LAUSR

BACKGROUND Rifaximin, a semi-synthetic antimicrobial, does not present microbiological method described in official compendia, and in the literature there is a lack for this topic. The quality control of antimicrobials is extremely important to evaluate the real potency of the pharmaceutical product. OBJECTIVE A miniaturized turbidimetric method for determining the potency of rifaximin in tablets was developed and validated by turbidimetry, according to the international guidelines. METHODS Escherichia coli ATCC 10536 IAL 2393, BHI broth, inoculum at 8%, rifaximin in purified water with 20% ethanol at 5, 10, and 20 μg/mL and 530 nm were used. RESULTS The method was considered selective for rifaximin, as the adjuvants did not show activity; linear with correlation coefficients 0.9998 for standard and 0.9999 for sample; accurate with 99.73% recovery; precise with RSD less than 3%; and robust in the face of small variations in (i) rifaximin volume, (ii) proportion of ethanol, (iii) inoculum volume. CONCLUSION The method is considered adequate and safe to evaluate the potency of rifaximin in tablets, contemplating speed, low cost, low waste generation, and ease of operation. HIGHLIGHTS This work shows the current, sustainable, and green analytical chemistry and can be used in the routine analyzes of rifaximin by laboratories and the pharmaceutical industry around the world.