Determination of Nitrofuran Metabolite Residues in Food of Animal Origin

7.
2.
1.
6 Determination

(1) Liquid chromatography conditions

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

Chromatographic column: Atlantis-C ₁₈ , 3.
5μm, 150mm×2.
1mm (inner diameter) or equivalent; column temperature: 35℃; injection volume: 40μL
.

Table 7-2 Liquid chromatography gradient elution conditions

2) Milk or milk powder sample

Chromatographic column: Atlantis C ₁₈ , 3.
5um, 150mm×2.
1mm (inner diameter) or equivalent; column temperature: 35°C; injection volume: 40μL
.

Table 7-3 Liquid chromatography gradient elution conditions

3) Honey sample

Chromatographic column: ZORBAXSB-C ₁₈ , 3.
5um , 150mm×2.
1mm (inner diameter) or equivalent; column temperature: 30℃; injection volume: 40μL
.

Table 7-4 Liquid chromatography gradient elution conditions

(2) Mass spectrometry conditions

Ion source: Electrospray ion source (ESI); Scan method: positive ion scan; Detection method: Multiple reaction monitoring (MRM); Electrospray voltage (IS): 5000V; Auxiliary gas (AUX) flow rate: 7L/min; Auxiliary gas Temperature (TEM): 480℃; Focusing voltage (FP): 150V; Collision cell outlet voltage (CXP): 11V; Declustering voltage (DP): 45V; Qualitative ions for four nitrofuran metabolites and internal standard derivatives See Table 7-5 for the mass spectrometry parameters of pair and quantitative ion pairs, acquisition time and collision energy
.

Table 7-5 Mass spectrometric parameters of four nitrofuran metabolites and internal standard derivatives

(3) Qualitative determination

Choose one parent ion and two or more product ions for each tested component.
Under the same experimental conditions, the ratio of the retention time of the test substance and the internal standard substance in the sample, that is, the relative retention time, is calibrated with the mixed matrix standard The deviation of the corresponding relative retention time in the solution is within ±2.
5%; and the relative abundance of the qualifier ion of each component in the sample spectrum is close to the relative abundance of the corresponding qualifier ion in the mixed matrix standard calibration solution spectrum.
By comparison, if the deviation does not exceed the range specified in Table 1-5, it can be determined that there is a corresponding analyte in the sample
.

(4) Quantitative determination

Internal standard method quantification: Under the best working conditions of the instrument, the mixed matrix standard calibration solution of four nitrofuran metabolites is injected for determination.
The ratio of the peak area to the peak area of ​​the isotope internal standard is the ordinate, draw a standard working curve, use the standard working curve to quantify the sample to be tested through the internal standard quantification program in the instrument software, and the response value of the analyte in the sample solution is all It should be within the linear range measured by the instrument
.

Figure 7-3 Multiple reaction monitoring (MRM) chromatograms of four nitrofuran metabolites and internal standard derivatives