Calcium in biological fluids

A carrier satisfying all of the basic requirements for the determination of calcium in biological fluids—ETH 1001—was invented in the early... 

Bowers GN Jr, Rains TC. Measurement of total calcium in biological fluids flame atomic absorption spectrometry. Methods Enzymol 1988 158 302-19. 

Sena SF, Bowers GN Jr. Measurement of ionized calcium in biological fluids ion-selective electrodes method. Methods Enzymol 1988 158 320-34. 

Determination of Magnesium and Calcium in Biological Fluids and Tissues... 

Ml. MacIntyre, I., The flame-spectrophotometric determination of calcium in biological fluids and an isotopic analysis of the errors in the Kramer-Tisdall procedure. Biochem. f. 67, 164-172 (1957). 

The only common redox titration applied in the clinical laboratory is for the analysis of calcium in biological fluids. Calcium oxalate is precipitated and filtered, the precipitate is dissolved in acid, and the oxalate, which is equivalent to the calcium present, is titrated with standard potassium permanganate solution. This method is largely replaced now by more convenient techniques such as complex-ometric titration with EDTA (Chapter 9) or measurement by atomic absorption spectrophotometry (Chapter 17). 

P. Premoli, A. Manzoni and C. Calzi, Method for the Quantitative Determination of Calcium in Biological Fluids through Direct Potentiometry, European Patent No EP 0153783 Bl, October 30, 1991. 

From rudimentary beginnings, the calcium ISE has become a reliable and widely applied analytical sensor which meets many, but not all, of the above ideal criteria. The developments in calcium ISE have been prompted mainly by the interest shown in analytical methods for the determination of ionised calcium in biological fluids. Methods for the potentiometric determination of calcium ion followed from the discovery of the glass electrode selective for hydrogen ion. ... 

Calcium may be determined by atomic absorption spectrophotometry. This technique has been used for the estimation of calcium in biological fluids and agricultural materials. It is a speedy method, superior to the more tedious chemical determination by oxalate precipitation and more specific than the EDTA titration method. The accuracy is of the order of 2 per cent and sensitivity limits have been reported at 0 08 to 1 p.p.m. of calcium in solution. The interference problems are very similar to those experienced with the emission method although not quite so formidable. 

Ion Selective Electrodes Technique. Ion selective (ISE) methods, based on a direct potentiometric technique (7) (see Electroanalytical techniques), are routinely used in clinical chemistry to measure pH, sodium, potassium, carbon dioxide, calcium, lithium, and chloride levels in biological fluids. 

E. W. Moore, Studies with ion-exchange calcium electrodes in biological fluids ... 

P. Venkateswarlu, L. Singer, W.D. Armstrong, Determination of ionic (plus ionizable) fluoride in biological fluids. Procedure based on adsorption of fluoride ion on calcium phosphate. Anal. Biochem. 42 (1971) 350-359. 

However, as already mentioned earlier, high pressure liquid chromatography with tandem mass spectrometric detection (LC-MS/MS) has evolved in the last few years as the major bioanalytical technique for the bioanalysis of analytes in biological matrices. This is reflected also in a number of LC-MS/MS assays for the determination of dihydropyridine calcium antagonists in biological fluids (Carvalho et al. 2001, Schug et al. 2002 Kang et al. 2004). 

Malcik N, Ferrance JP, Caglar P, Landers JP. Development of a microchip sensor for calcium detection in biological fluids. In preparation. 

M20. Moore, E. W., Studies with ion exchange calcium electrodes in biological fluids some applications in biomedical research and clinical medicine. In Ion-Selective Electrodes (R. A. Durst, ed.), pp. 215-285. Nat. Bur. Stand. (U.S.), Spec. Publ. 314 (1969). 

When the requirement is for many routine analyses of sodium and potassium, a simple filter fiame photometer burning a low temperature flame should be purchased. Many such models are on the market. On the other hand, if analysis for calcium and magnesium in biological fluids is also required, then only a fairly complex instrument with monochromator, photomultiplier, and high-temperature flame is satisfactory (Fig. 4). Compromise instruments between these two extremes lose the simplicity of the first type without gaining the versatility of the second. 

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. 

Parathyroid hormone can be assayed by its phosphaturic effect in mice (D2), its calcemic effect in parathyroidectomized rats (Dl, Mil), its effect on serum calcium in the dog (Ul), and its effect on the excretion of isotopic calcium or phosphate in the urine after the labeling of rats with Ca or P (C8, C9). None of these methods is particularly sensitive, and for this reason little work has been done on the estimation of parathyroid hormone in biological fluids. An attempt has been made to meas-... 

Turner et al. (1960) devised a rapid infrared method by which DjO can be determined in biological fluids, including plasma water. The error of this analytical procedure is 1 %, and as many as 50 plasma samples may be processed and analyzed in a single day. Neely et al. (1962) applied this method to study the possibility of the absorption of water by the body through the skin. A small animal is placed in a specially constructed chamber which encloses the body up to the neck. The chamber is filled with an H2O-D2O vapor. Plasma water in blood samples taken from the animal is analyzed in a calcium fluoride cell against a plasma water blank at 2513 cm . The results of Turner et al. indicated that D2O moved into the animal (dog) body water at the rate of 45 grams per square meter per hour. 

Calcium activities as low as 5 x 10 7 M can be measured, with selectivity coefficients ACaMg and ACaK of 0.02 and 0.001, respectively. Such potential response is independent of the pH over the pH range from 5.5 to 11.0. Above pH 11, Ca(OH)+ is formed, while below pH 5.5, protons interfere. Because of its attractive response characteristics, the calcium ISE has proved to be a valuable tool for the determination of calcium ion activity in various biological fluids. 

Clinical chemistry, particularly the determination of the biologically relevant electrolytes in physiological fluids, remains the key area of ISEs application [15], as billions of routine measurements with ISEs are performed each year all over the world [16], The concentration ranges for the most important physiological ions detectable in blood fluids with polymeric ISEs are shown in Table 4.1. Sensors for pH and for ionized calcium, potassium and sodium are approved by the International Federation of Clinical Chemistry (IFCC) and implemented into commercially available clinical analyzers [17], Moreover, magnesium, lithium, and chloride ions are also widely detected by corresponding ISEs in blood liquids, urine, hemodialysis solutions, and elsewhere. Sensors for the determination of physiologically relevant polyions (heparin and protamine), dissolved carbon dioxide, phosphates, and other blood analytes, intensively studied over the years, are on their way to replace less reliable and/or awkward analytical procedures for blood analysis (see below). 

Phosphates and phosphonates Protein binding studies, calcium in sewage water, mineral water, blood serum, biological fluid 131... 

Liquid membranes of the water-in-oil emulsion type have been extensively investigated for their applications in separation and purification procedures [6.38]. They could also allow extraction of toxic species from biological fluids and regeneration of dialysates or ultrafiltrates, as required for artificial kidneys. The substrates would diffuse through the liquid membrane and be trapped in the dispersed aqueous phase of the emulsion. Thus, the selective elimination of phosphate ions in the presence of chloride was achieved using a bis-quaternary ammonium carrier dissolved in the membrane phase of an emulsion whose internal aqueous phase contained calcium chloride leading to phosphate-chloride exchange and internal precipitation of calcium phosphate [6.1]. 

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