Studies on complexes of rare earth elements with tetracycline antibiotics by spectrophotometry

In pH 7 similar to 8 weak basic medium, rare earth elements react with tetracycline(TC), doxycycline(DOTC), oxyteracycline(OTC), and chlortetracycline(CTC) to form light yellow complexes. La(III) and Y(III) were studied as examples, the maximum absorption peaks of reaction products produced by the reactions of La(III), Y(III) and different antibiotics were located between 388 similar to 394 nm and 388 similar to 398 nm respectively. They can be applied to the photometric determination of antibiotics such as tetracycline. When La(III) was used for determination, the linear ranges were between 0 similar to 9.0 mg/L to 0 similar to 14.0 mg/L. The molar absorptivities were between 1.49 x 10(4) and 2.29 x 10(4) L.mol(-1).cm(-1). When Y(III) was used to the determination, the linear ranges were between 0 similar to 10.0 mg/L to 0 similar to 11.0 mg/L, and molar absorptivities were between 1.53 x 10(4) and 2.47 x 10(4) L.mol(-1).cm(-1). The method was applied to the determination of antibiotics and satisfactory results were obtained.