved testing procedures or an

approved alternate test procedure.

Therefore, entities with NPDES permits

could be affected by the standardization

of testing procedures in this rulemaking.

These entities may be affected because

NPDES permits may incorporate one of

the standardized testing procedures in

today’s rulemaking. In addition, when a

State, Territory, or authorized Tribe

provides certification of federal licenses

under Clean Water Act section 401,

States, Territories and Tribes are

directed to use the standardized testing

procedures. Categories and entities that

may ultimately be affected include:

Category Examples of potentially affected entities

State and Territorial Governments and Indian Tribes ....... States, Territories, and Tribes authorized to administer the NPDES permitting program; States, Territories, and Tribes providing certification under Clean Water Act

section 401; Governmental NPDES permittees.

Industry ............................................................................... Industrial NPDES permittees.

Municipalities ...................................................................... Publicly-owned treatment works with NPDES permits.

This table is not intended to be

exhaustive, but rather provides a guide

for readers regarding entities likely to be

affected by this action. This table lists

the types of entities that EPA is now

aware could potentially be affected by

this action. Other types of entities not

listed in the table could also be affected.

If you have questions regarding the

applicability of this action to a

particular entity, consult the person

listed in the preceding FOR FURTHER

INFORMATION CONTACT section.

I. Authority

Today’s proposal is pursuant to the

authority of sections 301, 304(h), and

501(a) of the Clean Water Act (CWA), 33

U.S.C. 1314(h), 1361(a) (the ‘‘Act’’).

Section 301 of the Act prohibits the

discharge of any pollutant into

navigable waters unless the discharge

complies with a National Pollutant

Discharge Elimination System (NPDES)

permit, issued under section 402 of the

Act. Section 304(h) of the Act requires

the Administrator of the EPA to

‘‘promulgate guidelines establishing test

procedures for the analysis of pollutants

that shall include the factors which

must be provided in any certification

pursuant to section 401 of this Act or

permit applications pursuant to section

402 of this Act.’’ Section 501(a) of the

Act authorizes the Administrator to

‘‘prescribe such regulations as are

necessary to carry out his function

under this Act.’’ EPA publishes CWA

analytical method regulations at 40 CFR

part 136. The Administrator also has

made these test procedures applicable to

monitoring and reporting of NPDES

permits (40 CFR part 122, § 122.21,

122.41, 122.44, and 123.25), and

implementation of the pretreatment

standards issued under section 307 of

the Act (40 CFR part 403, § 403.10 and

402.12).

II. Background

A. Mercury

Mercury is a toxic pollutant pursuant

to section 307(a)(1) of CWA (see the list

of toxic pollutants at 40 CFR 401.15)

and is a priority pollutant as derived

from the toxic pollutant list (see 40 CFR

423, Appendix A). Available EPA

approved methods for mercury
Federal Register / Vol. 63, No. 100 /Tuesday, May 26, 1998 / Proposed Rules 28869

determine inorganic and organic forms

of mercury as ‘‘total mercury.’’

B. Methods for Determination of

Mercury

Methods currently approved at 40

CFR part 136 measure mercury by

purging mercury vapor from a water

sample into a specially designed

chamber placed in the light beam of an

atomic absorption spectrophotometer. In

contrast, EPA Method 1631 measures

mercury by purging mercury vapor from

a water sample onto a gold trap and

thermally desorbing the mercury from

the trap into an atomic fluorescence

spectrometer. Purging the mercury onto

the gold trap concentrates the mercury

and allows water vapor from the sample

to be vented, and use of atomic

fluorescence provides an increased

response compared to atomic

absorption. As a result, EPA Method

1631 is approximately 200 times more

sensitive than currently approved

methods for determination of mercury.

C. Need for Improved Method for

Mercury

The most sensitive currently

approved methods for mercury are

capable of achieving a quantitation level

of 200 ng/L (parts-per-trillion; ppt).

These methods are not sensitive enough

to measure mercury at levels called for

under the National Toxics Rule (40 CFR

131.36) and the Water Quality Guidance

for the Great Lakes System (60 FR

15366)—12 ppt and 1.8 ppt,

respectively.

III. Summary of Proposed Rule

A. Introduction

This proposed rule would make

available at 40 CFR part 136 an

additional test procedure for

measurement of mercury. This

rulemaking does not propose to repeal

any of the currently approved methods

that test for mercury. For an NPDES

permit, the permitting authority should

decide the appropriate method based on

the circumstances of the particular

effluent measured. Use of EPA Method

1631 may be specified by the permitting

authority when a permit is modified or

reissued. If the permitting authority

does not specify the method to be used,

a discharger would be able to use EPA

Method 1631 or any of the currently

approved methods for determination of

mercury, provided that the method

chosen meets the requirements specified

in the permit.

B. Summary of Proposed Method 1631

EPA Method 1631 has four procedural

components: sample pretreatment;

purge and trap; desorption; and

detection by atomic fluorescence. In the

sample pretreatment step, bromine

monochloride (BrCl) is added to the

sample to oxidize all forms of mercury

to Hg(II). After oxidation, the sample is

sequentially prereduced with

NH2OH•HCl to destroy free halogens,

then reduced with SnCl2 to convert

Hg(II) to volatile Hg(0). The Hg(0) is

purged from the aqueous solution with

nitrogen onto a gold-coated sand trap.

The trapped mercury is thermally

desorbed from the gold trap into a

flowing gas stream into the cell of a

cold-vapor atomic fluorescence

spectrometer. Quality is assured through

calibration and testing of the oxidation,

purging, and detection systems.

C. Sample Contamination

Trace levels of metals are ubiquitous

in the environment. Therefore, the

determination of trace metals at the

levels of interest for water quality

criteria necessitates the use of clean

sample handling techniques to preclude

false positives arising from sample

collection, handling, or analysis. EPA

has released several guidance

documents that are designed to ensure

that metals data accurately reflect actual

environmental levels. The guidance

documents include: Method 1669:

Sampling Ambient Water for Trace

Metals at EPA Water Quality Criteria

Levels; Guidance on Establishing Trace

Metals Clean Rooms in Existing

Facilities; and Guidance on

Documentation and Evaluation of Trace

Metals Data Collected for Clean Water

Act Compliance Monitoring. The most

serious problem faced by laboratories

conducting metals analyses at these very

low levels is the potential for sample

contamination during sample collection

and handling. Mercury is particularly

difficult to collect due to its ubiquity in

the environment. For example,

commonly used polyethylene sample

containers are unacceptable for sample

storage because atmospheric mercury

would be expected to diffuse through

the walls of the container, causing

sample contamination. EPA’s Method

1669 (Sampling Method) details the

rigorous sample handling and quality

control (QC) procedures necessary to

produce reliable data for mercury at the

levels of interest for water quality

criteria.

D. Quality Control

The quality control (QC) in EPA

Method 1631 is more extensive than the

QC in currently approved methods for

mercury. EPA Method 1631 contains all

of the standardized QC tests proposed in

EPA’s streamlining initiative (62 FR

14976) and used in the 40 CFR 136

Appendix A methods. An initial

demonstration of laboratory capability is

required and consists of: (1) a method

detection limit (MDL) study to

demonstrate that the laboratory is able

to achieve the MDL and minimum level

of quantification (ML) specified in

Method 1631; and (2) an initial

precision and recovery (IPR) test,

consisting of the analysis of four reagent

water samples spiked with mercury, to

demonstrate the laboratory’s ability to

generate acceptable precision and

recovery.

Ongoing QC would consist of the

following tests that would need to

accompany each analytical batch (i.e., a

set of 20 samples or less pretreated at

the same time):

• Verification of calibration of the

purge and trap and atomic fluorescence

systems, to verify that instrument

response has not deviated significantly

from that obtained during calibration.

• Analysis of a matrix spike (MS) and

matrix spike duplicate (MSD) to

demonstrate method accuracy and

precision and to monitor matrix

interferences.

• Analysis of reagent and bubbler

blanks to demonstrate freedom from

contamination.

• Analysis of a laboratory control

sample and ongoing precision and

recovery (OPR) samples to demonstrate

that the method remains under control.

EPA Method 1631 contains QC

acceptance criteria for all QC tests.

Compliance with these criteria would

allow a data user to evaluate the quality

of the results. These QC acceptance

criteria would increase the reliability of

results and provides a means for

laboratories and data users to monitor

analytical performance, thereby

providing a basis for sound, defensible

data.

E. Performance Based Measurement

System

On October 7, 1997, EPA published a

Notice of the Agency’s intent to

implement a Performance Based

Measurement System (PBMS) in all of

its programs to the extent feasible (62

FR 52098). The Agency is currently

determining the specific steps necessary

to implement PBMS in its programs and

preparing an implementation plan.

Because final decisions have not yet

been made concerning the

implementation of PBMS in water

programs, today’s proposed method

does not include full provisions for

PBMS.

However, consistent with the

Streamlining Initiative proposed on

March 28, 1997 (62 FR 14976), EPA

Method 1631, as proposed, would
28870 Federal Register / Vol. 63, No. 100 /Tuesday, May 26, 1998 / Proposed Rules

employ a performance-based approach

to the sample preparation and trapping

systems. Analysts would be allowed to

modify the sample preparation and

trapping aspects of the method provided

all the performance criteria are met. The

method also allows the use of alternate

reagents and hardware provided that

equivalent or superior performance is

demonstrated and all QC acceptance

criteria are met.

Demonstrating equivalency involves

two sets of tests, one set with reference

standards and the other with the sample

matrix. The equivalency procedures

include performance of the IPR test

using reference standards to

demonstrate that the results produced

with the modified procedure would

meet or exceed the QC acceptance

criteria in EPA Method 1631. In

addition, if the detection limit may be

affected by a modification, performance

of an MDL study would be required to

demonstrate that the modified

procedure could achieve an MDL less

than or equal to the MDL in EPA

Method 1631 or, for those instances in

which the regulatory compliance level

is greater than the ML in the method,

one-third the regulatory compliance

level. (For a discussion of these levels,

see EPA Method 1631 or the

Streamlining Initiative proposed in

March of 1997 (62 FR 14976).

Once EPA has made its final

determinations regarding

implementation of PBMS in programs

under the Clean Water Act, EPA Method

1631 would be amended to incorporate

specific provisions of PBMS. We

anticipate that such changes will be

included in the final version of the

method. Commenters are encouraged to

address PBMS implementation for this

method and are specifically requested to

comment on the performance

characteristics of EPA Method 1631 to

assist EPA in developing practical

method performance and related criteria

for PBMS implementation.

IV. Development and Validation of

Method 1631

EPA Method 1631 is based on

techniques published in the literature

and widely used throughout the marine

chemistry community. EPA validated

the method during development in

multiple single-laboratory studies and

in an interlaboratory (round-robin)

method validation study.

A. Background

In response to the need for measuring

of trace metals at ambient water quality

criteria levels set forth in the National

Toxics Rule, EPA convened a panel of

trace metals experts in Boston in

November, 1993. The purpose of the

meeting was to obtain information on

modern laboratory techniques for the

analysis of trace metals. This panel

consisted of mostly marine chemists

who had been making trace metals

measurements in the marine

environment for more than 10 years.

The panel concluded that the technique

of oxidation, purge and trap, desorption,

and atomic fluorescence would provide

reliable results for measurements of

mercury at low ppt levels.

B. Initial Method Development

Initial method development was

carried out under contract in a marine

chemistry laboratory recognized for

expertise in measurements of mercury at

ultra-trace levels. EPA received an

initial draft of the method in late 1994.

EPA revised the initial draft into EPA’s

Environmental Monitoring Management

Council (EMMC) format in early 1995

and added the standardized quality

control (QC) used in the 40 CFR 136,

Appendix A methods. Initial QC

acceptance criteria were developed from

data provided by the Agency contractor

responsible for initial method

development.

C. Multiple Single-Laboratory

Validation Studies

In 1996, EPA conducted studies in

four laboratories to further assess

method performance and to better

define the method detection limit (MDL)

and QC acceptance criteria. Each

laboratory performed an MDL study and

an initial precision and recovery test.

EPA revised the draft method based on

results and comments received from

these studies. Based on these data, EPA

selected an MDL of 0.2 ng/L (0.2 ppt) for

EPA Method 1631. This was the highest

of the MDLs achieved by any of the

laboratories. The highest MDL was

selected because this MDL was well

below the 1.8 ppt ambient water quality

criterion required by the Great Lakes

Initiative. EPA established a minimum

level of quantitation of 0.5 ng/L and

revised the QC acceptance criteria for

EPA Method 1631 based on data from

the four laboratories in the validation

study. Details of the studies are given in

a study plan and a report of the studies

is included in the docket for today’s

proposed rule.

D. Interlaboratory Validation Study

In mid-1997, EPA developed a study

plan to conduct an interlaboratory

validation of EPA Method 1631. The

interlaboratory validation study was

conducted in late 1997. The following

matrices, forms, and levels were

studied: total mercury in reagent water

at four levels; total and dissolved

mercury in effluent at one level;

dissolved mercury in freshwater at four

levels, and total and dissolved mercury

in seawater at one level. In addition,

each laboratory performed an MDL

study to demonstrate that the MDL of

0.2 ppt could be achieved. All the

laboratories participating in the study

achieved an MDL below 0.2 ppt.

Therefore, EPA believes this MDL is

reasonable. The study plan and a report

of the study are contained in the Docket.

Results and comments from the study

were used to evaluate the QC

acceptance criteria and revise other

details of EPA Method 1631 into the

version being proposed today. The

performance characteristics of the

method are summarized in Tables 1–3.

EPA invites comment and additional

data on the performance characteristics

of this method.

V. Status of Currently Approved

Methods

This action proposes to make EPA

Method 1631 available for

determination of mercury in aqueous

samples ranging from seawater to

sewage effluent. Currently approved

methods for determination of mercury,

EPA Methods 245.1 and 245.2, Standard

Method 3112B, ASTM Method D3223–

91, USGS Method I–3462–85, and

AOAC-International Method 977.22,

would not be withdrawn or otherwise

affected by this regulation. EPA

specifically invites comment on this

aspect of the proposal, including the

possible consequences and solutions if

EPA were to withdraw such methods.

VI. Regulatory Requirements

A. Executive Order 12866

Under Executive Order 12866 (58 FR

51735 (October 4, 1993)) the Agency

must determine whether a regulatory

action is ‘‘significant’’ and therefore

subject to OMB review and the

requirements of the Executive Order.

The Order defines ‘‘significant

regulatory action’’ as one that is likely

to result in a rule that may: (1) Have an

annual effect on the economy of $100

million or more or adversely affect in a

material way the economy, a sector of

the economy, productivity, competition,

jobs, the environment, public health or

safety, or State, local, or tribal

governments or communities; (2) create

a serious inconsistency or otherwise

interfere with an action taken or

planned by another agency; (3)

materially alter the budgetary impact of

entitlements, grants, user fees, or loan

programs or the rights and obligations of

recipients thereof; or (4) raise novel
Federal Register / Vol. 63, No. 100 /Tuesday, May 26, 1998 / Proposed Rules 28871

legal or policy issues arising out of legal

mandates, the President’s priorities, or

the principles set forth in the Executive

Order.

It has been determined that this rule

is not a ‘‘significant regulatory action’’

under the terms of Executive Order

12866 and is therefore not subject to

OMB review.

B. Unfunded Mandates Reform Act

Title II of the Unfunded Mandates

Reform Act of 1995 (UMRA), P.L. 104–

4, establishes requirements for Federal

agencies to assess the effects of their

regulatory actions on State, local, and

tribal governments and the private

sector. Under section 202 of UMRA,

EPA generally must prepare a written

statement, including a cost-benefit

analysis, for proposed and final rules

with ‘‘Federal mandates’’ that may

result in expenditures to State, local,

and tribal governments, in the aggregate,

or to the private sector, of $100 million

or more in any one year. Before

promulgating an EPA rule for which a

written statement is needed, section 205

of UMRA generally requires EPA to

identify and consider a reasonable

number of regulatory alternatives and

adopt the least costly, most costeffective, or least burdensome

alternative that achieves the objectives

of the rule. The provisions of section

205 do not apply when they are

inconsistent with applicable law.

Moreover, section 205 allows EPA to

adopt an alternative other than the least

costly, most cost-effective, or least

burdensome alternative if the

Administrator publishes with the final

rule an explanation why that alternative

was not adopted. Before EPA establishes

any regulatory requirements that may

significantly or uniquely affect small

governments, including tribal

governments, it must have developed

under section 203 of UMRA a small

government agency plan. The plan must

provide for notifying potentially

affected small governments, enabling

officials of affected small governments

to have meaningful and timely input in

the development of EPA regulatory

proposals with significant Federal

intergovernmental mandates, and

informing, educating, and advising

small governments on compliance with

the regulatory requirements.

Today’s proposed rule contains no

Federal mandates (under the regulatory

provisions of Title II of the UMRA) for

State, local, or Tribal governments or

the private sector. The proposed rule

would impose no enforceable duty on

any State, local or Tribal governments or

the private sector. This rule proposes

alternative analytical test procedures

which would merely standardize the

procedures when testing is otherwise

required by a regulatory agency.

Therefore, the proposed rule is not

subject to the requirements of sections

202, 203, and 205 of the UMRA. EPA

invites comment on its conclusions

regarding whether alternate test

procedures constitute a federal mandate.

C. Regulatory Flexibility Act

Under the Regulatory Flexibility Act

(RFA), EPA generally is required to

conduct a regulatory flexibility analysis

describing the impact of the regulatory

action on small entities as part of

rulemaking. However, under section

605(b) of the RFA, if EPA certifies that

the rule will not have a significant

economic impact on a substantial

number of small entities, EPA is not

required to prepare a regulatory

flexibility analysis. Pursuant to section

605(b) of the Regulatory Flexibility Act,

5 U.S.C. 605(b), the Administrator

certifies that this rule will not have a

significant economic impact on a

substantial number of small entities.

This regulation approves an additional

test procedure (analytical method) for

the measurement of mercury. This rule

makes available an alternative testing

procedure for use in compliance

monitoring and data gathering but does

not require its use.

D. Paperwork Reduction Act

In accordance with the Paperwork

Reduction Act, 44 U.S.C. 3501 et seq.,

EPA must submit an information

collection request covering information

collection requirements in proposed

rules to the Director of the Office of

Management and Budget (OMB) for

review and approval. This proposed

rule contains no information collection

requirements. Therefore, an information

collection request will not be submitted

to OMB.

E. National Technology Transfer and

Advancement Act

Under section 12(d) of the National

Technology Transfer and Advancement

Act (NTTAA), the Agency is required to

use voluntary consensus standards in its

regulatory activities unless to do so

would be inconsistent with applicable

law or otherwise impractical. Voluntary

consensus standards are technical

standards (e.g., materials specifications,

test methods, sampling procedures,

business practices, etc.) that are

developed or adopted by voluntary

consensus standard bodies. Where

available and potentially applicable

standards are not used by EPA, the

NTTAA requires the Agency to provide

Congress, through the Office of

Management and Budget (OMB), an

explanation for the reasons for not using

such standards.

Proposal of EPA Method 1631 is the

result of a need to determine mercury at

the low levels associated with water

quality criteria for mercury in the

National Toxics Rule (40 CFR 131.36)

and in the Water Quality Guidance for

the Great Lakes System (60 FR 15366).

These documents specify concentrations

for mercury in the low part-per-trillion

range and the currently approved

methods are not sensitive enough to

measure mercury at these levels. EPA’s

search of the technical literature

revealed that there are no consensus

standards for determination of mercury

capable of measuring this pollutant at

these low levels. EPA invites public

comments on the Agency’s proposal as

well as on any other existing,

potentially applicable voluntary

consensus standards that the Agency

should consider for the determination of

mercury at low ppt levels.

F. Executive Order 13045: Protection of

Children From Environmental Health

Risks and Safety Risks

Executive Order 13045 (62 FR 19885,

April 23, 1997), applies to any rule that

(1) is likely to be ‘‘economically

significant’’ as defined under Executive

Order 12866, and (2) concerns

environmental health or safety risk that

the Agency has reason to believe may

have a disproportionate effect on

children. If a regulatory action meets

both criteria, the Agency must evaluate

the environmental health or safety

effects of the planned rule on children,

and explain why the planned regulation

is preferable to other potentially

effective and reasonably feasible

alternatives considered by the Agency.

This rule is not subject to E.O. 13045,

‘‘Protection of Children from

Environmental Health Risks and Safety

Risks’’ because this is not an

‘‘economically significant’’ regulatory

action as defined by E.O. 12866, and

because it does not involve decisions on

environmental health or safety risks that

may disproportionately affect children.

VII. Request for Comments

EPA requests public comments and

information on this proposed rule.

Specifically, EPA invites comment on

the appropriateness of Method 1631 for

the measurement of mercury at low ppt

levels, the utility of EPA Method 1631

for NPDES compliance monitoring, the

MDL and QC acceptance criteria

specified in Method 1631, and EPA’s

proposed decision not to withdraw

other, existing, approved methods for

determination of mercury.
28872 Federal Register / Vol. 63, No. 100 /Tuesday, May 26, 1998 / Proposed Rules

List of Subjects in 40 CFR Part 136

Environmental protection, Analytical

methods, Monitoring, Reporting and

recordkeeping requirements, Waste

treatment and disposal, Water pollution

control.

Dated: May 15, 1998.

Carol M. Browner,

Administrator.

In consideration of the preceding,

USEPA proposes to amend title 40,

chapter I of the Code of Federal

Regulations part 136 as follows:

PART 136—[AMENDED]

1. The authority citation for part 136

continues to read as follows:

Authority: Secs. 301, 304(h), 307, and

501(a) Pub. L. 95–217, Stat. 1566, et seq. (33

U.S.C. 1251, et seq.) (The Federal Water

Pollution Control Act Amendments of 1972

as amended by the Clean Water Act of 1977

and the Water Quality Act of 1987), 33 U.S.C.

1314 and 1361; 86 Stat. 816, Pub. L. 92–500;

91 Stat. 1567, Pub. L. 92–217; Stat. 7, Pub.

L. 100–4 (The ‘‘Act’’).

2. In § 136.3, paragraph (a), Table

IB.—List of Approved Inorganic Test

Procedures, is amended by revising

entry 35 to read as follows:

§ 136.3 Identification of test procedures.

(a) * * *

TABLE IB.—LIST OF APPROVED INORGANIC TEST PROCEDURES

Parameter, units and method

Reference (method number or page)

EPA1,35

Standard

methods 18th

Ed.

ASTM USGS2 Other

* * * * * * *

35. Mercury—Total,4

Cold vapor, manual, or (or μg/L) ................................................ 245.1 3112–B D3223–91 I3462–85 3 977.22

Automated (μg/L) ........................................................................ 245.2 ....................

Oxidation, purge and trap, and atomic fluorescence (ng/L) ....... 1631 ....................

* * * * * * *

Table IB Notes:

1 ‘‘Methods for Chemical Analysis of Water and Wastes’’, Environmental Protection Agency, Environmental Monitoring Systems Laboratory-Cincinnati (EMSL–CI), EPA–600/4–79–020, Revised March 1983 and 1979 where applicable. 2Fishman, M.J., et al, ‘‘Methods for Analysis of Inorganic Substances in Water and Fluvial Sediments,’’ U.S. Department of the Interior, Techniques of Water—Resource Investigations of the U.S. Geological Survey, Denver, CO, Revised 1989, unless otherwise stated. 3Official Methods of Analysis of the Association of Official Analytical Chemists,’’ methods manual, 15th ed. (1990).

4For the determination of total metals the sample is not filtered before processing. A digestion procedure is required to solubilize suspended

material and to destroy possible organic-metal complexes. Two digestion procedures are given in ‘‘Methods for Chemical Analysis of Water and

Wastes, 1979 and 1983’’. One (section 4.1.3), is a vigorous digestion using nitric acid. A less vigorous digestion using nitric and hydrochloric

acids (section 4.1.4) is preferred; however, the analyst should be cautioned that this mild digestion may not suffice for all sample types. Particularly, if a colorimetric procedure is to be employed, it is necessary to ensure that all organo-metallic bonds be broken so that the metal is in a reactive state. In those situations, the vigorous digestion is to be preferred making certain that at no time does the sample go to dryness. Samples

containing large amounts of organic materials may also benefit by this vigorous digestion, however, vigorous digestion with concentrated nitric

acid will convert antimony and tin to insoluble oxides and render them unavailable for analysis. Use of ICP/AES as well as determinations for

certain elements such as antimony, arsenic, the noble metals, mercury, selenium, silver, tin, and titanium require a modified sample digestion

procedure and in all cases the method write-up should be consulted for specific instructions and/or cautions.

NOTE TO TABLE IB NOTE 4: If the digestion procedure for direct aspiration AA included in one of the other approved references is different

than the above, the EPA procedure must be used.

Dissolved metals are defined as those constituents which will pass through a 0.45 micron membrane filter. Following filtration of the sample,

the referenced procedure for total metals must be followed. Sample digestion of the filtrate for dissolved metals (or digestion of the original sample solution for total metals) may be omitted for AA (direct aspiration or graphite furnace) and ICP analyses, provided the sample solution to be

analyzed meets the following criteria:

a. has a low COD (<20)

b. is visibly transparent with a turbidity measurement of 1 NTU or less

c. is colorless with no perceptible odor, and

d. is of one liquid phase and free of particulate or suspended matter following acidification.

* * * * * * *

35Precision and recovery statements for the atomic absorption direct aspiration and graphite furnace methods, and for the spectrophotometric

SDDC method for arsenic are provided in Appendix D of this part titled, ‘‘Precision and Recovery Statements for Methods for Measuring Metals’’.

* * * * * * *

3. In part 136, appendix A is amended

by adding EPA Method 1631 to read as

follows:

Appendix A to Part 136—Methods for

Organic Chemical Analysis of

Municipal and Industrial Wastewater

* * * * *

Method 1631 Mercury in Water by

Oxidation, Purge and Trap, and CVAFS

1.0 Scope and Application

1.1 This Method is for determination of

mercury (Hg) in filtered and unfiltered water

by oxidation, purge and trap, desorption, and

cold-vapor atomic fluorescence spectrometry

(CVAFS). This Method is for use in EPA’s

data gathering and monitoring programs

associated with the Clean Water Act, the

Resource Conservation and Recovery Act, the

Comprehensive Environmental Response,

Compensation and Liability Act, and the Safe

Drinking Water Act. The Method is based on

a contractor-developed method (Reference 1)

and on peer-reviewed, published procedures

for the determination of mercury in aqueous

samples, ranging from sea water to sewage

effluent (References 2–5).

1.2 This Method is accompanied by

Method 1669: Sampling Ambient Water for

Determination of Trace Metals at EPA Water

Quality Criteria Levels (Sampling Method).

The Sampling Method guidance document is

recommended to preclude contamination

during the sampling process.

1.3 This Method is for determination of

Hg in the range of 0.5–100 ng/L and may be

extended to higher levels by selection of a

smaller sample size.

1.4 The ease of contaminating ambient

water samples with mercury and interfering

substances cannot be overemphasized. This

Method includes suggestions for

improvements in facilities and analytical

techniques that should minimize

contamination and maximize the ability of

the laboratory to make reliable trace metals
Federal Register / Vol. 63, No. 100 /Tuesday, May 26, 1998 / Proposed Rules 28873

determinations. Section 4.0 gives these

suggestions.

1.5 The detection limit and minimum

level of quantitation in this Method usually

are dependent on the level of interferences

rather than instrumental limitations. The

method detection limit (MDL; 40 CFR 136,

Appendix B) for Hg has been determined to

be 0.2 ng/L when no interferences are

present. The minimum level (ML) has been

established as 0.5 ng/L. An MDL as low as

0.05 ng/L can be achieved for low Hg

samples by using a larger sample volume, a

lower BrCl level (0.2%), and extra caution in

sample handling.

1.6 Clean and ultraclean—The terms

‘‘clean’’ and ‘‘ultraclean’’ have been applied

to the techniques needed to reduce or

eliminate contamination in trace metals

determinations. These terms are not used in

this Method because they lack an exact

definition. However, the information

provided in this Method is consistent with

the summary guidance on clean and

ultraclean techniques (References 6–7).

1.7 This Method follows the EPA

Environmental Methods Management

Council’s ‘‘Guidelines and Format for

Methods to Be Proposed at 40 CFR, Part 136

or Part 141.’’

1.8 This Method is ‘‘performance based.’’

The analyst is permitted to modify the

Method to overcome interferences or lower

the cost of measurements if all performance

criteria are met. Section 9.1.2 gives the

requirements for establishing method

equivalency.

1.9 Any modification of this Method,

beyond those expressly permitted, shall be

considered a major modification subject to

application and approval of alternate test

procedures under 40 CFR 136.4 and 136.5.

1.10 This Method should be used only by

analysts who are experienced in the use of

CVAFS techniques and who are trained

thoroughly in the sample handling and

instrumental techniques described in this

Method. Each analyst who uses this Method

must demonstrate the ability to generate

acceptable results using the procedure in

Section 9.2.

1.11 This Method is accompanied by a

data verification and validation guidance

document, Guidance on the Documentation

and Evaluation of Trace Metals Data

Collected for CWA Compliance Monitoring

(Reference 8).

2.0 Summary of Method

2.1 A 100- to 2000-mL sample is collected

directly into a specially cleaned, pretested,

fluoropolymer bottle using sample handling

techniques specially designed for collection

of mercury at trace levels (Reference 9).

2.2 For dissolved Hg, the sample is

filtered through a 0.45-μm capsule filter.

2.3 The sample is preserved by adding

either 5 mL/L of pretested 12N HCl or

5mL/L BrCl solution. If a sample will also be

used for the determination of methyl

mercury, it should be preserved with 5 mL/

L HCl solution only.

2.4 Prior to analysis, a 100-mL sample

aliquot is placed in a specially designed

purge vessel, and 0.2N BrCl solution is added

to oxidize all Hg compounds to Hg(II).

2.5 After oxidation, the sample is

sequentially prereduced with NH2OH. HCl to

destroy the free halogens, and then reduced

with SnCl2 to convert Hg(II) to volatile Hg(0).

2.6 The Hg(0) is separated from solution

by purging with nitrogen onto a gold-coated

sand trap (Figure 1).

2.7 The trapped Hg is thermally desorbed

from the gold trap into an inert gas stream

that carries the released Hg(0) into the cell of

a cold-vapor atomic fluorescence

spectrometer (CVAFS) for detection (Figure

2).

2.8 Quality is ensured through calibration

and testing of the oxidation, purging, and

detection systems.

3.0 Definitions

3.1 Total mercury—all BrCl-oxidizable

mercury forms and species found in an

unfiltered aqueous solution. This includes,

but is not limited to, Hg(II), Hg(0), strongly

organo-complexed Hg(II) compounds,

adsorbed particulate Hg, and several tested

covalently bound organo-mercurials (e.g.,

CH3HgCl, (CH3)2Hg, and C6H5HgOOCCH3).

The recovery of Hg bound within microbial

cells may require the additional step of UV

photo-oxidation. In this Method, total

mercury and total recoverable mercury are

synonymous.

3.2 Dissolved mercury—All BrCloxidizable mercury forms and species found

in the filtrate of an aqueous solution that has

been filtered through a 0.45 micron filter.

3.3 Apparatus—Throughout this Method,

the sample containers, sampling devices,

instrumentation, and all other materials and

devices used in sample collection, sample

processing, and sample analysis that come in

contact with the sample and therefore require

careful cleaning will be referred to

collectively as the Apparatus.

3.4 Definitions of other terms used in this

Method are given in the glossary at the end

of the Method.

4.0 Contamination and Interferences

4.1 Preventing ambient water samples

from becoming contaminated during the

sampling and analysis process constitutes

one of the greatest difficulties encountered in

trace metals determinations. Over the last

two decades, marine chemists have come to

recognize that much of the historical data on

the concentrations of dissolved trace metals

in seawater are erroneously high because the

concentrations reflect contamination from

sampling and analysis rather than ambient

levels. Therefore, it is imperative that

extreme care be taken to avoid contamination

when collecting and analyzing ambient water

samples for trace metals.

4.2 Samples may become contaminated

by numerous routes. Potential sources of

trace metals contamination during sampling

include: metallic or metal-containing labware

(e.g., talc gloves that contain high levels of

zinc), containers, sampling equipment,

reagents, and reagent water; improperly

cleaned and stored equipment, labware, and

reagents; and atmospheric inputs such as dirt

and dust. Even human contact can be a

source of trace metals contamination. For

example, it has been demonstrated that

dental work (e.g., mercury amalgam fillings)

in the mouths of laboratory personnel can

contaminate samples that are directly

exposed to exhalation (Reference 5).

4.3 Contamination Control.

4.3.1 Philosophy—The philosophy

behind contamination control is to ensure

that any object or substance that contacts the

sample is metal free and free from any

material that may contain mercury.

4.3.1.1 The integrity of the results

produced cannot be compromised by

contamination of samples. This Method and

the Sampling Method give requirements and

suggestions for control of sample

contamination.

4.3.1.2 Substances in a sample cannot be

allowed to contaminate the laboratory work

area or instrumentation used for trace metals

measurements. This Method gives

requirements and suggestions for protecting

the laboratory.

4.3.1.3 Although contamination control is

essential, personnel health and safety remain

the highest priority. The Sampling Method

and Section 5 of this Method give suggestions

and requirements for personnel safety.

4.3.2 Avoiding contamination—The best

way to control contamination is to

completely avoid exposure of the sample to

contamination in the first place. Avoiding

exposure means performing operations in an

area known to be free from contamination.

Two of the most important factors in

avoiding/reducing sample contamination are

(1) an awareness of potential sources of

contamination and (2) strict attention to work

being done. Therefore, it is imperative that

the procedures described in this Method be

carried out by well-trained, experienced

personnel.

4.3.3 Use a clean environment—The ideal

environment for processing samples is a

class-100 clean room. If a clean room is not

available, all sample preparation should be

performed in a class-100 clean bench or a

nonmetal glove box fed by mercury- and

particle-free air or nitrogen. Digestions

should be performed in a nonmetal fume

hood situated, ideally, in the clean room.

4.3.4 Minimize exposure—The Apparatus

that will contact samples, blanks, or standard

solutions should be opened or exposed only

in a clean room, clean bench, or glove box

so that exposure to an uncontrolled

atmosphere is minimized. When not being

used, the Apparatus should be covered with

clean plastic wrap, stored in the clean bench

or in a plastic box or glove box, or bagged

in clean zip-type bags. Minimizing the time

between cleaning and use will also minimize

contamination.

4.3.5 Clean work surfaces’Before a given

batch of samples is processed, all work

surfaces in the hood, clean bench, or glove

box in which the samples will be processed

should be cleaned by wiping with a lint-free

cloth or wipe soaked with reagent water.

4.3.6 Wear gloves—Sampling personnel

must wear clean, nontalc gloves during all

operations involving handling of the

Apparatus, samples, and blanks. Only clean

gloves may touch the Apparatus. If another

object or substance is touched, the glove(s)

must be changed before again handling the

Apparatus. If it is even suspected that gloves

have become contaminated, work must be
28874 Federal Register / Vol. 63, No. 100 /Tuesday, May 26, 1998 / Proposed Rules

halted, the contaminated gloves removed,

and a new pair of clean gloves put on.

Wearing multiple layers of clean gloves will

allow the old pair to be quickly stripped with

minimal disruption to the work activity.

4.3.7 Use metal-free Apparatus—All

Apparatus used for determination of mercury

at ambient water quality criteria levels must

be nonmetallic, free of material that may

contain metals, or both.

4.3.7.1 Construction materials—Only

fluoropolymer or borosilicate glass (if Hg is

the only target analyte) containers should be

used for samples that will be analyzed for

mercury because mercury vapors can diffuse

in or out of other materials, resulting in

results that are biased low or high. All

materials, regardless of construction, that

will directly or indirectly contact the sample

must be cleaned using the procedures in this

Method and must be known to be clean and

mercury free before proceeding.

4.3.7.2 Serialization—It is recommended

that serial numbers be indelibly marked or

etched on each piece of Apparatus so that

contamination can be traced, and logbooks

should be maintained to track the sample

from the container through the labware to

introduction into the instrument. It may be

useful to dedicate separate sets of labware to

different sample types; e.g., receiving waters

vs. effluents. However, the Apparatus used

for processing blanks and standards must be

mixed with the Apparatus used to process

samples so that contamination of all labware

can be detected.

4.3.7.3 The laboratory or cleaning facility

is responsible for cleaning the Apparatus

used by the sampling team. If there are any

indications that the Apparatus is not clean

when received by the sampling team (e.g.,

ripped storage bags), an assessment of the

likelihood of contamination must be made.

Sampling must not proceed if it is possible

that the Apparatus is contaminated. If the

Apparatus is contaminated, it must be

returned to the laboratory or cleaning facility

for proper cleaning before any sampling

activity resumes.

4.3.8 Avoid sources of contamination—

Avoid contamination by being aware of

potential sources and routes of

contamination.

4.3.8.1 Contamination by carryover—

Contamination may occur when a sample

containing a low concentration of mercury is

processed immediately after a sample

containing a relatively high concentration of

mercury. When an unusually concentrated

sample is encountered, a bubbler blank

should be analyzed immediately following

the sample to check for carryover. Samples

known or suspected to contain the lowest

concentration of mercury should be analyzed

first followed by samples containing higher

levels.

4.3.8.2 Contamination by samples—

Significant laboratory or instrument

contamination may result when untreated

effluents, in-process waters, landfill

leachates, and other samples containing high

concentrations of mercury are processed and

analyzed. This Method is not intended for

application to these samples, and samples

containing high concentrations should not be

permitted into the clean room or laboratory

dedicated for processing trace metals

samples.

4.3.8.3 Contamination by indirect

contact—Apparatus that may not directly

come in contact with the samples may still

be a source of contamination. For example,

clean tubing placed in a dirty plastic bag may

pick up contamination from the bag and

subsequently transfer the contamination to

the sample. Therefore, it is imperative that

every piece of the Apparatus that is directly

or indirectly used in the collection,

processing, and analysis of ambient water

samples be thoroughly cleaned (see Section

6.1.2).

4.3.8.4 Contamination by airborne

particulate matter—Less obvious substances

capable of contaminating samples include

airborne particles. Samples may be

contaminated by airborne dust, dirt,

particles, or vapors from unfiltered air

supplies; nearby corroded or rusted pipes,

wires, or other fixtures; or metal-containing

paint. Whenever possible, sample processing

and analysis should occur as far as possible

from sources of airborne contamination.

4.4 Interferences.

4.4.1 Due to the BrCl oxidation step, there

are no observed interferences in the

determination of Hg by this Method.

4.4.2 The potential exists for destruction

of the gold traps if free halogens are purged

onto them, or if they are overheated (>500

°C). When the instructions in this Method are

followed accurately, neither of these

outcomes is likely.

4.4.3 Water vapor may collect in the gold

traps and subsequently condense in the

fluorescence cell upon desorption, giving a

false peak due to scattering of the excitation

radiation. Condensation can be avoided by

predrying the gold trap, and by discarding

those traps that tend to absorb large

quantities of water vapor.

4.4.4 The fluorescent intensity is strongly

dependent upon the presence of molecular

species in the carrier gas that can cause

‘‘quenching’’ of the excited atoms. The dual

amalgamation technique eliminates

quenching due to trace gases, but it remains

the analyst’s responsibility to ensure high

purity inert carrier gas and a leak-free

analytical train.

5.0 Safety

5.1 The toxicity or carcinogenicity of

each chemical used in this Method has not

been precisely determined; however, each

compound should be treated as a potential

health hazard. Exposure to these compounds

should be reduced to the lowest possible

level.

5.1.1 Chronic mercury exposure may

cause kidney damage, muscle tremors,

spasms, personality changes, depression,

irritability and nervousness. Organomercurials may cause permanent brain

damage. Because of the toxicological and

physical properties of Hg, pure standards

should be handled only by highly trained

personnel thoroughly familiar with handling

and cautionary procedures and the associated

risks.

5.1.2 It is recommended that the

laboratory purchase a dilute standard

solution of the Hg in this Method. If primary

solutions are prepared, they shall be

prepared in a hood, and a NIOSH/MESAapproved toxic gas respirator shall be worn

when high concentrations are handled.

5.2 This Method does not address all

safety issues associated with its use. The

laboratory is responsible for maintaining a

current awareness file of OSHA regulations

for the safe handling of the chemicals

specified in this Method. OSHA rules require

that a reference file of material safety data

sheets (MSDSs) must be made available to all

personnel involved in these analyses (29 CFR

1917.28, Appendix E). It is also suggested

that the laboratory perform personal hygiene

monitoring of each analyst who uses this

Method and that the results of this

monitoring be made available to the analyst.

Additional information on laboratory safety

can be found in References 10–13. The

references and bibliography at the end of

Reference 13 are particularly comprehensive

in dealing with the general subject of

laboratory safety.

5.3 Samples suspected to contain high

concentrations of Hg are handled using

essentially the same techniques employed in

handling radioactive or infectious materials.

Well-ventilated, controlled access

laboratories are required. Assistance in

evaluating the health hazards of particular

laboratory conditions may be obtained from

certain consulting laboratories and from State

Departments of Health or Labor, many of

which have an industrial health service. Each

laboratory must develop a strict safety

program for handling Hg.

5.3.1 Facility—When samples known or

suspected of containing high concentrations

of mercury are handled, all operations

(including removal of samples from sample

containers, weighing, transferring, and

mixing) should be performed in a glove box

demonstrated to be leaktight or in a fume

hood demonstrated to have adequate airflow.

Gross losses to the laboratory ventilation

system must not be allowed. Handling of the

dilute solutions normally used in analytical

and animal work presents no inhalation

hazards except in an accident.

5.3.2 Protective equipment—Disposable

plastic gloves, apron or lab coat, safety

glasses or mask, and a glove box or fume

hood adequate for radioactive work should

be used. During analytical operations that

may give rise to aerosols or dusts, personnel

should wear respirators equipped with

activated carbon filters.

5.3.3 Training—Workers must be trained

in the proper method of removing

contaminated gloves and clothing without

contacting the exterior surfaces.

5.3.4 Personal hygiene—Hands and

forearms should be washed thoroughly after

each manipulation and before breaks (coffee,

lunch, and shift).

5.3.5 Confinement—Isolated work areas

posted with signs, segregated glassware and

tools, and plastic absorbent paper on bench

tops will aid in confining contamination.

5.3.6 Effluent vapors—The effluent from

the CVAFS should pass through either a

column of activated charcoal or a trap

containing gold or sulfur to amalgamate or

react mercury vapors.

5.3.7 Waste handling—Good technique

includes minimizing contaminated waste.
Federal Register / Vol. 63, No. 100 /Tuesday, May 26, 1998 / Proposed Rules 28875

Plastic bag liners should be used in waste

cans. Janitors and other personnel must be

trained in the safe handling of waste.

5.3.8 Decontamination.

5.3.8.1 Decontamination of personnel—

Use any mild soap with plenty of scrubbing

action.

5.3.8.2 Glassware, tools, and surfaces—

Sulfur powder will react with mercury to

produce mercuric sulfide, thereby

eliminating the possible volatilization of Hg.

Satisfactory cleaning may be accomplished

by dusting a surface lightly with sulfur

powder, then washing with any detergent

and water.

5.3.9 Laundry—Clothing known to be

contaminated should be collected in plastic

bags. Persons who convey the bags and

launder the clothing should be advised of the

hazard and trained in proper handling. If the

launderer knows of the potential problem,

the clothing may be put into a washer

without contact. The washer should be run

through a cycle before being used again for

other clothing.

5.3.10 Wipe tests—A useful method of

determining cleanliness of work surfaces and

tools is to wipe the surface with a piece of

filter paper. Extraction and analysis by this

Method can achieve a limit of detection of

less than 1 ng per wipe. Less than 0.1 μg per

wipe indicates acceptable cleanliness;

anything higher warrants further cleaning.

More than 10 μg on a wipe constitutes an

acute hazard and requires prompt cleaning

before further use of the equipment or work

space, and indicates that unacceptable work

practices have been employed.

6.0 Apparatus and Materials

Disclaimer: The mention of trade names or

commercial products in this Method is for

illustrative purposes only and does not

constitute endorsement or recommendation

for use by the Environmental Protection

Agency. Equivalent performance may be

achievable using apparatus, materials, or

cleaning procedures other than those

suggested here. The laboratory is responsible

for demonstrating equivalent performance.

6.1 Sampling equipment.

6.1.1 Sample collection bottlesFluoropolymer or borosilicate glass, 125-to

1000-mL, with fluoropolymer or

fluoropolymer-lined cap.

6.1.2 Cleaning.

6.1.2.1 New bottles are cleaned by

heating to 65–75 °C in 4 N HCl for at least

48 h. The bottles are cooled, rinsed three

times with reagent water, and filled with

reagent water containing 1% HCl. These

bottles are capped and placed in a clean oven

at 60–70 °C overnight. After cooling, they are

rinsed three more times with reagent water,

filled with reagent water containing 0.4% (v/

v) HCl, and placed in a mercury-free class100 clean bench until dry. The bottles are

tightly capped (with a wrench), doublebagged in new polyethylene zip-type bags

until needed, and stored in wooden or plastic

boxes until use.

6.1.2.2 Used bottles known not to have

contained mercury at high levels are cleaned

as above, except for only 6–12 h in hot 4 N

HCl.

6.1.2.3 Bottle blanks should be analyzed

as described in Section 9.4.4.1 to verify the

effectiveness of the cleaning procedures.

6.1.3 Filtration Apparatus.

6.1.3.1 Filter—0.45-μm, 15-mm diameter

capsule filter (Gelman Supor 12175, or

equivalent).

6.1.3.2 Peristaltic pump—115-V a.c., 12-V

d.c., internal battery, variable-speed, singlehead (Cole-Parmer, portable, ‘‘Masterflex L/

S,’’ Catalog No. H–07570–10 drive with

Quick Load pump head, Catalog No. H–

07021–24, or equivalent).

6.1.3.3 Tubing—styrene/ethylene/

butylene/silicone (SEBS) resin for use with

peristaltic pump, approx 3⁄8-in ID by

approximately 3 ft (Cole-Parmer size 18,

Catalog No. G–06464–18, or approximately

1⁄4-in OD, Cole-Parmer size 17, Catalog No.

G–06464–17, or equivalent). Tubing is

cleaned by soaking in 5–10% HCl solution

for 8–24 h, rinsing with reagent water in a

clean bench in a clean room, and drying in

the clean bench by purging with metal-free

air or nitrogen. After drying, the tubing is

double-bagged in clear polyethylene bags,

serialized with a unique number, and stored

until use.

6.2 Equipment for bottle and glassware

cleaning.

6.2.1 Vat, 100–200 L, high-density

polyethylene (HDPE), half filled with 4 N

HCl in reagent water.

6.2.2 Panel immersion heater, 500–W, allfluoropolymer coated, 120 vac (Cole-Parmer

H–03053–04, or equivalent).

Warning: Read instructions carefully!! The

heater will maintain steady state, without

temperature feedback control, of 60–75 °C in

a vat of the size described. However, the

equilibrium temperature will be higher (up to

boiling) in a smaller vat. Also, the heater

plate MUST be maintained in a vertical

position, completely submerged and away

from the vat walls to avoid melting the vat

or burning out!

6.2.3 Laboratory sink—in class-100 clean

area, with high-flow reagent water (Section

7.1) for rinsing.

6.2.4 Clean bench—class-100, for drying

rinsed bottles.

6.2.5 Oven—stainless steel, in class-100

clean area, capable of maintaining ± 5°C in

the 60–70°C temperature range.

6.3 Cold vapor atomic fluorescence

spectrometer (CVAFS): The CVAFS system

used may either be purchased from a

supplier, or built in the laboratory from

commercially available components.

6.3.1 Commercially available CVAFS—

Tekran (Toronto, ON) Model 2500 CVAFS, or

Brooks-Rand (Seattle, WA) Model III CVAFS,

or equivalent.

6.3.2 Custom-built CVAFS (Reference 14).

Figure 2 shows the schematic diagram. The

system consists of the following:

6.3.2.1 Low-pressure 4–W mercury vapor

lamp.

6.3.2.2 Far UV quartz flow-through

fluorescence cell—12 mm × 12 mm × 45 mm,

with a 10-mm path length (NSG Cells, or

equivalent).

6.3.2.3 UV-visible photomultiplier

(PMT)—sensitive to <230 nm. This PMT is

isolated from outside light with a 253.7-nm

interference filter (Oriel Corp., Stamford, CT,

or equivalent).

6.3.2.4 Photometer and PMT power

supply (Oriel Corp. or equivalent), to convert

PMT output (nanoamp) to millivolts.

6.3.2.5 Black anodized aluminum optical

block—holds fluorescence cell, PMT, and

light source at perpendicular angles, and

provides collimation of incident and

fluorescent beams (Frontier Geosciences Inc.,

Seattle, WA, or equivalent).

6.3.2.6 Flowmeter—with needle valve

capable of reproducibly keeping the carrier

gas flow rate at 30 mL/min.

6.4 Hg purging system—Figure 2 shows

the schematic diagram for the purging

system. The system consists of the following:

6.4.1 Flow meter/needle valve—capable

of controlling and measuring gas flow rate to

the purge vessel at 350 ± 50 mL/min.

6.4.2 Fluoropolymer fittings—

connections between components and

columns are made using 6.4-mm OD

fluoropolymer tubing and fluoropolymer

friction-fit or threaded tubing connectors.

Connections between components requiring

mobility are made with 3.2-mm OD

fluoropolymer tubing because of its greater

flexibility.

6.4.3 Acid fume pretrap—10-cm long ×

0.9-cm ID fluoropolymer tube containing 2–

3 g of reagent grade, nonindicating, 8–14

mesh soda lime chunks, packed between

wads of silanized glass wool. This trap is

cleaned of Hg by placing on the output of a

clean cold vapor generator (bubbler) and

purging for 1 h with N2 at 350 mL/min.

6.4.4 Cold vapor generator (bubbler)—

200-mL borosilicate glass (15 cm high × 5.0

cm diameter) with standard taper 24/40 neck,

fitted with a sparging stopper having a coarse

glass frit that extends to within 0.2 cm of the

bubbler bottom (Frontier Geosciences, Inc. or

equivalent).

6.5 The dual-trap Hg(0) preconcentrating

system.

6.5.1 Figure 2 shows the dual-trap

amalgamation system (Reference 5).

6.5.2 Gold-coated sand traps—10-cm long

× 6.5-mm OD × 4-mm ID quartz tubing. The

tube is filled with 3.4 cm of gold-coated 45/

60 mesh quartz sand (Frontier Geosciences

Inc., Seattle, WA, or equivalent). The ends

are plugged with quartz wool.

6.5.2.1 Traps are fitted with 6.5-mm ID

fluoropolymer friction-fit sleeves for making

connection to the system. When traps are not

in use, fluoropolymer end plugs are inserted

in trap ends to eliminate contamination.

6.5.2.2 At least six traps are needed for

efficient operation, one as the ‘‘analytical’’

trap, and the others to sequentially collect

samples.

6.5.3 Heating of gold-coated sand traps—

To desorb Hg collected on a trap, heat for 3.0

min to 450–500 °C (a barely visible red glow

when the room is darkened) with a coil

consisting of 75 cm of 24-gauge Nichrome

wire at a potential of 10–14 vac. Potential is

applied and finely adjusted with an

autotransformer.

6.5.4 Timers—The heating interval is

controlled by a timer-activated 120-V outlet

(Gralab, or equivalent), into which the

heating coil autotransformer is plugged. Two

timers are required, one each for the

‘‘sample’’ trap and the ‘‘analytical’’ trap.

6.5.5 Air blowers—After heating, traps

are cooled by blowing air from a small
28876 Federal Register / Vol. 63, No. 100 /Tuesday, May 26, 1998 / Proposed Rules

squirrel-cage blower positioned immediately

above the trap. Two blowers are required,

one each for the ‘‘sample’’ trap and the

‘‘analytical’’ trap.

6.6 Recorder—Any multi-range millivolt

chart recorder or integrator with a range

compatible with the CVAFS is acceptable. By

using a two pen recorder with pen sensitivity

offset by a factor of 10, the dynamic range of

the system is extended to 103.

6.7 Pipettors—All-plastic pneumatic

fixed-volume and variable pipettors in the

range of 10 μL to 5.0 mL.

6.8 Analytical balance capable of

weighing to the nearest 0.01 g.

7.0 Reagents and Standards

7.1 Reagent water—18-MΩ minimum,

ultrapure deionized water starting from a

prepurified (distilled, reverse osmosis, etc.)

source. Water should be monitored for Hg,

especially after ion exchange beds are

changed.

7.2 Air—It is very important that the

laboratory air be low in both particulate and

gaseous mercury. Ideally, mercury work

should be conducted in a new laboratory

with mercury-free paint on the walls. Outside

air, which is very low in Hg, should be

brought directly into the class-100 clean

bench air intake. If this is not possible, air

coming into the clean bench can be cleaned

for mercury by placing a gold-coated cloth

prefilter over the intake.

7.2.1 Gold-coated cloth filter: Soak 2 m2

of cotton gauze in 500 mL of 2% gold

chloride solution at pH 7. In a hood, add 100

mL of 30% NH2OH•HCl solution, and

homogenize into the cloth with gloved

hands. The material will turn black as

colloidal gold is precipitated. Allow the

mixture to set for several hours, then rinse

with copious amounts of deionized water.

Squeeze-dry the rinsed cloth, and spread flat

on newspapers to air-dry. When dry, fold and

place over the intake prefilter of the laminar

flow hood.

Caution: Great care should be taken to

avoid contaminating the laboratory with gold

dust. This could cause interferences with the

analysis if gold becomes incorporated into

the samples or equipment. The gilding

procedure should be done in a remote

laboratory if at all possible.

7.3 Hydrochloric acid—trace-metal

purified reagent-grade HCl containing less

than 5 pg/mL Hg. The HCl should be

preanalyzed for Hg before use.

7.4 Hydroxylamine hydrochloride—

Dissolve 300 g of NH2OH•HCl in reagent

water and bring to 1.0 L. This solution may

be purified by the addition of 1.0 mL of SnCl2

solution and purging overnight at 500 mL/

min with Hg-free N2.

7.5 Stannous chloride—Bring 200 g of

SnCl2•2H2O and 100 mL concentrated HCl to

1.0 L with reagent water. Purge overnight

with mercury-free N2 at 500 mL/min to

remove all traces of Hg. Store tightly capped.

7.6 Bromine monochloride (BrCl)—In a

fume hood, dissolve 27 g of reagent grade

KBr in 2.5 L of low-Hg HCl. Place a clean

magnetic stir bar in the bottle and stir for

approximately 1 h in the fume hood. Slowly

add 38 g reagent grade KBrO3 to the acid

while stirring. When all of the KBrO3 has

been added, the solution color should change

from yellow to red to orange. Loosely cap the

bottle, and allow to stir another hour before

tightening the lid.

Warning: This process generates copious

quantities of free halogens (Cl2, Br2, BrCl),

which are released from the bottle. Add the

KBrO3 slowly in a fume hood!

7.7 Stock mercury standard—NISTcertified 10,000-ppm aqueous Hg solution

(NIST–3133). This solution is stable at least

until the NIST expiration date.

7.8 Secondary Hg standard—Add approx

0.5 L of reagent water and 5 mL of BrCl

solution (Section 7.6) to a 1.00-L class A

volumetric flask. Add 0.100 mL of the stock

mercury standard (Section 7.7) to the flask

and dilute to 1.00 L with reagent water. This

solution contains 1.00 ‘‘μg/mL (1.00 ppm)

Hg. Transfer the solution to a fluoropolymer

bottle and cap tightly. This solution is

considered stable until the NIST expiration

date.

7.9 Working Hg standard—Dilute 1.00 mL

of the secondary Hg standard (Section 7.8) to

100 mL in a class A volumetric flask with

reagent water containing 0.5% by volume

BrCl solution (Section 7.6). This solution

contains 10.0 ng/mL and should be replaced

monthly.

7.10 IPR and OPR solutions—Using the

working Hg standard (Section 7.9), prepare

IPR and OPR solutions at a concentration of

5 ng/L Hg in reagent water.

7.11 Nitrogen—Grade 4.5 (standard

laboratory grade) nitrogen that has been

further purified by the removal of Hg using

a gold-coated sand trap.

7.12 Argon—Grade 5.0 (ultra high-purity,

GC grade) that has been further purified by

the removal of Hg using a gold-coated sand

trap.

8.0 Sample Collection, Preservation, and

Storage

8.1 Before samples are collected,

consideration should be given to the type of

data required, (i.e., dissolved or total), so that

appropriate preservation and pretreatment

steps can be taken. The pH of all aqueous

samples must be tested immediately before

aliquotting for processing or direct analysis

to ensure the sample has been properly

preserved.

8.2 Samples are collected into rigorously

cleaned fluoropolymer bottles with

fluoropolymer or fluoropolymer-lined caps.

Borosilicate glass bottles may be used if Hg

is the only target analyte. It is critical that the

bottles have tightly sealing caps to avoid

diffusion of atmospheric Hg through the

threads (Reference 4). Polyethylene sample

bottles must not be used (Reference 14).

8.3 Collect samples using guidance

provided in the Sampling Method (Reference

9). Procedures in the Sampling Method are

based on rigorous protocols for collection of

samples for mercury (References 4 and 14).

Note: Discrete samplers have been found to

contaminate samples with Hg at the ng/L

level. Therefore, great care should be

exercised if this type of sampler is used to

collect samples. It may be necessary for the

sampling team to use other means of sample

collection if samples are found to be

contaminated using the discrete sampler.

8.4 Sample filtration—For dissolved Hg,

samples and field blanks are filtered through

a 0.45 μm capsule filter (Section 6.1.3.1). The

Sampling Method gives the filtering

procedures.

8.5 Preservation—Samples are preserved

by adding either 5mL/L of pretested 12N HCl

or 5 mL/L BrCl solution. If a sample will also

be used for the determination of methyl

mercury, it should be preserved with 5 mL/

L HCl solution only. Acid- and BrClpreserved samples are stable for a minimum

of 6 months.

8.5.1 Samples may be shipped to the

laboratory unpreserved if they are (1)

collected in fluoropolymer bottles, (2) filled

to the top with no head space, (3) capped

tightly, and (4) maintained at 0–4°C from the

time of collection until preservation. The

samples must be acid-preserved within 48 h

after sampling.

8.5.2 Samples that are acid-preserved

may lose Hg to coagulated organic materials

in the water or condensed on the walls

(Reference 15). The best approach is to add

BrCl directly to the sample bottle at least 24

hours before analysis. If other Hg species are

to be analyzed, these aliquot must be

removed prior to the addition of BrCl. If BrCl

cannot be added directly to the sample bottle,

the bottle must be shaken vigorously prior to

sub-sampling.

8.5.3 Handling of the samples in the

laboratory should be undertaken in a

mercury-free clean bench, after rinsing the

outside of the bottles with reagent water and

drying in the clean air hood.

Note: Due to the potential for

contamination, it is recommended that

filtration and preservation of samples be

performed in the clean room in the

laboratory. However, if circumstances in the

field prevent overnight shipment of samples,

samples should be filtered and preserved in

a designated clean area in the field in

accordance with the procedures given in

Sampling Method 1669 (Reference 9).

8.6 Storage—Sample bottles should be

stored in clean (new) polyethylene bags until

sample analysis. Refrigeration at 0—4°C is

not necessary once samples are preserved. If

properly preserved, samples can be held up

to 6 months before analysis.

9.0 Quality Control

9.1 Each laboratory that uses this Method

is required to operate a formal quality

assurance program (Reference 16). The

minimum requirements of this program

consist of an initial demonstration of

laboratory capability, ongoing analysis of

standards and blanks as a test of continued

performance, and the analysis of matrix

spikes (MS) and matrix spike duplicates

(M.SD) to assess accuracy and precision.

Laboratory performance is compared to

established performance criteria to determine

that the results of analyses meet the

performance characteristics of the Method.

9.1.1 The analyst shall make an initial

demonstration of the ability to generate

acceptable accuracy and precision with this

Method. This ability is established as

described in Section 9.2.

9.1.2 In recognition of advances that are

occurring in analytical technology, the
Federal Register / Vol. 63, No. 100 /Tuesday, May 26, 1998 / Proposed Rules 28877

analyst is permitted certain options to

improve results or lower the cost of

measurements. These options include

automation of the dual-amalgamation system,

single-trap amalgamation (Reference 17),

direct electronic data acquisition, calibration

using gas-phase elemental Hg standards,

changes in the bubbler design (including

substitution of a flow-injection system), or

changes in the detector (i.e., CVAAS) when

less sensitivity is acceptable or desired.

Changes in the principle of the determinative

technique, such as the use of colorimetry, are

not allowed. If an analytical technique other

than the CVAFS technique specified in this

Method is used, that technique must have a

specificity for mercury equal to or better than

the specificity of the technique in this

Method.

9.1.2.1 Each time this Method is

modified, the analyst is required to repeat the

procedure in Section 9.2. If the change will

affect the detection limit of the Method, the

laboratory is required to demonstrate that the

MDL (40 CFR Part 136, Appendix B) is lower

than one-third the regulatory compliance

level or lower than the MDL of this Method,

whichever is higher. If the change will affect

calibration, the analyst must recalibrate the

instrument according to Section 10.

9.1.2.2 The laboratory is required to

maintain records of modifications made to

this Method. These records include the

following, at a minimum:

9.1.2.2.1 The names, titles, addresses, and

telephone numbers of the analyst(s) who

performed the analyses and modification,

and the quality control officer who witnessed

and will verify the analyses and

modification.

9.1.2.2.2 A narrative stating the reason(s)

for the modification(s).

9.1.2.2.3 Results from all quality control

(QC) tests comparing the modified method to

this Method, including the following:

(a) Calibration (Section 10).

(b) Initial precision and recovery (Section

9.2).

(c) Analysis of blanks (Section 9.4).

(d) Matrix spike/matrix spike duplicate

analysis (Section 9.3).

(e) Ongoing precision and recovery

(Section 9.5).

(f) Quality control sample (Section 9.6).

(g) Method detection limit (Section 9.2.1).

9.1.2.2.4 Data that will allow an

independent reviewer to validate each

determination by tracking the instrument

output to the final result. These data are to

include the following:

(a) Sample numbers and other identifiers.

(b) Processing dates.

(c) Analysis dates.

(d) Analysis sequence/run chronology.

(e) Sample weight or volume.

(f) Copies of logbooks, chart recorder, or

other raw data output.

(g) Calculations linking raw data to the

results reported.

9.1.3 Analyses of MS and MSD samples

are required to demonstrate the accuracy and

precision and to monitor matrix

interferences. Section 9.3 describes the

procedure and QC criteria for spiking.

9.1.4 Analyses of blanks are required to

demonstrate acceptable levels of

contamination. Section 9.4 describes the

procedures and criteria for analyzing blanks.

9.1.5 The laboratory shall, on an ongoing

basis, demonstrate through analysis of the

ongoing precision and recovery (OPR) sample

and the quality control sample (QCS) that the

system is in control. Sections 9.5 and 9.6

describe these procedures, respectively.

9.1.6 The laboratory shall maintain

records to define the quality of the data that

are generated. Sections 9.3.7 and 9.5.3

describe the development of accuracy

statements.

9.1.7 The determination of Hg in water is

controlled by an analytical batch. An

analytical batch is a set of samples oxidized

with the same batch of reagents, and

analyzed during the same 12-hour shift. A

batch may be from 1 to as many as 20

samples. Each batch must be accompanied by

at least three bubbler blanks (Section 9.4), an

OPR sample, and a QCS. In addition, there

must be one MS and one MSD sample for

every 10 samples (a frequency of 10%).

9.2 Initial demonstration of laboratory

capability.

9.2.1 Method detection limit—To

establish the ability to detect Hg, the analyst

shall determine the MDL determined

according to the procedure at 40 CFR 136,

Appendix B using the apparatus, reagents,

and standards that will be used in the

practice of this Method. The laboratory must

produce an MDL that is less than or equal to

the MDL listed in Section 1.5 or one-third the

regulatory compliance limit, whichever is

greater. The MDL should be determined

when a new operator begins work or

whenever, in the judgment of the laboratory,

a change in instrument hardware or operating

conditions would dictate that the MDL be

redetermined.

9.2.2 Initial precision and recovery

(IPR)’To establish the ability to generate

acceptable precision and recovery, the

analyst shall perform the following

operations:

9.2.2.1 Analyze four replicates of the IPR

solution (5 ng/L, Section 7.10) according to

the procedure beginning in Section 11.

9.2.2.2 Using the results of the set of four

analyses, compute the average percent

recovery (X), and the standard deviation of

the percent recovery (s) for Hg.

9.2.2.3 Compare s and X with the

corresponding limits for initial precision and

recovery in Table 2. If s and X meet the

acceptance criteria, system performance is

acceptable and analysis of samples may

begin. If, however, s exceeds the precision

limit or X falls outside the acceptance range,

system performance is unacceptable. Correct

the problem and repeat the test (Section

9.2.2.1).

9.3 Matrix spike (MS) and matrix spike

duplicate (MSD)—To assess the performance

of the Method on a given sample matrix, the

laboratory must spike, in duplicate, a

minimum of 10% (1 sample in 10) from a

given sampling site or, if for compliance

monitoring, from a given discharge.

Therefore, an analytical batch of 20 samples

would require two pairs of MS/MSD samples

(four spiked samples total).

9.3.1 The concentration of the spike in

the sample shall be determined as follows:

9.3.1.1 If, as in compliance monitoring,

the concentration of Hg in the sample is

being checked against a regulatory

compliance limit, the spiking level shall be

at that limit or at 1–5 times the background

concentration of the sample (as determined

in Section 9.3.2), whichever is greater.

9.3.1.2 If the concentration of Hg in a

sample is not being checked against a limit,

the spike shall be at 1–5 times the

background concentration or at 1–5 times the

ML in Table 2, whichever is greater.

9.3.2 To determine the background

concentration (B), analyze one sample aliquot

from each set of 10 samples from each site

or discharge according to the procedure in

Section 11. If the expected background

concentration is known from previous

experience or other knowledge, the spiking

level may be established a priori.

9.3.2.1 If necessary, prepare a standard

solution to produce an appropriate level in

the sample (Section 9.3.1).

9.3.2.2 Spike two additional sample

aliquots with the spiking solution and

analyze these aliquots as described in Section

11.1.2 to determine the concentration after

spiking (A).

9.3.3 Calculate the percent recovery (R) in

each aliquot using the following equation:

%R

A B

T = ( ) − 100

Where:

A = Measured concentration of analyte after

spiking

B = Measured concentration of analyte before

spiking

T = True concentration of the spiking

9.3.4 Compare percent recovery (R) with

the QC acceptance criteria in Table 2.

9.3.4.1 If results of the MS/MSD are

similar and fail the acceptance criteria, and

recovery for the OPR standard (Section 9.5)

for the analytical batch is within the

acceptance criteria in Table 2, an interference

is present and the results may not be reported

for regulatory compliance purposes. If the

interference can be attributed to sampling,

the site or discharge should be resampled. If

the interference can be attributed to a method

deficiency, the analyst must modify the

method, repeat the test required in Section

9.1.2, and repeat analysis of the sample and

MS/MSD. However, when Method 1631 was

written, there were no known interferences

in the determination of Hg using this

Method. If such a result is observed, the

laboratory should investigate it thoroughly.

9.3.4.2 If the results of both the spike and

the OPR test fall outside the acceptance

criteria, the analytical system is judged to be

not in control. The laboratory must identify

and correct the problem and reanalyze the

sample batch.

9.3.5 Relative percent difference between

duplicates’Compute the relative percent

difference (RPD) between the MS and MSD

results according to the following equation

using the concentrations found in the MS

and MSD. Do not use the recoveries

calculated in Section 9.3.3 for this

calculation because the RPD is inflated when

the background concentration is near the

spike concentration.
28878 Federal Register / Vol. 63, No. 100 /Tuesday, May 26, 1998 / Proposed Rules

RPD

D D

D D

= × ( ) −

+

200

1 2

( ) 1 2

Where:

D1 = concentration of Hg in the MS sample

D2 = concentration of Hg in the MSD sample

9.3.6 The RPD for the MS/MSD pair must

not exceed the acceptance criterion in Table

2. If the criterion is not met, the system is

judged to be out of control. The problem

must be identified and corrected

immediately, and the analytical batch

reanalyzed.

9.3.7 As part of the QC program for the

laboratory, method precision and accuracy

for samples should be assessed and records

maintained. After analyzing five samples in

which the recovery passes the test in Section

9.3.4, compute the average percent recovery

(Ra) and the standard deviation of the percent

recovery (sr). Express the accuracy

assessment as a percent recovery interval

from Ra ¥ 2sr to Ra + 2sr. For example, if Ra

= 90% and sr = 10% for five analyses, the

accuracy interval is expressed as 70—110%.

Update the accuracy assessment regularly

(e.g., after every five to ten new accuracy

measurements).

9.4 Blanks—Blanks are critical to the

reliable determination of Hg at low levels.

The sections below give the minimum

requirements for analysis of blanks. However,

it is suggested that additional blanks be

analyzed as necessary to pinpoint sources of

contamination in, and external to, the

laboratory.

9.4.1 Bubbler blanks—Bubbler blanks are

analyzed to demonstrate freedom from

system contamination. At least three bubbler

blanks must be run per analytical batch. One

bubbler blank must be analyzed following

each OPR. The mean bubbler blank for an

analytical batch, if within acceptance criteria,

is subtracted from all raw data for that batch

prior to the calculation of results.

9.4.1.1 Immediately after analyzing a

sample for Hg, place a clean gold trap on the

bubbler, purge and analyze the sample a

second time using the procedure in Section

11, and determine the amount of Hg

remaining in the system.

9.4.1.2 If the bubbler blank is found to

contain more than 50 pg Hg, the system is out

of control. The problem must be investigated

and remedied, and the samples run on that

bubbler must be reanalyzed. If the blanks

from other bubblers contain less than 50 pg

Hg, the data associated with those bubblers

remain valid.

9.4.1.3 The mean result for all bubbler

blanks (from bubblers passing the

specification in Section 9.4.1.2) in an

analytical batch (at least three bubbler

blanks) is calculated at the end of the batch.

The mean result must be <25 pg with a

standard deviation of <10 pg for the batch to

be considered valid. If the mean is <25 pg,

the average peak measurement value is

subtracted from all raw data before results are

calculated.

9.4.1.4 If Hg in the bubbler blank exceeds

the acceptance criteria in Section 9.4.1.3, the

system is out of control, and the problem

must be resolved and the samples

reanalyzed. Usually, the bubbler blank is too

high for one of the following reasons:

(a) Bubblers need rigorous cleaning;

(b) Soda-lime is contaminated; or

(c) Carrier gas is contaminated.

9.4.2 Reagent blanks—The Hg

concentration in reagent blanks must be

determined on solutions of reagents by

adding these reagents to previously purged

reagent water in the bubbler.

9.4.2.1 Reagent blanks are required when

the batch of reagents (bromine monochloride

plus hydroxylamine hydrochloride) are

prepared, with verification in triplicate each

month until a new batch of reagents is

needed.

9.4.2.2 Add aliquots of BrCl (0.5 mL),

NH2OH (0.2 mL) and SnCl2 (0.5 mL) to

previously purged reagent water in the

bubbler.

9.4.2.3 The presence of more than 25 pg

of Hg indicates a problem with the reagent

solution. The purging of certain reagent

solutions, such as SnCl2 or NH2OH with

mercury-free nitrogen or argon can reduce Hg

to acceptable levels. Because BrCl cannot be

purified, a new batch should be made from

different reagents and should be tested for Hg

levels if the level of Hg in the BrCl solution

is too high.

9.4.3 Field blanks.

9.4.3.1 Analyze the field blank(s) shipped

with each set of samples (samples collected

from the same site at the same time, to a

maximum of 10 samples). Analyze the blank

immediately before analyzing the samples in

the batch.

9.4.3.2 If Hg or any potentially interfering

substance is found in the field blank at a

concentration equal to or greater than the ML

(Table 2), or greater than one-fifth the level

in the associated sample, whichever is

greater, results for associated samples may be

the result of contamination and may not be

reported for regulatory compliance purposes.

9.4.3.3 Alternatively, if a sufficient

number of field blanks (three minimum) are

analyzed to characterize the nature of the

field blank, the average concentration plus

two standard deviations must be less than the

regulatory compliance limit or less than onehalf the level in the associated sample,

whichever is greater.

9.4.3.4 If contamination of the field

blanks and associated samples is known or

suspected, the laboratory should

communicate this to the sampling team so

that the source of contamination can be

identified and corrective measures taken

before the next sampling event.

9.4.4 Equipment blanks—Before any

sampling equipment is used at a given site,

the laboratory or cleaning facility is required

to generate equipment blanks to demonstrate

that the sampling equipment is free from

contamination. Two types of equipment

blanks are required: bottle blanks and

sampler check blanks.

9.4.4.1 Bottle blanks—After undergoing

the cleaning procedures in this Method,

bottles should be subjected to conditions of

use to verify the effectiveness of the cleaning

procedures. A representative set of sample

bottles should be filled with reagent water

acidified to pH <2 and allowed to stand for

a minimum of 24 h. Ideally, the time that the

bottles are allowed to stand should be as

close as possible to the actual time that the

sample will be in contact with the bottle.

After standing, the water should be analyzed

for any signs of contamination. If a bottle

shows contamination at or above the level

specified for the field blank (Section 9.4.3),

the problem must be identified, the cleaning

procedures corrected or cleaning solutions

changed, and all affected bottles recleaned.

9.4.4.2 Sampler check blanks—Sampler

check blanks are generated in the laboratory

or at the equipment cleaning facility by

processing reagent water through the

sampling devices using the same procedures

that are used in the field (see Sampling

Method). Therefore, the ‘‘clean hands/dirty

hands’’ technique used during field sampling

should be followed when preparing sampler

check blanks at the laboratory or cleaning

facility.

9.4.4.2.1 Sampler check blanks are

generated by filling a large carboy or other

container with reagent water (Section 7.1)

and processing the reagent water through the

equipment using the same procedures that

are used in the field (see Sampling Method,

Reference 9). For example, manual grab

sampler check blanks are collected by

directly submerging a sample bottle into the

water, filling the bottle, and capping.

Subsurface sampler check blanks are

collected by immersing a submersible pump

or intake tubing into the water and pumping

water into a sample container.

9.4.4.2.2 The sampler check blank must

be analyzed using the procedures in this

Method. If mercury or any potentially

interfering substance is detected in the blank

at or above the level specified for the field

blank (Section 9.4.3), the source of

contamination or interference must be

identified, and the problem corrected. The

equipment must be demonstrated to be free

from mercury and interferences before the

equipment may be used in the field.

9.4.4.2.3 Sampler check blanks must be

run on all equipment that will be used in the

field. If, for example, samples are to be

collected using both a grab sampling device

and a subsurface sampling device, a sampler

check blank must be run on both pieces of

equipment.

9.5 Ongoing precision and recovery

(OPR)—To demonstrate that the analytical

system is within the performance criteria of

this Method and that acceptable precision

and accuracy is being maintained within

each analytical batch, the analyst shall

perform the following operations:

9.5.1 Analyze the OPR solution (5 ng/L,

Section 7.10) followed by a bubbler blank

prior to the analysis of each analytical batch

according to the procedure beginning in

Section 11. An OPR also must be analyzed

at the end of an analytical run or at the end

of each 12-hour shift. Subtract the peak

height (or peak area) of the bubbler blank

from the peak height (or area) of the OPR and

calculate the concentration for the blanksubtracted OPR.

9.5.2 Compare the concentration recovery

with the limits for ongoing precision and

recovery in Table 2. If the recovery is in the

range specified, the analytical system is

control and analysis of samples and blanks

may proceed. If, however, the concentration

is not in the specified range, the analytical
Federal Register / Vol. 63, No. 100 /Tuesday, May 26, 1998 / Proposed Rules 28879

process is not in control. Correct the problem

and repeat the ongoing precision and

recovery test. All reported results must be

associated with an OPR that meets the Table

2 performance criteria at the beginning and

end of each batch.

9.5.3 The laboratory should add results

that pass the specification in Section 9.5.2 to

IPR and previous OPR data and update QC

charts to form a graphic representation of

continued laboratory performance. The

laboratory should also develop a statement of

laboratory data quality by calculating the

average percent recovery (Ra) and the

standard deviation of the percent recovery

(sr). Express the accuracy as a recovery

interval from Ra—2sr to Ra + 2sr. For example,

if Ra = 95% and sr = 5%, the accuracy is 85–

105%.

9.6 Quality control sample (QCS)—The

laboratory must obtain a QCS from a source

different from the Hg used to produce the

standards used routinely in this Method

(Sections 7.7–7.10). The QCS should be

analyzed as an independent check of system

performance

9.7 Depending on specific program

requirements, the laboratory may be required

to analyze field duplicates and field spikes

collected to assess the precision and accuracy

of the sampling, sample transportation, and

storage techniques. The relative percent

difference (RPD) between field duplicates

should be less than 20%. If the RPD of the

field duplicates exceeds 20%, the laboratory

should communicate this to the sampling

team so that the source of error can be

identified and corrective measures taken

before the next sampling event.

10.0 Calibration and Standardization

10.1 Establish the operating conditions

necessary to purge Hg from the bubbler and

to desorb Hg from the traps in a sharp peak.

Further details for operation of the purge and

trap and desorption and analysis systems is

given in Sections 11.3 and 11.4, respectively.

The entire system is calibrated using

standards traceable to NIST standard

reference material, as follows:

10.1.1 Calibration.

10.1.1.1 The calibration must contain five

or more non-zero points and the results of

analysis of two bubbler blanks. The lowest

calibration point must be at the Minimum

Level (ML).

10.1.1.2 Standards are analyzed by the

addition of aliquots of the Hg working

standard (Section 7.9) directly into the

bubblers. Add a 50 μL aliquot of the working

standard and 0.5 mL SnCl2 to the bubbler.

Swirl to produce a standard of 0.5 ng/L.

Purge under the optimum operating

conditions (Section 10.1). Sequentially

follow with aliquots of 0.1, 0.5, 2.5, and 10

mL of the working standard plus 0.5 mL

SnCl2 to produce standards of 1, 5, 25, and

100 ng/L.

10.1.1.3 For each point, subtract the mean

peak height or area of the bubbler blanks for

the analytical batch from the peak height or

area for the standard. Calculate the

calibration factor (CFx) for Hg in each of the

five standards using the mean bubbler-blanksubtracted peak height or area and the

following equation:

CF

A A

C X

X BB

X

= ( ) − ( )

( )

Where:

AX=peak height or area for Hg in standard

ABBpeak height or area for Hg in bubbler

blank)

CX=concentration of standard analyzed (ng/

L)

10.1.1.4 Calculate the mean calibration

factor (CFm), the standard deviation of the

calibration factor (SD), and the relative

standard deviation (RSD) of the calibration

factor, where RSD = 100 x SD/CFm.

10.1.1.5 If RSD ≤ 15%, calculate the

recovery for the lowest standard (0.5 ng/L)

using CFm. If the RSD ≤ 15% and the

recovery of the lowest standard is in the

range of 75–125%, the calibration is

acceptable and CFm may be used to calculate

the concentration of Hg in samples. If RSD

> 15% or if the recovery of the lowest

standard is not in the range of 75–125%,

recalibrate the analytical system and repeat

the test.

10.2 Ongoing precision and recovery—

Perform the ongoing precision and recovery

test (Section 9.5) to verify calibration prior to

and after analysis of samples in each

analytical batch.

11.0 Procedure

Note: The following procedures for

analysis of samples are provided as

guidelines. Laboratories may find it

necessary to optimize the procedures, such as

drying time or potential applied to the

Nichrome wires, for the laboratory’s specific

instrumental set-up.

11.1 Sample Preparation.

11.1.1 Pour a 100-mL aliquot from a

thoroughly shaken, acidified sample, into a

125-mL fluoropolymer bottle. If BrCl was not

added as a preservative (Section 8.5), add the

amount of BrCl solution (Section 7.6) given

below, cap the bottle, and digest at room

temperature for a 12 h minimum.

11.1.1.1 For clear water and filtered

samples, add 0.5 mL of BrCl; for brown water

and turbid samples, add 1.0 mL of BrCl. If

the yellow color disappears because of

consumption by organic matter or sulfides,

more BrCl should be added until a

permanent (12-h) yellow color is obtained.

11.1.1.2 Some highly organic matrices,

such as sewage effluent, will require high

levels of BrCl (i.e., 5 mL/100 mL of sample),

and longer oxidation times, or elevated

temperatures (i.e.; place sealed bottles in

oven at 50°C for 6 h). The oxidation always

must be continued until a permanent yellow

color remains.

11.1.2 Matrix spikes and matrix spike

duplicates—For every 10 or fewer samples,

pour two additional 100-mL aliquots from a

randomly selected sample, spike at the level

specified in Section 9.3, and process in the

same manner as the samples. There should

be 2 MS/MSD pairs for each analytical batch

of 20 samples.

11.2 Hg reduction and purging—Place

100 mL of reagent water in each bubbler, add

1.0 mL of SnCl2, and purge with Hg-free N2

for 20 min at 300-400 mL/min (Figure 1).

11.2.1 Connect a gold sand trap to the

output of the soda lime pretrap, and purge

the water another 20 min to obtain a bubbler

blank.

11.2.2 Add 0.2 mL of 30% N H2OH to the

BrCl-oxidized sample in the 125-mL

fluoropolymer bottle. Cap the bottle and

swirl the sample. The yellow color will

disappear, indicating the destruction of the

BrCl. Allow the sample to react for 5 min

with periodic swirling to be sure that no

traces of halogens remain.

Note: Purging of free halogens onto the

gold trap will result in damage to the trap

and low or irreproducible results.

11.2.3 After discarding the water from the

standards, connect a fresh trap to the bubbler,

pour the reduced sample into the bubbler,

add 0.5 mL of 20% SnCl2 solution, and purge

the sample onto a gold sand trap with N2 for

20 min.

11.2.4 When analyzing Hg samples, the

recovery is quantitative, and organic

interferents are destroyed. Thus, standards,

bubbler blanks, and small amounts of highlevel samples may be run directly in the

water of previously purged samples. After

very high samples, a small degree of

carryover (<0.01%) may occur. Bubblers that

contain such samples should be blanked

prior to proceeding with low level samples.

11.3 Desorption of Hg from the gold trap.

11.3.1 Remove the (sample) trap from the

bubbler, place the Nichrome wire coil around

the trap and connect the trap into the

analyzer train between the incoming Hg-free

argon and the second gold-coated (analytical)

sand trap (Figure 2).

11.3.2 Pass argon through the sample and

analytical traps at a flow rate of

approximately 30 mL/min for approximately

2 min to drive off condensed water vapor.

11.3.3 Apply power to the coil around the

sample trap for 3 minutes to thermally desorb

the Hg (as Hg(0)) from the sample trap onto

the analytical trap.

11.3.4 After the 3-min desorption time,

turn off the power to the Nichrome coil, and

cool the sample trap using the cooling fan.

11.3.5 Turn on the chart recorder or other

data acquisition device to start data

collection, and apply power to the Nichrome

wire coil around the analytical trap. Heat the

analytical trap for 3 min (1 min beyond the

point at which the peak returns to baseline).

11.3.6 Stop data collection, turn off the

power to the Nichrome coil, and cool the

analytical trap to room temperature using the

cooling fan.

11.3.7 Place the next sample trap in line

and proceed with analysis of the next

sample.

Note: Do not heat a sample trap while the

analytical trap is still warm; otherwise, the

analyte may be lost by passing through the

analytical trap.

11.4 Peaks generated using this technique

should be very sharp and almost

symmetrical. Mercury elutes at

approximately 1 minute and has a width at

half-height of about 5 seconds.

11.4.1 Broad or asymmetrical peaks

indicate a problem with the desorption train,

such as improper gas flow rate, water vapor

on the trap(s), or an analytical trap damaged

by chemical fumes or overheating.
28880 Federal Register / Vol. 63, No. 100 /Tuesday, May 26, 1998 / Proposed Rules

11.4.2 Damage to an analytical trap is also

indicated by a sharp peak, followed by a

small, broad peak.

11.4.3 If the analytical trap has been

damaged, the trap and the fluoropolymer

tubing downstream from it should be

discarded because of the possibility of gold

migration onto downstream surfaces.

11.4.4 Gold-coated sand traps should be

tracked by unique identifiers so that any trap

producing poor results can be quickly

recognized and discarded.

12.0 Data Analysis and Calculations

12.1 Calculate the mean peak height or

area for bubbler blanks, ‘‘BB’’ (n = at least 3).

12.2 Calculate the concentration of Hg in

ng/L (parts-per-trillion; ppt) in each sample

according to the following equation:

[ ]( / ) Hg ng L

A A

CF V

s BB

m s

= −

×

where:

As = peak height (or area) for Hg in sample

ABB = peak height (or area) for Hg in bubbler

blank

CFm = mean calibration factor (Section

10.1.1.5)

Vs = sample volume in liters

12.3 Calculate the concentration of Hg in

the reagent blank (CRB), in ng/L, using the

equation in Section 12.2 and substituting the

peak height or area resulting from the reagent

blank for As. If the Hg in the reagent blank

is attributable to Hg in the BrCl, correct the

concentration of Hg in the reagent blank by

the volume of BrCl used for the particular

sample (Section 11.1.1.2) using the following

equation:

C V

V RB

BS

VBRB

=

where:

VBS = volume of BrCI solution used in

sample (Section 11.1.1.2)

VBRB = volume of BrCI solution used in

reagent blank (Section 9.4.2.2)

12.4 Reporting

12.4.1 Report results for Hg at or above

the ML, in ng/L, to three significant figures.

Report results for Hg in samples below the

ML as <0.5 ng/L, or as required by the

regulatory authority or in the permit. Report

results for Hg in reagent blanks at or above

the ML, in ng/L, to three significant figures.

Report results for Hg in reagent blanks below

the ML but at or above the MDL to two

significant figures. Report results for Hg not

detected in reagent blanks as > 0.2 ng/L, or

as required by the regulatory authority or in

the permit.

12.4.2 Report results for Hg in samples

and reagent blanks separately, unless

otherwise requested or required by a

regulatory authority or in a permit. If blank

correction is requested or required, subtract

the concentration of Hg in the reagent blank

from the concentration of Hg in the sample

to obtain the net sample Hg concentration.

12.4.3 If the laboratory achieved an MDL

lower than 0.2 ng/L (Section 1.5), a new ML

may be calculated by multiplying the

laboratory-determined MDL by 3.18 and

rounding the result to the number nearest to

(1, 2, or 5) × 10n, where n is an integer.

Results below these levels should be reported

as above using the lower MDL and ML.

13.0 Method Performance

13.1 This method was tested in 12

laboratories using reagent water, freshwater,

marine water and effluent (Reference 18).

The quality control acceptance criteria listed

in Table 2 were verified by data gathered in

the interlaboratory study, and the method

detection limit (MDL) given in Section 1.5

was verified in all 12 laboratories. In

addition, the techniques in this Method have

been intercompared with other techniques

for low-level mercury determination in water

in a variety of studies, including ICES–5

(Reference 19) and the International Mercury

Speciation Intercomparison Exercise

(Reference 20).

13.2 Precision and recovery data for

reagent water, freshwater, marine water, and

secondary effluent are given in Table 3.

14.0 Pollution Prevention

14.1 Pollution prevention encompasses

any technique that reduces or eliminates the

quantity or toxicity of waste at the point of

generation. Many opportunities for pollution

prevention exist in laboratory operation. EPA

has established a preferred hierarchy of

environmental management techniques that

places pollution prevention as the

management option of first choice. Whenever

feasible, laboratory personnel should use

pollution prevention techniques to address

their waste generation. When wastes cannot

be reduced feasibly at the source, the Agency

recommends recycling as the next best

option. The acids used in this Method should

be reused as practicable by purifying by

electrochemical techniques. The only other

chemicals used in this Method are the neat

materials used in preparing standards. These

standards are used in extremely small

amounts and pose little threat to the

environment when managed properly.

Standards should be prepared in volumes

consistent with laboratory use to minimize

the disposal of excess volumes of expired

standards.

14.2 For information about pollution

prevention that may be applied to

laboratories and research institutions, consult

Less is Better: Laboratory Chemical

Management for Waste Reduction, available

from the American Chemical Society’s

Department of Governmental Relations and

Science Policy, 1155 16th Street NW,

Washington DC 20036, 202/872–4477.

15.0 Waste Management

15.1 The laboratory is responsible for

complying with all Federal, State, and local

regulations governing waste management,

particularly hazardous waste identification

rules and land disposal restrictions, and for

protecting the air, water, and land by

minimizing and controlling all releases from

fume hoods and bench operations.

Compliance with all sewage discharge

permits and regulations is also required.

15.2 Acids, samples at pH <2, and BrCl

solutions must be neutralized before being

disposed of, or must be handled as hazardous

waste.

15.3 For further information on waste

management, consult Less is Better:

Laboratory Chemical Management for Waste

Reduction, both available from the American

Chemical Society’s Department of

Government Relations and Science Policy,

1155 16th Street NW, Washington, DC 20036.

16.0 References

1. Bloom, Nicolas, Draft ‘‘Total Mercury in

Aqueous Media’’, Frontier Geosciences, Inc.,

September 7, 1994.

2. Fitzgerald, W.F.; Gill, G.A. ‘‘SubNanogram Determination of Mercury by TwoStage Gold Amalgamation and Gas Phase

Detection Applied to Atmospheric Analysis,’’

Anal. Chem. 1979, 15, 1714.

3, Bloom, N.S; Crecelius, E.A.

‘‘Determination of Mercury in Sea water at

Subnanogram per Liter Levels,’’ Mar. Chem.

1983, 14, 49.

4. Gill, G.A.; Fitzgerald, W.F. ‘‘Mercury

Sampling of Open Ocean Waters at the

Picogram Level,’’ Deep Sea Res 1985, 32, 287.

5. Bloom, N.S.; Fitzgerald, W.F.

‘‘Determination of Volatile Mercury Species

at the Picogram Level by Low-Temperature

Gas Chromatography with Cold-Vapor

Atomic Fluorescence Detection,’’ Anal.

Chim. Acta. 1988, 208, 151.

6. Guidance on Establishing Trace Metal

Clean Rooms in Existing Facilities, U.S.

Environmental Protection Agency, Office of

Water, Office of Science and Technology,

Engineering and Analysis Division (4303),

401 M Street SW, Washington, DC 20460,

January 1996, EPA 821–B–96–001.

7. Trace Metal Cleanroom, prepared by

Research Triangle Institue for U.S.

Environmental Protection Agency, 26 W.

Martin Luther King Dr., Cincinnati, OH

45268, RTI/6302/04–02 F.

8. Guidance on the Documentation and

Evaluation of Trace Metals Data Collected for

Clean Water Act Compliance Monitoring,

U.S. Environmental Protection Agency,

Office of Water, Office of Science and

Technology, Engineering and Analysis

Division (4303), 401 M Street SW,

Washington, DC 20460, July 1996, EPA 821–

B–96–004.

9. Method 1669, ‘‘Method for Sampling

Ambient Water for Determination of Metals

at EPA Ambient Criteria Levels,’’ U.S.

Environmental Protection Agency, Office of

Water, Office of Science and Technology,

Engineering and Analysis Division (4303),

401 M Street SW, Washington, DC 20460,

April 1995 with January 1996 revisions.

10. ‘‘Working with Carcinogens,’’

Department of Health, Education, and

Welfare, Public Health Service. Centers for

Disease Control. NIOSH Publication 77–206,

Aug. 1977, NTIS PB–277256.

11. ‘‘OSHA Safety and Health Standards,

General Industry,’’ OSHA 2206, 29 CFR 1910.

12. ‘‘Safety in Academic Chemistry

Laboratories,’’ ACS Committee on Chemical

Safety, 1979.

13. ‘‘Standard Methods for the

Examination of Water and Wastewater,’’ 18th

ed. and later revisions, American Public

Health Association, 1015 15th Street NW,

Washington, DC 20005. 1–35: Section 1090

(Safety), 1992.
Federal Register / Vol. 63, No. 100 /Tuesday, May 26, 1998 / Proposed Rules 28881

14. Bloom, N.S. ‘‘Trace Metals & UltraClean Sample Handling,’’ Environ. Lab. 1995,

7, 20.

15. Bloom, N.S. ‘‘Influence of Analytical

Conditions on the Observed ‘Reactive

Mercury,’ Concentrations in Natural Fresh

Waters.’’ In Mercury as a Global Pollutant;

Huckabee, J. and Watras, C.J., Eds.; Lewis

Publishers, Ann Arbor, MI: 1994.

16. ‘‘Handbook of Analytical Quality

Control in Water and Wastewater

Laboratories,’’ U.S. Environmental Protection

Agency. Environmental Monitoring Systems

Laboratory, Cincinnati, OH 45268, EPA–600/

4–79–019, March 1979.

17. Liang, L.; Bloom, N.S. ‘‘Determination

of Total Mercury by Single-Stage Gold

Amalgamation with Cold Vapor Atom

Spectrometric Detection,’’ J. Anal. Atomic

Spectrom. 1993, 8, 591.

18. ‘‘Results of the EPA Method 1631

Validation Study,’’ February, 1998. Available

from the EPA Sample Control Center, 300 N.

Lee St., Alexandria, VA, 22314; 703/519–

1140.

19. Cossa, D.; Couran, P. ‘‘An International

Intercomparison Exercise for Total Mercury

in Sea Water,’’ App. Organomet. Chem. 1990,

4, 49.

20. Bloom, N.S.; Horvat, M.; Watras, C.J.

‘‘Results of the International Mercury

Speciation Intercomparison Exercise,’’ Wat.

Air. Soil Pollut., in press.

17.0 Glossary

The definitions and purposes below are

specific to this Method, but have been

conformed to common usage as much as

possible.

17.1 Ambient Water—Waters in the

natural environment (e.g., rivers, lakes,

streams, and other receiving waters), as

opposed to effluent discharges.

17.2 Analytical Batch—A batch of up to

20 samples that are oxidized with the same

batch of reagents and analyzed during the

same 12-hour shift. Each analytical batch

must also include at least three bubbler

blanks, an OPR, and a QCS. In addition, MS/

MSD samples must be prepared at a

frequency of 10% per analytical batch (one

MS/MSD for every 10 samples).

17.3 Bubbler Blank—Analyzed to

demonstrate freedom from system

contamination. Immediately after analyzing a

sample, water in the bubbler is purged and

analyzed using the same procedure as for the

samples to determine Hg. The blank is

somewhat different between days, and a

minimum of three bubbler blanks must be

analyzed per analytical batch. The average of

the results for the three bubbler blanks is

subtracted from the result of analysis of each

sample to produce a final result.

17.4 Intercomparison Study—An exercise

in which samples are prepared and split by

a reference laboratory, then analyzed by one

or more testing laboratories and the reference

laboratory. The intercomparison, with a

reputable laboratory as the reference

laboratory, serves as the best test of the

precision and accuracy of the analyses at

natural environmental levels.

17.5 Matrix Spike (MS) and Matrix Spike

Duplicate (MSD)—Aliquots of an

environmental sample to which known

quantities of the analyte(s) of interest is

added in the laboratory. The MS and MSD

are analyzed exactly like a sample. Their

purpose is to quantify the bias and precision

caused by the sample matrix. The

background concentrations of the analytes in

the sample matrix must be determined in a

separate aliquot and the measured values in

the MS and MSD corrected for these

background concentrations.

17.6 May—This action, activity, or

procedural step is allowed but not required.

17.7 May not—This action, activity, or

procedural step is prohibited.

17.8 Minimum Level (ML)—The lowest

level at which the entire analytical system

must give a recognizable signal and

acceptable calibration point for the analyte.

It is equivalent to the concentration of the

lowest calibration standard, assuming that all

method-specified sample weights, volumes,

and cleanup procedures have been

employed. The ML is calculated by

multiplying the MDL by 3.18 and rounding

the result to the number nearest to (1, 2, or

5) – 10n, where n is an integer.

17.9 Must—This action, activity, or

procedural step is required.

17.10 Quality Control Sample (QCS)—A

sample containing Hg at known

concentrations. The QCS is obtained from a

source external to the laboratory, or is

prepared from a source of standards different

from the source of calibration standards. It is

used as an independent check of instrument

calibration.

17.11 Reagent Water—Prepared from 18

MΩ ultrapure deionized water starting from

a prepurified source. Reagent water is used

to wash bottles, as trip and field blanks, and

in the preparation of standards and reagents.

17.12 Regulatory Compliance Limit—A

limit on the concentration or amount of a

pollutant or contaminant specified in a

nationwide standard, in a permit, or

otherwise established by a regulatory

authority.

17.13 Shall—This action, activity, or

procedure is required.

17.14 Should—This action, activity, or

procedure is suggested, but not required.

17.15 Stock Solution—A solution

containing an analyte that is prepared from

a reference material traceable to EPA, NIST,

or a source that will attest to the purity and

authenticity of the reference material.

17.16 Ultraclean Handling—A series of

established procedures designed to ensure

that samples are not contaminated during

sample collection, storage, or analysis.

18.0 Tables and Figures

TABLE 1.—LOWEST AMBIENT WATER QUALITY CRITERION FOR MERCURY AND THE METHOD DETECTION LIMIT AND

MINIMUM LEVEL OF QUANTITATION FOR EPA METHOD 1631

Metal

Lowest ambient

water quality criterion 1

Method detection limit (MDL) and minimum level (ML)

MDL2 ML3

Mercury (Hg) .......................................................................................................... 1.8 ng/L 0.2 ng/L 0.5 ng/L

1 Lowest water quality criterion for the Great Lakes System (60 FR 15366, March 23, 1995). The lowest Nationwide criterion is 12 ng/L (40

CFR 131.36). 2 Method detection limit (40 CFR 136, Appendix B).

3 Minimum level of quantitation (see Glossary).

TABLE 2.—QUALITY CONTROL ACCEPTANCE CRITERIA FOR PERFORMANCE TESTS IN EPA METHOD 1631

Acceptance criteria Section Limit (%)

Initial precision and recovery (IPR) .................................................................................................................................. 9.2.2 ....................

Precision (s) .............................................................................................................................................................. 9.2.2.3 21

Recovery (X) ............................................................................................................................................................. 9.2.2.3 79–121

Ongoing precision and recovery (OPR) ........................................................................................................................... 9.5.2 77–123

Matrix spike/matrix spike duplicate (MS/MSD) ................................................................................................................ 9.3 ....................

Recovery ................................................................................................................................................................... 9.3.4 75–125

Relative percent difference (RPD) ............................................................................................................................ 9.3.5 24
28882 Federal Register / Vol. 63, No. 100 /Tuesday, May 26, 1998 / Proposed Rules

TABLE 3.—PRECISION AND RECOVERY FOR REAGENT WATER, FRESH WATER, MARINE WATER, AND EFFLUENT WATER

USING METHOD 1631

Matrix * Mean recovery (%)

*Precision

(% RSD)

Reagent water .................................................................................................................................................................. 98.0 5.6

Fresh water (filtered) ........................................................................................................................................................ 90.4 8.3

Marine water (filtered) ...................................................................................................................................................... 92.3 4.7

Marine water (unfiltered) .................................................................................................................................................. 88.9 5.0

Secondary effluent (filtered) ............................................................................................................................................. 90.7 3.0

Secondary effluent (unfiltered) ......................................................................................................................................... 92.8 4.5

* Mean percent recoveries and RSDs are based on expected Hg concentrations.

BILLING CODE 6560–50–P
Federal Register / Vol. 63, No. 100 /Tuesday, May 26, 1998 / Proposed Rules 28883
28884 Federal Register / Vol. 63, No. 100 /Tuesday, May 26, 1998 / Proposed Rules

[FR Doc. 98–13783 Filed 5–22–98; 8:45 am]

BILLING CODE 6560–50–C