An electronic tongue for simultaneous determination of Ca2+, Mg2+, K+ and NH4+ in water samples by multivariate calibration methods.

In this study, a multi ion-selective electrode system was developed for simultaneous determination of Ca2+, Mg2+, K+ and NH4+ ions. The system, called electronic tongue, was used for the quantitative determination of these ions in different water samples. The measurement system was comprised of sixteen ion-selective electrodes, an Ag/AgCl double-junction reference electrode, and a sixteen-channel multi-potentiometer. In the fabrication process of the electronic tongue, an electrode body, which comprised eight ion-selective electrodes together on it, was designed. The obtained data were evaluated by using multivariate calibration methods such as Classical Least Squares (CLS), Principal Component Regression (PCR) and Partial Least Squares (PLS1). The parameters that influence the electronic tongue performance were investigated. Analyses were conducted in synthetic water samples and real water samples. Percentage recovery values in synthetic samples, which were calculated via PLS1, were found 101.35%, 102.41%, 100.04% and 99.23% for Ca2+, Mg2+, K+ and NH4+ respectively. The results, obtained from the electronic tongue and other analytical techniques, were compared and no significant difference was found between the results at 95% confidence level.

Synchronous fluorescence spectroscopy combined with chemometrics for rapid assessment of cold-pressed grape seed oil adulteration: Qualitative and quantitative study.

This paper describes the feasibility of synchronous fluorescence (SyF) spectroscopy combined with multivariate data analysis for qualitative and quantitative determination of adulteration of cold pressed grape seed oil (GSO) with refined soybean oil (SBO). SyF spectroscopy data of oil samples were collected in the region of 250-800 nm at excitation-emission wavelength differences (∆λ) of 10, 20, 30, 40, 50, 60, 70 and 80 nm. Three different multivariate methods, namely principal component analysis (PCA), soft independent modeling of class analogies (SIMCA) and partial least square regression (PLSR) analysis were used for data analysis. To simulate the adulteration of cold pressed GSO with refined SBO, ninety-six adulterated samples were prepared at adulterant levels from 5% to 50%. HPLC-FLD method was used as reference in order to authenticate pure oils and binary oil mixtures. The SIMCA models provided an excellent classification for pure cold pressed GSO versus other vegetable oil samples, with a 95% significance level. The classification error rate of SyF spectroscopy for detecting SBO added to GSO was also better than 5%. PLSR calibration models constructed for the evaluation of GSO purity and for the adulterants SBOs were internally validated by the leave-one-out procedure (cross-validation) and their predictive ability was assessed by independent external validation sets. Under the optimum conditions, the plots of observed versus predicted values exhibited a good linearity (R2 > 0.99). The root mean square errors of calibration (RMSEC) and cross-validation (RMSECV) were in the range 0.55-4.46% and 2.14-5.35%, respectively. Excellent predicting capabilities were also obtained using an external validation set consisting of GSO adulterated with SBOs from different brands.

Application of central composite design for the optimization of electrode surface composition for glucose biosensor fabrication.

The use of a central composite design (CCD) for the optimization of electrode surface composition and its application to develop an amperometric glucose biosensor as a model system are described. A five-level three-factorial CCD was applied to determine the optimum electrode surface composition for three critical variables: amounts of carboxylated multiwall carbon nanotubes (c-MWCNT), titanium dioxide nanoparticles (TiO2NP), and glucose oxidase (GOx). The statistical significance of the model and factors were evaluated using the variance analysis (ANOVA) at 95% of confidence level. The optimized electrode surface composition was used for the fabrication of the glucose biosensor. The resulting biosensor showed linear response to glucose from 2.0 × 10-5 to 1.9 × 10-3 M with a detection limit of 2.1 × 10-6 M and sensitivity of 168.5 µA mM-1 cm-2 under optimal experimental conditions. Analytical performance parameters of the biosensor were also compared with those obtained with the glucose biosensors fabricated using the electrode compositions optimized by conventional one factor-at-a-time method and 22 CCD (for c-MWCNT and TiO2NP amounts). The optimization of the critical variables, achieved by CDD, leads us to fabricate the glucose biosensor in the best electrode surface composition which was promoted by the improved analytical performance. The proposed biosensor was applied to the analysis of glucose in serum samples and the obtained results were well correlated with the results of reference method. Graphical abstract ᅟ.

Simultaneous determination of copper and zinc in brass samples by PCR and PLS1 methods using a multiple ion-selective electrode array.

A method was developed to determine copper and zinc simultaneously in brass sample using a multiple ion-selective electrode array system and multivariate calibration techniques. The multiple ion-selective electrode array system was consisted of one pH electrode and eight ion selective electrodes which were formed using commercial ionophores and which are mainly sensitive copper and zinc. PCR, PLS1 which are multivariate calibration techniques were used to calibrate the multiple ion-selective electrode array system using five level multivariate calibration design and PCR method was selected as most suitable method. The measurements were performed at pH 10 in ammonia-ammonium chloride buffer. Copper and zinc content of a brass sample were determined by the calibrated multiple ion-selective electrode array system and the composition of brass sample was also determined by gravimetric method. The percentage amount of copper and zinc in brass sample were 64 ±â€¯1 and 26 ±â€¯2, respectively using the gravimetric method. The percentage results obtained in brass samples for copper and zinc were 63 ±â€¯3 and 24 ±â€¯3 by PCR method and 60 ±â€¯5 and 20 ±â€¯7 by PLS1 method, respectively. The obtained results were calculated for a 95% confidence level.