| Key Words | Frequency | Limits & Comments |
|---|---|---|
| Mass calibration/resolution | Before each analytical session | According to manufacturer's recommendations |
| Precision and sensitivity | Before each analytical session | Determined with a “Tune” solution to demonstrate sensitivity and stability. < 5% RSD for N= 5. |
| Calibration | Daily or when required | |
| Method detection limits (MDL) (according to 40CFR136, Appendix B) | Annually or after major hardware change | < 50% of contract required quantitation limits (CROQLs) before reporting results. All required calculations must be included, eg., interference correction equations, as these can have a substantial influence on MDLs. |
| Linear dynamic range (LDR) | Quarterly or after major Instrument hardware change | High standard + 10%) of the expected value, extrapolated trom the low standards. Calibration verified using second-source stan- dard, 90-110% |
| Initial calibration verification (ICV) | After each calibration | Calibration verified using second-source stan- dard, 90-110% |
| Continuing calibration verification (CCV) | After each calibration and every 10 samples | Periodic check on ongoing accuracy and drift using primary calibration standard, 90-110% |
| Initial calibration blank (ICB) | After each calibration | Read back of blank, < CROLs |
| Continuing calibration blank (CCB) | After each calibration and every 10 samples | Read back of blank, <CROLs |
| Contract required quantitation limit (CROL) check (CRI) | After each calibration and every 20 samples | The CRI solution is a check of the accuracy at CROL values. 70-130%, 50-150% for Co, Mn, and Zn |
| Interference check solution A (ICSA) | After each calibration | Contains potential interference elements. Checks freedom from interference elements at blank levels. ± 3 CRQL |
| Interference check solution AB (ICSAB) | After each calibration | Checks accuracy in an interference producing matrix by spiking with target elements into ICSA. 80-120% recovery |
| Matrix spike (MXS) | One per sample batch | Checks recoveries of target analytes spiked into an unknown predigested sample. 75—125% |
| Postdigestion spike (PDS) | One per sample batch | Checks recoveries of target analytes spiked into an unknown digested sample. 75-125% |
| Duplicates (DUP) | One per sample batch | Two aliquots of same sample, 80-120% (rela tive percentage difference [RPD]) |
| Laboratory control sample (LCS) | One per sample batch | Sample with known composition, processed through the same sample preparation procedure as the unknown samples. 80-120% |
| Internal standard | Five elements required | Response of any internal standard must not deviate by more than 60-125%. Dilute for high dissolved solid samples. |
| Serial dilution | One per sample batch | Unknown sample to check for matrix effects. Diluted concentration must be within the upper 75% of the calibrated or linear range. If analyte concentration > 50 times the MBL, a fivefold dilution will be + 1096 of original concentration. |
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