The implementation of the Food Safety Law has strengthened the testing of product quality by food companies, especially the quantitative analysis of melamine in foods such as dairy products, dairy products and livestock and poultry feeds, with stricter requirements.
Quantitative analysis of melamine in foods such as dairy products, dairy products, and livestock and poultry feeds can be performed by high performance liquid chromatography, LC-MS/MS or GC-MS. Regardless of which method is used, sample pretreatment is the first and most critical step. Sample pretreatment guarantees the effective separation of melamine and products, and does not allow other impurities to interfere with the true effect of the test, in order to obtain true and reliable content data.
Melamine is first extracted from food and livestock feeds with organic solvents. The type of food is different and the extraction method is slightly different. After extraction with organic solvent, a solid phase extraction column must be applied. When using high performance liquid chromatography for quantitative analysis of melamine, the function of the solid phase extraction column is to clean impurities and concentrate the recovery of melamine. So a silica matrix C8+SCX or SCX solid phase extraction column is preferred. On the other hand, in the quantitative analysis of melamine by LC-MS/MS or GC-MS, it is the most important task of the SPE to clean impurities and eliminate the media effect. PSA or SCX solid phase extraction columns are preferred.
The simplest LC-MS/MS analysis method is:
After extracting foods such as dairy products, dairy products and livestock feeds with an organic solvent such as acetonitrile, 0.5 mL of the extract is passed through a PSA (500 mg/3 cc) solid phase extraction column (lead with 5 mL of acetonitrile first; the eluent is thrown away) Rinse with 2 ml of acetonitrile, collect all the effluent, and dilute to volume with 1% formic acid. Samples were analyzed directly by LC-MS/MS.
The LC-MS/MS MRM chart for melamine is as follows:
LC-MS/MS test conditions:
Column: InnovationTM WCX 3um 15cm x 2.1mm
Mobile phase A: acetonitrile (0.1% formic acid); mobile phase B: water (0.1% formic acid); flow rate: 300 uL/min injection volume: 10 uL;
Gradient: 55% A + 45% B (equal gradient)
Instrument: Perkin-Elmer 200 series HPLC
ABI API 4000 tandem mass spectrometer
Leap Technologies Autosampler
Test sample: 100 ng/mL melamine MRM conversion (ESI positive ion mode): 127.2 → 85.20 (DP: 42; CE: 28; CXP: 5)
127.2 → 68.10 (DP: 42; CE: 42; CXP: 11)
127.2 → 110.30 (DP: 42; CE: 26; CXP: 8)
The retention of melamine on the InnovationTM PFPP LC-MS/MS analytical column is hydrophilic hydrophilic chromatography. Acetonitrile is a weak solvent and water is a strong solvent. If you need to extend the retention time, simply increase the ratio of acetonitrile. Melamine has a good peak shape on the InnovationTM PFPP LC-MS/MS analytical column with no residual effect and high sensitivity to mass spectrometry. Each extraction sample was tested for 4 minutes (5 cm long PFPP LC-MS/MS analytical column for 1 minute without peak interference. After using the InnovationTM PSA or SCX solid phase extraction column to completely eliminate the Matrix effect in quantitative analysis, Using the same mobile phase standard calibration curve for the detection of melamine in different brands, different origins, different components of dairy and dairy products, accurate, fast, cheap and reliable. GLP certification proves that melamine recovery rate is 85 -105%, CV <10%. Because of extraction Do not concentrate and dry the sample. LC-MS/MS analysis for 1-2 minutes, 400-600 samples per day.
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