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1664 Method Modification

Complying with the Modifications to EPA Method 1664A Using Horizon Technology Automated Extraction Systems

On January 16, 2009, the US EPA released information regarding Modifications to Method 1664A. You can access the EPA memorandum referencing these modifications by visiting: http://www.epa.gov/waterscience/methods/method/oil/1664a-mod.html

Horizon Technology has several options available to your laboratory in order to ensure that you are in compliance with these modifications. Please be aware that some information being circulated by some O&G vendors is misleading and incorrect. The information contained here was obtained by direct conversations and e-mails with Dr. Dick Reding and Lemuel Walker of the US EPA.

The following information should help to clarify the ruling.

Method 1664A was promulgated in May 1999. Why are these modifications being made now?
It has been reported that regional EPA auditors were finding various sample preparation techniques being used for the extraction of O&G samples. The variations seemed to cover both LLE and SPE procedures and seemed to cover a wide range of variations. In an effort to remove confusion, add guidance, and more clearly identify the user's current flexibility to modify the method 1664A, the EPA released their January 16, 2009 memorandum. The memorandum addresses the following topics as Allowable Modifications; PAR Standard, SPE Filters/Prefilters, Smaller Sample Sizes, Alternate Concentration Techniques, Acidification of Sample, Matrix Spike Requirements, and Balance Calibration. The memorandum also addressed Unacceptable Modifications to the Method 1664A, and a Limited Use Modification to Method 1664A, specific to Region 8. See the document for details.

One "Unacceptable Modification to EPA Method 1664A" is the use of co-solvents and/or alternate solvents. Why is this?
One variation the regional EPA auditors found was that people performing SPE were using a variety of solvents to rinse the sample bottle and the SPE disk. While Method 1664A was written as a LLE technique, and was very specific in the sample preparation procedure to be followed, the exact SPE methodology was never included in the written method. It was omitted because SPE was a new technology; and it was determined that the SPE procedure should not be tied to a specific written procedure, that could not be deviated from. The main driver for this action was the fact that there have been previous cases where prescriptive EPA methods have been written and promulgated, but eventually shown not to be properly optimized to ensure good chemistry. However, once a prescriptive method is promulgated, it cannot be changed, which can create a major problem for analytical labs.

With regards to EPA Method 1664A, which was moving towards the performance based approach of method development, it was felt that as long as the MDL, IPR, and OPR requirements of the method were met, the SPE procedure should be able to be optimized, as long as the data quality objectives of the method were met. When the EPA auditors began to find various solvents and techniques being used, they referred back to the written 1664A method, a LLE technique, and made the decision that only n-hexane can be the extracting solvent. Therefore, the January 16th document stated that the "use of CO-solvents or alternate solvents is not allowed because the chemistry of the method has been changed."

How will this modification of disallowing co-solvent impact the recovery values of my O&G samples?
For those doing SPE extractions, it is well known that the optimal approach for maximum extraction efficiency is to rinse the SPE disk with a water soluble solvent, after the water sample has been filtered through the disk. This is important for several reasons.

1. If the residual water left in the pore structure of the SPE disk is not first removed, then any non-polar solvent, such as n-hexane, cannot effectively extract the compounds from the SPE disk, in this case the O&G fraction, which will result in low and inconsistent recoveries. Therefore, all proper SPE methods require a water soluble solvent as a rinse.

2. Using a water soluble solvent as a rinse, removes all residual water still trapped on the inner walls of the sample bottle. Again, removing the residual water from the sample bottle allows the n-hexane to effectively remove the compounds of interest.

3. It has been proven that if excessive air dry times are used to remove the residual water within the pore structure of the SPE disk, that the lighter end of the O&G compounds can be easily volatilized. This volatilization will result in low and inconsistent recoveries. (Request a copy of this study from Horizon)

Due to these issues, and the fact that Horizon Technology has continuously focused on optimized chemistry to achieve the best recovery values, the recommendation of using a water soluble solvent as a rinse has been used for all of the automated extractor systems we provide.

To check the possibly adverse impact of the EPA modifications, Horizon Technology conducted studies using POTW samples with only n-hexane as the extracting rinse solvent, and found a loss of 42.1%, as compared to the results when using a water soluble solvent, such as methanol, as a rinse. Additionally, the properly optimized SPE procedure with a methanol rinse, very closed matched the standard LLE technique. (Request a copy of this study from Horizon Technology).

What has Horizon Technology been doing to address this disallowance of co-solvents if the recoveries will be adversely impacted?
The Horizon Technology Customer Support Group has received many calls from concerned SPE-DEX users regarding what to do, and how to implement these method modifications in their laboratories, using their Horizon Technology automated extraction systems and products. Since the EPA announcement, Robert Johnson, Founder and CEO of Horizon Technology, has been in communication with Dr. Richard Reding, Chief, U.S. EPA, and Lemuel Walker, Jr., Clean Water Act ATP Coordinator, US EPA to explain the requirements for proper SPE techniques and to find a mutually suitable solution.

If recovery values can be adversely effected, what is the latest word from the US EPA on the use of CO-solvents and/or alternate solvents?
On March 24, 2009, Lemuel Walker, Jr., from the EPA stated in an email to Robert Johnson... "Oil and Grease is a method-defined analyte and use of any CO-solvents, alternate solvents or any substance that can introduce the target analyte into the final extract is not allowed per 40 CFR Part 136.6. However, a methanol rinse may be allowed to remove water residual if:

1. The methanol rinse is immediately discarded to waste.

2. The SPE filter is sufficiently air dried with vacuum to remove any traces of methanol remaining in the SPE filter so as to ensure that no methanol will collocate or be collected with the n-hexane extractions.

3. And, it is the laboratory's responsibility to demonstrate and document the appropriate operating conditions (1 and 2) above to allow this use of methanol.

Given this, the use of methanol to condition the SPE filter or rinsing bottles is allowed provided that the methanol is sent to waste and not collected into the collection vessel with the final n-hexane elution."

How do these modifications impact the use of my automated SPE systems and what do I need to do now?
In order to be in compliance with the January 16, 2009 EPA memorandum, several options are available from Horizon Technology. Our automated SPE products continue to ensure the most reliable and consistent testing for EPA Method 1664A. Our highly qualified team of technical representatives are on hand to assist you in selecting the best solution to suit your laboratory. Email us at info@horizontechinc.com or call our Customer Support Group at 1-603-893-3663 ext: 640 or 633 today, to discuss the option that best fits your current situation.

At Horizon Technology we are fully committed to your success with EPA Method 1664A. If you have any questions, please don't hesitate to contact us.

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