Analysis of organochloro-pesticides in Eritrean water and sediment samples

[摘要] ENGLISH ABSTRACT: The choice of the sample preparation technique used in combination with achromatographic technique in environmental analysis strongly influences theperformance of the method as a whole. The main aim of this work was to evaluatemethods like: micro liquid-liquid extraction (цLLE)and solid phase micro extraction(SPME) in combination with gas chromatography-electron capture detector (GCECD)and a recently developed technique named stir bar sorptive extraction (SBSE)combined with thermal desorption system-programmable temperature vaporizationgaschromatography-mass spectrometer (TDS-PTV-GC-MS) for the analysis oforganochloro-pesticides (OCPs) in natural water and to make a comparison betweenthem. The most suitable method was then selected for the analysis of water samplescollected from Eritrea. An additional goal was to develop a sensitive method for theanalysis ofOCPs in soil and sediment samples.цLLE-GC-ECD and SPME-GC-ECD methods were evaluated for the analysis ofOCPs in water. The former allowed achieving a sensitivity of less than 100 ppt andthe latter was able to detect down to the 1 ppt level. Both methods were found to berepeatable with %RSD of3% to 19% and 5% to 12% as well as linear with a range of1:103 and 1:5x103 respectivey. SBSE-TDS-GC-MS was also investigated for theanalysis of OCPs in water samples. With this technique a good sensitivity down to 1ppt was also obtained. The less sensitive nature of the MS compared to ECD washereby compensated for by the large amount of polydimethylsiloxane (PDMS) phaseon the stir bar. The method was repeatable and linear with a range of 1:5000, which issimilar to the one obtained for the SPME-GC-ECD method. All three methods werealso tested with real contaminated water samples and a comparison of the threetechniques in terms of sensitivity, linearity, repeatability, availability and costeffectiveness was done. As a method of choice in terms of the above criteria, SPMEGC-ECD was applied to the water samples collected from Eritrea. The presence ofsome oePs such as a-BBC (benzenehexachloride), heptachlor, heptachlor epoxide,endosulfan I, p,p'-DDE (dichlorodiphenylchloroethylene), endosulfan II, p,p'-DDD(dichlorodiphenyldichloroethane), endosu!fan sulfate and p,p'-DDT(dichlorodiphenyltrichloroethane) in some of the Eritrean water samples wasdemonstrated The SPME-GC-ECD technique for the analysis OCPs in soil and sediment sampleswas investigated. It was shown to be able to detect down to 1 pg/g (lppt) with goodlinearity and repeatability. The method was also evaluated for authentic soil samples.Due to a lack of time the method could not be applied for the analysis of the soil andsediment samples collected from Eritrea.

[发布机构] Stellenbosch University