Calcium, the most abundant mineral in the human body, plays a pivotal role as a crucial intracellular element, regulating many cellular processes. Calcium is found in either the free ion form or in bound complexes, such as the calcium phosphate and calcium carbonate complexes constituting bone tissue. Calcium signaling governs various physiological processes, including muscle contraction, cell adhesion, release of hormones/neurotransmitters, glycogen metabolism, cell proliferation/differentiation, blood clotting, nerve or sympathetic impulse transmission, and structural support of the skeleton. Disruptions in the integrity of cell-specific calcium signaling systems are associated with certain human diseases.

RayBio® Calcium Colorimetric Assay Kit provides a simple, reproducible, and sensitive tool for measuring calcium concentration in plasma, serum, cell lysates, urine and other biological liquid samples. In this assay, Calcium reacts with Arsenazo in a slightly alkaline medium forming a purple-colored complex with absorbance at 650 nm. The color intensity is proportional to the calcium concentration in the sample.

• Microplate reader capable of measuring absorbance at 650 nm
• Precision pipettes to deliver 2 µl to 1 ml volumes
• Multi-channel pipettes to deliver 20 μl to 200 μl volumes
• Tubes to prepare sample dilutions

Each Calcium standard and sample should be assayed in duplicate or triplicate. A freshly prepared standard curve should be used each time the assay is performed.

1. Add 10 µL of the diluted Calcium standards or samples to the 96-well microtiter plate.
2. Initiate the reaction by adding 150 µL of Calcium Assay Solution to each well.
3. Cover with the plate cover. Carefully shake the plate for a few seconds to mix.
4. Incubate the plate for 5 minutes at room temperature.
5. Measure the absorbance at 650nm using a plate reader.