Biomedical subjects

H C Thompson

Publications and source records attributed to H C Thompson.

79 records · Page 5Linked to original sources

PubMedDate not supplied

Analysis of calcium and lead in calcium supplements by inductively coupled plasma-atomic emission spectrometry and graphite furnace atomic absorption spectrophotometry.

A method was developed to analyze various calcium supplements for Ca and Pb content. The analysis involves a dry ash of the supplements followed by wet digestion. The Pb is determined by graphite furnace atomic absorption spectrophotometry (GFAAS). Analysis of Ca is by inductively coupled plasma-atomic emission spectrometry (ICP-AES). Ca supplements fortified with Pb at levels ranging from 0.25 to 10.0 micrograms/g yielded recoveries ranging from 82.7 +/- 4.2 to 105.0 +/- 1.7%. To test accuracy, the method was applied to National Institute of Standards and Technology standard reference materials (NIST SRMs) 1572 citrus leaves and 1486 bone meal. GFAAS analysis of SRM 1572 averaged 13.1 +/- 0.6 micrograms Pb per g (certificate value, 13.3 +/- 2.4 micrograms Pb per g), and analysis of SRM 1486 averaged 1.34 +/- 0.11 micrograms Pb per g (certificate value, 1.335 +/- 0.014 micrograms Pb per g). ICP-AES analysis of SRM 1572 averaged 3.12 +/- 0.01% Ca (certificate value, 3.15 +/- 0.10% Ca by weight), and analysis of SRM 1486 averaged 27.63 +/- 0.27% Ca (certificate value, 26.58 +/- 0.24% Ca). The method's limit of quantitation (LOQ), on supplement Ca basis and a 1 g sample, averaged 0.75 micrograms Pb per 1 g Ca for supplements containing 9 to 35% Ca by weight. At a Pb level of 0.663 micrograms/g Ca, the reproducibility relative standard deviation (RSDr) averaged 7.3% and the repeatability relative standard deviation (RSDR) averaged 8.0%. It is recommended that the method be studied collaboratively.

Calcium↗

PubMedDate not supplied

Determination of lincomycin residue in salmon tissues by ion-pair reversed-phase liquid chromatography with electrochemical detection.

A method is described for detecting and quantitating lincomycin residue in salmon muscle and skin tissues by ion-pair reversed-phase liquid chromatography (LC) with electrochemical detection at +0.9 V. Lincomycin was extracted from tissues by homogenizing with 0.01 M KH2PO4 buffer (pH 4.5) and centrifuging the mixture. Water-soluble proteins were precipitated by adding sodium tungstate and sulfuric acid and removed by centrifugation. The buffer extract was then passed through a C18 solid-phase extraction cartridge. Lincomycin was eluted with 50% acetonitrile in water, and the eluate containing lincomycin was extracted with ethyl acetate. After the solvent had evaporated, the residue was redissolved in mobile phase and analyzed by LC. The method had a limit of detection of 7 ng/g lincomycin for salmon muscle and 12 ng/g for salmon skin. The limit of quantitation was 17 ng/g for salmon muscle and 24 ng/g for salmon skin. Average recoveries of lincomycin spiked at 50, 100, and 200 ng/g were > or = 85% for salmon muscle and > or = 80% for salmon skin.

Acetonitriles↗

PubMedDate not supplied

Determination of amoxicillin in catfish and salmon tissues by liquid chromatography with precolumn formaldehyde derivatization.

A liquid chromatographic (LC) method with fluorescence detection was developed for analysis of amoxicillin in catfish and salmon tissues. The tissue was extracted with phosphate buffer (pH 4.5), followed by trichloroacetic acid (TCA) precipitation of proteins and solid-phase (C18) extraction. Trace amounts of nonpolar interfering substances present after solid-phase extraction were removed by ether liquid-liquid extraction. The extract was reacted with formaldehyde and TCA at 100 degrees C for 30 min. A fluorescent derivative was extracted with ether, concentrated, and analyzed by reversed-phase LC with fluorescence detection. Average recoveries of amoxicillin spiked at 2.5-20 ppb were > 80% for catfish and > 75% for salmon muscle tissue, with coefficients of variation of < 6%. Limits of detection (LOD) and quantitation (LOQ) for catfish tissue were 0.5 and 1.2 ppb, respectively. LOD and LOQ for salmon muscle tissue were 0.8 and 2.0 ppb, respectively.

Amoxicillin↗

PubMedDate not supplied

Determination of sulfonamides in edible salmon tissue by liquid chromatography with postcolumn derivatization and fluorescence detection.

Fourteen sulfonamides-sulfanilamide, sulfadiazine, sulfathiazole, sulfapyridine, sulfamerazine, sulfamethazine, sulfamethizole, sulfamethoxypyridazine, sulfachloropyridazine, sulfamonomethoxine, sulfadoxine, sulfamethoxazole, sulfadimethoxine, and sulfaquinoxoline-residues of which could be found in aquacultured species, were separated in < 25 min by reversed-phase (C18) liquid chromatography (LC) with gradient elution. Analytes were extracted from edible salmon tissue (muscle and adhering skin) with acetonitrile-2% aqueous acetic acid, isolated with 2 liquid-liquid partitionings, and derivatized with fluorescamine after eluting from the column. The derivatives were detected by fluorescence. Recoveries (n = 4) from coho salmon fortified with sulfonamides at 5, 10, and 20 ng/g tissue averaged 79.7 +/- 7.3, 84.6 +/- 7.7, and 88.2 +/- 7.1%, respectively. Limits of quantitation were 5 ng/g tissue, for sulfanilamide, sulfamethoxypyridazine, and sulfaquinoxoline and 1 ng/g tissue for the remaining sulfonamides.

Acetic Acid↗

PubMedDate not supplied

Analysis of fumonisin B1 in rodent feed by CE with fluorescence detection of the FMOC derivative.

A fast, simple, and environmentally friendly method has been developed for the analysis of fumonisin B1 (FB1) in rodent feed using CE. FB1 is the major fumonisin metabolite produced by the fungus Fusarium moniliforme and has been implicated in human and animal diseases. FB1 was extracted from rodent feed with acetonitrile/water (50/50) (vol/vol) and cleaned up with a C18 Sep-Pak Vac cartridge (Waters Corp., Milford, MA, U.S.A.). FB1 was quantitated after elution from the column using capillary electrophoresis with a 25-mM sodium borate buffer (pH 9.0) containing 10% acetonitrile and fluorescence detection of the (9-fluorenylmethyl) chloroformate (FMOC) derivative. The minimum detectable amount in rodent feed was 0.5 pmm. Recovery values in spiked rodent feed averaged more than 87% over the 2-20 ppm range.

Animal Feed↗

PubMedDate not supplied

A bridging study between liquid chromatography and microbial inhibition assay methods for determining amoxicillin residues in catfish muscle.

A bridging study was conducted to establish the correlation between a liquid chromatographic (LC) method and a microbial inhibition (MI) method for analysis of amoxicillin residues in catfish muscle. The LC procedure involved precolumn derivatization with formaldehyde followed by LC separation with fluorescence detection. The MI procedure used Bacillus stearothermophilus as the test organism and was validated in this study before the bridging investigation. The 2 methods were compared for determination of both fortified and incurred samples. No significant differences were found between the methods when all data were included in statistical computations. The linear correlation of LC means versus MI means had a slope of 0.972 and a negligible intercept (1.0 ng/g), with a correlation coefficient of 0.9962. LC was more specific and showed better sensitivity than MI for amoxicillin residues at < or = 10 ng/g. For practical purposes, values obtained by the 2 methods can be considered equivalent.

Amoxicillin↗

PubMedDate not supplied

Determination of calcium by inductively coupled plasma-atomic emission spectrometry, and lead by graphite furnace atomic absorption spectrometry, in calcium supplements after microwave dissolution or dry-ash digestion: method trial.

A 3-laboratory method trial was conducted to evaluate 2 sample digestion procedures and instrumental determination parameters for analysis of calcium and lead in Ca supplements. Calcium supplements were treated by dry-ash digestion or microwave dissolution prior to spectrometric analysis. In each case, Pb was determined by graphite furnace atomic absorption spectrometry and Ca by inductively coupled plasma-atomic emission spectrometry. Blind duplicates of 6 Ca supplement samples were analyzed after each sample treatment procedure. Matrix pairs contained dissimilar Pb levels to cover the analyte range encountered during method development. Calcium content of the Ca supplement samples also reflected the range seen during method development. Stock solutions of Ca and Pb were supplied to collaborators for preparation of quantitation standards to remove a variable external to the method. National Institute of Standards and Technology Standard Reference Material (NIST SRM) 1486, bone meal, was included to assess method accuracy and recovery at NIST certificate Ca and Pb levels for this material (26.58 +/- 0.24% Ca and 1.335 +/- 0.014 micrograms Pb/g). Analyses of the NIST SRM yielded 25.9 +/- 1.1 and 27.2 +/- 2.3% Ca and 1.53 +/- 0.19 and 1.26 +/- 0.19 micrograms Pb/g for dry-ash and microwave procedures, respectively. Statistical analyses of data indicated acceptable repeatability and reproducibility for determination of Pb and Ca in various Ca supplements. With either sample preparation technique, the method is appropriate for determining Pb or Ca in Ca supplements.

Biological Products↗