Fabrication of graphene nanosheet-multiwalled carbon nanotube-polyaniline modified carbon paste electrode for the simultaneous electrochemical determination of terbutaline sulphate and guaifenesin

A sensitive electrochemical method is developed for the simultaneous determination of terbutaline sulphate (TBS) and guaifenesin (GF) at a carbon paste electrode modified with graphene nanosheet-multiwalled carbon nanotube-polyaniline composite (GNS-MWCNT-PANI). The GNS-MWCNT-PANI composite is synthesized via the in situ oxidative polymerization of aniline in the presence of graphene nanosheets and multi-wall carbon nanotubes. The surface characterization of the as-synthesized composite is carried out using various techniques including X-ray diffraction, scanning electron microscopy, the Brunauer-Emmett-Teller method and transmission electron microscopy. Additionally, the electrochemical behavior of TBS and GF is investigated via cyclic voltammetry, adsorptive stripping differential pulse voltammetry and electrochemical impedance spectroscopy. The nanocomposite based sensor exhibits an excellent electrochemical response towards the oxidation of TBS and GF. Moreover, an adsorptive stripping differential pulse voltammetry method is developed and validated for the quantitative analysis of TBS and GF in pharmaceutical formulations, human urine and blood serum samples. Under the optimized experimental conditions, the linear working range was found to be 2.0 x 10(-8)- 8.0 x 10(-5) M and 6.0 x 10(-8)-8.0 x 10(-5) M for TBS and GF, respectively, and the limit of detection was established as 5.83 x 10(-9) M and 7.03 x 10(-9) M for TBS and GF, respectively. The proposed sensor is fabricated via a very simple method and at an extremely low cost with high sensitivity, selectivity and stability and is thus a promising tool for sensing TBS/GF in quality control laboratories.