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7 Selection of analysis conditions
(1) Selection of extraction and purification conditions
1) The choice of protein precipitant in the sample
Experiments have shown that the protein in the sample has a greater impact on the mass spectrometry determination.
Effectively removing the protein in the measurement solution is the key to sample extraction and purification
.
The method of the present experiment with trichloroacetic acid , zinc sulfate and potassium ferrocyanide mixed solution of sodium tungstate and three methods of removing protein, tests showed, 30mL 5% phosphoric acid solution was extracted, trichloroacetic deproteinized better
Table 3-5 The influence of the addition amount of different trichloroacetic acid solutions (50%, mass fraction) on the results
It can be seen from Table 3-5 that when the sample is extracted with 30mL 5% phosphoric acid solution and added with 3mL trichloroacetic acid solution (50%, mass fraction), the deproteinization effect is the best, and the three antibiotics have the highest response signals
.
2) Selection of solid phase extraction column
This method tested Oasis HLB (60 mg, 3 mL), BAKERBOND SPE TM (500 mg, 3 mL), SUPELCLEANT MLC-SCX (500 mg, 3 mL), carboxyl and BAKERBOND SPE TM C18 (500 mg, 3 mL) single and double columns and The purification effect and recovery rate of different combinations
.
Experiments show that the BAKERBOND SPE TM benzene sulfonic acid type cation exchange column and the carboxylic acid type (500 mg, 3 mL) double column purification effect and recovery rate are the highest
3) Selection of elution conditions for benzene sulfonic acid solid phase extraction column
The analyte is extracted from the sample and passes through a benzene sulfonic acid solid phase extraction column, and the target substance is adsorbed on the extraction column
.
After washing the extraction column with 5 mL phosphoric acid solution and 10 mL water, most of the impurities were removed
Use negative milk powder samples, add the same amount of standard, use the same method, use different pH and concentration of phosphate solutions for conditional experiments, the experimental data are shown in Table 3-6
.
Table 3-6 Experimental results of optimal elution conditions of buffer solution
It can be seen from Table 3-6 that when the concentration of the phosphate buffer solution is 0.
2mol/L and the pH is 9.
Table 3-7 Experimental results of optimal elution conditions of buffer solution
It can be seen from Table 3-7 that when the concentration of the phosphate buffer solution is 0.
2mol/L and the pH is 8.
Table 3-8 Experimental results of optimal elution conditions for buffer solution
It can be seen from Table 3-8 that when the concentration of the phosphate buffer solution is 0.
