Determination of the HMX and RDX content in synthesized energetic material by HPLC, FT-MIR, and FT-NIR spectroscopies

A new method has been developed for determining the content of mixtures of octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX) and hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX), the HMX/RDX ratio, in explosive compositions by Fourier transform infrared spectroscopy (FT-IR), in the regions MIR (mid infrared) and NIR (near infrared) with reference values obtained by chromatographic analysis (HPLC). Plots of relative MIR (A917 / A783) or NIR absorbance values (A4412 / A4317) versus HMX/RDX ratio determined by HPLC analysis revealed good linear relationships.

Validation and statistical analysis of two high performance liquid chromatography methods for the determination of indinavir sulfate raw material and capsules

Two high performance liquid chromatography (HPLC) methods for the quantitative determination of indinavir sulfate were tested, validated and statistically compared. Assays were carried out using as mobile phases mixtures of dibutylammonium phosphate buffer pH 6.5 and acetonitrile (55:45) at 1 mL/min or citrate buffer pH 5 and acetonitrile (60:40) at 1 mL/min, an octylsilane column (RP-8) and a UV spectrophotometric detector at 260 nm. Both methods showed good sensitivity, linearity, precision and accuracy. The statistical analysis using the t-student test for the determination of indinavir sulfate raw material and capsules indicated no statistically significant difference between the two methods.

Estudo de homogeneidade de lote de material silício metálico candidato a material de referência

From the perspective of the uncertainties in chemical measurements all uncertainty sources should be part of the uncertainty of the reference material. When the primary methods are not available, interlaboratorial comparisons are used as a means of certification. The material to be distributed to the laboratories should have its homogeneity confirmed. The uncertainty due to this factor will be added to the characterization uncertainty. This work presents a homogeneity study of a lot of silicon metal of chemical degree where the uncertainty due to inhomogeneity is obtained using analysis of variance.

Influência do material e volume do porta-amostra na determinação termogravimétrica do teor de cinzas em mel

The results suggest that the two variables studied are significant and that they may be independently optimized. The material of the sample holder interferes with the incineration process only due to the amount of heat transfered. The sample holder volume aids diffusion of the atmosphere to the honey sample, minimizing the foaming effect. According to the results, for the thermogravimetric analysis of ash content in honey, sample holders of platinum or alumina of 150 µL are indicated.

Análise de fármacos em material biológico: acoplamento microextração em fase sólida "no tubo" e cromatografia líquida de alta eficiência

A new solid phase microextraction (SPME) system, known as in-tube SPME, was recently developed using an open tubular fused-silica capilary column, instead of an SPME fiber, as the SPME device. On-line in-tube SPME is usually used in combination with high performance liquid chromatography. Drugs in biological samples are directly extracted and concentrated in the stationary phase of capillary columns by repeated draw/eject cycles of sample solution, and then directly transferred to the liquid chromatographic column. In-tube SPME is suitable for automation. Automated sample handling procedures not only shorten the total analysis time, but also usually provide better accuracy and precision relative to manual techniques. In-tube SPME has been demonstrated to be a very effective and highly sensitive technique to determine drugs in biological samples for various purposes such as therapeutic drug monitoring, clinical toxicology, bioavailability and pharmacokinetics.

A espectrometria atômica e a determinação de elementos metálicos em material polimérico

Polymeric materials are widely used in the chemical industry and are part of our daily lives. Inorganic species may be added to them as additives, anti-oxidizing agents, stabilizers, plasticizers, colorants and catalysts and may be present in a wide range of concentrations. Their determination demands the development of analytical methods considering different kinds of polymeric materials, their composition and the final use of the material. Although many different analytical techniques may be used, this review emphasizes those based on atomic absorption and emission spectrometry. Solid sampling techniques and digestion methods are described and discussed and compared considering published results.

Propriedades redox da matéria orgânica isolada de material ultrafiltrado das águas do rio Paraíba do Sul

Previous studies indicated that free radicals control organic matter redox activities. In the present study, organic matter of an ultra-filtrated material collected from seven samples taken seasonally from the Paraiba do Sul River for two years were titrated with an oxidizer (I2) in an inert atmosphere. Standard formal potential values for the electrode MO Ox, MO Red ranged from 0.754 to 0.786 V at a 25 ºC temperature. Organic matter oxidation capacity (COx) per carbon mass varied according to pH values, and changes in COx were related to rainfall and river flow intensities.

Hidrólise parcial da superfície do polyethylene terephthalate (PET): transformando um rejeito em um material de troca catiônica para aplicação ambiental

In this work it is proposed a simple and versatile undergraduate chemical experiment in polymer and environmental technology based on the process of polyethylene terephthalate (PET) hydrolysis. Polyethylene terephthalate from post-consume bottles is submitted to a controlled partial hydrolysis which allows the students to follow the reaction by a simple procedure. The students can explore the reaction kinetics, the effect of catalysts and the exposed polyethylene terephthalate surface area on the hydrolysis reaction. The second and innovative part of this experiment is the technological and environmental application of the hydrolyzed polyethylene terephthalate as a material with cation exchange properties. The surface hydrolyzed polyethylene terephthalate can be used as adsorbent for cationic contaminants.

Caracterização e propriedades do material coloidal nanoestruturado β-FeOOH/bentonita

A new mixed material was obtained through the combination of the suspensions of iron oxy-hydroxide and bentonite clay, denoted BFe. Analysis of its structure (XRD, Mossbauer and TGA) and composition (AAS) suggests the maintenance of the layer structure of the clay and an increase in the thermal stability of the BFe. Electrochemical studies performed in different electrolytes show that only in an alkaline medium it is possible to observe the redox peaks relative to the processes involving Fe+2/Fe+3 pair. Tests that evaluated the potential use of the photo-Fenton process showed an efficient degradation process of the dyes in significantly reduced reaction times.

Determinação seletiva de tributilestanho na presença de Sn(IV) em amostras ambientais usando HG-ICP OES e Saccharomyces cerevisiae como material sorvente

A method for selective determination of tributyltin in the presence of Sn(IV) by combining hydride generation inductively coupled plasma optical emission spectrometry (HG-ICP OES) and solid phase extraction (SPE) using baker's yeast is proposed. The procedure is based on selective retention of TBT by the yeast at pH = 6. Detection limit of 1.9 µg L-1 and quantification limit of 6.3 µg L-1 were obtained. TBT and San(IV) were determined in the range of 0-25 µg L-1 and the proposed approach was applied to analyze river water, sea water and biological extracts, with recoveries of 114, 101 and 86%, respectively.

Desidratação de etanol sobre material nanoestruturado do tipo LaSBA-15

La-incorporated SBA-15 mesopourous molecular sieves (LaSBA-15) were directly synthesized with aim to convert ethanol to ethylene. The samples were characterized by XRD, XRF, nitrogen sorption and acidity, by thermodesorption of n-buthylamine. The results have indicated that all the samples have showed high ordered mesostructure with a large average pore size, and that the lanthanum incorporation has caused an increase in the acidity of the SBA-15. The LaSBA-15 samples have improved, with low deactivation rate, the conversion of the ethanol to water, ether, acetaldehyde and ethylene. In addition, they have increased the ethylene selectivity.

Eletrodos positivos tubulares para baterias chumbo ácidas produzidas com material ativo nanométrico

Conventional stationary lead acid batteries positive tubular plates have a specific capacity of about 120 Ah/kg. This value represents an active material utilization coefficient of 50%. The production of these plates includes some initial processes to generate the active PbO2 from a precursor material. In the present work it will be presented a proper and novel methodology to assemble tubular plates directely with nanometric powder of PbO2 particles. The utilization coefficient of these plates was about 80%, and they were able to endure more than 130 severe duty cycles. This high utilization coefficient is a higly desirable feature for electric vehicles batteries.

Remoção dos hormônios 17β-estradiol e 17α-etinilestradiol de soluções aquosas empregando turfa decomposta como material adsorvente

This paper describes the adsorption of 17β-estradiol (E2) and 17α-ethinylestradiol (EE2) from aqueous solution by decomposed peat. The peat presented a good adsorption process, close to 76.2% for E2 removal and approximately 55.0% for EE2. Moreover, the results indicated a probable multi-layered process. Adsorption isotherms were well fitted by Freundlich model. The data were evaluated considering the pseudo-first-order and pseudo-second-order approaches, being the second more significant mechanism in the rate-controlling step. Thermodynamic data revealed that hormones adsorption onto peat is spontaneous under the employed experimental conditions. The results confirmed the potential of this adsorbent to be employed for effluents treatment.

A quantitative validated method using liquid chromatography and chemometric analysis for evaluation of raw material oF Maytenus ilicifolia (Schrad.) Planch., Celastraceae

The hydroalcoholic extracts prepared from standard leaves of Maytenus ilicifolia and commercial samples of espinheira-santa were evaluated qualitatively (fingerprinting) and quantitatively. In this paper, fingerprinting chromatogram coupled with Principal Component Analysis (PCA) is described for the metabolomic analysis of standard and commercial espinheira-santa samples. The epicatechin standard was used as an external standard for the development and validation of a quantitative method for the analysis in herbal medicines using a photo diode array detector. This method has been applied for quantification of epicatechin in commercialized herbal medicines sold as espinheira-santa in Brazil and in the standard sample of M. ilicifolia.

A retórica da linguagem científica: das bases teóricas à elaboração de material didático para o ensino superior de Química

This work is part of a study that focused on analyzing the contributions of didactic activities related to scientific language rhetoric characteristics aimed at developing students' abilities to identify such characteristics in chemistry scientific texts and critical reading of those texts. In this study, we present the theoretical basis adopted to determine the scientific discourse characteristics and for the production of the didactic material used in those activities. Latour, Coracini and Campanario studies on persuasive rhetorical strategies present in scientific articles aided the production of such material.