A direct ion-selective electrode analyzer (NOVA 10)evaluated for serum Li determination

A ion-selective electrode analyzers for measuring lithium (Li/ISE) in serum became available in early 1987. Since that time, several ionophores for determination of lithium in serum have been described. NOVA 10 (NOVA Biomedical, Waltham, MA) is a direct, ion-selective electrode analyzer for measuring sodium, potassium, chloride, total calcium and lithium in serum, plasma, CSF and urine. The aim was to evaluate the analytical performance of the instrument according to the ECCLS guidelines (imprecision, accuracy, carryover, linearity and comparison study for lithium (Li) in serum. Venous blood from patients receiving lithium therapy was collected in to vacutainer tubes (Becton Dickinson Co, Rutherford, UK) with no anticoagulant, and allowed to clot. Serum was separated by centrifugation. Control material used in the study included Stat Profile Control 1-3, Precinorm U, Precipath U and Serodos. Randomly chosen patient sera were used in comparison study for lithium on a flame photometer PHF-104 (Hycel, France). Intra-assay CV was 1.08%. While interassay CV ranged from 1.05% to 1.15%. Carryover was negligible (K