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astfJMSSKS®KIs-pubAn International Butyltin

Measurement Methods Intercomparison:

Sample Preparation and Results of

Analyses

NBS

PUBLICATIONS

W. R. Blair, G. J. Olson, F. E. Brinckman

U.S. DEPARTMENT OF COMMERCE

National Bureau of Standards

Institute for Materials Science and Engineering

Ceramics Division

Surface Chemistry and Bioprocesses Group

Gaithersburg, MD 20899

R. C. Paule

National Measurement Laboratory

National Bureau of Standards

Gaithersburg, MD 20899

and

D. A. Becker

Nuclear Methods Group

National Bureau of Standards

Gaithersburg, MD 20899

February 1 986

-QC

100 r

. U66 Naval Research

86-3321 ' VA 22217

1986

C- 2

NBSIR 86-3321

AN INTERNATIONAL BUTYLTIN

MEASUREMENT METHODS INTERCOMPARISON:

SAMPLE PREPARATION AND RESULTS OF

ANALYSES

EESSAHCH INFORMATION CENTER tirc-M gs

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W. R. Blair, G. J. Olson, F. E. Brinckman

U.S. DEPARTMENT OF COMMERCE

National Bureau of Standards

Institute for Materials Science and Engineering

Ceramics Division

Surface Chemistry and Bioprocesses Group

Gaithersburg, MD 20899

R. C. Paule

National Measurement Laboratory

National Bureau of Standards

Gaithersburg, MD 20899

and

D. A. Becker

Nuclear Methods Group

National Bureau of Standards

Gaithersburg, MD 20899

February 1 986

Prepared for Office of Naval Research

Arlington, VA 22217

U.S. DEPARTMENT OF COMMERCE. Malcolm Baldrige, Secretary

NATIONAL BUREAU OF STANDARDS, Ernest Ambler. Director

AN INTERNATIONAL BUTYLTIN MEASUREMENT METHODS INTERCOMPARISON: SAMPLE

PREPARATION AND RESULTS OF ANALYSES

W. R. Blair"' , G. J. Olson 1

, F. E. Brinckman 1

, R. C. Paule^ and D. A. Becker^

1 Surface Chemistry and Bioprocesses Group, National Bureau of Standards

National Measurement Laboratory, National Bureau of Standards

^Nuclear Methods Group, National Bureau of Standards

Abstract

A comparison of organotin measurement methods has been conducted with

a new tributyltin research sample distributed to over 40 laboratories

worldwide. A description of background research into the behavior and

manipulation of low concentration aqueous organotin solutions, chromatographic production of the speciated aqueous organotin research material,

and quantitative results from the methods intercomparison are reported

here along with recommendations for future work.

Keywords: chemical speciation; liquid chromatography; methods intercomparison; molecular character ization ; round-robin; research material;

stability; tributyltin; ultratrace organotin solutions

Certain trade names and company products are mentioned for identification

purposes only and in no case does it imply recommendation or endorsement by

the National Bureau of Standards.

2

1 . 0 Introduct ion

Worldwide production of organotin chemicals has increased

significantly over the past 30 years, to a present level of more than

35,000 tons annually (1). Numerous applications as catalysts, polymer

stabilizers, and tailored biocides have resulted from the highly varied

chemical and biological properties provided by different classes of

organotin( IV) compounds. For example, some recent studies (2,3) have

quantitatively correlated the number, size, and shape of organic moieties

bound to tin with physicochemical and toxic properties of the molecule,

with triorganotins displaying greatest effects towards most organisms. The

mono- and di- organotins, RSnXg and R

2SnX2

, are widely employed as heat

and light stabilizers in the PVC plastics industry (4) and as catalysts

for silicones and polyurethane foams (5). The highly selective biocidal

properties of triorganotin compounds, R^SnX, chiefly dependent upon the

kind of tin-bound organic groups, have resulted in their wide use as the

active ingredient in wood preservatives, antifouling paints, fungicides,

and miticides (6-9). Among the organic groups proven in laboratory and

extensive field testing to be most generally effective as preservatives,

antifoulants, and fungicides, the tri-n-butyltin moiety has received

greatest commercial impetus (10), and it is with this class that

significant commercial growth is anticipated. Tetraorganotins , R^Sn, have

no large industrial outlets, but are used mainly as intermediates in the

manufacture of other organotin compounds (1,11).

3
As the use of organotins has increased, international scrutiny of the

fate and effect of these compounds in the environment has also increased.

These concerns are reflected in environmental assessments and pollution

evaluations compiled by industry (12) and national environmental agencies

of several countries (13~15), including the United States Navy (16). For

example, in a situation where aquated tributyltin ion is toxic to some

sensitive aquatic organisms at yg/L (ppb) levels (17), and the dibutyltin

compound is comparatively nontoxic (3), it is essential that monitoring

methods yield chemical speciation data for all the active organotins

present in an environmental sample in order to provide a rational,

equitable and effective basis for regulation. Numerous methods for the

determination of total tin are described in analytical literature (13.18),

but unfortunately, the bulk of these methods are inapplicable to

isolation, separation, and quantitation of organotins in environmental

media at relevant ppb action levels.

1.1 Current Status of Organotin Measurements

Within the past several years many new methods have been described

which provide the required trace organotin speciation information. Examples

are summarized in Table 1 (Table 1 adapted from: The Occurrence and

Pathways of Organometallic Compounds in the Environment-General

Considerations, P. Craig and F. E. Brinckman, in The Environmental Chemistry

of Organometals , P. Craig, Ed., Longmans-Green, London, 1985) which illustrate

the basic steps of analyte preconcentration. In general, most of these

methods rely on two-phase solvent extraction of the organotins from the

environmental sample, concentration and often derivatization by sodium

4
borohydride or Grignard reagents before chromatographic or boiling point

separation with tin determination by a tin-selective (flame photometric)

(19) or tin-specific (atomic absorption) detector (20). With the

availability of analytical techniques possessing the requisite speciation

and detection level capabilities, reports began to appear concerning the

environmental distribution of organotins, revealing a globally dispersed

baseline concentration of methyltins at the ng/L level in aquatic systems

(21). Since methyltins are not commercially produced in major amounts, the

pathway for their formation could involve both biological (22) and abiotic

(23,24) methylation of inorganic tin or biodegradation of the man-made

organotins discussed above (25,26 ). The need to elucidate further the

biogeochemical cycles of tin is reinforced by the development and rapidly

emerging use, on a worldwide basis, of tri-n-butyltin-containing marine

antifoulant coatings. Although the potential for food chain accumulation of

tributyltin via a marine microbial pathway has been reported (27) very

little else is known about the environmental persistence, degradation rates,

and possible accumulation sites of tributyltin, though recent unpublished

reports suggest an environmental half-life of less than two weeks in certain

samples of marine and estuarine waters (G. J. Olson, unpublished results;

P. Seligman and R. Lee, personal communication).

1 .2 Basis and Scope of an Organotin Measurement Methods Intercomparison

Anticipating the need of reference standards for calibration and

intercomparison of current and future organotin analytical methods, the

National Bureau of Standards, with support of the Office of Naval Research,

initiated a program to evaluate the factors essential to conducting an

5
interlaboratory measurement methods comparison for organotins. Among the

chief parameters to be assessed were:

(a) Choice of most significant and representative organotin analyte and

matrix suitable for diverse participants and analytical state of art;

(b) Evaluation of contact materials and mode of preparation, storage,

and transport of candidate interlaboratory organotin research materials;

(c) Concurrent with, and in support of, (a) and (b), elucidation of the

appropriate solution chemistry and mode(s) of preparation of a stable

organotin analyte affording sufficient shelf life for present and future

intercomparisons, and ultimately assuring a means for certified reference

materials preparation (28).

(d) Merging successful features of (a), (b), and (c) in an inaugural

intercomparison protocol suited to international participation and

uncomplicated sample delivery and reportage.

1.3 Organization of the Organotin Intercomparison Study

Frequent contacts with colleagues, collaborators, and our NBS sponsors

over recent years made clear the marked preference for an initial comparison

of various methods for the quantitation of the tributyltin cation species,

especially in aqueous medium, irrespective of geganions. Not only was

selection of this prospective analyte consistent with the bulk of most

recent analytical literature (Table 1), this biocidal species has received

the greatest attention among environmentalists and regulatory bodies in the

homelands of all of the proposed participants. For some years, our

laboratory has dealt with trace organotins, including tri-n-butyltin , and

this familiarity with the manipulative difficulties of organotins provided

6
an opportunity to assess closely questions of contact and container

materials, solution stability and effects of light, impurities, and chemical

forms. Moreover, our experience with trace chemical speciation studies of a

variety of neutral and ionic organotins based upon liquid chromatographic

separation schemes (29), lent credence to successful development of a

tri-n-butyltin solution of high purity suited to the stringent requirements

of an intercomparison study.

1.4 Development of the Experimental Plan

Prior to design of the organotin sample generation apparatus or

selection of a sample container, the effects of four container materials

on the stability of low concentration aqueous solutions of tri-n-butyltin

were evaluated. The containers were commercially available bottles (125 to

250 mL) made of borosilicate glass (Pyrex), polytetrafluoroethylene

(Teflon), polycarbonate, and conventional polyethylene. Deionized water

was chosen as the sample solvent because our earlier studies suggested its

suitability as a universal medium for both neutral and ionic organotin

compounds at low concentrations, e.g., ppm (1 mg/L) or less, which was the

target concentration of an intercomparison material. Moreover, choice of

water provided a safe and transportable, non-toxic, non-flammable medium

suitable for easy dilutions by participants or other later users directly

into freshwater and marine samples acquired from the field, thereby

permitting methods of additions assessments. Finally, previous evidence

from our laboratory for both analytical- and preparative-scale quantitative

separations by aqueous ion-exchange liquid chromatography of organotins

7
suggested (29) a reliable method for producing pure tri-n-butyltin in water

at ppm levels in quantities sufficient for a major round-robin protocol.

All of these design and production factors were consistent with the

primary goal of the project: to cheaply and reproducibly produce and

disseminate ample-sized packages of a relevant organotin in an appropriate

solvent at some stable concentration. This allows round-robin participants

the flexibility to dilute the sample in ways consistent with their own

techniques but not compromising either quantification or chemical

speciation analyses over extended periods of time.

2.0 Experimental

Specific details of the tin-specific quantitative analyses of aqueous

solutions of inorganic and organotins, including butyltins, employing

graphite furnace atomic absorption spectrophotometry (GFAA) have been

reported in several recent papers ( 29—32 )

.

2.1 Chemicals and Materials

The tin compounds used in this work were purchased commercially and

used as received, with the exception of the bis( tributyltin)oxide (Alfa

Products, Danvers, MA 01923) used in preparation of the research material,

which was purified by vacuum (0.01 Torr) distillation just prior to use.

All laboratory glassware used for preparation, storage, and dilution of

stock organotin solutions and the various storage bottles used in this

work were cleaned prior to use by leaching for 24 to 48 hours with dilute

aqueous nitric acid (5 to 105?). When container size allowed, the

acid-filled bottles and glassware were placed in a warm water bath

8
(approximately at 40° C) during leaching. After leaching, all items were

rinsed 4 to 5 times with deionized water of 15 to 18 megaohm cm"^ resistance

(Aqua Suma 36, Culligan Water Conditioning, Vienna, VA 22180).

2.2 Organotin Analytical Procedures for Aqueous Media

The methods described below emphasize marine or saline media, which

represent difficult matrices in environmental analyses, but are also

applicable to fresh water samples.

2.2.1 Total Tin Determination by Graphite-Furnace Atomic-Absorption

Spectroscopy (GFAA)

A sensitive method for determination of the levels of total

extractable organotin compounds present in aqueous saline samples has been

developed at NBS and is described in detail in a separate publication

(30). Basically, the method recommends preconcentration of the organotin

compounds in a sample by extraction into toluene, followed by determination

of total tin concentration by graphite furnace atomic absorption (GFAA)

spectroscopy. Both the sensitivity and element specificity needed to

determine nanogram quantities of tin are provided by GFAA, but sensitivity

suffers significant losses when the sample matrix contains salts. For this

reason, the toluene extract must be washed several times with deionized

water prior to GFAA analysis.

Enhancement of GFAA sensitivity can be achieved by physical, chemical,

or combined methods. Physical enhancement involves inserting graphite

platforms, referred to as L'vov platforms (33) into the conventional furnace

tube. Analyte volatilization is delayed by the elevated platform, which

9
reaches maximum temperature more slowly than the furnace tube itself,

thereby reducing the probability that analyte will be volatilized before the

absorption signal is measured. The L'vov platform thus provides a physical

means of signal enhancement for a number of elements. Additionally, we have

discovered a chemical matrix modification technique employing transition

metal oxo-salts that specifically provide signal enhancement for tributyltin

compounds (3*0.

2.2.2 Molecular Tin Quantitation

Determining the molecular species of organotins present in saline

aqueous samples is routinely done at NBS by simultaneously hydridizing the

sample with sodium borohydride while extracting with dichloromethane

(35,36). The dichloromethane extract is injected into a gas chromatograph

equipped with a flame photometric detector for identification of the

organotins present. For a typical analysis of saline water with butyltin

concentrations in the sub-pg/L range (as tin), the following procedure has

been developed. To a 1 00-mL of sample in a 1 25-mL glass separatory funnel

equipped with a Teflon stopcock and Teflon-lined screw cap, add 2.8 mL

dichloromethane and 2.0 mL of 4 % (w/v) aqueous NaBH^. A 1 0 pL spike of

0.5 pg/mL aqueous solution of di-n-propyltin dichloride can be added to

the sample to serve as an internal calibrant. The funnel is then capped,

shaken by hand for 15 to 30 seconds, vented and then shaken (240

strokes/min) on a wrist action shaker for 10 min. Following a 5 min.

settling period, the bottom organic layer is removed. An additional

1.4 mL of dichloromethane is added and the 10 min. extraction repeated.

The organic layers are combined in small (approx. 2 mL volume) polypropylene

10
centrifuge tubes and the solvent volume reduced to 100 to 500 yL by

evaporation with a gentle stream of air. Appropriate blanks are carried

through the same procedure. While most of our work has been done with

samples of 100 mL volume, samples of 800 to 1000 mL have been analyzed

using 1 liter separatory funnels and proportionately larger volumes of all

reagents. Sensitivity when using 100 mL samples is approximately 7 ng Sn/L

for tetrabutyltin and tri-n-butyltin, 3 ng Sn/L for dibutyltin and 22 ng

Sn/L for mono-n-butyltin.

2.3 Stability of Dilute Aqueous Tri-n-Butyltin Solutions in Various

Container Materials

A series of 125 mL and 250 mL screw-capped bottles, typical of those

employed in most analytical laboratories were chosen for evaluating both

short- and long-term effects of various container materials on dilute

aqueous tri-n-butyltin solutions. In addition to considerations of

chemical effects by wetted materials, surface-to-volume, leakage,

resistance to impact, and cost played important roles in selection of test

containers, purchased from a number of commercial suppliers.

Four different commercial container materials were used in the study:

Pyrex glass; Teflon; polycarbonate; and conventional ("low-density")

polyethylene. One bottle of each material was filled with a freshly

prepared stock solution of 30 ppb (30 yg/L as Sn) of either stannous

chloride, SnCl 2

, or tri-n-butyltin chloride in deionized water. This

concentration range was selected as that representing the convenient

measurement range for analytical methods either providing total tin or

molecular tin quantitation, and was consistent with the upper limits of

11
the recommended dilution range to be suggested in the interlaboratory

protocol sent to each participant (see Section 3-1 and Appendix I).

Corresponding numbers and types of bottles filled with deionized water

served as controls. In those cases where effects of citric acid were

evaluated, the deionized water used was heat-sterilized to prevent any

stimulation of microbial activity by the citrate, a potential bacterial

nutrient

.

All test containers and solution contents were maintained in the dark

at ambient temperature (ca. 22° C) during the entire study. Small aliquots

of each test solution were periodically taken by an adjustable pipet with

a disposable polypropylene tip for total tin determination by GFAA. At

each sampling time corresponding samples of control bottle and SnCl 2 test

bottle solutions were also compared with a freshly prepared external tin

standard (SnCl 2

) solution. All periodic analyses were conducted in

replicate (5 determinations) and the means ± standard deviations of single

measurements were plotted against time (Figures 1 and 2).

2.3.1 Selection of Container Material and Solvent for the Tributyltin

Research Material.

The effects of container materials on tin solution stability are

presented graphically in Figure 1 . Although some loss of solution

strength is evident for all container materials, the loss seen for a

tributyltin solution stored in a polyethylene bottle is the most dramatic.

This finding illustrates the unsuitability of polyethylene materials for

use in trace level organotin work. Experience in our laboratory with

pyrex glass and polycarbonate materials indicates that either is

12
acceptable for use as organotin solution or environmental sample container.

An additional solution stability experiment was conducted with polyethylene

bottles to determine if the adsorbent effect of the polyethylene could be

moderated by addition of 0.01M citric acid to the tin solutions. Figure 2

shows that the citric acid added to the tin solutions did prevent the rapid

adsorption of tributyltin by polyethylene.

2.4 Chromatographic Preparation of Aqueous Tri-n-Butyltin Solution

The speciated, aqueous tributyltin research sample distributed for

the organotin measurement methods intercomparison was prepared using the

apparatus described below and illustrated in Figure 3. The entire research

sample was made in a single 12 liter batch to insure sample homogeneity. A

generator column technique was used to produce a saturated aqueous solution

of tributyltin which was immediately diluted on-line to prevent precipitation. The generator column consisted of a 6 mm OD Pyrex tube joined to a

short section of 9 mm Pyrex tubing. The overall column was 40 cm in length,

the column bed was 25 cm in length and entirely enclosed in a water jacket

for temperature control. Water jacket temperature was controlled by

connection to a constant temperature bath. Generator column temperature

(approx. 15°C) was maintained sufficiently below ambient (20-22°C) to insure

that no tributyltin species would precipitate from solution upon elution

from the generator column. The column packing, Chromosorb W HP 100/120 mesh,

(Supelco, Inc., Bellfonte, PA 16823) was retained in the column by silanized

glass wool plugs.

A pair of large 13“liter Pyrex glass bottles were employed as deionized

water reservoir and final organotin solution receiving vessel, respectively.

13
The solution in each bottle was stirred with teflon covered stirring bars

and purged with high purity nitrogen continuously from before organotin

solution generation began until the sample was subdivided into 125 mL

bottles for final storage and distribution. A stainless steel duplex LC

pump (Model 2396, LDC/Milton-Roy Co., Rivera Beach, FL 33404) pumped source

water through the generator column and to a ’T’ fitting located at the

eluent end of the chromatographic generator column. With the exception of

the stainless steel components in the pump head, the wetted surfaces of the

sample preparation apparatus were composed exclusively of borosilicate glass

(Pyrex) or teflon. Since the bis( tributyltin)oxide (TBTO) used to load the

generator column was introduced to the system downstream of the LC pump, the

organotin-containing effluent came into contact only with glass or teflon

surfaces, always under a nitrogen atmosphere. This anaerobic exposure to

container materials was maintained throughout the entire process of analyte

generation. Nitrogen purging of the receiving vessel continued until all

the 125 mL sample bottles were filled. No attempt was made to fill the

125 mL sample bottles under controlled atmosphere conditions, they were

filled and sealed in laboratory air.

2.4.1 Chromatographic and Sample Bottling Procedure

With the LC pump off, approx. 100 microliters of neat redistilled

bis( tributyltin)oxide was added to the top of the generator column using

an all-glass syringe and a teflon needle. Deionized water flow at 0.5 mL

per minute was then started through the generator column, and an equal

separate flow was delivered to the ’T' fitting just downstream of the

column. Tin concentration in the effluent was periodically monitored by
graphite furnace atomic absorption (GFAA) to establish dilution ratios and

column performance. When the tin concentration in the column effluent

reached equilibrium, typically after 2-3 hours, the effluent was collected

in the solution receiving bottle. When GFAA monitoring of the effluent

indicated a drop in tin concentration, usually after 18 to 20 hours, the

generator column was reloaded with TBTO, the column reequilibrated, and the

solution once again collected in the solution receiving reservoir.

The complete tri-n-butyltin batch solution so prepared was subdivided

in two decanting sessions into new 125 mL borosilicate glass bottles

secured with teflon-lined caps. Prior to filling, the bottles were rinsed

with methanol, then acid leached as described above, and dried in a

laboratory oven. After filling with tri-n-butyltin solution, each bottle

was immediately capped with a teflon lined screw cap and wrapped in

parafilm M sealer and, to exclude light, aluminum foil. The order of

filling sample bottles was noted for future reference by sequential

numbering of each bottle as it was filled then wrapped. All sample bottles

so prepared were maintained at ambient conditions, 22-25 °C, 40—60% R.H.

during and since, excepting those shipped to participants.

2.4.2 Distribution of the Tri-n-Butyltin Samples and Follow-up Studies

Following communication with proposed laboratories and verification

of their acceptance of the proposed intercomparison protocol (see Appendix

I), each participant was mailed a single bottle of the tributyltin

research material as prepared above. Bottles were selected randomly, since

the entire lot of numbered bottles had been remixed and blindly drawn for

mailing by a non-technical staff member. The actual sample identity

15
numbers were recorded for each participant laboratory. Since the total

number of samples prepared in the lot taken for this study exceeded the

number needed for participants, the Protocol (Appendix I) provided

accommodation to any participant requiring additional samples owing to

non-receipt or loss in the laboratory. In addition, the excess samples so

prepared permitted subsequent archival studies during and since the

round-robin completion. This has included random sacrifice of greater than

1056 of the remaining population to critically evaluate shelf stability or

modes of decomposition induced by analytical procedures, as suggested by

participants subsequent to their contributions. Several of these highly

significant findings are described in Section 3.0, with recommendations

for new work.

3.0 Results and Discussion

3.1 Protocol Used and Level and Character of Participation

Appendix I provides a facsimile of the initial contact letter,

response form, and details concerning each participants elected method(s)

of total and/or molecular tin analysis. Another section of the Protocol

illustrated in Appendix I details the uniform dilution scheme recommended

for each participating organization, and approximate sample concentration

range (expressed as total tin in yg/L) for guidance in instrumental

settings, and the preferred means to report numerical results for

statistical analysis at NBS. Specific information regarding the expected

shelf-life of the aqueous tributyltin samples, directions for obtaining

replicate samples in the event of misfortune, and the stringent means

16
exercised by the NBS for maintaining anonymity of each participant's

results, while yet providing a summary of the entire range of variability by

method or any preparation history was also provided. All the participating

laboratories (35 in total) cooperated expeditiously and fully, with only

several delays incurred by mailing or laboratory losses.

Table 1 lists some of the analytical methods currently available for

organotin determinations. Table 2 lists the participants by country, with

no identifying reference to their methods or submitted results. It can be

clearly seen from the distribution of nationality and type of organization

that an excellent response was obtained in this inaugural intercomparison.

Not only are contributors from tin-producing and using nations well

represented, so also are analytical experts representing academic,

governmental, and industrial laboratories.

3.2 Statistical Analysis of Results

Aliquot samples of an aqueous tributyltin solution, nominally at a

concentration of 1 yg/mL (1 ppm) were sent to nearly 50 laboratories.

Thirty-five sets of results from 32 tin samples were returned to NBS. As

discussed elsewhere in this report, the aliquot samples were believed to

contain only the tributyltin species. The analytical results from several

of the laboratories that undertook speciation analysis, however, have

shown other tin species. We believe these additional species may be

produced by the analytical procedures and are not representative of the

aliquot solution, as discussed below.

To avoid questions regarding the expression of analytical data, we

have converted the concentrations of all reported tin species to a total

tin concentration. The converted total tin data for the 35 sets of reported

17
results are listed in Table 3- An inspection of these data shows that 3 of

the sets of results (marked by asterisks) are very different from the results

of the remaining 32. The average results from these 3 laboratories are

0.03, 2.4, and 6.0 ppm tin. The extreme values of the averages from all

the remaining determinations are 0.30 and 1.6 ppm tin. The three results

(marked by asterisks) were judged to be outliers, and are not used further.

Each cooperating laboratory used its own method of analysis. We have

grouped the methods into 7 general categories (A-G), and have made a

preliminary statistical analysis on these groups. A general description of

the 7 groups is given in Table 4. The average tin values for the 7 groups

and the standard deviations of these averages are summarized in Table 5.

The averages are not significantly different from the nominal aliquot

solution value of 1 ppm tin. In general, there does not appear to be any

consistent biases between the 7 groups.

The combined results for the 32 laboratories with acceptable tin

determinations are rather remarkable for a methods intercomparison that

placed no constraint on the method employed for sample analysis. A

frequency diagram (histogram) of the laboratory results is shown in Figure

4. The analytical methods A-G are indicated in the figure. The results

tend to be distributed rather evenly about the central 1 ppm point, the

approximate true value of tin in the research sample. The histogram shows

an almost uniform distribution of analysis methods throughout the range of

concentrations reported, with a very narrow peak at the center. A more

detailed examination of the analytical methods comprising the narrow center

peak of 20 laboratory results shows a rather uniform distribution of methods

within the peak itself.

18
Since all of the different methods of analysis give very similar

results, we have chosen to ignore the analytical groupings in the

remaining statistical evaluations. A one-way analysis of variance (37,38)

was used to determine the within- and between-laboratory components of

variance. The square roots of these components of variance are called the

within- and between-laboratory components of standard deviation, and are

0.08 and 0.28 ppm tin, respectively. The within-laboratory imprecision of

0.08 ppm tin is small relative to the between-laboratory imprecision. This

is a common situation in inter laboratory studies. The overall average

total tin value from all laboratory results (excluding the 3 outlier results)

is 1.00 ± 0.05 ppm. The ± uncertainty is one standard deviation of the

average. The measurement method that we have chosen as the benchmark method

for determination of the true concentration of total tin in the research

material is neutron activation analysis (NAA). We feel it is the least

likely, of the methods available, to be subject to inaccuracies produced by

methodology or sample matrix interference. The total tin value measured at

NBS by neutron activation analysis for the research sample is 1.06 ±

0.05 ug/g (ppm). The relative standard deviation of the NAA analysis is

4.4 percent. The NAA procedure is described in Appendix II.

Because of the very unusual non-Gaussian distribution of laboratory

results from this study, we refrain from making general probability

statements. The interlaboratory results have been described by the

histogram and by the components of standard deviation. Based on our

experience with interlaboratory methods comparisons, it is believed that

these interlaboratory results are generally quite good.

19
3.3*2 Problems Reported by Participants Concerning Samples Provided

Most laboratories chose to determine the total tin content of the

research sample rather than to attempt speciation of the molecular moiety

in solution. Two reporting participants claimed that their analysis for

tin in molecular form(s) indicated that the original aqueous tri-nbutyltin research material either contained impurity monobutyl- and

dibutyl-tin species, or that the sample underwent decomposition during

transit and/or storage. These concerns are understandably very significant

because in addition to authenticating sample shelf life, another NBS

concern was to assess whether any or some of the various analytical methods

employed by the participants might actually induce redistribution of the

original tributyltin moiety, possibly occurring in stepwise manner (11,40),

viz. ,

2Bu^Sn +

> Bu2 Sn

2+

+ Bu^Sn (1)

2Bu2 Sn2 + > BuSn3+ + Bu

3

Sn

+ (2)

Most analytical methods cited in the literature (Table 1), affording

chemical speciation of such an organotin mixture suggested by equations 1

and 2, do not provide for analysis of the neutral, often volatile tetraorganotins. Recognizing this need, we have recently extended previous

work employing speciation analysis of aquatic methyl and butyltins (22,36)

to a comprehensive scheme for determination of the complete butyltin

series shown here plus likely methylbutyltin mixed species such as

20
recently reported by others (19). This method utilizes a novel combination

of simultaneous extraction-derivatization by methylene chloride-sodium

borohydride from water followed by direct injection into a gas chromatograph

coupled with a highly sensitive tin-selective flame photometric detector

(GC-FPD), described above in Section 2.2.2.

Applying the improved simultaneous extract ion-hydridizat ion method

with GC-FPD, we have sacrificed nearly 10$ of the original tributyltin

sample stock, selected randomly, in order to assess whether changes had

occurred in stored bottles. In addition to this, we also exposed some

bottles to both conventional laboratory mercury vapor fluorescent lights

and direct sunlight on a South-facing office window sill. To some of the

sample bottles were added small (100 ppm) amounts of acetone, representing

both expected concentrations frequently reported in forming dilute aqueous

solutions of organotins from concentrated organic solutions, and typical

C.| photosenitizers encountered in environmental media (41,42). Regular

stock samples kept in darkness served as controls.

Figure 5 depicts a series of GC-FPD analyses, clearly showing that a

random selection of the NBS sample stock stored for nearly 5 months, about

the midpoint during which participant laboratories were analyzing their

samples, consisted entirely (> 99$) of the aquated tri-n-butyltin cation.

On the other hand, long exposure to direct sunlight (through both window and

Pyrex glass) and laboratory fluorescent light caused decomposition of the

initial Bu^Sn + moiety in some bottles, probably by Sn-C bond scission only

rather than redistribution (equation 1 ) since no tetra-butyltin was detect.ed

(Table 6). After 5 months storage, two bottles received acetone spikes

(100 ppm final concentration), one was stored in sunlight (number 261) and

21
one in darkness (number 265). The dark sample did not show acetone-stimulated decomposition of Bu^Sn* after an additional years' storage (Table 6).

However, exposure of the acetone spiked test bottle to sunlight for 4 months

resulted in decomposition at a more rapid pace. Here di- (4.5# of the total

butyltins), mono- ( 1 . 0% ) and tetrabutyltin (1.0$) species were present,

suggesting that pathways described by equations 1 and 2 are operative.

Samples analyzed after 17 months storage (Table 6) in the dark

underwent only very slight degradation to dibutyltin (ca. 1$). Mass

balances for total tin in the dark-stored bottles gave virtually identical

values (x = 1.10, s = 0.04 ppm) to the NAA values for total tin.

In sum, dark-stored bottles remain extremely stable in terms of total

tin and Bu^Sn + values. Extended storage under fluorescent light or sunlight

resulted in enhanced degradation of tributyltin to other butyltin species in

certain bottles.

We conclude from these results that, while some participants reported

that appreciable "impurity butyltins" or "decomposition" occurred in the

NBS-supplied samples, we have seen no evidence to persuade us that this is

the case. Rather, we feel all analytical methodology, especially that

requiring vigorous extraction/derivatization must be carefully examined for

subtle stoichiometric or catalytic effects - often photoinitiated - which

might induce disproportionation and decomposition reactions at Sn-C bonds.

At NBS, we have been so far unable to detect such alterations in any of the

dark-stored round-robin samples retained and sacrificed at 5 month and 17

month periods for such archival studies, as summarized in Table 6. For this

methods intercomparison, no attempts were made to produce a sterile research

22
material. Viable microorganisms existed in all bottles tested after 5

months storage in the dark. Viable cell counts (on 1/4 strength nutrient

agar, 3 days incubation, 22°C) ranged from 125 to 1195 cells per mL. The

viable cells apparently had little, if any, influence on tributyltin

speciation in these dark stored samples (Table 6).

3.4 Basic Chemistry of the Chromatographic Generator Column

Formation of pure, stable organotins solutions in water is a

notoriously difficult procedure, subject to wide variations in products

and non-reproducible behaviors. Much of the difficulty stems from the

unfamiliar surfactant and lipophilic properties of organotin cations,

strongly dependent upon the number and size of their carbofunctional

groups (43). Notwithstanding their generally low solubilities in water

(typically < 10 ppm), also dependent upon carbon number or size of

covalently bound organic functions (18) the presence of easily dissociable

geganions (anions) can importantly affect both solubilities and stabilities.

In designing our production of large homogeneous batches of pure aquated

tri-n-butyltin cation, we selected an approach derived from our successful

applications of ion exchange chromatography (29). For ease of manipulation

and prepurification of starting material we chose freshly redistilled, neat

liquid bis-( tributyltin) oxide which could be directly injected onto a

suitable chromatographic substrate. The LC column packing selected was an

acid washed, silane treated diatomaceous material, chromosorb W HP of

100/120 mesh size. Consequently, an extensive highly reactive reaction bed

containing both Si-O-Si and Si-OH or Si-0H 2 sites was provided for

equilibration of saturated solutions of Bu^Sn-O-SnBu^ via surface

23
facilitated hydrolysis interactions, as summarized in Figure 6. Such a

cyclic process can be readily maintained because of the great excess of

water and active silica surface area over the Bu^SnOH precursor TBTO, as

the net reaction (Figure 6) reveals.

The induction periods required to produce a LC eluent with constant

Bu^Sr* concentration probably reflect rates of hydrolysis controlled

chiefly by equations B and C in Figure 6.

In sum, the generator column approach to production of both small (mL)

and large (>10 L) homogeneous batches of pure tri-n-butyltin cation in water

has proven effective. Of special note is the likelihood that this chromatographic technique can, in principle (29), be applied to a rather large array

of organotins precursors, both covalent as with liquid TBTO, and solid ionic

compounds such as aryltin halides, for example. Principal limitations will

involve rates of hydrolysis on the reaction flow (column) bed (equations B,

C, Figure 6), flow rates required to generate sufficient quantities, and the

final concentrations to be prepared for each organotin moiety.

5.0 Conclusions

One of the more important findings drawn from this inaugural organotin

measurement methods intercomparison is that a low concentration (ca. 1 ppm)

aqueous organotin research material could be produced with the stability and

chemical purity necessary for a material upon which a methods intercomparison could be based. Prior to the production and subsequent monitoring of

the research material used in this study, the long term fate, in terms of

2H
concentration and chemical species fidelity, of a low concentration

organotin solution was unknown.

The analysis of analytical data generated during this measurement

methods intercomparison demonstrates that any one of the 7 different methods

employed by the participants in this intercomparison can yield accurate

total tin measurement values. The distribution of results does not indicate

a bias inherent in any specific method, but only laboratory to laboratory

variation in the accuracy of total tin determination.

Since this methods intercomparison was initiated, several laboratories

have reported improvements in the detection levels for state-of-art tin

determinations by up to three orders of magnitude. This improved sensitivity now allows detection of organotin compounds at environmental action

level concentrations (ca. ng/L levels) for individual organotin species. It

is therefore clear that a definitive methods intercomparison, designed to

evaluate organotin speciation methodology by use of a multi-species

organotin research material, is both desirable and feasible. Moreover, in

view of increasing international concern with the environmental fate and

effect of organotins, an evaluation of organotin speciation methods is

necessary. Because of the orders of magnitude differences in toxicity

between the individual butyltin compounds, qualified speciation data is an

absolute requirement for accurate assessment of the environmental effects of

organotins and determination of the persistence. Manufacturers may also

find application for certified speciation data in areas of product specification and quality control.

An absolute calibration of the major organotin biocide, tributyltin,

and its known primary degradation product, dibutyltin, is essential to

25
insure that all laboratory and field data are fully supported by calibrated

analyses. This need cannot be met with total tin determinations of a single

species organotin research material. Production of a multi-species

organotin research material with a fixed ratio of di- to tributyltin would

be responsive to real world environmental issues and the measurement needs

of monitoring and regulatory agencies. Based on input from the first

organotin methods intercomparison participants and the limited published

speciation data available at environmental concentrations, a ratio of 2:1 or

greater (Bu^Sn: Bu2 Sn) , at an overall total tin concentration of 200 to

500 ppb, would appear to be an appropriate reflection of field measurement

experience. A research material of this type would provide users with a

useful standard for dilution into either natural saline or freshwater

matricies using dilutions of ca. 10^ to generate samples at environmental

levels of 20 to 50 ng/L.

Production of a multi-species organotin research material will require

NBS to additionally certify, by independent non-destructive means, the total

tin concentration along with the individual species concentrations in the

multi-species research material, thereby insuring total mass balance

agreement in the solution. As mentioned above, a two species organotin

research material is now considered timely and essential, but its generation

raises critical questions concerning the shelf-life and resistance to

degradation by redistribution of the dual-species solution.

Concern about biologically induced redistribution, fortuitously shown

to be no problem in the initial, non-sterile intercomparison sample, must be

reduced by synthesis of a sterile multi-species organotin research material.

Prior to distribution, the multi-species solution would need to be monitored

26
for a suitable period of time (60 to 90 days) to insure there is no sample

redistribution by chemical, catalytic or enzymatic processes exceeding an

acceptable level of approximately

The foregoing research has established the basis for transition of

measurement methodology developed in the research laboratory to qualified

procedures available to users in the manufacturing and monitoring fields.

The measurement methods intercomparison study now concluded makes clear the

feasibility of a more sophisticated speciation methods intercomparison

addressing international concerns of organotin use. We recommend that

effort be directed to the synthesis of a multi-species organotin research

material for use in marine, freshwater, or biotic media.

6.0 Acknowledgments

In conclusion, we would like to thank all the laboratories that

responded to our inquiry as to interest in an organotin measurement methods

intercomparison. Special thanks go to all laboratories that invested time

and resources to make tin determinations of the first intercomparison sample

and return data to NBS. We also thank Cheryl Matthias and Greg Olson for

monitoring the stability of the intercomparison samples.

7.0 References

1. Blunden, S. J. ; Hobbs, L. A.; Smith, P. J. The environmental chemistry

of organotin compounds, in Environmental Chemistry. H. J. M. Bowen,

ed., London: The Royal Society of Chemistry; 1984. p. 49~77.

2. Laughlin, R. B. ; French, W. ; Johannesen, R. B. ; Guard, H. E. ; Brinckman,

F. E. Predictive toxicity using computed molecular topologies: the

example of triorganotin compounds. Chemosphere 13: 575~584; 1984.

27
3. Laughlin, R. B. ; Johannesen, R. B. ; French, W. ; Guard, H. E.

Brinckman, F. E. Structure-activity relationships for organotin

compounds. Environ. Toxicol. Chem. 4: 343 - 351 ; 1985.

4. Lanigan, D.; Weinberg, E. L. The use of estertin stabilizers in PVC,

in organotin compounds: new chemistry and applications, ACS Advances

in Chemistry Series 157. J. J. Zuckerman, ed. Washington, D. C.:

American Chemical Society; 1976.

5. Karpel S. Some novel materials based on polyurethanes. Tin and

Its Uses 132: 14-16; 1982.

6. Smith, P. J. ; Smith, L. Organotin compounds and applications. Chem.

Brit. 1 1 : 208-212; 1975.

7. Cockcroft, R. Evaluating the performance of wood preservatives against

fungi. J. Inst. Wood. Sci. 6: 2-8; 1974.

8. Momtemarano, J. A. ; Dyckman, E. J. Performance of organometallic

polymers as antifouling materials. J. Paint. Technol. 47: 59-61;

1 975.

9. Evans, C. J. ; Smith, P. J. Organotin-based antifouling systems. J.

Oil Col. Chem. Assoc. 58: 160-168; 1975.

10. Gitlitz, M. H. Recent developments in marine antifouling coatings. J.

Coatings Technol. 53: 46-52; 1981.

11. Neumann, W. P. The organic chemistry of tin. New York: Wiley Interscience; 1970. 282 p.

12. Cardwell, R. D. ; Pavlou, S. P. ; Kadeg, R. D. An assessment of the

chemistry environmental chemistry and aquatic toxicology of trialkyltin

compounds. Report prepared for Organotin Environmental Programme

Association (ORTEPA) by Envirosphere Co., Bellevue, WA; 1984. 68 p.

13. Thompson, J. A. J. ; Sheffer, M. G. ; Pierce, R. C.; Chau, Y. K. ; Cooney,

J. J.; Cullen, W. R.; Maguire, R. J. Organotin compounds in the

aquatic environment: scientific criteria for assessing their effects

on environmental quality. National Research Council Canada Publ. NRCC

22494. Ottawa; 1985. 284 p.

14. Department of the Environment, U. K. The control and use of marine

antifouling paints containing organo-tin compounds. Control of

Pollution (anti-fouling paints) Regulations; 1985.

15. Anonymous. The giant oyster stirs a giant controversy. Chem. Eng.

News: 62; 1985 September 30.

16. Federal Register 50: 25748; 1985.

28
17. Laughlin, R. B. ; French, W. J. Comparative study of the acute toxicity

of a homologous series of trialkyltins to larval shore crabs,

Hemigrapsus nudus , and lobster, Homarus americanus . Bull. Environ.

Contam. Toxicol. 25: 802-809; 1980.

18. Craig, P. J. ; Brinckman, F. E. Occurrence and pathways of

organometallic compounds in the environment-general considerations, in

Organometallic Compounds in the Environment. P. J. Craig, ed. Essex,

U. K.: Longman; 1986 (in press), p. 1-64.

19. Maguire, R. J. Butyltin compounds and inorganic tin in sediments in

Ontario. Environ. Sci. Technol. 18: 291-294; 1984.

20. Hodge, V. F. ; Seidel, S. L. ; Goldberg, E. D. Determination of tin (IV)

and organotin compounds in natural waters, coastal sediments and macro

allgae by altomic absorption spectrometry . Anal. Chem. 51: 1256-1259;

1979.

21. Byrd, J. T. ; Andreae, M. 0. Tin and methyltin species in seawater:

concentrations and fluxes. Science 218: 565-569; 1982.

22. Jackson, J. A.; Blair, W. R. ; Brinckman, F. E. ; Iverson, W. P. Gaschromatographic seciation of methylstannanes in the Chesapeake Bay

using purge and trap sampling with a tin-selective detector. Environ.

Sci. Technol. 16: 110-119; 1982.

23. Manders, W. F. ; Olson, G. J. ; Brinckman, F. E. ; Bellama, J. M. A novel

synthesis of methyltin triiodide with environmental implications. J.

Chem. Soc. Chem. Commun. 1984: 538-540; 1984.

24. Rapsomanikis, S.; Weber, J. H. Environmental implications of

methylation of tin(II) and methyltin (IV) ions in the presence of

manganese dioxide. Environ. Sci. Technol. 19: 352-356; 1985.

25. Maguire, R. J. ; Wong, P. T. S. ; Rhamney, J. S. Accumulation and

metabolism of tri-n-butyltin cation by a green alga Ankistrodesmus

falcatus . Can. J. Fish. Aquat. Sci. 41: 537-540; 1984.

26. Barug, D. Microbial degradation of bis ( tr ibutyltin) oxide.

Chemosphere 10: 1145-1154; 1981.

27. Blair, W. R. ; Olson, G. J.; Brinckman, F. E. ; Iverson, W. P. Accumulation and fate of tri-n-butyltin cation in estuarine bacteria.

Microb. Ecol. 8: 241-251; 1982.

28. Alvarez, R. ; Rasberry, S. D.; Uriano, G. A. NBS standard reference

materials: update 1982. Anal. Chem. 54: 1226A-1244A; 1982.

29. Jewett, K. L. ; Brinckman, F. E. Speciation of trace di- and triorganotins in water by ion exchange HPLC-GFAA. J. Chromatogr. Sci.

19: 583-593; 1981.

29
30. Parks, E. J. ; Blair, W. R. ; Brinckman, F. E. GFAA determination of

ultra-trace quantities of organotins in sea water using enhancement

methods. Talanta 32: 633— 639 ; 1985.

31. Brinckman, F. E. ; Blair, W. R. ; Jewett, K. L. ; Iverson, W. P. Application of a liquid chromatograph coupled with a flameless atomic

absorption detector for speciation of trace organometallic compounds.

J. Chromatogr. Sci. 15: 493~503; 1977.

32. Parks, E. J. ; Brinckman, F. E. ; Blair, W. R. Application of a graphite furnace atomic absorption detector automatically coupled to

HPLC for speciation of metal-containing macromolecules. J. Chromatogr.

185: 563-572; 1979.

33* L'vov, B. V. Electrothermal atomization - the way toward absolute

methods of atomic absorption analysis. Spectrochim. Acta 33B: 153~

193; 1978.

34. Jewett, K. L. ; Weiss, C. S. ; Brinckman, F. E. Signal enhancement of

trace organometal compounds speciated by HPLC-GFAA using automated

post-column treatment with transition metal salts. Abstr. Papers,

183rd Amer. Chem. Soc. Nat. Meeting, Las Vegas, NV; April, 1982,

p. ANYL 040.

35. Matthias, C. L. ; Blair, W. R.; Olson, G. J. ; Brinckman, F. E. ; Bellama,

J. M. Quantitation of the complete butyltin sequence in environmental

media employing a new butyltin reference material. Abstr. Papers,

1 89th Amer. Chem. Soc. Nat. Meeting, Miami Beach, FL, April, 1985,

p. ANYL 63.

36. Matthias, C. L. ; Olson, G. J.; Brinckman, F. E.; Bellama, J. M. A comprehensive method for the determination of aquatic butyltin and

methylbutyltin species at ultratrace levels using simultaneous

extraction/hydridization with GC-FPD. Environ. Sci. Technol.,

submitted.

37. Mandel, J.; Paule, R. C. Interlaboratory evaluation of material with

unequal numbers of replicates. Anal. Chem. 42: 1194-1197; 1970, and

correction, Anal. Chem. 43: 1287; 1971.

38. Paule, R. C.; Mandel, J. Consensus values and weighting factors. J. Res. Nat. Bur. Stand. 87: 377-385; 1982.

39. Greenberg, R. R.; Fleming, R. F.; Zeisler, R. High sensitivity neutron

activation analysis of environmental and biological standard reference

materials. Environ. Internat. 10: 129-136; 1984.

40. Brinckman, F. E. Environmental organotin chemistry today: experiences

in the field and laboratory. J. Organometal. Chem. Library 1 2: 3 4

3

— 376; 1981.

41. Westall, J. ; Stumm, W. The hydrosphere, in Handbook of environmental

chemistry, vol. 1, part A, the natural environment and biogeochemical

cycles. 0. Hutzinger, ed. Berlin, Heidelberg, New York: Springer

Verlag; 1980. p. 17-49.

30
42. Williams, P. M. The distribution and cycling of organic matter in the

ocean, chaper 7 in organic compounds in aquatic environments. S. S.

Faust, J. V. Hunter, eds. New York: Marcel Dekker; 1971. p. 1*15-164.

43. Davies, A. G. ; Smith, P. J. Tin in comprehensive organometallic

chemistry, vol 2. G. Wilkinson, F. G. A. Stone, E. W. Abel, eds.

Oxford: Pergamon Press; 1982. p. 519-627.

31

APPENDIX Page 1

October 5, 1983 *^rn &

^ U UNITED STATES D

lyiU * National Buraau of

CTJjr Washington. D.C. B0234

UNITED STATES DEPARTMENT OF COMMERCE

National Buraau of Standard*

The National Bureau of Standards is conducting an interlaboratory comparison

of analytical methods for the measurement of organotin compounds in

aqueous solution. This work Is supported in part by the U.S. Office of

Naval Research (ONR) and is concerned with establishing the variance

between different organotin. measurement methods and providing the basis

for ultimately generating organotin standard reference materials (SRM)

involving relevant environmental matrices such as sea water, sediment,

or tissue. The initial sample will be a tri-n-butyltin compound in

deionized water. Tributyl tin is an organotin species with world-wide

importance in terms of commercial usage and analytical interest.

Because of your well-known interest in organotin compounds, we invite

your participation in the methods intercomparison. A reply form is

included in the enclosure, which we request that you return as soon as possible, whether you plan to participate in the intercomparison or not.

As noted In the enclosure, the identity of the participating laboratories

will be kept confidential. We also invite your use of this sample for

comparison of two or more methods of tin analyses within your laboratory,

i.e., an established speciation method and a new, preliminary method or

a total tin versus a speciated tin method.

Your comments and suggestions concerning this methods intercomparison

are welcomed, please feel free to write me, or telephone (301) 921-2849.

We hope to begin distribution of samples by late October/early November, 1983.

We hope to include your laboratory among those participating in the

intercomparison.

William R. Blair

Chemical & Biodegradation Processes Group

Inorganic Materials Division

Rm. A329/Bldg. 223

National Bureau of Standards

Washington, DC 20234 U.S. A.

s i nrprpl

v

Enclosure
APPENDIX I Page 2

In ter laboratory Comparison of Measurement Methods

for Trace Organotin Compounds in Water

OBJECTIVES

A series of aqueous organotin solutions are being prepared at the National

Bureau of Standards (NBS) for use in an interlaboratory comparison of

total and/or organotin measurement methods. NBS has been asked by the

U.S. Office of Naval Research (ONR) to provide samples and coordinate

data tabulation fcs part of an ongoing NBS program investigating the

environmental fate and effect of organotins. Considerable interest in

the intercomparison has been expressed by laboratories conducting organotin

research around the world. Consequently, we decided to invite participation by all interested laboratories, with more than 20 participants

expected.

Initially, a tributyltin-x compound in deionized water will be distributed

for analysis by the method(s) currently in use at each laboratory.

Ultimately, a similar sample using a sea water and possibly a sediment

matrix will also be provided for analysis. It is hoped that this inaugural

intercomparison will indicate the variance of current analysis methods,

resulting in identification or development of an internationally recognized

standard analytical method(s) for the determination and speciation of

organotins in aquatic media.

SAMPLE PREPARATION AT NBS

The tributyltin-x samples will be supplied in new clear borosilicate glass

bottles with Teflon-lined caps. A comparison between glass and polycarbonate

container materials is contemplated, but initial samples will be supplied

in glass bottles only. Prior to use, the bottles will be rinsed with an organic solvent (methanol) to remove manufacturing residues, then leached

for 15 to 18 hours with aqueous 10 percent HNO 3 at 40 °C to remove any

trace metal contamination. The tributyltin-x solution will be prepared

in a single batch of six to eight liters by on-line dilution of a saturated,

aqueous, solution of tributvl tin-x delivered through a thermostated

chromatographic column (1-3). The preparation, storage, and dispensing

of the tributyltin-x solution will be done under an N 2 atmosphere. A

sufficient number of samples will be prepared so that in case of loss or damage to a sample during shipping, a maximum of one duplicate can be

provided. Control samples, maintained at NBS, will be stored both under

normal laboratory lighting conditions and in the dark. The total tin

concentration of the sample will be stated only as a nominal value to

prevent overload of analytical instrument detectors. Anticipated sample

size is 100 ml, with a total tin concentration in the low part-permillion (pg/mL) range.

INDIVIDUAL LABORATORY PARTICIPATION

Your request to participate in the intercomparison of measurements will

indicate agreement to report sample analysis within 30 days of receipt

of the sample and to report the following information based on determination

of either speciated tin or total tin or both:

ii
APPENDIX I Page 3

(1) Values for eight replicate analyses of the sample. A replicate

analysis is here defined as a separate aliquot taken individually

for analysis from the original bottle containing the tin solution

supplied by MBS. Do not send averages or standard deviation values,

the eight individual measurements will be used to calculate averages

and standard deviation values, and to evaluate bias and random

errors in reported results.

(2) Concise despription(s) of method(s) used for sample analysis.

Rather than tryto provide several samples at different concentrations,

only one sample will be provided. The concentration should be high

enough to prevent significant losses during storage and shipping. Upon

receipt, samples must be stored in the dark at a temperature of 20 to

22 °C. Prior to analysis the sample will need to be diluted to protect

most tin-selective detectors. We recommend a dilution of at least

1000:1 to more realistically approximate environmental concentrations.

The identity of the individual laboratories participating in the intercomparison

will be kept confidential, with each lab knowing only its own coded

identity symbol.

COLLECTION OF DATA

Data collection, reduction, tabulation, and plotting will be handled by

a statistical analysis group at NBS, with the results of the intercomparison being mailed to participants as soon as all data are reported

and processed.

ANALYSIS OF RESULTS

The data received from each participant will be compiled into a table

indicating the variance between methods. The concentration of tin in

the sample will be determined at NBS by neutron activation analysis.

This value will be supplied with the results mailed to each participant

so the accuracy of the method used may be determined.

References

(1) Schwarz, F. P., Anal. Chem. 52, 10 (1980).

(2) Schwarz, F. P. , and Miller, J., Anal. Chem. 52, 2162 (1980).

(3) May, W. E. , Wasik, S. P., and Freeman, D. H. , Anal. Chem. 50, 175

(1978).

ill
APPENDIX I Page 4

INTERLABORATORY ORGANOTIN SPECIATION STUDY

PARTICIPANT INFORMATION

Please complete and return this sheet as soon as possible to:

Mr. William R. Blair

Rm. A331/B1 dg . 223 (Materials)

, National Bureau of Standards

Washington, DC 20234 USA

Tel. (301) 921-2849

We wish to participate in the organotin interlaboratory comparison.

We do not wish to participate.

Signed:

For those participating:

(1) We will submit analytical data to Mr. William R. Blair within

weeks (fill in blank) of receiving the sample.

(2) We will measure speciated tin

total tin

both of the above

(3) Summary (1 to 2 sentences) of analytical method(s) to be used

for measurement(s) specified in (2) above:

(Give literature reference if appropriate.)

(4)

Name and address for shipment of sample:

(5)

Name and address (if different from 4) for person(s) conducting

analysis.

iv
Appendix II

Report of Analysis of Tributlytin Solutions for Total Tin Content by

Neutron Activation Analysis

D. A. Becker

Inorganic Analytical Research Division

Center for Analytical Chemistry

Four samples were received in tightly capped, foil covered bottles

with the numbers 174, 214, 25 *1 , and 262. Samples were analyzed as

received.

Procedure: After several gentle inversions of the bottle, sample

solutions were poured directly into precleaned, weighed 2 dram

polyethylene vials, which were again weighed to determine sample weight.

Vials were then immediately sealed with a hot soldering iron, packaged as

required in the irradiation capsule, and immediately irradiated in the NBS

Reactor (NBSR) for analysis.

Standards were made from NBS SRM 1057b, Dibutyltin bis

(2-ethylhexanoate) . After drying, a standard solution of this matrial in

paraffin oil was made, having a concentration of 335.9 pg Sn/g oil. For

working standards, a weighed amount of the stock solution was diluted with

pure paraffin oil inside of the 2 dram vial used for that irradiation.

Amounts of tin in each standard ranged from approximately 30-90 pg.

Samples and standards were each analyzed individually according to

the following procedure: irradiation for 2 minutes in the RT-3 pneumatic

tube facility of the NBSR (neutron flux is 4.9 x lO 1 ^ n/cm2 s); decay time

v
of 9 minutes during which the samples (standards) in the 2 dram vials were

mixed by repeated inversion and positioned on a high resolution germanium

semi-conductor detector; samples were then counted for 1200 seconds clock

time, and the 332 key peak of Sn-125 m (Ti/2 = 9.52 m) was used for the

determination of total tin.

Results and Discussion: Results of this analysis are shown in Table

1 . All four bottles were analyzed at least once, and two were analyzed in

duplicate. Agreement is good, providing a total tin concentration in the

sample solutions of 1.06 ± 0.05 ug/g. The relative standard deviation

(Is) of the analysis was 4.4 percent.

It should be noted that a separate evaluation of the possible matrix

effects due to differing hydrogen content of water versus paraffin oil was

made, and showed no detectable effect. Also, both samples and standards

were irradiated and counted in the horizontal position, which effectively

eliminated errors due to geometry differences from differing sample sizes.

Blank values for the clean polyethylene vials plus pure paraffin oil were

found to be negligible. In addition, the agreement between data values

obtained on 16-17 May and on 21 August may indicate that these solutions

as delivered are stable over this period of time.

vi
Table 1 for Appendix II

Table 1 . Results from Tin Analysis

Bottle Number Sample Weight (g) Tin Concentration (ug/g)

174 7.3611 1 .09

174a 5.7468 1 .06

214 7.2932 1 .07

254 7.7043 0.99

262 7.4438 1 .02

262a 5.9272 1 .12

MEAN

STD. DEV. (1 s;n~1

)

STD. DEV. (relative)

1 .06

0.047

4.4 percent

a These samples were analyzed on 21 August 1984. All others were analyzed

on 1 6-1 7 May, 1984.
TABLE 1

SOME SPECIATION METHODS IN CURRENT USE FOR ORGANOTINS

(Substrate(s)

)

Der ivatization,

Preconcentration

Separation

Scheme

Detector ( s)

Employed

Tin Species;

Method Detn.

Limits, yg/mL

Refs

DIRECT SOLVENT EXTRACTION

(B) benzene, reflux none NMR,XRF,GFAA Oct 2 Sn; 40 1 (T) HC1 + hexane GC H-FID RjjSn ( R=Et

,

Pr , Bu ) ; 100 2

(T) RjjNOH + total organic

toluene none GFAA inorg. Sn 1

(M) MeOH + HC1 MeOH/hexane GFAA Bu Sn, n=2,3; 12 on alumina < 0.2

DIRECT HYDRIDIZATION

(M) sparge w/ or w/o Me

n

Sn, n=0-4;

NaBHjj GC FPD 0.01 3-0.053 3 on Tenax-GC Bu

nSn, n=1 , 2

0.018-0.037, n=1 ,2;

PhSn ; 0.023

(T) direct sparge GC MS Me

n

Sn, n=1-4; 10

w/ homogenate > 1 ng/g

EXTRACTION WITH HYDRIDIZATION

(W) CHC1 2 extr

,

Ph

n

Sn, n=1 -4

Li AlH^/hexane GC EC, FID 3-15 4

EXTRACTION WITH ALKYLATION

(W) benzene/tropolone Me

nSn, n=0~3; 5

extr + BuMgBr GC FAA 0.04 w/5 L water

(W) benzene/tropolone Bu

n Sn, n=0-3;

extr + PeMgBr GC FPD 0.060-0.150 6

COMPLEXOMETRIC/SPECTROPHOTOMETRIC

(W) 3,4-dithiol satd LC w/NaOH + UV at Sn(IV)

7

polyurethane acetone 650 nm 0.04

(M) silica gel TLC w/ GFAA of R

n

Sn, n=1 -38 w/ MeOH-HOAc hexane-HOAc spots air, 0.1 yg/rrP

waters, 100 yg/L

soils, 1 yg/g

MISCELLANEOUS

(W) direct cation ex- GFAA Rn

Sn, n=1 ,2 9

injection change HPLC R=alkyl, aryl;

25-150

NOTES FOR TABLE 1 Matrix speciated: (B) = beverage; (W) = natural waters; (T) = tissues;

(M) = mixed matrices, air, water, sediments, dusts.
REFERENCES FOR TABLE 1

1

.

J-C. Meranger, M A rapid screening method for the determination of

di(n-octyl) tin stabilizers in alcoholic beverages, using a heated

graphite analyzer," J. Assoc. Off. Anal. Chem., 58, 1143 (1975).

2. Y. Arakawa, 0. Wada, T. H. Yu, and H. Iwai, "Rapid method for the

determination of tetraalkyltin compounds in various kinds of biological

material by gas chromatography," J. Chromatogr . , 207, 237 (1981).

3. J. A. Jackson, W. R. Blair, F. E. Brinckman, and W. P. Iverson,

"Gas-chromatographic speciation of methylstannanes in the Chesapeake Bay

using purge and trap sampling with a tin-selective detector," Environ.

Sci. Technol., 1 6, 110 (1982).

4.

C. J. Soderquist and D. G. Crosby, "Determination of triphenyltin

hydroxide and its degradation products in water," Anal. Chem. , 50, 1435

(1978).

5. Y. K. Chau, P. T. S. Wong, and G. A. Bengert, "Determination of

Methyltin( IV) species in water by gas chromatography/atomic absorpiton

spectrophotometry," Anal. Chem., 54 , 246 (1982).

6. R. J. Maquire and H. Huneault, "Determination of butyltin species in

water by gas chromatography with flame photometric detection," J.

Chromatogr. , 209 , 458 (1981).

7. M. Omar and H. J. M. Bowen, "Pre-concentration of environmental tin

and its determination using catechol violet," Analyst, 107 , 654 (1982).

8. C. J. Riggle, D. L. Sgontz, and A. P. Graffeo, "The analysis of

organotins in the environment," Proceedings, 4th Joint Conference on Sensing of Environmental Pollutants, American Chemical Society,

Washington, D. C. (1978), pp. 761-764.

9. K. L. Jewett and F. E. Brinckman, "Speciation of tace di- and

triorganotins in water by ion-exchange HPLC-GFAA", J. Chromatogr. Sci.,

19, 583 (1981).

10. J. C. Means and K. L. Hulebak, "A methology for speciation of

organotins in mammalian tissues, Neurotoxlcol.

,

, xxx (1982).

11. H. L. Trachman, A. J. Tyberg, and P. D. Branigan, "Atomic absorption

spectrometric determination of sub-part-per-million quantities of tin in

extracts and biological lmaterials with a graphite furnace," Anal. Chem.,

49, 1090 (1977).

12. S. Kojima, "Separation of organotin compounds by using the difference

in partition behavior between hexane and methanolic buffer solution,"

Analyst, 104, 660 (1979).
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D3 D3D3DD DDX
USA

North

Carolina

Department

of

Natural

P.0.

Box

27687

Dr.

R.E.

Kelling

Resources

and

Community

Development

Raleigh,

North

Carolina

27611-7687 c0

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LABORATORY

RESULTS

OF

TIN

DETERMINATIONS

GROUPED

BY

METHOD

OF

ANALYSIS

(A-G)

VALUES

IN

PPM

TOTAL

TIN

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TABLE 5

Analytical Method Averages and Standard Deviations

Method

Total Tin

mg/L (ppm)

Average

Std. Dev.

from the

Average

Number

of

Laboratories

A 0.962 0.277 3

B 0.974 0.087 13

C 1 .055 0.018 3

D 0.898 0.125 3

E 1.185 0.189 4

F 0.976 0.042 2

G 0.935 0.048 4
TABLE 6

STABILITY OF ORGANOTIN RESEARCH MATERIAL

Analysis after 5 months of storage

Bottle #

Storage

Condition

% organotin species detected;

BugSn

++ BugSn

-1 BuSn+ + + nd = not detected

BU)|Sn

177 lab light 1 trace 1 .0 99 nd

206 lab light nd 0.6 99.4 nd

261 sunlight nd 1 .2 98.8 nd

267 sunlight 0.8 4.4 94.8 nd

152 dark nd 0.7 99.3 nd

162 dark nd nd 100 nd

258 dark nd nd 100 nd

265 dark nd nd 100 nd

167 dark nd nd 100 nd

Analysis after 17 months of storage, conditions as above

GFAA

TOTAL

TIN

177 3.4 4.0 92.6 nd 1.55

206

261*

nd 0.9

not speciated

99.1 nd 1 .43

1.14

267 not speciated 0.87

152 nd 2.5 97.5 nd 1 .12

162 nd 0.7 99.3 nd 1 .15

258 nd 0.4 99.6 nd 1 .05

265* nd 0.7 99.3 nd 1 .05

167 nd 1 .6 98.4 nd 1 .13

Laboratory fluorescent

Sunlight coming through

lights

south facing office window and pyrex sample bottle

* Samples receiving 100 ppm addition of acetone, after analysis of 5 months of

storage. Bottle 261 after 9 months contained 93.5 t Bu^Sn +

, 4.5$ Bu2 Sn

2+

, 1$ each of BuSn^ +

, Bu^Sn.
Figure Captions

Figure 1 . The effect of different container materials on the short term

48 hour) stability of aqueous inorganic and tributyltin solutions with an

initial concentration of 30 ppb (30 pg/L). A dramatic loss of solution

strength is seen with the tributyltin solution stored in a polyethylene

container, demonstrating the unsuitability of polyethylene for storage of

organotin reference solutions or samples containing organotin compounds.

Figure 2. Addition of 0.01 M citric acid to 30 ppb (30 pg/L) aqueous

solutions of inorganic and tributyltin stored in polyethylene containers

results in stabilization of the solutions, presumably by reducing adsorption

losses to the container walls.

Figure 3- Schematic diagram of the chromatographic generator column

apparatus used for synthesis of the tributyltin research material

distributed during this methods intercomparison.

Figure 4. Frequency diagram of the results of analysis of the tributyltin

research material by intercomparison participants. The total number of

participants was 32. The analytical methods used (A to G) , are located above

a concentration scale indicating the distribution of values determined. The

results tend to be evenly distributed about the center (1.0 ppm) point.
Figure 5. Analysis by GC-FPD of the contents of some of the intercomparison

samples retained at NBS and opened after 137 days of dark storage at 22°C.

Nine bottles altogether were opened and analyzed and all gave virtually

identical results. Sample 267 was analyzed with spikes of mono-, di-, and

tetrabutyltin species at levels which would represent 6 % degradation of the

tributyltin to each particular species (top chromatogram).

Figure 6. Schematic representation of the reactions occurring on the

generator column during tributyltin solution synthesis.
us 6u

HOURS

ELAPSED
Polyethylene

Bottle

ope "

,=

0.01 M

CITRIC

ACID

symbol

boiled H20•&0=

Bu3

Sn +

us 6u

HOURS
Figure 3
Total Tin ( |jg/ m L)

Figure 4
5 1 I 10 1 5 min

Figure 5
GENERATOR COLUMN SYNTHESIS OF ORGANOTINS

!

>Si-0-Si< H,0

//// )//)////

>Si-OH >Si-OH

/)/////)////

R >Si-OH + Bu 3 Sn-0-SnBu 3 n),u

>SI-0-SnBu 3 + Bu 3 Sn-OH

/)////

c Si-0-SnBu 3 + H 2 0 /W >SI-OH + Bu 3 Sn-OH

/)/////

NET REACTION:

Si-O-Si + 2 H 2 0 + Bu 3 Sn-0-SnBu 3 — 2 Si-OH + 2 Bu 3 Sn-OH

Figure 6
NBS-114A (REV. 2-80

U.S. DEPT. OF COMM.

BIBLIOGRAPHIC DATA

1. PUBLICATION OR

REPORT NO.

2. Performing Organ. Report No. 3. Publication Date

SHEET (See instructions) NBSIR 86-3321 FEBRUARY 1986

4. TITLE AND SUBTITLE

AN INTERNATIONAL BUTYLTIN MEASUREMENT METHODS INTERCOMPARISON: SAMPLE PREPARATION

AND RESULTS OF ANALYSES

5. AUTHOR(S)

W. R. Blair, G. J. Olson, F. E. Brinckman, R. C. Paule, and D. A. Becker

6. PERFORMING ORGANIZATION (If joint or other than NBS, see instructions)

national bureau of standards

DEPARTMENT OF COMMERCE

WASHINGTON, D.C. 20234

7. Contract/Grant No.

8. Type of Report & Period Covered

Interagency FY84-FY85

9. SPONSORING ORGANIZATION NAME AND COMPLETE ADDRESS (Street. City, State. ZIP)

Office of Naval Research, Code 441

800 North Quincy Street

Arlington, VA 22217

10. SUPPLEMENTARY NOTES

J Document describes a computer program; SF-185, FIPS Software Summary, is attached.

11. ABSTRACT (A 200-word or less factual summary of most significant information. If document includes a significant

bi bl iography or literature survey, mention it here)

A comparison of prevalent organotin measurement methods has been conducted on an international scale with a new tri-n-butyltin research material distributed to over 40 participating laboratories worldwide. A description of background research

into the behavior and manipulation of low-concentration (ppm) aqueous organotin

solutions, chromatographic production and packaging of the stable speciated

butyltin research material in water, and quantitative results from the international

methods intercomparison are reported here along with recommendations for future work.

12. KEY WORDS (Six to twelve entries ; alphabetical order; capitalize only proper names; and separate key words bv semicolon s) Chemical speciation; Liquid chromatography ; Methods intercomparison; Molecular

characterization; Research material; Round-robin; Stability; Tributyltin; Organotin

solutions.

13. AVAILABILITY 14. NO. OF

PRINTED PAGES

Unlimited

| | For Official Distribution. Do Not Release to NTIS

[~

] Order From Superintendent of Documents, U.S. Government Printing Office, Washington, D.C.

20402. 15. Price

lX I O r<^ er From National T echnical Information Service (NTIS), Springfield, VA. 22161 $ 11.95

USCOMM-DC 004 s-p 90