Propyl parabens

A mixture of methyl paraben, ethyl paraben, propyl paraben, diethyl phthalate, and butyl paraben is separated by HPLC. This experiment emphasizes the development of a mobile-phase composition capable of separating the mixture. A photodiode array detector demonstrates the coelution of the two compounds. 

Brononol (2-Bromo-2-nitropropane-1,3-diol) in combination with methyl and propyl paraben. The paper generated by the Danish group (ref. 5 Knoll BASF publication) shows that the mechanism of action of Bronopol is independent of formaldehyde formation. The inclusion of Tetrasodium EDTA at about 0.02% to remove ions in the water or extracts and carefully excluding any tertiary amines such as triethanolamine to counteract the fears of the marketers with reference to possible nitrosamine formation and release of formaldehyde. The pH used is usually at 6 and below. 

FIGURE 6.17 Chromatogram overlay for 24 consecutive runs performed on a single column. (A) results of overlay for the chromatograms obtained with UV absorbance detection. Peaks are identified as (with increasing retention time) uracil (dead volume marker), methyl paraben, and propyl paraben. (B) results of overlay for chromatograms obtained from fluorescence detection (peak identified as rhodamine 110 chloride). 

FIGURE 6.19 Magnified view of overlay of two chromatograms obtained during consecutive injections of a propyl paraben solution followed by injection of CH3CN H20 (50 50) solution. 

As shown in Figure 6.21, excellent linearity was obtained, as represented by the high coefficient of correlation obtained for the least square linear regression. Similar results were obtained for the evaluation of autosampler accuracy when other analytes (propyl paraben and rhodamine 110 chloride) were employed in the determinations. Liu et al.9 conducted similar evaluations for the samples employed in the evaluation of the drug release rate profile of OROS with similar results to those discussed above. 

Calculate the selectivity for propyl paraben compared to methyl paraben given the following data ... 

The capacity factor for methyl paraben is 2.7. The capacity factor for propyl paraben is 4.9. 

Charge 240 mL of water into a separate container and heat to boiling. Add and dissolve methyl and propyl parabens. Mix until complete solution. Add this solution to step 1 solution. 

Mix with solution of items 7 to 11 and add item 12 to make up the volume. Parabens are generally a 1 10 ratio of methyl and propyl paraben. 

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