title: A manual spectrophotometric method for the measurement of serum sodium and potassium by enzyme activation.
abstract: Manual procedures suitable for use on standard benchtop spectrophotometers have been developed for the enzymatic determination of Na+ and K+ in serum. Both assays require only minimal modification of reagents already available for BM/Hitachi analyzers and are performed in an endpoint mode, allowing up to 20 assays per run. The addition of a stop reagent is required--dipotassium EDTA for the Na+ assay and sodium dodecyl sulphate for the K+ assay. The most important criterion for achieving good assay performance is the precise pipetting of sample and reagent. Within-run imprecision is < 1% for Na+ and K+, and between-run imprecision < 1.5%, for both assays at all but the lowest concentrations of K+. Enzymatic electrolyte results compare well with flame photometry, however the assays are more prone to interference by very high concentrations of bilirubin or triacylglycerols than those performed on automated, dual-wavelength kinetic analyzers. It is possible to correct for most interferences by inclusion of appropriate sample and reagent blanks.
authors.affiliation: Department of Biochemistry and Chemical Pathology, Flinders Medical Centre, Bedford Park, Australia.
authors.forename: R D
authors.initials: RD
authors.lastname: Mazzachi
authors.forename: B C
authors.initials: BC
authors.lastname: Mazzachi
authors.forename: M N
authors.initials: MN
authors.lastname: Berry
mesh_terms: D000042:Absorption; D001663:Bilirubin / Q000378:metabolism; D002138:Calibration; D004347:Drug Interactions; D004492:Edetic Acid / Q000737:chemistry; D004789:Enzyme Activation; D006801:Humans; D016014:Linear Models; D008433:Mathematics; D011188:Potassium / Q000097:blood*; D012015:Reference Standards; D015203:Reproducibility of Results; D012964:Sodium / Q000097:blood*; D012967:Sodium Dodecyl Sulfate / Q000737:chemistry; D013056:Spectrophotometry, Ultraviolet; D014280:Triglycerides / Q000378:metabolism
chemical_list: D014280:Triglycerides; D012967:Sodium Dodecyl Sulfate; D004492:Edetic Acid; D012964:Sodium; D001663:Bilirubin; D011188:Potassium