Headspace solid-phase microextraction with on-fiber derivatization for the determination of aldehydes in algae by gas chromatography-mass spectrometry.

A simple, fast, sensitive and cost-effective method based on headspace solid-phase microextraction (HS-SPME) with on-fiber derivatization coupled with gas chromatography-mass spectrometry was developed for the determination of six typical aldehydes, 2E-hexenal, heptanal, 2E-heptenal, 2E,4E-heptadienal, 2E-decenal and 2E,4E-decadienal in laboratory algae cultures. As derivatization reagent, O-2,3,4,5,6-(pentafluorobenzyl) hydroxylamine hydrochloride, was loaded onto the poly(dimethylsiloxane)/divinylbenzene fiber for aldehydes on-fiber derivatization prior to HS-SPME. Various influence factors of extraction efficiency were systematically investigated. Under optimized extraction conditions, excellent method performances for all the six aldehydes were attained, such as satisfactory extraction recoveries ranging from 67.1 to 117%, with the precision (relative standard deviation) within 5.3-11.1%, and low detection limits in the range of 0.026-0.044 µg/L. The validated method was successfully applied for the analysis of the aldehydes in two diatoms (Skeletonema costatum and Chaetoceros muelleri), two pyrrophytas (Prorocentrum micans and Scrippsiella trochoidea) and Calanus sinicus eggs (feeding on the two diatoms above).

Determination of organophosphorus pesticides in underground water by SPE-GC-MS.

A rapid and effective method is developed for the determination of organophosphorus pesticides (dichlorovos, methyl parathion, malathion, and parathion) in underground water by solid-phase extraction (SPE)-gas chromatography-mass spectrometry. Some important extraction parameters including types of SPE adsorbents, elution solvents, and injection volume of water samples are optimized. The use of Cleanert-PEP polymer SPE column improved higher extraction efficiencies than the C18 SPE column commonly used. Water samples are extracted using Cleanert-PEP as SPE adsorbent and ethyl acetate as elution solvent. Precision values expressed as relative standard deviation for 1 microg/L of spiked water sample are in the range of 1.6-4.0%. Dichlorvos, methyl parathion, malathion, and parathion are linear in the range of 0.1-1.0 microg/L (r2=0.9976), 0.1-2.0 microg/L (r2=0.9883), 0.1-2.0 microg/L (r2=0.9798), and 0.055-1.1 microg/L (r2=0.9790), respectively. The limits of detection for spiked water samples are in the range of 4-10 ng/L. The optimized method is applied to the determination of underground water samples. Recoveries are between 59.5% and 94.6% for spiked underground water samples. The benefit of the method developed is rapid, simple, and has good repeatability.