Cromatografia gasosa-espectrometria de massas e derivatização assistida por micro-ondas na identificação de isômeros de glicose: uma prática para o ensino avançado em análise e caracterização de compostos orgânicos

This work reports a practical case based on the use of microwave-assisted derivatization and GC-MS for the analysis of glucose. Using two different methods for derivatization, one reference compound and the calculated dipole moment, all the isomers of glucose were identified. Identification was corroborated for the assignment of structures using the mass spectra. With this work, students are expected to associate different types of information to solve the complex problem of the analysis of glucose.

Ligandless cloud point extraction of trace amounts of palladium and rhodium in road dust samples using Span 80 prior to their determination by flame atomic absorption spectrometry

In this study, a procedure is developed for cloud point extraction of Pd(II) and Rh(III) ions in aqueous solution using Span 80 (non-ionic surfactant) prior to their determination by flame atomic absorption spectroscopy. This method is based on the extraction of Pd(II) and Rh(III) ions at a pH of 10 using Span 80 with no chelating agent. We investigated the effect of various parameters on the recovery of the analyte ions, including pH, equilibration temperature and time, concentration of Span 80, and ionic strength. Under the best experimental conditions, the limits of detection based on 3Sb for Pd(II) and Rh(III) ions were 1.3 and 1.2 ng mL-1, respectively. Seven replicate determinations of a mixture of 0.5 µg mL-1 palladium and rhodium ions gave a mean absorbance of 0.058 and 0.053 with relative standard deviations of 1.8 and 1.6%, respectively. The developed method was successfully applied to the extraction and determination of the palladium and rhodium ions in road dust and standard samples and satisfactory results were obtained.

Coprecipitation of trace amounts of silicon with aluminum hydroxide and the determination by flame atomic absorption spectrometry

A simple preconcentration method of silicon based on coprecipitation with aluminum hydroxide prior to its flame atomic absorption (FAAS) determination was established. The recovery values of analyte ion was higher than 95%. The parameters including types of hydroxide ion source for precipitation, acid type for dissolution step, amount of aluminum ion as collector, pH, temperature, standing and centrifuge time, and sample volume were optimized for the quantitative recovery of the analyte. The influences of matrix ions were also examined. The relative standard deviation was found to be 3.2%. The limit of detection was calculated as (0.1 mg L-1). The preconcentration factor is 100 for (200 mL) solution. The proposed method was successfully applied for the determination of silicon in some water and alloy samples.

RAPID AND SENSITIVE DETERMINATION OF PALLADIUM USING HOMOGENEOUS LIQUID-LIQUID MICROEXTRACTION VIA FLOTATION ASSISTANCE FOLLOWED BY GRAPHITE FURNACE ATOMIC ABSORPTION SPECTROMETRY

A method for the determination of trace amounts of palladium was developed using homogeneous liquid-liquid microextraction via flotation assistance (HLLME-FA) followed by graphite furnace atomic absorption spectrometry (GFAAS). Ammonium pyrrolidine dithiocarbamate (APDC) was used as a complexing agent. This was applied to determine palladium in three types of water samples. In this study, a special extraction cell was designed to facilitate collection of the low-density solvent extraction. No centrifugation was required in this procedure. The water sample solution was added to the extraction cell which contained an appropriate mixture of extraction and homogeneous solvents. By using air flotation, the organic solvent was collected at the conical part of the designed cell. Parameters affecting extraction efficiency were investigated and optimized. Under the optimum conditions, the calibration graph was linear in the range of 1.0-200 µg L-1 with a limit of detection of 0.3 µg L-1. The performance of the method was evaluated for the extraction and determination of palladium in water samples and satisfactory results were obtained. In order to verify the accuracy of the approach, the standard addition method was applied for the determination of palladium in spiked synthetic samples and satisfactory results were obtained.

Resistance spectra of wheat cultivars and virulence diversity of Magnaporthe grisea isolates in Brazil

Seventy-two monoconidial isolates of Magnaporthe grisea were obtained from the States of Mato Grosso do Sul and Paraná. The isolates were inoculated on seedlings of 20 wheat (Triticum aestivum) cultivars under greenhouse conditions. The virulence diversity of M. grisea was assessed based on compatible and incompatible reactions of leaf blast on wheat cultivars. Fifty-four distinct virulence patterns were identified on test cultivars among the isolates collected from the two wheat growing States. Sixteen of these isolates corresponding to 22.2% showed similar virulence pattern. None of the wheat cultivars was resistant to all isolates of M. grisea, but the cultivars differed in degree of resistance as measured by the relative spectrum of resistance (RSR) and disease index (DI). Among the cultivars the RSR ranged from 0 to 53.3% and DI from 0.4662 to 0.9662 (0 to 1 scale). The wheat cultivar BR18 exhibited a broad resistance spectrum in relation to the rest of the tested cultivars to the isolates of M. grisea, and can be used in wheat resistance breeding.

Experimental and theoretical investigation of the IR spectra and thermochemistry of four isomers of 2-N,N-dimethylaminecyclohexyl 1-N',N'-dimethylcarbamate

A combined experimental and Density functional theory (DFT) B3LYP/6-311+G* study on the IR spectra of four stable isomers of 2-N,N-dimethylaminecyclohexyl 1-N',N'-dimethylcarbamate was performed. Our theoretical calculations reveal that two new isomers of this compound exist and may be more stable than the known isomers. In addition the entropy, heat capacity, and the enthalpy content of the stable isomers are computed by fitting the calculated data to a standard Shomate equation and IR spectra for the two new isomers are presented.

Analysis of the structure and vibrational spectra of glucose and fructose

Molecular modelling using semiempirical methods AM1, PM3, PM5 and, MINDO as well as the Density Functional Theory method BLYP/DZVP respectively were used to calculate the structure and vibrational spectra of d-glucose and d-fructose in their open chain, alpha-anomer and beta-anomer monohydrate forms. The calculated data show that both molecules are not linear; ground state and the number for the point-group C is equal to 1. Generally, the results indicate that there are similarities in bond lengths and vibrational modes of both molecules. It is concluded that DFT could be used to study both the structural and vibrational spectra of glucose and fructose.

Direct determination of calcium in milk by atomic absorption spectrometry using flow-injection analysis

A flow-injection system with sample and reagent addition by the synchronous merging zones approach for calcium determination in milk by flame AAS is proposed. Main parameters were optimized using a factorial design with central point. The optimum conditions were 2.5% (m/v) for La concentration, 8 mL min-1 for the carrier flow-rate, 20 cm for coiled reactor and 250 ìL for sample volume. Different sample preparation procedures were evaluated such as dilution in water or acid and microwave-assisted decomposition using concentrated or diluted acids. The optimized flow system was applied to determine Ca in eleven commercial milk samples and two standard reference materials diluted in water. Similar calcium levels were encountered comparing the results obtained by the proposed method (dilution in water) with those obtained using microwave-oven digestion. Results obtained in two standard reference materials were in agreement at 95% confidence level with those certified. Recoveries of spiked samples were in the 93% - 116% range. Relative standard deviation (n = 12) was < 5.4% and the sample throughput was 150 measurements per hour, corresponding to a consumption of 250 µL of sample and 6.25 mg La per determination.

Solid phase extraction of zinc with octadecyl silica membrane disks modified by N,N'-disalicylidene-1,2-phenylendiamine and determination by flame atomic absorption spectrometry

A procedure for separation and preconcentration of trace amounts of Zn(II) from aqueous media is proposed. The procedure is based on the adsorption of Zn2+ on octadecyl bonded silica membrane disk modified with N,N'-disalicylidene-1,2-phenylendiamine at pH 7. The retained zinc ions were then stripped from the disk with a minimal amount of 1.5 mol L-1 hydrochloric acid solution as eluent, and determined by flame atomic absorption spectrometry. Maximum capacity of the membrane disk modified with 5 mg of the ligand was found to be 226 µg Zn2+. The relative standard deviation of zinc for ten replicate extraction of 10 µg zinc from 1000 mL samples was 1.2%. The limit of detection of the proposed method was 14 ng of Zn2+ per 1000 mL. The method was successfully applied to the determination of zinc in natural water samples and accuracy was examined by recovery experiments and independent analysis by graphite furnace atomic absorption spectrometry (GFAAS).

Evaluation of group electronegativities and hardness (softness) of group 14 elements and containing functional groups through density functional theory and correlation with NMR spectra data

Quantum Chemical calculations for group 14 elements of Periodic Table (C, Si, Ge, Sn, Pb) and their functional groups have been carried out using Density Functional Theory (DFT) based reactivity descriptors such as group electronegativities, hardness and softness. DFT calculations were performed for a large series of tetracoordinated Sn compounds of the CH3SnRR'X type, where X is a halogen and R and R' are alkyl, halogenated alkyl, alkoxy, or alkyl thio groups. The results were interpreted in terms of calculated electronegativity and hardness of the SnRR'X groups, applying a methodology previously developed by Geerlings and coworkers (J. Phys. Chem. 1993, 97, 1826). These calculations allowed to see the regularities concerning the influence of the nature of organic groups RR' and inorganic group X on electronegativities and hardness of the SnRR'X groups; in this case, it was found a very good correlation between the electronegativity of the fragment and experimental 119Sn chemical shifts, a property that sensitively reflects the change in the valence electronic structure of molecules. This work was complemented with the study of some compounds of the EX and ER types, where E= C, Si, Ge, Sn and R= CH3, H, which was performed to study the influence that the central atom has on the electronegativity and hardness of molecules, or whether these properties are mainly affected for the type of ligand bound to the central atom. All these calculations were performed using the B3PW91 functional together with the 6-311++G** basis set level for H, C, Si, Ge, F, Cl and Br atoms and the 3-21G for Sn and I atoms.

Mathematical equation correction to spectral and transport interferences in high-resolution continuum source flame atomic absorption spectrometry: determination of lead in phosphoric acid

In this work, a new mathematical equation correction approach for overcoming spectral and transport interferences was proposed. The proposal was applied to eliminate spectral interference caused by PO molecules at the 217.0005 nm Pb line, and the transport interference caused by variations in phosphoric acid concentrations. Correction may be necessary at 217.0005 nm to account for the contribution of PO, since Atotal217.0005 nm = A Pb217.0005 nm + A PO217.0005 nm. This may be easily done by measuring other PO wavelengths (e.g. 217.0458 nm) and calculating the relative contribution of PO absorbance (A PO) to the total absorbance (Atotal) at 217.0005 nm: A Pb217.0005 nm = Atotal217.0005 nm - A PO217.0005 nm = Atotal217.0005 nm - k (A PO217.0458 nm). The correction factor k is calculated from slopes of calibration curves built up for phosphorous (P) standard solutions measured at 217.0005 and 217.0458 nm, i.e. k = (slope217.0005 nm/slope217.0458 nm). For wavelength integrated absorbance of 3 pixels, sample aspiration rate of 5.0 ml min-1, analytical curves in the 0.1 - 1.0 mg L-1 Pb range with linearity better than 0.9990 were consistently obtained. Calibration curves for P at 217.0005 and 217.0458 nm with linearity better than 0.998 were obtained. Relative standard deviations (RSD) of measurements (n = 12) in the range of 1.4 - 4.3% and 2.0 - 6.0% without and with mathematical equation correction approach were obtained respectively. The limit of detection calculated to analytical line at 217.0005 nm was 10 µg L-1 Pb. Recoveries for Pb spikes were in the 97.5 - 100% and 105 - 230% intervals with and without mathematical equation correction approach, respectively.

Determination of sulfur in diesel using ATR/FTIR and multivariate calibration

The aim of this present work was to provide a more fast, simple and less expensive to analyze sulfur content in diesel samples than by the standard methods currently used. Thus, samples of diesel fuel with sulfur concentrations varying from 400 and 2500 mgkg-1 were analyzed by two methodologies: X-ray fluorescence, according to ASTM D4294 and by Fourier transform infrared spectrometry (FTIR). The spectral data obtained from FTIR were used to build multivariate calibration models by partial least squares (PLS). Four models were built in three different ways: 1) a model using the full spectra (665 to 4000 cm-1), 2) two models using some specific spectrum regions and 3) a model with variable selected by classic method of variable selection stepwise. The model obtained by variable selection stepwise and the model built with region spectra between 665 and 856 cm-1 and 1145 and 2717 cm-1 showed better results in the determination of sulfur content.

Determination of copper at wide range concentrations using instrumental features of high-resolution continuum source flame atomic absorption spectrometry

This work describes a method to determine Cu at wide range concentrations in a single run without need of further dilutions employing high-resolution continuum source flame atomic absorption spectrometry. Different atomic lines for Cu at 324.754 nm, 327.396 nm, 222.570 nm, 249.215 nm and 224.426 nm were evaluated and main figures of merit established. Absorbance measurements at 324.754 nm, 249.215 nm and 224.426 nm allows the determination of Cu in the 0.07 - 5.0 mg L-1, 5.0 - 100 mg L-1 and 100 - 800 mg L-1 concentration intervals respectively with linear correlation coefficients better than 0.998. Limits of detection were 21 µg L-1, 310 µg L-1 and 1400 µg L-1 for 324.754 nm, 249.215 nm and 224.426 nm, respectively and relative standard deviations (n = 12) were £ 2.7%. The proposed method was applied to water samples spiked with Cu and the results were in agreement at a 95% of confidence level (paired t-test) with those obtained by line-source flame atomic absorption spectrometry.

Cultural and textual properties in the translation and interpretation of allusions. An analysis of allusions in Dorothy L. Sayers’ detective novels translated into Finnish in the 1940s and the 1980s

Kulttuuriset ja tekstuaaliset tekijät alluusioiden kääntämisessä ja tulkinnassa. Alluusiot Dorothy L. Sayersin 1940- ja 1980-luvuilla suomennetuissa salapoliisiromaaneissa Väitöskirja käsittelee alluusioiden kääntämistä ja tulkintaa. Alluusio on intertekstuaalinen viittaus, jonka tulkitsemiseen tarvitaan implisiittistä tietoa tutuksi oletetusta viittauskohteesta. Käännösongelma alluusiosta tulee, mikäli kohdekulttuurin lukijat eivät tunne viittauskohdetta eivätkä voi päätellä alluusion merkitystä. Tutkimus pyrkii kuitenkin uuden analyysimenetelmän avulla osoittamaan, että vieraat alluusiot eivät välttämättä johda tulkintaongelmiin. Väitöskirja jakautuu kahteen osaan: analyysimenetelmän kehittämiseen (luvut 1-5) sekä tapaustutkimukseen (luvut 6-7). Kehitetyn menetelmän avulla pystytään analysoimaan aikaisempaa tarkemmin, millaisia tulkintamahdollisuuksia alluusiot tarjoavat eri lukijakunnille ja miten lähdetekstin alluusioiden kulttuuriset ja tekstuaaliset piirteet korreloivat käännösstrategioiden kanssa. Tapaustutkimus selvittää, millaisia tulkintamahdollisuuksia Dorothy L. Sayersin 1940- ja 1980-luvuilla suomennettujen salapoliisiromaanien alluusiot tarjosivat aikansa suomalaisille lukijoille. Tavoitteena on myös hahmottaa, miten suomentajien käännösratkaisut ja alluusioiden tulkintamahdollisuudet liittyvät toisaalta lähdetekstin alluusioiden piirteisiin ja toisaalta kohdekulttuurin kontekstiin. Tapaustutkimus tarjoaa näin uutta tietoa suomennoskirjallisuuden ja salapoliisiromaanien historiasta. Analyysimenetelmä määrittelee aikaisempaa alluusioita ja intertekstuaalisuutta käsitelleen tutkimuksen pohjalta ne kulttuuriset ja tekstuaaliset piirteet, jotka vaikuttavat alluusioiden kääntämiseen ja tulkintaan. Kulttuurisessa mielessä alluusio voi olla tietylle lukijakunnalle tuttu tai tuntematon. Tekstuaalisia tekijöitä ovat alluusion muodon ja tyylin tunnusmerkillisyys sekä alluusion pintamerkityksen koherenttius uudessa tekstikontekstissa, ilman tietoa viittauskohteesta. Alluusioiden tulkinnassa on perinteisesti erotettu toisaalta allusiivinen tulkintamahdollisuus, jossa alluusio on lukijoille tuttu ja yhdistettävissä viittauskohteeseensa, toisaalta kulttuuritöyssy, jonka muodostaa lukijoille tuntematon ja pintamerkitykseltään inkoherentti alluusio. Tutkimuksessa määritellään kulttuuristen ja tekstuaalisten tekijöiden perusteella lisäksi kaksi muuta mahdollisuutta. Pseudo-allusiivisessa tulkinnassa tuntematon alluusio erottuu ympäröivästä tekstikontekstista tyyliltään ja on koherentti ainakin kuvaannollisessa mielessä ilman viittauskohdettaan. Ei-allusiivisessa tulkinnassa taas vieras alluusio sulautuu kontekstiin sekä muodoltaan että merkitykseltään niin, ettei lukija edes huomaa mahdollista alluusiota. Tulkintamahdollisuuksien jakauma antaa yleiskuvan siitä, miten tietty lukijakunta pystyi tulkitsemaan tekstin alluusioita. Lisäksi analyysi tarkastelee lähdetekstin ja käännöksen välillä tulkintamahdollisuuksissa tapahtuneita muutoksia sekä niiden vaikutusta tulkinnan vaatimaan vaivannäköön (effort) ja alluusion funktioihin. Tapaustutkimus perehtyy Sayers-suomennosten kulttuurikonteksteihin tarkastelemalla salapoliisiromaanien asemaa suomalaisessa kirjallisuusjärjestelmässä, suomennoksilta odotettuja piirteitä sekä suomentajien ammattikuvaa, taustoja ja työoloja. Tulosten perusteella alluusioiden kääntäminen oli vaativa tehtävä sekä 1940- että 1980-luvun suomentajille. Lähdetekstien alluusioista 60–70 prosenttia oli todennäköisesti kohdelukijoille vieraita. Molempina aikakausina suomennoksilta odotettiin silti sekä kielellistä sujuvuutta että lähdetekstin merkitysten välittämistä. 1940-luvun suomentajien tehtävää vaikeutti lisäksi mm. se, että suomentaminen oli enimmäkseen sivutoimista ja englanti oli harvoin parhaiten hallittu vieras kieli. Nämä olosuhteet lienevät vaikuttaneet etenkin vähäarvoisena pidetyn salapoliisikirjallisuuden suomennoksiin. 1980-luvulla suomentajien aikataulut olivat realistisempia, englannin taidot parempia ja päätoiminen suomentaminen mahdollista. Myös salapoliisiromaanien arvostus oli lisääntynyt. Sekä 1940- että 1980-luvun suomennoksissa kohdelukijoille vieraitakin alluusioita oli usein säilytetty, mikäli ne olivat koherentteja ilman viittauskohdettaan. Sen sijaan vieraita ja pintamerkitykseltään epäselviä alluusioita oli muokattu tai poistettu. Kuitenkin 1980-luvun suomentajat säilyttivät lähdetekstin alluusioita useammin ja tarkemmin kuin 1940-luvun suomentajat. Varsinkin poisjättämistä esiintyi 1940-luvun suomennoksissa enemmän. Alluusioiden tulkintamahdollisuudet olivat kaikissa käännöksissä muuttuneet sikäli, että melko harvat suomennetut alluusiot olivat enää kohdelukijoiden tunnistettavissa. Toisaalta myös kulttuuritöyssyt olivat harvinaisia. Erot 1940- ja 1980-luvun suomennosten välillä näkyivätkin pseudo-allusiivisissa ja ei-allusiivisissa tulkintamahdollisuuksissa. 1980-luvun suomennoksissa vieraat alluusiot oli johdonmukaisesti säilytetty niin, että käännetyt alluusiot voitiin tulkita pseudo-alluusioiksi. Sen sijaan 1940-luvun suomennoksissa vieraita alluusioita oli usein muokattu tai jätetty pois tavalla, joka johti ei-allusiiviseen tulkintaan. Kohdelukijoiden kannalta 1980-luvun suomennettujen alluusioiden tulkitseminen lienee vaatinut jonkin verran enemmän vaivaa. Toisaalta pseudo-allusiivisten käännösten pohjalta oli useimmiten mahdollista rakentaa koherentti tulkinta, ja monesti ne jopa välittivät samankaltaisia funktioita kuin lähdetekstin alluusiot. 1940-luvun suomennosten muokkaukset ja poistot periaatteessa helpottivat tulkintaa, mutta mahdollisia kulttuuritöyssyjä esiintyi edelleen, jopa kääntäjän tekemien muutosten seurauksena. 1940-luvun suomennoksissa myös käännettyjen alluusioiden funktiot olivat muuttuneet enemmän lähdetekstin alluusioihin nähden. Kaiken kaikkiaan 1980-luvun suomennokset olivat lähempänä oman aikansa hyvän käännöksen piirteitä. Toisaalta alluusioiden muokkaaminen sai 1940-luvun suomennokset muistuttamaan enemmän perinteistä arvoituksen ratkaisuun keskittyvää salapoliisiromaania, joten tältä osin ne lienevät vastanneet kohdelukijoiden odotuksia. Kulttuurikontekstin vaikutus siis näkyi sekä käännösstrategioissa että käännettyjen alluusioiden tulkintamahdollisuuksissa. Tutkimustuloksissa korostui kuitenkin myös se, että lähdetekstin alluusion pintamerkitys saattaa vaikuttaa käännösratkaisuihin. Lisäksi käännetyt pseudo-alluusiot saattavat välittää samankaltaisia funktioita kuin lähdetekstin alluusiot. Toisin kuin yleensä on esitetty, kohdelukijoille vieraiden alluusioiden säilyttäminen saattaakin siis olla toimiva ratkaisu.

Mössbauer spectra of iron oxides in the bulk and nanocrystalline states

Magnetic nanoparticles are very important in modern industry. These particles are used in many different spheres of life. Nanoparticles have unusual physical and chemical properties connected both with quantum dimensional effects and with the increased role of the surface atoms. Most clearly the difference between the properties of bulk materials and nanoparticles can be seen in the magnetic properties of these materials. The most typical magnetic properties of nanomaterials are superparamagnetism with the size of the cluster from 1 to 10 nm; single-domain magnetic state of nanoclusters and nanostructures up to 20 nm; magnetization processes connected with magnetic cluster ordering and with its forms and sizes; quantum magnetic tunneling effects when magnetization changes by jumps and giant magnetoresistance effects. For research of the magnetic properties of iron-containing nanostructures, it is convenient to apply Mӧssbauer spectroscopy. In this work a number of nano-sized samples of iron oxides were examined by Mössbauer spectroscopy. The Mössbauer spectra of nanoparticles with various sizes were obtained. Mössbauer spectra of iron oxide nanoparticles were compared with the spectra of bulk samples. It was shown how the spectra of iron oxide nanoparticles change depending on the particle sizes.