Use of neutron activation analysis and LC–ICP-MS in the development of candidate reference materials for As species determination

Arsenic (As) is widely found in marine organisms, mainly as organic arsenical compounds. With the introduction of regulations for As species in foodstuffs and for environmental control, it has become more important to quantify the amount of arsenic species present. To address this concern new reference materials (RMs) for validation and quality assurance of As speciation measurements are being developed, including a tuna fish tissue and a robalo liver tissue. Instrumental neutron activation analysis (INAA) is used in this work as a proven analytical tool for As determinations and for validating the As mass fraction determined by liquid chromatography coupled to inductively coupled mass spectrometry (LC–ICP-MS) in extracts of the candidate RMs and other fish samples including certified RMs. Various methods for the extraction of water-soluble As species were evaluated. The best results were acquired after methanol/acetone/water extraction yielding in 93 % extractable As in the tuna RM. This procedure was used for the LC–ICP-MS studies. The results demonstrate that INAA can account for 100 % of the distribution of As species in analytical processes. It complements LC–ICP-MS for the validation of the characterization of As species in the development of RMs for such species. Excellent agreement of measured results in certified RMs with the reported values confirms the validity of the applied procedures.     

Analytical Methods for Determination of Non-Nutritive Sweeteners in Foodstuffs

Sweeteners have been used in food for centuries to increase both taste and appearance. However, the consumption of sweeteners, mainly sugars, has an adverse effect on human health when consumed in excessive doses for a certain period, including alteration in gut microbiota, obesity, and diabetes. Therefore, the application of non-nutritive sweeteners in foodstuffs has risen dramatically in the last decade to substitute sugars. These sweeteners are commonly recognized as high-intensity sweeteners because, in a lower amount, they could achieve the same sweetness of sugar. Regulatory authorities and supervisory agencies around the globe have established the maximum amount of these high-intensity sweeteners used in food products. While the regulation is getting tighter on the market to ensure food safety, reliable analytical methods are required to assist the surveillance in monitoring the use of high-intensity sweeteners. Hence, it is also necessary to comprehend the most appropriate method for rapid and effective analyses applied for quality control in food industries, surveillance and monitoring on the market, etc. Apart from various analytical methods discussed here, extraction techniques, as an essential step of sample preparation, are also highlighted. The proper procedure, efficiency, and the use of solvents are discussed in this review to assist in selecting a suitable extraction method for a food matrix. Single- and multianalyte analyses of sweeteners are also described, employing various regular techniques, such as HPLC, and advanced techniques. Furthermore, to support on-site surveillance of sweeteners’ usage in food products on the market, non-destructive analytical methods that provide practical, fast, and relatively low-cost analysis are widely implemented.     

Controlling the retention in capillary LC with solvents, temperature, and electric fields

Once a suitable stationary phase and column dimensions have been selected, the retention in liquid chromatography (LC) is traditionally adjusted by controlling the mobile phase composition. Solvent gradients enable achievement of good separation selectivity while decreasing the separation time as compared to isocratic elution. Capillary columns allow use of other programming parameters, i.e. temperature and applied electric fields, in addition to solvent gradient elution. This paper presents a review of programmed separation techniques in miniaturized LC, including retention modeling and method transfer from the conventional to micro- and capillary scales. The impact of miniaturized instrumentation on retention and the limitations of capillary LC are discussed. Special attention is focused on the gradient dwell volume effects, which are more important in micro-LC techniques than in conventional analytical LC and may cause significant increase in the time of analysis, unless special instrumentation and (or) pre-column flow-splitting is used. The influence of temperature upon retention is also discussed, and applications where the temperature has been actively used for retention control in capillary LC are included together with the instrumentation utilized. Finally the possibilities of additional selectivity control by applying an electric field over a packed capillary LC column are discussed.     

Recent applications of liquid chromatography–mass spectrometry to residue analysis of antimicrobials in food of animal origin

Residual antimicrobials in food constitute a risk to human health. Although epidemiological data on the real magnitude of their adverse effects are very scarce, they indicate that food could be an important vehicle for evolution and dissemination of antimicrobial-resistant bacteria. Public health agencies in many countries rely on detection by mass spectrometry (MS) for unambiguous identification of residues of antimicrobial agents in animal food products for human consumption. The introduction of relatively inexpensive and robust liquid chromatography (LC)–MS systems has given a strong impulse to the development of confirmatory methods for the above medicines in foodstuffs. The initial part of this review, after a brief introduction into the field of antimicrobials, is dedicated to the most important EU regulations and directives for control of residues of these substances in animal products. The main attention in this review is on the sample-treatment and MS detection systems in use today for analysing the most important classes of antimicrobials in various biological matrices (milk, animal tissues, eggs, and honey). As evidenced by this review, reversed-phase LC combined with tandem MS, usually triple-quadrupole MS (QqQMS), is currently the preferred technique in most residue analysis of a single-class of antimicrobials. A recently emerging analytical strategy is that of developing methods for detecting a large variety of veterinary drugs belonging to different classes, including pesticides (multi-class residue analysis). To do this, simple and generic extraction and separation techniques applicable to a broad range of compounds differing in physical and chemical properties have been adopted. Such methods are still based mainly on LC–QqQMS. Emerging alternative MS detection systems are time-of-flight MS, which provides accurate mass of the analyte(s), or Q–linear ion trap (IT) MS that eliminates some limitations of ITMS ⁿ .     

Multidimensional detection methods for separations and their application in food analysis

The use of the multidimensional detection systems, mass spectrometry and NMR, with separation techniques is discussed with a consideration of their actual or potential application in food analysis. The features of the most commonly used interfaces for coupling liquid chromatography (LC) and mass spectrometry (MS) are briefly examined and examples from the literature on the use of LC-MS in the analysis of natural components in foodstuffs are reported. The potential capabilities for food analysis of LC-NMR, supercritical fluid chromatography (SFC)-MS and capillary electrophoresis (CE)-MS are highlighted.     

Analytical methodologies for determination of artificial sweeteners in foodstuffs

Artificial high-intensity sweeteners are used increasingly frequently for food production. The food industry tends to highlight beneficial aspects of their use (e.g., tooth friendliness, increasing the quality of life of those suffering from different forms of diabetes and the possibility of weight control without anyone sacrificing their favorite “unhealthy” drinks or snacks). However, some consumers are deeply concerned about the safety of artificial sweeteners and claim that the food industry is replacing natural beet sugar or cane sugar for purely economic reasons.Most of these food additives have a maximum usable dose or a maximum allowable concentration specified for a given type of food. In order to assure consumer safety, it is necessary to control the content of sweeteners in foodstuffs. Analytical methods (including high-performance liquid chromatography, ion chromatography, thin-layer chromatography, gas chromatography, capillary electrophoresis, flow-injection analysis, electroanalysis and spectroscopy) can determine sweeteners individually and simultaneously in mixtures. This review focuses on the application of some popular analytical procedures for determination of artificial sweeteners in food.     

Chromatographic fingerprinting: An innovative approach for food 'identitation' and food authentication – A tutorial

Fingerprinting methods describe a variety of analytical methods that provide analytical signals related to the composition of foodstuffs in a non-selective way such as by collecting a spectrum or a chromatogram. Mathematical processing of the information in such fingerprints may allow the characterisation and/or authentication of foodstuffs. In this context, the particular meaning of 'fingerprinting', in conjunction with 'profiling', is different from the original meanings used in metabolomics. This fact has produced some confusion with the use of these terms in analytical papers. Researchers coming from the metabolomic field could use 'profiling' or 'fingerprinting' on a different way to researchers who are devoted to food science. The arrival of an eclectic discipline, named 'foodomics' has not been enough to allay this terminological problem, since the authors keep on using the terms with both meanings. Thus, a first goal of this tutorial is to clarify the difference between both terms. In addition, the chemical approaches for food authentication, i.e., chemical markers, component profiling and instrumental fingerprinting, have been described. A new term, designated as 'food identitation', has been introduced in order to complete the life cycle of the chemical-based food authentication process. Chromatographic fingerprinting has been explained in detail and some strategies which could be applied has been clarified and discussed. Particularly, the strategies for chromatographic signals acquisition and chromatographic data handling are unified in a single framework. Finally, an overview about the applications of chromatographic (GC and LC) fingerprints in food authentication using different chemometric techniques has been included.     

Recent developments in microcolumn liquid chromatography.

An overview of the most recent developments in microcolumn liquid chromatography (LC) is presented. A short theoretical discussion on chromatographic dilution and extracolumn bandbroadening is given and also the recent progress and advances in column technology and instrumentation are reviewed. However, the emphasis of this review is on miniaturized sample clean-up, sample introduction techniques and on both established and more recent detection techniques for microcolumn LC. The hyphenation of miniaturized LC columns with other techniques, specifically on multidimensional chromatography and the coupling of microcolumn LC to mass spectrometry is discussed in detail. Both the on-line and automated off-line interfacing to other separation and detection techniques will also be addressed. Finally, a number of typical microcolumn LC applications are presented in order to demonstrate the potential of microcolumn LC methods in a variety of scientific areas.     

Food Analysis on Electrophoretic Microchips

One of the current trends of separation techniques in analytical chemistry is miniaturization. The aim of miniaturization is to attain better performance, shorter analysis time, and reduced reagent consumption. Capillary Electrophoresis (CE) microchips, the first generation of micro-total analysis systems, are the most used microsystems in food analysis. The scope of this review is to gather and discuss the different applications of such miniaturized devices in this field. Various analytes of food significance such as natural antioxidants, amino acids, proteins, dyes, vanilla flavors, DNA probes, heavy metals, toxins, allergens etc. have been successfully monitored using CE-microchips, either to assess food quality or to ensure food safety. Also, to deal with the high complexity of food matrices, the integration of sample preparation steps onto the chip and the use of new tools from nanotechnology for the detection step have been reported.     

Daily dietary intake of elements of nutritional and radiological importance by adult Koreans

A one day representative mixed diet of an adult Korean was collectedfrom the data based on the food intake of 108 healthy subjects between theages 20 and 50. Sampling for the Korean total diet was carried out by usinga market basket study based on the Korean standard food consumption schemereported by the Korean Nutrition Society. Average consumption frequency ofdifferent food items for a one day representative mixed diet of an adult Koreanand the amount of each item to prepare a one day Korean representative totaldiet are surveyed. The analytical methods involve both instrumental and radiochemicalneutron activation techniques developed for the determination of the elementsCs, I, Sr, Th and U in various kinds of food samples. Concentrations of traceelements including 5 important elements for radiological protection, U, Th,Cs, Sr and I in the Korean total diet and the 4 most frequently consumed Koreanfoodstuffs have been analyzed by neutron activation analysis. Detection limitsfor U, Th, Sr and I were improved to ppb levels by radiochemical separationafter neutron irradiation. Five biological NIST reference materials were alsoanalyzed for quality control of the analysis. Seventeen trace elements inthe Korean total diet and four Korean representative foodstuffs were alsoanalyzed quantitatively by instrumental neutron activation analysis.     

Challenges encountered in the analysis of phthalate esters in foodstuffs and other biological matrices

Phthalate esters are ubiquitous environmental pollutants and are recognized as environmental endocrine disruptors because of their potential to elicit reproductive and developmental toxicity. Several phthalate esters have been listed by the US Environmental Protection Agency (EPA) as chemicals of concern. Determination of concentrations of phthalate esters in foodstuffs, typically present at sub to low nanogram-per-gram concentrations (between 0.1 and 100?ng?g^?1), is essential for assessment of human dietary exposure. However, phthalate esters are commonly present as contaminants in several laboratory products, including organic solvents, that are used in sample preparation and analysis. Therefore, accurate analysis of phthalates in food samples is a challenging task. In this review, we summarize the methods available for the determination of phthalate esters in foodstuffs and report on concentrations of phthalates in foodstuffs and potential sources of contamination by phthalates in the analysis of foodstuffs. We offer suggestions to eliminate and/or reduce background levels of contamination by phthalates in the analysis of food and other biological samples. We also introduce methods that are suitable for trace analysis of phthalates in a variety of liquid and solid food samples, in particular, a liquid–liquid extraction method for removal of lipids from food samples, because these can substantially reduce background levels of phthalates in the analytical procedure.     

3-MCPD in food other than soy sauce or hydrolysed vegetable protein (HVP)

This review gives an overview of current knowledge about 3-monochloropropane-1,2-diol (3-MCPD) formation and detection. Although 3-MCPD is often mentioned with regard to soy sauce and acid-hydrolysed vegetable protein (HVP), and much research has been done in that area, the emphasis here is placed on other foods. This contaminant can be found in a great variety of foodstuffs and is difficult to avoid in our daily nutrition. Despite its low concentration in most foods, its carcinogenic properties are of general concern. Its formation is a multivariate problem influenced by factors such as heat, moisture and sugar/lipid content, depending on the type of food and respective processing employed. Understanding the formation of this contaminant in food is fundamental to not only preventing or reducing it, but also developing efficient analytical methods of detecting it. Considering the differences between 3-MCPD-containing foods, and the need to test for the contaminant at different levels of food processing, one would expect a variety of analytical approaches. In this review, an attempt is made to provide an up-to-date list of available analytical methods and to highlight the differences among these techniques. Finally, the emergence of 3-MCPD esters and analytical techniques for them are also discussed here, although they are not the main focus of this review.     

Antibiotics in food: Legislation and validation of analytical methodologies

In this paper, European food safety legislation is presented, and special attention is devoted to monitoring residues of veterinary drugs in foodstuffs of animal origin. After a short review of the state of the art of analytical methodology for antibiotic residue analysis, the paper focuses on validation of analytical methods, with Decision 657/2002/EC as reference document. Finally, the main issues of the quality control of the analytical data, i.e. analysis of reference materials and participation in proficiency tests, are briefly addressed.     

Food safety assurance using methods of chemical analysis

A review of state-of-the-art methods of sample preparation and chemical analysis for the control of contaminants in foodstuffs and food raw materials is presented. The main achievements and performance characteristics of methods for the determination of pesticides and veterinary drugs, their metabolites, natural toxins, trace amounts of chemical elements, first of all toxic, allergens, food additives, and contaminants from packaging materials in foodstuffs and for the identification of falsifications by methods of chemical analysis are considered.     

Radioanalytische verfahren zur bestimmung des übertritts von packstoffbestandteilen in nahrungsmittel

The quantitative determination of the transfer of substances in the system packaging material/foodstuff is essential for the protection of the consumer and with respect to food regulations. The analytical difficulties occurring can be overcome by using food simulants and radio indicators. With the help of the radio tracer techniques described it is possible to determine the migration of an individual component of the packaging material into liquid and solid foodstuffs or their simulants. The methods show a high detection sensitivity; other substances do not interfere. This is accomplished by incorporating a radio indicator with the same chemical structure as the packaging-material component under consideration into test films or test sheets under conditions actually encountered in practice. The radio indicator must be evenly distributed in the test material. Then, parts of the radioactive test films or sheets are brought in one- or two-sided contact with the foodstuffs or their simulants using newly developed extraction and migration cells. The extracted or migrated amounts of the packaging material component are calculated from the radioactivities migrated into the contact media under the test conditions given. As an example for the application of these radio tracer techniques, investigations into the migration behaviour of the organotin stabilizer di-n-octyltin-2-ethyl-hexyl-dithioglycolate in the system rigid PVC/edible fat or test fat resp. are described. For the determination of the total components migrating from a packaging material into foodstuffs, a radio tracer method was developed making use of a¹⁴C-labelled standard triglyceride mixture—the fat simulant HB 307—¹⁴C: therefore, the sample of the packaging material is weighed before and after storage in the fat simulant HB 307—¹⁴C and the content of simulant in the stored sample is determined radioanalytically. The so-called global migrate equals the difference in weight of the sample of packaging material before and after storage in the simulant, provided, the amount of simulant absorbed by the test specimen has been subtracted previously from the weight of the stored sample. The efficiency of this method is demonstrated by determinations of the global migrates of polyvinyl chloride films containing different amounts of plasticizers and the dependence of the mean error of the single determination on the amount of global migrate is discussed.      

Pectin, a versatile polysaccharide present in plant cell walls

Pectin or pectic substances are collective names for a group of closely associated polysaccharides present in plant cell walls where they contribute to complex physiological processes like cell growth and cell differentiation and so determine the integrity and rigidity of plant tissue. They also play an important role in the defence mechanisms against plant pathogens and wounding. As constituents of plant cell walls and due to their anionic nature, pectic polysaccharides are considered to be involved in the regulation of ion transport, the porosity of the walls and in this way in the control of the permeability of the walls for enzymes. They also determine the water holding capacity. The amount and composition of pectic molecules in fruits and vegetables and other plant produce strongly determine quality parameters of fresh and processed food products. Pectin is also extracted from suitable agro-by-products like citrus peel and apple pomace and used in the food industry as natural ingredients for their gelling, thickening, and stabilizing properties. Some pectins gain more and more interest for their health modulating activities. Endogenous as well as exogenous enzymes play an important role in determining the pectic structures present in plant tissue, food products, or ingredients at a given time. In this paper functional and structural characteristics of pectin are described with special emphasis on the structural elements making up the pectin molecule, their interconnections and present models which envisage the accommodation of all structural elements in a macromolecule. Attention is also given to analytical methods to study the pectin structure including the use of enzymes as analytical tools.     

Applications of single-drop microextraction in analytical chemistry: A review

Single-drop microextraction (SDME) has been recognized as one of the simple miniaturized sample preparation tools for the isolation and preconcentration of several analytes from a complex sample matrix. In this review, we explored the applications of SDME coupled with various analytical techniques (spectroscopy, chromatography, and mass spectrometry) for the analysis of organic molecules, inorganic ions, and biomolecules from various sample matrices including food, environmental, clinical, pharmaceutical, and industrial samples. Also, it summarizes the use of nanoparticles in SDME combined with various analytical tools for the rapid analysis of several trace-level target analytes. An overview of ionic liquids, deep eutectic solvents, and SUPRAS, which improved the selectivity and sensitivity of various analytical techniques toward several analytes, as promising extracting solvent systems in SDME is also included. Finally, discussed the impressive analytical features and future perspectives of SDME in this review article.     

Food safety measurement issues: way forward

Ensuring food safety (FS) is a persistent concern frequently faced by many countries. Safeguarding the quality of food that is fit for human consumption is the primary responsibility of the governmental regulatory agencies. For most part, agro-industries and food processors assume voluntary leadership for producing safe food. However, in the event of FS breach, the regulatory responsibility kicks into identify and rectify the situation. Notwithstanding whether it is the regulator or the industry that institutes the remedial action (e.g. improved hygiene and refined agricultural and manufacturing practices), the role of laboratory measurements is central in safeguarding the integrity of a functioning FS system. There are many analytical tools available to implement this task, such as validated analytical methods, natural matrix reference materials, field tested monitoring systems (proactive assessment) and effective surveillance systems (constant vigilance to prevent repeat safety violations). Way forward: existing FS tools are insufficient and should be strengthened with innovative approaches. Examples are: assembling swift intervention logistics to face FS breaches; rapid response systems including communication; robust metrology based measurement systems located at strategic locations in the country; and inter-disciplinary human resource to match the need for capacity development. These issues are discussed.     

Electrochemical Peptide-Based Sensors for Foodborne Pathogens Detection

Food safety and quality control pose serious issues to food industry and public health domains, in general, with direct effects on consumers. Any physical, chemical, or biological unexpected or unidentified food constituent may exhibit harmful effects on people and animals from mild to severe reactions. According to the World Health Organization (WHO), unsafe foodstuffs are especially dangerous for infants, young children, elderly, and chronic patients. It is imperative to continuously develop new technologies to detect foodborne pathogens and contaminants in order to aid the strengthening of healthcare and economic systems. In recent years, peptide-based sensors gained much attention in the field of food research as an alternative to immuno-, apta-, or DNA-based sensors. This review presents an overview of the electrochemical biosensors using peptides as molecular bio-recognition elements published mainly in the last decade, highlighting their possible application for rapid, non-destructive, and in situ analysis of food samples. Comparison with peptide-based optical and piezoelectrical sensors in terms of analytical performance is presented. Methods of foodstuffs pretreatment are also discussed.