tailieunhanh - Drugs and Poisons in Humans - A Handbook of Practical Analysis (Part 70)

Introduction: Nitrate and nitrite compounds are being used for various purposes, such as coronary artery dilators, coloring reagents for meat, rust preventives, fertilizers and explosives. When a nitrate salt is ingested by a human, nitric acid is converted into nitrous acid by the action of nitric acidreducing bacteria inhabiting the upper digestive tract; the nitrous acid oxidizes the divalent ferrous ion of hemoglobin to produce methemoglobin a with the trivalent ferric ion. When methemoglobin is produced, its reduction into hemoglobin starts by the action of methemoglobin reductase (identical with cytochrome b5 reductase requiring NADH as a cofactor) present in mammalian. | Nitrate and nitrite compounds by Takeshi Saito and Sanae Takeichi Introduction Nitrate and nitrite compounds are being used for various purposes such as coronary artery dilators coloring reagents for meat rust preventives fertilizers and explosives. When a nitrate salt is ingested by a human nitric acid is converted into nitrous acid by the action of nitric acidreducing bacteria inhabiting the upper digestive tract the nitrous acid oxidizes the divalent ferrous ion of hemoglobin to produce methemoglobina with the trivalent ferric ion. When methemoglobin is produced its reduction into hemoglobin starts by the action of methemoglobin reductase identical with cytochrome b5 reductase requiring NADH as a cofactor present in mammalian red cells. The concentration of methemoglobin in blood of normal subjects is not higher than 1-2 1 in case of higher concentrations of methemoglobin it is called methemoglobinemia. Especially in newborn babies and small infants methemoglobinemia can easily take place because of lower methemoglobin reductase activities in these periods. Methemoglobin is not capable of transporting oxygen. When methemoglobinemia becomes severe it causes cyanosis headache easy fatigability respiratory and conciousness disturbances and finally death. The fatal methemoglobinemia is rare but fatal ones after ingestion of nitrate or nitrite were reported 2-6 . For analysis of nitrate or nitrite in blood plasma or serum the methods by ion chlomatog-raphy 7 and GC MS 8 were reported. In this chapter a method for GC analysis of nitrate and nitrite in blood using wide-bore and medium-bore capillary columns after their derivatiza-tion with mesitylene b is presented. Reagents and their preparation Potassium nitrate is dried at 110 C for 4 h mg of the resulting compound is dissolved in 10 mL purified water. The concentration of nitrate ion in this solution is mg mL. Sodium nitrite is dried by keeping it in a desiccator for 24 h mg of the compound