According to the US EPA criteria, inter-element interference corrections are achieved by using Inter Element Correction (IEC) factors. These are calculated by observing the effect of known amounts of interferents on the analyte wavelengths. A table of IEC factors is generated and applied to the sample results during the analysis. In ILM04.0/05.0, two solutions are analysed - Interference Check Samples A (Ref: CLPP-ICS-A-125ML)and AB (Ref: CLPP-ICS-B-125ML), where A contains 4 interferents only (Al, Ca, Fe and Mg) and AB contains the interferents plus 16 analytes. In the ICSA, the analytes must be within ± 2xCRDL (for elements with CRDLs ³10 ug/L) and in ICSAB the analytes should be recovered within ± 20%. If the recoveries are outside these limits the “Recalibrate and Repeat with Samples” action should be conducted. For elements with CRDLs > 10 ug/L the results of the ICSA are simply reported with no test applied. The ICSA and ICSAB tests are applied at the beginning and end of the run and at a frequency of not greater than 20 samples. In Method 200.7, 17 single element, Spectral Interference Check (SIC) solutions are prepared. Concentration results at analyte wavelengths are then compared to the IDL or 3 sigma control limits of the calibration blank.