Control Chart Internal Quality Control of Laboratory Data

Control Chart Internal Quality Control of Laboratory Data (at NIFC) Tran Cao Son, Ph. D. National Institute for Food Control, Vietnam Ministry of Health APEC Wine Regulatory Forum | May 11 -12, 2017 Ha Noi, Viet Nam

National Institute for Food Control GOVERMENT MARD MOH VFA (Vietnam food Administration) MOIT NIFC 4 regional labs under MOH (Nha Trang, HCM, Tay Nguyen, Hanoi) 63 provincial centers NIFC - national reference food safety laboratory! APEC Wine Regulatory Forum | May 11 -12, 2017 Ha Noi, Viet Nam

Control chart ▪ Control chart was first developed by Walter Shewhart since 1930 ▪ Control chart: a record of the results of periodic inspections over time. ▪ Control chart can be classified into two types: X-chart and R-chart APEC Wine Regulatory Forum | May 11 -12, 2017 Ha Noi, Viet Nam 3

X-chart APEC Wine Regulatory Forum | May 11 -12, 2017 Ha Noi, Viet Nam 4

R-chart Range UCLx LCLx 0, 3 0, 25 Range 0, 2 0, 15 0, 1 0, 05 0 1 3 5 7 9 11 13 15 17 19 21 23 25 27 29 31 33 35 37 39 41 43 45 47 49 51 53 55 57 59 61 63 65 67 69 71 73 75 77 79 81 83 85 87 89 91 93 95 97 99 Events APEC Wine Regulatory Forum | May 11 -12, 2017 Ha Noi, Viet Nam 5

Data for control chart ▪ CRM, RM ▪ The assigned value is available with uncertainty: X ± U ▪ IQC, spiked ▪ The target value is average from 30 data ▪ Blank ▪ Control the signal of the blank = control the reagent quality ▪ Duplicate ▪ The bias of two duplicate, from 30 data APEC Wine Regulatory Forum | May 11 -12, 2017 Ha Noi, Viet Nam 6

X-chart ▪ IQC samples UWL = +2 s LWL = -2 s UAL = +3 s LAL = -3 s

R-chart ▪ Duplicates UWL = 2, 83 s LWL = 3, 67 s

Example – X-chart Aflatoxin B 1 120, 0% 115, 0% 110, 0% 105, 0% %R 100, 0% 95, 0% 90, 0% 85, 0% 80, 0% 75, 0% 70, 0% 0 5 10 15 20 25 30 35 Event APEC Wine Regulatory Forum | May 11 -12, 2017 Ha Noi, Viet Nam 9

Example – R-chart Methanol 25 20 mg/L 15 10 5 0 0 5 10 15 20 25 30 35 Event APEC Wine Regulatory Forum | May 11 -12, 2017 Ha Noi, Viet Nam 10

Out of control situations ▪ Out of control Ø 1 point beyond action limits Ø 2 out of 3 points in a row beyond warning limits ▪ Out of statistical control Ø 7 points in a row on the same side of the central line Ø 7 points in a row steadily increasing or decreasing Ø 10 out of 11 points in a row on the same side of the central line (Xchart) APEC Wine Regulatory Forum | May 11 -12, 2017 Ha Noi, Viet Nam 11

Choices of control chart ▪ The more frequent a specific analysis is done the more sense a control chart makes ▪ If the analyses are always done with the sample matrix, the sample preparation should be included. If the sample matrix varies, the control chart can be limited to the measurement only. ▪ Some methods include obligatory measurement of control samples or multiple measurements. ▪ In some cases the daily calibration gives values (slope and/or intercept), internal standard signals can be useful. APEC Wine Regulatory Forum | May 11 -12, 2017 Ha Noi, Viet Nam 12

References ▪ Internal quality control – Handbook for chemical laborarories ▪ NORDTEST TR 569 APEC Wine Regulatory Forum | May 11 -12, 2017 Ha Noi, Viet Nam 13

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