High Sensitivity Analysis of 12 Synthetic Food Colorants by U-HPLC with Diode Array Detection

The natural colors of the food we eat add greatly to the enjoyment of life. Consequently, the art and science of recreating food's natural colors through the use of synthetic colorants is an important success factor in the food industry.

Table I: Gradient Program

Synthetic colorants are used widely because their coloring ability is more intense than most colors derived from natural products and can often be added to foods in smaller quantities. In addition, synthetic colorants are more stable, provide better color uniformity and blend together easily to provide a wide range of hues.

Figure 1

However, some colorants pose a potential risk to human health, especially if they are consumed in excess. For this reason, safety data based on toxicological studies have been repeatedly determined and evaluated by the Food and Drug Administration (FDA) and World Health Organization (WHO). This paper describes an accurate, linear, and sensitive method for the measurement of 12 synthetic food colorants using the Hitachi LaChromUltra™ U-HPLC system with diode array detection.

Experimental Conditions

Sample: 1 μL of std. soln. (0.5 to 50 mg/L each) dissolved in deionized water

Column: HITACHI LaChromUltra C18 (2μm); 2.0 mm I.D. × 50 mm L

Column Temp: 40°C

System Pressure: 34.5 MPa

Mobile phase:

(A) 10 mmol/L Ammonium Acetate / Acetonitrile = 95 / 5

(B) 10 mmol/L Ammonium Acetate / Acetonitrile = 1/ 1

Compounds:

Y4: Tartazine

R2: Amaranth

B2: Indigo Carmine

R102: New Coccine

Y5: Sunset Yellow FCF

R40: Allura Red AC

G3: Fast Green FCF

B1: Bullient Blue FCF

R3: Erythosine

R106: Acid Red

R104: Phloxine

R105:Rose Bengal

Results

Calibration curves consisting of four standards (0.5, 5.0, 10 and 50 ppm) were obtained for each compound with an average r² = 1.000. Excellent separation of all compounds was achieved in <3.5 min on the LaChromUltra U-HPLC and diode array detection provided the added benefit of secondary confirmation through spectral identification.

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