Development Of Two Types Nitrite Rapid Test Reagents

Nitrite is a important food hygiene and safety index of milk, meat and vegetable products. Instrumental detection of nitrite is precise, however, its operation is rather complicated and time consuming, and not efficient for large scale screening test. The shortcomings of nowadays nitrite rapid test, especially in milk, are low detection sensitivity and insufficient anti-interference ability. Thus developing more robust nitrite qualitative and semi-quantitative rapid test is of great practical importance.Based on purple diazo coupling reaction principle of nitrite detection, a semi-solid gel nitrite test tube (semi-solid test tube) and a nitrite test strip were designed and developed. Diazo coupling reagent was optimized, proper gel carrier for test tube and paper carrier for test strip were selected, and protection reagents were optimized. Meanwhile, the effect of several possible interfering reagents that may exist in water and milk system were examined as well.The optimal chromogenic reagents combination that superior to the classic Griess reagent(i.e. Diazo coupling reagents applied in GB/T 5009.33-2008), for two type of test reagent were(w/v):A2 0.65%, B2 0.12%, tartaric acid was 5%, and the solvent was methanol 60%(v/v) water solution. An acidity-resistant gel material-I was applied in production of semi-solid test tube; paper carrier for test strip was selected among over twenty types of water absorbent papers; while, the protection reagents selection were not ideal enough, still remains further to study.Nitrite sodium detection limit of semi-solid gel test tube and the test strip in water and milk system were 0.1-0.2 mg/L, i.e. test sensitivity of the two test were significantly higher than most domestic similar test strip(detection limit in milk generally is above 0.8 mg/L), promise the nitrite testing needs of raw milk (MRL 0.4 mg/LNaNO2). The semi-solid test tube is a major innovation of the study, characterized in unique design of interface reaction, slower/stable color reaction, higher reagents carry ability, higher buffering capacity and more resistance to interference substances or effects that exist in milk system. However, the protection, i.e. shelf life postponing still remains further studies.