Capillary electrophoresis for analyzing pesticides in fruits and vegetables using solid-phase extraction and stir-bar sorptive extraction

Immunochromatographic visualization detection platform for bitertanol in foods

As a widely used fungicide in agriculture, bitertanol (BIT) significantly affects hormone regulation leading to imbalance of homeostasis in vivo, which makes it necessary to monitor BIT residues in foods. In this research, a novel hapten derivation scheme was designed by analyzing the chemical structure of BIT to prepare an anti-BIT monoclonal antibody with high affinity, specificity and sensitivity (half inhibitory concentration of 4.78 ng/mL). Subsequently, a visualized gold immunochromatographic assay (GICA) platform was established based on antigen-antibody specific recognition, with a limit of detection of 0.06 mg/kg and 0.18 mg/kg in cucumber and tomato, respectively. GICA has spiked recoveries of 84.3 %-114.1 %, determines results are not significantly different from those of LC-MS/MS, and the complex purification treatments can be reduced during the detection process. Therefore, the developed GICA is a reliable, rapid, and sensitive method for on-site rapid monitoring of BIT in foods.

Combination of microwave-assisted solvent extraction and effervescence-assisted deep eutectic solvent-based in-syringe dispersive liquid-liquid microextraction and its application in the extraction of triazine pesticides from apple samples

In the current study, combination of microwave-assisted solvent extraction combined with effervescence-assisted deep eutectic solvent-based in-syringe dispersive liquid-liquid microextraction has been developed as a new sample pretreatment method. The offered method was used for the extraction of five triazine pesticides (atrazine, propazine, cyanazine, ametryn, and simazine) from apple samples before their determination by gas chromatography-flame ionization detection. For this purpose, briefly, the apple sample was contacted with a suitable acidified extraction solvent and the mixture was exposed to microwave irradiations. Then, the supernatant was taken and mixed with a few microliters of a low-density deep eutectic solvent. The supernatant phase containing the extracted analytes was injected into sodium bicarbonate solution filled into a syringe. Consequently, the effervescence reaction occurs and the analytes were extracted into the fine droplets of extractant dispersed throughout the solution. Afterward, an aliquot of this phase was analyzed by the chromatographic system. Satisfactory outcomes including high enrichment factors (228-261) and extraction recoveries (67-87%), good repeatability (relative standard deviations equal or less than 3.2 and 5.3% for intra- and inter day precisions), and low limits of detection (0.4-0.7 ng g^-1 ) and quantification (1.4-2.3 ng g^-1 ) were acquired under the best experimental situations. This article is protected by copyright. All rights reserved.

The Use of Single Drop Microextraction and Field Amplified Sample Injection for CZE Determination of Homocysteine Thiolactone in Urine

Two cheap, simple and reproducible methods for the electrophoretic determination of homocysteine thiolactone (HTL) in human urine have been developed and validated. The first method utilizes off-line single drop microextraction (SDME), whereas the second one uses off-line SDME in combination with field amplified sample injection (FASI). The off-line SDME protocol consists of the following steps: urine dilution with 0.2 mol/L, pH 8.2 phosphate buffer (1:2, v/v), chloroform addition, drop formation and extraction of HTL. The pre-concentration of HTL inside a separation capillary was performed by FASI. For sample separation, the 0.1 mol/L pH 4.75 phosphate buffer served as the background electrolyte, and HTL was detected at 240 nm. A standard fused-silica capillary (effective length 55.5 cm, 75 μm id) and a separation voltage of 21 kV (~99 μA) were used. Electrophoretic separation was completed within 7 min, whereas the LOD and LOQ for HTL were 0.04 and 0.1 μmol/L urine, respectively. The calibration curve in urine was linear in the range of 0.1–0.5 μmol/L, with R² = 0.9991. The relative standard deviation of the points of the calibration curve varied from 2.4% to 14.9%. The intra- and inter-day precision and recovery were 6.4–10.2% (average 6.0% and 6.7%) and 94.9–102.7% (average 99.7% and 99.5%), respectively. The analytical procedure was successfully applied to the analysis of spiked urine samples obtained from apparently healthy volunteers.

Determination of homocysteine thiolactone in human urine by capillary zone electrophoresis and single drop microextraction

A simple, fast, sensitive and reproducible capillary zone electrophoresis (CZE) method with single drop microextraction (SDME) for determination of homocysteine thiolactone (HTL) in human urine has been developed and validated. The method is characterized by good precision, high accuracy, short analysis time and low consumption of reagents. The procedure consists only of few steps: urine sample centrifugation, dilution with phosphate buffer and methanol, chloroform addition onto the top of donor phase, on-line SDME in CE system, sample separation by CZE and ultraviolet detection of HTL at 240 nm. The background electrolyte was 0.1 M pH 4.75 phosphate buffer. Effective separation was achieved within 6.04 min under the separation voltage of 24 kV (~110 μA). The LOQ and LOD for HTL were 50 and 25 nM urine, respectively. The calibration curve in urine showed linearity in the range of 50-200 nM, with R² 0.9995. The intra- and inter-day precision and recovery were 4.0-14.5% (average 8.7% and 9.3%) and 92.7-115.5% (average 103.6% and 104.8%), respectively. The procedure was successfully applied to analysis of urine samples.

Feasibility of Laser-Induced Breakdown Spectroscopy and Hyperspectral Imaging for Rapid Detection of Thiophanate-Methyl Residue on Mulberry Fruit

An effective and rapid way to detect thiophanate-methyl residue on mulberry fruit is important for providing consumers with quality and safe of mulberry fruit. Chemical methods are complex, time-consuming, and costly, and can result in sample contamination. Rapid detection of thiophanate-methyl residue on mulberry fruit was studied using laser-induced breakdown spectroscopy (LIBS) and hyperspectral imaging (HSI) techniques. Principal component analysis (PCA) and partial least square regression (PLSR) were used to qualitatively and quantitatively analyze the data obtained by using LIBS and HSI on mulberry fruit samples with different thiophanate-methyl residues. The competitive adaptive reweighted sampling algorithm was used to select optimal variables. The results of model calibration were compared. The best result was given by the PLSR model that used the optimal preprocessed LIBS–HSI variables, with a correlation coefficient of 0.921 for the prediction set. The results of this research confirmed the feasibility of using LIBS and HSI for the rapid detection of thiophanate-methyl residue on mulberry fruit.

Development of Dispersive Liquid-Liquid Microextraction method combined with UV spectrophotometry for the Determination of Malathion Pesticide

A simple and novel method was developed by combination of dispersive liquid-liquid microex-traction with UV spectrophotometry for the preconcentartion and determination of trace amount of malathion. The presented method is based on using a small volume of ethylenechloride as the extraction solvent was dissolved in ethanol as the dispersive solvent, then the binary solution was rapidly injected by a syringe into the water sample containing malathion. The important parame-ters, such the type and volume of extraction solvent and disperser solvent, the effect of extraction time and rate, the effect of salt addition and reaction conditions were studied. At the optimum conditions, the calibration graph was linear in the range of 2-100 ng mL-1 of malathion with a limit of detection of 0.8 ng L-1. In addition, the enrichment factor was 30. The developed method was successfully applied for the determination of malathion pesticide in water samples

A review of biosensing techniques for detection of trace carcinogen contamination in food products

Carcinogen contaminations in the food chain, for example heavy metal ions, pesticides, acrylamide, and mycotoxins, have caused serious health problems. A major objective of food-safety research is the identification and prevention of exposure to these carcinogens, because of their impossible-to-reverse tumorigenic effects. However, carcinogen detection is difficult because of their trace-level presence in food. Thus, reliable and accurate separation and determination methods are essential to protect food safety and human health. This paper summarizes the state of the art in separation and determination methods for analyzing carcinogen contamination, especially the advances in biosensing methods. Furthermore, the application of promising technology including nanomaterials, imprinted polymers, and microdevices is detailed. Challenges and perspectives are also discussed.

Evaluation of QuEChERS sample preparation and liquid chromatography-triple-quadrupole mass spectrometry method for the determination of 109 pesticide residues in tomatoes

A multiresidue method based on modified QuEChERS (quick, easy, cheap, effective, rugged and safe) sample preparation, followed by liquid chromatography tandem mass spectrometry (LC-MS/MS) was developed and validated for the determination of 109 selected multiclass pesticides in tomatoes. The recovery yields ranged from 77.1% to 113.2%, with repeatabilities of 4.4-19.2% and within-laboratory reproducibilities of 7.1-18.4%. The limit of detections (LODs) for target analytes in tomato extract were between 0.5 and 10.8μgkg(-1), and the limit of quantifications (LOQs) were between 1.3 and 30.4μgkg(-1). The expanded measurement uncertainty was not higher than 30% for all target analytes. The method has been successfully applied to the analysis of 345 tomato samples obtained from local markets and tomato traders. Residues of acetamiprid, azoxystrobin and triadimefon were identified and measured in 9.6% of tomato samples, ranging from 0.015 to 0.37mgkg(-1).

Stir bar sorptive extraction: recent applications, limitations and future trends

Stir bar sorptive extraction (SBSE) has generated growing interest due to its high effectiveness for the extraction of non-polar and medium-polarity compounds from liquid samples or liquid extracts. In particular, in recent years, a large amount of new analytical applications of SBSE has been proposed for the extraction of natural compounds, pollutants and other organic compounds in foods, biological samples, environmental matrices and pharmaceutical products. The present review summarizes and discusses the theory behind SBSE and the most recent developments concerning its effectiveness. In addition, the main results of recent analytical approaches and their applications, published in the last three years, are described. The advantages, limitations and disadvantages of SBSE are described and an overview of future trends and novel extraction sorbents and supports is given.

Novel sorption-based methodologies for static microextraction analysis: A review on SBSE and related techniques

Stir bar sorptive extraction (SBSE) became a well-established analytical technique in the last years, for which hundreds of applications in almost all types of scientific fields can be found in the literature. In spite of the great enrichment capacity and outstanding performance to operate at the ultra-trace level, this remarkable static sorption-based method is already not quite effective for some complex systems, in particular to monitor the large group of polar organic compounds. This review aims to cover the state-of-the-art in SBSE, as well as supplying a discussion of the analytical potential of the novel adsorptive microextraction techniques, as complementary enrichment approaches, by explaining the main principles and providing technical know-how for the beginners.

Recent advances in enrichment techniques for trace analysis in capillary electrophoresis

CE is gaining great popularity as a well-established separation technique for many fields such as pharmaceutical research, clinical application, environmental monitoring, and food analysis, owing to its high resolving power, rapidity, and small amount of samples and reagents required. However, the sensitivity in CE analysis is still considered as being inferior to that in HPLC analysis. Diverse enrichment methods and techniques have been increasingly developed for overcoming this issue. In this review, we summarize the recent advances in enrichment techniques containing off-line preconcentration (sample preparation) and on-line concentration (sample stacking) to enhancing sensitivity in CE for trace analysis over the last 5 years. Some relatively new cleanup and preconcentration methods involving the use of dispersive liquid-liquid microextraction, supercritical fluid extraction, matrix solid-phase dispersion, etc., and the continued use and improvement of conventional SPE, have been comprehensively reviewed and proved effective preconcentration alternatives for liquid, semisolid, and solid samples. As for CE on-line stacking, we give an overview of field amplication, sweeping, pH regulation, and transient isotachophoresis, and the coupling of multiple modes. Moreover, some limitations and comparisons related to such methods/techniques are also discussed. Finally, the combined use of various enrichment techniques and some significant attempts are proposed to further promote analytical merits in CE.

Comparison of the selectivity of different sorbent phases for bar adsorptive microextraction--application to trace level analysis of fungicides in real matrices

Bar adsorptive micro-extraction combined with liquid desorption followed by large volume injection-gas chromatography-mass spectrometry operating in the selected-ion monitoring acquisition mode (BAμE-LD/LVI-GC-MS(SIM)) was developed for the determination of trace levels of ten fungicides (azoxystrobin, difenoconazole, metalaxyl-M, myclobutanil, penconazole, tebuconazole, flusilazole, cyprodinil, procymidone and benalaxyl) in aqueous matrices. By comparing different sorbent coatings (two activated carbons, two styrene-divinylbenzene and one modified pyrrolidone polymers) through BAμE, the latter phase showed much higher selectivity and capacity offering multiple mechanisms of interaction, even against polydimethylsiloxane by stir bar sorptive extraction. Assays performed on 25 mL of water samples spiked at the 0.8 μg/L level, yielded recoveries ranging from 100.0 to 107.8%, under optimized experimental conditions; BAμE(modified pyrrolidone) - equilibrium time: 4h (1000 rpm), pH 5.5; LD - solvent:methanol/acetonitrile (1/1), 15 min with sonification. The analytical performance showed convenient detection limits (4.0-30.0 ng/L) and excellent linear dynamic ranges (0.04-1.60 μg/L) with remarkable correlation coefficients (r(2)>0.9980). Excellent repeatability was also achieved through intraday (RSD<13.7%) and interday (RSD<9.9%) assays. By using the standard addition methodology, the application of the present analytical approach on tap and ground water, as well as, wine samples revealed good sensitivity and absence of matrix effects. The proposed method operating under floating sampling technology proved to be a suitable sorption-based static microextraction alternative to monitor fungicides in real matrices, showing to be easy to implement, reliable, sensitive, requiring low sample volume and the possibility to choose the most selective sorbent coating according to the targets of interest.

Determination of organophosphorus pesticides using dispersive liquid-liquid microextraction combined with reversed electrode polarity stacking mode-micellar electrokinetic chromatography

A rapid and sensitive method using two preconcentration techniques, dispersive liquid-liquid microextraction (DLLME) followed by reversed electrode polarity stacking mode (REPSM) was developed for the analysis of five organophosphorus pesticides (OPPs) by micellar electrokinetic chromatography (MEKC). Parameters that affect the efficiency of the extraction in DLLME and preconcentration by REPSM, such as the kind and volume of the extraction and disperser solvents, salt addition, sample matrix and injection time were investigated and optimized. Under the optimum conditions, the enrichment factors were obtained in the range from 477 to 635. The linearity of the method for parathion, azinphos and fenitrithion was in the range of 20-1000 ng mL(-1), and for malathion and diazinon in the range of 50-1000 ng mL(-1), with correlation coefficients (r(2)) ranging from 0.9931 to 0.9992. The limits of detecton (LODs) at a signal-to-noice ratio of 3 ranged from 3 to 15 ng mL(-1). The relative recoveries of five OPPs from water samples at spiking levels of 20 and 200 ng mL(-1) for parathion, azinphos and fenitrithion, and 50 and 500 ng mL(-1) for malathion and diazinon, were 69.5-103%. The proposed method provided high enrichment factors, good precision and accuracy with a short analysis time.

Universal primer-multiplex-polymerase chain reaction (UP-M-PCR) and capillary electrophoresis-laser-induced fluorescence analysis for the simultaneous detection of six genetically modified maize lines

To meet the labeling and traceability requirement of genetically modified (GM) maize and their products for trade and regulation, it is essential to develop a specific detection method for monitoring the presence of GM content. In this work, six GM maize lines, including GA21, Bt11, NK603, Bt176, Mir604, and Mon810, were simultaneously detected by universal primer-multiplex-polymerase chain reaction (UP-M-PCR), and the amplicons for the six event-specific genes as well as the endogenous Ivr gene were successfully separated by the method of capillary electrophoresis-laser-induced fluorescence (CE-LIF). The UP-M-PCR method overcame the disadvantages in conventional M-PCR, such as complex manipulation, lower sensitivity, amplification disparity resulting from different primers, etc., and in combination with CE-LIF, it obtained a high sensitivity of 0.1 ng for both single and mixed DNA samples. The established method can be widely used for the qualitative identification of the GM maize lines.

Simultaneous multiresidue analysis of 41 pesticide residues in cooked foodstuff using QuEChERS: Comparison with classical method

The principal objective of this study was to develop a simple multiresidue method involving a quick, easy, cheap, effective, rugged, and safe (QuEChERS) extraction method for the identification and quantification of 41 pesticide residues in cooked foodstuffs including cooked potatoes, radishes, and rice using GC-μECD. The analytes were subsequently confirmed via GC-MS. The results were then compared using the classical method established by the KFDA. The quantitation of individual pesticides was based on matrix-matched calibration curves with a correlation coefficient in excess of 0.993 for the 41 pesticides selected herein. Using QuEChERS, the mean recoveries ranged between 68.6 and 130.0% for the majority of the tested pesticides; however, the classical method exhibited low recoveries for dichlofluanid, tetraconazole, oxadixyl, fenbuconazloe, and paclobutrazol. After QuEChERS, the LODs and LOQs ranged between 0.004 and 0.3μg/kg and 0.0125 and 1.0μg/kg, respectively. The proposed method was applied successfully to determine the residue levels in cooked foodstuffs, and none of the samples contained detectable amounts of pesticide residues.

Application of dispersion-solidification liquid-liquid microextraction for the determination of triazole fungicides in environmental water samples by high-performance liquid chromatography

A simple, rapid and environmentally friendly method has been developed for the determination of four triazole fungicides (myclobutanil, tebuconazole, triadimenol, hexaconazole) in water samples by dispersion-solidification liquid-liquid microextraction coupled with high performance liquid chromatography-diode array detection. Several variables that affect the extraction efficiencies, including the type and volume of the extraction solvent and dispersive solvent, extraction time, effect of pH and salt addition, were investigated and optimized. Under the optimum conditions, the proposed method is sensitive and shows a good linearity within a range of 0.5-200 ng mL(-1), with the correlation coefficients (r) varying from 0.9992 to 0.9998. High enrichment factors were achieved ranging from 190 to 450. The recoveries of the target analytes from water samples at spiking levels of 1.0, 5.0 and 50.0 ng mL(-1) were between 84.8% and 110.2%. The limits of detection (LODs) for the analytes were ranged in 0.06-0.1 ng mL(-1), and the relative standard deviations (RSD) varied from 3.9% to 5.7%. The proposed method has been successfully applied for the determination of the triazole fungicides in real water samples.

Measurement of pesticide residues in peppers by near-infrared reflectance spectroscopy

BACKGROUND

Peppers are a frequent object of food safety alerts in various member states of the European Union owing to the presence in some batches of unauthorised pesticide residues. This study assessed the viability of near-infrared reflectance spectroscopy (NIRS) for the measurement of pesticide residues in peppers. Commercially available spectrophotometers using different sample-presentation methods were evaluated for this purpose: a diode-array spectrometer for intact raw peppers and two scanning monochromators fitted with different sample-presentation accessories (transport and spinning modules) for crushed peppers and for dry extract system for infrared analysis (DESIR), respectively.

RESULTS

Models developed using partial least squares-discriminant analysis (PLS2-DA) correctly classified between 62 and 68% of samples by presence/absence of pesticides, depending on the instrument used. At model validation, the highest percentage of correctly classified samples-75 and 82% for pesticide-free and pesticide-containing samples respectively-were obtained for intact peppers using the diode-array spectrometer.

CONCLUSION

The results obtained confirmed that NIRS technology may be used to provide swift, non-destructive preliminary screening for pesticide residues; suspect samples may then be analysed by other confirmatory analytical methods.

Methods for determining pesticides and polychlorinated biphenyls in food samples--problems and challenges

Determination of residual amounts of pesticides and polychlorinated biphenyls (PCBs) in food samples requires the use of specific techniques regarding sample preparation as well as instrumental analysis which should be characterized by a very low detection limit. A problem associated with the use of pesticides and PCBs is the need for controlling their residues in the environment, particularly in food, as these chemicals show a propensity to accumulate. The analysis of food samples for the presence of pesticides and PCBs brings on many difficulties because of the specificity of sample preparation consisting of multistep purification procedures of samples that contain trace amounts of an analyte. Concentration determinations of pollutants that easily dissolve in complex matrices, particularly in the presence of a large apportionment of interfering substances, pose a big challenge. Therefore, the basic step in food analysis for the presence of pesticides and PCBs is sample preparation which mainly consists of analyte enrichment and the removal of interfering substances. But all steps of the analytical procedure that include sample collection and preparation, extraction of analytes from matrix, extract purification, and final determination, are very significant; their precision and correct application have a decisive effect on the final result.