Multiparametric flow system for the automated determination of sodium, potassium, calcium, and magnesium in large-volume parenteral solutions and concentrated hemodialysis solutions.

A multiparametric flow system based on multicommutation and binary sampling has been designed for the automated determination of sodium, potassium, calcium, and magnesium in large-volume parenteral solutions and hemodialysis concentrated solutions. The goal was to obtain a computer-controlled system capable of determining the four metals without extensive modifications. The system involved the use of five solenoid valves under software control, allowing the establishment of the appropriate flow conditions for each analyte, that is, sample size, dilution, reagent addition, and so forth. Detection was carried out by either flame atomic emission spectrometry (sodium, potassium) or flame atomic absorption spectrometry (calcium, magnesium). The influence of several operating parameters was studied. Validation was carried out by analyzing artificial samples. Figures of merit obtained include linearity, accuracy, precision, and sampling frequency. Linearity was satisfactory: sodium, r2>0.999 (0.5-3.5 g/L), potassium, r2>0.996 (50-150 mg/L), calcium, r2>0.999 (30-120 mg/L), and magnesium, r2>0.999 (20-40 mg/L). Precision (sr, %, n=5) was better than 2.1%, and accuracy (evaluated through recovery assays) was in the range of 99.8%-101.0% (sodium), 100.8-102.5% (potassium), 97.3%-101.3% (calcium), and 97.1%-99.8% (magnesium). Sampling frequencies (h-1) were 70 (sodium), 75 (potassium), 70 (calcium), and 58 (magnesium). According to the results obtained, the use of an automated multiparametric system based on multicommutation offers several advantages for the quality control of large-volume parenteral solutions and hemodialysis concentrated solutions.