The range listed above is based on a pathlength of 1.8 cm. Method Cupric ions form a purple complex with bicinchoninic acid around pH 6-7, in proportion to the concentration of copper in the sample. Samples should be analyzed as soon as possible after collection. However, a correction must be made to bring the reaction in the optimum pH range. Interferences High concentrations of oxidizing agents, calcium and magnesium interfere.
Silver can also interfere.
A calibration curve must be generated using this LaMotte reagent system before testing. See Creating a Calibration Curve instructions for directions. Procedure Set colorimeter or spectrophotometer to a wavelength of 560 nm. Cap and shake vigorously until tablet dissolves. Solution will turn purple if copper is present.