Sequential injection at valve mixing for determination of albumin-creatinine ratio in urine

Measurement of the albumin-creatinine ratio (ACR) as a medical index of renal failure is imperative to identify individuals at high risk of kidney disease. The present study is aimed to develop albumin and creatinine measurement method by sequential injection at valve mixing (SI-VM) for the determination of urinary ACR. The laboratory-made SI-VM system consists of a syringe pump, 8-port selection valve, RGB-LED detector, and holding coil. This system was controlled by a computer using a home-made software prepared by the Visual Basic program. The detection of albumin was based on dye-binding of methyl orange, while the Jaffe reaction was applied for the creatinine detection. Both albumin and creatinine were simultaneously and automatically measured using SI-VM, and the absorbance was recorded at 530 nm. Some parameters affected sensitivity, precision, and accuracy of the method, which includes pH of methyl orange, the volume of albumin, the concentration of NaOH, NaOH-picric acid ratio, and flow rate to detector were studied in detail. The proposed method was successfully applied to the determination of ACR in urine samples with satisfied results. Additionally, a rapid, sensitive, and accurate determination of ACR could be attributed to the SI-VM method.