Determination of Organic Impurities in Anthraquinone Color Additives D&C Violet No. 2 and D&C Green No. 6 by Ultra-High Performance Liquid Chromatography

Determination of Seven Organic Impurities in FD&C Yellow No. 6 by Ultra-High-Performance Liquid Chromatography

BACKGROUND

The U.S. Food and Drug Administration (FDA) batch certifies FD&C Yellow No. 6 (Y6) to ensure that the color additive meets requirements published in the Code of Federal Regulations (CFR), including specifications for seven organic manufacturing impurities consisting of two intermediates, a reaction by-product, an impurity originating from an intermediate, and three subsidiary colors.

OBJECTIVE

An ultra-high-performance liquid chromatography (UHPLC) method was developed and validated for determining seven organic impurities in Y6. For comparison, the currently used high-performance liquid chromatography (HPLC) method was also validated.

METHODS

The new UHPLC method uses a 1.7 µm particle size biphenyl column with aqueous ammonium formate and methanol as eluants. Analytes are identified by comparing their retention times and UV-visible spectra to those of reference standards. Calibration is performed in the presence of the dye matrix and analyte levels are determined from their peak areas.

RESULTS

UHPLC and HPLC validation studies obtained linear calibration curves and excellent values for limits of detection, limits of quantitation, recovery, repeatability, and intermediate precision for all analytes. Survey analyses of 30 samples using the UHPLC and HPLC methods yielded results that were consistent within experimental error; however, the UHPLC method provided more accurate results for two analytes that coelute using the HPLC method.

CONCLUSION

The UHPLC method satisfies the accuracy and precision requisites for routine certification of Y6.

HIGHLIGHTS

The UHPLC method is faster and generates less waste than the HPLC method while delivering better sensitivity, separation, and accuracy.

Determination of fluorescein and brominated fluoresceins in the color additive D&C Orange No. 5 and its lakes using high-performance liquid chromatography

The colour additives D&C Orange No. 5 (O5) and its lakes (O5L) are subject to batch certification by the U.S. Food and Drug Administration (FDA) to ensure compliance with specifications in the Code of Federal Regulations (CFR). The present study reports the development of a high-performance liquid chromatography (HPLC) method for the quantitative determination of seven CFR-specified components in O5 and O5L - fluorescein and six brominated fluoresceins. The analytes were quantified using six-point calibration curves with data points (w/w) that ranged as follows: 20.0-70.0% for 4',5'-dibromofluorescein; 9.8-44.1% for 2',4',5'-tribromofluorescein; 1.01-15.2% for 2',4',5',7'-tetrabromofluorescein; 0.10-3.12% for 2',4'-dibromofluorescein; 0.10-3.06% for 2',5'-dibromofluorescein; 0.11-2.85% for 4'-bromofluorescein; and 0.10-2.02% for fluorescein. For all seven analytes, the HPLC instrument response was linear (R² > 0.999) over the tested concentration ranges and the limits of detection (0.01-1.55%) were well below the CFR-specified levels. Other validation data showed good analyte recovery (87.91-101.73%) as well as method precision measured by the relative standard deviation (0.53-1.56%). The new method was applied to the analysis of test portions from 15 batches of O5 and eight batches of O5L submitted to FDA for certification by domestic and foreign manufacturers. Compared to the thin-layer chromatography/spectrophotometric procedure currently used for routine batch-certification analyses, the new method was found to be more sensitive, simpler to implement, and significantly faster, requiring 25 minutes rather than six hours to analyse one sample.