Simultaneous Determination of Nitrite and Nitrate in Whole Blood by GC£­NCI£­MS with Derivatization

KeyWord:nitrite  ?nitrate  ?whole blood  ?gas chromatography£­negative chemical ionization£­mass spectrometry£¨GC£­NCI£­MS£©  ?toxicological analysis

Abstract:

      A gas chromatography£­negative chemical ionization£­mass spectrometry£¨GC£­NCI£­MS£© with derivatization was developed for the quantitative analysis of nitrite£¨NO?22-£© and nitrate£¨NO?33-£© in whole blood. Isotope-labeled?15NO?22- and 15NO?33- were used as the internal standards£®After NO?22- and NO?33- in whole blood were extracted and derivatized£¬the target derivatives were analyzed by GC£­NCI£­MS. The target extraction solvent£¬derivative extraction solvent£¬amount of phase transfer reagent£¬the derivatization method£¬time and temperature of the derivatization reaction were optimized£®The optimal pretreatment conditions were also determined£®A negative chemical ionization source£¨NCI£© was used to select ion monitor£¨SIM£©£®The quantitative ions for target NO?22- and its internal standard 15NO?22- were m/z 46 and 47£¬while those for target NO?33- and its internal standard 15NO?33- were m/z 62 and 63£¬respectively£®There was a good linear relationship for NO?22- in whole blood£¨r2 = 0.995£© in the range of 0.05£­5 ¦Ìg/mL£¬with a detection limit of 0.01 ¦Ìg/mL and an accuracy of 89.6%£­98.0%£®The extraction recoveries ranged from 99.8% to 118%£¬with the intra-day and inter-day relative standard deviations£¨RSDs£© of 1.8%£­9.2% and 2.1%£­6.2%£¬respectively£®There also existed a good linear relationship for NO?33- in whole blood£¨r2 = 0.997£© in the range of 1£­300 ¦Ìg/mL£¬with a detection limit of 0.2 ¦Ìg/mL and an accuracy of 92.8%£­112%£®The extraction recoveries ranged from 80.3% to 88.4%£¬with the intra-day and inter-day RSDs of 0.60%£­14% and 0.60%£­3.7%£¬respectively. The endogenous NO?22- and NO?33- in 16 whole blood samples of healthy person were determined by this method£®The results showed that the concentrations of NO?22- and NO?33- were in the ranges of 0.05£­0.10 ¦Ìg/mL and 1.70£­7.70 ¦Ìg/mL£¬respectively£®In addition£¬the contents of two target substances in real human whole blood poisoned by nitrite were determined£¬and the concentrations of both substances were much higher than the endogenous concentration level in whole blood of human body£¬thus nitrite poisoning was determined£®With the advantages of strong specificity£¬high sensitivity£¬accuracy and reliability£¬the method could meet the requirements for inspection and identification of nitrite poison cases£®