Development of recycled and miniaturized electroanalytical sensor: Probing isoniazid determination in environmental water matrices

Surface water pollution has become relevant because growing population and intense industrial activities. Thus, to protect the environment from contamination, recently the electroanalytical sensors that require small sample volume and easy preparation have shown a prominent performance for pharmaceuticals monitoring. For this purpose, a miniaturized electrochemical platform was developed based on recycling obsolete computer integrated circuits (microchips), fitting with the ideals of green chemistry and circular economy. The gold microelectrodes array (Au-μEA) was easily exposed by polishing the device surface and then characterized by optical microscopy, scanning electron microscopy and cyclic voltammetry. To enhance the analytical performance for isoniazid detection, the Au-μEA was modified with electrochemically reduced graphene oxide (ERGO). The developed sensor presented a linear range between 5 and 100 μmol L-1 and a limit of detection of 1.38 μmol L-1 demonstrating a reliable performance. Looking to its environmental application, the ERGO/Au-μEA sensor was used for isoniazid quantification in lagoon, river, tap water and synthetic effluent spiked samples with recovery values between 92.5 and 108.4%. Thus, this research field opens up new possibilities in global water-related issues contributing with innovative sustainable solutions.

Development of non-aqueous titrimetric and spectrophotometric methods for the determination of valganciclovir hydrochloride in bulk drug and tablets

Two non-aqueous titrimetric and one visible spectrophotometric methods were developed and validated for the determination of valganciclovir hydrochloride (VLGH) in pure drug and tablets. The titrimetric methods were carried out by titrating the VLGH solution in glacial acetic acid with acetous perchloric acid (HClO₄) in the presence of mercuric acetate and the end point of this titration was being located either visually (method A) or potentiometrically (method B). The spectrophotometric method (method C) was based on the addition of p-dimethylaminobenzaldehyde (DMAB) solution to VLGH solution and the formed yellow condensation product was measured at 420nm. In titrimetric procedures, both the methods A and B were applicable over the range of 4-20mg VLGH, and the calculations were based on a 1:1 reaction stoichiometry (VLGH:HClO₄). In a spectrophotometric method, Beer's law was valid in a concentration range of 5-50 μg/mL VLGH with the corresponding value of molar absorptivity of 4.43×10³L/mol cm for method C. The limits of detection (LOD) and quantification (LOQ) for method C were 0.3 and 0.92μg/mL, respectively. The developed methods were successfully applied to the determination of VLGH in tablets, and the results were statistically compared with those of a reference method by applying Student's t-test and F-test. Further, the validity of the developed methods was confirmed by recovery studies via standard addition technique.

Electroanalysis of isoniazid and rifampicin: Role of nanomaterial electrode modifiers

Thanks to operational simplicity, speediness, possibility of miniaturization and real-time nature, electrochemical sensing is a supreme alternative for non-electrochemical methodologies in drug quantification. This review, highlights different nanotech-based sensory designs for electroanalysis of isoniazid and rifampicin, the most important medicines for patients with tuberculosis. We first, concisely mention analyses with bare electrodes, associated impediments and inspected possible strategies and then critically review the last two decades works with focus on different nano-scaled electrode modifiers. We organized and described the materials engaged in several categories: Surfactants modifiers, polymeric modifiers, metallic nanomaterials, carbon based nano-modifiers (reduced graphene oxide, multi-walled carbon nanotubes, ordered mesoporous carbon) and a large class of multifarious nano composites-based sensors and biosensors. The main drawbacks and superiorities associated with each array as well as the current trend in the areas is attempted to discuss. Summary of 79 employed electrochemical approaches for analysis of isoniazid and rifampicin has also been presented.