P. de Voogt, E.A.J. Bleeker, P.L.A. van Vlaardingen, A. Fernandez, J. Slobodnik, H. Wever, M.H.S. Kraak, Formation and identification of azaarene transformation products from aquatic invertebrate and algal metabolism, J. Chromatogr. B, 724 (1999) 265 – 274.
Abstract: The metabolism of two azaarenes, viz. acridine and phenanthridine, by aquatic organisms was studied in short-term and chronic laboratory tests. The identity of metabolites observed in the test waters was investigated with different analytical methods, including HPLC, GC and hyphenated LC- or GC-MS. The Zebra mussel (Dreissena polymorpha), one green alga species (Selenastrum capricornutum) and periphyton or bacteria transformed acridine into 9[10H]-acridinone. Phenanthridine was transformed into 5[6H]-phenanthridinone by midge (Chironomus riparius) larvae. The findings indicate that closely related isomers may undergo species-specific biotransformation. It was concluded that keto-metabolites are major products in the aquatic fate of benzoquinolines, which may be overlooked in the risk assessment of parent compounds. This study illustrates the typical problems with, as well as the potency of, chromatographic methods in the elucidation of metabolic routes of organic contaminants. (C) 1999 Elsevier Science B.V. All rights reserved.
J. Slobodník, H. Lingeman, U. A. Th. Brinkman, Large-volume liquid chromatographic trace-enrichment system for environmental analysis, Chromatographia 07/1999; 50(3):141-149.
Abstract: 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 min−1 can be used with an optimum at 10 mL min−1. A pore size of 300 A provides the best results using the polymeric PLRP-S material. The breakthrough volumes show significant dependence upon the concentration of the analytes in the sample.
P. Oswald, J. Krupčík, I. Špánik, E. Benická, P. Daučík, The determination of petroleum hydrocarbons in environmental samples by capillary gas chromatography, Chem. Listy 93, (1999) 628-632.
J. Slobodník, A.J.H. Louter, J.J. Vreuls, I. Liška and U.A.Th. Brinkman, Monitoring of organic micropollutants in surface water by automated on-line trace-enrichment liquid and gas chromatographic systems with ultraviolet diode-array and mass spectrometric detection, J. Chromatogr. A, 768 (1997) 239.
Abstract: 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 software. On-line analysis of 10–200-ml samples allowed the determination of low- to sub-μg l−1 levels of numerous pollutants. Relative standard deviations (R.S.D.) of the retention times were 0.1–0.9% for each system. R.S.D. values of peak areas were 1–15% for SPE-LC-DAD UV, 10–16% for SPE-GC-MS and 17–31% for SPE-LC-PB-MS. The three techniques were found to be complementary. No significant maintenance problems occurred during the project. More than 500 compounds frequently appeared in the sample chromatograms; about 30% could be identified by at least one technique. The majority were industrial pollutants, hydrocarbons, aliphatic alcohols, substituted phenols, sulphur-, nitrogen-, oxygen-, phosphorus- and chlorine-containing compounds, pesticides and their degradation products.
Author Keywords: Water analysis; Environmental analysis; Detection, LC; Detection, GC; Extraction methods; Pesticides.
J. Slobodník, A.J.H. Louter, A.C. Hogenboom and U.A.Th. Brinkman, Integrated system for on-line gas and liquid chromatography with a single mass spectrometric detector for the automated analysis of environmental samples, J. Chromatogr. A, 1996, 730 (1996) 353.
Abstract: 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 × 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 GC-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 GC-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.
Author Keywords: Environmental analysis; Water analysis; Automation; Liquid chromatography-mass spectrometry; Gas chromatography-mass spectrometry Pesticides.
A.J.H. Louter, C.A. van Beekvelt, P. Cid Montanes, J. Slobodnik, J.J. Vreuls, U.A.Th. Brinkman, Analysis of microcontaminants in aqueous samples by fully automated on-line solid-phase extraction-gas chromatography-mass selective detection, Journal of Chromatography A, 725 (1996) 67-83.
Abstract: The trace-level analysis of unknown organic pollutants in water requires the use of fast and sensitive methods which also provide structural information. In the present study, an on-line technique was used which combines sample preparation by means of solid-phase extraction (SPE) on a small precolumn packed with a hydrophobic phase, and capillary gas chromatography (GC) with mass spectrometric (MS) detection. Sample preparation was carried out in a fully automated SPE module which was connected to the GC system via an on-column interface. The on-column interface was selected because of its wide application range. The mass spectrometer was preferably used in the full-scan acquisition mode because of the intended identification. The total system including the SPE module, was controlled by the MS software which allowed unattended analysis of a series of samples.The feasibility of on-line SPE-GC-MS was demonstrated by analysing a variety of surface water samples in order to detect and identify non-target compounds. With a sample volume of only 10 ml various micropollutants could be identified, and also quantified, at levels below 0.1 μg/l. The system proved to be flexible, and the sample preparation could easily be adapted to analyse organochlorine pesticides by adding 30 vol.% of methanol to the raw sample. Samples were taken from several European (Axios, Greece; Ebro, Spain; Meuse, Netherlands; Nitra, Slovakia; Rhine, Germany; Thames, UK; Varta, Poland) and American (Sacramento, USA; Amazon, Brazil) rivers. An example of the identification of unknown microcontaminants in waste water is also presented, which is further evidence of the robustness and flexibility of the SPE-GC-MS analyzer.
Keywords: Water analysis; Automation; Environmental analysis; Solid-phase extraction; Sample preparation; Pesticides.
I. Liška and J. Slobodník, Comparison of gas and liquid chromatography for analysing polar pesticides in water samples, review, J. Chromatogr. A, 733 (1996) 235.
Abstract: This review describes the applications of gas chromatography (GC) and liquid chromatography (LC) in the analysis of selected groups of pesticides in water. The attention is focused on the most popular (in terms of amounts produced and applied) pesticide classes, i.e., carbamates, phenylureas, triazines, phenoxy acetic acid derivatives and chlorinated phenols. The use of GC and LC for the analysis of these compounds in water samples in the past and at present is reviewed separately for each group. Sample concentration and detection techniques are discussed in relation to their influence on the performance of the particular separation technique. Special attention is given to mass spectrometry (MS) because it is the most intensively developed detection technique in environmental analysis. The potential of another novel approach - large volume injections into the GC - is discussed separately. Methods using GC or LC coupled to an appropriate detector and using suitable sample handling procedures provide detection limits typically in the range of 0.001–1 ppb. At these levels, target or unknown compounds can be determined/identified by means of their retention and spectral characteristics. Principally, most of the analytes can be determined by both techniques, however, GC methods, when applicable, still have the advantages of great separation efficiency, high speed of analysis and the availability of a wide range of highly sensitive detectors; on the other hand, LC is often a method of choice when polar, non-volatile or thermolabile compounds are to be analyzed. Neither of the two separation techniques reviewed seems to have an overall priority in environmental analysis of pesticides. They can be considered as complementary.
Author Keywords: Reviews; Water analysis; Environmental analysis; Pesticides.
J. Slobodník, Ö. Öztezkizian, H. Lingeman and U.A.Th. Brinkman, 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, J. Chromatogr. A, 750 (1996) 227.
Abstract: 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 1 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 C18-bonded silica column and analysed by liquid chromatography with ultraviolet (LC-UV) detection. EACD performed better than EnviCarb cartridges in terms of breakthrough volumes (>2 1 for all test analytes), reproducibility (R.S.D. of recoveries, 4–8%, n=3) and sampling speed (100 ml/min); detection limits in drinking water were 0.05–0.16 μg/l. In the on-line experiments, 4.6 mm diameter pieces cut from original EACD and stacked onto each other in a 9 mm long precolumn, and EnviCarb and CPP-50 packed in 10×2.0 mm I.D. precolumn, were tested, and 50–200 ml spiked water samples were preconcentrated. Because of the peak broadening caused by the strong sorption of the analytes on carbon, the carbon-packed precolumns were eluted by a separate stream of 0.1 ml/min acetonitrile which was mixed with the gradient LC eluent in front of the C18 analytical column. The final on-line procedure was also applied for the less polar propoxur, carbaryl and methiocarb. EnviCarb could not be used due to its poor pressure resistance. CPP-50 provided less peak broadening than EACD: peak widths were 0.1–0.3 min and R.S.D. of peak heights 4–14% (n = 3). In terms of analyte trapping efficiency on-line SPE-LC-UV with a CPP-50 precolumn also showed better performance than when Bondesil C18/OH or polymeric PLRP-S was used, but chromatographic resolution was similar. With the CPP-50-based system, detection limits of the test compounds were 0.05–1 μg/l in surface water.
Author Keywords: Environmental analysis; Water analysis; Adsorbents; Sample preparation; Pesticides.
J. Slobodník, A.C. Hogenboom, J.J. Vreuls, J.A. Rontree, B.L.M. van Baar, W.M.A. Niessen, U.A.Th. Brinkman, Trace-level determination of pesticide residues using on-line solid-phase extraction/liquid chromatography with atmospheric pressure ionisation mass spectrometric and tandem mass spectrometric detection, J. Chromatogr. A, 741 (1996) 59.
Abstract: Column liquid chromatography (LC) with pneumatically assisted electrospray (PA-ESP) or atmospheric pressure chemical ionization (APCI) followed by (tandem) mass spectrometry (MS or MS-MS) was used for the analysis of a test mixture of 17 pesticides. In order to achieve low-ng/l detection limits, solid-phase extraction (SPE) of a 100-ml aqueous sample on a small cartridge packed with a hydrophobic sorbent was used. The LC set-up was coupled on-line to the MS part of the system. The complete analysis was automated by means of a gradient controller and a Prospekt valve switching, solvent selection and cartridge exchange unit. When using SPE-LC with either APCI or PA-ESP, the detection limits of 15 (out of the 17) pesticides in tap water were 0.007–3 μg/l in the full-scan and 0.1–200 ng/l in the SIM mode, with an analysis time of 65 min. Fenchlorphos and bromophos-ethyl could not be detected by either ionization method. APCI full-scan spectra showed much less sodium and acetonitrile/water cluster adducts than PA-ESP spectra. Negative ion (NI) operation was less sensitive for the majority of the compounds tested (73 in total), but several organophosphorus pesticides, nitrophenols and chlorophenols only gave a response in the NI mode. PA-ESP-MS-MS and APCI-MS-MS gave similar product-ion spectra from protonated molecules; an MS-MS library was built for more than 60 pesticides and their degradation products, at constant settings of collision gas pressure (argon, 2.0 × 10−3 Torr) and collision energy (25 eV). The library was successfully used for searching product-ion spectra from SPE-LC-APCI-MS-MS at low levels (10 ng/l) in tap water and for the identification of atrazine in surface water (estimated concentration 0.25 μg/l).
Author Keywords: Mass spectrometry; Trace analysis; Tandem mass spectrometry; Pesticides.
J. Slobodník, M.E. Jager, S.J.F. Hoekstra-Oussoren, M. Honing, B.L.M. van Baar and U.A.Th. Brinkman, Identification of carbamates by particle beam/mass spectrometry, J. Mass Spectrom., 32 (1998) 43-54.
Abstract: The possibility of analysing 33 carbamate pesticides and 14 of their transformation products was investigated utilizing flow injection particle beam/mass spectrometry (PBMS) with electron impact (EI) ionization and ammonia and methane positive and negative chemical ionization (CI). Optimum operating conditions of the interface and mass spectrometer in each mode were determined, with special attention given to spectrum quality; variables investigated included ion source temperature and ion source pressure in CI experiments. Ammonia, as a reagent gas, provided less fragmentation and better quantitative results than methane. The CI response was generally higher with positive ion detection (PCI) than with negative ion detection (NCI), but NCI was found to be highly selective for compounds such as aminocarb, asulam and thiophanate-methyl. As regards analyte detectability, EI performed best for most compounds, with the spectra providing relevant structure information. The response of more polar degradation products is generally larger by 2–3 orders of magnitude compared with the parent compounds. When analysing real samples, the combined use of CI for molecular mass determination and EI for structure elucidation is required. The spectral information from this study and additional chromatographic data were used for the determination of low- and sub-μg l-1levels of the test carbamates in surface water.
A.C. Hogenboom, J. Slobodník, J.J. Vreuls, J.A. Rontree, B.L.M. van Baar, W.M.A. Niessen and U.A.Th. Brinkman, Single short-column liquid chromatography with atmospheric pressure chemical ionization - (tandem) mass spectrometric detection for trace level environmental analysis, Chromatographia, 42 (1996) 506.
Abstract: Single short, i.e. ca 2-cm long, high-pressure-packed columns coupled with mass spectrometric (MS) or tandem MS detection enable rapid trace-level determination and identification of environmental pollutants in water samples. In this study an atmospheric pressure chemical ionization (APCI) interface has been used and the overall set-up was tested with a mixture of seventeen pesticides, including organophosphates, carbamates, phenylureas and triazines. For the majority of the test analytes, the most prominent peaks in the positive-ion APCI-MS spectra resulted from protonated molecules. For fifteen out of the seventeen pesticides short-column liquid chromatography (LC)-APCI-MS of water samples as small as 15 mL resulted in detection limits between 0.03 and 5 g L–1 in full-scan mode and between 2 and 750 ng L–1 by selected ion monitoring (SIM), both recorded in the positive-ion mode. Production spectra from protonated molecules of the majority of the selected pesticides present at a level of 0.1 g L–1 in tap water are successfully identified from a search against a pesticide MS-MS library compiled in-house. This short-column LC-APCI-MS(-MS) approach has, on the basis of full-scan positive-ion data and their product-ion spectra, also been used to confirm the identity of target compounds and to identify unknown organic micropollutants in environmental waters.
J. Slobodník, S.J.F. Hoekstra-Oussoren, M.E. Jager, M. Honing, B.L.M. van Baar and U.A.Th. Brinkman, On-line solid-phase extraction-liquid chromatography-particle beam mass spectrometry and gas chromatography-mass spectrometry of carbamate pesticides, Analyst, 121 (1996) 1327.
W.A. Minnaard, J. Slobodnik, J.J. Vreuls, K.-P. Hupe and U.A.Th. Brinkman, Rapid liquid chromatographic scereening of organic micropollutants in aqueous samples using a single short column for trace enrichment and separation, J. Chromatogr. A, 696 (1995) 333.
Abstract: A single short (20 mm × 4 mm I.D.) column packed with C18-bonded silica is used for both trace enrichment and liquid chromatographic (LC) separation of organic micropollutants in aqueous samples. The column can be used for at least twenty real-life samples without any decrease of performance. On-line short-column LC-diode array UV detection enables the detection of down to about 1 μg/l of organophosphorus and other polar pesticides in surface water, using 15-ml samples. The total time of analysis is ca. 25 min. Preliminary results are shown for short-column LC-particle beam mass spectrometry.
J. Slobodník, B.L.M. van Baar and U.A.Th. Brinkman, Column-liquid chromatography/mass spectrometry: Environmental applications for polar pesticides and related compounds, review, J. Chromatogr. A, 703 (1995) 81.
Abstract: A review covering the field of environmental applications of liquid chromatography-mass spectrometry (LC-MS) is presented. Recent developments and advances are discussed with emphasis on the presently popular thermospray, particle beam and atmospheric pressure ionisation interfaces. Each interface is described separately covering the principle of operation, typical detection limits and characteristics of the mass spectra. All reviewed interfacing techniques provide useful data for identification/confirmation of analytes with various chemical properties. The application-oriented part of the review primarily deals with polar pesticides and related compounds. However, generally speaking the conclusions which are drawn also hold true for other classes of micro-contaminants. LC-MS obviously is complementary to ‘routine’ GC-MS and it extends the boundaries of the ‘analytical window’ of mass spectrometry to polar, non-volatile and/or thermolabile compounds. LC-MS is a powerful tool in environmental analysis and especially when it is combined with appropriate sample-treatment procedures it allows one to obtain detection limits adequate for trace-level analysis.
J. Norberg, J. Slobodnik, R.J.J. Vreuls, U.A.Th. Brinkman, On-line solid phase extraction-liquid chromatography for screening and quantification of organophosphorus pesticides in surface water, Analytical Methods and Instrumentation, 2, 5 (1995) 266 – 276.
Abstract: The potential of the on-line combination SPE/LC/DAD was studied for the determination of organophosphorus pesticides. The separation was optimized with regard to gradient conditions and temperature. Sample pretreatment procedures such as pH adjustment and addition of a surfactant or a few per cent of methanol to the sample were tested. The final system allows the determination of some 20 model compounds at or below the 1 µg/L level in river water; many of these can even be determined at the 0.1 µg/L level required for drinking water.
J. Slobodník, S.J.F. Hoekstra-Oussoren and U.A.Th. Brinkman, Automated determination of polycyclic aromatic hydrocarbons by on-line solid-phase extraction/liquid chromatography/particle beam-mass spectrometry, Anal. Meth. Instrum., 2, 5 (1995) 227.
M. Honing, D. Barcelo, M.E. Jager, J. Slobodnik, B.L.M. van Baar, U.A.Th. Brinkman, Effect of ion source pressure on ion formation of carbamates in particle-beam chemical-ionisation mass spectrometry, J. Chromatogr. A, 712 (1995) 21 – 30.
M.G.M. Groenewegen, N.C. van de Merbel, J. Slobodnik, H. Lingeman, U.A.Th. Brinkman, Automated determination of weakly acidic and basic pollutants in surface water by on-line electrodialysis sample treatment and column liquid chromatography, Analyst, 119 (1994) 1753 – 1758.
Abstract: The use of on-line electrodialysis for the treatment of natural waters prior to the column liquid chromatographic determination of polar pollutants is described. The influence of several system parameters, such as electrical potential, donor flow rate, sample volume and pore size of the separation membrane, on the enrichment of various weak acids and bases and on the removal of interfering matrix components was evaluated. Further, the effect of a pH shift taking place in the sample during electrodialysis was studied. The completely automated procedure allows a 7–10-fold selective enrichment of the analytes (several anilines and chlorinated phenoxy acids) from 750 μl surface water samples within 25 min by applying a donor flow rate of 50 μl min−1 and a potential of 7.5–10 V. A separation membrane with 3.5 kDa pore size removes more of the matrix and yields 2–5-fold lower detection limits than a 15 kDa membrane. Under these conditions and using LC with UV detection, detection limits for all compounds studied were in the range 0.5–5.0 μg l−1 in surface water.
U.A.Th. Brinkman, J. Slobodník and J.J. Vreuls, Trace-level detection and identification of polar pesticides in surface water: the SAMOS approach, Trends in Anal. Chem., 13 (1994) 373.
Abstract: In recent years, much attention has been devoted to the low- and sub-μg/l trace-level determination of polar pesticides and related chemical compounds in surface and drinking water. The large number of analyses that have to be carried out and the general demand for speed and automation require the development of on-line and integrated analytical systems. Recent developments in the area of on-line trace enrichment-LC or GC separation—detection/identification SAMOS systems are discussed. The practicality of the approach is highlighted by giving real-life examples taken from studies on the quality of the surface water of several European rivers.
J. Slobodník, M.G.M. Groenewegen, E.R. Brouwer, H. Lingeman and U.A.Th. Brinkman, Fully automated multi-residue method for trace-level monitoring of polar pesticides by liquid chromatography, J. Chromatogr., 642 (1993) 359.
Abstract: A fully automated liquid chromatographic method using on-line trace enrichment, gradient elution and diode-array detection for the trace level determination of polar pesticides in surface water is described. The automated system uses specially developed software in the form of "user macros", allowing the on-line control of both the automated cartridge exchange unit for sample preparation and the liquid chromatograph with diode-array detector by means of the Pascal Workstation computer of that liquid chromatographic system. The collected data are automatedly evaluated, i.e., pollutants present in the sample at a concentration level above an input treshold level are identified/determined and a report is printed. Parameters such as the sampling interval of the spectra, temperature of the analytical column compartment, wavelength/bandwidth ratios and data handling were optimized. The validation results for 27 pesticides are presented. At an analyte concentration of 1 μg/1 the relative standard deviations of the retention times and peak areas in different types of water are in the range 0.2–1.5% and 1–15%, respectively. All calibration graphs are linear in the range 0.1–7 μg/1.
H. Bagheri, J. Slobodník, R.M. Marce Recasens, R.T. Ghijsen and U.A.Th. Brinkman, Liquid chromatography/particle beam-mass spectrometry for the identification of unknown pollutants in water, Chromatographia, 37 (1993) 159.
Abstract: Trace enrichment on a precolumn packed with copolymer material, coupled on-line with reversed-phase, column liquid chromatography-particle beammass spectrometry (RPLC-PB-MS) has been used for both target and non-target analysis of water samples. RPLC is carried out on a C-18-bonded silica column using a linear acetonitrile-0.1 M ammonium acetate gradient. Using optimised PB-MS conditions and 100–250 ml water samples, the detection limits for several phenylureas are in the 0.03–0.05 g l–1 range using the full-scan mode; repeatability is good and the LC-PB-MS system is robust. Several surface and drinking water samples have been analysed and low levels of various environmental contaminants have been identified using electron impact mass spectra. Applying chemical ionisation with methane as reagent gas in both the positive and negative mode in conjunction with PB-MS provides relevant confirmatory information.
E.R. Brouwer, J. Slobodník, H. Lingeman and U.A.Th. Brinkman, Determination by reversed-phase ion-pair chromatography of aromatic sulphonic acids in surface water, Analusis, 20 (1992) 121.
J. Slobodník, E.R. Brouwer, R.B. Geerdink, W.H. Mulder, H. Lingeman and U.A.Th. Brinkman, Fully automated on-line liquid chromatographic separation system for polar pollutants in various types of water, Anal. Chim. Acta, 268 (1992) 55.
Abstract: A fully automated column liquid chromatographic separation system using on-line trace enrichment, gradient elution and diode-array detection for the trace-level determination of polar pollutants is described. Automation of the system was achieved by means of an automated cartridge-exchange system (PROSPEKT). Relevant parameters such as pH, volume and ionic strength of the sample, flow-rate during the enrichment step and wavelengths and band widths during detection were optimized for eighteen pollutants in various types of water at concentration levels below 5 μg l−1. The determination limit for all test compounds in liquid chromatographic grade water was 0.1 μg l−1, and identification, via diode-array spectra, could be performed at the same level. The mean relative standard deviations of the peak areas and the retention times for all the test compounds were 10% and 0.3%, respectively, at the 5 μg l−1 level for river Rhine water.
Author Keywords: Liquid chromatography; Sample preparation; Pesticides; Polar pollutants; Waters