Determinação espectrofotométrica simultânea de cobre e ferro em álcool etílico combustível com reagentes derivados da ferroína

In the present work three ferroin reagents were studied for the simultaneous spectrophotometric determination of iron and copper: 1,10-phenanthroline, 2,2'-bipyridine and 2,4,6-tri(2-pyridyl)-1,3,5-triazine. Effect of pH, conditions, order reagent addition, interferences, amount of reagents, lineal range, sensitivity and stability of each system were compared. The 2,4,6-tri(2-pyridyl)-1,3,5-triazine can be used for determination of iron in the presence of copper with a detection limit of 5 µg L-1 and coefficient of variation of 2.0%; However it was not possible to determine directly copper in the presence of iron with this reagent. 1,10-phenanthroline can be used for simultaneous determination of the metallic ions with detection limits of 7 and 8 mg L-1 and coefficients of variation of 1.8 and 2.3% in the determination of iron and copper, respectively. The results showed also that 2,2'-bipyridine can be used for simultaneous determination of the metallic ions with detection limits of 11 and 32 µg L-1 and coefficients of variation of 1.9 and 2.5% in the determination of iron and copper, respectively. The reagents were used for spectrophotometric determination of iron and copper in ethanol fuel.

Construção e aplicação de biossensores usando diferentes procedimentos de imobilização da peroxidase de vegetal em matriz de quitosana

Biosensors were developed by immobilization of gilo (Solanum gilo) enzymatic extract on chitosan biopolymers using three different procedures: glutaraldehyde, carbodiimide/glutaraldehyde and epichlorohydrin/glutaraldehyde. The best biosensor performance was obtained after the immobilization of peroxidase on chitosan with epichlorohydrin/glutaraldehyde. Linear analytical curves for hydroquinone concentrations from 2.5x10-4 to 4.5x10-3 mol L-1 with a detection limit of 2.0x10-6 mol L-1 and recovery of hydroquinone ranging from 95.1 to 105% were obtained. The relative standard deviation was < 1.0 % for a solution of 3.0x10-4 mol L-1 hydroquinone and 2.0x10-3 mol L-1 hydrogen peroxide in 0.1 mol L-1 phosphate buffer solution at pH 7.0 (n=8). The lifetime of this biosensor was 6 months (at least 300 determinations).

Determinação turbidimétrica de metilbrometo de homatropina em formulações farmacêuticas empregando um sistema de análise por injeção em fluxo

A flow injection turbidimetric procedure exploiting merging zones is proposed for determining homatropine methylbromide (HMB) in pharmaceutical preparations. The determination is based on the precipitation reaction of homatropine methylbromide with AgNO3 solution to form a precipitate, which was measured at 410 nm. The analytical curve was linear in the HMB concentration range from 8.0x10-4 to 1.7x10-3 mol L-1, with a detection limit of 9.5x10-5 mol L-1. The recoveries ranged from 94.9 to 104 %, the sampling frequency was 75 h-1 and relative standard deviations were smaller than 2.0 % for solutions containing 1.2x10-3 and 1.5x10-3 mol L-1 HMB (n=10). The results obtained for commercial formulations using the FIA procedure were in good agreement with those obtained by using a comparative method (r= 0.9983).

Influência de desproteinizantes ácidos na quantificação da glutationa reduzida eritrocitária por CLAE-UV

Large differences in reduced glutathione (GSH) levels have been found in different investigations, also in healthy people. GSH oxidation in vitro has been associated with sample acidification in the presence of oxihemoglobin. In this work, the influence of different acids on GSH determination utilizing HPLC with UV detection was evaluated. The results showed that metaphosphoric acid and sulfosalicylic acid were inadequate for analysis, because metaphosphoric acid showed to be inefficient for deproteinization and with sulfosalicylic acid loss of GSH was observed. Trichloroacetic acid did not effect GSH quantification, since the deproteinized form was immediately derivatized with 5, 5´-dithio-bis (2-nitrobenzoic) acid. Methods with TCA deproteinization presented linear results from 0.5 to 3.0 mM. The correlation coefficient between aqueous curves and GSH spiked RBC exceeded 0.99. Precision calculations showed CV lower than 10% and bias within ± 10% for concentrations of 0.5; 1.5 and 3.0 mM GSH. The recovery was higher than 94%. Moreover, GSH blood concentrations were independent of hemoglobin concentrations.

Determinação voltamétrica por redissolução anódica de Cu(II) em águas residuárias empregando um eletrodo de pasta de carbono modificado com quitosana

The electrochemical applications of a CPE modified with chitosan for the determination of Cu(II) in wastewater samples using anodic stripping voltammetry are described. The best voltammetric response was observed for a paste containing 25% m/m of chitosan. A 0.10 mol L-1 NaNO3 solution (pH 6.5) as supporting electrolyte, a pre-concentration potential of -0.20 V, pre-concentration time of 270 s and a scan rate of 25 mV s-1 were selected. The calibration graph was linear in the Cu(II) concentration range from 2.0 x 10-7 to 7.4 x 10-6 mol L-1, with a detection limit of 8.3 x 10-8 mol L-1.

Utilização do índice de retenção linear para caracterização de compostos voláteis em café solúvel utilizando GC-MS e coluna HP-Innowax

Gas chromatography coupled with mass spectrometry (GC-MS) is widely used for the characterization of volatile compounds. However, due to the complexity of the soluble coffee matrix, a complete identification of the components should not be based on mass spectra interpretation only. The linear index of retention (LRI) is frequently used to give support to mass spectra. The aim of this work is to investigate the characterization of the volatile compounds in soluble coffee samples by GC-MS using LRI values found with a HP-INNOWAX column. The method used allows a significant increase of the reliability of identifying compounds.

Eficiència energètica aplicada a les instal·lacions de la Universitat de Vic

En termes generals, es pot definir l’Eficiència Energètica com la reducció del consum d’energia mantenint els mateixos serveis energètics, sense disminuir el nostre confort i qualitat de vida, protegint el medi ambient, assegurant el proveïment i fomentant un comportament Sostenible al seu ús. L’objectiu principal d’aquest treball, és reduir el consum d’energia i terme de potència contractat a la Universitat de Vic, aplicant un programa d’estalvi amb mesures correctores en el funcionament de les seves instal·lacions o espais. Per tal de poder arribar a aquest objectiu marcat, prèviament s’ha realitzat un estudi acurat, obtenint tota la informació necessària per poder aplicar les mesures correctores a la bossa més important de consum. Un cop trobada, dur a terme l’estudi de la viabilitat de la inversió de les mesures correctores més eficients, optimitzant els recursos destinats. L’espai on s’ha dut a terme l’estudi, ha estat a l’edifici F del Campus Miramarges, seguint les indicacions d’Arnau Bardolet (Cap de Manteniment de la UVIC). Aquest edifici consta d’un entresol, baixos i quatre plantes. L’equip de mesura que s’ha fet servir per realitzar l’estudi, és de la marca Circutor sèrie AR5-L, aquests equips són programables que mesuren, calculen i emmagatzemen en memòria els principals paràmetres elèctrics en xarxes trifàsiques. Els projectes futurs complementaris que es podrien realitzar a part d’aquest són: instal·lar sensors, instal·lar mòduls convertidors TCP/IP, aprofitar la xarxa intranet i crear un escada amb un sinòptic de control i gestió des d’un punt de treball. Aquest aplicatiu permet visualitzar en una pantalla d’un PC tots els estats dels elements controlats mitjançant un sinòptic (encendre/parar manualment l’enllumenat i endolls de les aules, estat d’enllumenat i endolls de les aules, consums instantanis/acumulats energètics, estat dels passadissos entre altres) i explotar les dades recollides a la base de dades. Cada espai tindria la seva lògica de funcionament automàtic específic. Entre les conclusions més rellevants obtingudes en aquest treball s’observa: · Que és pot reduir la potència contractada a la factura a l’estar per sota de la realment consumida. · Que no hi ha penalitzacions a la factura per consum de reactiva, ja que el compensador funciona correctament. · Que es pot reduir l’horari de l’inici del consum d’energia, ja que no correspon a l’activitat docent. · Els valors de la tensió i freqüència estan dintre de la normalitat. · Els harmònics estan al llindar màxim. Analitzant aquestes conclusions, voldria destacar les mesures correctores més importants que es poden dur a terme: canvi tecnològic a LED, temporitzar automàticament l’encesa i apagada dels fluorescents i equips informàtics de les aules “seguint calendari docent”, instal·lar sensors de moviment amb detecció lumínica als passadissos. Totes les conclusions extretes d’aquest treball, es poden aplicar a tots els edificis de la facultat, prèviament realitzant l’estudi individual de cadascuna, seguint els mateixos criteris per tal d’optimitzar la inversió.

Determinação voltamétrica de ciclamato de sódio em produtos dietéticos empregando um eletrodo de diamante dopado com boro

The use of square-wave voltammetry in conjunction with a cathodically pre-treated diamond electrode for the analytical determination of sodium cyclamate is described. The samples were analyzed as received in a 0.5 mol L-1 H2SO4 solution in the concentration range from 5.0 × 10-5 mol L-1 to 4.1 × 10-4 mol L-1, with a detection limit of 4.8 × 10-6 mol L-1. The RSD was smaller than 1.2 % and the proposed method was applied with success in the determination of sodium cyclamate in several dietary products.

Determinação turbidimétrica do antidepressivo amitriptilina em sistema fia explorando a formação do par iônico com lauril sulfato de sódio

The present work purposes the development of an analytical method for amitriptyline determination in pharmaceutical formulations using FIA system. It was based on interaction of amitriplyline with sodium lauryl sulphate in acid medium (pH 2.5) resulting in the ion-pair formation turbidimetrically detected at 410 nm. The fitting regression equation for range curve from 2.0 x 10-3 up to 3.2 x 10-3 mol L-1 was found to be analytical signal = -2.7417 + 0.1538 [amitriptyline] (r = 0.99991) with a detection limit of 1.8 x 10-3 mol L-1. The precision assessed as relative standard deviation (n = 10) was found to be 2.40 and 1.94%, for the respective concentration of amitriplyline 2.0 x 10-3 and 3.2 x 10-3 mol L-1 and the sample throughout was 60 h-1. The accuracy of method was successfully assessed in pharmaceutical formulation after comparison with a reference analytical method.

Determinação espectrofotométrica em fluxo de cloro em água usando célula de longo caminho óptico e multicomutação

A multicommuted method for determination of chlorine in water samples using a 100-cm cell was developed. In this method, orto-Tolidine reacts with chlorine and the product was monitored at 438 nm. The analytical curve for chlorine was linear in concentration range from 1.34x10-6 to 2.01x10-5 mol L-1 with a detection limit of 9.40x10-8 mol L-1. A sampling rate of 45 h-1and a RSD of 1.0 % (n = 15) were obtained. The method was applied with success for chlorine determination in six water samples.

Cromatografia gasosa bidimensional abrangente (GC × GC)

This paper presents the fundamental principles, instrumentation and selected applications of comprehensive two-dimensional gas chromatography (GC × GC). In this technique, introduced in 1991, two capillary columns are coupled and proper modulating interfaces continuously collect the eluate from the first column, transferring it to the second column. The result is a geometric increment in the chromatographic resolution, ensuring separation of extremely complex mixtures in time periods shorter or comparable to those of analysis using conventional gas chromatography and with better detectabilities and sensitivities.

Optimization of the carrot leaf dehydration aiming at the preservation of omega-3 fatty acids

The carrot leaf dehydration conditions in air circulation oven were optimized through response surface methodology (RSM) for minimizing the degradation of polyunsaturated fatty acids, particularly alpha-linolenic (LNA, 18:3n-3). The optimized leaf drying time and temperature were 43 h and 70 ºC, respectively. The fatty acids (FA) were investigated using gas chromatography equipped with a flame ionization detector and fused silica capillary column; FA were identified with standards and based on equivalent-chain-length. LNA and other FA were quantified against C21:0 internal standard. After dehydration, the amount of LNA, quantified in mg/100 g dry matter of dehydrated carrot leaves, were 984 mg.

Hidrocarbonetos policíclicos aromáticos (HPAS) em cachaça, rum, uísque e álcool combustível

The concentration of 15 polycyclic aromatic hydrocarbons (PAHs) in 57 samples of distillates (cachaça, rum, whiskey, and alcohol fuel) has been determined by HPLC-Fluorescence detection. The quantitative analytical profile of PAHs treated by Partial Least Square - Discriminant Analysis (PLS-DA) provided a good classification of the studied spirits based on their PAHs content. Additionally, the classification of the sugar cane derivatives according to the harvest practice was obtained treating the analytical data by Linear Discriminant Analysis (LDA), using naphthalene, acenaphthene, fluorene, phenanthrene, anthracene, fluoranthene, pyrene, benz[a]anthracene, benz[b]fluoranthene, and benz[g,h,i]perylene, as a chemical descriptors.

Determinação de paracetamol pela inibição da reação quimiluminescente do luminol-hipoclorito de sódio em um sistema de análise em fluxo empregando o conceito de multicomutação

A flow injection chemiluminescence method for the determination of paracetamol in pharmaceutical formulations is described. It is based on the consumption of the sodium hypochlorite by paracetamol and decreases of the analytical signal. The analytical curve was linear in the paracetamol concentration range from 5.0 x 10-6 to 5.0 x 10-5 mol L-1, with a detection limit of 1.8 x 10-6 mol L-1. The RSDs were 2.0 and 1.2% respectively for 2.0 x 10-5 and 4.0 x 10-5 mol L-1 paracetamol solutions (n = 10) and a sampling frequency of 180 h-1 was obtained.

Determinação turbidimétrica em fluxo de cloridrato de fluoxetina em formulações farmacêuticas

A simple, accurate and precise flow-injection turbidimetric procedure for the determination of fluoxetine hydrochloride in pharmaceutical formulations is reported. The procedure is based on the precipitation of chloride of fluoxetine hydrochloride with silver nitrate solution and the yielded insoluble AgCl(s) was monitored at 420 nm. The analytical curve was linear in the fluoxetine hydrochloride concentration range 3.0 x 10-5 - 5.0 x 10-4 mol L-1 with a detection limit of 10 µmol L-1 and, a sample throughout of 60 h-1.