Table 7. Summary of QC requirements for turbidity analysis by Hach meter QC Sample or Activity Minimum Frequency Acceptance Criteria Corrective Action Four (4) prepared samples Criteria for duplicate precision Capability demonstration analyzed prior to any Repeat until acceptable RPD < 25% customer sample analyses 90-110% R (measured value of Investigate problem. Correct 4-Point calibration plus primary standards when analyzed as At least quarterly any obvious problems. Repeat deionized water blank samples within 10% of expected calibration until acceptable. values) Investigate problem. Correct Assign values to Measurement after acceptable any obvious problems permanent transfer At least quarterly point calibration and values within including replacing transfer standards using formazin 10% of previous established values standards if necessary. Repeat primary standards until acceptable. Investigate problem. Correct any obvious problems. If GELEX Secondary Turbidity Standards Immediately prior to and necessary reassignment of Daily calibration check should read within 10% of assigned after sample analysis GELEX values and reanalyze values samples. Repeat calibration check until acceptable. Clean analytical system and repeat MB analysis. Identify Method blank Daily prior to sample analysis <1.0 NTU (i.e., < RL) and eliminate source of contamination. Direct sample reading within If reading below range report Sample analysis For all sample analyses acceptable measurement range (i.e., result as < RL. If result above 1.00 NTU to 4000 NTU) range dilute sample. Investigate problem. If system precision is in control, qualify Sample duplicate One (1) per preparation batch RPD < 25% results. If system precision is out of control, reanalyze entire batch. Samples and frequency 75-125% R Investigate all unacceptable Internal PE sample determined by Lab QA Officer RPD < 25% results. Samples and frequency Investigate all unacceptable Blind PE sample determined by accrediting Determined by PE provider results. agencies and projects LCS = laboratory control sample QC = quality control MB = method blank %R = percent recovery MDL = method detection limit RL = reporting limit MS = matrix spike RPD = relative percent difference PE = performance evaluation
Table 7. Summary of QC requirements for turbidity analysis by Hach meter QC Sample or Activity Minimum Frequency Acceptance Criteria Corrective Action Capability demonstration Four (4) prepared samples analyzed prior to any customer sample analyses Criteria for duplicate precision RPD < 25% Repeat until acceptable 4-Point calibration plus deionized water blank At least quarterly 90-110% R (measured value of primary standards when analyzed as samples within 10% of expected values) Investigate problem. Correct any obvious problems. Repeat calibration until acceptable. Assign values to permanent transfer standards using formazin primary standards At least quarterly Measurement after acceptable calibration and values within 10% of previous established values Investigate problem. Correct any obvious problems including replacing transfer standards if necessary. Repeat until acceptable. Daily calibration check Immediately prior to and after sample analysis GELEX Secondary Turbidity Standards should read within 10% of assigned values Investigate problem. Correct any obvious problems. If necessary reassignment of GELEX values and reanalyze samples. Repeat calibration check until acceptable. Method blank Daily prior to sample analysis <1.0 NTU (i.e., < RL) Clean analytical system and repeat MB analysis. Identify and eliminate source of contamination. Sample analysis For all sample analyses Direct sample reading within acceptable measurement range (i.e., 1.00 NTU to 4000 NTU) If reading below range report result as < RL. If result above range dilute sample. Sample duplicate One (1) per preparation batch RPD < 25% Investigate problem. If system precision is in control, qualify results. If system precision is out of control, reanalyze entire batch. Internal PE sample Samples and frequency determined by Lab QA Officer 75-125% R RPD < 25% Investigate all unacceptable results. Blind PE sample Samples and frequency determined by accrediting agencies and projects Determined by PE provider Investigate all unacceptable results. LCS = laboratory control sample QC = quality control MB = method blank %R = percent recovery MDL = method detection limit RL = reporting limit MS = matrix spike RPD = relative percent difference PE = performance evaluation point
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