Resolve the Separation Issue of 11 Synthetic Colorants
Colorants, also known as food dyes, are substances primarily used to color food and improve its appearance. Currently, there are more than 60 commonly used food colorants worldwide, which can be categorized into synthetic food colorants and natural food colorants based on their origin and properties. As awareness of food additive safety increases, there is a strong trend towards developing natural, nutritious, and multifunctional colorants, marking the future direction for food colorants.
The new standards have added four synthetic colorants: indigo, allura red, acid red, and quinoline yellow.
Recently, a customer encountered a common issue when testing these four synthetic colorants:
At a wavelength of 415 nm, acid red interferes with the peak of quinoline yellow, affecting the quantification of quinoline yellow. In response to this issue, Welch Laboratory conducted experiments and identified a chromatography column that allows accurate quantification without interference between the components.
Chromatographic Conditions
Column: Welch Xtimate® C18 (4.6×250 mm, 5 μm)
Mobile Phase:
- A: Ammonium acetate solution (20 mmol/L)
- B: Methanol
Gradient Elution Program:
| Time (min) | A (%) | B (%) |
| 0 | 90 | 10 |
| 12 | 60 | 40 |
| 19 | 50 | 50 |
| 22.5 | 45 | 55 |
| 24 | 5 | 95 |
| 33 | 5 | 95 |
| 34 | 90 | 10 |
| 42 | 90 | 10 |
Flow rate: 1.0mL/min
Column temperature: 30℃
Detector: 400-800nm
Injection volume: 10μL
Spectra and data
Summary
According to the Chinese National Food Safety Standard GB 5009.35-2023, the Welch Xtimate® C18 (4.6×250 mm, 5 μm) column was used to determine 11 colorants. The separation between acid red and quinoline yellow achieved a resolution of over 1.8. The resolution between other components was over 1.6 with no interference. The column also demonstrated good stability and longevity, meeting the testing requirements.
| 00577-20043 | Solid Phase Extraction Column |
Welchrom® PWAX Weak Anion Exchange Extraction Column 150mg/6mL |