Biomedical subjects

F L Joe

Publications and source records attributed to F L Joe.

27 records · Page 2Linked to original sources

PubMedDate not supplied

Liquid chromatographic methodology for the characterization of orange juice.

Liquid chromatographic (LC) methodology potentially useful for the characterization of orange juice, with particular regard to detecting adulteration of orange juice by computer pattern recognition analysis, has been developed. After dilution with methanol the juice is extracted with hexane to remove the carotenoids, which are chromatographed on a C18 column with an acetonitrile-methanol-methylene chloride mobile phase and detection at 450 nm. Further extraction of the juice with methylene chloride isolates the methoxylated flavones, which are chromatographed by reverse phase LC with an acetonitrile-methanol-water mobile phase and detection at 280 nm. The flavanone glycosides remaining in solution are chromatographed on a C18 column with an acetonitrile-water mobile phase and detection at 280 nm. The precisions of the heights of the 32 LC peaks selected for pattern recognition analysis were determined from 5 replicate analyses of a single juice. Coefficients of variation of the replicates ranged from 0.3 to 4.5%, with an average of 2.1%. Adulteration of products with sodium benzoate-fortified pulpwash or grapefruit juice can be detected by this method. Pattern recognition analysis of the data obtained for 80 authentic and 19 adulterated orange juices showed that the method is potentially useful for distinguishing between authentic and adulterated products.

Beverages↗

PubMedDate not supplied

Rapid gas chromatographic method for determining ethyl carbamate in alcoholic beverages with thermal energy analyzer detection.

A rapid column elution method has been developed for the determination of ethyl carbamate (EC) in alcoholic beverages. The beverage is mixed with Celite and packed in a column containing deactivated alumina capped with a layer of sodium sulfate. EC is then eluted with methylene chloride. The method, using a gas chromatograph-thermal energy analyzer with a nitrogen converter for detection and quantitation of EC, has been applied to a variety of alcoholic beverages. Recoveries +/- standard deviations of EC in wine and whisky fortified at the 20 and 133 micrograms/kg (ppb) levels averaged 87.3 +/- 5.3 and 88.7 +/- 3.6%, respectively. The method has a limit of detection of 1.5 ppb. Gas chromatography/mass spectrometry/mass spectrometry was used to confirm the identity and quantitation of EC in selected beverage extracts.

Alcoholic Beverages↗

PubMedDate not supplied

Liquid chromatographic determination of basic nitrogen-containing polynuclear aromatic hydrocarbons in smoked foods.

Several smoked foods were analyzed for basic nitrogen-containing polynuclear aromatic hydrocarbon (NPAH) content by a relatively rapid liquid chromatographic (LC) technique. The analyzed products included both domestic and imported market basket commodities. Nanogram quantities of NPAH standards were detected by UV and fluorescence detectors connected in series. The NPAHs were extracted from basic aqueous ethanolic solution into cyclohexane, extracted from cyclohexane into 6N HCl, and extracted back into cyclohexane after neutralization of the acid. The NPAHs were then purified by filtering the extract through deactivated basic alumina. The eluate from this step was concentrated to dryness, and the residue was dissolved in 95% ethanol and analyzed by LC, using a Vydac C-18 column and acetonitrile-water (9 + 1) as the mobile phase. Recoveries of 3 NPAHs, 5,7-dimethylbenz(a)acridine, dibenz(a,j)acridine, and dibenz(a,h)acridine, each added to salmon and sausage at the 5 ppb level, ranged from 62 to 101% by fluorescence measurement and from 64 to 106% by UV measurement. None of the NPAHs used as standards were found by either fluorescence or UV detection at levels greater than or equal to 5 ppb in any of the foods analyzed.

Animals↗

PubMedDate not supplied

Gas chromatographic determination of fatty acids and sterols in orange juice.

A gas chromatographic (GC) method has been developed for the simultaneous quantitation of fatty acids and sterols in orange juice, using a bonded phase fused silica capillary column of intermediate polarity, splitless automatic injection, and flame ionization detection. Sample preparation has been simplified by using 1 g C-18 adsorbent in a disposable minicolumn to extract 2 mL orange juice. Methylation of fatty acids and silylation of the sterols were carried out in the eluted extract (low polarity lipid fraction). The method precision was 7%; recoveries ranged from 83 to 113%. The precision of the injection technique was 2%. Seven major fatty acids and 5 sterols in orange juice were quantitated by the GC method and identified by GC/mass spectrometry. Quantitative data for several orange juice samples indicated that the levels of the compounds of interest were in the 1.3-72.0 mg/L range. The results demonstrate that bonded phase fused silica capillary GC has great versatility and potential for the quantitative determination of fatty acids and sterols.

Beverages↗

PubMedDate not supplied

Current trends in levels of volatile N-nitrosamines in fried bacon and fried-out bacon fat.

Commercially processed bacon samples purchased from the Washington, DC, retail market have been periodically analyzed since 1971 for the presence of volatile N-nitrosamines in the fried product. During that time, a downward trend in the concentration of N-nitrosopyrrolidine has been observed, and between 1978 and 1980 it plateaued at 4-30 ppb, with an average of 11 ppb. A recent survey, however, indicates a change in this downward trend, with N-nitrosopyrrolidine found at levels ranging from 1 to 65 ppb, average 21 ppb. Volatile N-nitrosamines were found at levels up to 110 ppb in the fried product and up to 85 ppb in the fried-out bacon fat.

Animals↗

PubMedDate not supplied

Reevaluation of Monier-Williams method for determining sulfite in food.

The Monier-Williams distillation procedure has a long history of successful use for determining sulfite in fruit products and wine; however, a systematic evaluation of its accuracy and precision with other food matrices has not been undertaken. We found that the Monier-Williams distillation yielded greater than 90% recovery of sulfite added to foods such as table grapes, hominy, dried mangoes, and lemon juice. Less than 85% recovery was obtained with broccoli, soda crackers, cheese-peanut butter crackers, mushrooms, and potato chips. These results may, in fact, accurately reflect the residual levels of sulfite if a portion of the sulfite undergoes irreversible reaction with some food components. Analysis of commercial food products gave sulfite levels ranging from 1400 ppm in dried apple slices to 25 ppm in cream sherry.

Chemical Phenomena↗

PubMedDate not supplied

Liquid chromatographic determination of trace residues of polynuclear aromatic hydrocarbons in smoked foods.

A liquid chromatographic (LC) method was developed and applied to the determination of polynuclear aromatic hydrocarbons (PAHs) in a variety of smoked, market basket commodities. The PAHs are extracted with 1,1,2-trichloro-1,2,2-trifluoroethane (Freon 113) from alcoholic KOH digests of the commodities. The extracts are purified by column chromatography through a deactivated silica gel/alumina column and by liquid-liquid partitioning between dimethyl sulfoxide and cyclohexane before separation of the PAHs by LC. Both fluorescence and UV detectors are used to monitor the LC column effluent to detect nanogram quantities of PAHs. Trace levels of carcinogenic and non-carcinogenic PAHs were found in all samples analyzed, although generally at less than 1 ppb levels.

Animals↗

PubMedDate not supplied

Liquid chromatographic determination of aspartame in dry beverage bases and sweetener tablets with confirmation by thin layer chromatography.

A liquid chromatographic method is described for the determination of aspartame in dry beverage bases and sweetener tablets. The sample was mixed with the mobile phase, the pH was adjusted to within +/- 0.1 pH unit of the mobile phase, and the sample was diluted to volume with the mobile phase. The solution was filtered and a 10 microL aliquot was injected onto a C18 reverse phase column. Aspartame was quantitated with an ultraviolet detector. Recoveries of aspartame ranged from 94 to 111%. The dry beverage bases contained 5-13% aspartame and the sweetener tablets contained 19% aspartame. The presence of aspartame was confirmed by using thin layer chromatography.

Aspartame↗

PubMedDate not supplied

Determination of ethyl carbamate in alcoholic beverages and soy sauce by gas chromatography with mass selective detection: collaborative study.

A method using gas chromatography with mass selective detection for the determination of ethyl carbamate (EC; also known as urethane) in alcoholic beverages and soy sauce was collaboratively studied by 17 laboratories including authors' laboratories. The method uses prepacked columns for extraction of liquids with methylene chloride, and n-propyl carbamate as the internal standard. A practice sample and 6 samples of distilled spirits, fortified wines, table wines, and soy sauces were analyzed by each collaborator. Each matrix included blind duplicates of incurred and fortified EC at 3 levels. Distilled spirits contained 50-330 ng EC/g (ppb), fortified wine 40-160 ppb, table wine 10-50 ppb, and soy sauce 15-70 ppb. The ranges of the repeatability relative standard deviations, excluding outliers, were 4.03-6.63% for distilled spirits, 4.01-5.05% for fortified wine, 3.94-6.73% for table wine, and 4.70-8.49% for soy sauce. The ranges of the reproducibility relative standard deviations, excluding outliers, were 8.53-9.49% for distilled spirits, 6.84-12.02% for fortified wine, 8.86-18.47% for table wine, and 13.87-27.37% for soy sauce. Recoveries of added EC ranged from 87 to 93%. Recoveries relative to reference values, labeled as the internal standard, obtained by using gas chromatography/tandem mass spectrometry with a triple quadrupole mass spectrometer ranged from 89 to 100%.

Alcoholic Beverages↗