Risk Warning of Veterinary Drug Residues in Raw Milk Based on Shewhart Control Chart
The aim of this study was to develop a dynamic risk warning method of veterinary drug residues in raw milk. Risk warning methods of veterinary drug concentration above MRLs (C1 risk warning), abnormal detection rates (J-Pn risk warning) and average-standard deviation (Χ-δ risk warning) were developed based on theory of Shewhart Control Chart. Flumequine and danofloxacin residues data of raw milk from a large dairy company were collected. Fifty raw milk samples were detected in each week and total of 1000 continuous data of 20 weeks were analyzed. The data were divided into 20 groups according to time series. C1 risk warning was not triggered, because none of samples exceeded MRLs. J-Pn risk warning was used for danofloxacin, because most of samples were not detected. Central line (CL) was calculated with the value of 5.95 and upper control limit (UCL) was 12.82. Control charts indicated that numbers of samples detected in each week were stable and all less than 12.82, so J-Pn risk warning was not necessary in 1-20 weeks. For flumequine, Χ-δ risk warning was used, because most of samples were detected. The value of CL was 1.5 and UCL was 2.82. Results analyzed by control charts showed average of flumequine in each week were stable and less than 2.82, so Χ-δ risk warning was not necessary in 1-20 weeks. In this study, abnormality of detection rate and average-standard deviation was also assumed and analyzed.
Keywords: risk warning; veterinary drug residues; Shewhart Control Chart