Optimization of separation and detection conditions for the multiresidue analysis of pesticides in grapes by comprehensive two-dimensional gas chromatography–time-of-flight mass spectrometry

Aroma Clouds of Foods: A Step Forward to Unveil Food Aroma Complexity Using GC × GC

The human senses shape the life in several aspects, namely well-being, socialization, health status, and diet, among others. However, only recently, the understanding of this highly sophisticated sensory neuronal pathway has gained new advances. Also, it is known that each olfactory receptor cell expresses only one type of odorant receptor, and each receptor can detect a limited number of odorant substances. Odorant substances are typically volatile or semi-volatile in nature, exhibit low relative molecular weight, and represent a wide variety of chemical families. These molecules may be released from foods, constituting clouds surrounding them, and are responsible for their aroma properties. A single natural aroma may contain a huge number of volatile components, and some of them are present in trace amounts, which make their study especially difficult. Understanding the components of food aromas has become more important than ever with the transformation of food systems and the increased innovation in the food industry. Two-dimensional gas chromatography and time-of-flight mass spectrometry (GC × GC-ToFMS) seems to be a powerful technique for the analytical coverage of the food aromas. Thus, the main purpose of this review is to critically discuss the potential of the GC × GC-based methodologies, combined with a headspace solvent-free microextraction technique, in tandem with data processing and data analysis, as a useful tool to the analysis of the chemical aroma clouds of foods. Due to the broad and complex nature of the aroma chemistry subject, some concepts and challenges related to the characterization of volatile molecules and the perception of aromas will be presented in advance. All topics covered in this review will be elucidated, as much as possible, with examples reported in recent publications, to make the interpretation of the fascinating world of food aroma chemistry more attractive and perceptive.

In vitro assessment of pesticide residues bioaccessibility in conventionally grown blueberries as affected by complex food matrix

The aim of this study was to investigate the bioaccessibility of pesticide residues in blueberries (commercial and sample from controlled field trial) from Serbia, involving the presence of a complex food matrix and to assess the potential risk to human health. The presence of nine active substances (azoxystrobin, boscalid, fludioxonil, cyprodinil, pyrimethanil, pyridaben, pyriproxyfen, acetamiprid and thiametoxam) in initial blueberry samples was determined in concentration range from 5.15 μg/kg for thiametoxam to 187 μg/kg for azoxystrobin. Clothianidin, metabolite of thiametoxam, was not detected in any blueberry sample. However, after in vitro digestion, the content of initially detected pesticides residues was significantly decreased or it was below limit of quantification resulting in the total bioaccessibility of about 15%. Azoxystrobin, pyrimethanil and fludioxonil was quantified in digestive juice at concentrations which were about 81%, 37% and 10% less than the inital concentration, respectively. The presence of food matrix during digestion of blueberries even more severely reduced concentration of pesticide residues (total bioaccessibility was about 7%) compared to digestion without the food matrix. Only azoxystrobin was quantified after digestion with food matrix in concentration of 27 μg/kg in sample from controlled field trial and detected in two commercial samples but below the limit of quantification. Furthermore, chronic risk assessment indicated that risk is acceptable for the health of different human subpopulation groups. The current study on pesticides residues, most commonly applied on blueberries, provides for the first time an insight into their bioaccessibility under conditions that mimic physiological environment of human digestive tract.

Two-Dimensional Gas Chromatography Coupled With Mass Spectrometry in Food Analysis

The development of instrumental analytical techniques provided the opportunity for in-depth characterization of many food matrices. In particular, the use of gas chromatography coupled with mass spectrometry gives impressive results in terms of quality and authenticity testing, conducting food freshness evaluations and contamination assessments. A new variant of gas chromatography, namely two-dimensional gas chromatography (GC × GC), and various versions of mass spectrometry have been developed since last 15 years, and they still remain at the time of their renaissance. The present critical review is focused on the use of GC × GC coupled with mass spectrometry for qualitative and quantitative reasons in food analysis. It is explained how powerful analytical tool is above-mentioned technical solution. Special attention is devoted to the issues related to the development of this technique during last years in terms of key construction elements, such as modulators and MS detectors. Finally, the critical discussion on many various aspects including advantages and more important disadvantages, caused probable moderate interest of this solution, in food analytics is concerned.

Direct Immersion Solid-Phase Microextraction with Matrix-Compatible Fiber Coating for Multiresidue Pesticide Analysis of Grapes by Gas Chromatography-Time-of-Flight Mass Spectrometry (DI-SPME-GC-ToFMS)

A fast and sensitive direct immersion-solid-phase microextraction-gas chromatography-time-of-flight mass spectrometry (DI-SPME-GC-ToFMS) method for the determination of multiresidue pesticides in grapes employing a PDMS-modified PDMS/DVB coating was developed utilizing multivariate approaches for optimization of the most important factors affecting SPME performance. A comprehensive investigation of appropriate internal standards using a bottom-up approach led to the selection of suitable compounds that adequately covered a range of 40 pesticides pertaining to various classes. The validated method yielded good accuracy, precision, and sensitivity and has been successfully applied to the analysis of commercial samples. With regard to the limitations of the proposed method, the DI-SPME method did not provide a satisfactory performance toward more polar pesticides (e.g., acephate, omethoate, dimethoate) and highly hydrophobic pesticides, such as pyrethroids. Despite the challenges and limitations encountered by this method, the practical aspects of the PDMS-modified coating demonstrated here create new opportunities for SPME applied in food analysis.

Trace level determination of pyrethroid and neonicotinoid insecticides in beebread using acetonitrile-based extraction followed by analysis with ultra-high-performance liquid chromatography-tandem mass spectrometry

Beebread is among the matrices suspected of contaminating honeybee. To better understand this contamination, the study aimed to develop an efficient, sensitive and reliable analytical method for the trace analysis of pesticides in beebread. This study focuses specifically on the insecticides pyrethroids and neonicotinoids and some of their metabolites. It describes the development and validation of an original analytical approach that consists of one simple extraction method based on modified QuEChERS followed by a selective and sensitive analysis by UHPLC-MS/MS to determine the target compounds in beebread. The method was validated using a quadratic fit. RSD values below 20% were obtained, except for 5-hydroxy-imidacloprid and imidacloprid at 0.5 ng/g, which exhibited RSDs of 25% and 21%, respectively. The intra-day precision was less than 10% for many of the investigated compounds. The inter-day precision varied between 2% and 36%, depending on the compound and the concentration. The recoveries varied from 53% to 119%, with averages of 83, 81 and 77% for the extraction of beebread samples spiked at 0.5, 5 and 10 ng/g, respectively. The LOD values for all the substances were below ng/g, with the exception of 6-chloronicotinic acid (LOD=1.7 ng/g). The method was then applied to the analysis of 32 beebread samples and revealed the presence of 7 of the target substances. The most frequently detected pesticides belonged to the neonicotinoid family and were generally present at low concentrations, but in some cases exceeded 170 ng/g (acetamiprid and thiacloprid). Some pyrethroids were also detected (lambda-cyhalothrine and bifenthrine), but at very low levels.

Ability of NIRS technology to determine pesticides in liquid samples at maximum residue levels

BACKGROUND

Pesticide residues remaining on food represent a potential risk to consumer's health. Determination of these pesticide residues involves tedious procedures of analysis with regard to time and laboratory work. Near-infrared spectroscopy (NIRS) is a possible alternative to these methods. The aim of this research was to evaluate the ability of NIRS to classify two pesticides used for controlling apple fruit pests according to their concentration. Different solutions were prepared, based on the dose recommended by the pesticide producers for apple pest treatments. Spectra were acquired on a spectrophotometer from liquid samples belonging to these solutions.

RESULTS

Calibration models were developed from liquid samples, following the soft independent modelling of class analogy (SIMCA) analysis method. These models classified between 99 and 100% of the validation samples belonging to different pesticide concentration solutions even at the maximum residue limit level of these products in apple fruit.

CONCLUSIONS

NIRS technology shows a high potential for identifying pesticides in liquid samples, according to their concentration, at the levels required by the legislation.

Strategies for the multi-residue analysis of 100 pesticides by liquid chromatography-triple quadrupole mass spectrometry

Analytical strategies for screening, quantitation and confirmation of a group of 100 pesticides in fruit and vegetable samples by LC-MS and LC-MS/MS were developed. The pesticides studied belong to different chemical families of herbicides, insecticides and fungicides. A selection of some degradation products was also included. Chromatographic separation was performed using a Zorbax Eclipse XDB-C8 column (150 mm × 4.6 mm and 5 μm particle size), and gradient elution with acetonitrile-water (both with 0.1% formic acid) as mobile phase. LC-MS/MS using highly-selective selected reaction monitoring (H-SRM) acquisition mode monitoring two transitions for each compound showed to be the most sensitive methodology. Quantitation was carried out using matrix-matched standard calibration and good linearity of response was demonstrated (r>0.998). Limits of detection (by acquiring two transitions and with the ion-ratio requirements) ranged between 0.01 and 20 μg/kg were obtained. So, in general, the sensitivity achieved meets the maximum residue levels (MRLs) established by the European Union regulation for food monitoring programs. Pesticide confirmation was carried out following European Union guidelines. In order to prevent false-positives, further confirmatory strategies were proposed. LC-MS in highly-selective selected ion monitoring (H-SIM) mode with accurate mass measurement was used to obtain an orthogonal criterion (exact mass) for confirmation. Accurate mass measurements were always bellow 0.9 mDa for almost all pesticides studied (similar to those described with TOF instruments). A user reversed energy ramp (RER) product ion scan spectra library was generated by means of a data dependent analysis for routine library searching of pesticides. The combination of LC-MS/MS in H-SRM mode and the generation of the RER product ion scan spectra and library search were then used to achieve further confirmation on pesticide analysis. The LC-MS and LC-MS/MS strategies developed were successfully applied for the analysis and confirmation of pesticides in different types of fruit and vegetables samples, and examples of the screening, quantitation and confirmation of pesticides in these samples are shown in this work.

Current mass spectrometry strategies for the analysis of pesticides and their metabolites in food and water matrices

Analysis of pesticides and their metabolites in food and water matrices continues to be an active research area closely related to food safety and environmental issues. This review discusses the most widely applied mass spectrometric (MS) approaches to pesticide residues analysis over the last few years. The main techniques for sample preparation remain solvent extraction and solid-phase extraction. The QuEChERS (Quick, Easy, Cheap, Effective, Rugged, Safe) approach is being increasingly used for the development of multi-class pesticide residues methods in various sample matrices. MS detectors-triple quadrupole (QqQ), ion-trap (IT), quadrupole linear ion trap (QqLIT), time-of-flight (TOF), and quadrupole time-of-flight (QqTOF)-have been established as powerful analytical tools sharing a primary role in the detection/quantification and/or identification/confirmation of pesticides and their metabolites. Recent developments in analytical instrumentation have enabled coupling of ultra-performance liquid chromatography (UPLC) and fast gas chromatography (GC) with MS detectors, and faster analysis for a greater number of pesticides. The newly developed "ambient-ionization" MS techniques (e.g., desorption electrospray ionization, DESI, and direct analysis in real time, DART) hyphenated with high-resolution MS platforms without liquid chromatography separation, and sometimes with minimum pre-treatment, have shown potential for pesticide residue screening. The recently introduced Orbitrap mass spectrometers can provide high resolving power and mass accuracy, to tackle complex analytical problems involved in pesticide residue analysis.

MS-based analytical methodologies to characterize genetically modified crops

The development of genetically modified crops has had a great impact on the agriculture and food industries. However, the development of any genetically modified organism (GMO) requires the application of analytical procedures to confirm the equivalence of the GMO compared to its isogenic non-transgenic counterpart. Moreover, the use of GMOs in foods and agriculture faces numerous criticisms from consumers and ecological organizations that have led some countries to regulate their production, growth, and commercialization. These regulations have brought about the need of new and more powerful analytical methods to face the complexity of this topic. In this regard, MS-based technologies are increasingly used for GMOs analysis to provide very useful information on GMO composition (e.g., metabolites, proteins). This review focuses on the MS-based analytical methodologies used to characterize genetically modified crops (also called transgenic crops). First, an overview on genetically modified crops development is provided, together with the main difficulties of their analysis. Next, the different MS-based analytical approaches applied to characterize GM crops are critically discussed, and include "-omics" approaches and target-based approaches. These methodologies allow the study of intended and unintended effects that result from the genetic transformation. This information is considered to be essential to corroborate (or not) the equivalence of the GM crop with its isogenic non-transgenic counterpart.

Halogenated persistent organic pollutants and polycyclic aromatic hydrocarbons in food

During recent years, mass spectrometry (MS) and hyphenated chromatographic instrumentation and techniques have been a subject of dramatic developments, resulting in the introduction of various useful tools for the analysis of halogenated persistent organic pollutants (POPs) and polycyclic aromatic hydrocarbons (PAHs) in food and environmental matrices. This chapter describes state-of-the-art in the field of MS as a primary detection tool for the halogenated POPs and PAHs previously separated using either gas chromatography (GC) or liquid chromatography (LC). Since sample preparation practice plays a crucial role for obtaining optimal performance characteristics of a particular analytical method, a brief overview of sample extraction and clean-up procedures in the POPs/PAHs analysis is also briefly outlined.

Multiresidue pesticide analysis by capillary gas chromatography-mass spectrometry

A multiresidue pesticide method using a modified QuEChERS (Quick, Easy, Cheap, Effective, Rugged and Safe) procedure and capillary gas chromatography-mass spectrometry (GC-MS) is described for the determination of 166 organochlorine, organophosphorus, and pyrethroid pesticides, metabolites, and isomers in spinach. The pesticides from spinach were extracted using acetonitrile saturated with magnesium sulfate and sodium chloride, followed by solid-phase dispersive cleanup using primary-secondary amine and graphitized carbon black sorbents and toluene. Analysis is performed using different GC-MS techniques emphasizing the benefits of non-targeted acquisition and targeted screening procedures. Non-targeted data acquisition of pesticides in the spinach was demonstrated using GC coupled to a single quadrupole mass spectrometery (GC-MS) in full scan mode or multidimensional GC-time-of-flight mass spectrometery (GC  ×  GC-TOF/MS), along with deconvolution software and libraries. Targeted screening was achieved using GC-single quadrupole mass spectrometry in selective ion monitoring (GC-MS/SIM) mode or -tandem mass spectrometry (GC-MS/MS) in multiple reaction monitoring mode. The development of these techniques demonstrates the powerful use of GC-MS for the screening, identification, and quantitation of pesticide residues in foods.

Screening level ecological risk assessment for phenols in surface water of the Taihu Lake

A number of approaches have been proposed for screening level ecological risk assessment. In this paper, we first established a mass spectrum library including 50 phenols using retention time locking (RTL) technology and deconvolution reporting software (DRS). Distribution of phenols in surface water of the Taihu Lake was screened. Among the 22 identified phenols, 14 phenols were quantified. The concentrations of total phenols ranged 675.2-3346.1 ng L(-1). The distributions of ecological effect quotients (EEQs) of 14 phenols were characterized in terms of the exposure concentration distributions (ECDs) and species sensitivity distributions (SSDs). Those phenols with EEQs exceeding the threshold proposed by Water Environment Research Foundation of Alexandria were selected as priorities. As a result, 2-nitrophenol (2-NP), p-chloro-m-xylenol (PCMX) and pyrocatechol were determined as potential ecological risk stressors in surface water of the Taihu Lake. Results of the present study suggested that the proposed approach is feasible for the screening level ecological risk assessment.