Fully automated on-line liquid chromatographic separation system for polar pollutants in various types of water

Identification of unknown microcontaminants in Dutch river water by liquid chromatography-high resolution mass spectrometry and nuclear magnetic resonance spectroscopy

In the past decade during automated surface water monitoring in the river Meuse at border station Eijsden in The Netherlands, a set of unknown compounds were repeatedly detected by online liquid chromatography-diode-array detection in a relatively high signal intensity. Because of the unknown nature of the compounds, the consequently unknown fate of this mixture in water treatment processes, the location being close to the water inlet of a drinking water supply company and their possible adverse public health effects, it was deemed necessary to elucidate the identity of the compounds. No data are available for the occurrence of these unknowns at downstream locations. After concentration and fractionation of a sample by preparative Liquid Chromatography, identification experiments were performed using Liquid Chromatography-High Resolution Mass Spectrometry (LC-HR-MS) combined with High Resolution Nuclear Magnetic Resonance Spectroscopy (HR-NMR). Accurate mass determination of the unknown parent compound and its fragments obtained in MS/MS provided relevant information on the elemental composition of the unknown compounds. With the use of NMR techniques and the information about the elemental composition, the identity of the compounds in the different sample fractions was determined. Beside some regularly detected compounds in surface water, like caffeine and bisphenol-S, five dihydroxydiphenylmethane isomers were identified. The major unknown compound was identified as 4,4'-dihydroxy-3,5,3',5'-tetra(hydroxymethyl)diphenylmethane. This compound was confirmed by analysis of the pure reference compound. This is one of the first studies that employs the combination of high resolution MS with NMR for identification of truly unknown compounds in surface waters at the μg/L level. Five of the seven identified compounds are unexpected and not contained in the CAS database, while they can be presumed to be products generated during the production of resins.

Preconcentration of contaminants in water analysis

Among the environmental areas, in this review attention will be focused on water matrices and both on organic (e.g., pesticides, herbicides, phenols, polycyclic aromatic hydrocarbons), inorganic species and anion pollutants, since these kinds of substances include a wide number of compounds with different physical and chemical properties and different effects on human health. Analytical methods for control of quality of waters are required to be highly specific and possibly highly sensitive for the determination of even low amounts of pollutants. The main problems encountered during the analysis are the separation of matrix components from the pollutants of interest and the achievement of low detection limits. Therefore an overview on different materials and techniques available for sample concentration and/or matrix removal will be provided and discussed according to the chemical characteristics of the pollutant that has to be enriched.

Recent developments in polymer-based sorbents for solid-phase extraction

A review with 136 references on the principles and recent developments in the solid-phase extraction based on polymer sorbents is presented. New polymer-based materials, chromatographic modes, experimental configurations are described and their advantages for a rapid sample preparation of certain classes of compounds with different functional groups are discussed and compared to silica-based sorbents.

Comparison of various liquid chromatographic methods involving UV and atmospheric pressure chemical ionization mass spectrometric detection for the efficient trace analysis of phenylurea herbicides in various types of water samples

The performance of mass spectrometric (MS) detection and UV detection in combination with reversed-phase liquid chromatography without and with the use of coupled column RPLC (LC-LC) has been compared for the trace analysis of phenylurea herbicides in environmental waters. The selected samples of this comparative study originated from an inter-laboratory study. For both detection modes, a 50 mm x 4.6 mm I.D. column and a 100 mm x 4.6 mm I.D. column packed with 3 microm C18 were used as the first (C-1) and second (C-2) column, respectively. Atmospheric pressure chemical ionization mass spectrometry was performed on a magnetic sector instrument. The LC-LC-MS analysis was carried out on-line by means of direct large volume (11.7 ml) injection (LVI). The performance of both on-line (LVI, 4 ml of sample) and off-line LC-LC-UV (244 nm) analysis was investigated. The latter procedure consisted of a solid-phase extraction (SPE) of 250 ml of water sample on a 500 mg C18 cartridge. The comparative study showed that LC-LC-MS is more selective then LC-LC-UV and, in most cases, more sensitive. The LVI-LC-LC-MS approach combines direct quantification and confirmation of most of the analytes down to a level of 0.01 microg/l in water samples in less then 30 min. As regards LC-LC-UV, the off-line method appeared to be a more viable approach in comparison with the on-line procedure. This method allows the screening of phenylurea's in various types of water samples down to a level of at least 0.05 microg/l. On-line analysis with LVI provided marginal sensitivity (limits of detection of about 0.1 microg/l) and selectivity was sometimes less in case of surface water samples. Both the on-line LVI-LC-LC-MS method and the LC-LC-UV method using off-line SPE were validated by analysing a series of real-life reference samples. These samples were part of an inter-laboratory test and contained residues of herbicides ranging from 0.02 to 0.8 microg/l. Beside good correlation between the methods the data agreed very well with the true values of the samples.

Solid-phase extraction followed by high-performance liquid chromatography-ionspray interface-mass spectrometry for monitoring of herbicides in environmental water

In this work we developed a sensitive and specific multiresidue method, based on reversed-phase liquid chromatography-mass spectrometry, with an ionspray interface (LC-ISI-MS), for determining 52 of most representative compounds of herbicides in water samples. The procedure used involved passing 0.5 l of surface water, 2 l of ground water and 4 l of drinking water samples, respectively, through a 0.5 g graphitized carbon black (GCB) extraction cartridge. Base-neutral and acid herbicides were differential eluted from GCB cartridge and follow analyzed by HPLC-ISI-MS apparatus. A conventional 4.6-mm-ID reversed-phase LC C18 column, operating with a mobile phase flow-rate of 1 ml/min, was used to chromatograph the analytes. A flow of 100 microl/min of the column effluent was diverted to the ISI source. The study demonstrates the sensitivity of the technique, with detection limit under 10 ng/l in drinking water samples. Performance data for the method such as recovery and precision are also reported.

Determination of hydroxyaromatic compounds in water by solid-phase microextraction coupled to high-performance liquid chromatography

Solid-phase microextraction (SPME) coupled with high-performance liquid chromatography (HPLC) for the analysis of hydroxyaromatic compounds is described. Three kinds of fibers [50 microns carbowax-templated resin (CW-TPR), 60 microns polydimethylsiloxane-divinylbenzene (PDMS-DVB) and 85 microns polyacrylate (PA) fibers] were evaluated. CW-TPR and PDMS-DVB were selected for further study. The parameters of the desorption procedure (such as desorption mode, the composition of the solvent for desorption and the duration of fiber soaking) were studied and optimized. The effect of the structure and physical properties of analytes, carryover, duration of absorption, temperature of absorption, pH and ionic strength of samples were also investigated. The method was applied to environmental samples (lake water) using a simple calibration curve.

Comparison of various sample handling and analytical procedures for the monitoring of pesticides and metabolites in ground waters

Various sample handling techniques such as liquid-liquid extraction off-line and on-line, solid-phase extraction followed by either gas chromatography (GC) with electron-capture, flame photometric or mass spectrometric detection, or liquid chromatography (LC) with diode array detection were applied in the determination of a selected group of insecticides and fungicides in ground water samples at sub-micrograms/l levels. An evaluation of the advantages and drawbacks in the application of the proposed methodologies for water monitoring studies is discussed. For the selected group of pesticides studied, off-line C18 or polymeric cartridges followed by GC-MS using an ion trap analyzer have been revealed as the more powerful technique. But very polar compounds such as methamidophos or acephate have not been recovered with this procedure. On the contrary, on-line C18 LC-DAD offered a few drawbacks for the trace determination of a large group of pesticides as a consequence of many important interferences in the chromatographic traces. Other techniques evaluated were LC-MS and GC-MS using a quadrupole analyzer, which offered complementary information and were useful for a limited range of analytes. An interlaboratory study was performed using all the methodologies evaluated in this work and the results obtained showed a good agreement between all the applied techniques. The various methodologies were for a ground water pilot survey study in Almeria (Spain). Endosulfan was the most ubiquitous pesticide detected in this area.

Comparison of different sorbents for on-line liquid-solid extraction followed by high-performance liquid chromatographic determination of nitrogen-containing pesticides

LiChrolut EN [poly(styrene-divinylbenzene), PSDVB], Carbograph (graphitized carbon black, GCB), Isolute CN (cyanopropylsilica), Isolute C2 (ethylsilica), and LiChrospher RP18 (octadecylsilica) were studied for on-line solid-phase extraction of twelve nitrogen containing pesticides from water. Determination (UV 210 nm) was performed with a Spherisorb C8 analytical column and an acetonitrile-water gradient. The mean recoveries from 50 ml ranged from 83% for RP18 to 44% for GCB, and decreased in the following order: RP18, CN, LiChrolut EN, C2, and GCB. GCB showed poor recoveries due to incomplete desorption with the acetonitrile-water gradient used, and memory effects were detected. Backflush was needed to elute selected pesticides from GCB and from LiChrolut EN. Breakthrough volumes were 50-100 ml for most selected pesticides with silica-based phases, whereas LiChrolut EN allowed larger sample volumes without observable losses.

Application of an on-line liquid chromatographic system for the determination of polar herbicides in drinking water within a routine laboratory

A previously developed on-line automated system for the analysis of polar herbicides in raw and drinking water, was further optimised for use within a routine environmental monitoring laboratory. One-hundred-ml portions of sample were extracted onto interchangeable, PLRP-S packed cartridges, prior to desorption by the mobile phase of an HPLC system. Determination of triazine and phenylurea herbicides was achieved by UV diode array detection, with detection limits ranging between 0.002 and 0.012 microgram l-1. Precision, in HPLC grade water, ranged from 3.1 to 9.7% R.S.D. at the 0.090 microgram l-1 level, as determined at those wavelengths selected for routine analysis. Confirmation of positive results was achieved by library searching of UV spectra. The system was found to be robust for routine analysis, with a sample throughput of ten samples per day.

Baker's yeast biomass (Saccharomyces cerevisae) for selective on-line trace enrichment and liquid chromatography of polar pesticides in water

Baker's yeast cells (Saccharomices cerevisae) were successfully immobilized onto silica gel and used in the on-line isolation and trace enrichment of desisopropylatrazine, desethylatrazine, hydroxyatrazine, simazine, cyanazine, atrazine, carbaryl, propanil, linuron, and fenamiphos. Since humic and fulvic acids were not coextracted, no cleanup was necessary. The pesticides were spiked at 0.1-1 microgram L-1 in tap water, groundwater, and seawater and were preconcentrated using on-line solid-phase extraction into a yeast immobilized on silica gel precolumn followed by liquid chromatography with diode array detection. All the variables that affect the enrichment step, such as amount of yeast immobilized, dimensions of the precolumn, sample pH, and preconcentration flow rate, were optimized. The degree of selectivity was evaluated by comparing the chromatograms obtained after on-line sample preconcentration on the yeast precolumn with those obtained by on-line solid-phase extraction using a precolumn filled with C18 material. The relative standard deviation for the whole procedure in the determination of the selected pesticides at the 0.3 microgram L-1 concentration level ranged from 1 to 9%, depending on the pesticide and the type of water. Detection limits within the range 0.01-0.5 microgram L-1 were obtained by percolating only 25 mL of water sample without any additional cleanup step.

Screening and analysis of polar pesticides in environmental monitoring programmes by coupled-column liquid chromatography and gas chromatography-mass spectrometry

Screening and analysis of polar pesticides based on coupled-column reversed-phase liquid chromatography (LC-LC) and GC- or LC-MS is a powerful tool in the execution of environmental monitoring programmes. This paper presents a unified approach utilising LC-LC screening followed by GC-MS confirmation. As polar pesticides are not generally amenable to GC a widely applicable derivation technique is used. The results demonstrate that the proposed LC and MS techniques are capable of analysing a wide range of polar pesticides down to levels of 0.1 microgram/l (EU limit for drinking water). LC switching techniques for group analysis or individual compounds rely on the reversed-phase retention and the UV detectability of the pesticides in combination with the choice of the LC columns. Fast miniaturised derivatization prior to GC-MS forms an integral part in the proposed strategy. In order to avoid extraction losses, derivation in the aqueous sample, preferably with electrophoric reagents with enhanced sensitivity in GC-NICI-MS are employed where possible. In this communication, method development and validation fitting in the strategy are evaluated and the results of the combined approach are discussed.

Occurrence and determination of pesticides in natural and treated waters

Pesticides as environmental pollutants are described in detail along with their sources and paths of entry into various elements of the environment. Comprehensive literature data on the concentration of these pollutants in natural and treated waters and wastewaters are discussed. A wide selection of isolation and preconcentration techniques for these pollutants in water is presented and discussed. An emphasis is put on solid-phase extraction. In the case of the authors' work, a more detailed description is given.

Strategies for chromatographic analysis of pesticide residues in water

A review is presented of the modern techniques and approaches in methods for pesticide residue analysis in water matrices. The state of the art of the individual steps (extraction, clean-up, separation, identification, quantitation) of the chromatographic methods is reviewed with emphasis laid on emerging techniques which have gained popularity. The new approaches are discussed with respect to their relevancy to the requirements for increasing the sensitivity of detection and reliability of identification and quantitation at low levels of concentrations, arising from the European Community Drinking Water Directive.