https://www.amjmed.com/article/0002-9343(71)90320-2/pdf

The infrequency of hypercalcemia in sarcoidosis

This article will review the methods currently employed for measuring the concentrations of total and ionized calcium in serum or plasma. As far as total calcium is concerned, various techniques such as atomic absorption spectrometry, spectrophotometry, fluorometry, complexometric titration, and flame photometry will be described and compared. Particular emphasis will be given to the accuracy and precision of each technique. Possible sources of error and interfering agents will be identified and the various procedures for the taking and handling of blood samples evaluated. Inter-laboratory variation in the measurement of calcium will be studied. An assessment will be made of a new reference method for measuring total calcium in serum using isotope-dilution mass spectrometry. The usefulness of the total calcium measurement in clinical medicine will be briefly discussed. Within the last decade the refinement of spectrophotometric techniques and the improvements in ion-selective electrode technology have revolutionized the measurement of ionized calcium in serum, such that it may now be possible to replace total calcium measurements with ionized calcium measurements on a routine basis. The various techniques currently in use for measuring ionized calcium will be described and evaluated. Particular attention will be paid to the preparation of standards, the procedures for taking blood samples, and the handling of the samples prior to and during measurement. An assessment of the relative value of measuring total and ionized calcium will be presented.

Calcium measurements in serum and plasma--total and ionized.

Chemical interference by drugs and other substances with clinical laboratory test procedures.

A completely automated analysis is described for the determination of serum calcium with glyoxal bis (2-hydroxyanil) solution (GBHA). The method is simple and precise, and the data obtained are in good agreement with results obtained by the manual GBHA procedure.

An Automated Method for the Determination of Serum Calcium with Glyoxal Bis (2-Hydroxyanil)

Phytic acid (PA) is the main way to store phosphorus in plants, representing about 60–82 % of the total content of phosphorus. The PA determination is still an analytical dare due to low chemical reactivity of this compound. The present work developed a simple and sensitive spectrophotometric method for phytic acid determination on a basis of a colored complex formation between glyoxal bis(2-hydroxianiline) (GBHA) and calcium ions in an alkaline medium (pH 12.5), inhibited by phytic acid presence. The selectivity of the method was evaluated for 15 possible interferences among anions and cations. The main figures of merit from the method in aqueous solution and optimized conditions presented a linear range from 1.0 to 12.5 mg L−1 (n = 8) for analytical curve A = −0.037C
 PA + 0.72 (r = 0.9981), limit of detection (LOD) equivalent to 0.33 mg L−1, and relative standard deviation (RSD) less than 2.7 %. The proposed method was applied to determine phytic acid in different grain bran/flour samples, the results when compared with reference procedure (Wade method) had no significant difference (significant level of 95 %). Additionally, to explore more applications, the proposed method was employed to determine phytic acid concentration in cream for skin whitening, with recovering of more than 86 %. Therefore, according to the results, the method was versatile with good precision, accuracy, and detection limit similar or better than other works described in the literature.

Simple and Sensitive Spectrophotometric Method for Phytic Acid Determination in Grains

A spectrophotometric method for the direct determination of microgram quantities of calcium in serum is presented. In this procedure, 0.02 ml. of serum is interacted with buffered glyoxal bis (2-hydroxyanil) solution (GBHA) at pH 12.6. The resultant red calcium-GBHA complex is diluted in methanol-acetone-water solution, and the absorbance determined at 520 mµ. The effects of pH, temperature, GBHA concentration, and alcohol-water ratio were evaluated, as was interference by serum constituents. The method is simple and precise, and the analytical results compare well with the chloranilate procedure for serum calcium.

Genevieve Farese

Papers

Direct photometric analysis of serum calcium with glyoxal bis (2-hydroxyanil).