Quantitative determination of glycine in pharmaceutical formulations by reaction with 2,3-dichlor-1,4-naphthoquinone reagent

Abstract

Glycine has been reported to be determined by different techniques including titrimetric methods, VIS spectrophotometry. Some of the proposed methods require inaccessible reagents, others – difficult in execution or offered only for substances. That is why, feasibility of developing new, simple, valid methods for the glycine quantitative determination in medical forms is not in doubt.
 This paper presents a new, simple and accurate VIS spectrophotometric method for determining of glycine in pharmaceutical formulation using 2,3-dichlor-1,4-naphthoquinone as a reagent.
 Pharmaceutical preparations: capsules of Doppel Herz, 0,50 g (Queisser Pharma Gmbh & Co, Germany); powder in packets Medichronalum-Darnitsa, 7,00 g (Pharmaceutical company «Darnitsa», Ukraine); tablets of Glycin («Biotiki», Russia).and Glicised («Arterium», Ukraine), 0,10 g.
 Analytical balance (ABT-120-5DM); UV-VIS spectrophotometer (Specord 200); water bath (Memmert WNB 7-45).
 The aliquot part (0,1200‒0,2000 g) of the glycine is put into a 25,00 ml volumetric flask, add 7,00 ml water and filled to the mark with DMF. The amount of 1,00 ml of the resulted solution is poured into a 25,00 ml volumetric flask, then treated with 2,50 ml of 1% solution of the 2,3-dichlor-1,4-naphthoquinone and mixed up. A received solution is heated up for 15 minutes on the water-bath under temperature of 95 °С, then is cooled down and filled to the mark with the DMF. Absorbance of the test solution is measured at 470 nm against the background of the compensation solution that does not contain any test solution.
 Defined minimum calculated by common method is 3,20 mcg/ml.
 Experimentally determined glycine optimal reaction conditions with the 2,3-dichlor-1,4-naphthoquinone as the basis for the development of spectrophotometric methods for glycine quantitative determination in the 4 drug dosage forms.
 The analytical method was optimized and validated by establishing the linearity (in the range of 5,00‒8,00 mg/100 ml), the correlation coefficient (r = 1,000), precision and the accuracy.
 Thus, the peculiarity of the developed method consists in it’s enhanced sensitivity in comparison with other available methods of quantitative determination. The developed method is simple and useful for routine analysis of glycine in pharmaceutical formulations and in-process quality control.