Abstract
The food colourants copper chlorophyll (CuCh) and sodium copper chlorophyllin (CuCh-Na) are used worldwide in a wide
range of processed foods. We developed an analytical method for the determination of CuCh/CuCh-Na levels in processed foods
to effectively monitor the appropriate use of these colourants. The proposed analytical method involves simultaneous extraction
and parallel analysis of hydrophobic CuCh and hydrophilic CuCh-Na without potentially harmful solvents. CuCh/CuCh-Na were
extracted from processed foods with 1-butanol and ethyl acetate. CuCh-Na was extracted from the initial extraction solvent with 0.15
mol/L NaOH, and then the residual extraction solvent and alkaline water layers were dried. Finally, the samples were carbonized
with H2SO4. The carbonized samples were ashed in a muffle furnace at 480°C. The residue was dissolved in 0.1 mol/L HNO3, and
the level of copper in the samples was determined using atomic absorption spectrophotometry to indirectly quantify the levels of
CuCh and CuCh-Na. Recoveries of CuCh and CuCh-Na from spiked samples were in the range of 70.7%-80.8% and 55.6%-72.3%
(except for white chocolate, at 50%), respectively, with standard deviations in the range of 1.7%-5.0% and 1.5%-7.8%, respectively.
In commercial processed foods, the levels of CuCh and CuCh-Na ranged from ND (not detected) to 3.7 mg/kg and from ND to 8.0
mg/kg as copper, respectively.
