Trace analysis of isothiazolinones in water samples by large-volume direct injection liquid chromatography tandem mass spectrometry.

Isothiazolinones are used as preservatives, biocides and disinfectants in a variety of industrial and domestic applications. Some of the isothiazolinones are difficult to isolate from water due their high polarity. A sensitive and selective analytical method was developed and optimized for the determination of sub-microg/L levels of three isothiazolinones in water samples. Three isothiazolinones are described in this paper: 2-methyl-3-isothiazolinone, 5-chloro-2-methyl-3-isothiazolinone and 4,5-dichloro-2-methyl-3-isothiazolinone. The analytical method involves a robust large-volume direct on-column loop injection of 2 mL on an Aqua ODS HPLC column and tandem MS detection (HPLC-MS/MS). After filtration, samples are directly injected without further pretreatment. Detection limits of the individual target compounds were between 0.03 and 0.1 microg/L employing Multi-Reaction Monitoring (MRM) mass spectrometry. Based on the constant ratio of two selected product-ions together with the retention time, the identification is very selective and quantification is reliable. The method was successfully applied to real samples of membrane flushings, drinking water, surface waters and waste water. Additional investigations showed the instability of the isothiazolinones in river- and waste water. Preservation of river water and waste water samples with sodium azide (NaN(3)) promotes the stability of the isothiazolines in solution. In membrane flushings, waste water, surface waters and drinking water, levels of the three isothiazolinones were all below the limit of detection. In effluents of households containing washings from normal shampoo use, isothiazolinones could be detected.

Determination of the herbicide amitrole in water with pre-column derivatization, liquid chromatography and tandem mass spectrometry.

Amitrole is a widely used polar herbicide, difficult to isolate from water. Due to its persistence, it can easily pollute ground and surface waters used in drinking water production. A fully automated on-line SPE-HPLC (solid-phase extraction-high-performance liquid chromatography) method with atmospheric pressure chemical ionisation-tandem mass spectrometry detection is described for the determination of amitrole. A pre-column derivatization with 9-fluorenylmethoxycarbonyl chloride directly in the native aqueous sample allows an enrichment step by SPE and HPLC separation. Due to the sensitivity of tandem mass spectrometric detection, a limit of detection and quantification as low as 0.025 microg/l was achieved in drinking water and ground and surface water. Based on the constant ratio of two selected product ions together with the retention time, the identification is very selective and quantitation is very reliable. The performance characteristics of the described method fully meet the requirements set by the EU Drinking Water Directive: recoveries of >95% in drinking water and >75% in surface water were achieved, as well as RSD values for repeatability of <9% in drinking water and <12% in surface water (determined at a spiking level of 0.1 microg/l). The method was successfully applied to real samples of ground and surface water with actual concentration up to 1.1 microg/l.

Rapid target analysis of microcontaminants in water by on-line single-short-column liquid chromatography combined with atmospheric pressure chemical ionization tandem mass spectrometry.

The applicability of trace enrichment and separation of microcontaminants on a 10 mm x 2 mm I.D. high-pressure packed (8 microns C18 bonded silica or 10-15 microns PLRP-S) column combined on-line with an atmospheric pressure chemical ionization MS-MS system is demonstrated for the target analysis of herbicides in river water. Tailor-made procedures are obtained for a limited number of analytes by tuning the chromatographic efficiency of the short LC column and the specificity of tandem MS, in order to minimize the analysis time. With the on-line short-column LC-MS-MS method, good linearity is obtained for the herbicides in the range of 0.1-10 micrograms/l. The relative standard deviations of peak areas are less than 5% and, with only 4-ml samples, detection limits of 0.01-0.1 microgram/l can be achieved. The total analysis time is 10-15 min. The 10 mm x 2 mm I.D. LC columns packed with 8 microns particles show good stability and can be used for at least 40 analyses. Target compound analyses of river water allowed the confirmation of the presence of herbicides such as diuron, simazine, atrazine and terbutylazine at sub-microgram/l levels.