Selection of analytical conditions for determination of levamisole residues in milk and milk powder-selection of purification methods and optimization of conditions

(2) Purification method selection and condition optimization

The experiment comparatively studied the purification effect of liquid-liquid extraction method, silica solid phase extraction column, Envi-C ₁₈ column, strong cation exchange (SCX) column and GPC

1) Preliminary purification by liquid-liquid extraction

Levamisole is easily soluble in organic solvents, while levamisole hydrochloride is soluble in water

2) Optimization of the concentration of hydrochloric acid solution

The optimization experiment of the concentration of hydrochloric acid solution on the reverse extraction efficiency of levamisole was done .

3) Strong cation exchange solid phase extraction column purification

The experiment optimized the elution conditions and elution volume of the SPE cartridge

Figure 18-3 Levamisole elution curve

(3) Liquid chromatography-tandem mass spectrometry determination

1) Optimization of liquid chromatography analysis conditions

The BEH C ₁₈ column was selected as the separation column, and the column temperature was 30°C.

2) Optimization of mass spectrometry conditions

A syringe pump was used for direct injection, and a standard solution of levamisole was injected into the ion source of the tandem mass spectrometer at 10 μL/min

Figure 18-4 Levamisole standard solution-stage scan mass spectrum

Figure 18-5 Secondary scan mass spectrum of levamisole standard solution

3) Liquid chromatography-tandem mass spectrometry analysis

A multi-reaction monitoring mode ultra performance liquid chromatography-tandem mass spectrometer was used for analysis

Figure 18-6 UPLC-MS/MS TIC chart (left) and MRM mass spectrum of levamisole standard solution

Related Links: Selection of Analysis Conditions for Determination of Levamisole Residues in Milk and Milk Powder-Optimization of Extraction Conditions