Reversed-phase LC determination of two manufacturing intermediates, the unsulfonated subsidiary color, and 4-methyl-Sudan I in D&C Red No. 6, D&C Red No. 7, and their lakes.
A reversed-phase liquid chromatographic (LC) method was developed to determine 4 impurities in the monosulfo monoazo color additives D&C Red No. 6, D&C Red No. 7, and their lakes. Manufacturing intermediates determined are 2-amino-5-methylbenzenesulfonic acid (PTMS) and 3-hydroxy-2-naphthalenecarboxylic acid (3-hydroxy-2-naphthoic acid). Subsidiary colors determined are the unsulfonated and uncarboxylated, unsulfonated homologs of the dye (the unsulfonated subsidiary color and 4-methyl-Sudan I). The new method uses lithium oxalate as part of a novel system to dissolve the water-insoluble color additives. The 4 impurities were identified by LC and UV-visible spectrophotometry; the 4-methyl-Sudan I was confirmed by LC/mass spectrometry. LC peak area calibrations were generally linear (R > 0.999), and recoveries ranged from 90 to 105%. The limits of determination used were 0.02% each for PTMS and 3-hydroxy-2-naphthoic acid, 0.1% for the unsulfonated subsidiary color, and 0.002% for 4-methyl-Sudan I. The relative standard deviations at the specification levels ranged from 0.7 to 22.7%. Survey analyses of 26 samples of certified D&C Red Nos. 6 and 7 straight colors and lakes from 11 domestic and foreign manufacturers yielded results that agree with those previously obtained using 3 other methods.
Harp
Bhakti Petigara
BP
U.S. Food and Drug Administration, Center for Food Safety and Applied Nutrition, Office of Cosmetics and Colors, 5100 Paint Branch Parkway, College Park, MD 20740, USA. bhakti.petigara@fda.hhs.gov
Scher
Alan L
AL
Yang
Huei-Hsuan W
HH
Brodie
Darlene L
DL
Sullivan
Michael P
MP
Barrows
Julie N
JN
D002853:Chromatography, Liquid / Q000379:methods*; D004340:Drug Contamination; D005505:Food Coloring Agents / Q000032:analysis*
D005505:Food Coloring Agents