For quantitative determination of calcium ion Ca²⁺ and evaluation of drug effects on calcium metabolism. Key Features: Sensitive and accurate. Use as little as 5 µL samples. Linear detection range 0.08 mg/dL (20 µM) to 20 mg/dL (5 mM) Ca²⁺ in 96-well plate assay. Simple and high-throughput. The procedure involves addition of a single working reagent and incubation for 3 min. Can be readily automated as a high-throughput assay for thousands of samples per day. Improved reagent stability and versatility. The optimized formulation has greatly enhanced reagent and signal stability. Cuvet or 96-well plate assay. Low interference in biological samples. No pretreatments are needed. Assays can be directly performed on raw biological samples i.e., in the presence of lipid, protein and minerals such as magnesium, iron and zinc. Method: OD612nm. Samples: Biological, food and environment. Species: All. Procedure: Assay takes 3 min. Kit size: 500 tests. Detection limit: 0.08 mg/dL (20 µM).