Polyoxometalates-graphene nanocomposites modified electrode for electro-sensing detection of Sudan I in food

Determination of fifteen illegal colorants in traditional Chinese medicines by two hydrophobic DES-based microextraction methods coupled with an HPLC-DAD

The dyeing and adulteration of traditional Chinese medicines (TCMs) are continuously updated. Valuable analytical methods for the daily inspection of illegal colorant additives in TCMs and the preparations are in demand. Two deep eutectic solvent (DES)-based vortex-assisted liquid-liquid microextraction (VA-LLME) and ultrasonic-assisted solid-liquid microextraction (UA-SLME) were developed for the sample pretreatment of ten water-soluble colorants and five water-insoluble colorants, respectively, followed by an HPLC-DAD detection. Fifteen colorants were analyzed at four detection wavelengths within 40 min of gradient elution. The optimal DES of VA-LLME and UA-SLME were screened from 23 homemade DESs. The factors affecting the extraction efficiency of VA-LLME and UA-SLME were optimized systematically. Under the optimal conditions, ten water-soluble colorants analyzed by DES-based VA-LLME-HPLC-DAD showed good linearity (R ≥ 0.9995) within the optimal linear range. The LODs and LOQs were 0.2-1.0 μg g-1 and 0. 5-5.0 μg g-1, respectively. The recoveries of spiked samples were 80.2%-104.7 %, with RSDs ≤ 4.39 %. Five water-insoluble colorants of Sudan I‒IV and Sudan 7B analyzed by DES-based UA-SLME-HPLC-DAD showed good linearity (R ≥ 0.9995) within the optimal linear range. The LODs and LOQs were 0.8-8.0 μg g-1 and 4.0-40.0 μg g-1, respectively. The recoveries of spiked samples were 94.2%-103.1 %, with RSDs ≤ 4.81 %. The proposed DES-based VA-LLME-HPLC-DAD was successfully applied to analyze six water-soluble yellow colorants in Cuscutae Semen, salted Cuscutae Semen, and four water-soluble red colorants in Schisandrae Chinensis Fructus. The proposed DES-based UA-SLME-HPLC-DAD was successfully applied to analyze five water-insoluble red colorants in Dieda pills. The study provides analytical method options for routine tests of water-soluble, water-insoluble, or both water-soluble/-insoluble illegal colorant additives in herbal medical materials and preparations by the relevant proposed DES-based sample pretreatment method or a combination of the two proposed DES-based methods.

Sudan I monitoring as a hazardous azo dye using an electroanalytical tool amplified with NiO/SWCNTs-ionic liquid catalysts

Sudan I is an azo dye that causes cancer and is not allowed to be used in food products. The current study focused on the design and manufacture of an electrochemical sensor modified with NiO/SWCNTs, as a nano-catalyst, and 1-hexyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (1H3MIbTMI), as an ionic liquid binder, to monitor Sudan I as azo additive dyes in various food samples. The modified carbon paste electrode (CPE/NiO/SWCNTs/1H3MIbTMI) offered superior electrochemical performance metrics as an analytical sensor to detect trace levels of Sudan I within the concentration range of 1.0 nM-250 μM. The limit of detection was determined as 0.3 nM by the differential pulse voltammetric (DPV) technique. The proposed CPE/NiO/SWCNTs/1H3MIbTMI can be put forward to be employed as an analytical instrument for sensing Sudan I in various culinary sauces, including chili, tomato, and strawberry sauces. The obtained recovery range was determined as 97.6%-104.35%. These findings demonstrated the effectiveness of the newly created material and its potential for usage as a novel analytical instrument.