Ten novel spectrophotometric approaches were developed for the initial examination of the Hydroxychloroquine and Paracetamol medications. These procedures are straightforward, specific, easy to use, and provide exact and accurate results. The determination was conducted through the utilization of several approaches, including zero order (dual wavelength, zero crossing, advanced absorption subtraction and spectrum subtraction), derivative (first derivative of zero crossing), ratio (ratio difference, ratio derivative) and mathematical (bivariate, simultaneous equation, and Q-absorbance) techniques. After undergoing validation in accordance with ICH criteria, it was established that each of these methods achieved acceptable levels of precision, repeatability, robustness, and accuracy. The advantages and disadvantages of each method are demonstrated, and the proposed and reported methodologies were statistically compared.

The UV spectra of Diclofenac Potassium DIC and Methocarbamol MET are superimposed making their analysis using direct or derivative spectrophotometric methods quite complicated. This study presents four effective spectrophotometric methods that enable simultaneous determination of both drugs without interference. The first method is based on application of simultaneous equation method on their zero order spectra where DIC has shown absorbance maxima at 276 nm and MET displays two absorbances maxima at 273 nm and 222 nm in distilled water. The second method relies on dual wavelength method, the two wavelengths (232 and 285 nm) were chosen for determination of DIC where the absorbance differences at these wavelengths are proportional to DIC concentration while the absorbance differences of MET are equal to zero. For the determination of MET, the two wavelengths (212 and 228 nm) were selected. The third method of first-derivative ratio has been applied where the derivative ratio absorbances of DIC and MET were measured at 286.1 and 282.4 nm, respectively. The fourth method utilizing ratio difference spectrophotometric (RD) method was eventually performed on the binary mixture. The amplitude difference between the two wavelengths (291and 305 nm) was calculated for DIC estimation while the amplitude difference between the two wavelengths (227and 273 nm) for MET determination. All methods show linearity range from 2.0-25 μg. mL-1 and 6.0-40 μg. mL-1 for DIC and MET respectively. The developed methods have been statistically compared with a reported method based on first derivative method and the results of statistical comparison confirm the accuracy and precision of the proposed methods therefore they can be effectively applied for determination of MET and DIC in pharmaceutical dosage form.

Simultaneous achievement of sustainable development goals (SDGs), especially energy efficiency (SDG 7), economic growth (SDG 8), and pollution reduction (SDG 13), has been a major challenge among the developing countries. Besides, there is absence of a study which quantifies clean production (net growth-emission effects) and energy import efficiency (net growth-energy import effects) as indicators of sustainable growth. Thus, this current study examines this issue for South Africa and Nigeria at aggregate and sectoral levels between 1981 and 2015 using simultaneous equation models and threshold regression analysis. Evidence of the sustainable growth cannot be established for South Africa and Nigeria with and without structural break. Further, the analysis shows that, with respect to Nigeria, keeping petroleum import per capita above the respective threshold enhances the environmental quality as aggregate and sectoral outputs increase. However, the CO2 emission can only induce increased GDP per capita when the petroleum import is below the threshold level. In South Africa\'s case, although maintaining petroleum import beyond the threshold may increase CO2 emission per capita associated with high aggregate output per capita, such emission exhibits a negligible reverse impact on output per capita. Results are found to vary across both lower and upper threshold regimes for sectors. Policy recommendations are discussed in the conclusion.

The water⁻energy⁻food (WEF) nexus attracts much attention due to the elevated public concern regarding environmental conservation and sustainability. As we head into a new era of civilization, population increase and modernized lifestyles have led to an increasing need for water, energy, and food. However, severe hydrological precipitation significantly impacts agricultural harvest, and such influence becomes more apparent under the influence of climate change. Meanwhile, the major method of electricity generation (i.e., fossil fuel burning) has a negative impact on the environment. These inevitable threats are crucial and have to be dealt with for a society on the road towards sustainability. In the present study, an integrated evaluation of the WEF nexus was conducted for two areas with different levels of urbanization using empirical multiple linear regression in a simultaneous equation model (SEM). By incorporating the collected data into the SEM, the weighting coefficient of each identified variable was obtained, and the nexus implication was assessed in model simulation at different scenarios considering the population growth, agro-technology advancement, energy structure improvement, and available water resources. In the simulated results, three observations were found: (1) the rural area is more sustainable than the urban one; (2) the sustainability for both the investigated areas is significantly subject to their water supply and demand; and (3) food production was found to have a less important effect on the sustainable development of the urban area. This study identified the key factors in the WEF nexus exploration, which are economically and environmentally important for resource allocation. An empirical model was developed to correlate sustainable achievement with WEF management, as well as strategic policies that should be implemented under the pressure of urbanization.

New univariate spectrophotometric method and multivariate chemometric approach were developed and compared for simultaneous determination of empagliflozin and metformin manipulating their zero order absorption spectra with application on their pharmaceutical preparation. Sample enrichment technique was used to increase concentration of empagliflozin after extraction from tablets to allow its simultaneous determination with metformin without prior separation. Validation parameters according to ICH guidelines were satisfactory over the concentration range of 2-12μgmL(-1) for both drugs using simultaneous equation with LOD values equal to 0.20μgmL(-1) and 0.19μgmL(-1), LOQ values equal to 0.59μgmL(-1) and 0.58μgmL(-1) for empagliflozin and metformin, respectively. While the optimum results for the chemometric approach using partial least squares method (PLS-2) were obtained using concentration range of 2-10μgmL(-1). The optimized validated methods are suitable for quality control laboratories enable fast and economic determination of the recently approved pharmaceutical combination Synjardy® tablets.

Four rapid, simple, accurate and precise spectrophotometric methods were used for the determination of ciprofloxacin in the presence of metronidazole as interference. The methods under study are area under the curve, simultaneous equation in addition to smart signal processing techniques of manipulating ratio spectra namely Savitsky-Golay filters and continuous wavelet transform. All the methods were validated according to the ICH guidelines where accuracy, precision and repeatability were found to be within the acceptable limits. The selectivity of the proposed methods was tested using laboratory prepared mixtures and assessed by applying the standard addition technique. So, they can therefore be used for the routine analysis of ciprofloxacin in quality-control laboratories.

Two simple spectrophotometric methods have been developed for simultaneous estimation of drotaverine hydrochloride and aceclofenac from tablet dosage form. Method I is a simultaneous equation method (Vierodt\'s method), wavelengths selected are 306.5 and 276 nm. Method II is the absorbance ratio method (Q-Analysis), which employs 298.5 nm as λ(1) and 276 nm as λ(2) (λmax of AF) for formation of equations. Both the methods were found to be linear between the range of 8-32 μg/ml for drotaverine and 10-40 μg/ml for aceclofenac. The accuracy and precision were determined and found to comply with ICH guidelines. Both the methods showed good reproducibility and recovery with % RSD in the desired range. The methods were found to be rapid, specific, precise and accurate and can be successfully applied for the routine analysis of drotaverine and aceclofenac in their combined tablet dosage form.

Three simple, accurate and economical methods have been developed for the estimation of norfloxacin and ornidazole in tablet dosage form. First method is based on the simultaneous equations, wavelengths selected for analysis were 273.0 nm (lambda(max) of norfloxacin) and 318.5 nm (lambda(max) of ornidazole), respectively, in 0.1N NaOH. Second method is Q-analysis method, based on absorbance ratio at two selected wavelengths 297.0 nm (iso-absorptive point) and 318.5 nm (lambda(max) of ornidazole). Third method is first order derivative spectroscopy using 297.5 nm (zero cross for norfloxacin) and 264.0 nm (zero cross for ornidazole). The linearity was obtained in the concentration range of 4-20 mug/ml and 5-25 mug/ml for norfloxacin and ornidazole, respectively. The results of the analysis have been validated statistically and by recovery studies.

Two simple, accurate and precise spectrophotometric methods have been developed for simultaneous determination of lansoprazole and domperidone in pharmaceutical dosage form. Method A involves formation of Q-absorbance equation at 256.0 nm (isoabsorptive point) and at 294.2 nm while method B is two wavelength method where 277.6 nm, 302.1 nm were selected as lambda(1) and lambda(2) for determination of lansoprazole and 231.3 nm, 292.0 nm were selected as lambda(1) and lambda(2) for determination of domperidone. Both the methods were validated statistically and recovery studies were carried out. The Beer\'s law limits for each drug individually and in mixture was within the concentration range of 5-50 mug/ml. Linearity of lansoprazole and domperidone were in the range of 24-36 mug/ml and 8-12 mug/ml, respectively. The proposed methods have been applied successfully to the analysis of the cited drugs either in pure form or in pharmaceutical formulations with good accuracy and precision. The method herein described can be employed for quality control and routine analysis of drugs in pharmaceutical formulations.