Solid Phase Extraction of Organophosphorus Pesticides and Triazine Herbicides in Water Using a New Polymeric Sorbent

This application describes a solid phase extraction (SPE) method for EPA method 8141B analytes, including organophosphorus compounds, and triazine herbicides in water. Target analytes are extracted onto Styre Screen® HL DVB polymeric sorbent from water samples at neutral pH. Proper sample pH is critical for good analyte recoveries as organophosphorus esters hydrolyze under acidic or basic conditions. The retained analytes are eluted with acetone and dichloromethane (DCM), the eluate is then dried, concentrated, and exchanged into n-hexane or 1:1 acetone:n-hexane if a loss of polar analytes occurs.

SPE Procedure

a) Adjust 1 L (or less) water sample to pH 7.

b) Connect sample transfer tubes to the top of the SPE cartridges (ECHLD156) and attach the cartridges to a SPE manifold.

c) Wash the SPE cartridges with 3 × 5 mL DCM, condition with 2 × 5 mL methanol, and equilibrate with 2 × 5 mL DI water.

d) Insert the stainless steel ends of the transfer tubes into the sample containers, and draw the entire sample through the SPE cartridge at a fast drop-wise fashion (about 15 mL/min).

e) Remove the transfer tubes from the SPE cartridges, and dry the cartridges under full vacuum for 10 min.

f) Insert collection vials into the manifold for eluate collection.

g) Rinse the sample bottles with 5 mL acetone and, using the transfer tubes, slowly draw the rinsates through the SPE cartridges. Repeat with 10 mL DCM.

h) Remove the transfer tubes from the SPE cartridges. Continue the elution with 5 mL DCM.

i) Dry the eluates with 10–15 g anhydrous sodium sulfate (ECSS25K) held in 15 mL reservoirs (RFV1F15P) or glass funnels with glass wool.

j) Rinse the collection vials with 2 × 5 mL DCM, pass the rinses through the sodium sulfate and collect.

k) Concentrate the dried eluates to about 0.5 mL under a gentle stream of nitrogen at 40 °C.

l) Rinse the surface of the eluate containers with 3 mL n-hexane; continue concentrating to 2 mL.

m) Adjust the final volume to 2 mL with n-hexane. Add internalstandards. The samples are ready for GC analysis.

Table I: SPE materials

Instrumental

GC–MS: Agilent 6890N GC with 5975C MSD Injector: 250 °C Injection Vol.: 2 µL

GC column: Restek Rxi® -5sil MS 30 m × 0.25 mm, 0.25 µm, integrated with 10-m guard column

Carrier gas: Helium at a constant flow of 1.2 mL/min

Oven: Initial temperature at 60 °C, hold for 1 min; ramp at 10 °C/min to 300 °C, hold for 2

Tune: dftpp.u

Full Scan: 45–450 amu

Results

Table II: Accuracy and precision data

Conclusion

Excellent recoveries ranging from 85.5% to 120% and relative standard deviations of less than 7.3% were obtained using UCT's new Styre Screen® HL DVB polymeric sorbent (ECHLD156) for the extraction of EPA 8141B analytes in water.

UCT, LLC

2731 Bartram Road, Bristol, PA 19007

tel. (800) 385-3153; Email: methods@unitedchem.com

Website: www.unitedchem.com