Determination of Roxithromycin Residues in Milk by UV-1500 Spectrophotometry - Master's thesis - Dissertation

Spectrophotometric determination of roxithromycin residues in milk. Key words: spectrophotometry; milk; roxithromycin; analysis instrument ; UV-1300 I. Experimental purpose master UV spectrophotometry The principle and method for detecting the amount of roxithromycin in milk samples. Second, the experimental principle Roxithromycin is a derivative of erythromycin, it can be degraded with concentrated HCl in glacial acetic acid, and can form a maximum absorption of colored substances at 486 nm with p-dimethylaminobenzaldehyde, and Compared with standard products, quantitative analysis can be achieved by colorimetry. Third, the instrument and the test material 1. Instruments and equipment UV-1300 UV spectrophotometer, centrifuge, ultrasonic cleaner, etc. 2. Reagents Unless otherwise specified, the reagents used in the experiments were of analytical grade and the water was deionized or distilled water. (1) Conventional reagents and solutions: glacial acetic acid, HCl, 95% ethanol, p-dimethylaminobenzaldehyde, HCl-glacial acetic acid mixture (2-+-1, volume ratio). (2) Color developing agent (O.5%): an appropriate amount of p-dimethylaminobenzaldehyde, prepared with glacial acetic acid. (3) Roxithromycin standard solution (0.8 mg/mL): The appropriate amount of roxithromycin standard (purity ≥99%) was weighed and prepared in 95% ethanol. 3. Experimental materials 2 to 3 kinds of fresh milk, each 50 mL. Fourth, the experimental steps 1. Sample extraction 1.00 g sample was weighed into a 100 mL stoppered conical flask, 10 mL of 95% ethanol was added, shaken to make it evenly dispersed, ultrasonically extracted for 20 min, centrifuged at 4000 r/min for 10 min, and the supernatant was a sample extract. 2. Determination (1) Take roxithromycin standard solution 0, 0.5mL, 1.0mL, 1.5mL, 2.0mL, 2.5mL, respectively placed in a 50mL volumetric flask, add glacial acetic acid 20mL, color developer 5. 0 mL, add HCl-glacial acetic acid mixture to the mark, shake well, the corresponding concentrations of roxithromycin were 0, 8 μg / mL, 16 μg / mL, 24 μg / mL, 32 μg / mL, 40 μg / mL. (2) After standing at 25-35 ° C for 15 min, measure A at the wavelength of 486 nm

486nm

With concentration as the abscissa, A

486nm

For the ordinate, draw a standard curve. (3) Take 2 mL of the sample extract, and measure the sample extract A according to the method described in (1) and (2).

486nm

The concentration of roxithromycin in the extract was found according to the standard curve. At the same time do reagent blanks. 3. Calculate the content of roxithromycin in the sample by the following formula: x=cV/m where x is the content of roxithromycin in the product, mg/kg; c is the concentration of roxithromycin in the sample extract , μg / mL; m is the mass of the sample, g; V is the volume of the sample extract, mL. V. Precautions During the measurement process, the amount of sample extract should be determined according to the content of roxithromycin in the sample. Key words: spectrophotometry; milk; roxithromycin; aesthetic instrument ; UV-1300