Determination Method Of Nitrite, Formaldehyde, Sulfite By HPLC And Application In Water Products

The paper is divided into three parts. In first part, a high performance liquid method using fluorescence detection is developed for determination of nitrite in water foods, using method researches influence of nitrite to aquiculture and disposing. Experiment utilizes principle that nitrite reacts with DAN to produce fluorescent NAT. Through optimizing chromatographic condition: V (acetonitrile):V (distilled water)=40﹕60 at a flow-rate of 0.8 mL/min is used as mobile phase. Fluorescence is monitored with excitation at 375 nm and emission at 415 nm. The limit of quantification(LQ) (0.01 mg/kg) is lower than Spectroscopic methods ( 1.0 mg/kg),Electrochemical detection(0.24 mg/kg), spectrofluorimetric methods(8.0 mg/kg)and ion chromatography(0.8 mg/kg).The linear plots are obtained between 0.01 mg/Kg～4 mg/Kg , r=0.9999. Average recovery is between 83.6%～96.5% , with RSD(n=6) values between 1.0 %～5.0%. Using nitrite as pollution researched, the pharmacokinetics properties and residue depletion of nitrite is studied. Chlorine and bromine ion influencing nitrite being absorbed is explored, The blood and muscle data are both described by a two-compartment and first-order elimination. Data is analyzed by 3p97 pharmacokinetic software. The elimination half life (t1/2β) of nitrite in blood and muscle are calculated to be 5.36, 7.98 d and total body clearance( CLT ) to be 83.1, 54.7 mg/L(kg)/d. Date indicates nitrite in Carassius auratus metabolizes slowly. The concentration in liver and blood is the mostly remained tissue. After 15 d, concentration of nitrite in muscle reduced to 0.017 mg/kg, which are lower than the maximum residue limit (MRL) of 0.2 mg/kg demanded by the world. Three groups individuals are exposed to concentrations of 20 mg/L nitrite-N. The same time two groups are appended 18.4 g NaCl , 30.0g NaBr, NO2-:Cl-(Br-)mol =20∶1. The results show the groups appended NaCl, NaBr are lower than only nitrite solution in three tissues. The groups appended NaCl are lowest. This provides evidence chloride, bromine and nitrite has the same uptake mechanism. Simutiniously using ClO2, NaClO, CaCO3, active carbon to eliminate nitrite, ClO2 was perfect by comparing effect.An improved, sensitive method for the determination of formaldehyde is developed in water products. It is followed by precolumn derivatizat- ion with 2, 4- dinitrophenylhydraz- ine and direct reversed-phase high-performanceliquid chromatography. Linearity is verified from 0.216~43.2μg/mL, The limit of quantification(LOQ) (0.13 mg/kg)is lower than method of titration(100 mg/L) and Spectroscopic methods(1 mg/L),manipulation course saves much time and avoides volatilization of formaldehyde because of lower melting and boiling point. Fresh fish determined showes that formaldehyde is less in water than in sea water. Harpadon nehereus has much formaldehyde.A method is described for determining sulfite in different matrixes. After extracted from the sample, sulfite is converted to hydroxyl-methyl-sulfonate (HMS) by adding formaldehyde and heating to 50℃. HMS is determined by reversed-phase ion-pairing liquid chromatography with post-column detection. In the post-column system, HMS is converted to sulfite ion, which then reacts with DTNB to produce 5-mercapto-2-nitrobenzoic acid and detected spectrophotometrically at 450 nm. The detection limits (S/N≥3) for sulfite was 0.15 mg/kg. The method is safe avoiding HgCl4 used. Limit of detection is more sensitive than ion chromatography(0.33 mg/kg). Manipulation course saves much time than distillation-iodine method. Average recovery is 93.6%, and relative standard deviations less than 2%. In general, three methods are sensitive, simple, accurate, and rapid.