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19.
2.
1.
8 Linearity range and lower limit of determination
Prepare five kinds of thiouracil derivatives with concentration of 1.
0ng/mL, 2.
0ng/mL, 5ng/mL, 10ng/mL and 20ng/mL matrix mixed standard solutions according to this method, and measure them under selected conditions.
The injection volume is 40uL, and the peak area is plotted against the concentration of each component in the standard solution.
The absolute amount of the five thiouracils shows a linear relationship in the range of 0.
04-0.
8ng, which meets the quantitative requirements.
The linear equation and The correction factors are shown in Table 19-7
.
Table 19-7 Five thiouracil linear equations and correction factors
It can be seen that, under the operating conditions specified by the method, when the concentration of the five thiouracils in the sample is 2ug/kg, the signal-to-noise ratio of the measured spectrum is greater than 10, which is higher than the minimum detection amount of the instrument
.
Therefore, the lower limit of the determination of the five thiouracils in this method is 2ug/kg
19.
2.
1.
9 Method recovery and precision
Use negative samples to do additive recovery and precision experiments.
After adding different concentration standards to the samples, perform extraction, derivatization, purification and determination according to this method.
The analysis results are shown in Table 19-8
.
It can be seen from Table 19-8 that the recovery rate of the two addition levels is between 86.
Table 19-8 Experimental data of recovery rate of five kinds of thiouracil addition (n=10)
Table 19-9 Experimental data of recovery rate of five kinds of thiouracil in different samples (n=10)
19.
2.
1.
10 Repeatability and reproducibility
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 19-10 The content range and repeatability and reproducibility equation of five kinds of thiouracil
