Calcium chelation value

The calcium chelation value of a substance can be determined by an oxalate titration. In this method [12], a sample of the product to be tested is added to a sodium oxalate solution at pH 10 to 12. The mixture is then titrated with a solution containing calcium ions. When the chelate becomes depleted the endpoint can be noted by the precipitation of insoluble calcium oxalate. The calcium chelation value (CV) is reported as mg of calcium chelated per gram of chelate. The CV of Na LED3 A was determined at a range of concentrations. The results are presented in Figure 7. EDTA chelates 260 mg CaCOj/g irrespective of system concentration. 

Hampshire Chemical Corp., Data Sheet, Analytical Procedure for Calcium Chelation Value, HCT 16. 

Morgan JM, Navabi H, Jasani B. Role of calcium chelation in high-temperature antigen retrieval at different pH values. J. Pathol. 1997 182 233-237. 

Nitrilotriacetic acid trisodiura salt, monohydrate. High purity dry form of PERMA KLEER NTA 150. White crystalline power. Chelating value at pH 11 355 mg calcium per g... 

PLEX PC is a modified diethylene triamine pentaacetic acid calcium-sodium salt. It contains a minimum of 30.0% active agent. The chelating values (CV) are in the table below. 

Chelating Values by the Copper PAN method and by AATCC Method 149-1985 (Calcium Oxalate Method) for PLEX HT are cited below. 

The Ca(Il) coaceatratioa ia blood is closely coatroUed aormal values He betweea 2.1 and 2.6 mmol/L (8.5—10.4 mg/dL) of semm (21). The free calcium ion concentration is near 1.2 mmol/L the rest is chelated with blood proteias or, to a lesser extent, with citrate. It is the free Ca(Il) ia the semm that determines the calcium balance with the tissues. The mineral phase of bone is essentially ia chemical equiUbrium with calcium and phosphate ions present ia blood semm, and bone cells can easily promote either the deposition or dissolution of the mineral phase by localized changes ia pH or chelating... 

There are available also several kits for the assay of calcium, in 10 or 20 microliter samples by chelate formation colorimetrically or fluorimetrically. (Pierce Chem. Co., Rockford, 111.). These are read either with the spectrophotometer or by spectrofluorometry. In our experience, while these systems can be used for approximate results, the plot of concentration versus reading curves are rather flat and only an approximation of the values can be obtained. This may be very important late at night or at times when the atomic absorption machine is down, but if the atomic absorption instrument is available it should be used in preference to these procedures. 

Urinary lead levels have also been used to measure current exposure (Robinson 1974) but they are of questionable value as biomarkers of exposure because of the relatively low and fluctuating lead levels that are excreted in the urine (ACGIH 1986 Ibels and Pollock 1986 Jensen 1984). In contrast, the determination of urinary lead following a single injection of the chelating agent, calcium disodium EDTA, which mobilizes extracellular lead and produces increased urinary excretion of lead, is presumed to be indicative of an elevated body burden of lead (Cory-Slechta et al. 1987 Ibels and Pollock 1986 Janin et al. 1985). Children whose PbB levels are 45 pg/dL should not receive a provocative chelation... 

Tetracyclines have the tendency to form chelates with bivalent metal ions. As a consequence of their affinity to calcium, tetracyclines tend to accumulate in the bones of treated animals. Although their chelates with calcium show considerable stability, tetracyclines can be extracted from bones containing these drugs and, therefore, may be present in soups and meals when bones from treated animals are cooked (80, 81). The extractability of chlortetracycline from bone tissue is strongly pH-dependent, being higher at low pH values. This can be easily explained by the dependence of the dissociation constant of the chelate from the pH value. 

The calibration procedure is simplified by applying the calibration formula developed by Grynkiewicz et al. (6) by using two extreme values for Ca2+ concentration (namely zero and infinite concentrations) and by using the original Kd determined in vitro which, for unknown reasons, has become the routinely used standard value under various experimental circumstances. The most commonly used procedure is the addition of ionophores. EGTA used at a concentration of 180 mM is added to the solution to chelate all free Ca2+ (Fmin) and then HC1 (1M) is added to lyse the cell. Consequently the dye is saturated with calcium (Fmax). 

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