UNITED STATES ENVIRONMENTAL PROTECTION AGENCY 

WASHINGTON, D.C. 20460 

MEMORANDUM 

OFFICE OF 

WATER 

SUBJECT: Modifications to Metho 

FROM: 

TO: 

DATE: 

Richard Reding, Chief 

Engineering & Analyti 

Quality Assurance Managers 

A TP Coordinators 

NPDES Coordinators 

January 16, 2009 

As a follow up to my "Flexibility to Modify CWA Methods" memorandum of November 

20,2007, Lem Walker has participated in conference calls and other outreach with our 

regional and state colleagues regarding modifications to Part 136 methods, including 

EP A Method 1664A, which determines oil and grease, a method-defined parameter. We 

have received many questions and suggestions about interpreting a user's current 

flexibility to modify Part 136 chemical analytical method without prior review or 

rulemaking Qy the EPA. This flexibility is embodied in the quality assurance/control 

(QAlQC) section of 1664A and other1600-series methods. This memorandum answers 

several questions about allowed modifications to Method 1664A. You may use it when 

aUditing a laboratory or fielding inquiries about allowed modifications to Method 1664A. 

Although analyst modifications to method-defined parameter methods are generally not 

allowed, some changes are acceptable. These modifications are described in general 

terms in the Scope and Application Section of 1664A: 

1. 7 The laboratory is permitted to modify the method to overcome 

interferences or lower the cost of measurements, provided that all 

performance criteria in this method are met. The requirements for 

establishing method equivalency are given in Sections 9.1.2 and 9.2.3. 

1.8 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. 

Changes to the chemistry of the method, the determinative step (e.g., the detector), the 

quality control, or those not expressly permitted in 1664A are not allowed. This memo 

describes several modifications that are within the flexibility of 1664A, a solvent change 

that is not allowed, and a special modification approved only in one EPA region. 

We appreciate your continued collaborative and cooperative approach to helping us 

implement the flexibility to modify Part 136 chemical methods. Please contact Lem 

Walker, if you have any questions or suggestions about the following examples. As we 

Internet Address (URL) • hllp:llwww.epa.gov 

Recycled/Recyclable. Printed with Vegetable Oil Based Inks on 100% Postconsumer, Process Chlorine Free Recycled Paper 
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gain more experience we will continue to update, as needed, via memoranda or updates to 

the Q&As at our CWA website http://www.epa.gov/waterscience/methods/. 

Questions and Answers Concerning EPA Method 1664A 

Allowable Modifications to EPA Method 1664A for Oil and Grease 

1. PAR Standard 

Question: May we spike samples at lower concentrations instead of 40 mg/L per 

the method? 

Answer: It is allowable to use a lower PAR (Precision and Recovery) standard 

concentration such as 20 mg/L when spiking matrix samples provided the 

concentration of the spike is (a) greater than the background concentration, (b) less 

than or equal to the regulatory compliance level, and c) all quality control 

requirements of the test are achieved. 

2. SPE Filters/Prefilters 

Question: Our lab uses 47mm diameter SPE Filters to analyze blanks, QC tests 

and effluents and only uses 90mm diameter SPE Filters to analyze complex 

samples containing particulates and other substances. Is this OK? 

Answer: All SPE (Solid Phase Extraction) filters used in the analytical batch should 

be of the same diameter and from the same manufacturer or brand (ideally the same 

lot number) as this may affect the chemistry and Quality Control of EPA Method 

1664A. Use of optional prefilters for specific samples are allowed as described in 

§11.3.5 of Method 1664A which allows use of techniques to complete the phase 

separation when dealing with LLE emulsions. 

3. Smaller Sample Size 

Question: Please confirm that it is allowable to collect and analyze a smaller 

volume of sample as long as we express our final results as mg/L? 

Answer: Per EPA Method 1664A Sections 1.7, 4.5, 6.1.1 Note, 8.1.2, 11.0 Note and 

11.2.2, collection of a smaller sample is permitted and is an allowable change 

provided all the quality control requirements of sections 9.1.2, 9.2.3 are met as well 

as sections 9.3 and 9.4, matrix spikes and blanks respectively. 

4. Alternate Concentration Techniques – Aluminum Pans – Beakers 

Question: In the past with the old method, we concentrated our Oil and Grease 

extracts using beakers. Can we do the same with the new method? 

Answer: Per EPA Method 1664A Section 9.1.2, alternate concentration techniques 

are permitted and include the use of aluminum pans or beakers with evaporation 

and/or distillation to aid concentration of the sample. 

5. Acidification of Sample 

Question: If analysis of the samples or QC tests will occur within 4 hours, do we 

still have to acidify them to pH < 2? 

Answer: All samples must be acidified and/or verified in the lab to pH<2 

immediately prior to analysis. If analysis is to be delayed for more than four hours, it 

is acceptable to adjust the sample pH to less than 2.5 with HCl or H2SO4 solution 

(Section 7.2) at the time of collection and refrigerate to 0-6°C (40 CFR 136, Table II). 
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6. Matrix Spike Requirements 

Question: The matrix spike requirements in the method seem complicated and 

appear as if they will be very burdensome for our lab. Can you please 

recommend simple, equally acceptable guideline that we can follow? 

Answer: As a practical means of ensuring compliance with the matrix spike 

frequency requirement, perform the following steps for a given discharge/waste 

stream (See matrix type definitions – 40 CFR Parts 400-699): 

1. Analyze at least one aliquot out of each analytical batch (up to 20 samples) 

from each site or discharge/waste stream per Method 1664A Section 9.3.2. 

2. The laboratory should randomly choose and rotate through each site or 

discharge/waste stream for the matrix spike until every site or discharge/waste 

stream has been used as the matrix spike at least once. 

3. Repeat and continue steps 1 and 2 above as needed. 

7. Balance Calibration 

Question: All of our other gravimetric methods specify use of a calibration 

weight greater than the expected value. Shouldn’t this method be similar? 

Answer: Use at least an additional upper limit (and possibly a lower) balance 

calibration weight to bracket the expected final weight values. This action should 

help improve data quality, but there is not any requirement for the laboratory to do it. 

Unacceptable Modifications to EPA Method 1664A 

Alternate Solvents 

Question: I’ve been told to pre-rinse my emptied sample bottle with methanol to 

remove the residual water so the subsequent hexane extractions can more 

efficiently remove any oil and grease adhering to the walls. Is this allowed? 

Answer: Based on the results of two Freon Replacement Studies, co-solvents and/or 

alternate solvents (including methanol) can significantly change the chemistry of 

Method 1664A. Thus, use of co-solvents or alternate solvents is not allowed because 

the chemistry of the method has been changed. 

Limited Use Modifications to EPA Method 1664A – Region 8 

Sulfur – Thiosulfate-Inflated HEM Results 

Question: May we report results using modified Method 1664 “Cu” even though 

our lab is not in or regulated by EPA Region 8? 

Answer: No. To address sulfur interference, a modified method (Method 1664 “Cu”) 

uses nitric acid-activated copper coils to remove sulfur from the hexane extract of 

produced water samples. This sulfur removal step occurs immediately prior to 

distillation of the solvent. EPA Region 8 has approved, only for use in Region 8, 

analysis of these “produced” water samples provided the discharger can initially 

demonstrate the presence of sulfur interference. Use of this modified method in other 

EPA Regions requires submitting a limited-use ATP application to the Region for 

approval.