Scanner Digital Images Combined with Color Parameters: A Case Study to Detect Adulterations in Liquid Cow’s Milk

This study presents a proposition of a low-cost screening method for detection and quantification of adulterations in liquid cow’s milk samples. The studied adulterations were made with water and NaOH. Digital images from the adulterated samples were obtained using a flatbed scanner, and the means of ten color parameters were used to evaluate the information from images: red, green, blue, hue, saturation, value, relative colors (r, g, and b), and intensity. Regression models for water quantification were proposed using multiple linear regression (MLR), principal components regression (PCR), and partial least squares (PLS). The best models were obtained using PCR and PLS, with root mean square error for prediction smaller than 7%. These results were compared with near-infrared (NIR), and the prediction capability was very similar. In the case of adulterations with NaOH, the colors B, S, g, and b presented the highest differences between fresh and adulterated milk samples.     

Comparison of the univariate and multivariate methods in the optimization of experimental conditions for determining Cu, Pb, Ni and Cd in biodiesel by GFAAS

Experimental design was used as a tool to define the optimum pyrolysis and atomization temperatures for four analytes (Cu, Pb, Ni and Cd) in biodiesel samples. Two chemical modifiers (Pd + Mg and W) and two distinct sample preparation procedures (microemulsion and wet digestion in a focused microwave system) were also investigated. The pyrolysis and atomization temperatures were optimized using 2⁴ factorial design for Cu, Pb, Ni and Cd, with 16 assays carried out for each analyte. The results for Cu and Pb indicated that variables of sample preparation for digestion by focused microwave was the most important one for both analytes. The pyrolysis and atomization temperatures applied were 1000 °C and 2200 °C for Cu and 500 °C and 2000 °C for Pb. None of the variables analyzed here were important for Ni, and the pyrolysis and atomization temperatures chosen for this element were 800 °C and 2300 °C. A different factorial design was used for Cd. The variables of medium and modifier were not important for this element, and the lowest temperatures, Tp-500 °C and Ta-1400 °C, were chosen based on this second design. The importance of factorial design in the simultaneous optimization of several variables studied by GFAAS was confirmed, for it involves fewer experiments and hence, lower costs, greater speed and higher efficiency.     

Removal of Cr(VI) from Wastewater of the Tannery Industry by Functionalized Mesoporous Material

Silicon - A previously synthesized PABA-MCM-41 mesoporous material was used to remove Cr(VI) in leather samples. The optimization step was performed using univariate method for the following...     

Sequential Determination of Cd, Cu and Pb in Tea Leaves by Slurry Introduction to Thermospray Flame Furnace Atomic Absorption Spectrometry

A simple procedure for the sequential determination of Cd, Cu and Pb in tea leaves by slurry introduction to thermospray flame furnace atomic absorption spectrometry was developed. Detection limits were 0.05 mg?kg^?1 for Cd, 2.1 mg?kg^?1 for Cu and 0.68 mg?kg^?1 for Pb using 0.67 % (m/v) slurries (100 mg/15 mL).     

<Superscript>1</Superscript>H NMR and Multivariate Calibration for the Prediction of Biodiesel Concentration in Diesel Blends

In this work, the use of ¹H-NMR spectroscopy and a statistical approach to the analysis of biodiesel concentrations in blends with conventional diesel is described. For this, we performed ¹H-NMR analyses using distinct mixtures of biodiesel from soybean and castor oil in mineral diesel, in concentrations ranging from 0.5 to 30%, and then we applied partial least squares regression (PLS) and principal components regression (PCR) to such data. So, six models were designed and they were evaluated through statistical parameters and through the analysis of four samples prepared in the laboratory. Briefly, a PLS model, obtained through the selection of aromatic, aliphatic and methoxy spectral regions, was quite suitable for the prediction of biodiesel concentrations greater than 2.0%. Deviations of real and predicted values were found to B2 commercial blends, indicating that this model can only be applied to blends exceeding a 2.0% level of biodiesel in petroleum diesel. In conclusion, the ¹H-NMR-PLS method is fairly useful for the quality control of biodiesel–diesel blends, whose commercialisation has increased in the last few years.     

Evaluation of Different Sample Preparation Procedures Using Chemometrics: Comparison Among Photo-Fenton Reaction,Microwave Irradiation,and Direct Determination of Minerals in Fruit Juices

In this work, an exploratory study about the mineral characteristic of some fruit juice (passion fruit, pineapple, orange, and grape) applying chemometric tools was made. The juices analyzed were separated in different groups by principal components analysis and hierarchical components analysis in accordance with their minerals contents. Barium, C, Ca, K, Mg, Mn, Na, and Sr were determined by inductively coupled plasma optical emission spectrometry. Addition and recovery methods were used for confirmation of the results. The recovery range for microwave sample preparation was from 81% (for K) to 111% (for Mn), for photo-Fenton from 102% (for Ca e Mg) to 128% (for Na), and the direct analysis, without sample preparation step, from 96% (for K) to 139% (for Mn). A new method based on photo-Fenton reaction coupled with microwave radiation for juice decomposition was proposed; the obtained results were satisfactory and compatible with the conventional methods of analysis in accordance with Student’s statistic t test and chemometric tools.     

Direct Determination of Ca,K and Mg in Cassava Flour Samples by Laser-Induced Breakdown Spectroscopy (LIBS)

This study aims to develop a method for direct determination of Ca, K, and Mg in cassava flour samples by laser-induced breakdown spectroscopy (LIBS). LIBS instrumental parameters were evaluated using factorial design with a central point. The variables evaluated were delay time (0.0; 1.0 and 1.8 μs) and fluence (81; 2037 and 4074 Jcm^?2): both were tested in three different values. The best results obtained were with a delay time of 1.8 μs and a fluence of 4074 Jcm^?2. The proposed calibration model obtained using LIBS data presented a good correlation with reference values obtained by inductively coupled plasma atomic emission spectrometry (ICP OES). The predictive capabilities, based on the standard error of validation (SEV), were 117, 530 and 77 mg kg^?1 for Ca, K, and Mg, respectively. The proposed LIBS method was applied to the analysis of 90 cassava flour samples, and the results showed concentrations of Ca, K, and Mg of 352–1845, 1285–3187, and 320–1242 mg kg^?1, respectively.     

Rapid detection and quantification of milk adulteration using infrared microspectroscopy and chemometrics analysis

The application of attenuated total reflectance mid-infrared microspectroscopy (MIR-microspectroscopy) was evaluated as a rapid method for detection and quantification of milk adulteration. Milk samples were purchased from local grocery stores (Columbus, OH, USA) and spiked at different concentrations of whey, hydrogen peroxide, synthetic urine, urea and synthetic milk. Samples were place on a 192-well microarray slide, air-dried and spectra were collected by using MIR-microspectroscopy. Pattern recognition analysis by Soft Independent Modeling of Class Analogy (SIMCA) showed tight and well-separated clusters allowing discrimination of control samples from adulterated milk. Partial Least Squares Regression (PLSR) showed standard error of prediction (SEP) ∼2.33, 0.06, 0.41, 0.30 and 0.014 g/L for estimation of levels of adulteration with whey, synthetic milk, synthetic urine, urea and hydrogen peroxide, respectively. Results showed that MIR-microspectroscopy can provide an alternative methodology to the dairy industry for screening potential fraudulent practice for economic adulteration of cow’s milk.     

Antenna pattern synthesis utilizing spherical Bessel functions

Pattern synthesis of linear antennas utilizing the spherical Bessel functions is presented. This leads to antenna current distribution by the Legendre polynomials of the first kind, which are of finite support. Some examples are given to illustrate this procedure