Phenylephrine is a medication mainly applied as a decongestant to relieve hemorrhoids, increase blood pressure, and dilate the pupil. It is the first-line choice for prevention and treatment of hypotension during spinal anesthesia for cesarean section. However, many methods were used for the determination of this drug and its properties. This paper proposes a method that uses N, N dimethyl-p-phenylenediamine dihydrochloride as a new chromogenic reagent (NNDPH). This method is based on the oxidative coupling reaction of phenylephrine with N, N dimethyl-p-phenylenediamine dihydrochloride with ferric chloride in basic media to form green-blue soluble dye product. The outcomes demonstrate that the maximum absorption is at 680 nm, molar absorptivity of 5.54 × 103 mol-1.cm-1, and Sandell’s sensitivity of 0.038 μg.cm-2. The concentration range of 4 to 22 μg.mL-1 of the product is conformable to Beer’s law. Furthermore, it is applied successfully for estimating the drug properties on a simple condition or pharmaceutical preparations.

A simple, accurate, and sensitive method for the spectrophotometric determination of Chloramphenicol (CAP) in pharmaceutical preparations. The method is based on the oxidative coupling reaction of Chloramphenicol after reducing the nitro group in the drug into an amino group with Naphthalene-1,5-diamine as a reagent in the presence of potassium Iodate as an oxidizing agent formed violet dye that is soluble in water and have a maximum absorption at 568nm. Beer's law is obeyed in the concentration range of 6-27㎍.mL-1 with a molar absorptivity of 0.4805×104 L.mol-1.cm-1, and Sandell's sensitivity was 0.061㎍.cm-2, respectively. The correlation coefficient was 0.9994, with recovery average % was 100.05. Detection limit (D.L) and quantitative limit (Q.L) were 0.241㎍.ml- 1 and 0.804 ㎍.ml -1. The product was stable for 70 minutes with relative error (RE) % of -0.12 to -0.22 and a relative standard deviation (RSD) % of 0.476 to 0.362. The method was successfully applied to the analysis of Chloramphenicol in pharmaceutical preparations (Eye drop).

Oxidative coupling reactions are one of the significant methods used in the estimation of certain drugs in pharmaceutical formulations. This study describes the development of a fast and sensitive spectroscopic method considering the determination of trace amounts of methyldopa in an acidic aqueous solution. The adopted method centered on oxidative coupling due to the drug Methyldopa with the reagent 1, 5-diaminonaphthalene in the presence of ceric (IV) ammonium nitrate as oxidizing agent to form a stable blue-colored product, giving the highest absorption at 730 nm. The product was appeared to agree Beer's law within the limits of (5.4 -39.6) µg /ml, and a value of molar absorptivity equal to 4.79471×10 4 L/mol.cm.Sandell ′ sindex, 0.0044µg/ cm 2 , Relative standard deviation was in the range (0.5942 -0.9687)%, whereas recovery average and determination factor were 99.908% and 0.9998. The proposed method has been successfully applied in the determination of Methyldopa in its pharmaceutical preparations.

A simple, rapid and sensitive spectrophotometric method was described for the determination of Furosemide (FUR). The method is based on the oxidative coupling reaction between Furosemide and 1-Naphthylamine-4-sulfonic acid in the presence of potassium permanganate to form a yellow colored product with maximum absorptions at 465nm, which is soluble in water. Beer's law is obeyed in the concentration range of 3 to 23㎍.ml-1 with a molar absorptivity of 1.065×104 L.mol-1.cm-1, and Sandell's sensitivity of 0.0310㎍.cm-2, respectively. The correlation coefficient of 0.9994, with recovery average % of 99.948. Limit of detection (LOD), limit of quantification (LOQ) of 0.971㎍.ml- 1 and 3.237 ㎍.ml -1 and a relative standard deviation (RSD) % of 0.641 to 0.812. The proposed method has been used to successfully determine furosemide in pharmaceutical formulations (Tablet).

A simple, rapid and sensitive spectrophotometric method for determination of Lisinopril (LS) in both pure form and pharmaceutical preparations has been reported. The adapted technique based on utilization 4-aminonaphthalene-1-sulfonic acid as a Chromogenic reagent through an oxidative coupling reaction with Lisinopril and Potassium Peroxydisulfate (oxidation agent) in acidic medium to form green dye soluble product absorption maxima at 612 nm. Linearity was in the range 2–43 μg ml-1. The values of molar absorption coefficient (ε), correlation coefficient and Sandel’s index were found to be 10.3808 × 103 L. mole-1 cm-1, 0.9995 and 0.00343 µg.cm-2 respectively. The average of recovery % was 100.067. Detection Limit and quantitative limit were 0.0343 µg/ml and 0.1143 µg/ml. The proposed method has been successfully applied in the determination of preparations containing lisinopril.