Table 14. Summary of QC requirements for Oakton pH meter Minimum QC Activity Acceptance Criteria Corrective Action Frequency Standardize using +/- 0.1 pH units two pH buffers that Before each of actual buffer value* are within 3 pH units meter use of each other Recalibrate the meter with new buffer solution. If this the doesn’t solve problem, the electrode should be Measure a pH buffer cleaned, repaired, or replaced. bracketed by the two Before each +/- 0.1 pH units buffers used for meter use of actual buffer value* standardization as a post-calibration check Periodically measure pH of standard buffer Recalibrate the meter and reanalyze Every 10 +/- 0.1 pH units of actual solution when the samples measured after the last samples buffer value* measuring pH of acceptable check measurement. samples Check ATC thermometer against Quarterly (4 +/- 0.05oC of a NIST-traceable Recalibrate the ATC thermometer to a NIST-traceable times/year) thermometer NIST-traceable thermometer thermometer *NOTE: Actual pH standard values are temperature dependent. See 5.6.3. in SOP 422.
Table 14. Summary of QC requirements for Oakton pH meter QC Activity Minimum Frequency Acceptance Criteria Corrective Action Standardize using two pH buffers that are within 3 pH units of each other Before each meter use +/- 0.1 pH units of actual buffer value* Recalibrate the meter with new buffer solution. If this doesn’t solve the problem, the electrode should be cleaned, repaired, or replaced. Measure a pH buffer bracketed by the two buffers used for standardization as a post-calibration check Before each meter use +/- 0.1 pH units of actual buffer value* Periodically measure pH of standard buffer solution when measuring pH of samples Every 10 samples +/- 0.1 pH units of actual buffer value* Recalibrate the meter and reanalyze the samples measured after the last acceptable check measurement. Check ATC thermometer against NIST-traceable thermometer Quarterly (4 times/year) +/- 0.05oC of a NIST-traceable thermometer Recalibrate the ATC thermometer to a NIST-traceable thermometer *NOTE: Actual pH standard values are temperature dependent. See 5.6.3. in SOP 422.
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