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The incorporation of pigments and natural polyphenols into inorganic matrices, resulting in a hybrid material that improves the resistance and chemical stability of the pigments and the antioxidant capacity of the materials, has been of great interest to the pharmaceutical, chemical and food industries. The aim of this work was to prepare and characterize a bifunctional pigment–antioxidant nanomaterial-based carminic acid-decorated solid core-mesoporous shell silica nanoparticles, evaluating its properties as a pigment, its antioxidant capacity and its properties as a chemical stabilizer of emulsions. The chemical stability of oil-in-water (O/W) Pickering emulsions was evaluated determining the stability of vitamin E solubilized in the oil phase. Carminic acid was attached through the action of coupling ethylcarbodiimide hydrochloride (EDC)/N-hydroxysuccinimide (NHS) agents, and the resulting spherical and homogeneous nanoparticles showed a diameter close to 175 nm. A notorious change of emulsion color was observed by the addition of the nanomaterial. Emulsions showed an attractive pink color, and when the pH was adjusted to pH 3 and pH 9, a change in color was observed, analogous to carminic acid in solution. The nanomaterial incorporation also improved chemical stability, decreasing vitamin E consumption to 9.26% of the initial value, demonstrating an important antioxidant effect of the developed nanomaterial.

Carminic acid, a natural hydrophilic dye extensively used in the food and cosmetic industries, is converted in hydrophobic dyes by acetylation or pivaloylation. These derivatives are successfully used as biocolourants for rubber objects. In this paper, spectroscopic properties of the carminic acid derivatives in dimethyl sulfoxide and in polybutylacrylate are studied by means of photoluminescence and time-resolved photoluminescence decays, revealing a hypsochromic effect due to the presence of bulky substituents as the acetyl or pivaloyl groups. Molecular mechanics and density functional theory calculations confirm the disruption of planarity between the sugar ring and the anthraquinoid system determined by the esterification.

The stepwise approach takes advantage of simple, versatile, low-cost screening tools that can be applied to several posts of the saffron trade chain to specifically detect adulteration with carminic acid (CA). This natural dye is of insect origin and should not be present in Kosher and Halal foods such as saffron. For gross adulteration levels (>25.0%, w/w) reaction with diphenylamine-sulfuric acid was found adequate to indicate the presence of extraneous matter but not its identity. FT-IR analysis of the dry material combined with chemometrics served to rapidly sort out samples containing >10.0% CA without any sample pretreatment except grinding. Aqueous extracts prepared according to ISO 3632-2 were then examined by tristimulus colorimetry and derivative UV–Vis spectrometry to detect adulteration down to the level of 2.0% (w/w). Determination of CA down to 0.2%, w/w was achieved by RP-HPLC-DAD using aqueous acetonitrile elution solvent (pH = 2.8). [ABSTRACT FROM AUTHOR]

Abstract Background Cochineal dye is used worldwide as a red coloring in foods, drinks, cosmetics, quasi-drugs, and drugs. The main component of the red color is carminic acid (CA). Carmine is an aluminum- or calcium-chelated product of CA. CA and carmine usually contain contaminating proteins, including a 38-kDa protein thought to be the primary allergen. Severe allergic reactions manifest as anaphylaxis. The aim of this study was to review all Japanese reported cases and propose useful diagnostic chart. Methods All reported Japanese cases of cochineal dye-induced immediate allergy were reviewed, and newly registered cases were examined by skin prick test (SPT) with cochineal extract (CE) and measurement of CE and carmine-specific serum IgE test. Two-dimensional (2D) western blotting using patient serum was conducted to identify the antigen. Results Twenty-two Japanese cases have been reported. SPT and the level of specific IgE test indicated that six cases should be newly registered as cochineal dye allergy. All cases were adult females, and all cases except three involved anaphylaxis; 13 cases involved past history of local symptoms associated with cosmetics use. Japanese strawberry juice and fish-meat sausage, and European processed foods (especially macarons made in France) and drinks were recent major sources of allergen. 2D western blotting showed that patient IgE reacted to the 38-kDa protein and other proteins. Serum from healthy controls also weakly reacted with these proteins. Conclusions SPT with CE and determination of the level of CE and carmine-specific IgE test are useful methods for the diagnosis of cochineal dye allergy. Graphical abstract Image 1 [ABSTRACT FROM AUTHOR]

Abstract: The use of surface‐enhanced Raman scattering methods for the quantitative determination of different molecular species is not trivial as many parameters seriously affect the outcome of any experiment. In this work, we use as a case study the quantitative analysis of ionic organics dyes. We report on the role of different molecular properties to the modulation of the surface‐enhanced Raman scattering signal, the useful dynamic range for the determination, the dynamics of the molecule‐nanoparticle interaction process, and the time dependency of the signal. The consequences on the quantitative determination on dye mixtures, often found in the analysis of artworks, are discussed. [ABSTRACT FROM AUTHOR]

To accurately determine carminic acid (CA) and its derivative 4-aminocarminic acid (4-ACA), a novel, high-performance liquid chromatography with photodiode array detector (HPLC/PDA) method using relative molar sensitivity (RMS) was developed. The method requires no analytical standards of CA and 4-ACA; instead it uses the RMS values with respect to caffeine (CAF), which is used as an internal standard. An off-line combination of 1H-quantitative nuclear magnetic resonance spectroscopy (1H-qNMR) and HPLC/PDA was able to precisely determine the RMSs of CA274nm/CAF274nm and 4-ACA274nm/CAF274nm. To confirm the performance of the HPLC/PDA method using RMSs, the CA and 4-ACA contents in test samples were tested using four different HPLC-PDA instruments and one HPLC-UV. The relative standard deviations of the results obtained from five chromatographs and two columns were less than 2.7% for CA274nm/CAF274nm and 1.1% for 4-ACA274nm/CAF274nm. The 1H-qNMR method was directly employed to analyse the CA and 4-ACA contents in test samples. The differences between the quantitative values obtained from both methods were less than 5% for CA and 3% for 4-ACA. These results demonstrate that the HPLC/PDA method using RMSs to CAF is a simple and reliable quantification method that does not require CA and 4-ACA certified reference materials. [ABSTRACT FROM AUTHOR]

The chemical composition of the scale insect Dactylopius coccus was analyzed with the aim to discover new possible intermediates in the biosynthesis of carminic acid. UPLC-DAD/HRMS analyses of fresh and dried insects resulted in the identification of three novel carminic acid analogues and the verification of several previously described intermediates. Structural elucidation revealed that the three novel compounds were desoxyerythrolaccin- O -glucosyl ( DE- O -Glc p ), 5,6-didehydroxyerythrolaccin 3- O -β-D-glucopyranoside ( DDE-3- O -Glc p ), and flavokermesic acid anthrone ( FKA ). The finding of FKA in D. coccus provides solid evidence of a polyketide, rather than a shikimate, origin of coccid pigments. Based on the newly identified compounds, we present a detailed biosynthetic scheme that accounts for the formation of carminic acid ( CA ) in D. coccus and all described coccid pigments which share a flavokermesic acid ( FK ) core. Detection of coccid pigment intermediates in members of the Planococcus (mealybugs) and Pseudaulacaspis genera shows that the ability to form these pigments is taxonomically more widely spread than previously documented. The shared core- FK -biosynthetic pathway and wider taxonomic distribution suggests a common evolutionary origin for the trait in all coccid dye producing insect species. [ABSTRACT FROM AUTHOR]

The nature of the pigments or dyes used to dye the first Portuguese postage stamps has remained unknown until now. In this work, a study has been made of the inks used for red, rose, purple and orange colors in a selected number of Portuguese postage stamps from the period 1857 to 1909. This is based on analysis involving a variety of techniques (X-ray fluorescence, UV-Vis spectroscopy, HPLC-MS/HPLC-DAD, steady and time resolved fluorescence). It was found that the inks included, among others, the inorganic pigments cinnabar (HgS), lead oxide (Pb3O4) and chromate (PbCrO4), lead sulphide (PbS), and the organic compounds carminic acid and Eosin Y. The study demonstrated a non-destructive analysis method for identification of two molecules of color involving the UV-Vis (for carminic acid and Eosin Y) and fluorescence spectra, together with quantum yields and lifetimes (for Eosin Y). [ABSTRACT FROM AUTHOR]

We have developed a colorimetric chemosensor for the selective and sensitive detection of Cys based on the complex (CA-2Pb) between a commercially available natural organic dye, carminic acid (CA) and Pb in pure aqueous solution at physiological pH. The addition of Cys to the CA-2Pb solution resulted in a distinct color change from purple to red together with a remarkable absorption spectral change by the restoration of CA through a displacement mechanism with formation of the Cys-Pb complex, whereas other amino acids and glutathione induce no or minimal spectral and color changes. Moreover, the other amino acids and GSH do not affect the detection ability of CA-2Pb for Cys. The reversibility even through several cycles was established for practical applications. The results indicate that CA-2Pb may be useful as a potential colorimetric and naked-eye chemosensor for Cys over Hcy and GSH in aqueous solution. [ABSTRACT FROM AUTHOR]

Recently, rare-earth elements (REEs) have attracted great interest due to their importance in several fields, such as the high-technology and medicine industries. Due to the recent intensification of the use of REEs in the world and the resulting potential impact on the environment, new analytical approaches for their determination, fractionation and speciation are needed. Diffusive gradients in thin films are a passive technique already used for sampling labile REEs, providing in situ analyte concentration, fractionation and, consequently, remarkable information on REE geochemistry. However, data based on DGT measurements until now have been based exclusively on the use of a single binding phase (Chelex-100, immobilized in APA gel). The present work proposes a new method for the determination of rare earth elements using an inductively coupled plasma‒mass spectrometry technique and a diffusive gradients in thin films (DGT) technique for application in aquatic environments. New binding gels were tested for DGT using carminic acid as the binding agent. It was concluded that acid dispersion directly in agarose gel presented the best performance, offering a simpler, faster, and greener method for measuring labile REEs compared to the existing DGT binding phase. Deployment curves obtained by immersion tests in the laboratory show that 13 REEs had linearity in their retention by the developed binding agent (retention x time), confirming the main premise of the DGT technique obeying the first Fick's diffusion law. For the first time, the diffusion coefficients were obtained in agarose gels (diffusion medium) and carminic acid immobilized in agarose as the binding phase for La, Ce, Pr, Nd, Sm, Eu, Gd, Dy, Ho, Er, Tm, Yb and Lu, which were 3.94 × 10−6, 3.87 × 10−6, 3.90 × 10−6, 3.79 × 10−6, 3.71 × 10−6, 4.13 × 10−6, 3.75 × 10−6, 3.94 × 10−6, 3.45 × 10−6, 3.97 × 10−6, 3.25 × 10−6, 4.06 × 10−6, and 3.50 × 10−6 cm2 s−1, respectively. Furthermore, the proposed DGT devices were tested in solutions with different pH values (3.5, 5.0, 6.5 and 8) and ionic strengths (I = 0.005 mol L−1, 0.01 mol L−1, 0.05 mol L−1 and 0.1 mol L−1 – NaNO 3). The results of these studies showed an average variation in the analyte retention for all elements at a maximum of approximately 20% in the pH tests. This variation is considerably lower than those previously reported when using Chelex resin as a binding agent, particularly for lower pH values. For the ionic strength, the maximum average variation was approximately 20% for all elements (except for I = 0.005 mol L−1). These results indicate the possibility of a wide range of the proposed approach to be used for in situ deployment without the use of correction based on apparent diffusion coefficients (as required for using the conventional approach). In laboratory deployments using acid mine drainage water samples (treated and untreated), it was shown that the proposed approach presents excellent accuracy compared with data obtained from Chelex resin as a binding agent. [Display omitted] • For the first time a new ligand was developed for sampling REEs by DGT. • The biding agent is based on immobilizing carminic acid directly in agarose gel. • The diffusion coefficient was determined utilizing agarose as diffusive layer. • Effects of pH and ionic strength on uptake of REEs were evaluated. • The proposed approach was successfully applied for analysis of DAM samples. [ABSTRACT FROM AUTHOR]

In this study, hybrid pigments based on carminic acid (CA) were synthesized and applied in polymer materials. Modification of aluminum-magnesium hydroxycarbonate (LH) with CA transformed the soluble chromophore into an organic-inorganic hybrid colorant. Secondary ion mass spectroscopy (TOF-SIMS), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), thermogravimetric analysis (TGA), scanning electron microscopy (SEM), and UV-Vis spectroscopy were used to study the structure, composition, and morphology of the insoluble LH/CA colorant. Successful modification of the LH was confirmed by the presence of interactions between the LH matrix and molecules of CA. XPS analysis corroborated the presence of CA complexes with Mg2+ ions in the LH host. The batochromic shift in UV-Vis spectra of the organic-inorganic hybrid colorant was attributed to metal-dye interactions in the organic-inorganic hybrid colorants. Strong metal-dye interactions may also be responsible for the improved solvent resistance and chromostability of the modified LH. In comparison to uncolored ethylene-norbornene copolymer (EN), a modified EN sample containing LH/CA pigment showed lower heat release rate (HRR) and reduced total heat release (THR), providing the material with enhanced flame retardancy.

Carminic acid (CA), a member of natural dyes, is well known for its good stability in a variety of foods such as candies, drinks, and fruits. However, it has never been authorized as a food additive in meat products. In order to detect CA with high sensitivity and specificity, an indirect competitive enzyme-linked immunosorbent assay (ic-ELISA) has been developed. A high-titer polyclonal antibody (Pab) against CA was obtained after the immunization of New Zealand white rabbits with conjugate of CA coupling with BSA. Several physicochemical factors including pH value, ionic strength, and organic solvent were tested, and it was observed that the ELISA working solution was pH 7.4 PBS buffer containing 50 mmol L Na. Under the optimal conditions, 50% inhibitive concentration (IC) of CA was 95.2 ng mL and the limit of detection (LOD) was 1 ng mL. Cross-reactivity of the Pab toward carmine was 108.7%, and no response was found with other four edible colorants. The spiked meat samples were detected by ic-ELISA with intra- and inter-assay recovery ranges of 79.1-103.1 and 81.6-98.8%, respectively. Finally, the results for the fortified food samples were further confirmed by high-performance liquid chromatography (HPLC) with a high correlation coefficient of 0.927, which demonstrated that the method in the study was sensitive enough for the quantification of CA in meat products. [ABSTRACT FROM AUTHOR]

The commercially available natural organic dye, carminic acid (CA), an anthraquinone derivative bearing hydroxyl and carboxyl groups as recognition sites was found to be a colorimetric probe for Pb in perfect aqueous solution under neutral conditions with specific selectivity and high sensitivity. Upon addition of Pb, the absorption maximum of CA showed a large red shift, and the resulted color change from red to purple could be easily identified even by the naked eye. The chemical stoichiometric ratio between CA and Pb was determined to be 1:2 through Job plot, Pb titration, and kinetic experiments. Moreover, other environmental relevant metal ions induced no or minimal spectral and color changes. The reversibility of Pb to CA with EDTA even through several cycles was established for practical applications. The results indicated that CA can be a good candidate for simple, convenient and reversible colorimetric detection of Pb in aqueous solution even though it was hard to be applied to determine Pb on the water testing by US EPA. [ABSTRACT FROM AUTHOR]

Background: Color change in artworks has been commented on for centuries. Fading of watercolor pigments is a notable alteration. Pigments based on carminic acid are among those particularly prone to color loss, but the mechanism and factors are not well understood. Results: We painted out three pigments prepared from the aqueous extract of carminic acid (CA) from Dactylopius coccus: the uncomplexed, and aluminium- and tin-complexed lakes. These were applied in a 2% gum Arabic solution to papers that were acidic, neutral or alkaline pH and exposed to accelerated light aging in a weatherometer. The comparative rate of fading was dependent on the complexation and on the pH of the substrate. On alkaline paper, the Al complex was least light stable, on neutral paper the three colorants responded similarly, and on acidic paper the tin complex was the least light stable. This is discussed in light of the published information on reactions and mechanism of color loss of CA. [ABSTRACT FROM AUTHOR]

The use of synthetic dyes for laccase induction in vivo has been scarcely explored. We characterized the effect of adding different synthetic dyes to liquid cultures of Pycnoporus sanguineus on laccase production. We found that carminic acid (CA) can induce 722 % and alizarin yellow 317 % more laccase than control does, and they promoted better fungal biomass development in liquid cultures. Aniline blue and crystal violet did not show such positive effect. CA and alizarin yellow were degraded up to 95 % during P. sanguineus culturing (12 days). With this basis, CA was selected as the best inducer and used to evaluate the induction of laccase on solid-state fermentation (SSF), using sugarcane bagasse (SCB) as substrate, in an attempt to reach selective delignification. We found that laccase induction occurred in SSF, and a slight inhibition of cellulase production was observed when CA was added to the substrate; also, a transformation of SCB under SSF was followed by the C cross polarization magic angle spinning (CPMAS) solid-state nuclear magnetic resonance (NMR). Results showed that P. sanguineus can selectively delignify SCB, decreasing aromatic C compounds by 32.67 % in 16 days; O-alkyl C region (polysaccharides) was degraded less than 2 %; delignification values were not correlated with laccase activities. Cellulose-crystallinity index was increased by 27.24 % in absence of CA and 15.94 % when 0.01 mM of CA was added to SCB; this dye also inhibits the production of fungal biomass in SSF (measured as alkyl C gain). We conclude that CA is a good inducer of laccase in liquid media, and that P. sanguineus is a fungus with high potential for biomass delignification. [ABSTRACT FROM AUTHOR]

• Removal of Carminic acid dye from wastewater is important because of its carcinogenic and neurotoxic effects. • The biosorbent potential of Prunus mahaleb L. shell was investigated for the first time in this study. • The biosorption data were consistent with the Langmuir isotherm model and the maximum adsorption capacity was found to be 148 mg/g. • The biosorption process was found to be consistent with the pseudo-second-order kinetic model and intraparticle diffusion. • According to the thermodynamic parameters, the biosorption was found to be endothermic and spontaneous. This study focused on the performance of Prunus mahaleb shell (MS) agricultural waste, which is used as an alternative biosorbent for carminic acid (CA) removal from aqueous solution. The effects of different parameters such as pH, initial dye concentration, contact time, biosorbent dosage and temperature on the biosorption of CA dye to the MS biosorbent surface were investigated. The characterization of the biosorbent was done by FT-IR, SEM-EDX and pzc analyses. It was determined that the isotherm and kinetics of CA dye removal were consistent with the Langmuir isotherm and PSO and IPD kinetic models, respectively. The maximum adsorption capacity was calculated as 148 mg g−1 according to the Langmuir isotherm. According to the ΔH0, ΔG0 and ΔS0 results, the biosorption was found to be endothermic and spontaneous. Based on these data, it is concluded that environmentally friendly, inexpensive, simple to use and effective MS biosorbent can be used for CA dye removal. [ABSTRACT FROM AUTHOR]

The image of Our Lady of Copacabana, a gilded polychrome sculpture carved in maguey wood in 1583, is one of the most important devotions in the Americas. In former research, we have identified the use of gypsum, Armenian bole, cerussite and atacamite in its polychromy. In this study, a red sample taken from the Virgin's tunic and a blue sample extracted from the cloak have been analysed with the aim to identify both pigments and offer insights into the painting technique. Analysis by micro-Raman spectroscopy complemented with scanning electron microscopy–energy dispersive spectroscopy and high-performance liquid chromatography allowed the identification of carmine lake in the red sample. Analysis by micro-Raman spectroscopy of the surface of the blue sample and its cross section showed the presence of smalt—the blue-glass pigment—over a cerussite layer, bathed by a very thin ultramarine layer—from a probable native origin—following a pictorial tradition that would last even until the eighteenth century. This is the first time that lapis lazuli has been scientifically identified in a Spanish American colonial painted layer.This article is part of the themed issue ‘Raman spectroscopy in art and archaeology’. [ABSTRACT FROM AUTHOR]

Abstract Cochineal, carminic acid, carmines (E 120) have been previously evaluated by JECFA and by the SCF. Both committees established an ADI of 5 mg/kg bw/day. The Panel noted that the title of the EC specifications for E 120 does not adequately correspond to the specified food additive and therefore, proposes to modify it to “E 120 cochineal extract, carminic acid and carmines”, which would more accurately reflect the material used. The Panel also noted that the specifications need to be updated with regard to the maximum limits for certain toxic elements present as impurities, to ensure that E 120 will not be a significant source of exposure to these toxic elements in food. No ADME studies on cochineal extract, carminic acid or carmines were available for evaluation, but indirect evidence suggests that carmines are absorbed and distributed in the body. Acute, short‐term, subchronic, carcinogenicity, reproduction and developmental toxicity studies conducted in rats or mice did not show toxicological potential. Consideration of the available information regarding genotoxicity indicated that carminic acid is not genotoxic. The Panel concluded that the present dataset does not give reason to revise the ADI of 5 mg carmine (containing approximately 50 % carminic acid)/kg bw, allocated by the SCF in 1983. The Panel concluded that this ADI should be expressed as carminic acid content, which would correspond to 2.5 mg carminic acid/kg bw/day. The Panel considered that, since no threshold dose can be established for allergic reactions, it is advisable that exposure to the eliciting allergens, such as proteinaceous compounds, in E 120 is avoided by introducing appropriate purification steps in the manufacturing process. Refined exposure estimates show that exposure to E 120 for the non‐brand‐loyal scenario, is below the ADI of 2.5 mg carminic acid/kg bw/day for all population groups.

The spectroscopic study was performed on 9,10-anthraquinone derivatives (purpurin, alizarin, carminic acid, and 2-(hydroxymethyl)-9,10-anthraquinone) in dimethylsulfoxide in the presence of triethylamine to bring information on their protonation/deprotonation equilibria in aprotic solvent. An interesting deprotonation effect of 5,5-dimethyl-1-pyrroline N -oxide (a spin trapping agent used in the EPR experiments) was revealed. The quantum chemical calculations enabled the identification of the individual protonated/deprotonated tautomeric forms present in the experimental systems. The UV photoexcitation of hydroxyanthraquinones (HAQ) led to the generation of reactive radical species and singlet oxygen, detected by in situ EPR spectroscopy (spin trapping, nitroxide radical elimination, oxidation of sterically hindered amines). The changes in the electronic absorption spectra upon photoexcitation, linked with the ability of the studied HAQ to generate reactive oxygen species upon exposure, confirm a substantial effect of the substituent character and position on the overall photochemical behavior of the HAQ, significantly influenced by the actual experimental conditions (solvent, pH). [ABSTRACT FROM AUTHOR]

Hybrid materials based on one organic dye, the carminic acid, and montmorillonite have been prepared and characterized by a multi-technical approach. Aluminum and tin II cations were used in the experimental mixtures in order to have a chelating effect with the carminic acid. X-Ray diffraction patterns (XRD) did not highlight any intercalation of the organic molecule in the interlayer space, a result confirmed by transmission electron microscopy (TEM) micrographs. The fixation of the organic molecules on the phyllosilicates was then investigated by 13 C solid state nuclear magnetic resonance (NMR) and time resolved fluorescence spectroscopies. The spectra showed the role that the ketone and catechol functions of the dye played for its fixation and stressed on the decrease of its mobility when the lake pigment was formed. The role of the clay edges and/or surface was highlighted by this set of experimental data. [ABSTRACT FROM AUTHOR]

In this work a combined chromatographic and spectroscopic approach is used to provide a diagnostic assessment of semi-synthetic ammoniacal cochineal through the syntheses of its dyes and lakes according to art historical recipes. Commercially introduced in the late XIX century as a dye and pigment, it was used to obtain a brilliant purplish/violet nuance which provided a more stable option over carminic acid although its evidenced use in manufacts and artworks of heritage importance have been scarcely documented. Through HPL C -DAD, it has been possible to identify 4-aminocarminic acid as the main component of ammoniacal cochineal highlighting a chemical formula analogous to acid stable carmine, a recent patented food dye. FTIR clearly distinguishes the amine group in the ammoniacal cochineal dye preparation and TLC-SERS allows for an adequate separation and spectral differentiation in its main components to be evidenced. Colloidal SERS has permitted spectral markers useful in discerning ammoniacal cochineal over carminic acid to be highlighted and discussed. Finally, the methods experimented in this study for the identification of ammoniacal cochineal have been validated on analyzing a sample of dyed wool. [ABSTRACT FROM AUTHOR]

Using the carminic acid assay, we determined the concentration of boron in oilfield waters. We investigated the effect of high concentrations of salts and dissolved metals on the assay performance. The influence of temperature, development time, reagent concentration, and water volume was studied. Ten produced and flowback water samples of different origins were measured, and the method was successfully validated against ICP-MS measurements. In water-stressed regions, produced water is a potential source of fresh water for irrigation, industrial applications, or consumption. Therefore, boron concentration must be determined and controlled to match the envisaged waste water reuse. Fast, precise, and onsite measurements are needed to minimize errors introduced by sample transportation to laboratories. We found that the optimum conditions for our application were a 5:1 mixing volume ratio (reagent to sample), a 1 g L −1 carminic acid concentration in 99.99% sulfuric acid, and a 30 min reaction time at ambient temperature (20 °C to 23 °C). Absorption values were best measured at 610 nm and 630 nm and baseline corrected at 865 nm. Under these conditions, the sensitivity of the assay to boron was maximized while its cross-sensitivity to dissolved titanium, iron, barium and zirconium was minimized, alleviating the need for masking agents and extraction methods. [ABSTRACT FROM AUTHOR]

The fundamental chemistry underlying the photo-induced degradation of cochineal (carmine), a red dye extracted from South American scale insects and used as an artist colorant, and its stability in solution and as a lake pigment in different paint media exposed to light in various ambient environments is examined. The influence of oxygen on the photodegradation was examined for dye solutions and for solid paint samples containing the lake pigment, and the effect of ambient humidity was assessed for the paint samples. The degradation was followed using absorbance spectroscopy, and characterized using IR and LC-MS. Results indicate lower reaction rates of the carminic acid chromophore in solution and in oil paints during light exposure in anoxic conditions; whereas watercolor paints demonstrated a stronger dependence of the rates on the ambient humidity. A ring opening of the anthraquinone core is suggested in the breakdown of the dye and pigment. This study illustrates that solution phase systems may serve as simple models to assess the kinetics and mechanism of photochemical breakdown of organic-based pigments in solid samples. [ABSTRACT FROM AUTHOR]

A novel modified electrode has been developed, by electrodeposition of Pd–Au bimetallic nanoparticles (Pd–AuNps) on a polypyroline coated (Poly(Pr)) graphite electrode (GE). The structure and morphologies of Pd–AuNps/Poly(Pr)/GE were characterized by cyclic voltammetry (CV), square wave voltammetry (SWV), electrochemical impedance spectroscopy (EIS), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX) and X-ray photon spectroscopy (XPS) techniques. The electrocatalytic activities and morphologies of the new electrode were compared with individual monometallic AuNps/Poly(Pr)/GE and PdNps/Poly(Pr)/GE. This new bimetallic nanoparticle modified electrode (Pd–AuNps/Poly(Pr)/GE) was evaluated for determination of carminic acid. The oxidation peak (0.750 V) of carminic acid was found to be linearly related to carminic acid concentration in the range of 1.0 × 10 − 8 to 1.0 × 10 − 6 M with a detection limit of 5.90 × 10 − 9 M. The proposed method was simple, less time consuming and showed a high sensitivity. [ABSTRACT FROM AUTHOR]

In a weak acidic Britton–Robinson (B–R) buffer of pH 4.0, human serum albumin (HSA) can react rapidly with carminic acid (CAA) to form a supramolecular complex. Microelectrostatic fields in the molecular structure of HSA cause the electrostatic binding reaction of the positively charged CAA with the negatively charged HSA. CAAhas a sensitive, second order derivative linear sweep voltammetric reductive peak at – 0.54 V (vs. SCE) on a dropping mercury electrode (DME). After the addition of HSA to a CAAsolution, the reductive peak current of CAAdecreased without a shift of the peak potential. Based on the decrease of the peak current, a sensitive voltammetric method for the determination of microamounts of the protein is proposed. The conditions for the binding reaction and the voltammetric detection were optimized. Under the optimal conditions, the decrease of the voltammetric detection were optimized. Under the optimal conditions, the decrease of the voltammetric peak current was in proportion to the quantity of HSA in the range of 2.0 to 70.0 mg l-1, with a linear regression equation DIp”(nA) = 11.74 C (mg l-1)–12.33 and a detection limit of 2.0 mg l-1 (3s). The method was further applied to the detection of different kinds of proteins, such as bovine serum albumin (BSA), oval albunim (OVA), lipase, etc. The established method was further applied to the determination of the albumin content in human serum samples and the results obtained by this method were in good agreement with the traditional Coomassie Brilliant Blue G-250 (CBB G-250) spectrophotometric method. The binding mechanism is discussed and the binding ratio was calculated from the voltammetric data.