Posted: March 26, 2009
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.
