Trans- and cis-resveratrol concentration in wines produced in Serbia

Resveratrol, which occurs in two isomeric forms, trans and cis, is a phytoalexin with numerous pharmacological activities, such as anti-cancer, antiviral, neuroprotective and anti-aging. Red wine is the main source of the compound and an easy way of including resveratrol in the human diet. In this study, the most popular commercial Serbian wines (red, white and ros?-type) were analyzed for their content of trans- and cis-resveratrol. The analysis was performed by HPLC with a UV detector. Prior to the injection, phenolic compounds were extracted onto a LiChrolut RP18 bonded silica cartridge. The concentration of trans-resveratrol ranged from 0.11 to 1.69 mg L-1 and cis-resveratrol from 0.12 to 1.49 mg L-1.

Planar Chromatography for Quantitative Determination of Ampicillin Residues in Milk and Muscle

A method involving protein precipitation with trichloroacetic acid and ampicillin hydrolysis with sodium hydroxide was developed for determination of ampicillin residue in milk and muscle. The hydrolysis product reacts in an acidic medium, in the presence of mercuric chloride, to form a fluorescent compound, which is extracted from the matrix with dichloromethane and concentrated on a silica Sep-Pak cartridge in a single step. After elution of the silica cartridge and evaporation of the solvent, the residue is recovered in 100 μL ethyl acetate, and 20 μL is deposited on a chromatoplate and chromatographed with ethyl acetate. The method allows determination of ampicillin residues in milk and muscle fortified at 4 μg/L and 50 μg/kg, respectively.

Potential Interference by Free Fatty Acids in Determination of Tricyclazole in Brown Rice by Gas Chromatography with Flame Thermionic Detection

A convenient method is described for the determination of tricyclazole in brown rice, and the interference of free fatty acids with flame thermionic detection (FTD) is reported for the first time. Brown rice is extracted with acetone, the extract is filtered, and the filtrate is evaporated. To the residue is added 10% (w/v) NaCI solution, and the mixture is extracted with ethyl acetate. The extract is charged on a Sep-Pak Plus silica cartridge. Free fatty acids are removed from the rice by washing with diethyl ether, and tricyclazole is eluted with acetone-n-hexane (1 + 1). Tricyclazole is determined on a DB-1 capillary column by gas chromatography with FTD (GC–FTD). Linoleic acid and oleic acid, which have essentially the same retention time as tricyclazole, cannot be detected by FTD. Thus, without the Sep- Pak Plus silica cleanup, the peak height of tricyclazole in the chromatogram decreased, the extent depending on the concentration of linoleic acid, n-Hexane–acetonitrile partitioning was not used for cleanup because it could not remove 50% of the free fatty acids. Recoveries (mean ± standard deviation, n = 5) of tricyclazole from rice fortified at 2 and 0.1 ppm were 90.5 ±9.4% and 81.3±10.6%, respectively. The limit of quantitation was 0.05 ppm.

Determination of Imazalil Residues in Lemons by Gas Chromatography with Nitrogen–Phosphorus Detection

A simple and reliable method was developed for determination of imazalil residues in whole lemons. Imazalil was extracted from lemon samples with ethyl acetate under basic conditions. The ethyl acetate in the extract was evaporated, and the residue was dissolved in dichloromethane. The solution was applied to a solid-phase extraction (diol- bonded silica) cartridge. Imazalil was eluted with methanol and determined by gas chromatography (GC) with nitrogen–phosphorus detection. Recoveries at 4 fortified levels (0.1,1.0,2.0, and 5.0 μg/g) ranged from 93.3 to 97.8%, with coefficients of variation ranging from 0.2 to 3.0%. The detection limit was 0.05 μg/g. Fifteen commercial lemon samples were analyzed for imazalil residues; 10 were positive. Concentrations of imazalil residues ranged from 0.22 to 4.44 μg/g. Imazalil-positive samples were confirmed by GC with mass–selective detection (m/z 173,215, and 217).

Interactions of sediment contaminants in the testing of mutagenicity

The influence of sediment contaminants on the Salmonella mutagenicity test was investigated to develop a preparation method not subject to interference by coexisting substances. Organic chemicals were extracted from sediment by dichloromethane/ethanol (4:1), acetonitrile or ethanol, and dichloromethane (DCM) extract was refined by washing with alkali, passing through a reduced-Cu column and/or fractionation with a silica cartridge. The strain Salmonella typhimurium TA98 was used. Sediment extracts and their refined preparations were first determined in their own mutagenicity, and then the influence on the mutagenicity of a fixed dose of 2-aminofluorene (2-AF) as a positive standard mutagen was examined. The toxicity to the strain was also tested. It was concluded that the coexisting environmental chemicals in sediment inhibited or promoted the original mutagenicity of the samples.