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Uso de espectrometria no infravermelho médio, calibração multivariada e seleção de variáveis por intervalos na quantificação de biodieseis em misturas com diesel

Fri, 18 Mar 2016 00:00:00 GMT

Title: Uso de espectrometria no infravermelho médio, calibração multivariada e seleção de variáveis por intervalos na quantificação de biodieseis em misturas com diesel Abstract: In Brazil, since November 2014, it is required by law an addition of 7% (v/v) of biodiesel to diesel, and this mixture is called B7. According to the report issued by National Brazilian Agency of Petroleum, Natural Gas and Biofuels in 2015, 33.6% of commercial diesel samples examined presented biodiesel content outside quality specifications. Therefore, this work aims to develop and validate methodologies to quantify methyl and ethyl biodiesel from soybeans, used frying oil, cottonseed and jatropha into binary mixtures with diesel, using Mid Infrared Spectroscopy (680 to 3100 cm-1) and multivariate calibration by Partial Least Squares (PLS). Furthermore, we present a study of application of variable selection methods for intervals as Interval Partial Least Squares (iPLS), Backward Interval Partial Least Squares (biPLS) and Synergy Interval Partial Least Squares (siPLS). Thus, the models built from spectral intervals, which provided, statistically, lower Root Mean Square Error of Prediction (RMSEP) and fewer variables compared to the model of full spectrum, were validated to determine the respective type of biodiesel mixed with diesel. The results of the global PLS models, to all kinds of biodiesels, demonstrated excellent correlation between actual and predicted values of the prediction set (R > 0.99), in the range of concentration of 1.00 to 30.00% (v/v), values of RSMEP between 0.0473 and 0.1020% (v/v) and did not show systematic errors according to ASTM E1655 norm. The proposed global PLS models met the requirements of accuracy demanded by ABNT NBR15568 (RMSEP < 0.1%) besides using only one calibration model against two of the respective norm. In relation to Variable Selection methods by intervals, were efficient in the elimination of non-informative variables significantly improving the prediction of validation samples if compared to multivariate calibration by PLS models, with the exception of the models containing biodiesels from used frying oil and jatropha methyl biodiesel. Therefore, the developed methodologies are presented as a viable alternative to the usual analysis for determining the biodiesel content in mixtures as diesel.

Uso do eletrodo de diamante dopado com boro acoplado a um sistema BIA para determinação simultânea de princípios ativos em medicamentos

Fri, 26 Feb 2016 00:00:00 GMT

Title: Uso do eletrodo de diamante dopado com boro acoplado a um sistema BIA para determinação simultânea de princípios ativos em medicamentos Abstract: The present work describes the development of new analytical procedures using Batch Injection Analysis (BIA) with amperometric detection and boron-doped diamond (BDD) as working electrode. This procedure was used for simultaneous determination of active ingredients present in four commercial pharmaceutical formulations: (1) nimesulide (NIM) and paracetamol (PAR); (2) promethazine (PRO) and codeine (COD); (3) amiloride (AMD) and furosemide (FMD); (4) sulfamethoxazole (SMX), trimethoprim (TMP) and phenazopyridine (FZP). All developed analysis procedures remained stable (RSD < 2.5%), linear (R > 0,996), fast (until 74 injections h-1) and with low detection limits (mg L-1): NIM (0.299); PAR (0.293); PRO (0.065); COD (0.135); AMD (0.130); FMD (0.940); FZP (0.050); SMX (0.200) and TMP (0.150).

Desenvolvimento de procedimentos de digestão de biodiesel assistidos por radiação ultrassônica visando à determinação de metais por técnicas eletroquímicas

Wed, 16 Dec 2015 00:00:00 GMT

Title: Desenvolvimento de procedimentos de digestão de biodiesel assistidos por radiação ultrassônica visando à determinação de metais por técnicas eletroquímicas Abstract: This thesis presents the use of ultrasonic radiation for the digestion of biodiesel samples (B100) for the determination of metal ions by electrochemical stripping techniques (potentiometric and voltammetric) using a glassy-carbon electrode modified with a mercury film. Biodiesel samples (50 mg) were subjected to digestion in glass tubes with a mixture of 3.0 mL of concentrated HCl and 4.4 ml H2O2 (30%), placed in an ultrasonic bath (40 kHz and 120 W) exactly on the higher intensity region (piezoelectric) of the ultrasound and sonicated for 40 min at room temperature (~ 20°C). These parameters were optimized using the chemometric technique of factorial design for the analysis of biodiesel samples spiked with ethanolic standard solutions of zinc, cadmium, lead and copper. Recovery values between 97 and 107% were observed in the optimal conditions found to zinc, cadmium, lead and copper. Residual carbon content (RCC) values after digestions were in the range of 3.05 to 3.75%. The simultaneous determination of zinc, cadmium, lead and copper using anodic stripping voltammetry revealed limit of detection (LD) values of 44 ng kg -1; 30 ng kg -1; 145 ng kg -1; 96 ng kg -1, respectively. Additionally, biodiesel samples (100 mg) were also treated in glass tubes with a mixture of 1.59 mL concentrated HCl and 3.0 ml H2O2 (30%) under sonication of an ultrasonic probe (sonication time 12.5 min, 25% amplitude, pulse of 5.0 s and time interval of 2.0 s). The parameters were also optimized employing the chemometric technique of factorial design for the analysis of spiked samples. Recovery values between 95 and 104% were observed in the satisfactory condition for zinc, cadmium, lead and copper. RCC values after digestions comprised values between 0.43 to 0.54%. For the simultaneous determination of zinc, cadmium, lead and copper using anodic stripping voltammetry obtained in the digestates employing the ultrasonic probe, the LD values found respectively for zinc, cadmium and copper were 25 ng kg -1 and for lead 56 ng kg -1. All results obtained using assisted digestion by ultrasonic bath and / or ultrasonic probe indicate that the proposed methods for the biodiesel sample preparation presents a comparable performance to traditional methods of digestion using acid blends, or yet digestions assisted by microwave radiation.

Utilização de derivados de Moringa oleifera Lam para produção de biodiesel e obtenção de aditivos antioxidantes

Fri, 31 Jul 2015 00:00:00 GMT

Title: Utilização de derivados de Moringa oleifera Lam para produção de biodiesel e obtenção de aditivos antioxidantes Abstract: This work presents the use of the oil extracted from seeds and the leaves of Moringa oleifera Lam for the production of biodiesel and ethanol extracts, respectively. The extracted oil was characterized to give yield of 33% (w / w), saponification number of 179 mg KOH g-1, kinematic viscosity of 44.5 mm2s-1, acid value of 13.2 mg KOH g-1, peroxide value of 10.4 meq kg-1, water content of 840 ppm and oxidative stability > 60 hours. This oil was used for biodiesel production in a two-step catalysis, acid (H2SO4) and alkaline (KOH) in methanol, to yield ester 96.8% (w/w) being the predominant ester oleic (81. 6%), kinematic viscosity of 4.5 mm2s-1, acid number of 0.21 mg KOH g-1, density of 882.5 kg m-3, the water content of 257.3 ppm and stability oxidation of 19.3 h, which is the last highlight parameter compared to other biodiesels presenting not greater than 4-6 h. The ethanol extracts of Moringa leaves were evaluated for their antioxidant activity (total phenols, proanthocyanidin content, by the method of DPPH radical sequestration and differential pulse voltammetry) and used as additives to various types of biodiesel, and it was checked the increase in oxidative stability of all biodiesels with superior efficiency in comparison with the synthetic antioxidant tert-butylhydroquinone (TBHQ). Furthermore, it was produced in larger quantity methyl biodiesel from Moringa oleifeira Lam refined oil of Indian origin, which, due to its reduced acidity (0.13 mg KOH g-1), did not require a two-step catalysis (only alkaline reaction). The corrosivity of the biodiesel was assessed by immersion tests (3, 7, 14, 21, 28, 56 and 84 days) with two types of carbon steel (AC1015 and AC4140) in the absence and presence of TBHQ antioxidant in 500 ppm, at room temperature in the dark and without agitation (static testing). The presence of TBHQ led to smaller variations of peroxide index and induction period values and at the same time decreased the corrosion of the metallic coupons (indicated by the low content of iron released to biodiesel in comparison with control experiments). Furthermore, in the absence of TBHQ, the variations of the same parameters were low during the corrosion experiments, which indicated compatibility of Moringa oleifera Lam biodiesel with the evaluated steels.