A new alternative assay for sensitive analysis of ethylenethiourea and propylenethiourea in fruit samples after their...

Ultra-high-performance liquid chromatography (UHPLC) coupled with a cobalt phthalocyanine screen-printed carbon electrode (CoPc-SPCE) was developed and validated for quantitative analysis of ethylenethiourea (ETU) and propylenethiourea (PTU). CoPC-SPCE provided high catalytic properties for ETU and PTU oxidation. This fabricated electrode is inexpensive, disposable, and easy to prepare by an in-house screen-printing technique. The chromatographic separation was performed in isocratic mode on a reversed phase C18 (100 mm × 4.6 mm, 3 μm) column, using a 90 : 10 (v/v) ratio of 0.05 M phosphate buffer solution (pH 4) and methanol as the mobile phase with a flow rate of 1.0 mL min^-1 at an oxidation potential of +0.7 V vs. Ag/AgCl. The separation could be achieved within 3 min, and a wide linear range of 0.01-100 μg mL^-1 (r² > 0.99) was obtained for both analytes. The limits of detection (3 S/N) were found to be 0.006 and 0.009 μg mL^-1 for ETU and PTU, respectively. Furthermore, this proposed method was utilized to determine ETU and PTU in fruit samples with satisfactory results, yielding excellent intra-day and inter-day relative standard deviations and recoveries. These results demonstrated that the proposed assay can be used as a new alternative way for inexpensive, rapid, selective and sensitive determination of ETU and PTU in fruit samples.