Adulterants in biodiesel/diesel blends modifies its physical and chemical properties. In this work, Fourier Transform Mid-Infrared spectrometry (FT-MIR) and multivariate control charts based on Net Analyte Signal (NAS) were used to monitor the quality of Crambe methyl biodiesel in relation to the biodiesel content and the presence of adulterants. The calibration model was constructed from the decomposition of the instrumental signals of the calibration samples into three vectors: NAS, interference and residual. From these vectors, three control charts were built: (i) NAS chart to monitor the analyte of interest (Crambe methyl biodiesel); (ii) Interference chart to monitor the data matrix (all components in diesel without the analyte of interest); and (iii) Residual chart to monitor any non-systematic variations. To validate the calibration model, other groups of B10, BX and B10 samples adulterated by direct addition of soybean oil and used fry oil in the range of 4.85-30.13% (v/v) were used. All samples prepared in-quality specifics were correctly classified as “in-quality control” samples, and other samples were correctly classified as “out-of-quality control” samples. Therefore, the methodology developed proved to be efficient in monitoring the quality of this fuel and it can be used by supervisory and quality control agencies.

Resumo A vigilância da concentração de flúor na água de abastecimento público visa garantir o equilíbrio entre o benefício (prevenção de cárie) e risco (fluorose dental) dos programas da fluoretação de água. O objetivo deste estudo foi verificar a precisão de dois métodos analíticos no monitoramento da concentração de flúor na água de abastecimento público de uma cidade brasileira. O checklist STROBE foi utilizado para auxiliar na condução desta pesquisa e relatar os resultados. Tratou-se de um estudo observacional analítico, de caráter prospectivo utilizando a água de abastecimento de Uberlândia, MG. Foram coletadas 126 amostras de água, em 21 pontos, durante seis meses seguidos e analisadas por meio do método com eletrodo íon seletivo (F-SIE) e por colorimetria com o SPADNS. A análise estatística foi realizada de maneira descritiva, em seguida, empregou-se o teste ANOVA e o teste t de Student para amostras pareadas. Os resultados mostraram que o método eletrométrico mostrou menor coeficiente de variação (12,3%) quando comparado o método colorimétrico (57,4%). Não foi observada variação significativa da concentração de fluoreto na água avaliada pelo F-ISE e SPADNS. Conclui-se que o método eletrométrico deve ser de primeira escolha para ser utilizado por laboratórios que monitoram a concentração de flúor nas águas de abastecimento público.

Abstract The surveillance of the concentration of fluoride in the public water supply aims to ensure the balance between the benefits (carie prevention) and risk (dental fluorosis) of water fluoridation programs. The aim of this study was to check the accuracy of two analytical methods for monitoring the concentration of fluoride in the public water supply of a Brazilian city. The STROBE checklist was used to aid the conduction of this study and report the results. It was an analytical, observational, and prospective study using the water supply of Uberlândia, MG, Brazil. We collected 126 water samples at 21 sites for six consecutive months and analyzed them using the fluoride ion selective electrode (F-ISE) method and colorimetry with SPADNS. The statistical analysis was performed descriptively and then the ANOVA and Student t-test for paired samples were applied. The results showed that the F-ISE method had a lower coefficient of variation (12.3%) than the SPADNS method (57.4%). There was no significant variation of the fluoride concentration in the water through the supply network evaluated either by F-ISE as SPADNS. We concluded that the electrometric method should be the first choice for use by laboratories that monitor fluoride concentration in the public supply water.

The production of methyl esters via transesterification reaction of triacylglycerides of macaúba and palm kernel oils, with subsequent atmospheric distillation and separation of six fractions of the produced biodiesel, corresponding to 60% of its initial volume, is reported. The composition in esters of the produced biodiesel, its fractions and remaining residue of the distillation was determined by gas chromatography. This analytical procedure has allowed to monitor the content in esters for each distilled fraction. The fractions richer in C8:0, C10:0, C12:0, C14:0 is intended to be used as an aviation fuel, in blends with the Jet-A1 biokerosene. The residues from the distillation with higher molecular weights than those corresponding to esters C16:0, C18:0 and C18:1 are destined to other combustion engines as any conventional biodiesel. For the biodiesel obtained from the macaúba kernel, this distillation led to an enrichment from 45.86% to up to 74.35% in the C12:0 ester. For the palm kernel biodiesel, the corresponding enrichment was from 66.76% up to 82.96%. Through this simple distillation, it was thus possible to effectively enrich, in C8:0 to C14:0 esters, the initial crude biofuel, with an efficiency of 30% for the macaúba and 11.5% for the palmiste biodiesel.

This paper presents methodologies for monitoring the quality of methyl cotton biodiesel in biodiesel/diesel blends using mid-infrared spectroscopy (MIR) and chemometrics tools. The first method relates to the construction of multivariate control charts with the aim of qualitatively monitoring the samples according to the Brazilian specification for biodiesel in the biodiesel/diesel blends (7.00 ± 0.5% v/v of biodiesel). The second concerns the construction of partial least squares (PLS) to determine the content of the biodiesel in the biodiesel/diesel blend. The PLS model was validated from multivariate figures of merit according to the guidelines of ASTM E1655-05 and IUPAC. The results from both methods were satisfactory for both qualitative and quantitative monitoring. Therefore, the proposed methodologies for monitoring the quality of biodiesel in biodiesel/diesel blends are fast, practical, economical and efficient and can be used by industries and service stations.

O objetivo deste trabalho foi determinar o coeficiente de expansão térmica do biodiesel a partir de dados experimentais de densidade em função da temperatura. Para tanto, foram utilizados alguns fundamentos da termodinâmica. O valor obtido para o coeficiente de expansão térmica após regressão linear para o biodiesel foi de 8,49 × 10-4 ºC-1, com um coeficiente de correlação igual a 0,9978.

The purpose of this study was to determine the coefficient of thermal expansion of the biodiesel from the experimental data of density as a function of temperature. For this, we used some fundamentals of thermodynamics. The value obtained for the coefficient of thermal expansion after the linear regression for biodiesel was 8.49 × 10-4 ° C-1, with a correlation coefficient equal to 0.9978.