Natural Material Shungite as Solid-Phase Extraction Sorbent for the Extraction of Red Synthetic Dye Ponceau 4R from Tap Water, Wine, and Juice

Three-dimensional dual-network magnetic conductive hydrogel for the highly sensitive electrochemical detection of ponceau 4R in foods

Synthetic pigment Ponceau 4 R is a commonly used additive in the process of various foods. Due to its potential toxicity to humans, realizing high sensitivity and rapid detection of Ponceau 4 R is extremely important. In this study, we synthesized a novel dual-network magnetic conductive hydrogel (MCHG) via a simple one-pot low temperature stirring method. In MCHG, cationic guar gum (CGG) and β-cyclodextrin (β-CD) formed a primary three-dimensional network cross-linked by N, N-methylene bisacrylamide. A second network was formed in MCHG by CGG, β-CD and magnetite@carboxylate-terminated carbon nanotubes (Fe3O4@COOH-MWCNTs) through hydrogen bonding and electrostatic interactions. Fe3O4@COOH-MWCNTs enhanced cross-linking in the MCHG hydrogel, whilst also boosting the equilibrium adsorption capacity of Ponceau 4 R (61.8 mg g-1), electrical conductivity and electrocatalytic performance. Application of MCHG to a glassy carbon electrode (GCE) created a highly sensitive electrochemical sensor for the detection of Ponceau 4 R. Under optimized testing conditions, the sensor offered a very wide linear range (0.01-200.0 μM) and a low limit of detection (1.8 nM) for Ponceau 4 R. When the sensor was applied to the detection of Ponceau 4 R in spiked honey and liqueur samples, excellent recoveries were achieved (88.2%-107.0%). Furthermore, analyses of commercial biscuit and candy samples using the MCHG/GCE sensor and a national standard ultraviolet spectrophotometry method afforded identical results. Results demonstrate that multifunctional hydrogels show great promise as signal amplification agents in electrochemical detection of target compounds in foods.

Surfactant-supported organoclay for removal of anionic food dyes in batch and column modes: adsorption characteristics and mechanism study

This study aimed to create CTAB-modified bentonite organoclay (Bt@CTAB) by mixing the naturally occurring mineral bentonite (Bt) with the cationic surfactant cetyltrimethylammonium bromide (CTAB). Elemental analysis, N2 adsorption–desorption isotherm, scanning electron microscopy (SEM), FTIR spectroscopy, XRD, and thermogravimetric (TGA) analysis have been employed to analyze both the unmodified Bt and the Bt@CTAB organoclay. The dye sorption onto Bt@CTAB organoclay was investigated in the batch and column modes using aqueous solutions of anionic food dyes, viz., Sunset yellow FCF (E110), Azorubine (E122), and Ponceau 4R (E124) (individually or in a mixture). Experimental variables affecting the adsorption process, such as initial dye concentration, contact time, temperature, pH, and adsorbent dose, are evaluated. From the kinetic investigations, the adsorption of E110, E122, and E124 dyes well matched the pseudo-second-order kinetic model. E110 and E122 dyes adsorption onto Bt@CTAB attained equilibrium in 120 min while attained in 240 min for E124. The investigated food dyes were expected to achieve maximum adsorption efficiencies at concentration of 100 ppm of (E110 and E124) and 150 ppm of (E124), an adsorbent dosage of 0.4 gL−1, and an initial pH 5. In addition, Langmuir model best fits the sorption isotherm data, with the maximum adsorption capacity at 303 K being 238 mg/g, 248.75 mg/g, and 358.25 mg/g for E110, E122, and E124, respectively. The Bt@CTAB organoclay can be regenerated up to the 4th cycle successfully. The thermodynamic studies revealed the spontaneous and exothermic nature of the adsorption of these anionic dyes onto Bt@CTAB organoclay. The prepared cationic Bt@CTAB organoclay was successfully applied for the removal of E110, E122, and E124 from real water samples, synthetic effluents, and colored soft drinks with a recovery (R%) higher than 95%. The plausible adsorption mechanism of E110, E122, and E124 onto Bt@CTAB organoclay is proposed to be due to electrostatic interaction and hydrogen bond formation. Finally, the present study shows that Bt@CTAB organoclay may be employed efficiently and effectively to remove anionic food dyes from a wide range of real water and colored soft drinks.