Three-dimensional strategies in the quantitative resolution of kinetic UV absorbance measurements for monitoring the oxidation of quercetin by oxidant agents and analyzing dietary supplement product.

Three-dimensional strategies involving the application of parallel factor analysis (PARAFAC) to the kinetic UV absorbance measurements were elaborated to monitor the oxidation of quercetin with oxidant agents (K2Cr2O7 and KIO3) and to quantify analyte in a dietary supplement product. Loadings (spectral, kinetic and concentration profiles) were obtained by the PARAFAC deconvolution. Spectral identification, kinetics and quantification of the relevant analyte in the presence of interferent(s) were performed. The elaborated chemometric strategies were carefully validated to demonstrate the capability of the method. Assay results of the PARAFAC strategies were statistically compared to that of the newly developed UPLC method.

A multiway spectral analysis model to monitor the kinetic chlorination reaction of caffeine and determine its content in commercial liquid and solid drinks.

A multiway data analysis model, namely parallel factor analysis (PARAFAC) was proposed to decompose a three-way array of second-order kinetic UV measurements, for the chlorination reaction of caffeine with NaOCl, into a set of the spectra, time, and concentration matrices. The multiway resolution provided the simultaneous estimation of spectral, kinetic, and quantitative analysis of caffeine. The ability of the PARAFAC tool was checked by analyzing the validation samples in the presence of interferences. The added recovery and relative standard deviations for caffeine in the spiked samples were calculated as 99.1%-99.5% and 0.52%-1.34% for Iced Coffee Black liquid coffee (ICB), 99.5%-103.0% and 0.42%-1.03% for Jacobs Monarch Gold 100% Instant Coffee (JMG) and 99.5%-101.4% and 0.11%-0.13% for Çaykur Black Filter (Süzen) Bag Tea (BTB). Caffeine in commercial drinks was analyzed using the concentration matrices of the PARAFAC application. The PARAFAC results were statistically compared to those obtained by the developed UPLC method.

A New Ultra-Performance Liquid Chromatographic Method for the Quantification of Vitamin C in Fresh and Dried Goji Berries (Lycium barbarum L.) Cultivated in Turkey.

BACKGROUND: The potential background of the study is related to comprehensive detection of the content of vitamin C with an actual chromatographic method. OBJECTIVE: Vitamin C is of vital importance in terms of human life and health due to its polyfunctional activity such as antioxidant activity and antiviral effect with other biological functions. In this regard, it may be necessary to update analytical methods or develop up-to-date analytical methods to accurately estimate the amount of vitamin C in natural samples. In this study, a new ultra-performance liquid chromatography with photodiode array detection (UPLC-PDA) method has been developed for the determination of vitamin C content in fresh and dried goji berries (Lycium barbarum L.), which are cultivated in Turkey. METHOD: The chromatographic elution of vitamin C in natural fruit samples was achieved on an ACQUITY UPLC BEH C18 (1.7 µm, 2.1 mm × 100 mm) column using methanol and 0.1 M H3PO4 pH 2.15 (20:80, v/v), which are mobile phase. UPLC determination was done at the 242.8 nm. Flow rate was 0.20 mL/min at a column temperature of 30°C. Linearity range of the calibration graph was found to be at 5-30 µg/mL. The validity of the newly developed UPLC method was tested by analyzing individual test samples and added samples. RESULTS: Applicability of the validated UPLC method was verified by the quantitative analysis of vitamin C content in both fresh and dried goji berries. CONCLUSIONS: We believe that the newly developed and validated UPLC method would be a useful and promising approach for simple quantitative analysis of goji berry samples for vitamin C. HIGHLIGHTS: In previous studies, no UPLC-PDA method was reported for the analysis of vitamin C in goji berries. The method provided a good repeatability for the analysis of real samples.

Three-way analysis-based pH-UV-Vis spectroscopy for quantifying allura red in an energy drink and determining colorant's pKa.

Three-way analysis-based pH-UV-Vis spectroscopy was proposed for quantifying allura red in an energy drink product without the need for chromatographic analysis, and determining the colorant's pKa without using any titration technique. In this study, UV-Vis spectroscopic data matrices were obtained from absorbance measurements at five different pH levels from pH 8 to pH 12 and arranged as a three-way array (wavelength × sample × pH). In the three-way analysis procedure, parallel factor analysis (PARAFAC) was implemented to decompose the three-way array into a set of trilinear components. Each set of three components relates to spectral, pH and relative concentration profiles of allura red and sample matrix in the energy drink. First, UV-Vis spectra of the colorant's acid-base pair and sample's matrix were characterized by using the estimated spectral profile. Then, from the pH profile the pKa value was found to be 11.28 for the related colorant. Finally, allura red in energy drink samples was determined using the estimated concentration curve in the relative concentration profile. In the quantitation procedure, the working concentration range was 0.8-19.2 µg/mL. PARAFAC approach was tested in terms of selectivity, precision, and accuracy of the method. Added recovery results obtained by applying the proposed method to spiked samples were between 101.5% and 103.5%. In the application of the method to the analysis of real samples, successful results were reported. For a comparison, an ultra-performance liquid chromatographic method was developed for the quantitation of the colorant. Compared to the chromatographic method, we observed that PARAFAC model was simple and less expensive without requiring separation.

PARAFAC and MCR-ALS approaches to the pKa determination of benzoic acid and its derivatives.

In general, the identification of biological activities of a molecule requires the observation of its physicochemical characteristics with its molecular interactions in an organism. The acid-base ionization constant (or pKa) is one of the key parameters that shows the physicochemical behaviors of molecules used in pharmaceuticals, foods, cosmetics etc. Therefore, the development of new methods (or approaches) is necessary to get simple, rapid, inexpensive and reliable determination of the acidity constants of active and inactive ingredients used in commercial products. In this paper, new UV spectroscopic methods were developed for the first time, by applying parallel factor analysis (PARAFAC) and multivariate curve resolution-alternating least squares (MCR-ALS) to the pH-UV spectral data arrays for determining the pKa values of benzoic acid and its five derivatives (4-fluorobenzoic acid, thiosalicylic acid, anthranilic acid, phthalic acid, 4-aminobenzoic acid). The pH profiles obtained by the PARAFAC and MCR-ALS decomposition of the pH-UV data arrays were used for the quantitative estimation of the acid-base ionization constants for the investigated compounds without classical titration procedure. We concluded that the proposed PARAFAC and MCR-ALS provided us an opportunity for simple and rapid pKa determination of relevant compounds, which have functional importance in pharmaceutical and food industries.

Three-way analysis of pH-UV absorbance dataset for the determination of paracetamol and its pKa value in presence of excipients.

A three-way analysis method, parallel factor analysis (PARAFAC) model was applied to the pH-absorbance dataset for the simultaneous determination of paracetamol and its acid-base dissociation constant in presence of excipient interference in a syrup formulation without using chemical pretreatment or chromatographic separation step. The UV spectroscopic data matrices of calibration set, validation and unknown samples were obtained from the absorbance measurements at the five different pH media, considering conjugate acid/base properties of the related drug. Their pH-absorbance data matrices were arranged as a cubic data array (wavelength x sample x pH) (425x52x5). Three-way array of pH-absorbance dataset was decomposed into a trilinear set of spectral, pH and relative concentration profiles of paracetamol and excipients in the commercial syrup using PARAFAC model. In the PARAFAC implementation, paracetamol in the commercial syrup formulation and its pKa value were simultaneously predicted from the relative concentration and pH profiles, respectively. In the method validation step of this study, the performance of PARAFAC model was checked by analyzing the validation samples in terms of selectivity, sensitivity, accuracy and precision of the method. The determination results of paracetamol and its pKa value provided from PARAFAC application were compared to those obtained by a newly developed ultra-performance liquid chromatography (UPLC) method, in terms of simplicity, applicability, interpretability with low cost and short analysis time.

Spectrophotometric determination of various polyanions with polymeric film optodes using microtiter plate reader.

Polycation-sensitive membrane optodes based on the chromoionophore 2',7'-dichlorofluorescein octadecylester (DCFOE) have previously been developed and used for determination of heparin via a titrimetric method. In this study, it is shown that some other important polyanions such as PPS (pentosan polysulfate), DNA, xanthan, Na-alginate, and carrageenan (food additive) can also be readily determined by using DCFOE-based microtiter plate-format optodes (MPOs) and polycationic titrants that bind these polyanionic species. The optical sensors are prepared with poly(vinyl chloride) (PVC), polyurethane (PU), bis(2-ethylhexyl)sebacate (DOS), and 2',7'-dichlorofluorescein octadecylester (DCFOE) and exhibit reproducible and sensitive absorbance changes in response to the varying polycationic titrant concentrations. Three different polycations; protamine, poly-l-lysine and poly-l-arginine, are employed as titrants. The method has a detection limit of 1 µg mL(-1), and a dynamic range of 1-40 µg mL(-1). After the quantitative determinations are successfully demonstrated in buffered solutions, similar titrations are also performed in real samples. The method is validated by recovery studies in these samples. The average polyanion recoveries were quantitative [99.7(±1.3) % for pastry cream with vanillin (protamine titrant); 100.4 (±3.3) % for pastry gel with strawberry(PLA titrant), and 102.9(±2.0) % for pastry gel with strawberry (PLL titrant)].