Matrix-Enhanced Degradation of p,p‘-DDT during Gas Chromatographic Analysis:  A Consideration

Abstract

Analysis of p,p‘-DDT in environmental samples requires monitoring the GC-derived breakdown of this insecticide, which produces p,p‘-DDD and/or p,p‘-DDE, both also primary environmental degradation products. A performance evaluation standard (PES) containing p,p‘-DDT but not p,p‘-DDD or p,p‘-DDE can be injected at regular intervals throughout an analytical sequence to monitor GC degradation. Some U.S. EPA methods limit GC breakdown of DDT in the PES to ≤20%. GC/MS analysis of large-volume natural water samples fortified with deuterium- and 13C-labeled p,p‘-DDT exhibited up to 65% DDT breakdown by the GC inlet. These matrix-enhanced GC degradation amounts substantially exceeded the <20% breakdown levels indicated by bracketing injections of the PES containing unlabeled and labeled DDT. Substantial matrix-enhanced GC degradation was not observed during analysis of a limited number of fractionated bed-sediment extracts containing labeled DDT. Use of isotopically labeled DDT seems to provide an effective tool for monitoring sample-specific DDT breakdown during GC/MS analysis. However, analyte co-elutions render impractical their use in GC/ECD analysis. The oc currence of matrix-enhanced GC degradation might have important implications on data quality and the resultant interpretations of the environmental degradation of DDT and other thermolabile contaminants.

Methods of analysis by the U.S. Geological Survey National Water Quality Laboratory-A method supplement for the determination of Fipronil and degradates in water by gas chromatography/mass spectrometry

“…This effect is more apparent at lower concentrations than higher concentrations (table 4). Other GC methods note degradation in the injection port and the need for required maintenance and quality-control samples for other compounds (Foreman, 1997;Munch, 1995). ----1 Laboratory 1 used a liquid chromatography tandem mass spectrometry analytical method.…”

Efficiency Evaluation of Extraction Methods for Analysis of OCPs and PCBs in Soils of Varying TOC

“…With a longer extraction period (16 hours) or the use of Soxhlet extraction the apparent recovery of the DDX increases drastically to levels above 100%. This increase is attributed to analyte decomposition [30] and matrix enhancement effects [31] in the GC liner. This is reasonable as a Judging from the data obtained during this study PCBs do not seem to be a point of concern during SLE from soils.…”

A Multisection Passive Sampler for Measuring Sediment Porewater Profile of Dichlorodiphenyltrichloroethane and Its Metabolites

“…Before instrumental analysis, the extent for breakdown of p,p′-DDT was less than 20% through the analysis of a standard solution of p,p′-DDT. 31 ■ RESULTS AND DISCUSSION Measurement of Sampling Rate (R). The sampling rate (R) can be expressed as (Text S4 of the Supporting Information )…”