Saad A. Al-Tamrah

Flow injection chemiluminescence determination of sulphite

A comparison is made of the use of riboflavin and 3-cyclohexylaminopropanesulphonic acid (CAPS) to increase the sensitivity of the determination of sulphite in a flow injection procedure based on the chemiluminescence produced by permanganate oxidation in an acidic solution. Both procedures give linear calibration graphs for 5–60 ng of sulphite, but the CAPS procedure has a lower detection limit (1.2 ng) and better relative standard deviation (RSD)(2.5% for 40 ng, n=10). Riboflavin enhancement arises from energy transfer, but the reason for the CAPS enhancement could not be identified with certainty.

Determination of naphthols by flow-injection chemiluminescence

Abstract 1-Naphthol, 2-naphthol, 2-naphthol-6-sulphonic acid, 1-amino-2-naphthol-4-sulphonic acid and 1-amino-2-naphthol hydrochloride are determined by the chemiluminescence produced by acidic permanganate oxidation in a flow system. Rhodamine B is used as sensitizer. The limits of detection are ca. 5×10 −7 M in a 20-μ sample.

Use of cerium(IV) sulphate in the spectrophotometric determination of paracetamol in pharmaceutical preparations

An accurate spectrophotometric method is proposed for the determination of paracetamol. Cerium(IV) sulphate is used to oxidise paracetamol in 5 M H2SO4 to p-benzoquinone, which is then determined at 410 nm. The method has been successfully applied to the analysis of commercial pharmaceutical preparations and the results have been statistically compared with those obtained by the official (BP) method.

Spectrophotometric determination of oxytetracycline by flow injection

A flow injection spectrophotometric method is proposed for the determination of oxytetracycline. The method is based on the reaction of this drug with iron(III) in the presence of sulphuric acid to form a coloured complex. Less than 10 µg ml–1 of the drug (defined as the amount of the drug that gave a signal of twice the background noise) can be determined by measuring the absorbance at 435 nm of the complex formed. Parameters affecting the absorbance such as the acid concentration, sample volume and the reaction coil length were all studied in order to optimize them. The method was applied to the determination of oxytetracycline in real samples and some pharmaceutical preparations. The relative standard deviation was 1.7% for 80 µg ml–1(for ten replicate injections). The sample throughput is 17 samples h–1. The effect of some foreign species was also investigated.

Flow-injection determination of kanamycin by inhibition of the lucigenin—H2O2Co2+ system

Abstract The application of lucigenin chemiluminescence for the determination of trace concentrations of kanamycin is described. The method is based on the inhibiting effect that kanamycin has on the reaction of lucigenin and hydrogen peroxide in a basic solution. The effect of the concentrations of the reagents was studied and the reaction conditions are discussed. The proposed method allows the determination of kanamycin in the range of 1 × 10 −13 to 1 × 10 −5 M with a relative standard deviation of ca. 1.91%. The method is relatively free from the interference of common excipients accompanying the drug in pharmaceutical samples. The results obtained for the assay of commercial preparations compared well with those obtained by another known method and showed good accuracy and precision.

Determination of promethazine by its inhibition of the chemiluminescence of the luminol—hydrogen peroxide—chromium(III) system

Abstract The luminolH 2 O 2 metal ion system has been widely used in chemical and biological analysis. A method is described for the determination of promethazine based on its inhibition of the intensity of chemiluminescence from the luminol system. The method is sensitive, convenient and simple with a detection limit of 3 × 10 −9 M. The R.S.D. at 1 × 10 −5 M promethazine is 1.3% (ten replicates). The method was applied successfully to the analysis of various commercially available dosage forms containing promethazine. The results obtained for the assay of commercial preparations compared well with those obtained by the official method and showed good accuracy and precision.

Determination of (S)(-)-cathinone by spectrophotometric detection.

Previous studies on the Khat plant (Catha edulis, Celastraceae) illustrated the importance of using freshly harvested young shoots and leaves such that cathinone, the principle active component and Schedule I controlled drug contained within the plant, could be suitably isolated and identified. The purpose of this work was to develop a quantitative analytical technique for the determination of cathinone. The proposed method is based on treating the reductant cathinone with copper(II)-neocuproine reagent in sodium acetate-buffered medium followed by measuring the absorbance of the copper(I)-neocuproine complex at 455 nm. The calibration plot is linear in the range 0.08-25 micrograms ml-1 with a detection limit of 0.08 microgram ml-1. The precision of the method, expressed as the relative standard deviation, is 1.35% for 10 micrograms ml-1 cathinone. Good recoveries have been obtained in applying the method to the analysis of cathinone in Khat leaves.

Determination of some tetracyclines spectrophotometrically by flow injection analysis

Abstract A spectrophotometric method for the determination of some tetracyclines is described. The suggested method is based on the reaction of the drug with sodium tungstate at pH 6 to form a yellow complex which can be determined spec trophotometrically. The complexes show absorption maxima at 380, 3385 and 390 nm for oxytetracycline hydrochloride(OTCH), doxycycline hydrochloride(DCH) and chlortetracycline hydro-chloride(CTCH), respectively. These drugs can be determined either in pure form or in pharmaceutical preparations.

Determination of selenium content in dates of some cultivars grown in Saudi Arabia

The concentrations of selenium in the flesh of ten date cultivars collected from different regions of Saudi Arabia were analysed using an ultraviolet/ visible spectrophotometer. The amount of selenium was found to be in the range between 1.48 and 2.96 μg/g in the ten varieties studied. The cultivar Sillaj from Al-Kharj (south-west region of Saudi Arabia) was found to contain the highest concentration of selenium (2.96 μg/g). The lowest content of selenium (1.48 μg/g) was observed in the cultivar Muneef from Riyadh region. The content of selenium in dates was compared with data for selenium content of other fruits, nuts and vegetables.

Determination of free fatty acids in olive oils by UPHLC-MS.

A simple, fast, highly efficient and direct method using ultra-performance liquid chromatography coupled to mass spectrometry has been established for the simultaneous separation, identification and quantitation of a few saturated and unsaturated fatty acids in olive oils from various countries. No sample pretreatment techniques were employed such as extraction or derivatization for the analysis of target acids from oil samples, as the oil samples were just diluted, filtered and then directly injected to the instrument. The chromatographic separations of all target fatty acids were achieved on a Hypersil Gold C18 column of particle size 1.9μm, 50×2.1mm I.D, while the gradient elution using a binary mobile phase mixture of acetonitrile and water at a flow rate of 1.5ml/min was adopted for achieving optimum separations. The identification and quantitation of target compounds was accomplished using selected ion reaction monitoring mode. The recoveries of the fatty acids were obtained higher than 89% with good validation parameters; linearity (r(2)>0.992), detection limit between 0.09 and 0.24μg/ml, run to run and day to day precisions with percent relative standard deviation lower than 2.4% at both low (1μg/ml) and medium (10μg/ml) concentration levels. The total content of fatty acids in each individual oils was found in the range of 472.63-7751.20μg/ml of olive oil, while oleic acid was found to be the major fatty acid among all analyzed oils with the amount 3785.94μg/ml (maximum) in Syrian olive oil. The obtained validation parameters confirm that the proposed analytical method is rapid, sensitive, reproducible and simple and it could be applied for the successful evaluation of fatty acids in various oils and other matrices. All the fatty acids were efficiently eluted in a time of less than 8min with well resolved peaks by employing the proposed method.