A simple spectrophotometric method is developed for the determination of oxymetazoline hydrochloride (OMCl) as pure and in its pharmaceutical preparations. The method is based on the oxidative coupling reaction of OMCl with 4-aminoantipyrine (4-A.A.P) in the presence of potassium periodate as oxidizing agent in an alkaline medium to produce a coloured water soluble product that is stable and has a maximum absorption at 480 nm. Beer's law is obeyed in a concentration range 20-400µg OMCl/20 ml with a molar absorptivity of 5.34 x 10 3 1.mol-1 .cm-1 , a relative error of-0.50 to-1.47% and a relative standard deviation of ± 0.36 to ± 1.58%, depending on the concentration level. The optimum conditions for full colour development are described and the proposed method was applied successfully to the assay of OMCl in two pharmaceutical preparations.

A simple and accurate spectrophotometric method to assay p-aminobenzoic acid (PABA) has been suggested. The method based on the diazotization of PABA via reaction with nitrite ions which liberated in the medium through the reaction of sodium nitrite with hydrochloric acid, then coupling the dizotised-PABA(D-PABA)with 1-naphthylamine -7-sulphonic acid (1-NASA) to form an intense colored pink azo dye ,it is water-soluble , very stable and has a maximum absorbance at 525 nm. The absorbance was increase with the increasing of PABA amounts in the solution, and the linearity from 2.5 to70 µg in 10 ml (0.25to7 µg.ml-1).The molar absorptivity and Sandell ҆s sensitivity values have been calculated they equal to 3.6057x104 L.mol-1 cm -1 and 0.0037993 µg. cm-2 respectively. The two values above demonstrated a good sensitivity of the suggested method. The method has been used in estimated PABA resulted from analysis of folic acid in tablet.

‫ال‬ ‫ملخص‬ ‫لت‬ ‫طيفية‬ ‫يقة‬ ‫طر‬ ‫البحث‬ ‫يتضمن‬ ‫قدير‬ ‫اسيتامول‬ ‫البار‬ ‫من‬ ‫الصغر‬ ‫في‬ ‫متناهيه‬ ‫كميات‬ . ‫تعتمد‬ ‫أزوتة‬ ‫عمى‬ ‫يقة‬ ‫الطر‬ ‫ا‬ ‫بار‬ -‫بمفاعمته‬ ‫وذلك‬ ‫اسيتامول‬ ‫لمبار‬ ‫الحامضي‬ ‫التحمل‬ ‫من‬ ‫الناتج‬ ‫فينول‬ ‫امينو‬ ‫يك‬ ‫الهيدروكمور‬ ‫حامض‬ ‫بوجود‬ ‫يت‬ ‫النتر‬ ‫ايون‬ ‫مع‬ ‫ان‬ ‫اقتر‬ ‫ثم‬ ‫قاعدي‬ ‫وسط‬ ‫في‬ ‫الناتج‬ ‫الدايازونيوم‬ ‫ممح‬ ‫مع‬ ‫ان‬ ‫االقتر‬ ‫كاشف‬ ‫اسيتوفي‬ ‫فمورو‬ ‫نون‬ ‫صبغة‬ ‫لتكوين‬ ‫آزوية‬ ‫الماء‬ ‫في‬ ‫وذائبة‬ ‫ة‬ ‫مستقر‬ ‫تقالية‬ ‫بر‬ ‫و‬ ‫تم‬ ‫ل‬ ‫االمتصاص‬ ‫شدة‬ ‫قياس‬ ‫لصبغة‬ ‫الناتجة‬ ‫الموجي‬ ‫الطول‬ ‫عند‬ 472 ‫نانوميتر‬ ‫وكانت‬ ‫حدود‬ ‫قانون‬ ‫التركيز‬ ‫مدى‬ ‫في‬ ‫بير‬ ‫من‬ 10 ‫إلى‬ 180 ‫ام‬ ‫مايكروغر‬ ‫ـ‬ ‫ال‬ ‫من‬ ‫اسيتامول‬ ‫بار‬ / 25 ‫مل‬ ‫قيمة‬ ‫وكانت‬ ‫ية‬ ‫الر‬ ‫المو‬ ‫االمتصاصية‬ ‫هي‬ 2.16  10 4 ‫لتر‬ . ‫م‬ ‫ول‬ -1 . ‫سم‬ -1 ‫النسبي‬ ‫الخطأ‬ ‫و‬ ، ‫اوح‬ ‫تر‬ ‫بين‬ -0.64 ‫و‬ +1.64 % ‫بين‬ ‫النسبي‬ ‫القياسي‬ ‫اف‬ ‫االنحر‬ ‫و‬  0.4 ‫و‬ 1.24 % ‫اعتمادا‬ ‫عمى‬ ‫تركيز‬ ‫مستوى‬ ‫ـ‬ ‫ال‬ ‫اسيتامول‬ ‫بار‬ . ‫تقدير‬ ‫في‬ ‫بنجاح‬ ‫يقة‬ ‫الطر‬ ‫تطبيق‬ ‫تم‬ ‫ـ‬ ‫ال‬ ‫اسيتامول‬ ‫بار‬ ‫في‬ ‫ات‬ ‫المستحضر‬ ‫الصيدالني‬ ‫ة‬ . ABSTRACTA spectrophotometric method for the assay of micro amounts of paracetamol has been developed. The method is based on the reaction of p-aminophenol which results from the acid hydrolysis of paracetamol, with nitrite ion to form the corresponding diazonium salt followed by coupling reaction in an alkaline medium with phloroacetophenone to form a stable and soluble orange azo dye. The intensity of absorbance for the resulting azo dye is measured at 472 nm and Beer's law is obeyed in the concentration range of 10-180 g of paracetamol in a final volume of 25 ml, with a molar absorptivity of 2.1610 4 l.mol -1 .cm -1 , a relative error of -0.64 to +1.64% and a relative standard deviation of 0.4 to 1.24 %, depending on the concentration level of paracetamol. The method has been successfully applied to the assay of paracetamol in various pharmaceutical preparations.