316 Fresenius Z. Anal. Chem., Band 287 (1977)

Fresenius Z. Anal. Chem. 287, 316 (1977) - �9 by Springer-Verlag 1977

Separation of Hydroxyurea Derivatives with High-Pressure Liquid Chromatography

B. Makuch*, B. Sledzifiska, and W. Sokotowska

Department of Chemical Engineering and Measuring Techniques, Technical University of Gdarlsk, PL-80-952 Gdafisk, Poland

Trennung yon Hydroxyharnstoffderivaten dutch Hochdruck-Fliissigkeits-Chromatographie

Key words: Trenn. yon Hydroxyharnstoffderivat~n; Chroma- tographie, Sfiulen; Hochdruck.

An analytical method was required for the investigation of tech- nical N-3,4-dichlorophenyl-N'-hydroxyurea, which is usually accompanied by other hydroxyurea derivatives (see below). It has been found that thin-layer chromatographic techniques are not satisfactory as they are time-consuming and their results are scarcely reproducible. High-pressure liquid chromatography, however, proved to be most suitable. After testing several ma- terials, it was obvious that best results are obtained by using Corasil II as the stationary phase and hexane/dioxane (85/15) as the mobile phase. The technical product was in this way sep- arated into six components. Peaks were identified as far as possible by comparing their retention volumes with those of standard substances (see Fig. 1). When using the above urea de- rivative as test substance the hight equivalent of the theoretical plate (HETP) was only 0.16 cm. The time required for an analysis was only 45 min. The determinations were carried out by the external calibration method. The error was + 4 % for the above compound. The following contents of the main compo- nent were found in different technical preparations: solvent

* Address for correspondence

6

~2 A J

i I I I

/.5,5 rain.

Fig. 1. Separation of the technical product 3,4-dichlo- rophenyl-N'-hydroxyurea. 1 unknown; 2 3,4-dichloroaniline; 3 unknown; 4 N,N-di(3,4-dichlorophenyl)urea; 5 N,N"- di(3,4-dichlorophenyl)-N-hydroxybiuret; 6 N-3,3-dichlo- rophenyl-N'-hydroxyurea

paste 70.2%, dry product A 97.4%, dry product B 86, dry product C 87.9%.

Experimental

q-he instrument used in the study was a liquid chromatographic apparatus made at the Institute of Chemical University of Gdafisk. It was equipped with an UV 254 nm detector with an 8 ~1 measuring cell, a sensitivity index of A 0.01 abs. u. for the full scale, and an acid resistant steel column of 2.0 mm interior diameter and 50 cm length.

Stationary and mobile phases as mentioned above. Flow rate: 0.5 ml/min. Pressure applied: 100 psi.

Received March 3, 1977; revised April 18, 1977

Fresenius Z. Anal. Chem. 287, 316 (1977)- �9 by Springer-Verlag 1977

Improvement of the lodometric Determination of Cysteine

Ashutosh Srivastava

Department of Chemistry, University of Jabalpur, 171 Bhaldarpura, Jabalpur 482002, India

Verbesserung der jodometrischen Cysteinbestimmung

Key words: Best. von Cystein; Volumetrie, Jodometrie; Ver- besserung

In the present work the effect of acid and of iodide concentra- tion on the reaction between eysteine and iodine, was studied. It was noted that when cysteine was titrated in 1 M hydrochloric acid in presence of 1 M solution of potassium iodide the results

were erratic. On raising the iodide ion concentration the titre value agrees with the theoretical one but the end-points are fleeting. On increasing acid concentration the latter difficulty was circumvented. The ideal situation thus evolved is reported.

Procedure. A sample containing 0.5-2.0 mmole of cysteine was dissolved in 10 ml of distilled water and 1 ml of 2 N hydro- chloric acid was added to it along with 1 ml of 1% starch solu- tion. This reaction mixture was then titrated with 0.05 N iodine solution prepared in 1 M potassium iodide. The end point was noticed by the blue colour of starch iodine formed with the first excess drop of iodine.

Under the described conditions of titration a series of 10determinations furnished recoveries that ranged from 99-101% of the theoretical with a relative standard deviation of _+0.4%.

Received May 6, 1977