Quantitative determination of methanol and propanol-2 in tinctures and extracts using head-space gas chromatography in comparison with method of vaporization of liquid in GC inlet
Keywords:methanol, propanol-2, volatile impurities, gas chromatography, gas-liquid chromatography, sensitivity
The aim of this work was to compare sensitivity of methods for determination of methanol and propanol-2 contents in tinctures and extracts.
Materials and methods. Two methods suggested in the State Pharmacopoeia of Ukraine for determination of the above mentioned compounds in liquid medicines were used, specifically: head-space gas-chromatography (method A) and classic gas chromatography (method B) with common injection technique.
The research was conducted on one of the most popular medicinal products based on ethanol extracts of herbal drugs: echinacea (Tinctura Echinaceae), hawthorn (Tinctura Crataegi), and motherwort tinctures (Tinctura Leonuri). All medicines used were manufactured at pharmaceutical factory “VIOLA” (Zaporizhzhia, Ukraine). Substance analysis was held on gas chromatograph Agilent 7890B (USA) coupled to head – space sampler DANI HSS 86.50 Plus (Italy). Compounds were separated on J&W Agilent DB-624 (USA) column.
In the study quantitative contents of methanol and propanol-2 were evaluated in tinctures and extracts using methods of head – space gas chromatography and liquid evaporation in the GC inlet (common injection technique), sensitivities of both methods were compared due to signal-to-noise levels. Statistical parameters of the obtained results were assessed (average, error, variance).
Results. The results demonstrated that methanol and propanol-2 contents in tinctures did not exceed the limit value, which is set to 0.05 %. However, it was showed that classic gas chromatography is not able to give information about amounts of propanol-2 in substances, while head-space chromatography has determined concentration of this compound in all examined tinctures. It was determined that head-space GC has higher signal-to-noise levels.
Conclusions. Considering all shown results and their discussion, it was concluded that method of head – space GC is more sensitive for determination of volatile impurities in liquid medicinal products than classic gas chromatography with common injection technique.
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