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There have been 2 spectrophotometric techniques developed, validated to find out how much folic acid there is that is simple to use, sensitive to detect, and selective. One method reduces ferric chloride in a neutral medium while simultaneously adding folic acid, and the second method is to chelate iron (II) along with 1, 10-phenanthroline (method A) on one hand and Method B depends on the interaction of the primary amino group of folic acid with the amino group of Ninhydrin in an alkaline solution, On the other hand. In Method A, red chromogens with a wavelength of 505 nm are produced, whereas, in Method B, violet chromogens with a wavelength of 575 nm are produced, and so on. Beer's law holds under ideal conditions in molar absorptivity values of 2.331104 L.mol-1 cm-1 and 6.771104 L.mol-1 cm-1, respectively, for concentration ranges of 1.0–35.0 g ml-1 and 0.5–10.0 g ml-1. Sandell's sensitivity values of 1.944 × 10–6 µg cm-2 and 1.6728 × 10–6 µg cm-2, respectively, and Sandell Technically, technique A and method B had limits of detection (LODs) of 0.198 and 0.488, respectively, and limits of quantification (LOQs) of 0.600 and 1.479, respectively. The correlation coefficients (R2) for technique A and method B were both 0.9979 and 0.9988. A and B used stability constants of 5.6192 and 5.4633 kJ.mol-1, respectively, and Gibbs free energy change (ΔG) values of −25.6071 and −24.8963, respectively, in their calculations of the free energy change (ΔG). The proposed methodologies were successfully used to evaluate folic acid in both pure and tablet form, with no influence from common excipients found in pharmaceutical formulations, demonstrating their efficacy. According to the study, there were no statistically significant differences between the precision and accuracy of the suggested procedures and those produced using the reference approach.

The three novel easy, to the prepare and sensitive spectral methods, were used to estimate metoclopramide in both standard and pharmaceuticals. The effective double–electron, was present in the metoclopramide compound helps to interact in an acidic medium with a reagent such as diazetide resorcinol and 8-hydroxyquinoline reagents. The present article was extended to find out three analytical methods with UV-V is the detector. In both A and B methods, two azo-dyes are formed, they are orange-red and red stable and have high water solubility, giving highest absorption values at 415 nm and 485 nm but the C method will depend on a complex colour configuration with the p-benzoquinone reagent, which has a maximum absorption at a wavelength of 285 nm. Beer's law was applied in a range of concentrations between 1 and 10 μg / ml, 2-20 μg / ml and 1-30 μg / ml. The values ​​of the molar absorption factors were (4.1224 × 104, 3.0229 × 104 and 1.7373 × 104) L mol-1cm-1 with a sensitivity of Sandell’s equal to 0.2606 × 10-4, 0.9834 × 10-4 and 0.2568 × 10 - 4 μg cm-2 to methods A, B respectively and LLOD values ​​were 0.255, 0.553 and 0.158 μg / ml to methods A, B and C. LLOQ 0.512, 0.898 and 0.455 μg / ml to methods A, B, C respectively. The constant fixed Kf configuration was also calculated for the colored outputs of the reaction where it was found to be equal to 43.6435 × 108, 54.6261 × 10-8 and 17.29099 × 106 L2 mol-2 to all methods A, B, C respectively. The values ​​of G were calculated based on -43.9293 KJ / mol, -44.3735 and -51.2019. G values, molar absorption factor, Sandell sensitivity, detection limit.

Three quick and sensitive spectrum methods have been suggested to determine Metronidazole. All spectral methods that were used included reducing Metronidazole by mixing zinc powder with hydrochloric acid. The first method (A) included the process of the conjugation of resorcinol reagent with metronidazole and the production of red chromophores, which was then estimated spectrally at a maximum wavelength of 520 nm. Method–B including the reaction p-chloro benzaldihyde in acidic medium to product yellow color Schiff base has an absorbance at 305 nm. The method C employing a charge transfer reaction with hydroquinone accepter in basic medium to product orange to yellow product absorbed at 335 nm. The best experimental conditions were used by applying the beer's Law for a range of concentrations 2.0-50 μg ml-1, 1.0-35 μg ml-1 and 1.5-30 μg ml-1for methods A, B and C respectively, and the corresponding molar absorptivity values are 1.375×104, 8.672×104, 1.995×104 L mol-1cm-1 with a Correlation coefficient of 0.9996, 0.9998, and 0.9988 and Limits Of Detection (LOD) 0.145 μg ml-1, 0.0776 μg ml-1and 0.110 μg ml-1 and Limits of Quantitation (LOQ) 0.4412 μg ml-1, 0.2352 μg ml-1and 0.3333 μg ml-1 for methods A, B and C Sequentially. The methods were successfully applied to the determination of Metronidazole in pharmaceutical preparation.

Simple and sensitive spectrophotometric method is described for the determination of phenolic compounds in both in pure form and in pharmaceutical preparations. The method is based on the formation of a new ligand from the reaction between 4-aminoantipyrine with phenolic compounds and then reacts with copper (II) to give a colored complex at room temperature. The maximum absorbance of the prepared complexes were measured at 450,500 and 480 nm for pyridoxine, resorcinol and phloroglucinol complexes respectively. Beer’s law was obeyed in the concentration range of 1.5-20, 2.530 and 2.0-25 μg/ml-1, the molar absorptivity values are 2.4778 x 104,1.6740x104 and 1.7001 x 104 L mol−1cm−1, the Sandal sensitivity values are 0.0501x10−3,0.1740x10−3and 0.1228x10−3μg cm−2 for Pyridoxine, resorcinol and phloroglucinol complexes respectively. The correlation coefficients were 0.9999, 0.9998 and 0.9999, the limits of detection(LOD) were 0.47793, 0.15125 and 0.01434μg ml−1, the limits of quantification were (LOQ) 1.4482, 0.45833 and 0.04347 for pyridoxine, resorcinol and phloroglucinol complexes respectively. The stoichiometry of the complexes formed (1:2) was determined by Job’s continuous variations method and molar ratio method. Furthermore the stability constant (K) and Gibbs free energy ΔG) for the complexes were also calculated. The proposed methods were applied successfully for the determination of phenolic compounds in commercial tablets.