I. Overview
1. Chemical properties
Sulfonamides (sulfonamides, SAs) are a class of drugs with a p-aminobenzenesulfonamide structure, with a relative molecular weight between 170 and 300.
SAs are generally white or slightly yellow crystalline powder, odorless and almost tasteless. Slightly soluble in water, easily soluble in ethanol and acetone, almost insoluble in chloroform and ether. Except that sulfamidine is alkaline, SAs are amphoteric because they contain primary amine groups and sulfonamide groups, and can be dissolved in acid and alkali solutions. Because of the benzene ring in its structure, various SAs have ultraviolet absorption.
SAs mostly have aromatic primary amine groups, and the color gradually turns yellow when exposed to sunlight for a long time. It is generally quite stable and can be stored for several years if stored properly.
2. Pharmacology and Toxicology
SAs are mainly used to prevent and treat bacterial infectious diseases. Its antibacterial effect is due to its ability to interfere with the use of aminobenzoic acid by the bacterial enzyme system. P-aminobenzoic acid is a component of folic acid, which is an essential substance for the growth of microorganisms, and it is a basic raw material of oxidoreductase in its body.
SAs can be rapidly absorbed after oral administration. The concentration of the drug in plasma reaches the highest within 2 to 3 hours. The concentration in body fluid is 50% to 80% of the blood concentration. In organs and tissues, the stomach, kidney, mucosa and liver The concentration is higher. The concentration in other organs and muscles is only half of that in serum. The drug concentration in milk is 5% to 15% in serum. The concentration of bone and fat is the lowest.
SAs are mainly metabolized in the liver, and sulfonamides that are difficult to absorb in the intestinal tract are mainly excreted with feces, and sulfonamides that are easily absorbed in the intestinal tract are excreted through the kidneys. A small amount is discharged from breast milk, digestive juices and other secretions.
The action time and metabolic time of SAs in the body are longer, so sulfonamides ingested through any route may accumulate in the body. Drugs whose accumulation concentration exceeds a certain value are harmful to human function. The long-term presence of sulfonamide in the human body can cause many bacteria to develop resistance to sulfonamides. Therefore, the Codex Alimentarius Commission (CAC) and many countries stipulate that the total amount of SAs in animal feasibility organizations and the amount of a single sulfa drug should not exceed o. 1mg / k8, Japan stipulates that SAs should not be detected in food.
Second, the measurement method
People have conducted in-depth and comprehensive research on the detection of SAs residues in foods very early. From early spectrophotometry (UV), fluorescence (FL), thin layer chromatography (TLC), gas chromatography (GC) to phase chromatography (HPLC), gas chromatography-mass spectrometry since the 1980s ( GC-MS), liquid chromatography-mass spectrometry (HPLC-MS), capillary electrophoresis (CE) and supercritical fluid chromatography (SFC), etc. Among them, the most used is the reversed-phase HPLC method, which is used to analyze the residues of various sulfonamides.
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