Low-Level Determination of Organochlorine Pesticides in Wines by Automatic Preconcentration and GC–MS–MS Detection

Levels and patterns of DDTs in maternal colostrum from an island population and exposure of neonates

Dichlorodiphenyltrichloroethane (DDT) was heavily used in the past in many regions of the world. The occurrence of DDTs in island populations may be elevated if the island is adjacent to major DDT consumption estuaries, such as the Yangtze River Delta. In this study, colostrum samples were collected from maternal-neonate pairs (n = 106) from the Shengsi Island, located directly downstream from the Yangtze River outlet. DDT isomers and enantiomer compositions were analyzed by gas chromatography equipped with mass spectrometer (GC/MS) and GC/MS-MS. The average levels of p,p'-DDE, o,p'-DDD, p,p'-DDD, o,p'-DDT, p,p'-DDT and total DDTs were 1.32, 0.03, 0.09, 0.08, 0.48, and 1.93 μg g(-1) lipid weight, respectively. Maternal age and pregnancy body mass index (BMI) were positively associated with levels of DDTs (p < 0.05). High (DDE+DDD)/DDT and p,p'-DDE/p,p'-DDT ratios suggested that current DDT residues originated primarily from historical use of DDT products, but new sources may also contribute partially to some high o,p'-DDT/p,p'-DDT ratios. Enantiomeric enrichment was found for the (-)-enantiomer of o,p'-DDD and the (+)-enantiomer of o,p'-DDT, suggesting stereoselective attenuation. Based on breast milk consumption, the average daily intake of DDTs by neonates was 8.33 ± 7.34 μg kg(-1)bw per day, which exceeded the WHO's tolerable daily intake guideline of 0.01 mg kg(-1) bw per day by 25%, implying some neonates in the Yangtze River region are potentially at high risk from exposure to DDTs.

Investigation on the Gas-phase decomposition of trichlorfon by GC-MS and theoretical calculation

The gas phase pyrolysis of trichlorfon was investigated by the on-line gas chromatography – mass spectrometry (GC-MS) pyrolysis and theoretical calculations. Two reaction channels were proposed in the pyrolytic reaction, by analyzing the detected pyrolytic products in the total ion chromatography, including 2,2,2-trichloroacetaldehyde, dimethyl phosphite, and dichlorvos. Theoretical calculations showed that there is an intramolecular hydrogen bond between the hydroxyl group and the phosphate O atom in trichlorfon, through which the hydroxyl H atom can be easily transferred to phosphate O atom to trigger two pyrolytic channels. In path-a, migration of H atom results in direct decomposition of trichlorfon to give 2,2,2-trichloroacetaldehyde and dimethyl phosphite in one step. In path-b, migration of H atom in trichlorfon is combined with formation of the O-P bond to give an intermediate, followed by HCl elimination to afford dichlorvos. Path-a is kinetically more favorable than path-b, which is consistent with the GC-MS results.