Fluorimetric Determination of Kanamycin in Injections and Milk Samples by Quenching of Fluorescence of Carbon Quantum Dots by Kanamycin

Carbon quantum dots (CQDs), a kind of nanomaterial possessing high fluorescence intensity, were prepared from coal powdow. At the excitation wavelength (λ_ex) of 370 nm, CQDs showed its emission wavelength (λ_em) of 495 nm. Kanamycin (KANA) showed quenching effect on the fluorescence of CQDs, and the magnitude of the decrease of fluorescence intensity of CQDs was found to keep a linear relationship with concentration of KANA in the range of 5.0 to 140.0 μmol·L^-1, with detection limit (3s/k) of KANA 1.0 μmol·L^-1. Further testings were made for applying this fluorescence quenching reaction to determination of KANA in its injections and in milk samples. The optimum reaction conditions were given as follows: ① the reaction medium chosen was pH 7.5 tri(hydroxymethyl)aminomethane (Tris-HCl) buffer solution; ② amount of CQDs added was 0.5 mL; and ③ reaction time was 10 min. Preparation of sample solutions was done as follows: ① for KANA injection sample, 5 injections were taken and mixed thoroughly, an aliquot of 0.1 mL was taken and diluted to 100.0 mL with water. After filtering through filtering membrane, the filtrate was used for determination; ② for milk samples, 10.0 g of the sample were taken and diksted to 50.0 mL with absolute alcohol. After staying for 30 min, the mixed solution was centrifuged, and the surpernatant was used for determination. An appropriate amount of the sample solution was taken, and 0.5 mL each of the Tris-HCl buffer solution and ths CQDs were added to the sample solution, and the volume was made up to 5.0 mL with water. Fluorescence intensity (F) of the solution was measured under the condition given above, and fluorescence intensity (F₀) of blank solution was measured simultaneously. Values of recovery found by recovery test were found in the range of 97.0% to 104%, and RSDs (n=6) found were ranged between 1.2% and 2.6%. Samples were analyzed by the present method and checked by HPLC determination, results obtained by the 2 methods were found in good conformity. Result of KANA found in injection sample (99.6 g·L^-1) was in consistency with its labelled value (100 g·L^-1).