Selection of analysis conditions for melengestrol acetate, chlorgestrol acetate and megestrol acetate residues in milk and milk powder

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7 Selection of analysis conditions

(1) Extraction method

When extracting the sample, it needs to be treated with alkali to dissolve the calcium salt of casein in the milk and reduce its adsorption capacity.
Add ethanol to dissolve the ethanol soluble matter in it, and add petroleum ether to make the separation clear
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After extraction with acetonitrile in the experiment , the temperature during centrifugation was controlled at -5°C, which could solidify the fat in the test solution and obtain a better centrifugal layering effect

(2) Purification method

To determine the optimal range of the elution, the milk was added 20μg / kg concentration melengestrol acetate , chloride, megestrol acetate and megestrol acetate after the standard solution, the method according to the present extraction process, activation of the solid-cyanopropyl After the phase extraction column, after passing the column, the eluent is collected in sections, the nitrogen is blown to dryness, and the volume is fixed with 1.
0 mL of methanol, and then the sample is injected to obtain the elution curve (Figure 8-10)
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It can be seen from Figure 8-10 that melengestrol acetate, chlorgestrol acetate and megestrol acetate can be eluted and washed with 3mL ethyl acetate + n-hexane solution (1+4, v/v).

Figure 8-10 Elution curve: elution volume 0～5mL n-hexane;

Wash volume 6～11mL ethyl acetate+n-hexane solution (1+19, v/v)

The elution volume is 12-16mL ethyl acetate + n-hexane solution (1+4, v/v)

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8 Method recovery and precision

Add melengestrol acetate, chlorgestrol acetate and megestrol acetate to the milk and milk powder samples, and take 10 independent samples for each addition level.
Process the samples according to the above steps.
The results of addition levels and recovery rates are shown in Table 8.
-16
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It can be seen from Table 8-16 that the average recovery rate of melengestrol acetate, chlorgestrol acetate and megestrol acetate added to the milk and milk powder samples at the four levels of addition is between 86.

Table 8-16 The recovery rate results of adding melengestrol acetate, chlorgestrol acetate and megestrol acetate to milk and milk powder samples (n=10)