An update on the sample preparation and analytical methods for synthetic food colorants in food products

Colorants, especially synthetic colorants, play a crucial role in enhancing the aesthetic qualities of food owing to their cost-effectiveness and stability against environmental factors. Ensuring the safe and regulated use of colorants is essential for maintaining consumer trust in food safety. Various preparation and analytical technologies, which are continuously undergoing improvement, are currently used to quantify of synthetic colorants in food products. This paper reviews recent developments in analytical techniques for synthetic food colorants, detection and compares the operational principles, advantages, and disadvantages of each technology. Additionally, it also explores advancements in these technologies, discussing several invaluable tools of analysis, such as high-performance liquid chromatography, liquid chromatography-tandem mass spectrometry, electrochemical sensors, digital image analysis, near-infrared spectroscopy, and surface-enhanced Raman spectroscopy. This comprehensive overview aims to provide valuable insights into current progress and research in the field of food colorant analysis.

Development of a highly sensitive ultra-small ratiometric fluorescence nanosphere probe for Sunset Yellow detection

A highly sensitive ultra-small ratiometric fluorescence nanosphere probe was successfully manufactured to detect Sunset Yellow (SY). The probe, CMCS@N, S-CDs/Rh6G, was formed through the encapsulation of N, S-CDs and Rh6G within carboxymethyl chitosan (CMCS) through in situ cross-linking. Remarkably, our nanosphere probe had an average grain diameter of 6.80 nm and exhibited excellent dispersibility without the need for additional solvents. The probe exhibited a strong linear relationship with SY concentration in the range of 0.26-100 μM, with a low detection limit of 0.078 μM. Furthermore, SY demonstrated strong fluorescence quenching capability on our nanosphere probe, with the fluorescence quenching mechanism involving a combined effects of inner filter effect (IFE) and static quenching. Notably, our nanosphere probe retained the bacteriostatic properties of CMCS, with a substantial bacteriostasis rate of 77.58 %, introducing novel potential applications.

Fast Determination of Eleven Food Additives in River Water Using C18 Functionalized Magnetic Organic Polymer Nanocomposite Followed by High-Performance Liquid Chromatography

A novel magnetic nanomaterial with Fe3O4 as the core, PS-DVB as the shell layer, and the surface modified with C18 (C18-PS-DVB-Fe3O4) had been synthesized by seeded emulsion polymerization. C18-PS-DVB-Fe3O4 retains the advantages of the chemical stability, large porosity, and uniform morphology of organic polymers and has the magnetic properties of Fe3O4. A simple, flexible, and efficient magnetic dispersive solid phase extraction (Mag-dSPE) method for the extraction of preservatives, sweeteners, and colorants in river water was established. C18-PS-DVB-Fe3O4 was used as an adsorbent for Mag-dSPE and was coupled with high-performance liquid chromatography (HPLC) to detect 11 food additives: acesulfame, amaranth, benzoic acid, tartrazine, saccharin sodium, sorbic acid, dehydroacetic acid, sunset yellow, allura red, brilliant blue, and erythrosine. Under the optimum extraction conditions, combined with ChromCoreTMAQC18 (5 μm, 4.6 × 250 mm), 20 mmol/L ammonium acetate aqueous solution and methanol were used as mobile phases, and the detection wavelengths were 240 nm and 410 nm. The limits of detection (LODs) of 11 food additives were 0.6-3.1 μg/L with satisfactory recoveries ranging from 86.53% to 106.32%. And the material could be reused for five cycles without much sacrifice of extraction efficiency. The proposed method has been used to determine food additives in river water samples, and results demonstrate the applicability of the proposed C18-PS-DVB-Fe3O4 Mag-dSPE coupled with the HPLC method to environment monitoring analysis.

A composite polymer of polystyrene coated with poly(4-vinylpyridine) as a sorbent for the extraction of synthetic dyes from foodstuffs

A poly(St-co-EGDMA)@poly(4-vinylpyridine-co-EGDMA) composite polymer was synthesised by precipitation reversible addition-fragmentation chain transfer (RAFT) polymerization. The polymer was investigated as a sorbent for extraction of synthetic food dyes: ponceau 4R, tartrazine, sunset yellow, brilliant blue and erythrosine from soft drinks. The morphology and composition of the polymer were characterized and confirmed respectively by scanning electron microscopy and Fourier-transform infrared spectroscopy. The pH dependence experiment revealed that the adsorption of food dyes by the polymer was pH dependent and the maximum adsorption was achieved at pH 3. Adsorption between the polymer and the dyes was mainly due to electrostatic interaction. Under the optimized pH conditions, the polymer was saturated with the dye solutions at a concentration of about 200 μg mL-1 and exhibited a maximum adsorption capacity of 9 μg mg-1. The values were higher than those for polyamide, a sorbent used in the standard method. The recovery from the real samples of the three spiked concentrations 10, 50 and 100 μg mL-1 was respectively within the ranges of 83.2-107.2%, 94.5-110.7% and 79.2-111.5%, with a SD within ±4%. The sorbent could be reused more than 10 times with a recovery higher than 80%. The small volume requirement of the sample and sorbent during the sample pre-treatment, indicated that poly(St-co-EGDMA)@poly(4-vinylpyridine-co-EGDMA) was a potential material for food dye extraction in an environment-friendly and economical manner.

A Comparative Study of Advanced Stationary Phases for Fast Liquid Chromatography Separation of Synthetic Food Colorants

Food analysis demands fast methods for routine control and high throughput of samples. Chromatographic separation enables simultaneous determination of numerous compounds in complex matrices, several approaches increasing separation efficiency and speed of analysis were involved. In this work, modern types of column with monolithic rod or superficially porous particles were employed and compared for determination of eight synthetic food dyes, their chromatographic performance was evaluated. During method optimization, cyano stationary phase Chromolith Performance CN 100 × 4.6 mm and Ascentis Express ES-CN 100 × 4.6 mm, 5 µm were selected for the separation of polar colorants. The separation was performed by gradient elution of acetonitrile/methanol and 2% water solution of ammonium acetate at flow rate 2.0 mL min-1. Mobile phase composition and the gradients were optimized in order to enable efficient separation on both columns. The method using fused-core particle column provided higher separation efficiency, narrow peaks of analytes resulted in increased peak capacity and shortening of analysis time. After the validation, the method was applied for analysis of coloured beers, soft drinks and candies.

Ultrasonically synthesis of Mn- and Cu- @ ZnS-NPs-AC based ultrasound assisted extraction procedure and validation of a spectrophotometric method for a rapid preconcentration of Allura Red AC (E129) in food and water samples

This study is devoted on Allura Red as food colorant preconcentration and determination in beverage, fruit juice and drink water samples is based on usage of Mn- and Cu- @ ZnS-NPs-AC as new sorbent for ultrasound-assisted-dispersive solid-phase microextraction (UA-DSPME) combined with ultraviolet-visible spectrophotometric based method (UV-Vis). Contribution of volume of eluent, pH, sorbent mass and sonication time on response following conduction of 28 experiments were optimized and investigated while their significantly justified according to p-value. Values of "Prob > F" less than 0.0500 is proportional with their significant influence on recovery of analyte. Under the optimum conditions 0.14 mL of THF; pH of 2.5; 8 mg of sorbent and 3 min sonication time guide and help achievement of limit of quantification (LOQ) and limit of detection (LOD) of 6.08 and 20.26 ng mL^-1, respectively. The accuracy of method was validated according to calculation of recovery following spiking 400 and 600 ng mL^-1 to blank solution and recovery as more reliable indication of accuracy 93.41 and 102.17% recoveries with RSD < 3.5%, which demonstrate the successful applicability of present method for real sample analysis. The maximum sorbent capacity was 50.0 mg g^-1 based on Langmuir isotherm as best model with high correlation coefficient. Combination of UA-DSPME and UV-Vis lead to higher sensitivity and lower cost for accurate and repeatable monitoring of Allura Red level in beverage, fruit juice and drink water samples with acceptable recovery and reasonable RSD%.