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The purpose of this paper is to determine the amount of water in ionic liquid aqueous solutions that does not form hydrogen bonds (that is to say, free water). Here, the amount of free water was determined in mixtures of water and four ionic liquids based on the imidazolium cation: 1-Butyl-3methylimidazolium acetate, 1-Butyl-3methylimidazolium bromide, 1-Butyl-3methylimidazolium chloride, and 1-3, dimethyl-imidazolium chloride. Their ionic liquid mass fraction was between 0% and 80%. The amount of free water in the mixtures was determined from the concentration profiles obtained by analysing the near infrared spectra of the mixtures between 800 and 1070 nm using multivariate curve resolution-alternating least squares. The absorption band characteristic of the OH- group in the water is present in the spectral region considered. The analysis was done at three temperatures: 298.15, 313.15 and 333.15 K. The major conclusions obtained from a comparative analysis of the results are these: a) the length of the alkyl chain significantly affects the hydrophobicity of the cations when the molality of the ionic liquid in the solutions is higher than 1.435 mol/kg. b) for the solutions with the same cation, the amount of free water in the chloride solutions is lower than in the acetate and bromide solutions when the temperature is lower than 333.15 K. At this temperature, the capacity of acetate and bromide solutions to interact with water is the same. Between 298.15 and 333.15 K, the ionic liquid concentration at which there is no free water in the solutions ranges between 62.70% and 59.59% for the 1-3, dimethylimidazolium chloride, 66.72% and 87.75% for the 1-Butyl-3methylimidazolium chloride, 69.76% and 78.36% for the -1-Butyl-3methylimidazolium bromide and between 69.77% and 78.26% for the 1-Butyl-3methylimidazolium acetate. So, the ionic liquid with the greatest capacity to retain water is the 1-3, dimethylimidazolium chloride., (Copyright © 2019 Elsevier B.V. All rights reserved.)

This paper discusses the development and implementation of a method based on NIR spectroscopy for the in-situ determination of the ammonia mass fraction of ammonia/water mixtures in an absorber test bench. The calibration model was established using a static measuring system. A cell was designed and constructed to prepare and measure samples at the ammonia mass fractions (0.332-0.482), pressures (3.4-4.6), bar and temperatures (25.0-35.5) °C typical in absorption refrigeration systems. A quadratic model for absorbance at 1041nm was established and validated. The root-mean-square deviation (RMSD) of the results was 2.1%. To implement NIR spectroscopy in the absorber test bench, a new flow cell was designed. The calibration model was transferred and used in the conditions of the absorber test bench. In these experimental conditions, the model was statistically validated using density measurements as a reference method for measuring the ammonia mass fraction. The root-mean-square deviation between the ammonia mass fractions obtained using the two methods was 1.1%., (Copyright © 2017 Elsevier B.V. All rights reserved.)

This paper proposes a methodology based on short-wave near-infrared spectroscopy to determine the ammonia content of ammonia/water mixtures with ammonia mass fraction in the range 0.35-0.65. Establishing this methodology meant modeling the relationship between the pressure bar (15-25)bar, temperature (20-50)°C and composition of the ammonia-water in the mixture (0.35-0.65 in ammonia mass fraction) with absorbance at 1033nm. The experiments were designed to optimize experimental work. A 2(3) factorial design+3 center points was used to establish and analyze the significance of the variables in the absorbance using analysis of variance (ANOVA). A linear model for absorbance was obtained using the least squares method. The trueness of the results versus the values obtained was assessed using a reference method; density measurement was chosen for this study. The accuracy of the results in terms of root-mean-square deviation (RMSD) was 3.7%. The methodology proposed represents a fast alternative for the "in-situ" measurement of the ammonia composition of ammonia-water mixtures in absorption refrigeration systems., (Copyright © 2015 Elsevier B.V. All rights reserved.)

The photodegradation process of three azo-dyes - Acid Orange 61, Acid Red 97 and Acid Brown 425 - was monitored simultaneously by ultraviolet-visible spectroscopy with diode array detector (UV-vis-DAD) and (1)H-nuclear magnetic resonance ((1)H-NMR). Multivariate curve resolution-alternating least squares (MCR-ALS) was applied to obtain the concentration and spectral profile of the chemical compounds involved in the process. The analysis of the H-NMR data suggests there are more intermediate compounds than those obtained with the UV-vis-DAD data. The fusion of UV-vis-DAD and the (1)H-NMR signal before the multivariate analysis provides better results than when only one of the two detector signals was used. It was concluded that three degradation products were present in the medium when the three azo-dyes had practically degraded. This study is the first application of UV-vis-DAD and (1)H-NMR spectroscopy data fusion in this field and illustrates its potential as a quick method for evaluating the evolution of the azo-dye photodegradation process., (© 2013 Elsevier B.V. All rights reserved.)

A methodology based on multisyringe chromatography with a monolithic column was developed to determine three sulphonated azo textile dyes: Acid Yellow 23, Acid Yellow 9 and Acid Red 97. An ion pair reagent was needed because of the low affinity between the monolithic column and the anionic dyes. The proposed analytical system is simple, versatile and low-cost and has great flexibility in manifold configuration. The method was optimized through experimentation based on experimental design methodology. For this purpose two blocks of full factorial 2(3) were done sequentially. In the first experimental plan, the factors studied were: the % of acetonitrile in organic phase, the % of H(2)O in the mobile phase and the kind of ion pair reagent. In this stage, a simple configuration was used which has only one syringe for the mobile phase. After the first experimentation, we added a second syringe with a second mobile phase to the multisyringe module and performed a second full factorial 2(3). The factors studied in this case were: the % of acetonitrile in the second mobile phase, the pH and the concentration of ion pair reagent in both mobile phases. After this design, the optimal conditions were selected for obtaining a good resolution between the peaks of yellow dyes (1.47) and the elution of red dye in less than 8 min. The methodology was validated by spiking different amounts of each dye in real water samples, specifically, tap water, well water and water from a biological wastewater lagoon., (Copyright 2010 Elsevier B.V. All rights reserved.)

A new concept of flow titration is proposed and demonstrated for the determination of total acidity in plant oils and biodiesel. We use sequential injection analysis (SIA) with a diode array spectrophotometric detector linked to chemometric tools such as multivariate curve resolution-alternating least squares (MCR-ALS). This system is based on the evolution of the basic specie of an acid-base indicator, alizarine, when it comes into contact with a sample that contains free fatty acids. The gradual pH change in the reactor coil due to diffusion and reaction phenomenona allows the sequential appearance of both species of the indicator in the detector coil, recording a data matrix for each sample. The SIA-MCR-ALS method helps to reduce the amounts of sample, the reagents and the time consumed. Each determination consumes 0.413ml of sample, 0.250ml of indicator and 3ml of carrier (ethanol) and generates 3.333ml of waste. The frequency of the analysis is high (12 samples h(-1) including all steps, i.e., cleaning, preparing and analysing). The utilized reagents are of common use in the laboratory and it is not necessary to use the reagents of perfect known concentration. The method was applied to determine acidity in plant oil and biodiesel samples. Results obtained by the proposed method compare well with those obtained by the official European Community method that is time consuming and uses large amounts of organic solvents.

The influence of several factors in the simultaneous photocatalytic degradation of three textile dyes - Acid Red 97, Acid Orange 61 and Acid Brown 425 - has been studied using a fractional factorial design 2(5-1). The considered factors were: the initial concentration of each dye, the catalyst concentration (TiO(2)) and pH. First, we developed a rapid analytical methodology based on recording UV-visible spectra during the degradation process and a data treatment using multivariate curve resolution with alternating least squares (MCR-ALS), which enabled the three dyes to be quantified simultaneously despite the overlap of their spectra. The kinetic constant of degradation for each dye in all the experiments was evaluated. In all cases the degradation followed a first order kinetics. For a significance level of 5%, the most important factor in the photodegradation of each dye is the concentration of Acid Red 97, the degradation is more effective at higher pHs and, in the studied range, the concentration of the catalyst is not important.

The photodegradation of phenol using TiO(2) as catalyst was studied and monitored by fluorescence excitation-emission matrix (EEM). Hydroquinone, catechol and resorcinol were the dihydroxyderivative intermediates although in lower concentrations than phenol. The data were analyzed using a three-way multivariate curve resolution alternating least squares method (MCR-ALS) and augmented matrices. The procedure was assessed using synthetic samples prepared with a {4,3} Simplex-lattice design that considered a representative range of analyte concentrations. The results were analyzed in terms of overall RMSEP for the overall data set. A detailed study was made of how the analytes behaved at each concentration level and how the concentration of the other species affected the process. The method was used to quantify phenol in photodegradation samples with an overall prediction error of 5.37%. The conversion values were fitted to pseudo first-order kinetics and the apparent rate constant was calculated to be -4.9x10(-4)+/-5.2x10(-5)min(-1).

Two methods were developed for the simultaneous quantitative monitoring of photodegradation process of dibenz[a,h]anthracene (DibA), benz[a]anthracene (BaA), benz[a]pyrene (BaP) and benz[k]fluorantene (BkF) using excitation-emission fluorescence spectroscopy. Parallel factor analysis (PARAFAC) and multivariate curve resolution-alternating least squares (MCR-ALS) were satisfactory applied to the data obtained during this process. The results achieved were statistically compared by means of the joint interval test of slope and intercept, with the data obtained using the reference methodology, high performance liquid chromatography (HPLC) method. There are not significant differences between the methodologies proposed and the standard one, and may be a good alternative to the traditional methods of analysis for monitoring the degradation of these pollutants.

The application of two chemometric techniques for data structure analysis (Ward's hierarchical clustering and Principal Components Analysis) has permitted the characterization of 5th century A.D. amphora-producing centres in the Mediterranean on the basis of X-ray fluorescence data on 66 amphora fragments. The chemometric study complements and reinforces the conclusions drawn from typological and archaeological analysis. Nineteen samples of unknown origin have been classified (using the SIMCA method) into the eight proposed classes of amphora production.