Food contaminants, HPLC analysis

Scotter, M.J., Castle, C., Roberts, D., Method development and HPLC analysis of retail foods and beverages for copper chlorophyll (E141[i]) and chlorophyllin (E14[ii]) food colouring materials. Food Additives and Contaminants, 22,1163, 2005. 

On-line NPLC-GC-FID and/or FUR analysis has been used in discriminating between paraffin waxes and paraffin oils present in, or migrating between, food packaging and food simulants FID was used for quantitation [967]. In a typical application, online coupled LC-GC-F1D has also been used for the analysis of food contamination by mineral oil from printed cardboard [968]. The technique has revealed that many foods are contaminated with mineral oil products. Grob et al. [969] have determined mineral oil in canned food by on-line LC-LC-GC-F1D. DEHP was determined in salad oil by means of conventional LC-GC [970]. HPLC-GC-MS/MS (ion trap) can serve highly useful purposes in areas of applications such as impurity... 

The data presented here show that capillary SFC can be used to analyze food components such as fats, flavors and fragrances. The high chromatographic efficiency possible with capillary columns and the use of an FID make this technique an attractive alternative to HPLC or GC for some applications. When selective detectors are used, such as the NPD, SFC can also be used for the analysis of food contaminants such as pesticides. 

HPLC has been used increasingly in the analysis of food samples to separate and detect additives and contaminants. HPLC can separate a large number of compoimds both rapidly and at high sensitivity, reduce separation times, and reduce the volume of sample needed. HPLC is ideally suited for compounds of limited thermal stability, but requires sample pretreatment such as extraction and filtration. In addition, HPLC requires careful selection of mobile phase and sample pumping rate [24]. 

A number of criteria could be apphed to organize this chapter, depending on the point of view by which foods are considered. In this chapter, application of HPLC to food analysis will be described considering homogeneous classes of food components lipids, carbohydrates and related substances, proteins, peptides, amino acids, biogenic amines, phenolics, vitamins, and some selected contaminants. 

In a method proposed by Booth et al. (141) for the determination of phylloquinone in various food types, extracted samples are subjected to silica solid-phase extraction followed, in the case of meat or milk samples, by further purification using reversed-phase solid-phase extraction or liquid-phase reduction extraction, respectively. The final test solution is analyzed by NARP-HPLC, and the fluorescent hydroquinone reduction products of phylloquinone and the internal standard are produced online using a postcolumn chemical reactor packed with zinc metal. 2, 3 -Dihydrophylloquinone, a synthetic analog of phylloquinone, is a suitable internal standard for the analysis of vegetable juice, whole milk, and spinach. Another synthetic analog, Ku23), is used for the analysis of bread and beef, because a contaminant in the test solution coelutes with dihydro-phylloquinone. 

Other early food applications included the analysis of pesticide residues in fruits and vegetables, organic acids, lipids, amino acids, toxins (e.g., aflatox-ins in peanuts, ergot in rye), and contaminants. As with pharmaceutical analysis, HPLC provides the ability to analyze for vitamin content in food... 

Anion exchange chromatography coupled with ICP MS was used in the simultaneous speciation analysis of As, Se, Sb and Te compounds in extracts of fish [230]. Size exclusion chromatography (SEC) coupled with specific detectors is frequently used to analyse species of trace elements in protein-rich materials, such as extracts of meat and plant tissues. For instance, SEC hyphenated with ICP MS was used for the speciation analysis of Cu and Zn in samples of leguminous plants [191]. The same technique was applied to the speciation analysis of Cu, Cd, Zn, Se, As and Ca in fish [220] and Fe, Zn, Cu, Ag, Cd, Sn and Pb in mussels [189]. SEC HPLC coupled with GF AAS mmed out to be very useful for determining levels of Fe species in baby food [312]. With gel permeation chromatography (GPC) GF AAS, the speciation forms of Cd were determined in two kinds of vegetables contaminated with this element [216]. 

HPLC is a versatile technique applicable to diversified analytes, including labile molecules, ions, organic, and biopolymers. This chapter provides an overview of HPLC applications for the analysis of food, environmental, chemical, polymer, ion-chromatography, and life science samples. In food analysis, HPLC is widely used in product research, quality control, nutritional labeling, and residual testing of contaminants. In environmental testing, HPLC is excellent for the sensitive and specific detection of labile and nonvolatile pollutants... 

Puech, L., Dragacci, S., Gleizes, E., and Fremy J-M. (1999) Use of immunoaffinity columns for clean-up of diarrhetic toxins (okadaic acid and dinophysistoxins) extracts from shellfish prior to their analysis by HPLC/fluorimetry. Food Additives and Contaminants, 16, 6, 239-251. 

Food Analysis Preparative immunoaffinlty chromatography techniques are also applicable to the analysis of food samples for the presence of parent aflatoxins. To validate this method, naturally contaminated corn and peanut product samples were obtained and extracts made using methanol-water (60% 40%, vol/vol). An aliquot of extract was applied to the monoclonal antibody affinity column, aflatoxins eluted, and the product measured by reversed phase HPLC. In Figure... 

The derivatives are used for amino acid analysis via HPLC separation. Instead of mercapto-ethanol, a chiral thiol, e.g., N-isobutyryl-L-cysteine, is used for the detection of D-amino acids. The detection hmit lies at 1 pmol. The very fast racemizing aspartic acid is an especially suitable marker. One disadvantage of the method is that proline and hydroxyproline are not detected. This method is apphed, e.g., in the analysis of fruit juices, in which high concentrations of D-amino acids indicate bacterial contamination or the use of highly concentrated juices. Conversely, too low concentrations of D-amino acids in fermented foods (cheese, soy and fish sauces, wine vinegar) indicate unfermented imitations. Fluorescamine reacts with primary amines and amino acids - at room temperature under alkaline conditions - to form fluorescent pyrrolidones (Aex = 390 nm, Aem - 474 nm). The detection limit lies at 50-100 pmol ... 

Liquid chromatography coupled to electrospray ionization mass spectrometry (LC-ESI-MS) was introduced in the 1980s [1]. Today it has become a standard method for separation and characterization of nonvolatile compounds. Reversed-phase high-performance liquid chromatography (RP-HPLC) coupled to ESI-MS is the method of choice for peptide and protein analysis, but also used for the characterization of contaminants, therapeutic drugs, and food additives [2-5], More than 75% of HPLC analyses are run on RP stationary phases, and a wide range of columns are available with various substituents of the silica matrix, base deactivation, endcapping, and column dimensions. 

Minerals are usually analyzed by the traditional method of atomic absorption spectroscopy or with the newer induced coupled plasma analyzers. Most vitamins are analyzed by HPLC systems or colorimetric assays. Many laboratories still quantify folic acid with the use of a microbiological assay. The analysis of dietary and detergent (neutral and acid) fibers are critically important for foods and feeds, respectively. Raw materials and feeds should be examined for rodent contamination, pathogenic bacteria, molds and mycotoxins, and undesirable toxicants such as PCB, insecticides, herbicides, and heavy metals. The proper selection of ingredients will ensure the production of high-quality foods that satisfy sensory properties required for humans, and feeds that are palatable and can meet sensory properties required for domestic animals (Chapter 18). 

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