Polycyclic aromatic hydrocarbons (PAHs), of which benzo[a]pyrene is the most commonly studied and measured, are formed by the incomplete combustion of organic matter. They are widely distributed in the environment and human exposure to them is unavoidable. A number of them, such as benzo[a]pyrene, are carcinogenic and mutagenic, and they are widely believed to make a substantial contribution to the overall burden of cancer in humans. Their presence in the environment is reflected in their presence at detectable levels in many types of uncooked food. In addition, cooking processes can generate PAHs in food. PAHs can also be formed during the curing and processing of raw food prior to cooking. Several studies have been carried out to determine the levels of exposure to PAHs from representative human diets, and the proportion of the overall burden of environmental exposure to PAHs that is attributable to the diet. In most cases, it is concluded that diet is the major source of human exposure to PAHs. The major dietary sources of PAHs are cereals and vegetables, rather than meat, except where there is high consumption of meat cooked over an open flame. More recently, biomonitoring procedures have been developed to assess human exposure to PAHs and these have also indicated that diet is a major source of exposure. Exposure to nitro-PAHs through food consumption appears to be very low.

Polycyclic aromatic hydrocarbons in the diet.

Polycyclic aromatic hydrocarbons in smoked fish: a critical review

Effects of grilling and roasting on the levels of polycyclic aromatic hydrocarbons in beef and pork

Optimisation of microwave assisted extraction (MAE) for polycyclic aromatic hydrocarbon (PAH) determination in smoked meat.

Bioaccumulation and biomagnification of polycyclic aromatic hydrocarbons in aquatic organisms

A simple and accurate analytical method for determination of polycyclic aromatic hydrocarbons (PAHs) in fish and shellfish is presented, which is considered to be useful for routine analyses and for screening purposes. The procedure involves alkaline digestion, extraction with n-hexane, silica gel column chromatography, and liquid chromatographic (LC) determination with fluorometric detection. During development of the analytical method for determination of PAHs, it was found that benzo[a]pyrene, a representative PAH, was decomposed easily by the analytical procedure, and this tendency was investigated for the experimental conditions used. Benzo[a]pyrene was decomposed by the coexistence of alkaline conditions, light, and oxygen; by peroxides in aged ethyl ether; and by oxygen when absorbed on silica gel. Thus, to obtain good recoveries and precise analytical results, these decomposition conditions must be avoided. The following precautions are recommended: protection from light through all analytical steps; addition of Na2S to alkaline digestion mixture as an antioxidant; complete removal of peroxides from ethyl ether just before use; quick column chromatography on silica gel; and prevention of air from contact with adsorbent. When this simple method was applied to fish and shellfish samples, very good recoveries of PAHs from fortified fish samples were obtained, and no serious interferences were observed in fish and shellfish extracts.

Liquid chromatographic determination of polycyclic aromatic hydrocarbons in fish and shellfish.

A simple liquid chromatographic (LC) method is described for the determination of free and added niacin and niacinamide in meats. A sample is homogenized and extracted with water, and the water extract is centrifuged, deproteinized with zinc hydroxide, and filtered first through a fluted paper and then through a microporous filter. The filtrate is subjected to liquid chromatography with UV detection at 263 nm. Different ion-pair systems are needed for the measurement of niacin and niacinamide on a reverse phase column. Methanol-water (1 + 9) containing 5mM tetrabutyl ammonium ion is used to separate niacin. Water containing 10mM heptane sulfonic acid is recommended for niacinamide. Recoveries (CV,%) are 104.8% (2.9%) for niacin and 96.3% (2.7%) for niacinamide at a 10 mg/100 g fortification level. Detection limit is 1 mg/100 g sample for niacin and niacinamide.

Liquid Chromatographic Determination of Free and Added Niacin and Niacinamide in Beef and Pork

CNP (chlornitrofen), widely used as a paddy herbicide in Japan, is known to be converted readily to the corresponding amino derivative by reduction of the nitro group in the environment. An unusually high level of CNP residue concentration was reported in fresh-water fish and shellfish during the application period. Therefore, the occurrence of CNP reduction products in samples with high CNP residue levels was investigated and two unknown compounds were detected which were not identical with any standard pesticides on GLC. These two compounds, obtained in preparative scale experiments, showed high sensitivity in ECD-GC and NP-FID GC and gave CNP-amino compound on alkaline hydrolysis. From the GC-MS analysis and the above mentioned chemical property, the structures of these compounds were elucidated as CNP-acetamide (CNP-a) and CNP-formamide (CNP-f); these structures were confirmed by comparison of the products with authentic samples prepared from CNP.Analytical methods for residual CNP-a and CNP-f were established and the residual concentrations were investigated in fresh-water fish and shellfish at regular intervals through a year at a fixed location in Miyagi prefecture. The maximum concentrations of CNP derivatives were 0.58ppm (CNP-a) and 0.24ppm (CNP-f) in freshwater clam, 0.04 (CNP-a) and 0.05ppm (CNP-f) in loach, and 0.06 (CNP-a) and 0.13ppm (CNP-f) in crucian carp during May and June, and these levels decreased rapidly after the end of the herbicide application period.

Residues of CNP Metabolites in Fish and Shellfish

An accurate, sensitive method is described for the determination of monensin residue in chicken tissues by liquid chromatography (LC), in which monensin is derivatized with a fluorescent labeling reagent, 9-anthryldiazomethane (ADAM), to enable fluorometric detection. Samples are extracted with methanol-water (8 + 2), the extract is partitioned between CHCl3 and water, and the CHCl3 layer is cleaned up by silica gel column chromatography. Free monensin, obtained by treatment with phosphate buffer solution (pH 3) at 0 degrees C, is derivatized with ADAM and passed through a disposable silica cartridge. Monensin-ADAM is identified and quantitated by normal phase LC using fluorometric detection. The detection limit is 1 ppb in chicken tissues. Recoveries were 77.6 +/- 1.8% at 1 ppm, 56.7 +/- 7.1% at 100 ppb, and 46.5 +/- 3.7% at 10 ppb fortification levels in chicken. Gas chromatography-mass spectrometry is capable of confirming monensin methyl ester tris trimethylsilyl ether in samples containing residues greater than 5 ppm.

Liquid chromatographic determination of monensin in chicken tissues with fluorometric detection and confirmation by gas chromatography-mass spectrometry.

The determination of diphenyl ether herbicides, NIP, CNP, chlomethoxynil and TCNP, was achieved according to the procedure for the determination of organochlorine pesticides, which consists of acetonitrile extraction and clean-up by silver nitrate-coated Florisil column chromatography.The homogenized sample is extracted 3 times with acetonitrile. The extract is diluted with water and re-extracted with n-hexane. After concentration, the n-hexane layer is subjected to silver nitrate-coated Florisil column chromatography. The 2% ethylacetate/n-hexane eluate is concentrated for ECD/GC analysis. Satisfactory gas chromatograms were obtained for most samples.The average recoveries throughout the procedure were 98% (NIP), 97% (CNP), 91% (chlomethoxynil) and 95% (TCNP).

Shigeru Suzuki

Papers

Liquid chromatographic determination of polycyclic aromatic hydrocarbons in fish and shellfish.

Liquid Chromatographic Determination of Free and Added Niacin and Niacinamide in Beef and Pork

Residues of CNP Metabolites in Fish and Shellfish

Liquid chromatographic determination of monensin in chicken tissues with fluorometric detection and confirmation by gas chromatography-mass spectrometry.

Analytical Method for Diphenyl Ether Herbicides in Fish and Shellfish