Nabil M. Omar

Utility of certain π-acceptors for the spectrophotometric determination of some penicillins

Two simple and sensitive spectrophotometric methods are described for the determination of six penicillin derivatives. The methods are based on the reaction of these drugs as n-electron donors with either 2,3-dichloro-5,6-dicyano-p-benzoquinone (DDQ) or 7,7,8,8-tetracyanoquinodimethane (TCNQ) as pi-acceptors, to give a highly coloured radical anion. The coloured products are quantified spectrophotometrically at 460 and 842 nm for DDQ and TCNQ, respectively. The optimization of the different experimental conditions is described. The interference from streptomycin sulphate and common degradation products was also studied. The proposed methods were applied successfully to the determination of the different penicillins investigated, either in pure or dosage forms, with good accuracy and precision. The results were compared with those given by the official United States Pharmacopeial XXI method.

Spectrodensitometric Analysis of Penicillins by Detection with Iodine

Abstract A rapid, sensitive and selective method is described for the determination of some penicillin derivatives and their additive and degradation products in the presence of each other. Penicillin derivatives are separated from their degradation and additive products on high performance thin layer silica gel G plates. The plates were developed in a linear chamber, air dried, exposed to iodine vapour and measured on a spectrodensitometer at 290 nm. Procaine and procaine penicillin are measured at 360 nm. The results of the analysis show good agreement with the method of the USP XXI. For the reaction of penicillins with iodine, the formation of charge-transfer complexes is considered.

Cyclodextrin Bonded Phase for Liquid Chromatographic Separation and Analysis of Some Oral Contraceptives

Abstract A specific and sensitive analytical HPLC procedure was described for quantitative determination of ethinylestradiol and norethisterone acetate (Anovlar 1) and ethinylestradiol and norgestrel (Primovlar) in tablet formulation. These steroids were extracted from the tablets with methanol. The steroids were then determined with high performance liquid Chromatograph-Cyclobond 1 column using mobile phase phosphate buffer pH 7.0: methanol (60:40), flow rate 0.5 ml min−1 and the detection was effected spectrophotometrically at 280 nm, using variable wavelength UV detector. There was > 99.3% recovery from synthetic mixtures and the coefficient of variation was < 2.0% for the formulations investigated. The method is highly quantitative and reproducible.

Use of Charge-Transfer Complexation in the Spectro-photometric and Spectrodensitometric Analysis of Cephalothin Sodium and Cephradine

Abstract Two rapid and simple spectrophotometric methods as well as a selective and sensitive spectrodensitometric procedure are described for the determination of cephalothin sodium (CT) and cephradine (CD). The spectrophotometric methods are based on the charge-transfer complex formation between these derivatives as n-donors and iodine, the o-acceptor or 2,3-dichloro-5,6-dicyano-p-benzoquinone (DDQ, π-acceptor). The obtained charge-transfer complex with iodine shows two maxima at 295 and 365 nm in 1.2-dichloroethane while it shows a single maximum at 460 nm wih DDQ in methanol. Beers law is obeyed in a concentration range of 2–30 and 2–16 μg/ml with iodine; 10–120 and 30–270 μg/ml with DDQ for CT and CD respectively. In the spectrodensitometric method, cephalosporin derivatives are separated from their degradation or additive products on high performance thin-layer silica gel G plates. The plates were then developed, air dried, exposed to iodine vapour and measured on a spectrodensitometer at 290 and 3...

Synthesis of 3-(1-Methyl-5-nitro-2-benzimidazolyl)acrylic Acid Derivatives as Expected Antischistosomal Agents

Abstract Several ester and amide derivatives of 3-(1-methyl-5-nitro-2-benzimidazolyl)acrylic acid have been prepared for testing as potential antischistosomal agents. The starting acid was conveniently synthesized from the corresponding aldehyde derivative through the Knövenagel-Döbner reaction. The utility of EEDQ as a coupler for the synthesis of peptides has been successfully extended to the coupling of N-heterocyclic acrylic acid derivatives and various amines.