1-Nitropyrene (1NPy) is the most abundant nitropolycyclic aromatic contaminant encountered in diesel exhausts. Understanding its photochemistry important because of carcinogenic and mutagenic properties, potential phototransformations into biologically active products. We have studied photophysics 1NPy solvents that could mimic microenvironments which it can be found atmospheric aerosol, using nanosecond laser flash photolysis, conventional absorption fluorescence techniques. Significant...

Stoichiometric network analysis (SNA) is used to study spontaneous mirror symmetry breaking in chemical reaction schemes.

The removal of Cr(VI) from aqueous solutions was studied using a compost generated carnation flowers waste. highest percentage achieved (ca. 99 %) obtained at pH 2.0, 10 mg L-1 solution, dose g compost, and with an equilibrium time 3 hours. Under these conditions, the kinetics adsorption isotherm were examined varying initial concentration 15 to 200 L-1. maximum sorption capacity (Qm), Langmuir model, found be 6.25 g-1. evaluation 2.0 showed second order that process mechanism can modeled by...

The kinetics of the Dushman reaction, 5I- + IO3- 6H+ → 3I2 3H2O, is considerably more complex in aqueous, acidic media than behavior analogous reaction Br- with BrO3-. latter first order both [Br-] and [BrO3-] believed to proceed via a series simple oxygen-atom transfers, there being no evidence for intermediacy polybromine species such as H2Br2O3. In contrast, [I-] reported variously be one or two, depending upon experimental conditions, especially [IO3-]0/[I-]0, this generally very H2I2O3...

In this paper we present the dependence of induction time Belousov-Zhabotinsky reaction (BZ) on initial concentrations malonic acid, bromate and cerium. The experimental results show that gets larger with increasing behaviour does not agree mechanistic explanations based models proposed for BZ reaction. We propose a kinetic competition between bromination acid oxidation bromomalonic acids is way to understand behaviour. Model calculations using GTF MBM support explanation.

A reação de Belousov-Jabotinsky clássica foi modificada pela adição fenol como um segundo substrato orgânico que compete cineticamente com o ácido malônico na redução Ce 4+ para 3+ e remoção bromo molecular da reação.A oscilante dois substratos exibiu oscilações abruptas período oscilatório longa duração.A análise dados experimentais mostra aumento do fenômeno abrupto,

Abstract Titrations are a group of techniques that have contributed considerably to developing the chemical industry and chemistry itself. Currently, Consultative Committee for Amount Substance has recognized titration as one primary methods determining amount substance. In this context, an accurate gravimetric complexometric method was implemented determine purity ethylenediaminetetraacetic acid (EDTA) disodium salt dihydrate using lead nitrate-certified reference material (CRM). The...

This work presents the optimization process of mercury determination by Anodic Stripping Voltammetry (ASV), using a glassy carbon modified with gold film as working electrode, in samples extracted aqua regia.The may contain Cu, Fe or Pb high concentrations.In these conditions usual Hg ASV is almost impossible.The effects supporting electrolyte on sensitivity method and chloride nitrate ions concentration were studied.Supporting was selected between: HCl, HNO 3 , HClO 4 CH COOH.Our results...

The kinetics of the reaction HBrO(2) + --> HOBr BrO(3)(-) H(+) is investigated in aqueous HClO(4) (0.04-0.9 M) and H(2)SO(4) (0.3-0.9 media at temperatures range 15-38 degrees C. found to be cleanly second order [HBrO(2)], with experimental rate constant having form k(exp) = k k'[H(+)]. half-life on a few tenths 0.01 M < [HBrO(2)](0) 0.02 M. detailed mechanism this discussed. activation parameters for kare E(double dagger) 19.0 +/- 0.9 kJ/mol DeltaS(double -132 3 J/(K mol) HClO(4), 23.0 0.5...

A kinetic study of the uncatalyzed bromate oscillator (UBO) using phenol was carried out by chemometric analysis UV/Vis data. The reaction studied with different starting concentrations reagents (sulfuric acid and potassium bromate) changing for 2-bromophenol 4-bromophenol. number chemical absorbing species involved in data established singular value decomposition residual fit parameter. Multivariate curve resolution alternating least squares generated valuable information about along...

Contrary to what has been thought, systems classified as bromine-hydrolysis-controlled (BHC) show an induction period. In studies on the effect of a family ketones upon this type oscillators, it was found that period appears in interval concentrations ketone, or value enolization constant. Simulations processes involved and corresponding explanation are shown paper.

When a methyl ketone is added to the Belousov−Zhabotinskii (BZ) reaction, an increase of induction period and in number oscillations observed. This behavior can be explained by competition malonic acid for molecular bromine. We studied effect four ketones BZ reaction found direct relationship between period, concentration, enolization constant ketone. A discussion results with regard crucial concentration bromomalonic given. The experimental are supported simulations based upon GTF mechanism...

Current research has highlighted the need to understand factors influencing cadmium (Cd) availability in cacao-growing soils elucidate its presence cacao beans (the raw material for chocolate). Although literature about this topic is increasing, few report importance of rhizosphere on Cd dynamics. This study aimed changes available and association with soil properties (pH, pseudo-total Cd, (Cd-DTPA), Ca, Mg, K, Na, organic carbon, P, Zn, urease activity, exchangeable acidity, cation exchange...

The goal of our research is the development algorithmic tools for analysis chemical reaction networks proposed as models biological homochirality. We focus on two problems: detecting whether or not a mechanism admits mirror symmetry-breaking; and, given one those input, sampling set racemic steady states that can produce symmetry-breaking. Algorithmic solutions to problems will allow us compute parameter values emergence found mathematical criterion occurrence This allows semialgebraic...

A method for quantification of arsenic, cadmium, mercury, and lead in pineapple using inductively coupled plasma-mass spectrometry (ICP-MS) was developed, validated, used to test the homogeneity stability in-house reference materials.The tested at regulation levels given by Food Agriculture Organization United Nations (FAO, 100 µg kg -1 ).The mineralization conditions samples, a microwave oven, were improved throughout study HNO 3 H 2 O concentrations, sample weight, time, temperatures.The...

Coulometry is a well-established technique for certified reference materials (CRM). However, commercial coulometers are currently expensive and utilize outdated software. The National Metrology Institute of Colombia (INMC) has developed cheaper modular coulometer with powerful software capable controlling the instrument, acquiring pH, potential difference between generator electrodes, electrical current at any stage coulometric titration. results obtained from this new align well novel...

The generation of amino acid homochirality under prebiotic atmosphere conditions is a relevant issue in the study origin life. This research based on production acids via Strecker synthesis and how it adjusted to Kondepudi-Nelson autocatalytic model. spontaneous mirror symmetry breaking (SMSB) new Kondepudi-Nelson-Strecker model, subject two modifications (with Limited Enantioselective Cross Inhibition), also their combination were studied using stoichiometric network analysis (SNA). In...

In metrology, the certification of potassium hydrogen phthalate (KHP) as a reference material is made using potential primary method coulometric titration. Usually, this titration performed in three steps at constant current, where two endpoint (EP) times are determined from nonlinear regression that fits empirical W-function (eWf) to experimental data. As an alternative, we propose implementation theoretical curve (TC). The TC allowed us compute KHP amount substance, influence CO2 system,...

CHEMical KINetics SimuLATOR is a Graphical User Interface for the simulation of reaction mechanisms. The interface allows user to see and change parameters network within single window. Chemkinlator comes with built-in support three types kinetic simulations: Time Series, which computes concentration all species in an interval time defined model; Bifurcation diagrams, are result running several Series simulations over gradually different rate constants; Flow/Temperature series, takes into...

En este trabajo se presenta un estudio para determinar el mecanismo del proceso de remoción Cr(VI) disoluciones acuosas, usando como adsorbente compost obtenido residuos cultivo clavel. primer lugar, determinó si la microbiota presente en material afecta Cr(VI). Para esto realizaron medidas respirométricas y evaluó capacidad esterilizado sin esterilizar. Adicionalmente, analizó antes después llevar a cabo deCr(VI),mediante cuantificación grupos funcionales ácidos seguimiento cinético pH,...

Biological homochirality is modelled using chemical reaction mechanisms that include autocatalytic and inhibition reactions as well input output flows. From the mathematical point of view, differential equations associated with those have to exhibit bistability. The search for bifurcations can be carried out stoichiometric network analysis. This algorithm simplifies analysis implemented in a computer programme, which help us analyse networks. However, regardless reduction linear polynomials,...

Colombian emeralds, 26 from Palo Arañado (eastern emerald zone, Chivor district, Boyacá, Colombia), and 28 Santo Domingo - La Pava mine (western Muzo together with 30 Kafubu Zambia, were studied by reflectance Fourier transform infrared spectroscopy, principal component analysis, clustering, partial least squares – discriminant in order to differentiate them geographical origin. The spectra smoothed a baseline correction was made. analysis showed that the wavenumbers 2,474; 2,640; 2,686;...