First of all let me define first what does a colorimeter do.
According to wikipedia, A Colorimeter is a device used in colorimetry. In scientific fields the word generally refers to the device that measures the absorbance of particular wavelengths of light by a specific solution. This device is most commonly used to determine the concentration of a known solute in a given solution by the application of the Beer-Lambert law, which states that the concentration of a solute is proportional to the absorbance.
The assigned topic to me is colorimetric method for Potassium determination, before I start explaining the method I will explain first what is Potassium. Potassium is an element (and an electrolyte) that's essential for the body's growth and maintenance. It's necessary to keep a normal water balance between the cells and body fluids. Potassium also plays an essential role in the response of nerves to stimulation and in the contraction of muscles. Cellular enzymes need potassium to work properly.
There are many methods or test wherein you can use the colorimeter and one of these test is the Potassium Determination. This colorimetric method for the direct determination of potassium in serum or plasma is based on the selective complexing of potassium by a specific macrocyclic polyether, with the subsequent formation of an ion-pair with a colored anion. The colored anion is extracted into an organic solvent, clarified by centrifugation, and then measured at 415 nm. The absorbance of the chromogen varies linearly with [K+] to at least 15 mmol/L. Results of this colorimetric method (y) correlate well with the results obtained by a flame- photometric method (y = 1.04x - 0.22, r = 0.97, n = 81), with CVs ranging from 2 to 4%. We observed no interferences from lipemia, added bilirubin, or various electrolytes. We also evaluated the use of this reagent in a new automated blood analyzer developed by Abbott, a two- dimensional centrifugal system (Clin Chem 31:1457-1463, 1985). Potassium determined with this system (y) correlated well with results by flame photometry: y = 1.02x + 0.02 (r = 0.94, n = 168). With this system one can use whole-blood specimens in measuring potassium.
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