The BioThema liquid-stable ATP Standard
At BioThema the concentration of ATP stock solutions is determined with an enzymatic method using hexokinase and a glucose standard monitoring the end-point ATP consumption at the addition of a known amount of glucose with the Biothema ATP Reagent SL. Using this method the concentration of one stock solution was found to be 2.052±0.003 mmol/L. At SP Technical Research Institute of Sweden the concentration of the same solution was determined with ICP-OES and HPLC-ICP-OES methods to be 2.10±0.10 mmol/L. The two values agree within limits of error. As the BioThema value is more accurate and has been repeated several times with essentially the same result we have chosen this value for this reference ATP stock solution. When preparing new stock solutions we perform the assay with the hexokinase method, but we also compare the light emission (without hexokinase and glucose) with ATP Reagent SL between the new solution and the 2.052 mmol/L solution. Furthermore we run an HPLC method to confirm that there are only traces of other nucleotides.
BioThema liquid-stable ATP Standards are available in different concentrations. They are all prepared from a known stock solution by weighing out the ATP solution and the buffer on a calibrated analytical balance. The light emission with ATP Reagent SL of newly prepared ATP Standard is compared with that of an old ATP Standard. Certificates of analysis are available on all BioThema products. The liquid-stable ATP Standards are abolutely stable both at +4 and -20 degrees Celsius for more than 2 years. They can be frozen and thawed for more than 10 times with no effect on the ATP concentration. The standards should be kept in closed vials to avoid increasing the concentration by evaporation of water.