Determination of calcium and magnesium

Discussion. Patton and Reeder s indicator (HHSNNA), see Section 10.48, makes it possible to determine calcium in the presence of magnesium, and is 

Metal Titration type pH Buffer Indicator (Note 1) Colour change (Note 2) Notes 

Calcon may also be used for the titration of calcium in the presence of magnesium (compare Section 10.48). The neutral solution (say, 50 mL)is treated with 5 mL of diethylamine (giving a pH of about 12.5, which is sufficiently high to precipitate the magnesium quantitatively as the hydroxide) and four drops 

Procedure. Prepare the indicators by grinding (a) 0.5 g HHSNNA with 50 g potassium chloride, and (b) 0.2 g solochrome black with 50 g potassium chloride. The following solutions will also be required  

Magnesium chloride solution (0.01 Mj. Dissolve 0.608 g pure magnesium turnings in dilute hydrochloric acid, nearly neutralise with sodium hydroxide solution (1M) and make up to 250 mL in a graduated flask with de-ionised water. Pipette 25 mL of the resulting 0.1M solution into a 250 mL graduated flask and make up to the mark with de-ionised water. 

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Lochmuler, C. Atomic Spectroscopy—Determination of Calcium and Magnesium in Sand with a Statistical Treatment of Measurements published on the web at http //www.chem.duke.edu/ clochmul/exp4/exp4.html. 

Traces of many metals interfere in the determination of calcium and magnesium using solochrome black indicator, e.g. Co, Ni, Cu, Zn, Hg, and Mn. Their interference can be overcome by the addition of a little hydroxylammonium chloride (which reduces some of the metals to their lower oxidation states), or also of sodium cyanide or potassium cyanide which form very stable cyanide complexes ( masking ). Iron may be rendered harmless by the addition of a little sodium sulphide. 

We have found that the use of serum standards for standardizing the instrument in the laboratory is useful. However, the serum standards cannot be used for urines. In urines, one runs into other problems and needs to use aqueous standards. Therefore, at present, while atomic absorption is the instrument of choice, there is much to be desired for the determination of calcium and magnesium in the routine laboratory of clinical chemistry. 

Atomic absorption spectrophotometry [165,166] has been used in the determination of calcium and magnesium in seawater. 

International Standard Organization. 1986. Water quality. Determination of calcium and magnesium. Atomic absorption spectrometric method. ISO 7980. International Organization for Standardization, Case Postale 56, CH-1211, Geneva 20 Switzerland. 

Liquid chromatography was used by Rho and Choi [46] for the simultaneous determination of calcium and magnesium. A column of 4.6mm by 25cm, containing Zipax SCX was used for the separation. Linear calibration curves were obtained in the range of 1x 10-4 to 5x 10 4M and the correlation coefficient of the calibration curves was in the range of 0.9952-0.9996. 

R. M. Pollman, Atomic absorption spectrophotometric determination of calcium and magnesium and colorimetric determination of phosphorus in cheese collaborative study, J. Assoc. Off. Anal. Chem., 74 (1991), 27 -31. 

A. N. Araujo, R. C. C. Costa, J. L. F. C. Lima, B. F. Reis, Sequential injection system in flame atomic absorption spectrometry for the determination of calcium and magnesium in mineral waters, Anal. Chim. Acta, 358 (1998), 111-119. 

D13. Decker, C. F., Aras, A., and Decker, L. E., Determination of calcium and magnesium in human cerebrospinal fluid by atomic absorption spectroscopy. Abstr. Am. Chem. Soc., Div. Biol. Chem., Dec. 1963 p. 7A. 

K2. Kramer, B., and Tisdall, F. F., A simple technique for the determination of calcium and magnesium in small amounts of serum. J, Biol. Chem. 47, 475-481 (1921). 

A chemometric method for simultaneous determination of calcium and magnesium in natural waters using Arsenazo III and FIA system was described [5], The concentrations of the analytes were calculated by the H-point standard addition method for ternary mixtures. 

A.R.A. Nogueira, S.M.B. Brienza, E.A.G. Zagatto, J.L.F.C. Lima, A.N. Araujo, Flow injection system with multisite detection for spectrophotometric determination of calcium and magnesium in soil extracts and natural waters, J. Agric. Food Chem. 44 (1996) 165. 

D.G. Themelis, P.D. Tzanavaras, A.V. Trellopoulos, M.C. Sofoniou, Direct and selective flow-injection method for the simultaneous spectrophotometric determination of calcium and magnesium in red and white wines using online dilution based on "zone sampling," J. Agric. Food Chem. 49 (2001) 5152. 

The determination of sodium and potassium in biological fluids and tissues is so widely practiced that no detailed discussion is necessary. A simple filter instrument with absorption or interference filters is perfectly adequate for most purposes. However, the determination of calcium and magnesium in biological fluids and tissues has proved more difficult and merits further discussion. 

The methods in use in the author s laboratory for determination of calcium and magnesium in plasma and urine and in fecal and tissue ash are described below in detail. Willis (W2) has shown that absorption methods are also suitable. The methods described here have proved reliable in practice over several years of intensive use. 

Recently, the determination of calcium and magnesium by atomic absorption spectrometry is preferred gravimetric and manganometric determinations after elimination of calcium in the form of calcium oxalate are losing their importance [14]. 

T. Uchida, C. S. Wei, C. lida, and H. Wada, Simultaneous Determination of Calcium and Magnesium in Serum with Flow Injection-Atomic Absorption System [in Japanese]. Nagoya Kogyo Daisako Gakuho, 33 (1982) 97. 

B. F. Rocks, R. A. Sherwood, and C. Riley, Direct Determination of Calcium and Magnesium in Serum Using Flow Injection Analysis and Atomic Absorption Spectroscopy. Ann. din. Biochem., 21 (1984) 51. 

A. T. Haj-Hussein and G. D. Christian, Multicomponent Flow Injection Analysis Using Spectrophotometric Detection with Reagent Spectral Overlap Application to Determination of Calcium and Magnesium in Blood Serum Using Eriochrome Black T. Microchem. J., 34 (1986) 67. 

A method for simultaneous spectrophotometric determination of calcium and magnesium is based on... 

Krenn, K. Tanzer, D. Test strip for the determination of calcium and magnesium in aqueous solutions using o-cresolphthalein. PCX Int. Appl. WO 2002046742, 2002 Chem. Abstr. 2002,137, 14975. 

One of the most important applications of FAAS in the routine clinical chemistry laboratory is the determination of calcium and magnesium in blood serum and other body fluids. The samples are diluted 1 20 to 1 50 with a buffer such as EDTA, lanthanum, or strontium and analyzed directly in an air-acetylene flame. Paschen [6] describes a micromethod for the determination of sodium, potassium, calcium, and magnesium in a single-serum dilution. One hundred microliters of serum is diluted 1 50 with 0.25% (w/v) strontium chloride solution and analyzed directly. The addition of strontium eliminates the influence of phosphate on calcium and the ionization of sodium and potassium. 

Dionex Corporation (1998) Dionex Application Note No. 120 Determination of Calcium and Magnesium in Brine. Dionex Corporation (now part of... 

Protective agents prevent interference by forming sfable but volatile species with the analyte Three common reagents for this purpose are elhylenedi-aminetetraacetic acid (EDTA). 8-hydroxyquinoline, and APCD, which is the ammonium salt of 1-pyrro-lidinecarbodithioic acid. The presence of EDTA has been shown to eliminate the interference of aluminum, silicon, phosphate, and sulfate in the determination of calcium. Similarly. 8-hydroxyquinoline suppresses the interference of aluminum in the determination of calcium and magnesium. 

M. C. Yebra, Flow injection determination of calcium and magnesium in soluble pharmaceutical tablets by flame atomic absorption spectrometry using ultrasound for sample preparation, At. Spectrosc., 2011, 32(2), 80-84. 

For calcium and magnesium, ignite about 2 g of the powdered lozenges at a temperature not exceeding 500° until all the carbon is removed and then dissolve the residue in a mixture of 6 ml of water and 3 ml of concentrated nitric acid. Add 2 ml of dilute hydrochloric acid and 150 ml of water and then add dilute ammonia solution until the solution remains just acid to litmus paper. Boil for two minutes, cool to 15°, filter into a 250-ml graduated flask and dilute to volume with water. Proceed as described for the determination of calcium and magnesium in Compound Mixture of Calcium Carbonate for Infants (p. 154) using two 50-ml aliquots of the solution instead of the two 20-ml aliquots of solution A directed in that assay. 

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