Comparison of solid-phase microextraction and stir bar sorptive extraction for determining six organophosphorus insecticides in honey by liquid chromatography–mass spectrometry

Sorption/Desorption and Kinetics of Atrazine, Chlorfenvinphos, Endosulfan Sulfate and Trifluralin on Agro-Industrial and Composted Organic Wastes

The use of pesticides presents a risk to terrestrial and aquatic ecosystems. For this reason, the development of strategies to prevent and restore pollution is of the greatest interest, including the adsorption to organic matter. The aim of the present study was to investigate the sorption/desorption and kinetics of atrazine, chlorfenvinphos, endosulfan sulfate, and trifluralin onto several raw organic wastes by batch experiments. Three kinetic models were used to fit the obtained sorption kinetics data and two to fit the obtained adsorption isotherm data; both the Freundlich and pseudo-second-order kinetic models described the sorption isotherms well. The desorption study revealed hysteresis in all cases, showing strong, and not completely reversible, adsorption in most cases, with the exception of atrazine-sawdust and chlorfenvinphos-sawdust and chicken manure combinations, for which responses were weak and irreversible. The best kinetic, adsorption and desorption constants were achieved for the hydrophobic pesticides. With respect to sorption-desorption rates, orujillo was found to be the best adsorbent for atrazine, while composted urban solid waste was more suitable for trifluralin and endosulfan sulfate. Sorption constants and simple correlations indicated that, not only the organic matter content, but also the nature of the organic matter itself, and the pesticide and adsorbent properties, determine pesticide sorption-desorption. The use of wastes as efficient and cheap adsorbents for reducing the risk of pesticide pollution is proposed.

Development of magnetic solid phase extraction using magnetic amphiphilic polymer for sensitive analysis of multi-pesticides residue in honey

A sensitive and time-saving method for the determination of multi-pesticide residues in honey was developed using magnetic solid phase extraction (MSPE) coupled with liquid chromatography-tandem mass spectrometry (LC-MS/MS). Magnetic polymer (N-vinyl pyrrolidone-divinyl benzene) (MVP-DB) was fabricated and employed as the adsorbent for extraction and enrichment of multi-pesticide residues in honey. MVP-DB contains lipophilic benzene ring, divinyl group, and hydrophilic pyrrolidone group. The good hydrophilic and hydrophobic structure of MVP-DB not only ensures sufficient dispersion in honey samples, but also enhances the ability to enrich target analytes. The predominant factors affecting the recoveries of analytes were systematically investigated, affording a rapid and highly efficient MSPE method. Under the optimal conditions, the method was verified, including the recovery, precision, linearity, sensitivity, and matrix effects. The results displayed that these pesticides showed good linearity in the range of 2-250 µg L^-1. The MLOQs were 0.5 µg kg^-1. The recoveries of pesticides in honey at the pre-spiked concentrations of 0.5-25 µg kg^-1 were 61.6%-112% with RSDs less than 18.2%. Hence, the developed method displayed good application prospect for the determination of multi-pesticide residues in honey samples.

Simultaneous Detection of Multiple Plant Growth Regulator Residues in Cabbage and Grape Using an Optimal QuEChERS Sample Preparation and UHPLC-MS/MS Method

BACKGROUND

At present, PGRs are widely used in agricultural and forestry production in the world, PGRs, like the traditional pesticides have certain toxicity, naively excessive applied them will cause the acute and chronic poisoning of humans and animals, potential harm to human health.

OBJECTIVES

In order to assess, prevent and control the residues of plant growth regulators (PGRs) in fruits and vegetables, a set of easy, sensitive, quick, cheap, effective, reliable and safe analytical method that simultaneously detects multiple PGRs residues is urgently needed for the inspection departments of agricultural product's quality safety.

METHODS

In this study, grape (representative of fruit) and cabbage (representative of vegetable) were used as the detected objects. The 30 commercial products residues of PGRs in both were detected with the ultra-high performance liquid chromatography-tandem mass spectrometric (UHPLC-MS/MS) method based on the optimized chromatographic conditions, mass spectrometry and preparation conditions (extraction solvent and cleanup conditions). Grape and cabbage samples were extracted by acetonitrile containing 5% (v/v) acetic acid, dehydrated by salt package, purified by QuEChERS method, ionized by electrospray (ESI) under positive and negative ion switching mode, detected by multi-reactions monitoring (MRM) and quantification by external standard method of matrix matching standard curve.

RESULTS

The results showed that methanol was selected as the strong elution phase. The methanol-0.1% formic acid-5 mmol/L ammonium acetate solution was selected as the best mobile phase. The optimal extraction solvent was acetonitrile containing 5% acetic acid. PSA cleanup could meet the determination requirements of PGRs residues. The developed method for 30 commercial products of PGRs such as betaine showed excellent linearity in 1∼500 μg/kg, 10∼1000 μg/kg, ∼500 μg/kg, ∼2000 μg/kg, and 100∼10000 μg/kg (R ≥ 0.98). At the 0.001 mg/kg (0.01 mg/kg), 0.05 mg/kg, 0.20 mg/kg and 1.00 mg/kg additive concentrations, the average addition standard recovery of 30 commercial products of PGRs were 61%∼132% with the relative standard deviations (RSD) of 1%∼14%, the LOQwere confirmed 1.0-100 μg/kg through the actual addition values of samples.

CONCLUSIONS

The results demonstrated that the optimized "QuEChERS-UHPLC-MS/MS method" is a set of simple, rapid, sensitive, accurate, efficient, economical and safe detection method that simultaneously detected the residues of more PGRs in fruits and vegetables through one time sample preparation for their high-throughput rapid quantitative screening and confirmation; it is characterized by wide coverage of detecting PGRs types, simple and convenient preparation and small amount of solvent, and which can provide the technical supports for the supervision of PGRs residues in fruits and vegetables.

HIGHLIGHTS

Based on the facts mentioned above, the optimizations of extraction solvent screening, different ratio of various purification packings in QuEChERS method and UPLC-MS conditions were conducted and the indexes of method such as precision, sensitivity and recovery rate were investigated in order to establish an simple, quick, sensitive, cheap, efficient, reliable and safe QuEChERS-UPLC-MS/MS method for simultaneously detecting the 30 kinds of PGRs residues in fruits and vegetables a set of method with simultaneously detecting 30 kinds of PGRs; which shall meet the high throughput determination of multiple PGRs residues in fruits and vegetables and can also provide the technical references for related compounds residues detection of other matrix.

Analytical Extraction Methods and Sorbents' Development for Simultaneous Determination of Organophosphorus Pesticides' Residues in Food and Water Samples: A Review

Extensive use of organophosphorus pesticides in agriculture leads to adverse effects to the environment and human health. Sample preparation is compulsory to enrich target analytes prior to detection as they often exist at trace levels and this step is critical as it determines the concentration of pollutants present in samples. The selection of a suitable extraction method is of great importance. The analytical performance of the extraction methods is influenced by the selection of sorbents as sorbents play a vital role in the sensitivity and selectivity of an analytical method. To date, numerous sorbent materials have been developed to cater to the needs of selective and sensitive pesticides' detection. Comprehensive details pertaining to extraction methods, developed sorbents, and analytical performance are provided. This review intended to provide a general overview on different extraction techniques and sorbents that have been developed in the last 10 years for organophosphorus pesticides' determinations in food and water samples.

Carbon aerogel-based solid-phase microextraction coating for the analysis of organophosphorus pesticides

The current study is focused on the in situ synthesis of a carbon aerogel (CA)-based solid-phase microextraction (SPME) fiber coating on stainless steel wire and evaluation of the suitability of CAs as SPME coating materials for the analysis of selected organophosphorus pesticides (OPPs) contained in environmental samples. A CA-based coating was obtained by pyrolyzing organic aerogels, which were prepared by the sol-gel polymerization of formaldehyde and 5-methylresorcinol, an oil shale processing by-product. The results demonstrated, for the first time, the in situ synthesis of a CA-based SPME fiber coating on stainless steel wire and its suitability for the extraction and preconcentration of six OPPs. Main parameters affecting the extraction efficiency were investigated and optimized. The direct immersion (DI)-SPME procedure combined with gas chromatography-mass spectrometry (GC-MS) for the simultaneous analysis of selected OPPs was successfully applied to the efficient and sensitive determination of analytes of interest in environmental matrices of honey and natural water samples. The developed CA-coated SPME fiber showed good linearity (R² = 0.981-0.994), low detection limits (0.11-0.83 μg L^-1) and satisfactory single fiber and fiber-to-fiber reproducibilities (8.8-12.3%, n = 5 and 11.4-17.2%, n = 3). The performance of the CA-coating was compared with that of commercially available SPME fiber coatings.

Comparison of volatile trapping techniques for the comprehensive analysis of food flavourings by Gas Chromatography-Mass Spectrometry

Trapping volatiles is a convenient way to study aroma compounds but it is important to determine which volatile trapping method is most comprehensive in extracting the most relevant aroma components when investigating complex food products. Awareness of their limitations is also crucial. (Un)targeted metabolomic approaches were used to determine the volatile profiles of two commercial flavourings. Four trapping techniques were tested as was the addition of salt to the mixture. Comprehensiveness and repeatability were compared and SBSE proved particularly suitable for extracting components such as polysulfides, pyrazines and terpene alcohols, and provided an overall broader chemical spectrum. SPME proved to be more suitable in extracting sesquiterpenes and DHS in extracting monoterpenes. Adding salt to the sample had only quantitative effects on volatiles as detected by SPME. These results help clarify the advantages and limitations of different trapping techniques and hence deliver a valuable decision tool for food matrix analysis.

Distribution of POPs, pesticides and antibiotic residues in organic honeys from different production areas

Demand for honey is increasing, especially if it is organic and if its nutritional properties are linked to untreated environments in order to guarantee quality for health. Sources of contamination of honey can be divided into environmental and apicultural. Therefore, the distribution of persistent organic pollutants, pesticides and antibiotic residues from geographical areas with different contamination sources (high anthropic impact, intensive farming, husbandry and low anthropic impact) was investigated in order to confirm the potential transfer of xenobiotics into the supply chain and to give beekeepers tools for the selection of areas dedicated to organic production. The presence of polychlorinated biphenyls, polybrominated diphenyl ether and polycyclic aromatic hydrocarbons was confirmed, not only in proximity to highly urbanised centres, where the concentrations were higher, but in all environment contexts, confirming their ubiquity. No antibiotics or neonicotinoids were detected in 95 organic honeys, demonstrating the absence of apicultural treatments and consequently the good quality of honey of different areas. These results are important due to the undefined regulatory European situation on honey antibiotic limits.

The optimization and establishment of QuEChERS-UPLC-MS/MS method for simultaneously detecting various kinds of pesticides residues in fruits and vegetables

OBJECTIVES

The quality safety supervision and test of agricultural products urgently need a very excellent analytical method with simultaneously detecting many components in order to assess, prevent and control pesticide residues.

METHODS

In this research, three fruits and three vegetables produced in Shanghai were selected as the materials, 54 pesticide residues were detected with the ultra-high performance liquid chromatography-tandem mass spectrometric (UPLC-MS/MS) method on the basis of optimized QuEChERS method according to different materials properties.

RESULTS

The results showed that: all samples were directly extracted by acetonitrile containing 1% (v/v) acetic acid; complex matrix samples were purified by a mixed sorbent of 300mg MgSO₄+100mg PSA+100mg C18+0.01g Carb, general matrix samples didn't add Carb, simple matrix samples such as watermelon directly filmed; Chromatographic column was ZORBAX Eclipse Plus-C18 column (3.0mm×150mm, 3.5μm) at 40°C, the methanol-water of mobile phase at a flow rate of 0.45mL/min by a gradient elution contained 0.1% formic acid and 5mmol/L ammonium acetate and the injection volume was 1μL. With switching electrospray ion source polarity, [M-H]^- and high sensitive [M+Na]^＋were respectively the precursor ions of eight pesticides and avermectin, [M+H]^＋ was those of the else 45 pesticides. The detection parameters of multi-reactions monitoring (MRM) with simultaneously positive and negative ions (electron multiplier voltage was 200V) scanning were set as follows: the 310.3kPa of nebulizer pressure, the 300°C of drying gas temperature, the 7L/min of drying gas flow, the 3000V and 3500V of respectively capillary positive and negative voltage. With the optimized method, the calibration curves of 54 pesticides were better linear in 15-500μg/kg (r ≥0.988), the average adding standard recovery rates of 54 pesticides were 73.2%-134.3% except pymetrozine and cyromazine with the relative standard deviations (RSD) of 1.0%-13.8%; the limit of detection (LOD) under three times signal-to-noise ratio (S/N) and limit of quantitative (LOQ) under 10 times S/N were respectively confirmed 0.003-2.000μg/kg and 0.01-6.67μg/kg.

CONCLUSIONS

The results demonstrated that the optimized "QuEChERS-UPLC-MS/MS method" was a simple, rapid, sensitive, accurate, efficient, economical and safe method that simultaneously detected multiple pesticide residues through one time sample treatment; It had some advantages such as more pesticides per detection, simple and convenient pretreatment and less solvent dosage to be suitable for the quick high-throughput quantitative screening and confirmation of pesticide residues in fruits and vegetables.

Portable Agrichemical Detection System for Enhancing the Safety of Agricultural Products Using Aggregation of Gold Nanoparticles

Organophosphorus (OP) and triazole chemicals have been commonly used as insecticides and fungicides to protect agricultural foods from harmful insects and fungi. However, these agrichemicals sometimes remain after distribution and can cause serious health and environmental issues. Therefore, it is essential to detect OPs and triazole chemicals in agricultural products. Nowadays, many detection techniques for OPs and triazole chemicals are expensive and time-consuming and require highly trained technicians. Thus, particularly rapid, simple, and sensitive detection methods are in demand for on-site screening of agrichemicals. Gold nanoparticles (AuNPs) have been utilized for applications in analytical assays and real-time monitoring in the biosensor field because of their biocompatibility and outstanding size-dependent optical properties. In this study, we used AuNPs as a detection probe, which have a size of 17 nm in diameter, a red color, and the absorbance peak at 520 nm. When imidazole was added to AuNPs mixed with the agrichemicals, the AuNPs aggregated and their colors changed to purple, causing the appearance of a new peak at 660-670 nm, which could be measured within approximately 20 s. Moreover, we developed a novel device for multiple agrichemical detections using an AuNP-aggregation-based spectrometric detection system. This portable device is light, simple, fast, and highly sensitive as well as selective. With this system, agrichemical residues can be easily detected on the spot at a low cost and in a short reaction time.

Development of a stir bar sorptive extraction method for the determination of volatile compounds in orange juices

A stir bar sorptive extraction method for the determination of volatile compounds in orange juices was developed. The extraction variables were optimized using a reduced two-level factorial screening design (2(5-1) ), and the most suitable analytical conditions for the extraction of the studied compounds were: sample volume 10 mL, extraction time 60 min, stirring speed 1800 rpm, NaCl amount 30% (weight/volume), and twister length 10 mm. The optimized method was further validated, obtaining good linearity and detection and quantification limits low enough to correctly determine the studied compounds. As well, for most of the studied compounds precision and recovery values were good. Several orange juice samples (squeezed and commercial) were extracted following the optimized extraction method and analyzed by gas chromatography coupled to mass spectrometry detection. The method has proven to be suitable for the determination of the aroma of orange juice, of which limonene was the major volatile compound in all the studied samples.

Simultaneous preconcentration of polar and non-polar organophosphorus pesticides from water samples by using a new sorbent based on mesoporous silica

A new mesoporous silica based on the sol-gel material cyanopropyltriethoxysilane (CNPrTEOS) was successfully synthesized by the hydrolysis and condensation of CNPrTEOS in the presence of ammonium solution as catalyst and methanol as solvent. It was used as a solid-phase extraction sorbent for the simultaneous extraction of three organophosphorus pesticides, namely, polar dicrotophos and non-polar diazinon and chlorpyrifos. Analysis was performed using high-performance liquid chromatography with UV detection. CNPrTEOS was characterized by FTIR spectroscopy, field-emission scanning electron microscopy and nitrogen gas adsorption. The surface area and average pore diameter of the optimum sol-gel CNPrTEOS are 379 m(2) /g and 4.7 nm (mesoporous), respectively. The proposed solid-phase extraction based on CNPrTEOS exhibited good linearity in the range of 0.8-100 μg/L, satisfactory precision (1.15-3.82%), high enrichment factor (800) and low limit of detection (0.072-0.091 μg/L). The limits of detection obtained using the proposed solid-phase extraction method are well below the maximum residue limit set by European Union and are also lower (13.6-48.5×) than that obtained by using a commercial CN-SPE cartridge (0.98-4.41 μg/L). The new mesoporous sol-gel CNPrTEOS showed promising alternative as SPE sorbent material for the simultaneous extraction of polar and non-polar organophosphorus pesticides.

Simultaneous Detection of Fenitrothion and Chlorpyrifos-Methyl with a Photonic Suspension Array

A technique was developed for simultaneous detection of fenitrothion (FNT) and chlorpyrifos-methyl (CLT) using a photonic suspension array based on silica colloidal crystal beads (SCCBs). The SCCBs were encoded with the characteristic reflection peak originating from the stop-band of colloidal crystal. This approach avoids the bleaching, fading or potential interference seen when encoding by fluorescence. SCCBs with a nanopatterned surface had increased biomolecule binding capacity and improved stability. Under optimal conditions, the proposed suspension array allowed simultaneous detection of the selected pesticides in the ranges of 0.25 to 1024 ng/mL and 0.40 to 735.37 ng/mL, with the limits of detection (LODs) of 0.25 and 0.40 ng/mL, respectively. The suspension array was specific and had no significant cross-reactivity with other chemicals. The mean recoveries in tests in which samples were spiked with target standards were 82.35% to 109.90% with a standard deviation within 9.93% for CLT and 81.64% to 108.10% with a standard deviation within 8.82% for FNT. The proposed method shows a potentially powerful capability for fast quantitative analysis of pesticide residues.

Fragmentation of toxicologically relevant drugs in negative-ion liquid chromatography-tandem mass spectrometry

Negative-ion LC-MS analysis of drugs is applied far less frequently than positive-ion LC-MS. Data on the interpretation of negative-ion MS-MS spectra are even more scarce. Therefore, following the recent review on the class-specific fragmentation of toxicologically relevant compounds in positive-ion MS-MS, it was decided to perform a similar study in negative-ion MS-MS. To this end, a set of over 500 negative-ion MS-MS spectra was collected from three libraries applied in toxicological general unknown screening and systematic toxicological analysis. The compounds involved were classified by chemical and therapeutic class. The MS-MS spectra were manually interpreted and relevant interpretation data were searched for in the scientific literature. The emphasis in the discussion is on class-specific fragmentation, because discussing fragmentation of all individual compounds would take far too much space. Negative-ion MS-MS fragmentation is discussed for a wide variety of toxicologically relevant compounds, including dihydropyridine calcium channel blockers, diuretics, barbiturates, anti-inflammatory drugs, anti-diabetics, sulfonamide and betalactam antibiotics, and a number of classes of pesticides.

Undesirable sulphur and carbonyl flavor compounds in UHT milk: a review

Ultra High Temperature (UHT) processing leads to the formation of "cooked" and "flat" flavors in milk. These undesirable notes occur due to the volatile formation of a variety of sulphur containing compounds, methyl ketones and aliphatic aldehydes, derived from the constituents of the milk's matrix during thermal processing and storage. The "cooked" flavor of UHT milk is associated with the presence of a variety of sulphur containing compounds while the "stale" flavor is characterized by the dissipation of these sulphur volatiles and an increase of the formation and presence of both methyl ketones and aliphatic aldehydes over time. The extent to which the individual volatiles contribute to the overall flavor of UHT milk is not clear. The proposed formation of these volatiles, that is, the methods to control the intensity of "cooked" and "stale" flavors associated with UHT milk and extraction techniques for the isolation of these volatiles from milk, have been reviewed.