No Time to Dye: Portable Surface-Enhanced Raman Scattering for On-Site Detection of Sudan IV Dye in Palm Oil

Abstract The widespread use of Sudan IV dye as an adulterant in palm oil poses significant public health risks. This nonfood-grade dye, linked to carcinogenic effects, has prompted a pressing need for efficient, rapid, and reliable field-portable detection methods. This study investigates the application of hand-held surface-enhanced Raman scattering (SERS) technology for the rapid and sensitive detection of Sudan IV dye in palm oil. By leveraging the enhanced sensitivity of SERS, we provide a field-deployable solution that can be utilized in local markets and production sites, facilitating real-time monitoring and ensuring food safety. Using a univariate calibration approach, a predictive model was developed to quantify Sudan IV in palm oil, achieving a limit of detection (LOD) of 0.0065 mg/mL. In total, 64 palm oil samples obtained from markets in Cameroon and 9 palm oil samples purchased online were screened for Sudan IV using SERS, which identified four online samples as testing positive for this azo dye. To verify these findings, liquid chromatography–mass spectrometry (LC-MS) was subsequently performed on the samples bought online. LC-MS analysis confirmed the presence of Sudan IV in the four SERS-positive oils purchased from an online retailer and additionally detected the dye in a fifth oil from the same source.