Determination of some pesticides and intermediates by ion chromatography

A method for the quantitative analysis of polar anionic pesticides in milk/infant formula, cereals and fruit and vegetables using ion chromatography coupled to tandem mass spectrometry

Polar pesticides such as anionic or ionisable compounds have always provided a challenge for analytical chemists. Methods of analysis have been developed using a range of techniques including normal phase chromatography, ion-pairing, derivatisation and HILIC or multi-mode chromatography. These work well with some of these compounds but, except for HILIC, all of them have their limitations and none of them cover the range required by legislation. Some of these compounds, glyphosate, chlorate and phosphonic acid, are found regularly in a range of food matrices, and therefore reliable methods of analysis are essential. This study describes an ion chromatography method with tandem mass spectrometry detection which not only covers the full range of compounds required by legislation but also can be expanded to include other anionic or ionisable pesticides and metabolites. These include glyphosate and its metabolites, glufosinate and its metabolites, ethephon and its metabolites as well as fosetyl aluminium, chlorate and perchlorate. The method is fully validated according to the performance criteria from the SANTE guidelines for the analysis of pesticides in food and feed over a wide range of matrices, including milk, infant formula, cereals and fruits and vegetables. Over 300 food samples have analysed as part of our routine monitoring program.

Titanium dioxide based nanocomposites - Current trends and emerging strategies for the photocatalytic degradation of ruinous environmental pollutants

Many ruinous pollutants are omnipresent in the environment and among them; pesticides are xenobiotic and pose to be a bio-recalcitrance. Their detrimental ecological and environmental impacts attract attention of environmental excerpts and the surge of stringent regulations have endows the need of a technically feasible treatment. This critical review emphasizes about the occurrence, abundance and fate of structurally distinct pesticides in different environment. The practiced remedial strategies and in particular, the advanced oxidation processes (AOPs) those utilize the photo-catalytic properties of nano-composites for the degradation of pollutants are critically discussed. Photo-catalytic degradation utilizes many composite materials at nano-scale level, wherein synthesis of nano-composites with appropriate precursors and other adjoining functional moieties are of prime importance. Therefore, suitable starter materials along with the reaction conditions are prerequisite for effectively tailoring the nano-composites. The aforementioned aspects and their customized applications are critically discussed. The associated challenges, opportunities and process economics of degradation using photo-catalytic AOP techniques are highlighted and in addition, the review tries to explain how best the photo-degradation can be a stand-alone tool with a societal importance. Conclusively, the future prospects for undertaking new researches in photo-catalytic breakdown of pollutants that can be judiciously sustainable.

Temperature-enabled reversible "On/Off" switch-like hazardous herbicide picloram voltammetric sensor in agricultural and environmental samples based on thermo-responsive PVCL-tethered MWCNT@Au catalyst

Picloram (PCR), a vastly utilized chlorinated herbicide, is very stable in water and soil with severe ecological and health impacts. It is necessary to establish a fast and highly sensitive technique for accurately detecting trace level PCR in agricultural and environmental samples. We employed a temperature-responsive poly(N-vinylcaprolactam)-tethered multiwalled carbon nanotubes (MWCNT-PVCL) decorated gold nanoparticles (Au@MWCNT-PVCL) catalyst on the electrochemical sensor for the sensitive "On/Off" switch-like detection of PCR. The effect of temperature-sensitive catalyst surface chemistry on electrocatalytic activity was scrutinized. Results showed that the hydrophilic surface of PVCL at 25 °C (<lower critical solution temperature (LCST)) extended to bury the electroactive sites of Au nanoparticles and MWCNT, and the PCR unable to pass over the PVCL to achieve electron exchange process, signifying the "Off" state. Surface wettability of the prepared Au@MWCNT-PVCL then spontaneously switched its hydrophilic to hydrophobic surface one at 40 °C (>LCST) that immensely upgraded PCR oxidation on the catalyst in the electrochemical reaction, signifying the "On" state. The detection of the Au@MWCNT-PVCL modified electrode ranged from 0.02-183 μM with a low detection limit (LOD) of 1.5 nM at 40 °C toward PCR. The proposed sensor was successfully used to detect PCR in real agricultural and environmental samples.

Simultaneous determination of acetamiprid and 6-chloronicotinic acid in environmental samples by using ion chromatography hyphenated to online photoinduced fluorescence detector

This study aims to introduce a simple, sensitive, and cost-effective method for the simultaneous determination of acetamiprid and its main metabolite 6-chloronicotinic acid in environmental samples by using a nonsuppressed ion chromatography hyphenated with an online postcolumn photoinduced fluorescence detection system. The fluorescence detector wavelengths λ_ex /λ_em  = 257/382 nm was set for up to 6.0 min for acetamiprid, while λ_ex /λ_em  = 231/370 nm programmed for 6-chloronicotinic acid for the rest of the analysis time. Both samples were treated by applying miniaturized quick, easy, cheap, effective, rugged, and safe method before the separation of analytes on an IonPac^® AS11-HC column by pumping 40 mM NaOH having minuscule content of acetonitrile (5%, v/v) as an eluent. Both intrinsically nonfluorescent analytes were turned-on by online postcolumn photoinduced derivatization, avoiding the need for complex chemical derivatization or addition of a postcolumn extra pump. The developed method was appraised for the analysis of environmental samples, exhibiting excellent linearity (0.050-10 μg/mL) with a correlation coefficient greater than 0.9993 for both analytes. Whereas, obtained limit of detection (0.025-0.0072 μg/mL), recoveries (98.02-116.00%), and inter- and intraday precision (≤3.02 %) were satisfactory for both compounds in environmental samples.

A novel strategy based on surfactant assisted electromembrane extraction for the determination of dicamba and 2,4-DB as model herbicides in real water samples

Schematic illustration of the surfactant assisted electromembrane-extraction (SEME) technique.

Chemometric experimental design based optimization techniques in capillary electrophoresis: a critical review of modern applications

A critical review of recent developments in the use of chemometric experimental design based optimization techniques in capillary electrophoresis applications is presented. Current advances have led to enhanced separation capabilities of a wide range of analytes in such areas as biological, environmental, food technology, pharmaceutical, and medical analysis. Significant developments in design, detection methodology and applications from the last 5 years (2002-2007) are reported. Furthermore, future perspectives in the use of chemometric methodology in capillary electrophoresis are considered.

Separation and determination of 2,4-D, dicamba and 2,4,5-T in tobacco by nonaqueous capillary electrophoresis

A practical method for residue analysis of 2,4-D, dicamba and 2,4,5-T in baked tobacco leaves has been developed using nonaqueous CE (NACE). The herbicide residues of 2,4-D, dicamba and 2,4,5-T in tobaccos were extracted by ultrasonication with ethyl acetate, followed by a cleanup procedure with gel permeation chromatography. The separation of 2,4-D, dicamba and 2,4,5-T by NACE was optimized based on orthogonal experiment design with four factors at three levels. The optimal NACE condition was established with the running buffer of 40.0 mmol/L ammonium acetate in 90% CH3CN (apparent pH 10.2), and the applied voltage of -25 kV over a capillary of 50 microm id x 46 cm (37.5 cm to the detector window), which gave a baseline separation of 2,4-D, dicamba and 2,4,5-T within 15 min. The LOD were ca. 0.4-0.6 microg/mL for the three herbicides, whereas the overall recovery ranged from 80.8 to 84.1%. The proposed method has been successfully applied to measure 300 real tobacco samples, and the residue profiles of the three herbicides in tobacco samples were obtained and evaluated.

Polychlorinated dibenzo-p-dioxins, dibenzofurans, and polychlorinated biphenyls in human tissues, meat, fish, and wildlife samples from India

Concentrations of polychlorinated dibenzo-p-dioxins (PCDDs), dibenzofurans (PCDFs), and non- and mono-ortho-substituted polychlorinated biphenyls (dioxin-like PCBs) were measured in tissues of humans, fishes, chicken, lamb, goat, predatory birds, and Ganges River dolphins collected from various locations in India. PCDDs/DFs were found in most of the samples analyzed with the liver of spotted owlet containing the highest concentration of 3,300 pg/g, fat wt. 2,3,7,8-Substituted PCDDs and PCDFs were found in human fattissues at concentrations ranging from 170 to 1,300 pg/g, fat wt. Concentrations of PCDDs were generally greaterthan those of PCDFs in human tissues, fishes, animal fat, and dolphin. Among fishes, meat, and wildlife samples analyzed, concentrations of PCDDs/DFs were found in the following order: country chicken < goat/lamb fat < fishes < river dolphins < predatory birds. Hepta-CDDs and OCDD were the major PCDD homologues found in humans, fishes, meat products, and dolphins. 2,3,7,8-Tetrachlorodibenzo-p-dioxin equivalents of PCDDs/DFs were greater than those of PCBs in selected fish, dolphin, and human samples. To our knowledge, this is the first report of PCDDs and PCDFs in human tissues, fishes, meat, and wildlife collected from India.