Veterinary drug residue testing

1. Types of veterinary drug residues

Antibiotics: chloramphenicol, tetracycline, oxytetracycline, penicillin, etc.;

Sulfas: Sulfadiazine, Sulfamethazine, etc.;

Furans: furazolidone, nitrofurans, nitrofurantoin, etc.;

Hormones and β-stimulants: Clenbuterol, diethylstilbestrol, progesterone, etc.;

Anti-parasitic: levamisole, benzimidazole, kemidazole, globulin, praziquantel, etc.

1. Analysis methods of veterinary drug residues

Characteristics of veterinary drug residue analysis technology

• Low concentration of test substance
• The sample matrix is ​​complex and there are many interfering substances
• Different or unknown metabolic products of veterinary drugs
• Different types of animals, there are differences in drug metabolism

Analysis method of veterinary drug residue

ELISA: simple, fast and sensitive, but prone to false positives, generally only suitable for coarse screening of samples, positive results need to be confirmed.

GC: High sensitivity, but most veterinary drugs have high polarity or boiling point, requiring cumbersome derivatization steps, limiting the application.

HPLC: The operation is simple, but the sensitivity is not high; some residues, the detection limit cannot meet the requirements.

Combined use of instruments: integration of separation, qualitative and quantitative, sensitive, accurate and selective, is an international recognized method of confirmation, including GC/MS, LC/MS, etc.

GC sensitivity is high, but false positives are likely to occur, and positive results need to be further confirmed; HPLC operation is simple, but the sensitivity is not high; ELISA is simple, fast, and sensitive, but it is easy to produce false positives, generally only suitable for coarse sample screening, positive results need Confirmation; GC/MS and GS-MS/MS are the ones with higher sensitivity and better confirmation rate.

Mass Spectrometry (MS)

Mass spectrometry is an analysis method that analyzes the mass-to-charge ratio of the measured sample ions. After the compound molecules are impacted by the electron current, the positively charged molecular ions and fragment ions formed according to the ratio m/z (mass-to-charge ratio) of their mass m and charge z are sequentially arranged and recorded, which is called the mass spectrum.

The advantages and disadvantages of GC-MS

Chromatographs have a strong ability to separate mixtures, but have poor ability to characterize compounds. Mass spectrometric analysis samples must be highly pure, and mass spectrometry itself has no ability to separate mixtures, but it can be used to determine the relative molecular mass and chemical structure of compounds, and is an excellent qualitative tool.

When combined with gas chromatography-mass spectrometry, gas chromatography has high separation efficiency and accurate quantification, so gas chromatography is an ideal separator for mass spectrometry; similarly, mass spectrometry has high sensitivity and strong qualitative ability, and can detect almost all organic compounds Therefore, the mass spectrometer is an ideal detector for gas chromatography.

Gas chromatography first separates and quantifies volatile substances; mass spectrometry then performs component analysis and structural analysis by measuring ion mass and intensity. Therefore, the combination of the two is used to synthesize its advantages and overcome its deficiencies.