Calcium sample preparation

FIGURE 19 Choline in infant formula. Columns 4x250mm lonPac CSI2A, and 4x50mm CGI2A. Flow rate I mLmin. Eluent l8mM MSA. Injection volume lOpL. Detection suppressed conductivity, CSRS (4 mm), recycle mode. Ions I— sodium 2—ammonium 3—choline 4—potassium 5—magnesium 6—calcium. Sample preparation add 30 mL of I M HCI to 5 g sample, mix well, place in 70°C water bath for 3 h, cool, filter and dilute to 100 mL. 

In a study of dental silicate cements, Kent, Fletcher Wilson (1970) used electron probe analysis to study the fully set material. Their method of sample preparation varied slightly from the general one described above, in that they embedded their set cement in epoxy resin, polished the surface to flatness, and then coated it with a 2-nm carbon layer to provide electrical conductivity. They analysed the various areas of the cement for calcium, silicon, aluminium and phosphorus, and found that the cement comprised a matrix containing phosphorus, aluminium and calcium, but not silicon. The aluminosilicate glass was assumed to develop into a gel which was relatively depleted in calcium. 

Sample preparation is rather involved. A sample of urine or fecal matter is obtained and treated with calcium phosphate to precipitate the plutonium from solution. This mixture is then centrifuged, and the solids that separate are dissolved in 8 M nitric acid and heated to convert the plutonium to the +4 oxidation state. This nitric acid solution is passed through an anion exchange column, and the plutonium is eluted from the column with a hydrochloric-hydroiodic acid solution. The solution is evaporated to dryness, and the sample is redissolved in a sodium sulfate solution and electroplated onto a stainless steel planchette. The alpha particles emitted from this electroplated material are measured by the alpha spectroscopy system, and the quantity of radioactive plutonium ingested is calculated. Approximately 2000 samples per year are prepared for alpha spectroscopy analysis. The work is performed in a clean room environment like that described in Workplace Scene 1.2. 

Analytical methods for monitoring the compounds were developed or modified to permit the quantification of all 23 compounds of interest. As noted earlier, the compounds were initially studied in small-scale extractions by groups. This approach assured minimal interferences in the analyses conducted during the initial supercritical fluid carbon dioxide extractions. Table II summarizes the data on the recovery of organics from aqueous samples containing the compounds of interest at concentration levels listed in Table I when the sample preparation techniques and analytical methods described were used. For each experimental run, blank and spiked aqueous samples were carried through the sample prepration and analytical finish steps to ensure accurate and reproducible results. Analyses of sodium, calcium, and lead content were also conducted on selected samples by using standard atomic ab-... 

Figure 1. Crystals of calcium phosphate (arrows) in an unstained smear of a cheese sauce product. A small sample of the product was placed on a slide and observed by Kohler Illumination. If quantification is necessary, sample preparation is easily standardized to allow for particulate enumeration, (x 80)...

The data in Table IV for the three samples of hydroxyapatite summarize the range for shifts in these samples of hydroxyapatite. Shifts have not been observed in commercially available hydroxyapatites, one sample of natural apatite, or calcium phosphates. Likewise, calcium phosphates prepared by methods which yield high specific surface have also not responded in this manner to adsorbates. 

Sample Preparation Proceed as directed for the Standard Preparation, using an accurately weighed amount of sample equivalent to about 15 mg of Calcium Pantothenate that has been previously dried at 105° for 3 h. 

Procedure Concomitantly determine the absorbance of each Standard Preparation and of the Sample Preparation at 422.7 nm, with a suitable atomic absorption spectrophotometer, following the operating parameters as recommended by the manufacturer of the instrument. Plot the absorbance of the Standard Preparations versus concentration of calcium, in micrograms per milliliter, and from the curve so obtained determine the concentration, C, in micrograms per milliliter, of calcium in the Sample Preparation. Calculate the quantity, in milligrams, of calcium in the sample taken by the formula... 

Procedure Add 5 mL of Buffer Solution Final Preparation, 1 mL of a 1 20 potassium cyanide solution, and 5 drops of eriochrome black TS or another suitable indicator to the Sample Preparation. Begin stirring with a magnetic stirrer, and titrate with Standard EDTA Solution to a true blue endpoint, recording the volume, in milliliters, required as V. Calculate the milligrams per kilogramof total calcium and magnesium (both expressed as Ca) in the sample by the formula... 

Table I lists the results of this experiment. A metallic calcium sample was prepared from limestone from an 11-m depth and was not preenriched. The sample was assumed to contain no cosmogenic 41Ca at the instrumental detection limit of the AMS system used, because of its geological age (Mesozoic) and burial depth. No counts were observed for a time approximately three times longer than that for the bone sample. From the measurement...

All reactions and sample preparations are carried out in an inert-atmosphere enclosure under dry nitrogen. Solvents and reagents are dried in the following manner. Benzene, tetrahydrofuran, and n-pentane are freshly distilled from lithium aluminum hydride pyridine is distilled over barium oxide and tetramethylethylenediamine is distilled over calcium hydride. Solvents used in preparing nmr and infrared samples are degassed by a freeze-thaw technique. Nmr spectra are obtained with torch-sealed nmr tubes. The commercial transition metal carbonyl complexes are recrystallized and vacuum-dried before use. Glassware is routinely flame-dried. 

Stewart et al. (S8) estimated magnesium in serum and urine. Of four different methods of sample preparation (i.e., wet-ashing, deproteiniza-tion, simple dilution with water, and dilution with hydrochloric acid), deproteinization with trichloroacetic acid was found to be most satisfactory. No interference was seen from sodium, potassium, or phosphate, but sulfate produced depression. With protein a 6% decrease in the apparent magnesium concentration was seen. Calcium and sulfate were added to standards and samples to control sulfate depression. 

High-performance liquid chromatography is performed using a Hewlett-Packard 1090 chromatograph equipped with a ternary-solvent delivery system, an autoinjector with a 0 -20- u.L injection loop, an oven compartment, and a diode-array UV detector. An ELS detector (Alltech Associates, Deerfield, IL) is connected in series to the UV detector. Hexane, 2-propanol, and water were used for the analysis of nonionic surfactants. Water and tetrahydrofuran (THF) are used for the analysis of anionic surfactants. No preliminary sample preparation is used other than dilution. The nonionic surfactants are diluted 1 40 (v/v) with hexane. The anionic surfactants (alkyl ether sulfates and synthetic and petroleum sulfonates) are diluted 1 20 (v/v) with water-THF (50 50). The calcium sulfonate surfactants were diluted 1 20 (v/v) with a THF-38% hydrochloric acid solution of pH 1. Hydrochloric add is required to prevent salt precipitation by converting any excess water-insoluble caldum carbonate into water-soluble calcium chloride. All diluted samples are... 

One of the requirements of any nuclear facility is to monitor the effluent uxiste water to show compliance with existing standards. This paper describes a sequential procedure for the separation of the transuranic elements from water samples up to 60 1. The elements of interest are coprecipitated with calcium fluoride and then individually separated using a combination of ion exchange and solvent extraction, with a final sample preparation by electrodeposition. Alpha spectrometry of these samples allows the measurement of neptunium, plutonium, and transplutonium nuclides at sub-fCi/l, levels. 

---