Objective:To establish a high-performance liquid chromatography method for the simultaneous determination of metronidazole,chloramphenicol,oxytetracycline,and tetracycline in toothpaste.Methods:CAPCELL PAK C18 MGⅡ chromatography column is used,with acetonitrile methanol 0.01%oxalic acid aqueous solution as the mobile phase,flow rate of 1.0 mL/min,column temperature of 30℃,detection wavelength of 268 nm,injection amount of 10.0 μL,external standard method for quantification,and high-performance liquid chromatography for detection.Results:Within a certain concentration range,the linear relationship between the four prohibited substances is good,and the correlation coefficient R2 is greater than 0.999.The detection limits for metronidazole,chloramphenicol,oxytetracycline,and tetracycline are 50 μg/g,1.0 μg/g,1.0 μg/g and 1.0 μg/g,respectively.The recovery rates of four prohibited substances at high,medium,and low concentration levels are 83.9%to 111.0%,with a relative standard deviation of 0.4%to 3.8%(n=6).Conclusion:This method is easy to operate,has high recovery rate,high precision,and good reproducibility,and can be used for the determination of metronidazole,chloramphenicol,oxytetracycline,and tetracycline content in toothpaste.
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