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Biomedical subjects

J F Lawrence

Publications and source records attributed to J F Lawrence.

At least 55 records · Page 3Linked to original sources
PubMed1984

Mammary transfer and metabolism in the rat of halogenated fatty acids of halogenated olive oil.

To assess possible incorporation of halogenated fatty acids into the neonate via the milk, a 4-day study was carried out in which lactating Wistar rats were orally dosed with either brominated olive oil (BOO) (0.6 g/kg body wt/day) or chlorinated olive oil (COO) (0.4 g/kg body wt/day) for the first 4 days. On days 1-5 inclusive 2 pups per litter were sacrificed and the stomach curd and livers analyzed for halogenated fatty acids by gas liquid chromatography (GLC). On day 5 all dams also were sacrificed and their livers and adipose tissue similarly analyzed. With BOO, brominated fatty acids (bfa) accumulated in both the milk lipids and neonate liver lipids, and appeared to plateau on day 4 at levels of 2% and 5% respectively. In contrast to the BOO in which approximately 100% of the bfa was dibromostearic (DBS), the milk bfa comprised 79% (DBS), 9% dibromopalmitic (DBP) and 12% dibromomyristic (DBM) acids, suggesting maternal metabolism to the shorter chain brominated acids. In the neonate liver lipids the bfa composition was 47% (DBS), 12% (DBP) and 41% (DBM), suggesting either further metabolism in the neonate and/or preferential accumulation of the shorter chain brominated acids. The analysis of maternal tissue indicated very low bfa residues, contrary to previous studies in non-lactating rats. Similar results were obtained with COO.

Adipose Tissue↗
PubMed1984

Brominated fatty acid distribution in tissues and fluids of rats fed brominated vegetable oils.

Rats dosed orally for four days with 0.24 g/kg body weight per day of brominated olive oil (BOO) or brominated sesame oil (BSO) were found to accumulate dibromostearic (DBS) acid (from BOO) and DBS and tetrabromostearic (TBS) acids (from BSO) in the liver, heart and adipose tissue. The metabolites, dibromopalmitic, and dibromomyristic acids (from BOO and BSO), as well as their tetrabromo-analogues (from BSO) were found as determined by gas chromatography with halogen specific detection and confirmed by gas chromatography-mass spectrometry. Blood contained no DBS, TBS or metabolites. However, inorganic bromide was observed in both blood and urine while none was observed in the feces. The latter contained significant quantities of both DBS and TBS but showed the absence of the four brominated metabolites.

Adipose Tissue↗
PubMed1983

The use of ion-exchange filters for the determination of iodide in milk by X-ray fluorescence spectrometry.

An X-ray fluorescence spectrometric method has been developed for the quantitative determination of iodide in milk which makes use of anion-exchange filters for the isolation and concentration of iodide from the liquid samples. The milk is deproteinized with trichloroacetic acid, filtered then passed through an anion-exchange paper disc to remove the iodide. The disc is removed, dried then analysed by X-ray fluorescence spectrometry. Six samples, consisting of homogenized, 2% fat and skim milk were analysed and found to contain between 0.37-0.67 ppm iodide. Detection limits in milk were estimated to be 0.05 ppm.

Animals↗
PubMed1983

The determination of formaldehyde in beer and soft drinks by HPLC of the 2,4-dinitrophenylhydrazone derivative.

A simple procedure was developed for the determination of formaldehyde in samples of beer and soft drinks. A volume of sample was distilled and the aqueous distillate containing the formaldehyde collected directly in a solution of 2,4-dinitrophenylhydrazine. The resulting hydrazone was extracted and analysed by reversed-phase high-performance liquid chromatography with UV absorbance detection. Levels of formaldehyde found were in the low mg/kg range. Detection limits were less than 0.1 mg/kg of sample. Results were confirmed by mass spectrometry (probe) of the derivatives after fraction collection from the HPLC.

Beer↗
PubMed1983

Acid methanolysis and gas chromatographic determination of brominated vegetable oils in soft drinks.

A gas chromatographic method has been developed for determination of brominated vegetable oils in citrus-flavored soft drinks. Oils were extracted from the drinks with ethyl ether and subjected to acid-catalyzed methanolysis. The resulting brominated methyl esters (dibromostearate, tetrabromostearate, and hexabromostearate) were separated and quantitated as single peaks on a 3% OV-3 column. Chromatography columns were stable for about 3 months of daily use; then the first 15 cm of column packing material was replaced or a new column was prepared. A number of citrus soft drinks were analyzed and contained 3.5-3.9 mg brominated oil/10 fl. oz. Recoveries from spiked samples after organic extraction and methanolysis were 94.5-105%.

Beverages↗
PubMed1981

Gravimetric determination of ethoxylated mono- and diglycerides in bread.

A gravimetric method is described for the quantitative determination of ethoxylated mono-and diglycerides (EMGs) in bread at levels as low 0.42% (dry sample). The air-dried pulverized samples are Soxhlet-extracted 22 h with an azeotropic mixture of n-propanol-water. The contents are evaporated to dryness, and then treated with 5% HCl in methanol to trans-esterify the fatty acids present which are then removed by petroleum ether extraction. The EMGs are subsequently precipitated from aqueous solution with phosphomolybdic acid in the presence of barium ions. The precipitate is weighed and compared with known amounts of standard carried through the same procedure.

Bread↗
PubMed1980

Comparison of gas and liquid chromatography for determination of anilazine in potatoes and tomatoes.

Anilazine (2,4-dichloro-6-(2-chloroanilino)-1,3,5-triazine), a triazine fungicide, is extracted from potatoes or tomatoes with acetonitrile. An aliquot of the filtered extract is partitioned between methylene chloride and water. The organic phase is concentrated and passed through a 3% deactivated Florisil column for cleanup. The eluted anilazine is then concentrated and determined by liquid chromatography (LC) on LiChrosorb RP-8 column with a mobile phase of acetonitrile--water (55 + 45) and detection at 275 nm, the absorption maximum of anilazine. Twenty-five nanograms produces a 5 cm peak under the conditions used. Detection limit is about 0.02 ppm in both vegetables. A comparison is made with gas chromatography, using either an electron capture (EC) or nitrogen--phosphorus alkali-flame ionization (NP) detector. Separations are carried out on a 4% SE-30 + 6% SP-2401 column at 195 degrees C at 40 mL/min. Detection limits for all systems studied are about 0.02--0.05 ppm in the samples studied. Recoveries over a concentration range of 0.2--10.0 ppm are greater than 80% with the extraction procedure employed and LC determination.

Aniline Compounds↗
PubMed1978

Gas-liquid chromatography of triazine herbicides as heptafluorobutyryl derivatives and some applications to analysis in foods.

The heptafluorobutyryl (HFB) derivatives of ten triazine herbicides were prepared by reacting the pesticides with heptafluorobutyric anhydride in benzene, in the presence of trimethylamine or pyridine as catalyst. The reactions produced mainly the mono-HFB products while some of the herbicides had small quantities of the di-HFB derivatives present. The derivatives were 300 fold to several thousand fold more sensitive to electron-capture detection than the underivatized triazines. They also were 5-10 fold more sensitive than the parents by electrolytic conductivity detection in the halogen mode while they were of similar sensitivity with the same detector in the nitrogen mode. The derivatives eluted in the same general order as the parent triazines on stationary phases of OV-1, OV-101, OV-101/QF-1, and OV-210. This method was successfully applied to the analysis of potatoes, peas and tomatoes spiked with various triazines at levels of 0.13-0.86 ppm.

Chromatography, Gas↗
PubMed1978

Detection of goitrin and its heptafluorobutyryl derivative by gas-liquid chromatography with electron capture, electrolytic conductivity and sulfur detectors.

The separation of goitrin by two gas-liquid chromatographic columns, the response of different detectors and the use of the heptafluorobutyric (HFB) anhydride derivative of goitrin to improve sensitivity was investigated. The non-polar 3% OV-1 and the intermediate 4% SE-30/6% SP-2401 on 80-100 mesh Chromosorb W HP gave comparable results and were considered interchangeable. The sensitivities of the electron capture, sulfur 394 nm emission, chlorine and nitrogen Coulson electrolytic conductivity detectors were inadequate for goitrin per se. Chromatography and sensitivity of all detectors to goitrin were greatly improved by using by using the HFB derivative. It was possible to detect 1 to 60 ng of goitrin-HFB in standard solutions. Application of the technique to goitrin-spiked (2 ppm) milk, cleaned up by high-performance liquid chromatography, encountered no problems and was considered satisfactory for all four detectors.

Animals↗
PubMed1978

High-pressure liquid chromatographic analysis of carbofuran and two non-conjugated metabolites in crops as fluorescent dansyl derivatives.

Carbofuran, and non-conjugated 3-hydroxycarbofuran and 3-ketocarbofuran were extracted from carrots, corn and potatoes with acetone and partitioned into hexane-methylene chloride. The organic extract was evaporated to a small volume for clean-up on a 2% deactivated Florisil column. All three carbamates were eluted with 15% acetone in hexane. The pesticide residues were hydrolysed to their corresponding phenols with 0.1 M sodium carbonate followed by derivatization with dansyl chloride in acetone. The derivatives were extracted and analysed by high-pressure liquid chromatography with fluorescence detection (excitation, 360 nm; emission, greater than 400 nm). Absolute recoveries for all three compounds were between 50 and 65% for spiked samples by the extraction method used. Detection limits approached 0.01 ppm in the foods studied.

Carbofuran↗
PubMed1978

High pressure liquid chromatography with ultraviolet absorbance or fluorescence detection of carbaryl in potato and corn.

Carbaryl (1-naphthyl-N-methylcarbamate) was extracted from corn and potato with acetone. The acetone extract was partitioned into methylene chloride-hexane and concentrated for cleanup on a 5% water-deactivated Florisil column. The fraction containing the carbamate was subjected to high pressure liquid chromatographic (HPLC) analysis on a 25 cm LiChrosorb Si60 (5 micron) column (2.2 mm id) by various means. First, the pesticide was analyzed directly with ultraviolet (UV) absorption detection at 254 nm and a mobile phase of trimethyl-pentane-isopropanol (96 + 4). After this, a fluorescent derivative was prepared, using dansyl chloride (5-dimethylaminonaphthalene-1-sulfonyl chloride), and analyzed by HPLC, using trimethylpentane-dioxane (95 + 5) as the mobile phase, with both UV absorption (254 nm) and fluorescence (excitation 365 nm, emission greater than 400 nm) detection. The response/ng for the dansyl derivative with fluorescence detection was 1.3 times greater than that for UV detection and 8 times more sensitive than direct UV detection of the carbamate. About 10 ppb carbaryl could be detected after derivatization in the foods studied; for direct analysis, 30-50 ppb could be detected at a 2:1 signal:noise ratio. Recoveries at 0.1 ppm averaged 90% by direct analysis compared with 78% after derivatization.

Carbaryl↗
PubMed1977

Detection of carbofuran and metabolites directly or as their heptafluorobutyryl derivatives using gas-liquid or high-pressure liquid chromatography with different detectors.

The gas chromatography of the heptafluorobutyryl derivatives of carbofuran, 3-ketocarbofuran and 3-hydroxycarbofuran is examined with electrolytic conductivity detection (halogen mode). The reaction consists of heating the compounds with heptafluorobutyric anhydride in the presence of trimethylamine catalyst. Although as little as 200 pg of carbofuran, 400 pg of 3-ketocarbofuran and 100 pg of 3-hydroxycarbofuran can be detected by electrolytic conductivity, the minimum detectable quantities by electron capture are about 20-fold less for each derivative. Application to the analysis of carbofuran and 3-ketocarbofuran in corn, potato, turnip and wheat is carried out. This technique is compared to direct gas chromatography in the nitrogen mode and to direct high-pressure liquid chromatography with UV detection at 254 nm using extracts of field-treated turnips.

Carbofuran↗