Thesis (MSc)--Stellenbosch University, 2004. / ENGLISH ABSTRACT: The choice of the sample preparation technique used in combination with a
chromatographic technique in environmental analysis strongly influences the
performance of the method as a whole. The main aim of this work was to evaluate
methods 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 vaporizationgas
chromatography-mass spectrometer (TDS-PTV-GC-MS) for the analysis of
organochloro-pesticides (OCPs) in natural water and to make a comparison between
them. The most suitable method was then selected for the analysis of water samples
collected from Eritrea. An additional goal was to develop a sensitive method for the
analysis ofOCPs in soil and sediment samples. цLLE-GC-ECD and SPME-GC-ECD methods were evaluated for the analysis of
OCPs in water. The former allowed achieving a sensitivity of less than 100 ppt and
the latter was able to detect down to the 1 ppt level. Both methods were found to be
repeatable with %RSD of3% to 19% and 5% to 12% as well as linear with a range of
1:103 and 1:5x103 respectivey. SBSE-TDS-GC-MS was also investigated for the
analysis of OCPs in water samples. With this technique a good sensitivity down to 1
ppt was also obtained. The less sensitive nature of the MS compared to ECD was
hereby compensated for by the large amount of polydimethylsiloxane (PDMS) phase
on the stir bar. The method was repeatable and linear with a range of 1:5000, which is
similar to the one obtained for the SPME-GC-ECD method. All three methods were
also tested with real contaminated water samples and a comparison of the three
techniques in terms of sensitivity, linearity, repeatability, availability and cost
effectiveness 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 of
some 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 was
demonstrated The SPME-GC-ECD technique for the analysis OCPs in soil and sediment samples
was investigated. It was shown to be able to detect down to 1 pg/g (lppt) with good
linearity 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 and
sediment samples collected from Eritrea. / AFRIKAANSE OPSOMMING: Die keuse van 'n gepaste monster-voorbereidingsmetode wat gebruik word tesame
met 'n chromatografiese skeidingtegniek in omgewings-analise het 'n beduidende
effek op die algehele metode. Die doel van hierdie werk was om metodes soos mikrovloeistof-
vloeistof ekstraksie (цLLE) en soliede fase mikro ekstraksie (SPME) in
kombinasie met gaschromatografie met elektronvangs deteksie (GC-ECD) te
ontwikkel vir die analise van organochloor-pestisiede (OCPs) in natuurlike water.
Vervolgens is hierdie metodes vergelyk met die onlangs-ontwikkelde roerstaaf
sorptiewe ekstraksie tegniek (SBSE) in kombinasie met termiese desorbsie-GCmassaspektrometriese
deteksie (TDS-GC-MSD). Die mees geskikte metode is
vervolgens gebruik vir die analise van Eritreaanse watermonsters. Daarbenewens was
die doelook om 'n sensitiewe metode te ontwikkel vir die analise van OCPs in gronden
sedimentmonsters.
Beide цLLE en SPME-GC-ECD metodes is gekarakteriseer deur goeie
herhaalbaarheid en lineariteit. Die sensitiwiteit van bogenoemde metodes was minder
as 100 dele per triljoen (ppt) en 1 ppt, respektiewelik. Ook met SBSE-TDS-GC-MSD
kon 'n deteksielimiet van 1 ppt bereik word. In hierdie geval is vir die verlies van
sensitiwiteit van die MSD in vergelyking met die ECD, gekompenseer deur die groter
hoeveelheid PDMS op die roerstaaf in vergelyking met 'n SPME apparaat. Die
herhaalbaarheid en lineariteit van die metode is vergelykbaar met dié van die SPMEGC-
ECD metode.
Al drie metodes is vergelyk vir die analise van gekontamineerde watermonsters in
terme van sensitiwiteit, liniêre bereik, herhaalbaarheid, toeganklikheid en kosteeffektiwiteit.
SPME-GC-ECD is vervolgens gekies as metode van voorkeur vir die
analise van Eritreaanse watermonsters. Die teenwoordigheid van sekere OCPs soos
a-BHC, heptachloor, heptachloorepoksied, endosulfan I, p,p'-DDE, endosulfan II,
p,p' -DDD, endosulfan sulfaat en p,p' -DDT in die monsters is gedemonstreer.
Die toepasbaarheid van die SPME-GC-ECD metode vir die analise van OCPs in
grond-en sedimentmonsters is ook geëvalueer, en dit was moontlik om so min as 1
pg/g waar te neem. Weens tydbeperkings was dit nie moontlik om Eritreaanse
grondmonsters met die ontwikkelde metode te analiseer nie.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:sun/oai:scholar.sun.ac.za:10019.1/49830 |
| Date | 12 1900 |
| Creators | Weldegergis, Berhane Tekle |
| Contributors | Sandra, P. J. F., Stellenbosch University. Faculty of Science. Dept. of Chemistry & Polymer Science. |
| Publisher | Stellenbosch : Stellenbosch University |
| Source Sets | South African National ETD Portal |
| Language | en_ZA |
| Detected Language | English |
| Type | Thesis |
| Format | 103 p. : ill. |
| Rights | Stellenbosch University |
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