Electrochemical Characterization Using Biosensors with the Coagulant Moringa oleifera Seed Lectin (cMoL).

Triturated Moringa oleifera seeds have components that adsorb recalcitrant indigo carmine dye. Coagulating proteins known as lectins (carbohydrate-binding proteins) have already been purified from the powder of these seeds, in milligram amounts. The coagulant lectin from M. oleifera seeds (cMoL) was characterized by potentiometry and scanning electron microscopy (SEM) using MOFs, or metal-organic frameworks, of [Cu3(BTC)2(H2O)3]n to immobilize cMoL and construct biosensors. The potentiometric biosensor revealed an increase in the electrochemical potential resulting from the Pt/MOF/cMoL interaction with different concentrations of galactose in the electrolytic medium. The developed aluminum batteries constructed with recycled cans degraded an indigo carmine dye solution; the oxide reduction reactions of the batteries generated Al(OH)3, promoting dye electrocoagulation. Biosensors were used to investigate cMoL interactions with a specific galactose concentration and monitored residual dye. SEM revealed the components of the electrode assembly steps. Cyclic voltammetry showed differentiated redox peaks related to dye residue quantification by cMoL. Electrochemical systems were used to evaluate cMoL interactions with galactose ligands and efficiently degraded dye. Biosensors could be used for lectin characterization and monitoring dye residues in environmental effluents of the textile industry.

A novel recycling way of blast furnace dust from steelworks: Electrocoagulation coupled micro-electrolysis system in indigo wastewater treatment.

In this study, a novel electrocoagulation electrode, based on blast furnace dust (BFD) from steelworks waste, was prepared for indigo wastewater treatment, and the performance was compared with different ratios of Fe-C composite electrodes. The BFD electrode exhibited great electrochemical performance and removal effect. The presence of Fe-C micro-electrolysis in the electrocoagulation system of the BFD electrode was demonstrated by FT-IR, Raman, ESR, and quenching experiments. Density Functional Theory (DFT) calculations further demonstrated that the iron-carbon ratio could influence the degree of O-O breaking and enhance ·OH generation. Finally, the BFD electrode's operating parameters were perfected, and the COD removal and decolorization could reach 75.7% and 95.8% within 60 min, respectively. Fe-C composite electrodes reduce energy consumption compared with the traditional Fe/Al electrode and have a lower production cost, which provides a potential way to recycle and reuse the resources of solid waste in steelworks, the concept of "waste controlled by waste" is realized.

A more selective and accurate method than indigo method for measuring dissolved ozone concentration (p-vinylbenzoic acid method).

Dissolved ozone concentration measurement is crucial for ozone treatment. In the most used conventional indigo method, the ozone concentration is measured by the decrease in absorbance due to the loss of the C-C double bond of indigotrisulfonic acid. However, measurement of ozone concentration is difficult when water contains substances that react with C-C double bonds other than ozone. To address this concern, we developed a novel breakthrough method to measure ozone concentration by measuring the p-formylbenzoic acid (p-FBA) produced after the reaction of p-vinylbenzoic acid and ozone. The formation of p-FBA was almost not caused by other substances (hypochlorous acid, hypobromous acid, permanganate ion and hydrogen peroxide), and its yield to ozone was maintained at 1 in river water, treated wastewater and seawater. In addition, the experimental error is smaller with the new method than with indigo. Furthermore, the new method does not require cumbersome calibration unlike indigo method because highly pure forms of p-FBA are commercially available. p-FBA can be separated by liquid chromatography and detected with highly sensitive ultraviolet and mass spectrometric detectors, and hence easily analyzed simultaneously with other substances. Our new method contributes to extensive ozone treatment and ozonation management.

Development and optimization of a microbial co-culture system for heterologous indigo biosynthesis.

BACKGROUND: Indigo is a color molecule with a long history of being used as a textile dye. The conventional production methods are facing increasing economy, sustainability and environmental challenges. Therefore, developing a green synthesis method converting renewable feedstocks to indigo using engineered microbes is of great research and application interest. However, the efficiency of the indigo microbial biosynthesis is still low and needs to be improved by proper metabolic engineering strategies. RESULTS: In the present study, we adopted several metabolic engineering strategies to establish an efficient microbial biosynthesis system for converting renewable carbon substrates to indigo. First, a microbial co-culture was developed using two individually engineered E. coli strains to accommodate the indigo biosynthesis pathway, and the balancing of the overall pathway was achieved by manipulating the ratio of co-culture strains harboring different pathway modules. Through carbon source optimization and application of biosensor-assisted cell selection circuit, the indigo production was improved significantly. In addition, the global transcription machinery engineering (gTME) approach was utilized to establish a high-performance co-culture variant to further enhance the indigo production. Through the step-wise modification of the established system, the indigo bioproduction reached 104.3 mg/L, which was 11.4-fold higher than the parental indigo producing strain. CONCLUSION: This work combines modular co-culture engineering, biosensing, and gTME for addressing the challenges of the indigo biosynthesis, which has not been explored before. The findings of this study confirm the effectiveness of the developed approach and offer a new perspective for efficient indigo bioproduction. More broadly, this innovative approach has the potential for wider application in future studies of other valuable biochemicals' biosynthesis.

Electrochemical Fingerprint Biosensor for Natural Indigo Dye Yielding Plants Analysis.

Indigo is a plant dye that has been used as an important dye by various ancient civilizations throughout history. Today, due to environmental and health concerns, plant indigo is re-entering the market. Strobilanthes cusia (Nees) Kuntze is the most widely used species in China for indigo preparation. However, other species under Strobilanthes have a similar feature. In this work, 12 Strobilanthes spp. were analyzed using electrochemical fingerprinting technology. Depending on their electrochemically active molecules, they can be quickly identified by fingerprinting. In addition, the fingerprint obtained under different conditions can be used to produce scattered patter and heatmap. These patterns make plant identification more convenient. Since the electrochemically active components in plants reflect the differences at the gene level to some extent, the obtained electrochemical fingerprints are further used for the discussion of phylogenetics.

Colorimetric and fluorometric nanoprobe for selective and sensitive recognition of hazardous colorant indigo carmine in beverages based on ion pairing with nitrogen doped carbon dots.

Indigo carmine (IC) dye is hazardous and allergenic for humans even though it has been excessively used in a wide range of industries. Therefore, the quantitative determination of IC is still challenging. Herein, for the first time, we have developed fluorometric and colorimetric dual-mode nanoprobe derived from the ion-pair association complex between the negatively charged IC and positively charged N@C-dots in pH = 3.0. Consequently, the binding between N@C-dots and IC resulted in cyan blue and quenching of N@C-dots fluorescence. The dependence of the fluorescence response on IC concentrations was linear over the range of 0.73-10.0 µM (R2 = 0.9989) with LOD of 0.24 µM. On the other hand, the linearity of the colorimetric method ranged from 9.97 to 80.0 µM (R2 = 0.9986) with LOD of 3.3 µM. The sensor was applied for estimation of IC in fruit juice and soft drink without the need for exhaustive extraction steps.

A three-dimensional origami microfluidic device for paper chromatography: Application to quantification of Tartrazine and Indigo carmine in food samples.

Herein, we report three-dimensional paper chromatography (3D-PC) as a micro-chromatographic platform. The method was based on applying the origami microfluidic device for separation, coupled by colorimetric methods for simultaneous determination. The microfluidic device fabrication was a facile printing approach. Two azo food dyes, Tartrazine (E102) and Indigo carmine (E132), were selected as a model analyte, while carbonate-bicarbonate buffer was used as the mobile phase. Our micro-chromatographic device is associated with two big advantages including needing very small volume of mobile phase ( ~12 µL) and ultrafast separation time (~35 s). Under the optimal conditions, the method provided acceptable linear ranges of 0. 0 g L1-18.0 g L1 (R2 = 0.997) for E102 and 0.070 g L1-10.0 g L1 for E132 and the limits of detection (3σ/slope) were evaluated as 0.620 and 0.060 g L1, respectively. The proposed method was successfully applied in the separation and quantification of these dyes in commercial food products such as jelly, candy, and four kinds of drink samples without any sample preparation prior to analysis. The mean recovery values for the real sample analysis were in the range of 100.14%-102.38% for E132 and E102 respectively. The inter-device relative standard deviations were in the ranges of 1.5%-11.8%. In total, our chromatographic µPAD is small (1.0 cm × 1.0 cm × 0.5 cm), portable, inexpensive, no need of specialized user, requires low volumes of sample (0.5 µL), and can perform separation using 12 µL of aqueous mobile phase in very short time.

Determination of the food dye indigotine in cream by near-infrared spectroscopy technology combined with random forest model.

Artificial pigment is a common food additive in cream products. If added in excess, it will do harm to human body. At present, there is no research on the detection of cream pigment by Near Infrared (NIR) spectroscopy. In this paper, a method based on random forest was applied to determine the indigotine in cream. Weighting in the experiments was accomplished using analytical balances with precision as low as 0.0001 g. The NIR spectra data of cream with different concentration of indigotine were recorded. The original spectra was pretreated by SG smoothing, mean centering and second derivative. Random forest was applied to establish a quantitative analysis model for cream pigment content, and multiple evaluation criteria were selected to comprehensively evaluate the model. The R2 was 0.9402, RMSEP was 0.2509 and RPD was 4.0893. Consequently, NIR spectroscopy, combined with data pretreatments and random forest model, was confirmed to be an interesting tool for non-destructive evaluation of pigment content in cream.

Degradation of indigo carmine in water induced by non-thermal plasma, ozone and hydrogen peroxide: A comparative study and by-product identification.

The non-thermal plasma (NTP) technique is an advanced oxidation technology (AOT) applied to the degradation of organic compounds in water. In this study, the degradation kinetics of indigo carmine was investigated systematically, applying N2-NTP, O2-NTP, ozonolysis and hydrogen peroxide and the results were compared. The transient species (OH, O and NO radicals) formed with the NTP discharge at the gas-liquid interface and their products (NO3-, NO2-, H2O2) stabilized by the water, were identified and quantified. These species contribute to the effects on the chemical characteristics of the water, such as a decrease in the pH and increase in the conductivity and redox potential. Additionally, the stabilization of the oxidative species was estimated from the degradation reactions induced by the post-discharge effect, which was significant in the case of N2-NTP, due to the presence of long-lived species, such as nitrite and nitrate. The kinetics study revealed first-order kinetics for IC color removal and the rate constant values followed the order: O2-NTP (3.0 × 10-1 min-1) > O3 (1.4 × 10-1 min-1) > N2-NTP (2.2 × 10-2 min-1) > H2O2 (negligible). Also the main by-products of N2-NTP, O2-NTP and ozonolysis degradation reaction were identified by ultra-fast liquid chromatography coupled with mass spectrometry. The route fragmentation showed the formation of indole intermediates, such as isatin, which is an important precursor in organic synthesis.

Degradation of crystal violet in water solution using post discharge DBD plasma treatment: Factorial design experiment and modeling.

In this study, highly oxidative ozone species, generated through dielectric barrier discharge (DBD) plasma, were used to decolorize crystal violet (CV) in aqueous solutions. The solution was exposed to a post-discharge plasma with a mixture of oxygen and argon as carrier gas. The exhaust plasma gas was brought into contact with the solution to be treated in a bubbler by the post discharge configuration. The degradation of the contaminants would be improved by the enhancement of the reactive species diffusion in the solution in the post discharge configuration. The effects of different parameters including oxygen percentage in the carrier gas, discharge power, and total flow rate were investigated on the efficiency of CV removal. Further, the concentrations of ozone in the gas and liquid phases were measured via iodine and indigo methods, respectively. Under optimal conditions, the entire dissolved CV was degraded after 60 s of plasma treatment. Kinetic study revealed that the reaction between ozone and CV follows the behavior of a first-order reaction. After plasma treatment, the aromatic fragment and its intermediates completely disappeared. Analysis of variance with an excellent coefficient of determination of 0.988 ensured a satisfactory fit between second-order regression model and the experimental data. The high CV removal rate constant of 4.88 min-1 obtained at a low discharge power of 5 W was of paramount importance in comparison with previous studies.

Development and Validation of an Effective Spectrophotometric Method for Simultaneous Determination of Synthetic Colorants After Cloud Point Extraction and Comparision with New Green HPLC Method.

Background: Synthetic colorants are largely used in the pharmaceutical products to increase the attractiveness of products and to help patients distinguish between pharmaceuticals. Despite their commercial advantages, synthetic colorants may, in some cases, have a negative impact on the human body. It is therefore imperative to measure the quantities in food products and pharmaceuticals with a fast, reliable, and sensitive method. Objective: The analyzed synthetic colorants in this study are Erythrosine [(E) E127], Quinoline Yellow [(QY) E104], and Indigo Carmine [(IC) E132]. The aim of this study was to develop and validate a new method for the preconcentration and simultaneous determination of these colorants in pharmaceutical preparations. Method: The developed method has many advantages such as novelty, sensitivity, cost effectiveness, speed, and environmental friendliness. This method is based on the cloud-point extraction (CPE) method coupled with first-derivative spectrophotometry (FDS). In the proposed method, QY, E, and IC were extracted from an aqueous solution by using mixed micelles of TritonX-100 and cetyltrimethylammonium bromide. The effect of the main parameters such as solution pH, surfactant and salt concentration, incubation time, and temperature on the CPE of colorants were investigated and optimized. Under the optimal conditions, the extracted surfactant-rich phase was diluted with acetone, and the first-derivative absorbance values were measured at wavelengths 408, 497, and 637 nm for QY, E, and IC, respectively. The CPE-FDS method was applied in the range of 1.0-6.0 µg/mL for E and QY, and 0.3-1.8 µg/mL for IC. Results: The results showed higher correlation coefficients of 0.9990-0.9993 for each colorant. Furthermore, the method was validated for precision and accuracy and assessed the colorants' contents in the synthetic mixtures that contained different ratios of colorants and pharmaceutical samples. The LOD and LOQ values were 31.0 and 103.0 ng/mL for E, 57.0 and 190.0 ng/mL for QY, and 48.0 and 160.0 ng/mL for IC, respectively. The RSDs at the intermediate concentration level (1.2 µg/mL for IC and 3 µg/mL for QY and for E) were <5%. The recovery values in different ratios of colorants were in the ranges of 90.42-101.14, 92.40-105.54, and 96.15-101.25% for E, IC, and QY, respectively. CPE-FDS was also successfully applied to the simultaneous analysis of the QY, IC, and E contents in the various pharmaceutical samples. The obtained results were statistically compared with those obtained by the green HPLC method that was previously reported by Yoshioka et al. and modified by us in this study. Conclusions: The data observed indicated that the CPE-FDS method does not require use of great samples for determination of trace amounts of E, IC, and QY and allows for the determination of analytes in high matrix effect samples such as suspension and syrup. The study concludes that the proposed CPE-FDS method could be considered an alternative to the existing chromatographical methods for the simultaneous determination of trace amounts of E, IC, and QY in pharmaceutical dosage forms for routine analysis. Highlights: A new and effective procedure, simultaneous determination, trace amounts of E, QY, and IC was developed. This is the first report that uses CPE coupled with FDS for the analysis of E, QY, and IC. CPE avoids the use of costly, hazardous, and flammable solvents in large quantities. FDS resolves two or three overlapping spectra and eliminates matrix interferences. CPE-FDS did not require use of large samples for determination of trace colorants.

Semiquantitative determination of food acid dyes by magnetic textile solid phase extraction followed by image analysis.

Magnetic textile solid phase extraction, based on the use of magnetically modified non-woven textile impregnated with chitosan, was successfully employed for the preconcentration of acid food dyes from water solutions. The photos of textile squares with the adsorbed dye were taken with a mobile phone. The image analysis of the photos was performed using appropriate freeware. The values of saturation, obtained through the HSB color space, were proportional to the dye concentration in the analyzed samples. Described inexpensive, simple and elution free assay enables analysis of dyes concentration in various solutions. This novel method has a potential to be a useful alternative to existing semiquantitative determination procedures, especially for dyes analysis.

Bacillus fermenti sp. nov., an indigo-reducing obligate alkaliphile isolated from indigo fermentation liquor for dyeing.

The indigo-reducing, facultatively anaerobic and obligately alkaliphilic strains Bf-1T, Bf-2 and Bf-4 were isolated from an indigo fermentation liquor used for dyeing, which uses sukumo [composted Polygonum indigo (Polygonum tinctorium Lour.) leaves] as a basic ingredient and was obtained from a craft centre in Date City, Hokkaido, Japan. The 16S rRNA gene sequence analyses indicated that the closest neighbours of strain Bf-1T are Bacillus maritimus DSM 100413T (98.3 % 16S rRNA gene sequence similarity), Bacillus persicus DSM 25386T (98.2 %) and Bacillus rigiliprofundi LMG 28275T (97.7 %). The 16S rRNA gene sequence of strain Bf-1T was almost identical to the sequences of strains Bf-2 and Bf-4 (99.9 %). Cells of strain Bf-1T stained Gram-positive and formed straight rods that achieved motility through a pair of subpolar flagella. Strain Bf-1T grew at temperatures of between 15 and 45 °C with optimum growth at 33‒40 °C. The strain grew in the pH range of pH 8‒12, with optimum growth at pH 10. The isoprenoid quinone detected was menaquinone-7 (MK-7), and the DNA G+C content was 41.7 %. The whole-cell fatty acid profile mainly (>10 %) consisted of iso-C15 : 0 and iso-C16 : 0. Phylogenetically related neighbours, although demonstrating high 16S rRNA gene sequence similarity (>97.6 %) with strain Bf-1T, exhibited less than 9 % relatedness in DNA-DNA hybridization experiments. Based on evidence from this polyphasic study, the isolates represent a novel species, for which the name Bacillus fermenti sp. nov. is proposed. The type strain of this species is Bf-1T (=JCM 31807T=NCIMB 15079T).

A novel poly (glycine) biosensor towards the detection of indigo carmine: A voltammetric study.

The electrochemical behavior of indigo carmine (IC) at poly (glycine) modified carbon paste electrode (PGMCPE) was investigated by cyclic and differential pulse voltammetry. The oxidation peak of IC was observed in phosphate buffer of pH 6.5. The influence of different pH, scan rate, and concentration were analyzed. The probable reaction mechanism involved in the oxidation of IC was also proposed. Results showed that PGMCPE a remarkable electrocatalytic activity for the oxidation of IC under optimal conditions. The electrocatalytic response of the sensor was proportional to the IC concentration in the range of (2 × 10-6-1 × 10-5 M) and (1.5 × 10-5-6 × 10-5 M) with a limit of detection 11 × 10-8 M and limit of quantification 3.6 × 10-7 M. The modified electrode demonstrated many advantages such as simple preparation, high sensitivity, low detection of limit, excellent catalytic activity, short response time, and remarkable antifouling property toward IC and its oxidation product.

Selective and simultaneous determination of indigo carmine and allura red in candy samples at the nano-concentration range by flow injection analysis with multiple pulse amperometric detection.

A novel, unique electroanalytical method was developed for the simultaneous quantification of the dyes indigo carmine (IC) and allura red (AR) in candies by coupling flow injection analysis and multiple pulse amperometry with a cathodically pretreated boron-doped diamond electrode, using 0.30 mol L-1 H2SO4 as supporting electrolyte. A dual-potential waveform was employed, causing the electrooxidation of either IC solely or IC and AR simultaneously. Thence, subtraction of current signals was used to quantify IC and AR in the concentration ranges of 70.0-1000 nmol L-1 and 40.0-770 nmol L-1, with limits of detection of 40.0 nmol L-1 and 7.0 nmol L-1, respectively. The proposed method, which permits up to 153 determinations per hour with good precision, was successfully applied in the quantification of these dyes in samples of commercial candies; their obtained contents were similar (at a 95% confidence level) to those from a comparative HPLC method.

Bio-electro oxidation of indigo carmine by using microporous activated carbon fiber felt as anode and bioreactor support.

The bioremediation and electro-oxidation (EO) processes are included among the most promising cleaning and decontamination mechanisms of water. The efficiency of bioremediation is dictated by the biological actuator for a specific substrate, its suitable immobilization and all involved biochemical concepts. The EO performance is defined by the anode efficiency to perform the complete mineralization of target compounds and is highlighted by the low or null use of reagent. Recently, the combination of both technologies has been proposed. Thus, the development of high efficient, low cost and eco-friendly anodes for sustainable EO, as well as, supporting devices for immobilization of biological systems applied in bioremediation is an open field of research. Therefore, the aim of this work was to promote the bio-electrochemical remediation of indigo carmine dye (widely common in textile industry), using new anode based on a microporous activated carbon fiber felt (ACFF) and ACFF with immobilized Laccase (Lcc) from Pycnoporus sanguineus. The results were discolorations of 62.7% with ACFF anode and 83.60% with ACFF-MANAE-Lcc anode, both for 60 min in tap water. This remediation rates show that this new anode has low cost and efficiency in the degradation of indigo dye and can be applied for other organic pollutant.

Mediated electrochemical method for the determination of indigo carmine levels in food products.

In this paper, we have studied the electrochemical behavior of indigo carmine (IC) in the presence and absence of mediator molecules. We have used three azo dyes as mediators in our studies and the effect of mediator molecules on the electron transfer between the IC solution and the electrode surface was explained from the cyclic voltammograms data. Among these dyes, 4-(4-nitrophenilazo)N-benzyl,N-ethylaniline (NBE) showed good performance as an electron transfer mediator. The NBE/carbon paste was characterized with Fourier transform infrared spectroscopy and scanning electron microscopy methods. The redox peak currents of IC were enhanced significantly compared with those obtained at the unmodified electrode. Some parameters affecting sensor response were optimized and then the calibration curve was plotted. The oxidation peak current was proportional to the concentration of IC from 1 to 100µmolL-1. The detection limit was 0.36µmolL-1. The proposed electrode was successfully applied to the determination of IC in various real samples without complex sample pretreatment.

Determination of green, blue and yellow artificial food colorants and their abuse in herb-coloured green Easter beers on tap.

Beer is one of the most popular alcoholic beverages worldwide. For consumer acceptance, significant factors are its taste, flavour and colour. This study determines selected synthetic green, blue and yellow food colorants in popular Easter herb-coloured green beers on tap produced in breweries on Holy Thursday. The abuse of beer colouring with Tartrazine (E 102), Quinoline yellow (E 104), Sunset yellow (E 110), Patent blue (E 131), Indigo carmine (E 132), Brilliant blue FCF (E 133), Green S (E 142) and Fast green FCF (E 143) was assessed in 11 green beer samples purchased in local restaurants. HPLC was used for the separation and detection of artificial colorants with diode-array detection and a Chromolith Performance CN 100 × 4.6 mm column with guard pre-column Chromolith CN 5 × 4.6 mm. Separation was performed in gradient elution with mobile phase containing methanol-aqueous 2% ammonium acetate at pH 7.0. The study showed that eight beers (70%) marketed in the Czech Republic contained artificial colorants (Tartrazine and Brilliant blue FCF). The concentration of colorants found in analysed green herb-coloured beers ranged from 1.58 to 3.49 mg l(-)(1) for Tartrazine, 0.45-2.18 mg l(-)(1) for Brilliant blue, while Indigo carmine was detected only once at concentration 2.36 mg l(-)(1). Only three beers showed no addition of the synthetic colorants. However, the levels of artificial colorants found in beers marketed in the Czech region were very low and did not show a serious risk for consumers' health.

Adsorption-regeneration by heterogeneous Fenton process using modified carbon and clay materials for removal of indigo blue.

Indigo blue dye is mainly used in dyeing of denim clothes and its presence in water bodies could have adverse effects on the aquatic system; for this reason, the objective of this study was to promote the removal of indigo blue dye from aqueous solutions by iron and copper electrochemically modified clay and activated carbon and the saturated materials were regenerated by a Fenton-like process. Montmorillonite clay was modified at pH 2 and 7; activated carbon at pH 2 and pH of the system. The elemental X-ray dispersive spectroscopy analysis showed that the optimum pH for modification of montmorillonite with iron and copper was 7 and for activated carbon was 2. The dye used in this work was characterized by infrared. Unmodified and modified clay samples showed the highest removal efficiencies of the dye (90-100%) in the pH interval from 2 to 10 whereas the removal efficiencies decrease as pH increases for samples modified at pH 2. Unmodified clay and copper-modified activated carbon at pH 2 were the most efficient activated materials for the removal of the dye. The adsorption kinetics data of all materials were best adjusted to the pseudo-second-order model, indicating a chemisorption mechanism and the adsorption isotherms data showed that the materials have a heterogeneous surface. The iron-modified clay could be regenerated by a photo-Fenton-like process through four adsorption-regeneration cycles, with 90% removal efficiency.

A simple and rapid resonance Rayleigh scattering method for detection of indigo carmine in soft drink.

A novel method that uses acridine orange (AO) to detect indigo carmine (IC) in soft drinks was developed. The method is highly sensitive and is based on a resonance Rayleigh scattering (RRS) technique. In Britton-Robinson (BR) buffer solution, pH 4.3, the weak RRS intensity of AO was greatly enhanced by the addition of IC, with the maximum peak located at 332 nm. Under optimum conditions, it was found that the enhanced RRS intensity was proportional to the concentration of IC over a range of 2-32 × 10(-6)  mol/L. A low detection limit of 2.4 × 10(-8)  mol/L was achieved. The sensitivity and selectivity of the method are high enough to permit the determination of trace amounts of IC without any significant interference from high levels of other components such as common anions and other amino acids. Finally, the concentration of IC in three different soft drinks was determined with satisfactory results. Copyright © 2016 John Wiley & Sons, Ltd.