Determination of 9 Penicillin Residues in Milk and Milk Powder-Selection of Analysis Conditions

5.
2.
2.
7 Selection of analysis conditions

(1) Selection of precipitant

In the study of this method, according to the characteristics of high protein content in milk and milk powder, we must first select a suitable precipitant to remove the protein, so as to reduce or remove the interference to the determination
.
Respectively use acetonitrile , trichloroacetic acid , sodium urate, composite precipitation agent 1: Carrez I (0.

(2) Selection of extract

Use sodium dihydrogen phosphate solution, different volume ratios of acetonitrile to sodium dihydrogen phosphate solution (0.
05mol/L, pH8.
5) (5+2, v/v), acetonitrile, and different volume ratios of acetonitrile-water as Extract the liquid and do the recovery test of the addition
.
Experiments have found that when the sodium dihydrogen phosphate buffer is used as the extraction solution, the protein cannot be precipitated, and it is more difficult to pass the solid phase extraction column

(3) Selection of solid phase extraction column

In the experiment of the method, has used a C BUNDELUT _{18 is} solid phase extraction column (3cm ^.
3 and 6cm ^.
3 ), OasisHLB SPE column (3cm ^.
3 and 6cm ^.
3 )
.
The results showed that the retention of amoxicillin by the two specifications of the C ₁₈ column was incomplete.

Figure 5-59 Elution curve of penicillins

(4) Selection of liquid chromatography analysis column

In the experiment, 0.