Large-volume liquid chromatographic trace-enrichment system for environmental analysis,

The fully automated on-line trace enrichment of 27 (polar) pollutants, using volumes of up to 1,000 mL, on a polymeric precolumn followed by liquid chromatography - diode-array detection has been studied. Various parameters influencing the reproducibility of these large volume injections like breakthrough volume, precolumn capacity, matrix effects, and enrichment flow rate are discussed. The relative standard deviation of the recoveries after enrichment of 25-500 mL of sample is 1-20 %. Enrichment flow rates up to 15 mL mi

Integrated systems for on-line gas and liquid chromatography with a single mass spectrometric detector for the automated analysis of environmental samples.

An integrated system has been developed which combines liquid (LC) and gas (GC) chromatographic separation with a single mass spectrometer (MS). On-line solid-phase extraction (SPE) of 10-200 ml aqueous samples on a short (10 x 2.0 mm I.D.) precolumn packed with a styrene-divinylbenzene copolymer is used for analyte enrichment. The trace-enrichment procedure was automated by means of a PROSPEKT cartridge-exchange/ solvent-selection/valve-switching unit. After sample loading, the precolumn is eluted on-line in two subsequent runs, first onto the GC-MS system and, next, onto the LC-MS system using a particle beam (PB) interface. Prior to entering the PB-MS, the LC eluent passes through the flow cell of a UV diode-array detector (DAD). Both GO-MS and LC-PB-MS generate classical electron ionisation (EI) and chemical ionisation (CI) spectra which are useful for the identification of low- and sub-μg/l concentrations of environmental pollutants covering a wide polarity and volatility range. The LC-DAD data provide additional means for quantitation and yield complementary spectral information, All three detection systems (GC-MS, LC-DAD, LC-PB-MS) and the trace-enrichment procedure are fully automated and controlled from the keyboard of the central computer. With such a 'MULTIANALYSIS' system GC-MS, LC-DAD and LC-MS data of the same sample can be obtained within 3 h. The system was optimised with nine chlorinated pesticides in drinking water as test mixture. With 100-ml samples detection limits in GO-MS were 0.0005-0.03 μg/l, and in LC-PB-MS 0.5-7 μg/l, both in the full-scan (EI) mode. Negative chemical ionisation (NCI) with methane as reagent gas improved the sensitivity of six halogenated compounds 3- to 30-fold and provided relevant information for structural elucidation of unknown compounds in real-world samples. LC-DAD detection limits varied from 0.01 to 0.05 μg/l. Relative standard deviations (R.S.D.) of retention times were less than 0.2% in all systems, R.S.D.s of peak areas were 5-15% for GC-MS and LC-PB-MS and less than 5% for LC-DAD. The 'MULTIANALYSIS' system was used to analyse surface water samples and river sediment extracts; several pollutants were detected and identified

Solid-phase extraction of polar pesticides from environmental water samples on graphitized carbon and Empore-activated carbon disks and on-line coupling to octadecyl-bonded silica analytical columns.

The suitability of Empore-activated carbon disks (EACD), Envi-Carb graphitized carbon black (GCB) and CPP-50 graphitized carbon for the trace enrichment of polar pesticides from water samples was studied by means of off-line and on-line solid-phase extraction (SPE). In the off-line procedure, 0.5-2 l samples spiked with a test mixture of oxamyl, methomyl and aldicarb sulfoxide were enriched on EnviCarb SPE cartridges or 47 mm diameter EACD and eluted with dichloromethane-methanol. After evaporation, a sample was injected onto a

Monitoring of organic micropollutants in surface water by automated on-line trace-enrichment liquid an gas chromatographic systems with ultraviolet diode-array and mass spectrometric detection.

The pollution of the Nitra river (Slovakia), a left-bank tributary of the river Danube, by organic microcontaminants was monitored in 1993 and 1994. Water samples were taken at six sites every two months, transported in a portable refrigerator and processed in the Netherlands. From among five systems tested for their suitability to analyse the samples, solid-phase extraction (SPE)-LC-diode-array detection (DAD UV), SPE-LC-particle beam (PB)-MS and SPE-GC-MS, were selected for regular monitoring. At a later stage SPE-LC-DAD UV and SPE-LC-PB-MS were integrated in one system. The three systems used similar SPE procedures for trace enrichment coupled on-line to LC and GC set-ups. Each method was fully automated by means of an automated cartridge exchange, solvent selection and valve-switching unit, and SPE/WIN software. On-line analysis of 10-200-ml samples allowed the determination of low- to sub-μg