Interference-free determination of illegal dyes in sauces and condiments by matrix solid phase dispersion (MSPD) and liquid chromatography (HPLC–DAD)

A fast, simple and effective extraction method based on matrix solid phase dispersion (MSPD) was developed and validated for the simultaneous cleaning-up and quantitative extraction of illegal dyes (sudan I, sudan II, sudan III and sudan IV) from different sauces and condiments. Several parameters as sorbent, cleaning procedure to eliminate carothenoids and other interferences, and solvents for elution were evaluated to find the optimal MSPD conditions. The best results were obtained using a system containing washed sea sand and Florisil as sorbents and sodium sulphate as desiccant; hexane was used as defatted agent and acetonitrile as elution solvent. Quantitative analyses were performed by liquid chromatography (LC) with diode array detection (DAD). The chromatographic separation was performed on a Phenomenex Synergy Polar RP column with isocratic elution using methanol/acetonitrile/water 65/20/15, v/v/v, as the mobile phase at a flow rate of 1.0 mL min−1 and 30 °C of temperature. Under these conditions sudan I–IV recoveries were between 60% and 99% and relative standard deviations ranging from 2.0% to 10.0%. Limits of detection resulted five times lower than the values required by European regulations and were ranged between 0.05 and 0.09 μg g−1. The applicability of this MSPD–DAD method to determine illegal sudan dyes in sauce and condiment samples was demonstrated. This method has potential to be applied using a simple instrumentation present in most analytical laboratories.