Working calibration standards are prepared each day from dilution of a 1000 ppm mixed stock solution. A four point calibration is performed and an independent check QC sample is analyzed every 10 samples. Because of the long-term instability of nitrite in aqueous solution this ion is not included in the routine analysis. However, if required, nitrite standards can be made up on the day of analysis and this anion subsequently quantified for an additional cost. The unit automates sampling, reagent addition, dilution, absorbance measurements and data logging to file, and is capable of simultaneously determining up to three analytes in a given sample set.
Detection limits are typically sub-ppm in solution.
For P and B, ICP may be used with slightly better detection. CS5A column and absorbance detection following post column derivitization.