Linear range and lower limit of determination of nitrofuran metabolite residues in food of animal origin

7.
2.
1.
8 Linearity range and lower limit of determination

(1) Pork, beef, chicken, pork liver, fish, shrimp, crab and shellfish samples

Prepare four nitrofuran metabolite derivatives with concentrations of 0.
5 ng/mL, 1.
0 ng/mL, 5.
0 ng/mL, 10 ng/mL, 20 ng/mL and 50 ng/mL matrix mixed standard solutions according to the method.
Measured under the conditions of, the injection volume is 40uL, and the peak area is used to plot the concentration of each component in the standard solution.
The four nitrofuran metabolites show a linear relationship in the range of 0.
5-50.
0ng/mL, which is consistent with For quantitative requirements, the linear range, linear equation and correction factor are shown in Table 7-9
.

Table 7-9 Linear equations and correction factors of four nitrofuran metabolites

Under the operating conditions specified in the method, when the concentration of the four nitrofuran metabolites in the sample is 0.
5μg/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 determination in samples of pork, beef, chicken, pork liver, fish, shrimp, crab, and shellfish is determined to be 0.

(2) Milk and milk powder samples

Prepare four nitrofuran metabolite derivatives with concentrations of 1.
0ng/mL, 2.
0ng/mL, 5.
0ng/mL, 10ng/mL, 20ng/mL and 100ng/mL matrix mixed standard solutions according to the method.
Measured under the conditions of, the injection volume was 40μL, and the peak area was used to plot the concentration of each component in the standard solution.
The four nitrofuran metabolites showed a linear relationship in the range of 1.
0～100.
0ng/mL, which was consistent with For quantitative requirements, the linear range, linear equation and correction factor are shown in Table 7-10
.

Table 7-10 Linear equations and correction factors of four nitrofuran metabolites

Under the operating conditions specified in the method, when the added concentrations of the four nitrofuran metabolites in milk and milk powder are 0.
2μg/kg and 1.
6μg/kg, respectively, the signal-to-noise ratio of the measured spectrum is greater than 10, which is higher than the instrument's minimum Detection amount
.
Therefore, the determination limits of the four nitrofuran metabolites in milk and milk powder samples are 0.

(3) Honey samples

The concentrations of 2-NBA-AOZ and 2-NBA-AMOZ were prepared according to the method at 0.
5ng/mL, 1.
0ng/mL, 5.
0ng/mL, 10ng/mL, 20ng/mL and 50ng/mL; 2-NBA-SEM and 2-NBA-AHD concentration of 1.
0ng/mL, 5.
0ng/mL, 10ng/mL, 20ng/mL, 50ng/mL and 100ng/mL of honey blank sample matrix mixed standard solution, measured under selected conditions , The injection volume is 40μL, and the peak area is plotted against the concentration of each component in the standard solution.
The absolute amount of 2-NBA-AOZ and 2-NBA-AMOZ is linear in the range of 0.
02～2.
0ng; 2- The absolute amount of NBA-SEM and 2-NBA-AHD shows a linear relationship in the range of 0.
04～4.
0ng, which meets the quantitative requirements.
The linear equations and correction factors are shown in Table 7-11
.

Table 7-11 Linear equations and correction factors of four nitrofuran metabolites

Under the operating conditions specified in the method, when AOZ and AMOZ are added at a level of 0.
2～4μg/kg: when SEM and AHD are at a level of 0.
5～10μg/kg, the response values ​​are all within the linear range of the instrument
.
At the same time, the additive concentration of AOZ and AMOZ in the sample is 0.