Horizon 1664 Compliance Options
The following is excerpted from an email from Lemuel Walker, USEPA CWA ATP Coordinator, dated Friday, April 10, 2009 to Barbara Escobar of the State Assessor's Teleconference Group regarding compliance options for Horizon® SPE-DEX® 1000/3000 users when employing alternate solvents.
Information on Oil and Grease discussed during Monday's State Assessors call. Please forward.
As you know, 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:
- The methanol rinse is immediately discarded to waste.
- 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 emtanol will collocate or be collected with the n-hexane extractions.
- And, it is the laboratory's responsibility to demonstrate and document the appropriate operating conditions (1&2) above to allow this use of methanol.
Given this, the use of methanol to condition the SPE filter or rinsing bottles with another solvent is allowed provided that solvent is sent to waste and not collocated or collected into the collection vessel with the final n-Hexane elution.
To get back into compliance with EPA Method 1664 A, Horizon users may:
For relatively clean samples without sediment build-up on the SPE filter:
- A user should use only hexane and manually enter a new method into the Horizon controller in which methanol is not used after the air dry step. An example of such is provided in the 3M®-Horizon® protocol link below:
For samples with significant sediment build-up on the SPE filter/prefilter:
- Use an equivalent hexane-only method as above and try to optimize the loperating conditions such as air dry time, hexane dispnese volume, soak times and vacuum free air flow to improve potentially low MS/MSD recoveries for specific samples. Users may also try different SPE filters, prefilters and filtration aids to help prevent build-up of the sediment layer and its subsequent air flow restriction which can lead to the low recoveries. In addition, drying agents like magnesium sulfate, sodium sulfate and other means may be added to the sediment layer to help remove residual water from the trapped solids.
- Evaluate the suitability of methanol exception methods with current Horizon equipment. Initial conditions for such methodw that take a 50:50% v/v methanol:water solution immediately to waste after the air dry step can be entered into the Horizon Controller as a new method (1-20) and are available from Xenosep at:
- Users may also purchase the Controller updgrades from Horizon which may eliminate the collection flask change requried aaove with current Horizon equipment. (In which I can not give an opinion at this tijme whether or not this modification meets the methanol exception requirements.)
- However, I would suggest testing methods/disks/prefilters and drying agents from different vendors and demonstrate the method you select will meet EPA 1664 A requirements in your current Horizon equipment before investing in any upgrades if appropriate.
- Please also note that some samples may not be amenable to processing by SPE technology at this time and may have to be processed by the reference LLE method.
Xenosep Technologies set-up conditions for these options may also be viewed by selecting the navigation links below:
Option 1: Hexane only
Option 2: MeOH to waste
Option 3: MeOH with pause