Determination of inorganic sulfate in plasma with a centrifugal analyzer.

Turbidimetry of inorganic sulfate, after precipitation with barium sulfate, can be done simply in a Cobas Bio centrifugal analyzer. Polyethylene glycol is used as the precipitate-stabilizing agent. Reproducibility of precipitation is enhanced by the presence of BaSO4 particles, which function as seed nuclei. There is no interference by normal or above-normal concentrations of phosphate, heparin, bilirubin, hemoglobin, or erythrocyte contents, or by lipemia (triglyceride concentrations up to 6.5 mmol/L). Analytical recovery of added inorganic sulfate was found to be quantitative. Precision is similar to that for other methods for inorganic sulfate in plasma. This method is suitable for the rapid, routine analysis of plasma inorganic sulfate, and it is simple and less expensive to perform than alternative methods.