GB/T 19423-2020 in English

GB/T19423-2020 stipulates two methods: high performance liquid chromatography and liquid chromatography-tandem mass spectrometry for the determination of nicarbazin residues in feed, which is suitable for the detection of compound feed, concentrated feed and additive premix feed.

HPLC method

A C18 column (250mm×4.6mm, 5μm) was used, acetonitrile-water (50+50) was used as the mobile phase, and the detection was carried out at a wavelength of 350nm. The sample was extracted with a methanol-acetonitrile (50+50) mixed solution, and the sample was injected and analyzed after MAX column purification.

LC-MS/MS method

A C18 chromatographic column (2.7μm) with a diameter of 100mm×2.1mm was used, and the electrospray ionization mode (ESI-) and multiple reaction monitoring (MRM) were used. The characteristic ion pairs were 300.90＞137.05 (quantitative) and 300.90＞107.05 (qualitative).

• Extraction temperature control: 50℃ water bath ultrasonic extraction needs to keep the temperature constant±1℃
• Purification step: MAX column needs to be activated with 3mL extraction solution before use
• Mass spectrometer tuning: Standard solution needs to be used to optimize mass spectrometer parameters before daily testing
• Matrix effect: LC-MS/MS method must use a matrix-matched standard curve

Inter-laboratory validation shows:

• HPLC recovery rate 82%-95%, RSD<8%
• LC-MS/MS recovery rate 85%-102%, RSD<5%
• The relative deviation of the results of the two methods is <12%

1. HPLC is preferred for routine screening, and suspected positive samples are confirmed by LC-MS/MS
2. Pay attention to the sample weight control when testing additive premixes (nicarbazine content ≤10mg)
3. Establish laboratory internal quality control charts to monitor method stability
4. Each batch of tests should include blank controls and spike recovery experiments