Sensitive phosphorimetric determination of bumetanide in human urine with its inhibition effect on the formation of [Fe-morin]3+ complex.

A novel solid substrate-room temperature phosphorimetry (SS-RTP) was developed for determination of bumetanide (BMTN). It was validated by determining selectivity, linearity, accuracy, precision, and signal to noise ratio (S/N) for analysis. And all the experiments presented in this work were based on that BMTN inhibited the formation of Fe-morin (FeR) complex by the reaction between Fe(3+) and R, which led to severe quenching of room temperature phosphorescence (RTP) signal. The rate constant of the reaction (k) was 2.44 x 10(-4) s(-1), the activation energy (E) was 21.39 kJ mol(-1). Detection limit of this method (LD, 5.0 ag spot(-1), corresponding concentration was 1.2 x 10(-14) g mL(-1)) was evaluated and compared with other methods, indicating better sensitivity for BMTN determination using this technique. And due to the high sensitivity of the method, it has been successfully applied to determine BMTN in human urine samples. The linear range was from 0.040 pg mL(-1) to 4.0 pg mL(-1), allowing wide determined range of BMTN. Meanwhile, the mechanism of this method was also discussed.