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3
ExtractionMethods forLiquid,Solid, andBiotaSamples
All of thepesticide compounds listed inTable I, except theUSEPA8151herbi-
cides, are extractedunderneutral conditionsusinga varietyof organic solvents.
There are several sample extractionmethods that canbe applied, but themost
commonwill be addressedhere.
Liquid Samples
For liquid samples, you can use either separatory funnel extraction (US EPA
Method 3510) or automated liquid-liquid extraction (US EPAMethod 3520).
In comparison, separatory funnel extraction is faster and less expensive to set
up, but requires continuousattention. Automated liquid-liquid extractors can
operate unattended, but are more expensive. For some methods, if analyte
recovery is lower than allowed, youmust re-extract the sample by separatory
funnel. Alternatively, if the sample forms an emulsion to the degree that ac-
ceptable solvent recovery isnot possibleusinga separatory funnel, then some
methods require liquid-liquid extraction.
According toUSEPAMethod 3535, solid phase extraction (SPE) can be used
to extract pesticide compounds from aqueous samples.
Separatory Funnel Extraction
For separatory funnel extraction, measure up to 1L of sample into a 2L
separatory funnel, and check the pH. Adjust the pH to neutral using hydro-
chloric acid or sodium hydroxide, depending on the starting pH. Avoid using
sulfuric acid (see
SulfuricAcidCleanup
onpage8). If adjustment isnecessary,
record on your sample tracking paperwork.
Extract the sample by adding 60mL of dichloromethane and shaking for two
minutes. It is critical to shakeall samples in the samemanner or youmay see
variations in extraction efficiency—the best way to ensure consistency is to
use a mechanical separatory funnel shaker. The dichloromethane settles to
the bottom of the separatory funnel and then is decanted through a sodium
sulfate tube into a collection vessel such as a Kuderna-Danish (KD) concen-
trator or intoaTurboVap
®
orRapidVap
®
container if usingautomated concen-
trators. This step is repeated twomore times to achieve quantitative recovery
of all analytes (collect all three extractions into the same collection vessel).
Table I, cont.
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Use SPE (USEPAMethod
3535), separatory funnel
extraction (USEPAMethod
3510), or automated
liquid-liquidextraction
(USEPAMethod3520)
for liquid samples.
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acidfluorfen
bentazon
chloramben
2,4-D
dalapon
2,4-DB
DCAA
US EPA 8151 (herbicides)
DCPA
dicamba
3,5-dichlorobenzoic acid
dichloroprop
dinoseb
MCPA
MCPP
4-nitrophenol
pentachlorophenol
picloram
2,4,5-T
2,4,5-TP (Silvex)
alachlor
atrazine
cyanozine
US EPA 8081 Additional Compounds
metalachlor
metribuzin
pentachloronitrobenzene
simazine
2,4-DA (herbicide)
Common Surrogates
decachlorobiphenyl
2,4,5,6-tetrachloro-m-xylene
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