Automated determination of urinary Na+, K+, chloride, inorganic phosphate, urea, and creatinine without sample dilution, with the "RA-XT".

We describe how concentrations of chloride, urea, inorganic phosphate, and creatinine in urine can be measured directly, without manual sample dilution, in a discrete analyzer (the Technicon "RA-XT"). These methods were accurate for concentrations of chloride up to 280 mmol/L, urea up to 500 mmol/L, inorganic phosphate up to 50 mmol/L, and creatinine up to 30 mmol/L. CVs are less than 3% nd results correlate well with those obtained by continuous-flow analysis (SMA-II). All these reagents are stable at room temperature for three weeks. Analyses are easy to perform and infrequent calibration is required.