Analytical approaches for the measurement of sulfide in biological and pharmaceutical fields

Hydrogen sulfide (H2S) is a widely recognized gasotransmitter, with key roles in physiological and pathological processes. The accurate quantification of H2S and reactive sulfur species (RSS) may hold important implications for the diagnosis and prognosis of various diseases. However, H2S species quantification in biological matrices is still a challenge. Among the sulfide detection methods, monobromobimane (MBB) derivatization coupled with reversed phase high-performance liquid chromatography (RP-HPLC) is one of the most reported. However, it is characterized by a complex preparation and time-consuming process, which may alter the actual H2S level. Moreover, quantitative validation has still not been described based on a survey of previously published works. In this study, we developed and validated an improved analytical protocol for the MBB RP-HPLC method. Main parameters like MBB concentration, temperature, reaction time, and sample handling were optimized, and the calibration method was further validated using leave-one-out cross-validation (CV) and tested in a clinical setting. The method shows high sensitivity and allows the quantification of H2S species, with a limit of detection (LOD) of 0.5 µM and a limit of quantification (LOQ) of 0.9 µM. Additionally, this model was successfully applied in measurements of H2S levels in the serum of patients subjected to inhalation with vapors rich in H2S. In addition, a properly procedure was established for H2S release with the modified MBB HPLC-FLD method. The proposed analytical approach demonstrated the slow-release kinetics of H2S from the multilayer Silk-Fibroin scaffolds with the combination of different H2S donor’s concentration with respect to the weight of PLGA nanofiber. In the end, some efforts were made on sulfide measurements by using size exclusion chromatography fluorescence/ultraviolet detection and inductively coupled plasma-mass spectrometry (SEC-FLD/UV-ICP/MS). It’s intended as a preliminary study in order to define the feasibility of a separation-detection-quantification platform to analyze biological samples and quantify sulfur species.

Gases e ruídos em edificações para suínos: aplicação das normas NR-15, CIGR e ACGIH

Swine production represents an important segment of Brazilian economy, and the possibility of increasing production is eminent mainly if considered the low pork consumption when compared to other meat and the consumption of other countries. The increasing need in the international market demands show that in a near future the commercial barriers will be based on welfare, in the protection of the environment as well as in the worker's legislation. Little knowledge is available in the subject of worker's standards in the environmental agents in rural activities as well as the air quality under Brazilian conditions. The objectives of this research were to apply the main used standards related to noise and gases and to estimate occupational risk using measurements of noise level, hydrogen sulfide, methane and oxygen in swine housing, in piglet's nursery and finishing. The results showed that the continuous noise level were below the one found in the standards, however there were observed differences (P < 0.05) in relation to the noise level measured in piglet's nursing cages and in semi-slatted floor. The respective concentrations of hydrogen sulfide and methane were less than 1 ppm and less than 0,1% by volume, which was lower than the recommended limits in NR-15, CIGR and ACGIH. The oxygen level was 21% in average.

Trialing wetlands to treat coal mining wastewaters in a low rainfall, high evaporation environment

The large number of wetlands treating mining wastewaters around the world have mostly been constructed in temperate environments. Wetlands have yet to be proven in low rainfall, high evaporation environments and such conditions are common in many parts of Australia. BHP Australia Coal is researching whether wetlands have potential in central Queensland to treat coal mining wastewaters. In this region, mean annual rainfall is < 650 mm and evaporation > 2 000 mm. A pilot-scale wetland system has been constructed at an open-cut coal mine. The system comprises six treatment cells, each 125 m long and 10 m wide. The system is described in the paper and some initial results presented. Results over the first fourteen months of operation have shown that although pH has not increased enough to enable reuse or release of the water, sulfate reduction has been observed in parts of the system, as shown by the characteristic black precipitate and smell of hydrogen sulfide emanating from the wetlands. These encouraging signs have led to experiments aimed at identifying the factors limiting sulfate reduction. The first experiment, described herein, included four treatments where straw was overlain by soil and the water level varied, being either at the top of the straw, at the top of the soil, or about 5 cm above the soil. The effect of inoculating with sulfate-reducing bacteria was investigated. Two controls were included, one covered and one open, to enable the effect of evaporation to be determined. The final treatment consisted of combined straw/cattle manure overlain with soil. Results showed that sulfate reduction did occur, as demonstrated by pH increases and lowering of sulfate levels. Mean pH of the water was significantly higher after 19 days; in the controls, pH was < 3.3, whereas in the treatments, pH ranged from 5.4 to 6.7. The best improvement in sulfate levels occurred in the straw/cattle manure treatment. (C) 1997 IAWQ. Published by Elsevier Science Ltd.

Structural changes in mixed Langmuir-Blodgett films upon nanoparticle formation

The formation of CdS nanoparticles by reacting mixed Langmuir-Blodgett films of arachidic acid and either octadecylamine or dimethyldioctadecylammonium nitrate on a cadmium-containing subphase with hydrogen sulfide gas has resulted in the identification of a number of structural changes, observed using grazing incidence X-ray diffraction. In the case of octadecylamine, the structure after reaction is a hexagonal close-packed array of surfactant-stabilized nanoclusters, with a lattice constant of a = 17.65 Angstrom. In both octadecylamine and dimethyldioctadecylammonium nitrate films, the presence of a unit cell tilted at 38degrees to the plane of the substrate was found. Despite these changes, the average nanoparticle size was unaffected by the addition of either second component to the film.

Gás sulfídrico nas redes de águas residuais

Os colaboradores que realizam a sua atividade profissional, no setor das águas residuais, reconhecem que a sua atividade é perigosa. Esse conhecimento, foi adquirido pela experiência obtida ao longo dos anos, pelas várias formações e pelas notícias de acidentes, muitas vezes mortais, que têm acontecido na atividade. Muita das vezes, os colaboradores têm dificuldade em aceitar o risco, porque na realidade não existe um histórico conhecido do que se passa no interior das redes de drenagem de águas residuais e consideram que o risco é apenas teórico. Os portugueses são um Povo muito ligado à Cultura Popular,e são os ditados populares que melhor sintetiza as ideias expressas pelos trabalhador português “Ver para Crer, Como São Tomé” (SOUSA, Marcelo Rebelo de, Os Evangelhos de 2001, Lisboa, Bertrand Editora, 2001]. O objetivo principal com este trabalho, foi evidenciar que existem gases no interior das caixas de visita, mas principalmente, demostrar que seu aparecimento e respetiva concentração, é variável e que ocorre sem aviso prévio! Tornando assim, os trabalhos no interior das caixas de visita e das redes de drenagem de águas residuais domesticas, locais perigosos para quem opera no seu interior, sem a correta utilização dos equipamentos de proteção individual, (Epis e Epc). Sendo necessário, reforçar, a constante informação e formação para a utilização dos equipamentos de proteção individual e coletiva. Com o presente estágio, pretendeu-se iniciar um registo histórico de medições nas redes de drenagem de águas residuais domésticas. Com o resultado das medições que serão obtidas, pretende-se uma “Radiografia Fotográfica” ao interior das caixas de visitas das redes de drenagem de águas residuais. Com os resultados deste estudo, pretende-se contribuir de forma clara e objetiva, para os perigos iminentes que existem efetivamente, no interior das redes de saneamento, com a presença de altas concentrações de gás sulfídrico, nocivo para a vida humana!

Use of swine waste-derived biogas to enhance microalgae productivity.

The effects of swine wastewater-derived biogas on microalgae productivity were determined. Experiments were conducted in a closed photobioreactor containing digestate effluent as culturing media and biogas in the headspaceas source of CO2. Experiments were carried out under mixothrophic and autothrophic conditions. Results showed that autotrophic growth rate (0.6 d-1)was twofoldfaster than mixotrophic. Frequent reinjections of biogas containing up to 2,000 ppm of hydrogen sulfide was not inhibitory to microalgae growth. The rapid removal of H2S in the system suggests photobioreactors can be an interesting alternative to biogas purification. A model to estimate microalgae productivity based on the amount of available CO2, inorganic and organic carbon was developedand showed good data fit correlation (r²= 0.99).

Validation of an analytical method for nitrous oxide (N2O) laughing gas by headspace gas chromatography coupled to mass spectrometry (HS-GC-MS): Forensic application to a lethal intoxication.

Drug abuse is a widespread problem affecting both teenagers and adults. Nitrous oxide is becoming increasingly popular as an inhalation drug, causing harmful neurological and hematological effects. Some gas chromatography-mass spectrometry (GC-MS) methods for nitrous oxide measurement have been previously described. The main drawbacks of these methods include a lack of sensitivity for forensic applications; including an inability to quantitatively determine the concentration of gas present. The following study provides a validated method using HS-GC-MS which incorporates hydrogen sulfide as a suitable internal standard allowing the quantification of nitrous oxide. Upon analysis, sample and internal standard have similar retention times and are eluted quickly from the molecular sieve 5Å PLOT capillary column and the Porabond Q column therefore providing rapid data collection whilst preserving well defined peaks. After validation, the method has been applied to a real case of N2O intoxication indicating concentrations in a mono-intoxication.

Pharmacotherapy and analysis of gaseous mediators in hypertensive patients

OBJECTIVE To evaluate the effect of using antihypertensive classes of drugs of the calcium channel antagonists and inhibitors of angiotensin-converting enzyme in plasma concentrations of hydrogen sulfide and nitric oxide in patients with hypertension. METHODS Cross-sectional study with quantitative approach conducted with hypertensive patients in use of antihypertensive classes of drugs: angiotensin-converting enzyme inhibitors or calcium channel antagonists. RESULTS It was found that the concentration of plasma nitric oxide was significantly higher in hypertensive patients that were in use of angiotensin-converting enzyme inhibitors (p<0.03) and the hydrogen sulphide concentration was significantly higher in hypertensive plasma in use of calcium channel antagonists (p<0.002). CONCLUSION The findings suggest that these medications have as additional action mechanism the improvement of endothelial dysfunction by elevate plasma levels of vasodilatory substances.

Validación y cuantificación de sulfuros de hidrógeno (H2S) en agua intersticial de sedimentos marinos recientes

Para la validación del método analítico de cuantificación de sulfuros en aguas intersticiales se analizaron varios parámetros: la especificidad, determinándose que el único compuesto formado es el azul de metileno con absorbancia máxima a 670 nm; la linealidad en intervalo de 3 a 36 μM (y= 0,0319 x +0,0142) con coeficiente de regresión 0,9983; la repetitividad obteniéndose promedio de 0,1043% y CV de 5,0811. La reproducibilidad se analizó con la prueba t de Student, determinándose que t calculado

Role of fluid mixing in deep dissolution of carbonates

The presence of cavities filled with new minerals in carbonate rocks is a common feature in oil reservoirs and lead-zinc deposits. Since groundwater equilibrates rapidly with carbonates, the presence of dissolution cavities in deep carbonate host rocks is a paradox. Two alternative geochemical processes have been proposed to dissolve carbonates at depth: hydrogen sulfide oxidation to sulfuric acid, and metal sulfide precipitation. With the aid of geochemical modeling we show that mixing two warm solutions saturated with carbonate results in a new solution that dissolves limestone. Variations in the proportion of the end-member fluids can also form a supersaturated mixture and fill the cavity with a new generation of carbonate. Mixing is in general more effective in dissolving carbonates than the aforementioned processes. Moreover, mixing is consistent with the wide set of textures and mineral proportions observed in cavity infillings.

When gas analysis assists with postmortem imaging to diagnose causes of death.

Postmortem imaging consists in the non-invasive examination of bodies using medical imaging techniques. However, gas volume quantification and the interpretation of the gas collection results from cadavers remain difficult. We used whole-body postmortem multi-detector computed tomography (MDCT) followed by a full autopsy or external examination to detect the gaseous volumes in bodies. Gases were sampled from cardiac cavities, and the sample compositions were analyzed by headspace gas chromatography-mass spectrometry/thermal conductivity detection (HS-GC-MS/TCD). Three categories were defined according to the presumed origin of the gas: alteration/putrefaction, high-magnitude vital gas embolism (e.g., from scuba diving accident) and gas embolism of lower magnitude (e.g., following a traumatic injury). Cadaveric alteration gas was diagnosed even if only one gas from among hydrogen, hydrogen sulfide or methane was detected. In alteration cases, the carbon dioxide/nitrogen ratio was often >0.2, except in the case of advanced alteration, when methane presence was the best indicator. In the gas embolism cases (vital or not), hydrogen, hydrogen sulfide and methane were absent. Moreover, with high-magnitude vital gas embolisms, carbon dioxide content was >20%, and the carbon dioxide/nitrogen ratio was >0.2. With gas embolisms of lower magnitude (gas presence consecutive to a traumatic injury), carbon dioxide content was <20% and the carbon dioxide/nitrogen ratio was often <0.2. We found that gas analysis provided useful assistance to the postmortem imaging diagnosis of causes of death. Based on the quantifications of gaseous cardiac samples, reliable indicators were determined to document causes of death. MDCT examination of the body must be performed as quickly as possible, as does gas sampling, to avoid generating any artifactual alteration gases. Because of cardiac gas composition analysis, it is possible to distinguish alteration gases and gas embolisms of different magnitudes.

Rikkiyhdisteiden laskenta simuloinneissa

Diplomityön tarkoituksena on tutkia eri laskentamenetelmien soveltuvuutta kevyiden rikkiyhdisteiden laskentaan ja kuinka mitatusta kaasu-neste tasapainotiedoista sovitetut binääriset vuorovaikutusparametrit parantavat kaasu-neste tasapainojen laskentaa simuloinneissa. Kirjallisuusosassa paneudutaan kevyisiin rikkiyhdisteisiin ja niiden aineominaisuuksiin. Lisäksi käsitellään öljynjalostuksessa nykyisin käytettäviä ja uusia kehitteillä olevia rikinpoistomenetelmiä.Kokeellisessa osassa tarkastellaan eri laskentamenetelmien soveltuvuutta rikkiyhdisteiden ja kevyiden hiilivetyjen kaasu-neste tasapainon laskentaan. Mitatusta rikkiyhdisteiden ja hiilivetyjen kaasu-neste tasapainoista sovitetaan binäärisiä vuorovaikutusparametrejä tarkentamaan käytettäviä laskentamenetelmiä. Osassa verrataan binääristen seosten mittaustuloksia eri laskentamenetelmillä saatuihin simulointituloksiin. Tarkasteluiden perusteella tehdään johtopäätöksiä laskentamenetelmien soveltuvuudesta kevyiden hiilivetyjen ja rikkiyhdisteiden laskentaan. Tarkastellaan kahden prosessin (rikkivetystripperi ja butaaninpoistokolonni) rikkiyhdisteiden laskentaa. Prosesseille tehdään taseajot, joista saatuja analyysituloksia verrataan simulointien antamiin tuloksiin. Työssä tarkastellaan myös veden liukoisuuden laskentaa ja mahdollisten laskentamenetelmien käytön vaikutusta rikkiyhdisteiden laskentaan.

Kaivosteollisuudessa syntyvän kipsin hyödyntäminen

Diplomityön tarkoituksena oli tutkia ja kehittää käyttökohde kaivosteollisuudessa syntyvälle märälle kipsisivuvirralle, joka sisältää metalliepäpuhtauksina alumiinia, rautaa ja mangaania ja jonka määrä on noin 1 000 000 t/a. Kirjallisuuden pohjalta tutkittiin aluksi mahdollisuutta hyödyntää kipsiaines asfaltti- ja sementtiteollisuuden raaka-aineena. Sementin joukkoon lisätään tavallisesti noin 5 p-% kipsiä, mutta harvinaisimpiin sementtilaatuihin sitä voidaan lisätä jopa 30 p-%. Tästä huolimatta vain pieni osa tutkimuksen kohteessa syntyvästä kipsisivuvirrasta voitaisiin hyödyntää tässä sovelluksessa. Lisäksi kipsisivuvirran sisältämät epäpuhtaudet täytyisi poistaa tai saattaa inaktiiviseen muotoon. Myöskään sen kosteuspitoisuus ei saisi olla suuri. Näin ollen tämän kipsisivuvirran hyödyntäminen asfaltti- ja sementtiteollisuuden lisäaineena ei ole mahdollista Seuraavaksi harkittiin kipsin kierrättämistä, jolloin yhtenä vaihtoehtona oli hajottaa kipsi termisesti rikkioksideiksi ja valmistaa niistä rikkihappoa. Taloudellisista syistä hajoamistuotteen on oltava rikkitrioksidia, josta voitaisiin veteen imeyttämällä valmistaa rikkihappoa. Kipsin hajottaminen termovaa´alla osoitti, että kipsi vaatii noin 1400 ºC:n lämpötilan ja haihtuvat komponentit ovat H2O, SO ja SO2, muttei SO3. Alempien oksidien muuttaminen rikkihapoksi vaatisi katalyyttisen hapetuksen, mikä olisi käytännössä liian kallista. Toisena vaihtoehtona kipsin kierrättämiseksi tutkittiin sen biologista pelkistämistä rikkivedyksi ja kalsiumhydroksidilietteeksi. Laboratoriossa Ca(OH)2-lietteestä valmistettiin hiilidioksidin avulla kalsiumkarbonaattia, jolloin päästiin 90 %:n kalsiumhydroksidin konversiossa. Lisäksi alumiinihydroksidi saatiin erotettua kipsilietteestä kokeellisesti hydrosyklonin avulla. Diplomityössä päädyttiin siihen, että sulfaatin biologinen pelkistäminen ja alumiinihydroksidin mekaaninen erotus jatkuvatoimisesti on varteenotettava vaihtoehto kipsisivuvirran hyödyntämiseksi.

Estudo da adsorção de hidrogênio e sulfeto na superfície de paládio: aspectos experimentais (eletroquímica) e teóricos (ab initio e Teoria do Funcional da Densidade)

The adsorption of H and S2- species on Pd (100) has been studied with ab initio, density-functional calculations and electrochemical methods. A cluster of five Pd atoms with a frozen geometry described the surface. The computational calculations were performed through the GAUSSIAN94 program, and the basis functions adapted to a pseudo-potential obtained by using the Generator Coordinate Method adapted to the this program. Using the cyclic voltammetry technique through a Model 283 Potentiostat/Galvanostat E.G.&G-PAR obtained the electrochemical results. The calculated chemisorption geometry has a Pd-H distance of 1.55Å, and the potential energy surface was calculated using the Becke3P86//(GCM/DFT/SBK) methodology. The adsorption of S2- ions on Pd surface obtained both through comparison between the experimental and theoretical results, at MP2 level, suggest a S2- absorption into the metallic cluster. The produced Pd-(S2-) system was show to be very stable under the employed experimental conditions. The paper has shows the powerful aid of computational methods to interpret adsorption experimental data.

Environmental comfort in constructions for Sindi and Guzera calves in the agreste region of the State of Paraiba, Brazil

The objective of this study was to evaluate the quality of air, bioclimatic indexes of facilities and physiological indices of Guzera and Sindhi calves, reared in climatic conditions of Agreste. The study was conducted at the experimental station of Alagoinha, PB, Brazil, using 16 calves of Sindi and Guzerá races. The average concentration of oxygen (20.85%), ammonia (1.99 ppm), carbon monoxide (<0.01 ppm), methane (0.13 ppm) and hydrogen sulfide (<0.01) within facilities, were within the limits established by the Brazilian and international standards, for both animals and workers. The bioclimatic index of temperature and humidity and the temperature of the black globe and humidity index were within the thermal comfort zone for cattle in most of the experimental period, the mean values of respiratory frequency (26.0 min mov-1) and skin temperature (32.3 °C) were higher in the hottest time of the day (1 pm) and rectal temperature (39.3 ºC) in the late afternoon (5 pm), but remained within normal ranges for the studied races. The races have good adaptability to climatic conditions in the region of the Paraibano Agreste, Brazil.