Sample preparation food contaminants

During the last few years, miniaturization has become a dominant trend in the analysis of low-level contaminants in food and environmental samples. This has resulted in a significant reduction in the volume of hazardous and expensive solvents. Typical examples of miniaturization in sample preparation techniques are micro liquid/liquid extractions (in-vial) and solvent-free techniques such as solid-phase microextraction (SPME). Combined with state-of-the-art analytical instrumentation, this trend has resulted in faster analyses, higher sample throughputs and lower solvent consumption, whilst maintaining or even increasing assay sensitivity. 

HPLC determination of food contaminants always involves an extraction step, generally followed by sample clean-up, prior to the analytical determination. When the analytes are present at very low concentrations, sample preparation, performed by means of classical procedures, involves long and tedious extraction and purification steps, high solvent consumption, and can be responsible for losses of the analyte and sample contamination. In recent years, a number of innovative sample... 

Gawalko and coworkers elucidated the characteristics of closed-vessel and focused open-vessel MW sample preparation techniques for the subsequent determination of Cd, Cu, and Pb, and Se in wheat, wheat products, corn bran, and rice flour by ET-AAS with transverse-heated graphite furnace [23]. Both techniques were evaluated using a total of 15 CRMs for the three food types. In the case of rice, these were the NIES 10a, 10b, and 10c Rice Flour and the NRC Rice Flour. The two techniques were equivalent in terms of agreement with the certified figures. Up to 12 samples could be processed with the closed system with minimal amounts of acid and reduced risk of contamination. Larger masses of samples could be treated by the open-vessel system. 

The analysis of phytochemicals is a tedious process involving several steps in which care must be taken to avoid degradation and contamination. Recent advancements in extraction, concentration, purification and analytical procedures of phytochemicals have been made, but additional developments are needed to assist in the identification and quantification of the diverse array of phytochemicals present in plants and foods, as well as metabolites in biological samples. Specifically there is a need to automate sample extraction, clean-up, and concentration steps to facilitate the screening of phytochemicals develop analytical methods with improved sensitivity, resolution and throughput that utilize less organic solvents and develop concentration and purification methods to produce analytical standards that are not available commercially. Continued advancements in sample preparation and analytical techniques will assist researchers in their quest to identify and quantify the vast array of phytochemicals present in plants... 

The content of contaminants in foods is an altogether more demanding problem since contaminants are often present in trace quantities. Accordingly, it is necessary to resort to the sample preparation and trace enrichment techniques commonly used in environmental analysis. The types of problems that might be encountered include drug residues in meat products, furosine (known for its deteriorative and browning reaction) in... 

The analysis of food contaminants, in particular any toxic or biologically active residue, is important for public health or quality control reasons.19 Examples are mycotoxins (aflatoxins) and pesticide and drug residues. Sample preparation is typically elaborate and might involve deproteinization, solvent extraction, and clean-up via solid-phase extraction (SPE).The use of highly sensitive and specific LC/MS/MS is increasing and has simplified some of the sample preparation procedures. 

The main advantage of MS/MS is its abihty to analyse specific target molecules directly from biological matrices without any sample preparation. One important application of MS/MS in food analysis can be the rapid screening of intact fruits or vegetables for the presence of mycotoxins or pesticides. For example intact lettuce leaves can be introduced directly into the ion source and analysed for the presence of the pesticide parathion. The CAD (methane gas) spectrum of this pesticide shows the parent ion at m/z 291 and two daughter ions at m/z 169 and m/z 154. If the peak at m/z 291 of the normal spectrum of the contaminated lettuce leaf is selected and its CAD spectrum is recorded and... 

Several studies have attempted to estimate hiunan uptake when MTBE-contaminated water is used to drink, prepare food or shower. For instance, 1% of drinking water supphes in the USA contain MTBE above 20 p.g L [31] and it was estimated that via potable water, 5% of the population of the USA may be exposed to higher than 2 xg L levels of MTBE [49]. Williams [50] reported results from a survey of MTBE in drinking waters in Cahfornia for 1995-2000. In the state that is supposed to be the most impacted by MTBE, this pollutant was detected in about 1.3% of all drinking-water samples and 27% of them above the state s primary health-based standard of 13 p.g L . ... 

In this section we provide some practical considerations to chemists not familiar with the use of immunoassays for food contaminants. We focus primarily on the use of 96-well microtiter ELISA. Regardless of the type of sample and analysis, good laboratory practices (GLPs) and international standards organization (ISO) standards, where they apply, need to be followed to ensure the quality of results and the minimization of variability. Like any other analytical protocol, the analysis of contaminants by immunoassay is a combination of three sequential steps sample collection and preparation, sample analysis, and data processing followed by the interpretation of results. 

No information on analysis of tetrachloroethylene in soil or sediment was located. Several procedures for determination of the chemical in plants and food were located. GC/ECD and GC/HSD are most commonly used to analyze solid samples for tetrachloroethylene contamination. Extraction, purge-and-trap, and headspace analysis have all been used to prepare samples. Analysis of headspace gases by GC coupled with ECD, MS, or HSD has proven relatively sensitive (low- to sub-ppb range) and reproducible for a variety of foods (Boekhold et al. 1989 Entz and Hollifield 1982 EPA 1982c Pocklington 1992 ... 

Ridgway, K Lalljie, S.P. Smith, R.M. (2007). Sample preparation techniques for the determination of trace residues and contaminants in foods. Journal of... 

At present, the selectivity improvement is easily achieved by coupling simple mono-dimensional chromatographic systems to MS. Today, easy-to-operate benchtop MS (/MS) systems (single/triple quadrupole or ion-trap) with robust interfaces are commercially available, and LC-MS(ZMS) has become the method of choice in many quantitative bioanalytical and food applications, its use also being increased in the environmental field. In spite of the high selectivity (and sensitivity) of tandem MS techniques, some kind of sample preparation and preseparation still remains necessary in order to avoid the analyte response decrease by matrix effects (ion suppression) observed in the majority of analyte/ sample combinations as well as to avoid source contamination by matrix loading. 

See alsa Chromatography Multidimensional Techniques. Environmental Analysis. Extraction Solid-Phase Extraction. Food and Nutritional Analysis Sample Preparation Contaminants Pesticide Residues. Forensic Sciences Drug Screening in Sport Illicit Drugs. Herbicides. Liquid Chromatography Instrumentation Clinical Applications Food Applications. Mass Spectrometry Peptides and Proteins. Pesticides. Pharmaceutical Analysis Sample Preparation. Proteomics. Sample Handling Automated Sample Preparation. Water Analysis Organic Compounds. 

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