Oxalate in urine

Two nucleation processes important to many people (including some surface scientists ) occur in the formation of gallstones in human bile and kidney stones in urine. Cholesterol crystallization in bile causes the formation of gallstones. Cryotransmission microscopy (Chapter VIII) studies of human bile reveal vesicles, micelles, and potential early crystallites indicating that the cholesterol crystallization in bile is not cooperative and the true nucleation time may be much shorter than that found by standard clinical analysis by light microscopy [75]. Kidney stones often form from crystals of calcium oxalates in urine. Inhibitors can prevent nucleation and influence the solid phase and intercrystallite interactions [76, 77]. Citrate, for example, is an important physiological inhibitor to the formation of calcium renal stones. Electrokinetic studies (see Section V-6) have shown the effect of various inhibitors on the surface potential and colloidal stability of micrometer-sized dispersions of calcium oxalate crystals formed in synthetic urine [78, 79]. 

S. Milardovic, Z. Grabaric, M. Tkalcec, and V. Rumenjak, Determination of oxalate in urine using an amperometric biosensor with oxalate oxidase immobilized on the surface of a chromium hexacyanoferrate-modified graphite electrode. J. AOAC Int. 83,1212—1217 (2000). 

A mixture consisting of oxalic acid, carbodiimide, fluorescer, and hydrogen peroxide is known to produce strong visible light [185], Albrecht et al. used this reaction to determine oxalate in urine [118] and serum [119]. 

Since the order of increasing CL intensity for alkyl amines reacted with Ru(bpy)32+ is tertiary amines > secondary amines > primary amines, pharmaceutical compounds bearing a tertiary amine function (e.g., antihistamine drugs [99], anticholinergic drugs [100], erythromycin [101], and its derivatives [102]) have been sensitively determined after HPLC separation (Table 3). The method was applied to the detection of d- and L-tryptophan (Trp) after separation by a ligand-exchange HPLC [103], The detection limits for d- and L-Trp were both 0.2 pmol per injection. Oxalate in urine and blood plasma samples has also been determined by a reversed-phase ion-pair HPLC (Fig. 18) [104], Direct addition of... 

Harvey, J. A., Zobitz, M. M., and Pak, C. Y. (1985). Calcium citrate Reduced propensity for the crystallization of calcium oxalate in urine resulting from induced hypercalduria of calcium supplementation. /. Clin. Endocrinol. Metab. 61,1223-1225. 

Table 8 lists some examples of gla proteins. They are assodated, in particular, with the control of blood coagulation and calcification. These will be discussed in later sections (62.1.3.8 and 62.1.3.9). The precipitation of calcium oxalate in urine is inhibited by gla proteins.263... 

Acidic polypeptides which inhibit the precipitation of calcium oxalate in urine contain gla residues. Other precipitating-inhibiting proteins found in saliva which are rich in tyrosine and proline residues have been discussed in Section 62.1.3.4.8. 

Zuborova M, Masar M, Kaniansky D, Johnck M, Stanislawski B. Determination of oxalate in urine by zone electrophoresis on a chip with conductivity detection. Electrophoresis 2002 23 774-781. 

Although a number of studies have suggested that high intakes of ascorbate lead to synthesis and excretion of oxalate (Section 13.6.5.1), this seems to be the result of nonenzymic formation of oxalate in urine samples after collechon. There is no known pathway for oxalate synthesis from ascorbate. 

Trace amounts of oxalate in urine are not usually significant as oxalates are present in many plant foods approximately 2 to 10 mg is excreted daily in the urine. Oxalate may also occur in urine as a result of poisoning widi ethylene glycol. 

Fig. 8-95. Separation of oxalate in urine. - Separator column IonPac AS4 eluent 0.0028 mol/L NaHC03 + 0.0022 mol/L Na2C03 flow rate 2 mL/min detection suppressed conductivity injection 50 pL sample (diluted 1 10).

The determination of oxalate in urine is required for diagnosis of renal calculus and hyperoxaluria. For enzymatic oxalate determination, oxalate decarboxylase (EC 4.1.1.2) has been employed in enzyme thermistors (Danielsson etal., 1981), enzyme reactors (Lindberg, 1983), and potentiometric enzyme electrodes (Kobos and Ramsey, 1980). 

It is evident from the equation that potentiometric CO2 electrodes as well as amperometric O2 or H2O2 electrodes can be used as transducers. Both potentiometric and amperometric sensors have been covered by a layer of oxalate oxidase protected by a dialysis membrane (Bradley and Rechnitz, 1986 Rahni et al.f 1986a). The sensors had a pH optimum at pH 3.5-4. Diffusion control was reached at 1 U oxalate oxidase per electrode. Oxalate determination was not affected by ascorbic acid or amino acids. The hydrogen peroxide-detecting sensor (Rahni et al., 1986a) has been used to measure oxalate in urine diluted 1 40. 

Other examples of amperometric enzyme electrodes based on the measurement of oxygen or hydrogen peroxide include electrodes for the measurement of galactose in blood (galactose oxidase,enzyme), oxalate in urine (oxalate oxidase), and cholesterol in blood serum (cholesterol oxidase). Ethanol is determined by reacting with a cofactor, nicotinamide adenine dinucleotide (NAD" ) in the presence of the enzyme alcohol dehydrogenase to produce the reduced form of NAD", NADH, which is electrochemically oxidized. Lactate in blood is similarly determined (lactate dehydrogenase enzyme). 

E. Gaetani, C. F. Laureri, M. Vitto, L. Borghi, G. F. Elia, and A. Novarini, Determination of Oxalate in Urine by Flow Injection Analysis. Clin. Chim. Acta, 156 (1986) 71. 

Figure 10.325 Separation of oxalate in urine. Separator column ionPac AS4-SC eluent 2.8mmol/L NaHC03+2.2mmol/L Na2C03,-flow rate 2 mUmin detection suppressed...

High oxalate concentrations in human urine and blood cause primary and secondary hyperoxaluria, chronic renal failure and formation of nephrocalcinosis. Therefore, precise and sensitive methods are required to detect oxalate in urine or blood, and in food for quality analysis. Measurement of oxalate in biological matrices requires separation methods due to the presence of other interfering species. Direct electrochemical detection methods have been proven to be simple and economical for the detection of... 

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