Feces fecal samples, preparation

The use of stable isotopes or tracers to study zinc absorption in humans with subsequent analysis by mass spectrometry has been reported in the literature. Analysis of fecal samples obtained 3 and 6 days after the administration of zinc-65 isotope in food showed that between 45% and 75% of zinc isotope was absorbed (Johnson 1982). The results indicated satisfactory detection of the zinc-67 isotope in human feces, while the zinc-70 isotope was not as detectable. Better precision and recovery were obtained for the zinc-67 isotope (2.4% CV >95% recovery) than for the zinc-70 isotope (38% CV 71% recovery). Sampie detection limits were not reported. Total reported sample preparation time was <2 hours, and it took only 5-10 minutes to anaiyze each sample on the mass spectrometer. 

Highlights Analytical procedures for bioassays of uranium in blood and feces have been developed and used in a limited number of studies. Compared to urinalysis, the collection and handling of blood and feces are complicated and entail special procedures. The preparation of fecal samples involves dry-ashing at an elevated temperature and then acid digestion. For alpha spectrometry, separation, purification, and deposition precede counting (that could last several days per sample). Other analytical techniques described in the literature include neutron activation analysis, but ICPMS is currently more widely used. 

In humans, radiolabled Cg-NP was administered to two male volunteers (5 mg as a oral dose to one volunteer, and 1 mg intravenously to the second volunteer) and blood, urine, and fecal samples were monitored over time (Muller et al. 1998). Because less than 1 % of the dose was excreted in the feces as NP, and the bioavailability of administered NP was calculated to be about 20 % (oral dose), the authors suggested that after absorption by the gastrointestinal tract, NP was metabolized in the gut wall as well as in the liver. Studies using microsomes prepared from rat intestinal tissue found that while NP was glucuronidated within... 

The excretion of uranium in fecal material results primarily from intakes by ingeshon, and includes uranium swallowed after inhalation. Usually, uranium will appear in feces within hours after intake thus providing a rapid means of determining whether an intake has occurred. Fecal analysis requires prechemistry preparation that includes ashing of the sample, cleaning by co-precipitation, and solvent extraction followed by electrodeposition. Alpha spectroscopy is then performed (Singh and Wrenn 1988). Urinalysis is typically favored over both fecal and blood analysis because it is generally more sensitive and less costly, and because fecal analysis provides no uptake or retention information and blood analyses is invasive. 

In vitro radioactive strontium analyses are routinely performed in support of a personnel monitoring program, or in cases where the size of an operation does not justify the cost of whole body counter facilities. These analyses are usually done on urine samples, but other types of body materials (e.g., feces or blood) may also be used. Urinalysis is effective for analysis of transportable or soluble strontium. Strontium may also be measured in fecal material using the same methods identified above for urinalyses, except that this matrix requires extensive preparation. 

For urine analysis sample aliquots are diluted 1 1 with distilled water before application to the AAS stabilized temperature platform (Leung and Henderson, 1982). Fecal analysis require considerably more complicated preparation steps than serum or urine. The procedure developed in the author s laboratory (Brown et al., manuscript in preparation) is summarized as follows Frozen specimens are thawed and distilled water is added (1 mL per 2 g feces) and the sample is homogenized in a sealed container on a paint shaker. A 10 mL aliquot is ashed at 550°C in a muffle furnace, dissolved in dilute HNO3 snd analyzed by GF-AAS. 

For the collection of urine we used small metabolic cages. Urine was collected several hours before the experiments and stored at room temperature (18—20 C) it was usually used within 3 hours. For presentation, 0.1 ml of prepared sample (we mixed all undiluted urine volume from 3 donors) was applied to cotton swabs. The feces were collected directly after excretion. For presentation we used 2—3 fecal boli of different donors. Mid-ventral gland secretion was collected by rubbing the gland directly with water soaked cotton swabs. Three swabs contaminated with secretion (about 1—2 mg from each donor) were put in 1 ml of cold water for mixing of individual odors. For presentation 0.1 ml of prepared sample was applied to a clean cotton swab. 

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