Determination of 9 kinds of penicillin residues in milk and milk powder

5.
2.
2.
6 Determination

(1) Liquid chromatography conditions

Chromatographic column: phenyl column, 5μm, 150mm×2.
1mm (inner diameter) or equivalent; chromatographic column temperature: 30℃; injection volume: 15μL; mobile phase gradient and flow rate are shown in Table 5-14
.

Table 5-14 Liquid chromatography gradient elution conditions

(2) Mass spectrometry conditions

Ionization mode: electrospray positive ion mode (ESI); mass spectrometry scan mode: multiple reaction monitoring (MRM); sheath gas pressure: 30unit; auxiliary gas pressure: 8unit; positive ion mode electrospray voltage (IS): 4000V; capillary temperature : 320℃; Induced dissociation voltage in the source: 10V; Q1 is 0.
4, Q3 is 0.
7; collision gas: high purity argon; collision gas pressure: 1.
5mTorr; other mass spectrometer parameters are shown in Table 5-15
.

Table 5-15 The retention time, acquisition window, monitoring ion pair and fragmentation energy of the analyte

(3) Qualitative determination

Choose one parent ion and two or more product ions for each tested component.
Under the same experimental conditions, the retention time of the substance to be tested in the sample is within ±2.
5% of the corresponding retention time in the mixed matrix standard calibration solution.
In addition, the relative abundance of the qualifier ions of each component in the sample spectrum is compared with the relative abundance of the corresponding qualifier ions in the mixed matrix standard calibration solution spectrum with close concentrations, and 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

Under the best working conditions of the instrument, sample the mixed matrix standard calibration solution.
Use the peak area as the ordinate and the concentration of the mixed matrix calibration solution as the abscissa to draw a standard working curve.
Use the standard working curve to quantify the sample.
The response value of the measured object should be within the linear range measured by the instrument
.

Figure 5-49 Multiple Reaction Monitoring (MRM) Chromatograms of Penicillin Standard Substances

Draw an appropriate amount of mixed standard working solution and dilute it with a blank matrix solution into a standard calibration solution of the required concentration
.

Related Links: Determination of 9 Penicillin Residues in Milk and Milk Powder-Liquid Chromatography-Tandem Mass Spectrometry