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Background: The development of innovative approaches in drug analysis is a challenging task for medicine, pharmacy, and engineering sciences. For instance, the requirement of proper dosage forms in releasing active ingredients is crucial. It is essential to analyze drugs in biological liquids for early diagnosis and treatment purposes. Drug analysis is also of great importance to control the quality of pharmaceutical products, test their efficacy, and develop novel drug formulation. The present review is aimed to highlight the most recent spectrophotometric approaches applied to analyze various classes of drugs in biological media and/or dosage forms. Methods: Direct and derivative UV/UV-Vis spectrophotometry and a combination of various techniques with spectrophotometry, such as injection analysis and chemometrics, have most widely been applied in the analysis of dosage forms. In addition, emerging technologies, such as UV imaging allows to obtain the distribution of drug concentration in time-resolved 2D images based on UV light absorption, utilization of nanotechnology, self-assembled nanomaterials, and aptamer-based nanoparticles have gained interests to investigate drug assays and to quantify the proper drug release. Results: Due to their high versatility, ease of application, low cost, and fast response, spectrophotometric methods are one of the most preferable methods providing high accuracy and precision with a wide linear range in drug analysis. Conclusion: Selected examples demonstrating the applicability of spectrophotometric methods in pharmaceutical assays in this review might contribute to the overall importance of the analytical test used in modern pharmaceutical analysis.

The expectorant drug guaifenesin (GFN) electroanalytical analysis was performed on boron doped diamond electrode (BDDE) by cyclic voltammetry (CV), differential pulse voltammetry (DPV) and square wave voltammetry (SWV) methods. The results of CV studies indicate that the reaction mechanism of GFN in the oxidation direction on the BDDE is irreversible and diffusion controlled. The linearity ranges are 0.400 ˗ 100 µM and 0.800 ˗ 100 µM for DPV and SWV methods, respectively. Limit of detection (LOD) values are obtained as 1.47 nM for DPV and 2.92 nM for SWV. Quantitative analysis of GFN from the pharmaceuticals was performed with fully validated DPV and SWV methods without any pre-separation. The sensitive methods with good recovery, high precision and accuracy have been developed for the electroanalytical analysis of GFN.

Antiarrhythmic agents are used to suppress abnormal rhythms of the heart. Class II antiarrhythmic agents are beta blockers used to treat supraventricular tachycardias. Voltammetric analysis of class II antiarrhythmic drug active ingredients propranolol and acebutolol carried out with various modified/non-modified electrodes using cyclic voltammetry, linear sweep voltammetry, differential pulse voltammetry and square wave voltammetry were compiled from the literature. The effect of buffer solution and pH was investigated. Scan rate results obtained with the voltammetric methods showed whether the redox process of the drug active ingredient diffusion or adsorption controlled on the electrode used in the selected supporting electrolyte. Results of the quantitative analysis of these drugs were evaluated in terms of parameters such as linearity range, limit of detection, stability, robustness, repeatability, reproducibility and sensitivity. Accuracy and precision of the validated methods were investigated by combining the results obtained from the pharmaceutical dosage forms of the drug active ingredients. Finally, voltammetric behavior of the drugs in real samples such as human serum and urine was evaluated and it was examined whether the analysis results were affected by the other substances in real samples.

The electro-oxidation behavior of expectorantdrug guaifenesin (GUF) was studied on poly(Nile blue) modified glassy carbon electrodeby cyclic voltammetry and differential pulse voltammetry. Camsı karbon elektrotwas modified with electropolymerization of Nile blue for sensitivedetermination of GUF with voltammetric methods. The current peaks for GUFoccurred at around 1.130 V for differential pulse voltammetry when thepotential was scanned in the positive direction. The oxidation process of GUFhas shown irreversible and diffusion controlled behavior. The linear responsehas been obtained in the range from 6 × 10-7 to 1 × 10-4 M with the limit of detection 1.24 × 10-8 fordifferential pulse voltammetry in 0.1 M phosphate buffer solution at pH 3.0.Fully validated differential pulse voltammetry was successfully applied for thedetermination of GUF from pharmaceutical dosage form and obtained satisfyingresults., Ekspektorant bir ilaç etken maddesi guaifenesin (GUF)elektro-oksidasyon davranışı poli(Nil mavisi) modifiye camsı karbon elektrottadönüşümlü voltametri (DV) ve diferansiyel puls voltametri (DPV) ile çalışıldı.Camsı karbon elektrot, GUF’un voltametrik metodlarla hassas tayini için, Nilmavisinin elektropolimerizasyonu ile modifiye edildi. Potansiyel pozitif yöndetarandığında GUF’un pik akımı 1.130 V civarinda DPV ile oluştu. GUF’unoksidasyon prosesi tersinmez ve difüzyon kontrollü davranış gösterdi. DPV içindoğrusal cevaplar 6 × 10-7- 1 × 10-4 M, 1.24 × 10-8 yakalama alt sınırı (YAS)ile 0.1 M fosfat tamponu (FT) pH 3.0 içinde elde edildi. Tamamen valide edilmişDPV başarılı bir şekilde GUF’un farmasötik dozaj formundan miktar tayini içinuygulandı ve memnun edici sonuçlar elde edildi.