8 Synthetic Food Colorants in Milk Tea (Copure® PWAX Cartridges)

Introduction

Synthetic food colorants are widely used in the food industry forenhancing color and sensory appeal. However, their excessiveuse can be harmful. Milk tea, rich in proteins, fats, and sugars,poses challenges for colorant detection. Biocomma addressesthese challenges by adding a zinc sulfate solution to the extractionsolvent to reduce interference, and develops a HPLC method withsimplified operation and good recovery to detect 8 synthetic foodcolorants of tartrazine, sunset yellow, new red, carmine cochineal,amaranthus red, allura red, brilliant blue and erythrosine in milk teafor routine testing.

Experiment

Preparation

Prepare ethanol-ammonia solution: add 700 mL of ethanol and 4mL of ammonia. Dilute to 1 L by water.

Extraction

Weigh 2.0 g of the sample in a 50 mL centrifuge tube. Add 5 mL ofzinc sulfate solution (120 g/L) and mix well. Add 25 mL of ethanolammonia solution and vortex for 1 min. Extract by ultrasonictreatment for 15 min, and centrifuge at 8000 r/min for 5 min.Transfer the supernatant into a clean 50 mL centrifuge tube. Add15 mL of the ethanol-ammonia solution to the remaining sample.Repeat the extraction procedures. Combine the supernatants anddilute to 50 mL. Centrifuge again if the solution is cloudy. Pipette 10mL of supernatant to a clean tube and concentrate to 2 mL at 50°C.Add 10 mL of 5% aqueous methanol solution and mix well. Thesample is ready for purification

Purification (Copure® PWAX Cartridge, 150 mg/ 6 mL)

Activation: activated the cartridge by 6 mL of methanol, then 6 mLof water.

Loading: add prepared sample to the activated cartridge.

Washing: add 5 mL of water, then 5 mL of methanol. Drain thecartridge.

Elution: add 8 mL of 2% ammoniated methanol solution and collectthe eluate. Evaporate to about 0.3 mL at 45 °C. Dilute to 2 mL with0.02 mmol/L ammonium acetate solution (pH=9.0). Vortex to mixwell. After filter by PTFE membrane, the sample is ready for LCMS/MS analysis.

Instrumental Conditions

Instrument: Liquid Chromatograph, ThermoFisher U3000

Chromatographic column: Agilent ZORBAX SB-C18 (4.6 mm×250mm, 5 μm)

Mobile phase: A: 0.02mol/L ammonium acetate solution, B:methanol

Flow rate: 1.0 mL/min

Column temperature: 30 ℃

Injection volume: 10 μL

Detector: UV detector

Detector wavelength range: 400~800 nm. (Tartrazine: 415 nm. Newred, carmine cochineal, amaranthus red, sunset yellow, allura redand erythrosine: 520 nm. Brilliant blue: 630 nm.)

Table 1. Gradient Elution Program