Chromatography Forum

dear friends

in our lab we analize water samples for PAH's following EPA 8310 and EPA 610, but we are confused beacuse in EPA 610 the sample must be analised before 7 days and the extract can be stored for 40 days, however in EPA 8310 there is no time to analize the sample and the extract can be stored 40 days too.

which have your experience been in this matter??, do you analize the sample before 7 days or the sample has stability enough to be analised it over 7 days???

thanks a lot and best regards

The 8000-series methods contain a lot of references, and usually don't have all the details of the extraction process and quality control requirements in them, but they do have references to the guidance methods that do contain the relevant information.


From 8310:

7.1 Extraction:
7.1.1 Refer to Chapter Two for guidance on choosing the appropriate extraction procedure. In general, water samples are extracted at a neutral pH with methylene chloride, using either Method 3510 or 3520. Solid samples are extracted using either Method 3540 or 3550. To achieve maximum sensitivity with this method, the extract must be concentrated to 1 mL.


From 3520C:

8.0 QUALITY CONTROL
8.2 Refer to Chapter One for specific quality control procedures and Method 3500 for extraction and sample-preparation procedures.


From 3500C:

8.0 SAMPLE COLLECTION, PRESERVATION, AND STORAGE
See the introductory material to Chapter Four, "Organic Analytes," and the specific methods to be employed.


And finally, in SW-846, Chapter Four, "Organic Analytes", see Table 4-1.

http://www.epa.gov/osw/hazard/testmetho ... /chap4.pdf

That table shows the standard 7/40 holding times.


Please, anyone out there, correct me if I'm wrong.

oscareiden,

I believe what you are mixing up is extraction holding times and analytical holding times. Back in the day when I did this type of work, you had seven days (for example) to extract the sample, get the analytes into solvent. You then had 40 days from that point in which to complete the analysis, that is run the samples to the point of being able to report them.

I hope this clarifies.

Best regards.