Validation and measurement uncertainty of analytical methods for various azo dye adulterants in Curcuma longa L

Abstract: Food adulteration involving the illegal addition of dyes to foodstuffs has become an alarming issue in recent years. This study developed and validated a high-performance liquid chromatography (HPLC)–DAD (diode array detector) method for the simultaneous determination of nine azo dyes (Butter Yellow, Sudan Orange G, Para Red, Sudan I, Sudan II, Sudan III, Sudan IV, Sudan Red 7B, and Scarlet 808). Moreover, a qualitative analysis method using liquid chromatography–tandem mass spectrometry was developed to more accurately identify peaks detected in HPLC–DAD. The calibration curve represented good linearity (r² ≥ 0.9998) over the measured concentration range of 0.5–25 mg/kg. limit of detection and limit of quantification were 0.01–0.04 and 0.04–0.12 mg/kg, respectively. Accuracy and precision were 96.0–102.6 and 0.16–2.01 (relative standard deviation%), respectively. Additionally, the measurement uncertainty and HorRat value were estimated. Several Curcuma longa L. distributed in Korea were collected and monitored for azo dye contaminants. Practical Application: The proposed HPLC–DAD method represents a significant advancement in the field, offering a reliable means of quantifying azo dyes and identifying their presence even at trace levels in adulterated turmeric. This not only contributes to ensuring the safety and integrity of turmeric products but also establishes precedent for robust analytical techniques in addressing food safety challenges.