Electrochemical sensor for trace determination of timolol maleate drug in real samples and drug residues using Nafion/carboxylated-MWCNTs nanocomposite modified glassy carbon electrode

A sensitive and selective differential pulse-adsorptive anodic stripping voltammetry (DP ASV) method has been developed for trace determination of timolol maleate drug in complex matrices. The established method is first of its kind for timolol maleate (TM) determination with a wide linear dynamic range (1.0 × 10−9-2.0 × 10−5 mol L−1) coupled with limits of detection and quantification of 7.1 × 10−10 mol L−1 (0.31 μg L−1) and 2.4 × 10−9 mol L−1 (1.04 μg L−1), respectively. A relative standard deviation (±0.565%, n = 5) at 2.0 × 10−6 mol L−1 concentration of the drug was obtained. The method was validated by comparison with standard HPLC method. Statistical treatment of data using Student t and F tests at P = 0.05 revealed no significant differences between experimental and tabulated t and F values. Due to high selectivity towards TM and minimum interference from common organic and inorganic compounds the developed probe was successfully applied for trace analysis of TM in an eye drop, urine and water samples. The established method has a unique advantage to be quantitatively applied to a variety of samples due to rapid response, short analytical time and high sensitivity, and excellent selectivity with good reproducibility. The figures of merits were compared successfully with some reported electrochemical, chromatographic and spectrochemical methods. The interfacial properties of the modified Nafion/c-MWCNTs/GCE were explored by electrochemical impedance spectroscopy (EIS).