ABSTRACT
The use of bacteria to remove sulfur from crude oil or petroleum distillates is a novel concept that presents an alternative biotechnology to the current technology of hydrodesulfurization (HDS). Sulfur must be removed from crude oils prior use. The burning of fossil fuels containing sulfur releases sulfur dioxide into the atmosphere causing acid rain. The aim of this work is to determine the sulfate concentration by ion chromatography (IC), and calculate the percentage of transformation of organic bound sulfur, that is converted to sulfate, and estimate the efficiency of bacteria in desulfurization. IC is a suitable method for sulfate concentration determination. However, when chloride concentrations are significantly high, interference of the sulfate signal does occur. In this case, it could be avoided by diluting samples. A Dionex Model 2000i/SP IC system, with an anionic pre-column (Dionex AG4A), an anion separator column (Dionex AS4A), a suppressor column (Dionex AMMS-II), and a conductivity detector was used. The eluent (21 mM NaOH) and regenerant (electrolyzed 18 M omega/cm water) flow-rates were 1.0 and 2.0 ml/min, respectively. The sample loop volume was 10 microliters and the conductivity sensitivity was 30 muS. The diluted samples were filtered through a 0.45-micron filter before injection. The highest sulfate concentration detected was 24.10 mg/l, corresponding to a maximal conversion rate of 10% in a month. Sulfate ions were not detected in control samples. The correlation coefficient for a linear least squares fit was 0.99 (p < 0.001). The minimal concentration that we can read was 0.02 mg/l and this concentration corresponded to the limit of detection obtained under the conditions employed in this study. IC is an economical, sensitive and accurate way to estimate the sulfate concentrations in microbiological samples.
Subject(s)
Bacteria/metabolism , Chromatography/methods , Hydrocarbons, Aromatic/metabolism , Sulfates/metabolism , Bacillus/metabolism , Chemical Precipitation , Chlorides/analysis , Gram-Positive Endospore-Forming Bacteria/metabolism , Silver Compounds , Staphylococcus/metabolism , Thiophenes/metabolismABSTRACT
The mercury concentrations in wastewater and sewage sludge of a stabilization pond system have been evaluated. The system is built by three parallel facultative ponds followed by two systems of three maturation ponds in series. The samples of wastewater and sludge were digested using nitric acid and placed into a Parr-type bomb for 4 h at 110 degrees C. Mercury was measured by Cold Vapour Atomic Absorption Spectrometry (CV-AAS) at 253.7 nm with sodium tetrahydroborate as reductant. The methodologies were checked with an USEPA quality control sample, a standard reference material from NIST and with another method of mineralization (cold mineralization) showing good results. Concentrations of mercury in wastewater between 1.47 +/- 0.75 microgl(-1) have been found at the entrance of the system and 0.74 +/- 0.0 microgl(-1) at the exit, while in sludge the results were between 0.29 +/- 0.12 microgkg(-1) in the facultative pond and 0.04 +/- 0.02 microgkg(-1) in the second maturation pond (exit).
ABSTRACT
An important factor contributing to the development of ion chromatography (IC) has been the need for repetitive analyses of samples with high ionic contents and samples available in microvolumes. IC was selected for the determination of Cl, NO3, SO(2-)4 and PO(3-)4 anions in tear fluid and serum from ten human volunteers of both sexes, seven young-adult black vultures (Coragyps atratus) and three young-adult chickens (Gallus gallus domesticus). The samples were analysed on a Dionex Model 2000i/SP ion-exchange chromatograph equipped with an anion guard column (Dionex IonPac AG4A), anion separator column (Dionex IonPac AS4A), suppressor column (Dionex AMMS-II) and a conductivity detector. The flow-rte of the mobile phase, 1.7 mM NaHCO3 - 1.8 mM Na2CO3 was set at 2.0 ml/min. The R.S.D. was calculated to be less than 1.5% for all anions. In the human, black vulture and chicken serum samples, the NO3, PO(3-)4 and SO(2-)4 anion contents were higher than in tears; for Cl the reverse was found. No correlation was found amongst the anion concentrations present in the tear fluid and blood serum in all samples (p > 0.05). With no sample treatment, column maintenance was required.
