Quantitative analysis of two COVID-19 antiviral agents, favipiravir and remdesivir, in spiked human plasma using spectrophotometric methods; greenness evaluation.

Favipiravir and remdesivir have been included in the COVID-19 treatment guidelines panel of several countries. The main objective of the current work is to develop the first validated green spectrophotometric methods for the determination of favipiravir and remdesivir in spiked human plasma. The UV absorption spectra of favipiravir and remdesivir have shown some overlap, making simultaneous determination difficult. Due to the considerable overlap, two ratio spectra manipulating spectrophotometric methods, namely, ratio difference and the first derivative of ratio spectra, enabled the determination of favipiravir and remdesivir in their pure forms and spiked plasma. The ratio spectra of favipiravir and remdesivir were derived by dividing the spectra of each drug by the suitable spectrum of another drug as a divisor to get the ratio spectra. Favipiravir was determined by calculating the difference between 222 and 256 nm of the derived ratio spectra, while calculating the difference between 247 and 271 nm of the derived ratio spectra enabled the determination of remdesivir. Moreover, the ratio spectra of every drug were transformed to the first order derivative using ∆λ = 4 and a scaling factor of 100. The first-order derivative amplitude values at 228 and 251.20 nm enabled the determination of favipiravir and remdesivir, respectively. Regarding the pharmacokinetic profile of favipiravir (Cmax 4.43 µg/mL) and remdesivir (Cmax 3027 ng/mL), the proposed methods have been successfully applied to the spectrophotometric determination of favipiravir and remdesivir in plasma matrix. Additionally, the greenness of the described methods was evaluated using three metrics systems: the national environmental method index, the analytical eco-scale, and the analytical greenness metric. The results demonstrated that the described models were in accordance with the environmental characteristics.

Stability indicating spectrophotometric methods for quantitative determination of bromazepam and its degradation product.

Four simple, sensitive and selective stability indicating spectrophotometric methods are presented for quantitative determination of the benzodiazepine drug; bromazepam (BMZ) and one of its reported potential impurities and degradation product; 2-(2-amino-5-bromobenzoyl) pyridine (ABP) in methanol. Method A, is isoabsorptive point coupled with D0 method, where good linearity was obtained by measuring the absorbance of BMZ at 264 nm (Aiso) in the concentration range of 2-25 µg mL-1, and the absorbance of ABP at its λmax 396 nm in concentration range of 0.5-24 µg mL-1. Method B, is ratio subtraction; the absorbance was measured at 233 nm for BMZ using 20 µg mL-1 of ABP, while ABP was determined directly at its λmax 396 nm using methanol as a solvent. Method C, was based on measuring the total peak amplitude of the first derivative of the ratio spectra (DD1) of BMZ from 301 to 326 nm using 10 µg mL-1 of ABP as a divisor and determination of ABP at peak amplitude of 293 nm using 5 µg mL-1 of BMZ as a divisor. In method D, ratio difference method, good linearity was achieved for determination of BMZ and ABP by measuring the differences between the amplitudes of ratio spectra at 312 nm and 274 nm and differences between the amplitudes of ratio spectra at 274 nm and 312 nm, respectively. The stability of BMZ was investigated under different ICH recommended forced degradation conditions. The suggested methods were then successfully applied for determination of BMZ in its pharmaceutical formulations.

Spectrophotometric assessment of the brand new antiviral combination: Sofosbuvir and velpatasvir in their pure forms and pharmaceutical formulation.

Sofosbuvir (SOF) and velpatasvir (VEL) are recently co-formulated together for the treatment of hepatitis C virus. Smart and robust spectrophotometric methods were first developed and validated for quantification of SOF and VEL in their pure forms and in their combined pharmaceutical formulation without preliminary separation. VEL has two UV maxima at 302.5 and 337.0 nm that allow its direct determination by zero-order spectrophotometric method (D°) without any interference from SOF in a linear range of 2.0-30.0 µg/mL. On the other hand, determination of SOF in presence of VEL was carried out by four smart spectrophotometric methods, developed for resolving the overlaid spectra of these binary mixture. These methods are dual wavelength (DW), ratio subtraction (RS), ratio difference (RD) and first derivative of ratio spectra method (1DD). Linearity was checked and found to be in the range of 5.0-90.0 µg/mL for SOF by all of the aforementioned spectrophotometric methods. The developed methods were optimized and validated in accordance to the ICH guidelines. They were successfully utilized for estimating both SOF and VEL in their pure forms, laboratory prepared mixtures and in their pharmaceutical formulations with good recoveries. The methods can be easily applied for the routine analysis in quality control laboratories.

Innovative spectrophotometric methods for simultaneous estimation of the novel two-drug combination: Sacubitril/Valsartan through two manipulation approaches and a comparative statistical study.

Different innovative spectrophotometric methods were introduced for the first time for simultaneous quantification of sacubitril/valsartan in their binary mixture and in their combined dosage form without prior separation through two manipulation approaches. These approaches were developed and based either on two wavelength selection in zero-order absorption spectra namely; dual wavelength method (DWL) at 226nm and 275nm for valsartan, induced dual wavelength method (IDW) at 226nm and 254nm for sacubitril and advanced absorbance subtraction (AAS) based on their iso-absorptive point at 246nm (λiso) and 261nm (sacubitril shows equal absorbance values at the two selected wavelengths) or on ratio spectra using their normalized spectra namely; ratio difference spectrophotometric method (RD) at 225nm and 264nm for both of them in their ratio spectra, first derivative of ratio spectra (DR1) at 232nm for valsartan and 239nm for sacubitril and mean centering of ratio spectra (MCR) at 260nm for both of them. Both sacubitril and valsartan showed linearity upon application of these methods in the range of 2.5-25.0µg/mL. The developed spectrophotmetric methods were successfully applied to the analysis of their combined tablet dosage form ENTRESTO™. The adopted spectrophotometric methods were also validated according to ICH guidelines. The results obtained from the proposed methods were statistically compared to a reported HPLC method using Student t-test, F-test and a comparative study was also developed with one-way ANOVA, showing no statistical difference in accordance to precision and accuracy.

Simultaneous determination of the brand new two-drug combination for the treatment of hepatitis C: Sofosbuvir/ledipasvir using smart spectrophotometric methods manipulating ratio spectra.

In this work, various sensitive and selective spectrophotometric methods were first introduced for the simultaneous determination of sofosbuvir and ledipasvir in their binary mixture without preliminary separation. Ledipasvir was determined simply by zero-order spectrophotometric method at its λmax=333.0nm in a linear range of 2.5-30.0µg/ml without any interference of sofosbuvir even in low or high concentrations and with mean percentage recovery of 100.05±0.632. Sofosbuvir can be quantitatively estimated by one of the following smart spectrophotometric methods based on ratio spectra developed for the resolution of the overlapped spectra of their binary mixture; ratio difference spectrophotometric method (RD) by computing the difference between the amplitudes of sofosbuvir ratio spectra at 228nm and 270nm, first derivative (DD1) of ratio spectra by measuring the sum of amplitude of trough and peak at 265nm and 277nm, respectively, ratio subtraction (RS) spectrophotometric method in which sofosbuvir can be successfully determined at its λmax=261.0nm and mean centering (MC) of ratio spectra by measuring the mean centering values at 270nm. All of the above mentioned spectrophotometric methods can estimate sofosbuvir in a linear range of 7.5-90.0µg/ml with mean percentage recoveries of 100.57±0.810, 99.92±0.759, 99.51±0.475 and 100.75±0.672, respectively. These methods were successfully applied to the analysis of their combined dosage form and bulk powder. The adopted methods were also validated as per ICH guidelines and statistically compared to an in-house HPLC method.

Quantitative determination of zopiclone and its impurity by four different spectrophotometric methods.

Four simple, sensitive and selective spectrophotometric methods are presented for determination of Zopiclone (ZPC) and its impurity, one of its degradation products, namely; 2-amino-5-chloropyridine (ACP). Method A is a dual wavelength spectrophotometry; where two wavelengths (252 and 301 nm for ZPC, and 238 and 261 nm for ACP) were selected for each component in such a way that difference in absorbance is zero for the second one. Method B is isoabsorptive ratio method by combining the isoabsorptive point (259.8 nm) in the ratio spectrum using ACP as a divisor and the ratio difference for a single step determination of both components. Method C is third derivative (D(3)) spectrophotometric method which allows determination of both ZPC at 283.6 nm and ACP at 251.6 nm without interference of each other. Method D is based on measuring the peak amplitude of the first derivative of the ratio spectra (DD(1)) at 263.2 nm for ZPC and 252 nm for ACP. The suggested methods were validated according to ICH guidelines and can be applied for routine analysis in quality control laboratories. Statistical analysis of the results obtained from the proposed methods and those obtained from the reported method has been carried out revealing high accuracy and good precision.