On-line SPE–UHPLC method using fused core columns for extraction and separation of nine illegal dyes in chilli-containing spices

•Method for determination of illegal Sudan dyes in chilli containing spices was developed.•Method shows on-line SPE–UHPLC separation system with rapid sample pretreatment.•On-line dyes extraction was developed using fused core precolumns.•Method shows innovative approach in fused core columns using both dimensions.

The presented work describes the development of a simple, fast and effective on-line SPE–UHPLC–UV/vis method using fused core particle columns for extraction, separation and quantitative analysis of the nine illegal dyes, most frequently found in chilli-containing spices. The red dyes Sudan I–IV, Sudan Red 7B, Sudan Red G, Sudan Orange G, Para Red, and Methyl Red were separated and analyzed in less than 9 min without labor-consuming pretreatment procedure. The chromatographic separation was performed on Ascentis Express RP-Amide column with gradient elution using mixture of acetonitrile and water, as a mobile phase at a flow rate of 1.0 mL min−1 and 55 °C of temperature. As SPE sorbent for cleanup and pre-concentration of illegal dyes short guard fused core column Ascentis Express F5 was used. The applicability of proposed method was proven for three different chilli-containing commercial samples. Recoveries for all compounds were between 90% and 108% and relative standard deviation ranged from 1% to 4% for within- and from 2% to 6% for between-day. Limits of detection showed lower values than required by European Union regulations and were in the range of 3.3–10.3 µg L−1 for standard solutions, 5.6–235.6 µg kg−1 for chilli-containing spices.

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