Spectrophotometric determination of carminic acid in human plasma and fruit juices by second order calibration of the absorbance spectra–pH data matrices coupled with standard addition method

A rapid colorimetric method for the detection of carminic acid in samples based on visible color change

Carminic Acid (CA), an insect-derived red color, is widely used as a colorant and additive in food and non-food items. The detection of CA is of great concern since it is unacceptable for vegetarians and vegans consumers. Therefore, it is important for food authorities to have a rapid detection method for CA. We describe here a simple and rapid method for the qualitative detection of CA, using Pb2+ for complex formation. As a result, the sample solution shows a visible change from pink to purple (bathochromic shift) which could also be analyzed through a spectrophotometer at λmax = 605 nm. The structure of the CA-Pb2+ complex was also studied through advanced spectroscopic techniques. Moreover, the presence of iron results in the formation of a stable CA-Fe2+ complex without any significant color change, as Fe2+ has a stronger binding affinity with CA. Thus, sodium fluoride (NaF) was used to prevent CA-Fe2+ complex formation. Therefore, two methods were developed based on the absence (method I) and presence (method II) of NaF. The LOD and LOQ for the method I was 0.0025 and 0.0076 mg mL-1, and for method II, values were 0.0136 and 0.0415 mg mL-1, respectively. The methods were also validated by intra and inter-day analyses. A total of 45 commercials, including food and non-food samples, were screened for the detection of CA. The developed methods are applicable for the effective and rapid surveillance of CA in various samples without the use of high-tech instruments.

Interference-free quantitation of aromatic amino acids in two complex systems by three-way calibration with ultraviolet-visible spectrophotometer: Exploration of trilinear decomposition of spectrum-pH data

Aromatic amino acids play an extremely important role in life activities and participate in many biological processes. Their concentration levels are associated with a variety of diseases, such as phenylketonuria and colorectal cancer. Therefore, the quantification of aromatic amino acids is an important task. In the present work, a novel and rapid three-way analytical method was proposed to detect the levels of aromatic amino acids in prostate cancer cells (PC3 cells) and Dulbecco's modified minimal essential medium (DMEM cell culture), by using the affordable ultraviolet-visible spectrophotometer. First, spectrum-pH second-order data were designed per sample; Second, properties of the resulted spectrum-pH-sample three-way data were investigated by utilizing the parallel factor analysis (PARAFAC), alternating trilinear decomposition (ATLD), and constrained alternating trilinear decomposition (CATLD) algorithms, and a flexible scanning approach for determining the constraint parameters of CATLD was proposed; Third, a three-way calibration method based on the CATLD algorithm with the proposed scanning approach was developed for interference-free quantification of aromatic amino acids in these systems. The average relative predictive errors of validation (ARPEV) for phenylalanine, tyrosine, and tryptophan were 1.4%, 3.0%, and 0.7% in prostate cancer cells, and ARPEV for phenylalanine, tyrosine, and tryptophan were 4.1%, 1.2%, and 0.7% in DMEM cell culture. The predicted contents of tyrosine and tryptophan in DMEM cell culture were 64.2 ± 2.9 μg mL^-1, 5.6 ± 0.3 μg mL^-1, there are no significant differences in the concentrations between the developed analytical method and high performance liquid chromatography method. The proposed spectrum-pH-sample three-way calibration method based on CATLD algorithm can provide an interesting analytical strategy with high selectivity and accuracy for ultraviolet-visible spectrophotometer.

Sensitive voltammetric quantification of carminic acid in candies using selenium dioxide nanoparticles based electrode

Carminic acid is a food colorant which concentration has to be controlled due to the possible negative health effects. Sensitive voltammetric method is developed for carminic acid determination using electrode modified with SeO₂ nanoparticles (SeO₂ NPs) and hexadecyltriphenylphosphonium bromide (HDTPPB) acting as dispersive agent for nanoparticles and electrode surface co-modifier. SeO₂ NPs of 37-45 nm are uniformly distributed at the electrode increasing its electroactive area (41 ± 2 vs. 8.9 ± 0.2 mm² for bare glassy carbon electrode (GCE)). Electrochemical impedance spectroscopy data confirm an 18.3-fold decrease of charge transfer resistance compared to GCE (12.7 ± 0.3 vs. 232 ± 7 kΩ, respectively). In differential pulse mode, the linear dynamic ranges of carminic acid are 0.010-2.5 and 2.5-10 μmol L^-1 with a detection limit of 3.4 nmol L^-1. The method is successfully employed in candies and lozenges for sore throat treatment. The approach is simple, reliable, and can be used as an alternative to chromatography in routine analysis.

Recent advantages in electrochemical monitoring for the analysis of amaranth and carminic acid food colors

This study provides a comprehensive review of the latest developments in the electrochemical impressions of the important dyestuffs including amaranth and carminic acid. Food colors are organic substances that have important effects on human health and food safety. While these substances do not pose a problem when used in the daily intake (ADI) amounts, they harm human health when consumed excessively. Amaranth and carminic acid are synthetic and natural food colors ingredients, respectively. Analysis of these substances in food, pharmaceutical, cosmetic and textile samples is extremely important because of their genotoxicity, cytostatic and cytotoxic effects. Electroanalytical methods, which have great advantages over traditional analytical methods, shed light on the scientific world. Electrochemical monitoring modules, which are fast, simple, accurate, reliable, and highly selective, are promising for the determination of both substances. Until now, amaranth and carminic acid food determinations have been carried out successfully with electrochemical monitoring techniques in many numbers in the literature. Voltammetric techniques are the most widely used among these electroanalytical methods. In particular, square wave and differential pulse voltammetric techniques, which have extraordinary properties, have been heavily preferred. Limits of detection (LOD) comparable to the standard analytical method have been achieved using these methods, which have very quick analysis durations, high precision and accuracy, do not require long preprocessing, and have great selectivity. In addition, more sensitive and selective analyses of amaranth and carminic acid in natural samples were carried out with numerous indicator electrodes. The merits of powerful electrochemical monitoring studies for the determination of both food colors during the last decade are presented in this study. Moreover, parameters such as analytical applications, detection limits, electrochemical methods, selectivity, working electrodes, and working ranges are summarized in detail.

Multilinear Mathematical Separation in Chromatography

Chromatography is a powerful and generally applicable method for the analytical separation and quantification of the chemical constituents in complex mixtures because chromatographic separation can provide high selectivity by isolating all analytes from interferences. Multiway analysis based on the multilinear model is an increasingly widely used method for interference-free and fast determination of the chemical constituents also in complex mixtures because multilinear mathematical separation can provide high selectivity by extracting the pure signal of the analyte from the mixed signal of a real sample. By combining chromatographic separation with mathematical separation, multiway calibration method, multiway standard additions method, and multiway internal standard method can be established. Chromatography assisted by multiway analysis can reduce the requirements for complete chromatographic separation, save elution time, and decrease the consumption of the mobile phase, particularly when the peak coelution problem is difficult to solve. This review presents the fundamentals and analytical applications of multilinear mathematical separation in chromatography.

Determination of Carminic Acid in Foodstuffs and Pharmaceuticals by Microchip Electrophoresis with Photometric Detection

This paper presents a novel miniaturized analytical method for the determination of carminic acid, a natural red food dye, in complex food and pharmaceutical matrices by microchip electrophoresis (MCE) with photometric detection. MCE has become a very attractive microscale separation technique because it offers high-speed, high-throughput, small sample injection volume and low reagents consumption. Fast determination of carminic acid in less than 5 min was achieved on a poly(methyl methacrylate) microchip in anionic separation mode at pH 6. Photometric detector based on light-emitting diode technology was set to a wavelength of 490 nm. Using a sample injection volume of 900 nL, a limit of detection of 69 nmol L−1 was achieved. A wide linear dynamic range over four orders of magnitude (from nmol L−1 to mmol L−1) was observed for peak area. Developed method provided favorable intra- and inter-day repeatability of the migration time (up to 2.5% RSD), as well as the repeatability of the peak area (less than 1.9% RSD), regardless of the sample type. The content of carminic acid was determined in various foodstuffs and pharmaceuticals, such as candies, saffron, non-alcoholic drink, and sore throat lozenges with good recoveries (92.5–104.0%).

Dispersive Micro-Solid Phase Extraction for Sensitive Determination of Methotrexate from Human Saliva Followed by Spectrophotometric Method

For biological assessing of hospital personnel occupationally exposed to antineoplastic drugs, highly sensitive and accurate methods are required. Methotrexate (MTX) is an anticancer agent that is widely used in a variety of human cancers. For the first time, dispersive-micro solid phase extraction (D-µ-SPE) has been applied for determination of low levels of MTX in saliva samples. The method is based on rapid extraction of MTX using graphene oxide adsorbent. The sample preparation time is decreased by the fact that the adsorbent dispersed in the sample solution and extraction equilibrium can be reached very fast. This significant feature which obtained with this method is of key interest for routine trace laboratory analysis. The influence of different variables on D-µ-SPE was investigated. Under optimum conditions, the calibration graph was linear over the range of 10-1000 ng/ml. The relative standard deviations are better than 9.0%. The proposed method was successfully applied for the determination of MTX in patient samples.

Using post-column infused internal standard assisted quantitative metabolomics for establishing prediction models for breast cancer detection

RATIONALE

Breast cancer is one of the most common cancers among women and its associated mortality is on the rise. Metabolomics is a potential strategy for breast cancer detection. The post-column infused internal standard (PCI-IS)-assisted liquid chromatography/tandem mass spectrometry (LC/MS/MS) method has been demonstrated as an effective strategy for quantitative metabolomics. In this study, we evaluated the performance of targeted metabolomics with the PCI-IS quantification method to identify women with breast cancer.

METHODS

We used metabolite profiling to identify 17 dysregulated metabolites in breast cancer patients. Two LC/MS/MS methods in combination with the PCI-IS strategy were developed to quantify these metabolites in plasma samples. Detection models were built through the analysis of plasma samples from 176 subjects consisting of healthy volunteers and breast cancer patients.

RESULTS

Three isotope standards were selected as the PCI-ISs for the metabolites. The accuracy was within 82.8-114.16%, except for citric acid and lactic acid at high concentration levels. The repeatability and intermediate precision were all lower than 15% relative standard deviation. We have identified several metabolites that indicate the presence of breast cancer. The area under the receiver operating characteristics (AUROC) curve, sensitivity and specificity of the linear combinations of metabolite concentrations and age with the highest AUROC were 0.940 (0.889-0.992), 88.4% and 94.2% for pre-menopausal woman, respectively, and 0.828 (0.734-0.922), 73.5% and 85.1% for post-menopausal women, respectively.

CONCLUSIONS

The targeted metabolomics with PCI-IS quantification method successfully established prediction models for breast cancer detection. Further study is essential to validate these proposed markers.

Comparison of different fluorescence techniques in brandy classification by region of production

Fluorescence spectrometry coupled with chemometrics was used to discriminate between 44 brandies originating from different countries. The kind of spectrum (emission, total luminescence and synchronous fluorescence), the geometry of sample illumination (front-face and right angle), and the sample type (bulk and diluted) were considered to compare the brandy classification. Firstly, the emission and synchronous fluorescence spectra (SFS) were processed by the principal component analysis (PCA) and the excitation-emission matrix (EEM) fluorescence spectra were modeled by unfolded PCA and parallel factor analysis (PARAFAC). Secondly, the scores of PCA/PARAFAC components were used in the linear discriminant analysis (LDA). Finally, the quality of the PCA-LDA and PARAFAC-LDA models was compared. Total correct classification using emission spectra was poor, regardless of the experimental conditions. The highest total correct classification (95.5%) was achieved by processing the SFS recorded at wavelength difference of 20 and 60nm on the diluted samples. However, 90.9% observed for bulk samples and their SFS at wavelength difference of 20nm in the right angle geometry as well as EEM fluorescence spectra in both geometries is still an acceptable result.

A novel mixed hemimicelles dispersive micro-solid phase extraction using ionic liquid functionalized magnetic graphene oxide/polypyrrole for extraction and pre-concentration of methotrexate from urine samples followed by the spectrophotometric method

Methotrexate (MTX) is an anticancer drug that is widely used in a variety of cancers including primary central nervous system lymphoma. It is also administrated in the treatment of some autoimmune diseases. A simple, accurate, sensitive, and precise mixed hemimicelles dispersive micro-solid phase extraction was proposed for MTX quantification in human urine samples. MTX was quantified by spectrophotometer after dispersive micro-solid phase extraction using ionic liquid functionalized magnetic graphene oxide/polypyrrole. Interactions of adsorbent and MTX were modeled by molecular docking and the interaction energy was predicted to be -8.35 kcal/mol. A larger absolute value of binding energy represents larger adsorption strength, indicating that graphene oxide nanosheets could perform higher adsorption strength toward MTX. The concentrations of MTX were proportional to analytical response in amounts ranging from 10 to 1000 ng/mL with a good correlation (R² = 0.99). Inter- and intra-day precisions and accuracies were within the acceptable limit according to FDA guideline (15% for biological determination). The recoveries were ranging from 89 to 93% and the method was specific for routine analysis of MTX. This protocol was applied to the urine of two patients under MTX therapy received an intravenous administration of 1 mg/kg/dose of MTX with acute lymphoblastic leukemia. The accuracy of the method was confirmed by HPLC measurements.

Dye-Sensitized Solar Cells Prepared with Mexican Pre-Hispanic Dyes

A dye-sensitized solar cell (DSSC) is a photovoltaic device capable of generating electrical power from the absorption of solar radiation. These cells use a SnO2 : F/TiO2/dye heterojunction as the active electrode (working electrode). Active electrodes containing TiO2 in the anatase crystalline phase and synthetic dyes are used to achieve high conversion efficiencies. Synthetic dyes, whether organic or organometallic compounds, have the disadvantage of being expensive. For this reason, many efforts are made worldwide to find natural dyes with lower production costs that can be used in the fabrication of DSSCs. Nocheztli is a natural red dye obtained from the cochineal insect Dactylopius coccus; the dye dates from pre-Hispanic times and contains high levels of carminic acid (CA). Nocheztli has been used in Mexico in textile dyeing from pre-Hispanic times to the present. Carmine is an organometallic dye with two molecules of carminic acid and one atom of aluminum in its structure; it is obtained by the interaction of the carminic acid from Nocheztli with aluminum salts. Carminic acid and carmine molecules contain a carboxyl group in their structure, allowing them to anchor to TiO2, creating a suitable heterojunction to prepare DSSCs. In this study, both dyes are used to sensitize the mesoporous TiO2m semiconductor to prepare DSSCs.

Multiway analysis methods applied to the fluorescence excitation-emission dataset for the simultaneous quantification of valsartan and amlodipine in tablets

In this study, excitation-emission matrix datasets, which have strong overlapping bands, were processed by using four different chemometric calibration algorithms consisting of parallel factor analysis, Tucker3, three-way partial least squares and unfolded partial least squares for the simultaneous quantitative estimation of valsartan and amlodipine besylate in tablets. In analyses, preliminary separation step was not used before the application of parallel factor analysis Tucker3, three-way partial least squares and unfolded partial least squares approaches for the analysis of the related drug substances in samples. Three-way excitation-emission matrix data array was obtained by concatenating excitation-emission matrices of the calibration set, validation set, and commercial tablet samples. The excitation-emission matrix data array was used to get parallel factor analysis, Tucker3, three-way partial least squares and unfolded partial least squares calibrations and to predict the amounts of valsartan and amlodipine besylate in samples. For all the methods, calibration and prediction of valsartan and amlodipine besylate were performed in the working concentration ranges of 0.25-4.50μg/mL. The validity and the performance of all the proposed methods were checked by using the validation parameters. From the analysis results, it was concluded that the described two-way and three-way algorithmic methods were very useful for the simultaneous quantitative resolution and routine analysis of the related drug substances in marketed samples.

A stepwise approach for the detection of carminic acid in saffron with regard to religious food certification

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).

Second-order data obtained by beta-cyclodextrin complexes: a novel approach for multicomponent analysis with three-way multivariate calibration methods

This research reports the first application of β-cyclodextrin (β-CD) complexes as a new method for generation of three way data, combined with second-order calibration methods for quantification of a binary mixture of caffeic (CA) and vanillic (VA) acids, as model compounds in fruit juices samples. At first, the basic experimental parameters affecting the formation of inclusion complexes between target analytes and β-CD were investigated and optimized. Then under the optimum conditions, parallel factor analysis (PARAFAC) and bilinear least squares/residual bilinearization (BLLS/RBL) were applied for deconvolution of trilinear data to get spectral and concentration profiles of CA and VA as a function of β-CD concentrations. Due to severe concentration profile overlapping between CA and VA in β-CD concentration dimension, PARAFAC could not be successfully applied to the studied samples. So, BLLS/RBL performed better than PARAFAC. The resolution of the model compounds was possible due to differences in the spectral absorbance changes of the β-CD complexes signals of the investigated analytes, opening a new approach for second-order data generation. The proposed method was validated by comparison with a reference method based on high-performance liquid chromatography photodiode array detection (HPLC-PDA), and no significant differences were found between the reference values and the ones obtained with the proposed method. Such a chemometrics-based protocol may be a very promising tool for more analytical applications in real samples monitoring, due to its advantages of simplicity, rapidity, accuracy, sufficient spectral resolution and concentration prediction even in the presence of unknown interferents.

Determination of the food dye carmine in milk and candy products by differential pulse polarography

As a basis for the development of a sensitive analytical method for the determination of carmine food dye, a study of the differential pulse polarographic reduction of carminic acid (CA) on a dropping mercury electrode was performed. For the analytical differential pulse polarographic method running at pH 2.0 Britton-Robinson (B-R) buffer solution (peak at -489 mV), the relationship between the peak current and CA concentration was linear in the range of 1 μM to 90 μM with a detection limit of 0.16 μM. The proposed electrochemical procedure was successfully applied to the determination of carmine food dye in spiked commercially available strawberry flavored milk. The method was extended to the determination of CA in candy and results were in agreement with that obtained by a spectrophotometric comparison method. A cyclic voltammogram of CA in 2.0 B-R buffer electrolyte was obtained on the dropping mercury electrode at pH 2.0 during potential scans from 0.00 mV to 1000 mV versus Ag/AgCl. From repetitive cyclic voltammograms, one cathodic peak at -500 mV and three anodic peaks on the reverse scan between approximately -340 mV and -460 mV were recorded. The influences of some other commonly found inorganic and organic salts on the determination of CA were also examined. The sufficiently good recoveries and low standard deviations for the data reflect the high accuracy and precision of the proposed differential pulse polarographic method.