A review of liquid chromatography in environmental pesticide analysis

Summary The use of liquid chromatography in environental pesticide analysis is reviewed. In addition to classical UV and electrochemical detectors, detection systems such as mass spectromytry and gas chromatographytype detectors are discussed. The applicability of supercritical fluid chromatography to pesticide analysis is also reviewed.Presented at the 18th International Symposium on Environmental Analytical Chemistry, Barcelona 5–8 September, 1988.     

Miniaturization in sample treatment for environmental analysis

The increasing demand for faster, more cost-effective and environmentally friendly analytical methods is a major incentive to improve the classical procedures used for sample treatment in environmental analysis. In most classical procedures, the use of rapid and powerful instrumental techniques for the final separation and detection of the analytes contrasts with the time-consuming and usually manual methods used for sample preparation, which slows down the total analytical process. The efforts made in this field in the past ten years have led to the adaptation of existing methods and the development of new techniques to save time and chemicals, and improve overall performance. One route has been to develop at-line or on-line and, frequently, automated systems. In these approaches, miniaturization has been a key factor in designing integrated analytical systems to provide higher sample throughput and/or unattended operation. Selected examples of novel developments in the field of miniaturized sample preparation for environmental analysis are used to evaluate the merits of the various techniques on the basis of published data on real-life analyses of trace-level organic pollutants. Perspectives and trends are briefly discussed.     

A review of sample preparation methods for the pesticide residue analysis in foods

The pesticide residues in foods have received increasing attention as one of the most important food safety issues. Therefore, more strict regulations on the maximum residue limits (MRLs) for pesticides in foods have been established in many countries and health organizations, based on the sensitive and reliable analysis methods of pesticide residues. However, the analysis of pesticide residues is a continuing challenge mainly because of the small quantities of analytes as well as the large amounts of interfering substances which can be co-extracted with them, often leading to experimental errors and damage to the analytical instruments. Thus, extensive sample preparation is often required for the pesticide residue analysis for the effective extraction of the analytes and removal of the interferences. This paper focuses on reviewing the recent development in the sample preparation methods for the pesticide residue analysis in foods since 2006. The methods include: liquid-liquid extraction (LLE), supercritical-fluid extraction (SFE), pressurized-liquid extraction (PLE), microwave-assisted extraction (MAE), ultrasound-assisted extraction (UAE), gel permeation chromatography (GPC), solid-phase extraction (SPE), molecularly imprinted polymers (MIPs), matrix solid-phase dispersion (MSPD), solid-phase micro-extraction (SPME), QuEChERS, cloud point extraction (CPE) and liquid phase micro-extraction (LPME), etc. Particularly their advantages, disadvantages and future perspectives will be discussed.     

Capillary electrochromatography for pesticide analysis: effects of environmental matrices

An insecticide, pirimicarb, and a fungicide, azoxystrobin, were analyzed by capillary electrochromatography. Nine environmental matrices derived from soil, plant and animal extracts were used. After a series of 311 consecutive injections with no washing between injections, retention times increased by ca. 0.5 min. The use of exaggerated application rates for metabolism studies enabled the detection of xenobiotic pesticide degradates by UV absorbance. A 1.2 mm path length, high-sensitivity flow cell gave a gain in sensitivity; however, a further increase in sensitivity of at least two orders of magnitude is required for pesticide residue analysis. Analyte stacking using large volume injections of aqueous samples led to a large increase in retention times.     

Advances in on-site analytical sample preparation for analysis of environmental waters: A review

The collection, storage, and transportation of water samples from far-off places to the labs is a pretty challenging task. It can cause contamination, degradation, or losses of the analytes, leading to errors in the analysis. On-site sample preparation provides an opportunity to extract the analytes into suitable extraction media that preserves the analytes and is easy to handle in terms of storage and transportation. However, the required equipment for on-site sample preparation should be simple, portable, and energy-efficient. Solvent- and sorbent-based microextraction approaches and the modern variants of solid-phase extraction have shown great potential for on-site sample preparation because of reduced consumption of solvents and low energy requirement. This review provides an overview of the application of different extraction techniques in on-site sample preparation, their advantages, and their limitations. The recent advances combining on-site extraction and analysis have also been critically discussed.     

Ultrasound: A subexploited tool for sample preparation in metabolomics

Metabolomics, one of the most recently emerged “omics”, has taken advantage of ultrasound (US) to improve sample preparation (SP) steps. The metabolomics–US assisted SP step binomial has experienced a dissimilar development that has depended on the area (vegetal or animal) and the SP step. Thus, vegetal metabolomics and US assisted leaching has received the greater attention (encompassing subdisciplines such as metallomics, xenometabolomics and, mainly, lipidomics), but also liquid–liquid extraction and (bio)chemical reactions in metabolomics have taken advantage of US energy. Also clinical and animal samples have benefited from US assisted SP in metabolomics studies but in a lesser extension. The main effects of US have been shortening of the time required for the given step, and/or increase of its efficiency or availability for automation; nevertheless, attention paid to potential degradation caused by US has been scant or nil. Achievements and weak points of the metabolomics–US assisted SP step binomial are discussed and possible solutions to the present shortcomings are exposed.     

A new method for handling liquid samples in organic elemental analysis

Summary A method for handling liquid samples in automatic CHN analysis is described. It involves the use of an aluminum pan in which the sample is hermatically sealed by means of a sealing press. Satisfactory results have been obtained with liquids boiling between 35° and 290°.

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Zusammenfassung Zur Einwaage flüssiger Proben für die automatische CHN-Analyse werden Aluminiumschälehen verwendet, die sich mit einer Presse hermetisch verschließen lassen. Zwischen 35 und 290° siedende Flüssigkeiten lassen sich so mit gutem Erfolg analysieren.

     

Statistical design of data handling in environmental analysis

In environmental analysis, owing to the huge number of analytical data, statistical evaluation is inevitable and must be carefully designed. Though the appropriate statistical test system is basically depending on the given analytical task, some general principles of the statistical design can be outlined, namely: i) before calculating mean value and standard deviation (SD), a preliminary test series must be performed for trend, distribution and outliers; ii) while the trueness of the measured mean values can be tested using appropriate certified reference materials (CRMs), even for a correct test, use of SD reference values are also necessary; iii) as the distribution may differ from the normal one, alternative non-parametric tests must be also built into the test system. The fulfillment of these requirements necessitates a flexible, adaptable statistical software, such as the DATAPRO 2.0 software recently developed.     

Solid-phase microextraction: a promising technique for sample preparation in environmental analysis

Solid-phase microextraction (SPME) is a simple and effective adsorption and desorption technique, which eliminates the need for solvents or complicated apparatus, for concentrating volatile or nonvolatile compounds in liquid samples or headspace. SPME is compatible with analyte separation and detection by gas chromatography and high-performance liquid chromatography, and provides linear results for wide concentrations of analytes. By controlling the polarity and thickness of the coating on the fibre, maintaining consistent sampling time, and adjusting other extraction parameters, an analyst can ensure highly consistent, quantifiable results for low concentration analytes. To date, about 400 articles on SPME have been published in different fields, including environment (water, soil, air), food, natural products, pharmaceuticals, biology, toxicology, forensics and theory. As the scope of SPME grew, new improvements were made with the appearance of new coatings that allowed an increase in the specificity of this extraction technique. The key part of the SPME fibre is of course the fibre coating. At the moment, 27 variations of fibre coating and size are available. Among the newest are a fibre assembly with a dual coating of divinylbenzene and Carboxen suspended in poly(dimethylsiloxane), and a series of 23 gauge fibres intended for specific septumless injection system. The growth of SPME is also reflected in the expanding number of the accessories that make the technology even easier to use Also available is a portable field sampler which is a self-contained unit that stores the SPME fibre after sampling and during the shipment to the laboratory. Several scientific publications show the results obtained in inter-laboratory validation studies in which SPME was applied to determine the presence of different organic compounds at ppt levels, which demonstrates the reliability of this extraction technique for quantitative analysis.     

QSID Tool: a new three-dimensional QSAR environmental tool

QSID Tool (Quantitative structure–activity relationship tool for Innovative Discovery) was developed to provide an easy-to-use, robust and high quality environmental tool for 3D QSAR. Predictive models developed with QSID Tool can accelerate the discovery of lead compounds by enabling researchers to formulate and test hypotheses for optimizing efficacy and increasing drug safety and bioavailability early in the process of drug discovery. QSID Tool was evaluated by comparison with SYBYL^® using two different datasets derived from the inhibitors of Trypsin (Böhm et al., J Med Chem 42:458, 1999) and p38-MAPK (Liverton et al., J Med Chem 42:2180, 1999; Romeiro et al., J Comput Aided Mol Des 19:385, 2005; Romeiro et al., J Mol Model 12:855, 2006). The results suggest that QSID Tool is a useful model for the prediction of new analogue activities.     

A new adsorbent for trace organic analysis in environmental samples

Summary Graphite fluoride has been evaluated as an adsorbent for use in concentrating organic impurities in air and water samples. This material has been shown to yield large breakthrough volumes for most organics and should be useful for trace analysis in environmental chemistry.     

Sorbent-excluding sample preparation method for GC–MS pesticide analysis in apple peel

Apple peel is frequently exposed to pesticides, especially in the last stages of the pesticide treatment practice. For a certain period, peel retains most of the applied pesticides, which precisely indicates the presence of pesticide residues. This study was conducted to establish and evaluate the method for the residue analysis of pyrimethanil, cyprodinil, trifloxystrobin, bifenthrin and boscalid by GC–MS in peel of Granny Smith, Golden Delicious and Idared varieties. The method consisted of few steps, without the routine usage of sorbents, and resulted in efficient removal of waxes, targeted as main interferences in GC–MS analysis. The matrix effect, boscalid selectivity issue, trend of lower trueness for bifenthrin in all matrices and for all analytes in Granny Smith matrix were in some way associated with the waxes. Finally, the method was applied to the analysis of three varieties of apple orchard samples, after 9 and 5 months of treatment with commercial formulations that contain pyrimethanil, cyprodinil and boscalid as active ingredients. Since the developed method consisted of few steps and used nontoxic and economic reagents, it could be implemented as a fast, economic and reliable screening method.     

Coupled LC-GC: A new method for the on-line analysis of organochlorine pesticide residues in fat

This paper describes the use of coupled LC-GC for the determination of organochlorine pesticide residues in fat samples. Organochlorine pesticide residues are preseparated from fat by LC on a short C-18 column using an organic solvent as the mobile phase. Evaporation of the LC eluent is achieved by a modified on-column interface, introducing an on-line vaporizer module using the fully concurrent evaporation technique.     

A new quality control material for marine environmental analysis

The implementation of the European Water Framework Directive (WFD) and of the sediment-quality criteria related to the potential disposal of dredged materials is expected to involve a substantial increase in the number of chemical analyses performed in marine environmental control laboratories. The chemical characterization of sediments (metals, elemental composition, etc.) and the potential release of metals under changing environmental conditions are relevant when dealing with risk assessment. The present paper describes the preparation of a quality control material (QCM) harbor sediment carried out in a specifically equipped laboratory at the University of Barcelona. The results of homogeneity and stability studies for total metal content (Cd, Cr, Cu, Ni, Pb, and Zn), extractable metal following the BCR three-step sequential extraction procedure (BCR-SEP), and total carbon content show the suitability of QCM for multi-parameter routine quality control (QC) in marine environmental laboratories.     

Synthesis and surface engineering of magnetic nanoparticles for environmental cleanup and pesticide residue analysis: A review

In recent years, water pollution and pesticide accumulation in the food chain have become a serious environmental and health hazard problem. Direct determination of these contaminants is a difficult task due to their low concentration level and the matrix interferences. Therefore, an efficient separation and preconcentration procedure is often required prior to the analysis. With the advancement in nanotechnology, various types of magnetic core–shell nanoparticles have successfully been synthesized and received considerable attention as sorbents for decontamination of diverse matrices. Magnetic core–shell nanoparticles with surface modifications have the advantages of large surface‐area‐to‐volume ratio, high number of surface active sites, no secondary pollutant, and high magnetic properties. Due to their physicochemical properties, surface‐modified magnetic core–shell nanoparticles exhibit high adsorption efficiency, high rate of removal of contaminants, and easy as well as rapid separation of adsorbent from solution via external magnetic field. Such facile separation is essential to improve the operation efficiency. In addition, reuse of nanoparticles would substantially reduce the treatment cost. In this review article, we have attempted to summarize recent studies that address the preconcentration methods of pesticide residue analysis and removal of toxic contaminants from aquatic systems using magnetic core–shell nanoparticles as adsorbents.     

A quick analytical method using direct solid sample introduction and GC-ECD for pesticide residues analysis in crops

In this work, an analytical method for GC using direct solid sample introduction was developed to tackle the problem regarding quick detection of pesticide residue in crops and large-scale screening of samples. 10 mg of the crop solid sample without sample pre-treatment was directly introduced into a modified split/splitless injector for GC analysis. A split/splitless injector was modified to quickly remove oxygen and low boiling-point matrices of the sample. The whole sampling procedure was simple and it required less than 5 min. The experimental parameters including injector-port temperature, removal of oxygen and low boiling point matrices, size and the amount of the solid sample, oven temperature program were studied. Satisfactory recoveries of 6 pesticides (methyl parathion, fenitrothion, aldrin, dieldrin, endosulfan, o,p′-DDT) were obtained in maize and rice sample. Relative standard deviation was less than 15%. Experimental results showed that the proposed method was quick and reliable for pesticide residues analysis in crops.     

A new spectroscopic tool for surface layer analysis: multiple-angle incidence resolution spectrometry

A series of application studies of infrared multiple-angle incidence resolution spectrometry (IR-MAIRS) have been reported since it was first proposed as a unique technique for analyzing molecular orientation in thin films on an optically transparent substrate, and both expected and unexpected benefits of IR-MAIRS have been revealed. In this review, cutting-edge application studies are summarized systematically, and the principle of MAIRS is explained from a new point of view.     

Multiple injection techniques for microfluidic sample handling

This paper presents an experimental and numerical investigation into electrokinetic focusing flow injection for bioanalytical applications on 1 x N (i.e., 1 sample inlet port and N outlet ports) and M x N (i.e., M sample inlet ports and N outlet ports) microfluidic chips. A novel device is presented which integrates two important microfluidic phenomena, namely electrokinetic focusing and valveless flow switching within multiported microchannels. The study proposes a voltage control model which achieves electrokinetic focusing in a prefocusing sample injection system and which allows the volume of the sample to be controlled. Using the developed methods, the study shows how the sample may be prefocused electrokinetically into a narrow stream prior to being injected continuously into specified outlet ports. The microfluidic chips presented within this paper possess an exciting potential for use in a variety of techniques, including high-throughput chemical analysis, cell fusion, fraction collection, fast sample mixing, and many other applications within the micrototalanalysis systems field.     

FT-Raman spectroscopy - analytical tool for routine analysis of diazinon pesticide formulations

FT-Raman spectroscopy based on band intensity and band area measurements, was used for the quantitative determination of diazinon in pesticide formulations. Bands at 554, 604, 631, 1562 and 2971 cm(-1) were used for calibration. Spectra were acquired by averaging 100 scans at a resolution of 4 cm(-1). Calibration curves were linear (correlation coefficients, 0.992-0.9992 and 0.99-0.999 for band intensity and band area measurements, respectively) in the range of 0.2-3.5 M for 554 and 2971 cm(-1), 0.3-3.5 M for 604 cm(-1), 0.6-3.5 M for 1562 cm(-1) and 1.0-3.5 M for 631 cm(-1) bands. Normalization of calibration curves against the 802 cm(-1) cyclohexane band improved their long term stability and minimized the effect of laser beam power fluctuations. No interference was found by commonly used surfactants and the proposed method was applied to the analysis of diazinon formulations. Results obtained compare well as indicated by the t-test, with those obtained by the HPLC reference method. Precision ranged between 0.2-7.8 and 0.1-7.2% RSD, (n=4) for band intensity and band area measurements, respectively. The proposed method is rapid, simple and safe, as toxic samples are analyzed 'as received' without sample pre-treatment, permiting the routine analysis of pesticides formulations.     

Charged particle induced X-ray analysis: A new tool in forensic science

The application of the charged particle X-ray excitation technique (CPXE) to the problem of determination of residues from gun firing is described. Preliminary results indicate that certain elements, including S, Ba, Fe, and Pb can be detected in statistically significant larger amounts on firing hands than on nonfiring hands with 90 to 98% confidence limits. Results for other elements including K, Ca, Sb, Cr, Mn, Ni, Cu, are also discussed. The simplicity on the technique, together with the number of elements detected, offers advantages over other techniques for firearm discharge residue detection.