Chemometric approach to the optimization of HS-SPME/GC–MS for the determination of multiclass pesticide residues in fruits and vegetables

A chemometric-assisted method for automatic, rapid and non-targeted detection of multi-pesticides in plant-derived foods by gas chromatography-mass spectrometry

An automatic, rapid and non-targeted detection method for multi-pesticides in plant-derived foods was developed by gas chromatography-mass spectrometry and chemometrics. In this method, a novel algorithm named moving window iterative target transformation factor analysis was proposed. Although there are challenges of peak overlapping and background interference, the retention time and corrected mass spectra of unknown pesticides can be automatically obtained through iteration calculation in the 'moving window' with reference to the pesticide mass spectral library. One mixed pesticide standard and nine varieties of plant-derived foods were investigated with the proposed method. By contrast, a fast temperature programme was used to shorten detection time compared to the standard temperature programme. For the mixed standard, the mass spectra and retention times of all 39 pesticides were successfully obtained from the overlapping signal. Furthermore, all spiked pesticides were successfully detected in plant-derived foods within 10 min using a fast temperature programme.

A convenient and effective method for determining organophosphorus pesticides in citrus fruits based on a novel dispersive solid phase extraction using UiO-66/Alg bead as the sorbent

This work presents a novel, convenient and effective method for assaying organophosphorus pesticides (OPPs) in the pulp and peel of citrus fruits. In this method, shaped UiO-66/alginate (UiO-66/Alg) beads were employed to replace the powder sorbents used in traditional dispersive solid phase extraction (d-SPE) methods. The UiO-66/Alg beads can be easily separated by only using a tweezer within 1 min, which effectively simplifies the sample pretreatment and overcomes the shortages brought by the incomplete separation of powder sorbents. Moreover, the matrix compounds can be effectively excluded by UiO-66/Alg beads, and the UiO-66/Alg beads can be reused at least 8 times. The d-SPE conditions were optimized by a single factor test. The method shows satisfactory sensitivity, accuracy and precision. Furthermore, ATR-FTIR and UV-Vis-DRS were employed to investigate the adsorption mechanism. Finally, the developed method was applied to monitor the OPPs in ten different citrus fruits.

Pesticide residues in animal-derived food: Current state and perspectives

Pesticides are widely used in the cultivation and breeding of agricultural products all over the world. However, their direct use or indirect pollution in animal breeding may lead to residual accumulation, migration, and metabolism in animal-derived foods, posing potential health risks to humans through the food chain. Therefore, it is necessary to detect pesticide residues in animal-derived food using simple, reliable, and sensitive methods. This review summarizes sample extraction and clean-up methods, as well as the instrumental determination technologies such as chromatography and chromatography-mass spectrometry for residual analysis in animal-derived foods, including meat, eggs and milk. Additionally, we perspectives on the future of this field. This information aims to assist relevant researchers in this area, contribute to the development of ideas and novel technical methods for residual detection, metabolic research and risk assessment of pesticides in animal-derived food.

Volatolomic approach by HS-SPME/GC-MS and chemometric evaluations for the discrimination of X-ray irradiated mozzarella cheese

In this work, an untargeted screening of the volatile profile of X-ray irradiated mozzarella cheese was carried out to study the possible radio-induced modifications. A Central Composite Design (CCD) for Response Surface Methodology (RSM) was employed to optimise the HS-SPME analysis of volatile organic compounds (VOCs). The optimised HS-SPME conditions, in terms of sample amount (5.0 g), extraction temperature (50 °C) and extraction time (75 min), were used to analyse non-irradiated and irradiated samples at three dose levels, 1.0, 2.0, 3.0 kGy. Partial Least Squares-Discriminant Analysis (PLS-DA) and Linear Discriminant Analysis (LDA) were applied to explore the variation of volatile profile with respect to the X-ray irradiation treatment. Both methods highlighted a high discriminant capability with excellent values of accuracy, specificity and sensitivity, demonstrating the effectiveness of the volatolomic approach to evaluate the variations induced by the treatment and allowing to select a total of 35 VOCs as potential irradiation markers.

Solid-Phase Microextraction-Gas Chromatography Analytical Strategies for Pesticide Analysis

Due to their extensive use and the globalized commerce of agricultural goods, pesticides have become a global concern. Despite the undoubtful advantages of their use in agricultural practices, their misuse is a threat to the environment and human health. Their analysis in environmental samples and in food products continues to gain interest in the analytical chemistry community as they are challenging matrices, and legal concentration limits are particularly low (in the order of ppb). In particular, the use of solid-phase microextraction (SPME) has gained special attention in this field thanks to its potential to minimize the matrix effect, while enriching its concentration, allowing very low limits of detection, and without the need of a large amount of solvents or lengthy procedures. Moreover, its combination with gas chromatography (GC) can be easily automated, making it a very interesting approach for routine analysis. In this review, advances and analytical strategies for the use of SPME coupled with GC are discussed and compared for the analysis of pesticides in food and environmental samples, hopefully encouraging its further development and routine application in this field.

Chemical Approach to the Optimization of Conditions Using HS-SPME/GC–MS for Characterization of Volatile Compounds in Eugenia brasiliensis Fruit

Grumixama (Eugenia brasiliensis Lam.) is a native fruit of the Brazilian Atlantic Forest, belonging to the Myrtaceae family, which designatesthe most significant number of species with food potential. It stands out due to its phytochemical characteristics because of the presence of polyphenols and volatile organic compounds. Volatile compounds are substances released by foods that give off an aroma and influence flavor. Solid-phase microextraction is a technique that allows for low-cost, fast, and solvent-free extraction, has an affinity for numerous analytes, and is easily coupled to gas chromatography. The objectives of this work were to evaluate the efficiency of different fibers of SPME (solid-phase microextraction) in the extraction of volatile organic compounds from grumixama pulp; optimize a method for extraction time, temperature, and sample weight; and to determine the characteristic volatile profile of this fruit. For the extraction of volatile compounds, three fibers of different polarities were used: polar polyacrylate (PA) fibers, divinylbenzene/carboxyne/polydimethylsiloxane (DVB/CAR/PDMS) semipolar fibers, and polydimethylsiloxane/divinylbenzene (PDMS/DVB). Fourteen volatile organic compounds (VOCs) were identified by DVB/CAR/PDMS, six by PA, and seven by PDMS/DVB through solid-phase microextraction in the headspace mode (SPME-HS). Considering the total number of compounds identified, regardless of the fiber used, and the optimization of the method, Eugenia brasiliensis presented sesquiterpene fractions (85.7%, 83.3%, and 85.7% of total VOCs) higher than the monoterpene fractions (14.3%, 16.7%, and 14.3%) for DVB/CAR/PDMS, PA, and PDMS/DVB, respectively in its composition. In addition, it was possible to verify that the fiber DVB/CAR/PDMS presented a better efficiency due to the larger chromatographic area observed when the grumixama pulp was subjected to conditions of 75 °C, 2.0 g, and an adsorption time of 20 min.

Rapid Screening of 352 Pesticide Residues in Chrysanthemum Flower by Gas Chromatography Coupled to Quadrupole-Orbitrap Mass Spectrometry with Sin-QuEChERS Nanocolumn Extraction

To analyze pesticide residues, GC coupled with quadrupole-Orbitrap MS (GC-Orbitrap-MS) has become a powerful tool because of its unique characteristics of accurate mass full-spectrum acquisition, high resolution, fast acquisition rates, and overcoming matrix interference. This paper presents an efficiency evaluation of GC-Orbitrap-MS for identification and quantitation in the 352 pesticide residues analysis of chrysanthemum flowers in full-scan mode. A streamlined pretreatment approach using one-step extraction and dilution was used, which provided high-throughput processing and excellent recovery. The samples were extracted using acetonitrile. The extracted solution was purified by a Sin-QuEChERS Nano column to suppress the matrix in chrysanthemum flowers and determined by GC-Orbitrap-MS. The calibration curves for the 352 pesticides obtained by GC-Orbitrap-MS were linear in the range of 0.5-200 μg·kg^-1, with the correlation coefficients higher than 0.99. The limits of detection (LODs) and the limits of quantification (LOQs) for the 352 pesticide residues were 0.3-3.0 μg·kg^-1 and 1.0-10.0 μg·kg^-1, respectively. The average recoveries in chrysanthemum flower at three levels were 95.2%, 88.6%, and 95.7%, respectively, with relative standard deviations (RSDs) of 7.1%, 7.5%, and 7.2%, respectively. Lastly, the validated method and retrospective analysis was applied to a total of 200 chrysanthemum flower samples bought in local pharmacies. The proposed method can simultaneously detect multipesticide residues with a good performance in qualitative and quantitative detection.

Counter Current Salting-out Homogenous Liquid-liquid Extraction and Dispersion Liquid-liquid Microextraction Based on the Solidification of Floating Organic Drop Followed by High-performance Liquid Chromatography for the Isolation and Preconcentration of Pesticides from Fruit Samples

BACKGROUND

Pesticides are widely used to control pests and prevent diseases in crops, including cereals, vegetables, and fruits. Due to factors such as the persistence of pesticides, bioaccumulation, and potential toxicity, the pesticide residues monitoring in foodstuffs is very important.

OBJECTIVE

In the current research, we proposed a novel approach to counter current salting-out homogenous liquid-liquid extraction (CCSHLLE) combined with dispersive liquid-liquid microextraction based on the solidification of floating organic drop (DLLME-SFO) in pesticides from aqueous samples for the isolation and preconcentration, which were evaluated prior to analysis as real samples by high-performance liquid chromatography-ultraviolet detection (HPLC-UV).

METHODS

In brief, sodium chloride was applied as a separation reagent, which is filled in a small glass column, through which a combination of an aqueous solution (here we could say as juice of fruit) and passing of acetonitrile. In this process, the droplets rose through the column and a separated layer would be formed on what has remained from aqueous phase. Following that, acetonitrile as the organic phase combined with 50.0 µL of extraction solvent. To further enrich the analytes, the mixture was injected into five milliliters of a 4% sodium chloride solution and placed in a tube for the DLLME-SFO.

RESULTS

Under optimal conditions, the dynamic linear range of 0.5-500 μg/L, extraction recovery of 65-85%, enrichment factors of 108-142, and limit of detection as 0.2-0.4 μg/L were obtained for the organophosphorus pesticides. In addition, the repeatability and reproducibility in the five replicate of the pesticides measurements (100 μg/L) are within the ranges of 3.5-5.1% and 4.5-6.3%, respectively.

Combination of solid phase microextraction and low energy electron ionisation gas chromatography-quadrupole time-of-flight mass spectrometry to meet the challenges of flavour analysis

The flavour analysis of volatile compounds remains challenging not only because of their diversity in properties and dynamic range, but also due to the high background noise from food matrix constituents. To improve sensitivity and specificity for a multiclass range of compounds, a combination of solid phase micro-extraction (SPME) devices and low energy electron ionisation (LE-EI) was proposed for the analysis of 36 volatile compounds, using coffee as a model matrix. From a pre-evaluation of devices and extraction modes, the combined use of direct immersion-stir bar sorptive extraction and headspace-thin-film SPME (SBSE-TFSPME) was selected to increase compound recovery, and further optimised for extraction temperature (88 °C) and time (110 min). Furthermore, to complement sample preparation by improving method specificity, a LE-EI technique was developed by evaluating the effect of ionisation energy, source temperature, and emission current on the formation of the diagnostic molecular ions and their preservation. This LE-EI method (15 eV, 150 °C, 0.3 μA) was validated with SBSE-TFSPME as a complete workflow in coffee matrices, and was found to possess good repeatability (intra-day RSD: 1.6-7.3 %), intermediate precision (inter-day RSD: 4.1-12.2 %), and linearity (R² > 0.98). Even for complex coffee samples, the method detection limit reached the pg/mL range (e.g. 2,4,5-trimethylthiazole was detected at 15 pg/mL). In conclusion, this study provided insights on the potential of SPME and LE-EI to improve the sensitivity and specificity of analysis for a range of volatile compounds from food and other complex matrices.

Optimization and Validation of a Headspace Solid-Phase Microextraction with Comprehensive Two-Dimensional Gas Chromatography Time-of-Flight Mass Spectrometric Detection for Quantification of Trace Aroma Compounds in Chinese Liquor (Baijiu)

The detection of trace aroma compounds in samples with complex matrices such as Chinese liquor (Baijiu) requires a combination of several methods, which makes the analysis process very complicated. Therefore, a headspace solid-phase microextraction (HS-SPME) method coupled with two-dimensional gas chromatography time-of-flight mass spectrometry (GC×GC-TOFMS) was developed for the quantitation of a large number of trace compounds in Baijiu. Optimization of extraction conditions via a series of experiments revealed that dilution of the alcohol content of 8 mL of Baijiu to 5%, followed by the addition of 3.0 g of NaCl and subsequent SPME extraction with DVB/CAR/PDMS fiber coating over 45 min at 45 °C was the most suitable. To check the matrix effects, various model Baijiu matrices were investigated in detail. The quantitative method was established through an optimized model synthetic solution, which can identify 119 aroma compounds (esters, alcohols, fatty acids, aldehydes and ketones, furans, pyrazines, sulfur compounds, phenols, terpenes, and lactones) in the Baijiu sample. The developed procedure provided high recovery (86.79–117.94%), good repeatability (relative standard deviation < 9.93%), high linearity (R² > 0.99), and lower detection limits than reported methods. The method was successfully applied to study the composition of volatile compounds in different types of Baijiu. This research indicated that the optimized HS-SPME–GC×GC-TOFMS method was a valid and accurate procedure for the simultaneous determination of different types of trace compounds in Baijiu. This developed method will allow an improved analysis of other samples with complex matrices.

One-step integrated sample pretreatment technique by gas-liquid microextraction (GLME) to determine multi-class pesticide residues in plant-derived foods

Gas-liquid microextraction technique (GLME) has been integrated with dispersive solid phase extraction to establish a one-step sample pretreatment approach for rapid analysis of multi-class pesticides in different plant-derived foods. A 50 μL of organic solvent plus 40 mg of PSA were required throughout the 5-minute pretreatment procedure. Good trueness (recoveries of 67.2 - 105.4%) and precision (RSD ≤ 18.9%) were demonstrated by the one-step GLME method, with MLOQs ranged from 0.001 to 0.011 mg kg^-1. As high as 93.6% pesticides experienced low matrix effect through this method, and the overall matrix effects (ME%) were generally better or comparable to QuEChERS. This method successfully quantified 2-phenylphenol, quintozene, bifenthrin and permethrin in the range of 0.001 - 0.008 mg kg^-1 in real food samples. The multiresidue analysis feature of GLME has been validated, which displays further potential for on-site determination of organic pollutants in order to safeguard food safety and human health.

Study on the environmental fate of three insecticides in garlic by in vivo sampling rate calibrated-solid phase microextraction-gas chromatography-mass spectrometry

Traditional sample preparation methods for insecticide analysis are laborious and fatal to living organisms. In the work, an in vivo sampling rate calibrated-solid phase microextraction-gas chromatography-mass spectrometry method was established and successfully used for in vivo sampling and quantitative determination of three insecticides (hexachlorobenzene, fipronil and chlorfenapyr) by direct exposing micron-sized fiber in living garlic. Absorption, enrichment, migration and elimination behavior of insecticides in garlic were investigated. Bioaccumulative effects with obvious tissue differences were observed to all three insecticides, especially for chlorfenapyr. Bioconcentration factors (BCFs) ranging from 0.0342 to 1.0887 were obtained, and the closer to roots, the higher BCFs. The half-life of insecticides in garlic ranged from 0.43 to 0.96 d. In the first 24 h, 55.0% - 80.3% insecticides residues in garlic were eliminated with first-order elimination kinetics. The research provides in vivo insights into the environmental fates of insecticides in complex living system with minimized organism damage.

Rapid Screening of 350 Pesticide Residues in Vegetable and Fruit Juices by Multi-Plug Filtration Cleanup Method Combined with Gas Chromatography-Electrostatic Field Orbitrap High Resolution Mass Spectrometry

A new method for screening pesticide residues in vegetable and fruit juices by the multi-plug filtration cleanup (m-PFC) method combined with gas chromatography-electrostatic field orbitrap high resolution mass spectrometry(GC-Orbitrap/MS) was developed. The samples were extracted with acetonitrile, purified with m-PFC and determined by GC-Orbitrap/MS. Qualitative analysis was confirmed by retention time, accurate molecular mass and quantitative analysis were performed with the matrix standard calibration. It could eliminate matrix interference effectively. Eight kinds of typical samples (orange juice, apple juice, grape juice, strawberry juice, celery juice, carrot juice, cucumber juice, tomato juice) were evaluated. The linear ranges of the 350 pesticides were from 5 to 500 μg/kg, with good correlation coefficients greater than 0.990. The limits of detection (LODs) were 0.3-3.0 μg/kg and the limits of quantification (LOQs) were 1.0-10.0 μg/kg. The average recoveries at three spiked levels of 10, 100, 200 μg/kg were in the range of 72.8-122.4%, with relative standard deviations (RSDs) of 2.0-10.8%. The method has effectively improved the determination efficiency of pesticide residue screening by high-resolution mass spectrometry in vegetable and fruit juices.

Microwave-Assisted Extraction Coupled with Mass Spectrometry for Determining Five Volatile Compounds from Soy Sauces

As a popular fermented condiment in oriental countries, soy sauce plays a more and more important role in modern food culture due to its unique smell and delicious taste. With the help of microwave extraction and gas chromatography-tandem mass spectrometry, the sample preparation method is aimed to determine the content of cyclohexane, benzene, toluene, chlorobenzene, and styrene in soy sauce. The method was validated by examining the linearity, accuracy, specificity, precision, the limit of detection, and quantitation. Meanwhile, three key factors have an impact on the efficiency and accuracy of the method including extracting solvent, temperature, and time which were optimized. The result shows that the recoveries of spiked analytes ranged from 80.86% to 105.71%, the relative standard deviation of intraday and interday precision was no more than 12.1% and 12.5%, and the limit of detection and quantitation were 0.25-1.00 ng/mL and 0.50-2.00 ng/mL, respectively. The results also indicated that the proposed method was a simple, reliable, and sensitive approach for the determination trace amount of five harmful volatile organic compounds from soy sauce.

Detection of Pesticide Residues in Vegetables Sold in Changchun City, China

ABSTRACT

We evaluated fresh vegetables for residues of 18 pesticides with different chemical structures, including organochlorine pesticides, organophosphorus pesticides, carbamate pesticides, and pyrethroid pesticides and estimated that the potential health risks for consumers. A total of 313 samples were collected from 12 kinds of vegetables in Changchun, the capital of Jilin Province, People's Republic of China. Pesticide residues were analyzed by gas chromatography and mass spectrometry, and the curves were highly linear at 0.01 to 1.00 μg/mL (R2 ≥ 0.99). The mean recovery rate of the pesticides was 62 to 110% (relative standard deviation of <5%). The limit of detection was 0.0001 to 0.0167 mg/kg, the limit of quantification was 0.0002 to 0.0556 mg/kg, and the overall detection rate was 28.43%. The prevalence of pesticides and of samples above the standard limit were highest in celery, the prevalence of pesticides was lowest in potatoes, and the prevalence of samples above the standard limit was lowest in cucumber. Three of the 18 pesticides were not detected: omethoate, chlorpyrifos, and fenvalerate. Among the 15 pesticides detected, the maximum risk factor of six (carbofuran, omethoate, phorate, dicofol, dimethoate, and dichlorvos) is >1, indicating possible harm to human health. Residues of a single pesticide may not adversely affect a person's health, but multiple pesticide residues could present a health risk.

HIGHLIGHTS

Review: Microextraction Technique Based New Trends in Food Analysis

Food chemistry is the study and classification of the quality and origin of foods. The identification of definite biomarkers and the determination of residue contaminants such as toxins, pesticides, metals, human and veterinary drugs, which are a very common source of food-borne diseases. The food analysis is continuously demanding the improvement of more robust, sensitive, highly efficient, and economically beneficial analytical approaches to promise the traceability, safety, and quality of foods in the acquiescence with the consumers and legislation demands. The traditional methods have been used at the starting of the 20th century based on wet chemical methods. Now it existing the powerful analytical techniques used in food analysis and safety. This development has led to substantial enhancements in the analytical accuracy, precision, sensitivity, selectivity, thereby mounting the applied range of food applications. In the present decade, microextraction (micro-scale extraction) pays more attention due to its futures such as low consumption of solvent and sample, throughput analysis easy to operate, greener, robotics, and miniaturization, different adsorbents have been used in the microextraction process with unique nature recognized with wide range applications.

Development and comprehensive HS-SPME/GC-MS analysis optimization, comparison, and evaluation of different cabbage cultivars (Brassica oleracea L. var. capitata L.) volatile components

Seven parameters of the headspace solid phase micro-extraction (HS-SPME) for extracting volatile compounds from cabbage were optimized comprehensively for the first time. A total of 75 volatiles were identified and quantified in 10 cabbage cultivars, mainly including aldehydes, hydrocarbons, esters, isothiocyanates, alcohols, ethers, nitriles and thiazoles. Dimethyl ether was the most abundant volatile. There were 24 volatiles with the odour activity values (OAVs) greater than 1 making large contributions to the cabbage flavor. Pungent aroma was the strongest odour, followed by green and fruity aromas. In short, the overall OAV of purple cabbages were generally higher than that of green cabbage. The volatile profile of 10 cabbage cultivars could be distinguished on the basis of radar fingerprint chart (RFC), hierarchical cluster analysis (HCA) and principal component analysis (PCA). Therefore, this study not only developed a feasible method to distinguish different cabbage cultivars, but also established a theoretical basis for the genetic improvement of cabbage flavor.

Headspace Solid-Phase Microextraction: Validation of the Method and Determination of Allyl Isothiocyanate Persistence in Cowpea Beans

Essential oils are widely recognized as an efficient and safe alternative for controlling pests in foods. However, a few studies have determined the persistence of these compounds in stored grains. The present study optimized and validated a fast and effective method for extraction and quantification of allyl isothiocyanate (AITC-the main component of mustard essential oil) residue in cowpea beans. It also investigated the persistence of this substance in the grains. The proposed method employs headspace solid-phase microextraction (HS-SPME) and gas chromatography with a flame ionization detector (GC/FID). For optimizing it, a central composite design (CCD) was used, where the best conditions for the extraction of the AITC were achieved using 15 min fiber exposure at 30 °C. The performance of the method was assessed by studying selectivity, linearity, limits of detection (LOD) and quantification (LOQ), precision, and accuracy. The LOD and LOQ for AITC were 0.11 and 0.33 μg kg^-1, respectively. The determination coefficient (R ²) was above 0.99. The relative recovery rate ranged from 108.2 to 114.8%, with an interday coefficient of variation below 9%. After 36 h, no residue was detected in the samples, demonstrating that the AITC has low persistence and can be safely used as a bioinsecticide for grains.

Unsupported liquid-state platform for SERS-based determination of triazophos

A highly reproducible surface-enhanced Raman scattering (SERS) unsupported liquid-state platform (ULP) was developed for accurate quantitative determination of triazophos. Herein, citrate-reduced Ag NPs suspension was concentrated and placed in a stainless steel perforated template to form the SERS ULP. The relative standard deviation of the SERS measurements was less than 5% (n ≥ 10), and the R² of the calibration curve was 0.994. The developed SERS ULP was applied for determination of triazophos in spiked agricultural products (rice, cabbage, and apple). Experiment results showed that the coefficient of variation ranged from 5.3 to 6.2% for intra-day and from 5.5 to 6.3% for inter-day (n = 3), which proved excellent SERS reproducibility. Moreover, the results were in good agreement with those from HPLC analysis. As a liquid-state SERS substrate, the highly reproducible ULP can perform precision quantitative analysis without surface modification of NPs, which is a significant improvement. This method provides a new perspective for quantitative SERS analysis of pesticide residues. Graphical abstract.

Smartphone-based enzyme-free fluorescence sensing of organophosphate DDVP

A novel fluorescence strategy based on the outstanding catalytic capability of CuS nanoparticles (CuS_NPs) has been developed for highly sensitive and specific determination of o,o-dimethyl-o-2,2-dichlorovinyl phosphate (DDVP) under enzyme-free and hydrogen peroxide (H₂O₂)-free conditions. In the presence of DDVP, CuS_NPs can catalyze non-fluorescence substratum of Amplex red (AR) into resorufin, which exhibits fluorescence emission at 584 nm under excitation at 540 nm. The sensing system exhibits outstanding specificity and only responds to DDVP and no other organophosphorus pesticides (OPs). A wide linear range is obtained from 0.0001 to 0.1 μg/mL, and the limit of detection (LOD) is 0.1 ng/mL. Furthermore, paper-based test strips have been constructed for visual detection of DDVP under ultraviolet light irradiation. By integrating a smartphone installed with Color Picker APP, point-of-care detection with quantitative determination is realized, demonstrating substantial potential applications of the as-developed assay for in situ detection. Graphical abstract.

Fiber-Sample Distance, An Important Parameter To Be Considered in Headspace Solid-Phase Microextraction Applications

To define and control the parameters which impact headspace solid-phase microextraction (HS-SPME), it is important to reach the highest level of reproducibility. The present study aims to assess, for the first time, the effect of fiber–sample distance during HS-SPME in pre-equilibrium conditions. Analyses were primarily performed on mixtures of standard volatiles compounds (alkanes, alcohols, organic acids) designed in our lab and then on various food matrices (wine, chicken, cheese, tea), repeating already published experiments. Extractions were performed varying fiber penetration depths (10–60 mm) at different times (10–60 min) and temperatures of extraction (30–80 °C). The study revealed that variation of the distance between the fiber and the sample into the vial clearly impacts the results obtained during HS-SPME when conditions are such that no equilibrium is reached in HS. For example, in wine analysis, the percentage of octanoic acid at 80 °C was higher at 40 mm (7.5 ± 0.2%) than that at 20 mm (4.4 ± 0.3%). Moreover, regardless of the extraction temperature, the lower the time of extraction, the stronger the dependence on the fiber–sample distance. Indeed, at 60 °C, the obtained response factors for octadecane at 20 and 40 mm of fiber penetration were 21.8 and 44.5, respectively, after 10 min of extraction, 54.1 and 71.0 after 30 min, and 79.4 and 82.4 after 60 min of extraction. The analyses have been here corroborated by a theoretical model based on the diffusion equation. Therefore, to improve the method robustness during HS-SPME studies, we suggest specifying the fiber penetration depth or the fiber–sample distance with the other parameters of extraction.

Effect of static-state fermentation on volatile composition in rapeseed meal

BACKGROUND

Fermented rapeseed meal has been used as an alternative protein source for animal feed, but the volatile compounds and how their contents change during fermentation have not been reported. To clarify the effect of static-state fermentation on its aroma, the volatile compounds of rapeseed meal during different stages of fermentation were analyzed using an electronic nose system and headspace solid-phase microextraction-gas chromatography-mass spectrometry.

RESULTS

The results suggested that the volatile compounds in the raw rapeseed meal, mostly hydrocarbons and some aldehydes, were lost. The levels of the volatile compounds resulting from microbial metabolism, especially pyrazines, greatly increased during fermentation. Nonanal was the dominant volatile measured in the headspace of raw rapeseed meal. However, the volatile compounds found at high concentrations in rapeseed meal after 5 days of fermentation were tetramethylpyrazine, followed by butanoic acid, benzenepropanenitrile, 2-methylbutanoic acid, trimethylamine, 2,3,5-trimethyl-6-ethylpyrazine, and 2,3,5-trimethylpyrazine.

CONCLUSION

The fermentation process could significantly change the composition and content of volatile compounds in rapeseed meal. The results may provide reference data for studies on the choice of fermentation period and formation mechanism of flavor substances in fermented rapeseed meal. © 2020 Society of Chemical Industry.

Review of pesticide residue analysis in fruits and vegetables. Pre-treatment, extraction and detection techniques

A wide variety of pesticides have been used in agriculture to increase the yield, quality and extend the storage life of crops. However, the use of pesticide has been increased now a day due to the ever-increasing population and rapid urbanization. The continuous uses of these pesticides have resulted in contamination of the environment, crops and also caused potential risk to human health. For this reason, strict regulations are developed and regulated to monitor these compounds. To date, several techniques have been developed for the extraction and detection of pesticides, from traditional to advanced detection techniques. The present study delineates a comprehensive up to date overview of the available traditional methods (gas chromatography and high-performance liquid chromatography coupled with various detector) to advanced pre-treatment (polystyrene-coated magnetic nanoparticle) and detection (sensor development and nanotechnology) techniques used in the analysis of pesticides residue in various fruits and vegetables. Also, categorization of pesticides and its toxicity have been discussed.

The accumulation profiles of terpene metabolites in three Muscat table grape cultivars through HS-SPME-GCMS

Aroma is an important parameter for table grapes and wines; terpenes are typical compounds in Muscat-type grape cultivars and can be easily perceived by humans because of their low olfactory threshold. Volatile terpenes contribute directly to the aroma character, while glycoside-bound terpenes are potential aromatic compounds and can be changed to their volatile forms via hydrolysis. With gas chromatography-mass spectrometry and a solid-phase microextraction method, an automatic data analysis platform was constructed; terpene compounds were identified and quantified from three table grape cultivars at three stages during berry development, and the raw data were deposited in MetaboLights. Terpene metabolite accumulation profiles are presented in this article for integrative analysis with the transcriptome data and phenotypic data to elucidate the important candidate genes and mechanism for terpene biosynthesis. Our method has applications in the identification and quantification of terpene compounds with very low or trace concentrations.

Key-Marker Volatile Compounds in Aromatic Rice (Oryza sativa) Grains: An HS-SPME Extraction Method Combined with GC×GC-TOFMS

The aroma of rice essentially contributes to the quality of rice grains. For some varieties, their aroma properties really drive consumer preferences. In this paper, using a dynamic headspace solid-phase microextraction (HS-SPME) system coupled to a two-dimensional gas chromatography (GC×GC) using a time-of-flight mass spectrometric detector (TOFMS) and multivariate analysis, the volatile compounds of aromatic and non-aromatic rice grains were contrasted to define some chemical markers. Fifty-one volatile compounds were selected for principal component analysis resulting in eight key-marker volatile compounds (i.e., pentanal, hexanal, 2-pentyl-furan, 2,4-nonadienal, pyridine, 1-octen-3-ol and (E)-2-octenal) as responsible for the differences between aromatic and non-aromatic rice varieties. The factors that are most likely to affect the HS-SPME efficiency for the aforementioned key-marker compounds were evaluated using a 2III5−2 fractional factorial design in conjunction with multi-response optimisation. The method precision values, expressed as % of coefficient of variation (CV), were ranging from 1.91% to 26.90% for repeatability (n = 9) and 7.32% to 37.36% for intermediate precision (n = 3 × 3). Furthermore, the method was successfully applied to evaluate the volatile compounds of rice varieties from some Asian countries.

Recent Applications and Newly Developed Strategies of Solid-Phase Microextraction in Contaminant Analysis: Through the Environment to Humans

The present review aims to describe the recent and most impactful applications in pollutant analysis using solid-phase microextraction (SPME) technology in environmental, food, and bio-clinical analysis. The covered papers were published in the last 5 years (2014–2019) thus providing the reader with information about the current state-of-the-art and the future potential directions of the research in pollutant monitoring using SPME. To this end, we revised the studies focused on the investigation of persistent organic pollutants (POPs), pesticides, and emerging pollutants (EPs) including personal care products (PPCPs), in different environmental, food, and bio-clinical matrices. We especially emphasized the role that SPME is having in contaminant surveys following the path that goes from the environment to humans passing through the food web. Besides, this review covers the last technological developments encompassing the use of novel extraction coatings (e.g., metal-organic frameworks, covalent organic frameworks, PDMS-overcoated fiber), geometries (e.g., Arrow-SPME, multiple monolithic fiber-SPME), approaches (e.g., vacuum and cold fiber SPME), and on-site devices. The applications of SPME hyphenated with ambient mass spectrometry have also been described.

Multivariate optimization of headspace solid-phase microextraction coupled to gas chromatography-mass spectrometry for the analysis of terpenoids in sparkling wines

A headspace solid-phase microextraction coupled to gas-chromatography and mass spectrometry (HS-SPME-GC-MS) was developed and validated for the determination of 26 terpenes in sparkling wines. The use of a Box-Behnken experimental design, together with the desirability function D, allowed the extraction conditions of the method to be optimized. The optimal extraction conditions were found at a dilution ratio of 2:3, the addition of 3.5 g of NaCl, an extraction temperature of 46 °C and an extraction time of 52 min, using the DVB/CAR/PDMS fibre. Afterwards, the analytical method was successfully validated in terms of linearity, matrix effect, limit of detection and quantification, precision and accuracy. To test the developed method, 35 commercial sparkling wines from different grape varieties, geographical regions and ageing times were analysed and their terpenoid profile was monitored. The use of multivariate statistical tools made it possible to highlight differences in the samples related to the terpene profile. Finally, the most important compounds involved in the discrimination of the samples were identified by means of iterative variable selection procedures.

Balls-in-tube matrix solid phase dispersion (BiT-MSPD): An innovative and simplified technique for multiresidue determination of pesticides in fruit samples

Sample preparation of complex matrices, like food samples, continues to be a challenge demanding great effort for improvements. In this study, a new technique named balls-in-tube matrix solid-phase dispersion (BiT-MSPD) is proposed based on a simplification of the conventional MSPD technique being all sample preparation performed directly in a closed extraction tube with the assistance of steel balls. An innovative method using BiT-MSPD was successfully established for the determination of 133 pesticide residues in apple, peach, pear and plum by ultra-high performance liquid chromatography with tandem mass spectrometry (UHPLC-MS/MS). Several sorbents were evaluated as solid support in different proportions with the sample. The homogenization step using mortar, glass rod or steel balls, with methanol and acetonitrile as extraction solvent, was evaluated. Vortex and ultrasound assisted extractions were also tested. Best results were obtained with C18, homogenization with steel balls, acetonitrile as solvent and ultrasound assisted extraction. Validation presented adequate trueness and precision results for the evaluated pesticides with recovery results ranging from 72 to 113% and RSD ≤ 17%. Practical limit of detection (LOD) and quantification (LOQ) for the compounds were 3 and 10 µg kg^-1, respectively. The developed method proved to be easier and faster to perform than the MSPD, considering that extraction and clean-up are performed in the same tube without the need to transfer to cartridges, recipients or to use a separate clean-up step. The proposed BiT-MSPD technique was successfully applied to fruit samples and has great potential to be applied in other matrices, like cereals and meat, since the steel balls promote an efficient sample dispersion and extraction of pesticides. The BiT-MSPD permit a fully automation of the entire sample preparation step.

ThThnated Development of a pH assisted AgNP-based colorimetric sensor Array for simultaneous identification of phosalone and azinphosmethyl pesticides

Development of simple and rapid methods for identification of pesticides, due to their broad usage and harmful effects on mammals, has been known as a critical demand. Herein, we have introduced a silver nanoparticle (AgNP) based colorimetric sensor array for simultaneous identification of Azinphosmethyl (AM) and Phosalone (PS) pesticides. In the presence of the target pesticides, unmodified AgNPs at various pHs (4.5, 5.5 and 9.5) showed different aggregation behaviors. As a result of aggregation, the color and UV-Vis spectra of AgNPs changed differentially, leading to distinct response patterns for AM and PS. The aggregation induced spectral changes of AgNPs, were used to identify AM and PS with the help of linear discriminant analysis (LDA). The applicability of the proposed sensor array was then evaluated by identifying the target pesticides in apple samples. Altogether, the developed AgNPs based colorimetric sensor array can be potentially exploited as an efficient discrimination tool in the near future for agrichemical applications.

Detection of Five Mycotoxins in Different Food Matrices in the Malaysian Market by Using Validated Liquid Chromatography Electrospray Ionization Triple Quadrupole Mass Spectrometry

Mycotoxins are common food contaminants which cause poisoning and severe health risks to humans and animals. The present study applied chemometric approach in liquid chromatography-tandem mass spectrometry (LC-MS/MS) optimization for simultaneous determination of mycotoxins, i.e., aflatoxins B1, B2, G1, and G2, and ochratoxin A. The validated quick, easy, cheap, effective, rugged, and safe (QuEChERS)-LC-MS/MS method was used to study the occurrence of mycotoxins in 120 food matrices. The recovery ranges from 81.94% to 101.67% with relative standard deviation (RSD) lesser than 11%. Through the developed method, aflatoxins were detected in raisin, pistachio, peanut, wheat flour, spice, and chili samples with concentration ranges from 0.45 to 16.93 µg/kg. Trace concentration of ochratoxin A was found in wheat flour and peanut samples which ranged from 1.2 to 3.53 µg/kg. Some of the tested food samples contained mycotoxins of above the European legal maximum limit.

Optimization of a headspace solid-phase micro-extraction method to quantify volatile compounds in plain sufu, and application of the method in sample discrimination

A rapid headspace solid-phase microextraction method was optimized to detect volatile components in three commercial plain sufu samples. The method was then used to qualify 14 aroma impact components that contribute significantly to the volatile profile in 12 commercial samples produced at three locations and laboratory-scale fermented samples aged for 3, 15, 30, and 90 days. Principal component analysis (PCA) was subsequently used to group the samples. The optimized method identified 148 volatile compounds in three commercial samples, and the concentrations of 14 aroma impact compounds varied significantly among commercial and laboratory samples. PCA confirmed that these samples could be discriminated according to their production location and aging time, thereby rendering this method a simple strategy for sample discrimination.