Chloride in biological fluids

Schales, O., and Schales, S. S., Simple and accurate method for determination of chloride in biological fluid.. Biol. Chem. 140, 879-884 (1941). 

Schales O, Schales SS. A simple and accurate method for the determination of chloride in biological fluids. J Biol Chem 1941 140 879-84. 

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. 

A comparative study was made of the RP-HPLC analysis of free amino acids in physiological concentrations in biological fluids, with pre-column derivatization by one of the four major reagents o-phthalaldehyde (73) in the presence of 2-mercaptoethanol, 9-fluorenylmethyl chloroformate (90), dansyl chloride (92) and phenyl isothiocyanate (97, R = Ph) (these reagents are discussed separately below). Duration of the analysis was 13-40 min. Sensitivity with the latter reagent was inferior to the other three however, its use is convenient in clinical analysis, where sample availability is rarely a problem. The derivatives of 73 were unstable and required automatized derivatization lines. Only 92 allowed reliable quantation of cystine. All four HPLC methods compared favorably with the conventional ion-exchange amino acid analysis188. 

A rapid method (31) for the determination of salicylate in biological fluids is presented, based on a reagent containing ferric nitrate, mercuric chloride and hydrochloric acid, which precipitates the proteins and simultaneously reacts with salicylic acid to give a purple color. 

One of the earliest methods for determining CP in biological fluids is mentioned here for historical purposes. A protein-free filtrate of specimen is titrated with mercuric nitrate solution in the presence of diphenylcarbazone as an indicator. Free Hg combines with CP to form soluble but essentially nonionized mercuric chloride ... 

An even more serious source of error in biologic fluid measurements by electrodes is the reference electrode. The biological scientist is probably more aware of, and frustrated by, reference electrode problems than any other type of electrode user. While the reference element of the electrode, be it mercury/calomel or silver/silver chloride, is usually stable, well-defined and trouble-free, the liquid junction between the internal reference solution and the sample solution is rather poorly understood except for the simplest electrolyte systems. 

Seligson, S. McCormick. G. J. and Sleeman, R. Electrometric method for the determination of chloride in serum and other biological fluids. Clin. Chem. (1958), 4, 159 -169. 

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). 

The individual activity coefficients calculated from (4.12), suitable for calibration of ISEs for chloride ions, the alkali metal and alkaline earth ions, are given in tables 4.1 and 4.2. Ion activity scales have also been proposed for KF [141], choline chloride [98], for mixtures of electrolytes simulating the composition of the serum and other biological fluids (at 37 °C) [106,107], for alkali metal chlorides in solutions of bovine serum albumine [132] and for mixtures of electrolytes analogous to seawater [140]. 

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