Multiresidue solid-phase extraction for trace-analysis of pesticides and their metabolites in environmental water

Abstract

Recent research on the fate and transformation of pesticides in the environment has pointed out the need for including more and more polar analytes in multiresidue analysis. Liquid chromatography have been shown to be suitable for mu l t i residue sep a ration of many compounds over a wide ra n ge of polarity without prev i o u s derivatization. Examples can be found in the literature, the most impressive one being the multiresidue separation of 72 pesticides in one run published by Di Corcia and Marchetti some time ago [1]. However, despite the advances in separation and quantifi c ation tech n i q u e s , no sample can be directly analyzed and a multiresidue extraction is a compulsory step in the analytical procedure.In recent years, enrichment of trace compounds on suitable sorbents has been shown to be an interesting alternative to LLE, and has now become a reliable and useful tool for sample handling. In addition, many modern pesticides and identified degra d ation products are fa i rly soluble in water and are therefore less amenable to solvent extraction. Automation and new trends in SPEThe solid-phase extraction (SPE) area has been very active these past years, certainly due to the now well-recognized trends for using solvent-free methods in environmental analytical laboratories and for its suitability to automation [2]. The four individual steps of a typical SPE sequence-i) conditioning of the sorbent, ii) application of the sample, iii) rinsing and cleaning of the sample, and iv) desorption and recovery of the analytes to be separated-can be performed sequentially for up to 24 cartridges at the same time using extraction units working under positive or negative pressure. The whole sequence can also be easily automated with devices now available by several companies using any comm e rcial cart ri d ges or ex t raction disks. Examples are the ASPEC from Gilson, Microlab from Hamilton, AutoTrace and RapidTrace from Zymark. Possibility exists for some of these devices for automatic injection of an aliquot of the final extract into the chromatographic system. The complete automation also exists which couples SPE with direct online LC analysis (ASPEC XL from Gilson, Prospekt from Spark Holland, OSP-2 from Merck). These last two apparatus improved productivity since the next sample is automatically prepared while the previous sample is being analyzed. Th e re fo re, method development can easily be automat e d with various degrees of automation.Off-line SPE materials are mainly disposable cartridges and disk membranes. Besides automation, two other main SPE characteristics have been commercially developed. The first one tends to increase the sample thoughput and the second one to broaden the polarity range of analytes to extract. R e s t ricted fl ow rates and cl ogging are often observe d when handling water containing suspended solids such as surface water. Various approaches have been developed to solve this problem. One consists in depth filters which can be placed above the cartridge or membrane extracti...

Determination of the pesticides considered as endocrine‐disrupting compounds (EDCs) by solid‐phase extraction followed by gas chromatography with electron capture and mass spectrometric detection

“…These results support other findings reporting that recoveries of virtually all of the routinely determined nitrogen and phosphorus containing herbicides are considerably higher when using SDB as the adsorbent material, than octadecyl silica (C18) [39,40]. The higher retention of SDB sorbents over C18 silicas is due to strong p -p interaction types between analytes and the SDB matrix in addition to common hydrophobic interactions [41]. Moreover, SDB disks do not exhibit the secondary cationic interactions common to bonded silica sorbents, so they offer more predictable and reproducible RP interaction [39].…”

Determination of dimethoate, 2,4-dichlorophenoxy acetic acid, mecoprop and linuron pesticides in environmental waters in Republic of Macedonia by high performance liquid chromatography

“…The presence of pesticides at trace levels in raw waters, has been confirmed in numerous SPE-LC-MS applications [11][12][13][14]. As a consequence, SPE-LC-UV DAD-MS has become a widely used analytical method for the quantitative environmental analysis of pesticides [15][16][17]. Baraud et al developed an improved analytical method for sampling characterization and quantification of pesticides in atmosphere among which were the pesticides investigated in our work [18].…”

“…18) were filtered on Schleicher & Schuell 5841 black ribbon ashless filter paper, and pre concentrated on Bond Elut PPL cartridges optimized for the extraction of highly polar species from large volume water samples. The off-line SPE procedure involves several steps of conditioning, pre concentration, drying and elution [1,5,15,20]. The conditioning was performed with 10 mL of MeOH, followed by 10 mL of water at a flow rate of 2 mL/min.…”

Semiautomated Determination of Pesticides in Water Using Solid Phase Extraction Disks and Gas Chromatography−Mass Spectrometry

“…Pichon (9) reported a linear relation between the average log k w (retention factor of an analyte in water, k w ) values and the log K o/w (K o/w is the water-octanol partition coefficient) for closely related compounds and even for compounds having different polarities and chemical properties. For compounds with a log K o/w > 2.5-3, SPE C 18 silicas are generally appropriate for multiresidue extraction.…”