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8 Linearity range and lower limit of determination
According to the sensitivity of each penicillin drug, a series of standard working solutions are prepared with water, and a series of matrix standard working solutions are prepared with the blank solutions of milk and milk powder samples.
The determination is carried out under the selected chromatographic conditions and mass spectrometry conditions.
The injection volume is 15μL.
, Use the ratio of the peak area of the analyte to the peak area of the selected internal standard to plot the concentration of the measured component in the matrix standard working solution.
The linear range, linear equation and linear correlation coefficient are shown in Table 5-16
.
From the linear equations of different matrices, it can be known that the matrix has a certain interference to the determination of the analyte.
Table 5-16 Linear equations and correction factors of 9 penicillins
Under the operating conditions of this method, when the added level of 9 penicillins was in the range of 1 to 320 μg/kg, the respective measured response values were within the linear range of the instrument
.
The concentration of ampicillin and nafcillin in milk is 1μg/kg, the concentration of amoxicillin, piperacillin , penicillin G, penicillin V, and cloxacillin is 2μg/kg, and the concentration of oxacillin and dicloxacillin is 4ug.
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9 Method recovery and precision
This method uses penicillin-free milk and milk powder to add a mixed standard solution for recovery and precision tests.
Four levels are added, and each level is measured 10 times.
The average recovery and coefficient of variation are shown in Table 5-17
.
It can be seen from Table 5-17 that the recovery rate of the milk sample in this method is between 62.
Table 5-17 Recovery rate and precision data of 9 penicillins in milk and milk powder (n=10)
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Under repeatability test conditions, the absolute difference between the two independent test results obtained does not exceed the repeatability limit (r).
If the difference exceeds the repeatability limit (r), the test results should be discarded and the two individual tests should be completed again.
Determination
.
Under the reproducibility test conditions, the absolute difference between the two independent test results obtained does not exceed the reproducibility limit (R)
Table 5-18 Concentrations and repeatability and reproducibility equations of 9 penicillins in milk
Table 5-19 Concentrations and repeatability and reproducibility equations of 9 penicillins in milk powder
Related Links: Determination of 9 Penicillin Residues in Milk and Milk Powder-Selection of Analysis Conditions