Final Sample Volume Research Articles

Clay sedimentation and consolidation behaviour in tailing storage facilities over mine lifetime

Changes in the tailing properties (increasing clay mineral content and fine particles) and poor operation of the dewatering systems have negative impacts on the Tailing Storage Facilities (TSF) of the Shahrbabak copper complex. The design solid concentration of the thickened tailings is 63 wt.% in the Shahrbabak paste plant but it is well below the design value right now (approx. 55 wt.%). The aim of this work is to find the effects of the clay mineral and dewatering operations on the water recovery and tailing dam capacity. The understudied samples were taken from the thickener underflow and prepared at the required solid concentrations (55, 60, 65, and 70 wt.%). The results obtained showed that the initial settled density varied from 1.044 to 1.146 t/m3 by increasing the solid concentrations from 55 to 63 wt.%. Furthermore, the shrinkage limit density of the two solid concentrations was recorded at 1.52 and 1.62 t/m3, and the crack volume was estimated at 6.3% and 7.2% of the final sample volume. Also the sub-aerial tailing beach slope in the upper quarter and the remainder of TSF was too low and exhibited 2.0% and 1.0%, respectively. However, it is far from the design values (3.5%, 2.5%, and 1.7% from head of the beach to the end). Thus it is clear that the clay minerals and fine particles hold more water in their inner network and occupy a more TSF volume. Nevertheless, the beach slope can be increased by improving the thickener performance and removing the leakage and other periodic water, although it seems impractical to achieve the design value due to the changes in the tailing properties.

The Effect of Credit Risk Management and Capital Adequacy on Financial Performance of Business Banks

The main purpose of the research to study the effect of credit risk management and capital adequacy on financial performance of business banks from 2009 to 2014. The statistical population of the research is all state and private banks and final sample volume is 25 banks based on available information. In this research, amount of loans, previous maturity of credits, loss reserve on loans and previous maturity of credits, liquidity ratio and capital adequacy of banks were used to study their effects on the performance of banks (return on asset). The results of data analysis using multivariate - linear regression at 95% confidence level indicated that there is a negative relationship between loss reserve on loans and previous maturity of credits and banks’ performance. On the other side, the results indicated that there is a positive relationship between liquidity ratio and capital adequacy ratio with banks’ performance.Keywords: Credit Risk, Capital Adequacy, Financial Performance, Return of Assets

Lactobacillus delbrueckii subsp. bulgaricus Proteinase: Purification by Ion-Exchange and Hydrophobic Interaction Chromatography

In order to purify proteinase from Lactobacillus delbrueckii subsp. bulgaricus, chromatography methods including ion-exchange and hydrophobic interaction were combined. Chromatographic conditions were structured and optimized. The final sample volume, flow rate, and length of gradient for anion exchange chromatography were 20 mL, 5 mL/min and 10 column volume length of gradient, in that order. Besides, the flow rate and length of gradient for hydrophobic interaction chromatography were 1 mL/min and 10 column volume. Proteinase was purified up to 43-fold with a specific activity of 54.4 U/mg protein, and the recovery of 46.6%. The molecular weight of the purified proteinase was about 40 kDa.

Determination of temozolomide in serum and brain tumor with micellar electrokinetic capillary chromatography

Micellar electrokinetic capillary chromatographic (MEKC) with photodiode-array detection was applied to determine temozolomide (TMZ) in human serum and brain tumor. The limit of quantitation (LOQ) was 0.096 μg/mL using 325 nm as detection wavelength. The method made possible that the TMZ could be detected in in vivo serum samples without sample pretreatment. In order to detect TMZ at lower concentration, an extraction with ethyl acetate was applied to preconcentrate the analyte. Small amount of brain tumor tissues (less than 1 g) were lyophilized and pretreated using extraction as a clean up and concentrating step. After removing the organic solvent a final sample volume of only 10 μL was analyzed. The obtained peak concentrations (8.2–10.1 μg/mL) and T max (44–65 min) of TMZ in serum were similar to the data reported by others, the in vivo TMZ concentrations found in brain tumor ranged between 0.061 and 0.117 μg/g.

Lipoprotein separation in a novel iodixanol density gradient, for composition, density, and phenotype analysis

Separation of lipoproteins by traditional sequential salt density floatation is a prolonged process ( approximately 72 h) with variable recovery, whereas iodixanol-based, self-generating density gradients provide a rapid ( approximately 4 h) alternative. A novel, three-layered iodixanol gradient was evaluated for its ability to separate lipoprotein fractions in 63 subjects with varying degrees of dyslipidemia. Lipoprotein cholesterol, triglycerides, and apolipoproteins were measured in 21 successive iodixanol density fractions. Iodixanol fractionation was compared with sequential floatation ultracentrifugation. Iodixanol gradient formation showed a coefficient of variation of 0.29% and total lipid recovery from the gradient of 95.4% for cholesterol and 84.7% for triglyceride. Recoveries for VLDL-, LDL-, and HDL-cholesterol, triglycerides, and apolipoproteins were approximately 10% higher with iodixanol compared with sequential floatation. The iodixanol gradient effectively discriminated classic lipoproteins and their subfractions, and there was evidence for improved resolution of lipoproteins with the iodixanol gradient. LDL particles subfractionated by the gradient showed good correlation between density and particle size with small, dense LDL (<25.5 nm) separated in fractions with density >1.028 g/dl. The new iodixanol density gradient enabled rapid separation with improved resolution and recovery of all lipoproteins and their subfractions, providing important information with regard to LDL phenotype from a single centrifugation step with minimal in-vitro modification of lipoproteins.

Determination of nitrites by the formation of bisazo dye

AbstractA facile, sensitive and rapid spectrophotometric method for the determination of nitrite is presented. The method involves the reaction of nitrite with 4-aminoazobenzene under acidic conditions in the presence of a bromide ion allowing to complete the diazotization reaction almost instantaneously. The formed diazonium ion is then coupled with acetyl acetone to give bisazo dye in an aqueous alkaline medium having maximum absorption at 500 nm. The molar absorptivity and Sandell’s sensitivity of the method were found to be 4.2 × 104 dm3 mol−1 cm−1 and 1.1 ng cm−2, respectively. The system obeys the Beer’s law within the concentration range of 0.1–9 µg of nitrite in the final sample volume of 10 cm3. Optimum reaction conditions were evaluated and the influence of ionic interference on the determination of nitrite has been studied. The developed method has been applied in the determination of nitrite in water and soil samples, and the results were statistically evaluated.

Characterization of low density lipoprotein receptor ligand interactions by fluorescence resonance energy transfer

The low density lipoprotein receptor (LDLR) is the prototype of a family of cell surface receptors involved in a wide range of biological processes. A soluble low density lipoprotein receptor (sLDLR) and a tryptophan (Trp)-deficient variant human apolipoprotein E3 (apoE3) N-terminal domain (NT) were used in binding studies. The sole cysteine in apoE3-NT was covalently modified with an extrinsic fluorescence probe, N-(iodoacetyl)-N'-(5-sulfo-1-napthyl)ethylenediamine (AEDANS), and the protein was complexed with lipid. Incubation of sLDLR with AEDANS-Trp-null apoE3-NT dimyristoylphosphatidylcholine (DMPC) disks, but not lipid-free AEDANS-apoE, induced an enhancement in AEDANS fluorescence emission intensity (excitation, 280 nm) consistent with intermolecular energy transfer from excited Trp in sLDLR to receptor-bound apoE. Ligand binding to sLDLR required calcium and was saturable. In competition binding assays, unlabeled apoE3-NT DMPC inhibited AEDANS-apoE DMPC binding to sLDLR more effectively than low density lipoprotein. Fluorescence changes in this system reflected pH-dependent ligand binding and release from sLDLR consistent with models derived from the X-ray crystal structure of the receptor at endosomal pH. Intermolecular energy transfer from excited Trp in LDLR family members to fluorescently tagged ligands represents a sensitive and convenient assay for the characterization of the myriad molecular interactions ascribed to this family of receptor.

Human C4b-binding Protein, Structural Basis for Interaction with Streptococcal M Protein, a Major Bacterial Virulence Factor

Human C4b-binding protein (C4BP) protects host tissue, and those pathogens able to hijack this plasma glycoprotein, from complement-mediated destruction. We now show that the first two complement control protein (CCP) modules of the C4BP alpha-chain, plus the four residues connecting them, are necessary and sufficient for binding a bacterial virulence factor, the Streptococcus pyogenes M4 (Arp4) protein. Structure determination by NMR reveals two tightly coupled CCP modules in an elongated arrangement within this region of C4BP. Chemical shift perturbation studies demonstrate that the N-terminal, hypervariable region of M4 binds to a site including strand 1 of CCP module 2. This interaction is accompanied by an intermodular reorientation within C4BP. We thus provide a detailed picture of an interaction whereby a pathogen evades complement.

Novel matrix separation—on-line pre-concentration procedure for accurate quantification of palladium in environmental samples by isotope dilution inductively coupled plasma sector field mass spectrometry

A method for accurate on-line ultra-trace analysis of palladium by inductively coupled plasma mass spectrometry has been developed. After separation of interfering cations by cation exchange chromatography, palladium was selectively adsorbed on to a C18 micro-column on-line which had been reversibly loaded with the complexing agent N,N-diethyl-N′-benzoylthiourea (DEBT). The palladium complex formed was eluted with methanol and introduced into an ICP-SFMS via microconcentric nebulization with membrane desolvation. Quantification of palladium was carried out by isotope dilution analysis. The results obtained via the isotope ratios of 105Pd/108Pd and 106Pd/108Pd agreed within their measurement uncertainty. For solid samples (total intake 100 mg, final sample volume of 10 mL after closed vessel microwave digestion) the limit of detection was 0.24 ng g−1 palladium (2 mL of digested sample). The necessity of combining matrix separation and pre-concentration for elimination of spectral interferences was demonstrated using soil samples. The method was validated by analysis of the certified reference material BCR-723 (road dust).

Multielement Determination of Trace Metals in Seawater by Inductively Coupled Plasma Mass Spectrometry after Tandem Preconcentration Using a Chelating Resin

Abstract A tandem preconcentration method using a chelating resin was exploited for simultaneous multielement determination of trace metals in seawater by inductively coupled plasma mass spectrometry (ICP-MS). In the first preconcentration step, 500 mL of seawater sample was adjusted to pH 6.0, and the adsorption of trace metals on 0.4 g of Chelex-100 resin in dry weight was carried out at 55 °C. After equilibrium, the resin was collected on a glass filter and rinsed with 30 mL of ammonium acetate solution (pH 6.0) to reduce major elements such as Na, K, Mg, and Ca that had been partly adsorbed on the resin. Then, trace metals on the resin were eluted with 7.5 mL of 2 M nitric acid and collected in a 30 mL polypropylene bottle. In the second preconcentration step, the mixture of the filtrate and the rinsing solution obtained in the first step was adjusted to pH 4.0, and metal adsorption on another 0.4 g of Chelex-100 resin was carried out at 20 °C. In a similar manner to the first step, the resin collected on a glass filter was rinsed with 10 mL of ammonium acetate solution (pH 4.0), and trace metals adsorbed on the resin were eluted with 6 mL of 2 M nitric acid. This eluate was taken into the same polypropylene bottle as used in the first step. The final sample volume thus obtained was 15 mL including 1.5 mL of internal standard solution. Then a 33-fold preconcentration factor was achieved, where the recoveries for 33 elements were larger than 80%. The analytical results for trace metals in coastal seawater reference material (CASS-4) were in fairly good agreement with the certified or information values after correction with the recovery values. The coastal seawater samples from the Ise Bay and the Take Island were also analyzed by the present method. The concentrations for 20 trace metals in the Ise Bay coastal seawater were found to be more than 2-fold larger than those in the Take Island coastal seawater, indicating considerable anthropogenic pollution in the Ise Bay area.

Chemical Modification of Cysteine Residues Is a Misleading Indicator of Their Status as Active Site Residues in the Vitamin K-dependent γ-Glutamyl Carboxylation Reaction

The enzymatic activity of the vitamin K-dependent proteins requires the post-translational conversion of specific glutamic acids to gamma-carboxy-glutamic acid by the integral membrane enzyme, gamma-glutamyl carboxylase. Whether or not cysteine residues are important for carboxylase activity has been the subject of a number of studies. In the present study we used carboxylase with point mutations at cysteines, chemical modification, and mass spectrometry to examine this question. Mutation of any of the free cysteine residues to alanine or serine had little effect on carboxylase activity, although C343A mutant carboxylase had only 38% activity compared with that of wild type. In contrast, treatment with either thiol-reactive reagent 4-acetamido-4'-maleimidylstilbene-2,2'-disulfonic acid, disodium salt, or sodium tetrathionate, caused complete loss of activity. We identified the residues modified, using matrix-assisted laser desorption/ionization time of flight mass spectrometry, as Cys(323) and Cys(343). According to our results, these residues are on the cytoplasmic side of the microsomal membrane, whereas catalytic residues are expected to be on the lumenal side of the membrane. Carboxylase was partially protected from chemical modification by factor IXs propeptide. Although all mutant carboxylases bound propeptide with normal affinity, chemical modification caused a >100-fold decrease in carboxylase affinity for the consensus propeptide. We conclude that cysteine residues are not directly involved in carboxylase catalysis, but chemical modification of Cys(323) and Cys(343) may disrupt the three-dimensional structure, resulting in inactivation.

Ultratrace determination of phosphorus in ultrapurified water by a slope comparison method

The analytical method for the determination of phosphorus in ultrapurified water was developed. Ultrapurified water was evaporated to concentrate phosphorus and the final sample volume for analysis was 10 ml. In 0.55 mol l −1 HCl, orthophosphate forms molybdophosphate, and then the molybdophosphate forms ion associate with Malachite Green (MG), which can be collected on a tiny membrane filter (diameter: 5 mm, and effective filtering diameter: 2 mm). After the ion associate on the membrane filter is dissolved together with the membrane filter in 1 ml of methyl cellosolve (MC), the absorbance of MC solution is measured at 627 nm by a flow injection–spectrophotometric detection technique. When 10 ml of the sample solution was used for the procedures and absorbance measurement, the calibration graph is linear up to about 500 ng l −1 of phosphorus and the detection limit was 8 ng l −1 (S/N=3). For the determination of phosphorus in an ultrapurified water, 10–40 ml of sample solutions were transferred into poly(tetrafluoroethylene) (PTFE) beaker and evaporated to 5 ml or to dryness. To them, 0.003 mol l −1 HCl was added to get 10 ml of final solution, which was used as sample. Phosphate is determined by comparing the slope of the varied sample volume after evaporation/concentration with a slope of the standard calibration graph (a slope comparison method: SCM). The SCM enables to evaluate the concentration of phosphate in ultrapurified waters more sensitively and accurately.

Recovery of Polycyclic Aromatic Hydrocarbons During Solvent Evaporation with a Rotary Evaporator

Analytical behavior of dichloromethane solutions containing polycyclic aromatic hydrocarbons (PAHs) was systematically studied through evaporation in a rotary evaporator. Starting sample concentration levels for each PAH were 0.167 w g/mL (concentrated) and 0.0167 w g/mL (diluted). Solvent reductions from 300 mL to final volumes of 30, 10, 3, and 1 mL (concentrated) and from 300 mL to 3 and 1 mL (diluted) were evaluated and each sample analyzed using gas chromatography-flame ionization detection (GC-FID). Factors affecting the percentage of analyte recovery include boiling point of analyte, the final sample volume, and starting sample concentration. When concentrated solutions were reduced from 300 mL to 1 mL, PAH recoveries were nearly all higher than 90%, except for naphthalene, acenaphthylene, and acenaphthene. However, when diluted solutions were evaporated to 1 mL, recoveries of all analytes dropped to 64.5% (naphthalene) ∼ 89.2% (benzo[ ghi ]perylene). For evaporation to a final volume of 3 mL, recovery of PAHs in both concentrated and diluted solutions was higher than 90%. This implies that no significant losses of semivolatile analytes were found during evaporation of methylene chloride by rotary evaporation, regardless of boiling point or concentration level, until or unless the final volume was below 3 mL. Results of comparison of rotary evaporation and nitrogen blowdown showed that both concentration techniques provide qualitative recovery but rotary evaporation was more time effective.

A Study on Losses of PAHs During Sample Concentration for Chromatographic Analysis: Evaporation with a Stream of Nitrogen

Losses of polynuclear aromatic hydrocarbons (PAHs) in methylene chloride during evaporation with a stream of nitrogen was systematically studied. The starting sample concentration levels were 0.167 μg/mL and 0.00333 μg/mL for each PAH. These two sets of test solutions were both evaporated from 300 mL to final volumes of 50, 30, 5, 3, and 1 mL, with a constant stream of nitrogen and in a water bath kept at 40°C. Each sample was analyzed by GC-FID. Factors affecting the percentage of analyte recovery include boiling points of analytes, the final sample volume and the starting sample concentration. When the diluted solutions were reduced from 300 mL to 1 mL, the recoveries for PAHs were all higher than 90%. However, when the concentrated solutions were evaporated to 1 mL, recoveries of all analytes dropped below 85%, and naphthalene, the most volatile PAH, dropped to 77.5%. if evaporation was halted to a final volume of 3∼5 mL, the recovery for PAHs in both concentrated and diluted solutions were still almost all higher than 90%. This implies that during evaporation of methylene chloride with a nitrogen stream, no significant losses of semivolatile analytes, regardless of their boiling points or concentration levels, were found until or unless the final volume reaches below 3∼5 mL. Apparently, the solute losses are mainly due to coevaporation instead of vapor partition.

Leukocyte recovery from umbilical cord blood by poligeline.

Umbilical cord blood (UCB) collected at delivery is a source of transplantable stem/progenitor cells; it represents an alternative to bone marrow to restore hematopoiesis in patients affected by malignant and non-malignant disease. Therefore, large-scale UCB banks would be a natural complement to bone marrow donor registries. Storage of unmanipulated whole UCB units requires a great number of liquid nitrogen containers. Separation of leukocytes allows UCB storage in smaller space, thus lowering banking costs; unfortunately, UCB processing may cause significant losses of stem cells. We report about the use of poligeline to remove erythrocytes from UCB units. After erythrocyte sedimentation at 1xg (30' or 40') or 50xg, leukocyte-rich supernatant was collected and centrifuged to recover the leukocyte pool in view of stem cell transplantation. Erythrocyte depletion was always satisfactory, ranging from 82.6% to 88.9%, but 1xg sedimentation for 40' enabled us to achieve the best CD34+ cell recovery (mean value 80.5%). The proposed UCB-processing method allowed us to lower the final sample volume down to 1/10 of the initial one, in this way making UCB banking feasible. Erythrocyte depletion took place directly in the collection bag, thus reducing microbial contamination risk.

2-Phosphoglycolate and glycolate-electrophore detection, including detection of 87 zeptomoles of the latter by gas chromatography-electron-capture mass spectrometry

As a first stage towards a goal of studying some aspects of oxidative damage to DNA and its subsequent repair, we set up three techniques for the detection of 2-phosphoglycolate (PG). This compound is released as a metabolite from the DNA in certain cases of this process. We explored three techniques because we wanted to learn which one(s) would be most sensitive, given the anticipated availability of small biological samples for analysis. By employing indirect detection with fluorescein as the fluorophore in capillary electrophoresis, we detected 5 · 10 −6 M PG (corresponding to 5 pmol/μl, projecting that a final sample volume of 1 μl could be handled). The specificity of this technique can be enhanced by converting the PG to glycolate enzymatically. Flow injection analysis (FIA; 1.0-μl injection volume) negative-ion electrospray mass spectrometry was similarly sensitive (1.1 · 10 −6 M). Based on our prior experience, substituting capillary HPLC for the FIA in this technique is anticipated to lower the detection limit by 20- to 150-fold. Gas chromatography-electron-capture mass spectrometry (1.0-μl injection volume) was able to detect, as a standard, 87 zmol of O 2-pivalyl-3′,5′-bis(trifluoromethyl)benzylglycolate, a product that can be obtained from PG via hydrolysis followed by derivatization. We plan to continue working with all three techniques since each is very sensitive, and has certain advantages.

Analytical characteristics of sample evaporation with the micro-Kuderna-Danish concentrator

The analytical behaviour of dichloromethane, pentane, and hexane solutions was studied through their evaporation in a micro-Kuderna-Danish concentrator. Initial sample concentration, final sample volume, matrix composition, system geometry and temperature gradients influence the process greatly. In general, solute loss increases exponentially when the final volume decreases. During the concentration process with very dilute solutions, the loss of solutes can be higher than 50% if the final volume reached is lower than 200 μl. This means a decrease in the quantification of the process, even though it is seemingly kept under control (low R.S.D.). The solute losses are not just due to the decrease in the number of plates during the reflux disappearance, but also to the probability that droplets of the evaporating sample are projected against clean and dry walls of low retention capacity. This hypothesis may explain the observed effects when concentrating more concentrated samples, or samples with a high content of some solutes. A more advantageous design for the micro-Kuderna-Danish receptor flask is also proposed. The replacement of the cylindrical flask by a flask with conical bottom permits a decrease in the volume of losses and an improvement in the quantification of the process.

Low-Temperature Decomposition of Botanical and Biological Samples for Multielement Analysis by High-Frequency Induced Oxygen–Argon–Fluorine Plasma

Abstract The cool plasma asher (CPA) consists of a high-frequency generator and a quartz sample vessel equipped with a cooling finger that prevents loss of volatile elements. After sample decomposition within an O2–Ar–F plasma, the ashing residues and the elements condensed on the surface of the vessel or cooling finger are dissolved by refluxing in 1–5 mL of double-distilled acid. The sample solutions are analyzed for elemental content by inductively coupled plasma-atomic emission spectrometry (ICP–AES). The recovery values for 42 elements (Ag, Al, As, B, Ba, Be, Bi, Ca, Cd, Co, Cr, Cu, Eu, Fe, Hg, K, Li, Mg, Mn, Mo, Na, Ni, P, Pb, Pd, Pt, Rb, S, Sb, Se, Sn, Sr, Te, Ti, V, Y, Yb, Zn, Zr, La, Au, and Sc) are documented after cool plasma ashing of elemental spectrometric standards. In addition, NIST Standard Reference Materials consisting of botanical and biological samples are ashed by CPA, and results are reported for 23 elements (Al, As, Ba, Be, Ca, Cd, Co, Cr, Cu, Fe, K, Li, Mg, Mn, Na, Ni, P, Pb, S, Se, Sr, V, and Zn) analyzed by ICP-AES. This method achieves good recoveries for many elements while allowing decomposition of difficult sample matrixes without acid, at a temperature slightly above 100°C. We investigated several ashing facilitators to improve ashing efficiency. This paper describes improved ashing conditions due to sample agitation, gas mixtures, Teflon balls, and a Teflon vessel. The time required to ash 1.0 g of botanical sample in the CPA was reduced from 80 h with no ashing aids to 3 h with maximum ashing aids. The optimum plasma ashing conditions for 1.0 g of sample was 6 h at a high-frequency power of 30 W with a 1 h acid reflux to dissolve sample ash. Because reflux acid in the final sample volume was minimal, trace elemerits were concentrated and blank contamination was extremely low.

Method for the isolation and liquid chromatographic determination of eight sulfonamides in milk

A method for the isolation and liquid chromatographic determination of eight sulfonamides in milk is presented. Fortified or blank milk samples (0.5 ml) were blended with octadecylsilyl (C 18T) derivatized silica (2 g). A column made from the sample C 18T matrix was first washed with hexane (8 ml) following which the sulfonamides were eluted with methylene chloride (8 ml). The eluate contained sulfonamide analytes which were free from interferences when analyzed by high-performance liquid chromatography (HPLC) utilizing UV detection (270 nm, photodiode array). Standard curve correlation coefficients (range, 0.998 +− 0.002 to 0.999 +− 0.001), average perentage recoveries (73.1 +− 7.4 to 93.7 +− 2.7%), and the inter- (3.9–9.6%) and intra-assay (2.2–6.7%) variabilities, were determined for the concentration range examined (62.5–2000 ng/ml) and resulted in a minimal detectable limit of 1.25 ng on column (62.5 ng/ml, 20 μl injection from a final sample volume of 0.5 ml). Savings in terms of time and solvent make this procedure attractive when compared to classical isolation techniques for sulfonamides.