SIMULTANEOUS DETERMINATION OF CARBIDOPA AND LEVODOPA USING A NEW TLC METHOD AND A FREE RADICAL AS DETECTION REAGENT

Abstract

A new thin-layer chromatographic (TLC) method was applied for the simultaneous analysis of two catechol related compounds (carbidopa and levodopa) using the DPPH free radical as detection reagent and digital image processing for the determination of the compounds on the chromatographic plate. The BioDit Thin Layer Chromatography (TLC) Scanner device and advanced specific software (ImageDecipher-TLC, Sorbfil TLC Videodensitometer and Just TLC) were used for the detection and quantification of chromatographic spots. The raw colored images of the chromatographic plates were imported directly from the scanner and for an accurate determination they were inverted and processed after their conversion into green scale. The results showed a strongly linear correlation between area (R² > 0.9969) and respectively volume (R² > 0.9956) of spots and concentration of investigated compounds in all cases. The linearity of the analytical procedure was in range of 50–300 ng/spot for both carbidopa and levodopa. The limit of detection (LOD) and the limit of quantification (LOQ) were below 53.4 ng/spot and 61.1 ng/spot, respectively, in all cases. The validation of the method was also performed using commercial pharmaceutical tablets containing carbidopa and levodopa as active compounds.

Keywords:

• carbidopa
• digital image processing
• DPPH free radical
• levodopa
• method validation
• TLC

ACKNOWLEDGMENT

This work was possible with the financial support of the Sectorial Operational Program for Human Resources Development 2007–2013, cofinanced by the European Social Fund, under the project number POSDRU 89/1.5/S/60189 with the title “Postdoctoral Programs for Sustainable Development in a Knowledge Based Society” and PN-II-ID-PCE-2011-3-0366 project.

Notes

(I)– ImageDecipher-TLC.

(II) – Sorbfil TLC.

(III) – JustTLC.

(I) – ImageDecipher-TLC.

(II) – Sorbfil TLC.

(III)– JustTLC.

*Data represent the mean of 3 identical samples, each of them applied on 3 replicate spots ± SD.

(I) – ImageDecipher-TLC.

(II) – Sorbfil TLC.

(III) – JustTLC.