I. Overview
1. Chemical properties
Chloramphenicol (chloramphenicol, CAP) is a broad-spectrum antibiotic produced by the Venezuelan zipper mold, the molecular formula is CuH, OsN2CI. , The relative molecular mass is 322.
CAP is white needle-like or long plate-like crystal, melting point is 150.5 ~ 151.5 ℃, the maximum ultraviolet absorption wavelength is 278nm. The solubility of CAP in water is about 2.5 mg / ml at 25 ° C, and it is dissolved in 400 parts of water, 2.5 parts of 95% ethanol and 7 parts of propylene glycol at 20 ° C. It is easily soluble in most organic solvents (such as alcohols, acetone, ethyl acetate, etc.), but insoluble in benzene, petroleum ether and vegetable oils. The pH value of the saturated aqueous solution of CAP is 4.5 to 7.5.
CAP is very stable, boiled in boiling water for 5 hours without degradation, and can be maintained for 25 hours at pH 2-9 and room temperature. The body can be stored for more than two years. Hydrolysis can occur under acid, alkali (more sensitive) and heating conditions.
2. Pharmacology and Toxicology
CAP is a broad-spectrum antibiotic that can inhibit the synthesis of bacterial proteins and has a strong effect on Gram-negative bacteria. Escherichia coli, salmonella, typhoid bacillus, paratyphoid bacillus, dysentery bacillus, streptococcus, staphylococcus, bacillus anthracis, etc., are all sensitive to it. It also has a certain inhibitory effect on various Rickettsia and some protozoa viruses.
The internal absorption of CAP is good, but the absorption of injection is slow, and it is mainly retained locally. After absorption, it is distributed throughout the body and can penetrate the blood-brain barrier and the placental barrier. Most CAPs are inactivated by binding to glucuronic acid in the liver, and a few are degraded to aromatic amines. About 10% of the original CAP is excreted by the kidneys and can also be secreted through milk. Liver or kidney dysfunction prolongs elimination and is prone to accumulation poisoning.
The main toxic and side effect of CAP is to inhibit hematopoietic function. Mild cases can cause leukopenia. In severe cases, it can cause "gray syndrome" and aplastic anemia. The toxic and side effects are irreversible. The former is related to the dosage and frequency of use, and the latter is not related.
Second, the measurement method
Due to the important significance of CAP in residual toxicology, there have been many analytical methods in the past 20 years, mainly including immunoassay (ELISA), high performance liquid chromatography (HPLC), gas chromatography (GC), thin layer chromatography (TLC) ), Gas-mass spectrometry (GC ~ MS) and liquid-mass spectrometry (HPLC-MS). At present, ELISA method is mainly used for rapid screening, GC or HPLC for determination, and GC-MS method for confirmation.
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