Biomedical subjects

N Thiex

Publications and source records attributed to N Thiex.

4 recordsLinked to original sources

PubMed1980

Solvent extraction and flameless atomic absorption determination of arsenic in biological materials.

This method for the determination of arsenic specifies wet digestion of biological materials, followed by reduction of arsenic(V) to arsenic(III) and extraction of arsenic(III) with diethylammonium diethyldithiocarbamate (DDDC) in chloroform. The extract is analyzed by flameless atomic absorption spectrometry (AAS). Recoveries of arsenic from plant and animal tissues ranged from 88 to 108%, averaging 99%. Analyses of rat tissues, using a radioisotope technique, averaged 103% of theoretical. Repeatability studies on rat tissues showed the method to be consistent with coefficients of variation ranging from 3.0 to 8.5%, and a test for ruggedness showed that the method is not affected by slight variations in procedure, but is affected by the presence of Fe and Cu. The method is sensitive to about 0.04 microgram arsenic in the total digest (injections of 20 muL of a 4 ng/mL solution).

Animals↗

PubMedDate not supplied

Feeds.

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6-Phytase↗

PubMedDate not supplied

Determination of selenium in feeds and premixes: collaborative study.

A total of 17 laboratories participated in a collaborative study for the determination of selenium in feeds and premixes using either a fluorometric or a continuous hydride generation atomic absorption (HGAA) method. Each collaborator analyzed 16 blind duplicate samples of feed and premixes from various feed manufacturers. The amount of Se in these materials ranged from 0.2 to 5500 micrograms/g. Six laboratories used only the fluorometric procedure, 8 laboratories used only the hydride generation atomic absorption procedure, and 3 laboratories used both procedures. One laboratory in the fluorometric study and 3 laboratories in the HGAA study were initially excluded because of invalid data. Poor agreement between the blind duplicates indicated probable sample interchange and/or dilution error. The data from 8 laboratories were submitted to statistical analysis, including data from 2 laboratories participating in both studies. The repeatability standard deviation (RSDr) for samples analyzed by the fluorometric procedure ranged from 5.9 to 33%, and the reproducibility standard deviation (RSDR) ranged from 12 to 33%. RSDr for samples analyzed by HGAA ranged from 2.8 to 18%, and RSDR ranged from 4.0 to 36%. Both fluorometric and continuous hydride generation atomic absorption methods for the determination of Se in feeds and premixes have been adopted first action by AOAC INTERNATIONAL.

Animal Feed↗

PubMedDate not supplied

Determination of water in forages and animal feeds by Karl Fischer titration.

Oven methods for determining moisture (volatiles) in forages and other animal feeds are empirical. The moisture concentration obtained depends upon the time and temperature the sample was dried and is influenced by the presence of other volatiles than water. A validated reference method to measure water in forages and animal feeds could be used to evaluate the appropriateness of oven methods for various types of animal feeds and forages. Karl Fischer titration is a well-established method for determining water. However, thorough extraction of water from forages and feeds is a challenge because they often contain cellular structures that release water slowly. Water was successfully extracted into methanol-formamide (50 + 50) by high-speed homogenization and then titrated directly at 50 degrees C with a one-component Karl Fischer reagent based on imidazole. The method is described in detail, results of day-to-day repeatability and laboratory-to-laboratory reproducibility are reported, and preliminary comparison data between oven methods are provided.

Analysis of Variance↗