40-ml Samples Research Articles

A new technique for low-volume continuous sampling of spent dialysate: a validation study.

The measure of hemodialysis (HD) adequacy recommended nowadays by most guidelines, Kt/V-urea, presents significant drawbacks. Direct dialysis quantification (DDQ) through total dialysate collection (TDC), considered the gold standard measure of HD adequacy, is cumbersome, which precludes its widespread use in clinical practice. The present study aims to validate a low-volume continuous sampling of spent dialysate (CSSD). Cross-sectional study carried out at a university hospital. Throughout 4-h hemodialysis sessions, urea removal was measured by three DDQ methods: TDC, CSSD, and fractional sampling of dialysate (FSD). The primary outcome was the comparison between the total mass of urea removed measured by TDC and the dialysate sampling techniques. The comparison between urea distribution volume (UDV) estimated by anthropometric method and through DDQ was a secondary outcome. The analysis was done through linear regression and Bland-Altman concordance method. Twenty HD sessions were studied. The mean amount of urea collected in TDC and calculated from the 40-mL sample of CSSD were 33.70 ± 11.70g and 33.90 ± 11.70g, respectively [r 0.96, p < 0.0001; bias - 0.2 (95% CI - 1.8 to 1.4); limits of agreement - 6.8 to 6.4]. The anthropometric measure, when compared with DDQ method, underestimated UDV in patients with smaller body size. This new simple, inexpensive, and small volume CSSD technique can provide accurate information about the total amount of solutes removed by hemodialysis.

Micro-organic Ion-associate Phase Extraction/micro-volume Back-extraction for the Preconcentration and GF-AAS Determination of Cadmium, Nickel and Lead in Environmental Water.

Micro-organic ion-associate phase (IAP) extraction was combined with a micro-volume back-extraction (MVBE) to reduce coexisting components and viscosity in the concentrates. Heavy metals were converted into a complex with 2-(5-bromo-2-pyridylazo)-5-(N-propyl-N-sulfopropylamino)phenol in a 40-mL sample solution, and were extracted into ion associates. After centrifugation and discarding the aqueous phase, trace metals were stripped from IAP into a nitric acid solution, followed by GF-AAS determination. Only one vessel was required for 400-fold enrichment. The detection limits (3σb) for Cd, Ni, and Pb were 0.6, 3.7, and 0.8 ng/L, respectively. This method was applied in recovery tests in seawater.

Adsorption and determination of polycyclic aromatic hydrocarbons in water through the aggregation of graphene oxide

Abstract In this study, a simple method was developed for the aggregation of graphene oxide (GO) with the addition of NaCl to concentrate and separate polycyclic aromatic hydrocarbons (PAHs) from water samples, and this method was used as a environmentally friendly method for the determination of PAHs. We demonstrate the uniform dispersion of GO sheets in aqueous samples for the fast high-efficiency adsorption of PAHs. Aggregation occurred immediately upon elimination of electrostatic repulsion by adding NaCl to neutralize the excessive negative charges on the surfaces of the GO sheets. The aggregates of GO and PAHs were separated and treated with hexane to form a slurry. The slurry was filtered and subjected to gas chromatography–mass spectroscopy (GC-MS) analysis. Based on a 40-mL sample volume, limits of detection of 10–30 ng L-1 were obtained for 16 PAHs, with correlation coefficients (R2) exceeding 0.99. The method yielded good recovery, ranging from 80 to 111% and 80 to 107% for real spiked water samples at 100 and 500 ng L-1, respectively. Compared to traditional solid-phase extraction and liquid–liquid extraction methods, this method is free of organic reagents in the pretreatment procedure and uses only 1 mL hexane for sample introduction.

Tannery Waste Water Treatment through Aggregation of Bio-sorption and Chemical Coagulation Aided by Indigenous Coagulant

Tannery in Bangladesh seems a source of pollution load and waste water to all because there are 270 registered tanneries where approximately 220 MT raw hides and skins are taking for the production of leather in Bangladesh. The leather industry has crossed the record $1-billion mark in exports in 2013-2014. According to the Department of Environment, the tanneries discharge 22,000 cubic meters of untreated liquid toxic waste daily. These pollution load and waste water should need treatment to make environmentally sustainable and living. From this point of view, we worked on tannery waste water processing. The paper highlights the initiation of Algal treatment with chemical coagulation process aided by natural coagulant for waste water processing in Bangladesh. The methodology of this process starts with mixing of waste water from different section of beam house operations at a definite ratio. The mixer takes nearly six hours to settle down. After sedimentation, the turbidity decreases at a reasonable amount i.e. 1428 NTU whereas before sedimentation it was 9050 NTU (2100P Turbid Meter of HACH). Later the supernatant was collected for algal treatment. After algal treatment the turbidity reduced to 530 NTU from 1428 NTU and the DO level increased up to 4.48 mg/L at 33.6 °C (HQ 40d of HACH) where DO level was 0.24 mg/L at 33.6°C in raw mixer. In addition, the amount of alum as chemical coagulant was reduced in tannery waste water treatment by using indigenous snail shell powder as coagulant aid in conjunction with alum. In case of untreated sample after sedimentation required alum dozing was 6 mL/ 40 mL sample. After algal treatment, required alum dozing reduced to 4 mL/ 40 mL sample. By adding 3 mL/ 40mL liquid natural coagulant as coagulant aid, alum dozing was further minimized to 1 mL/ 40mL sample. The odour was more tolerable than raw mixer after algal treatment but after adding alum aided by natural coagulant, the odour was more acceptable than before. The diversified technique can hopefully reduce a reliable chemical cost in treatment process, considerable amount of pollution load and increase DO level and thus make effluent environment friendly to discharge. Finally, the DO level increases up to 6.56 mg/L at 33.7 0C and turbidity reduces to 183 NTU, pH reduces to 7.6, odour turns to be tolerable limit.

Directly-thiolated graphene based organic solvent-free cloud point extraction-like method for enrichment and speciation of mercury by HPLC-ICP-MS

Directly-thiolated graphene (G-SH) was prepared by substitution of the epoxy and hydroxyl groups with mercapto on the bulk and edge of the graphene oxide. Cloud point extraction-like method (CPEL) was established for enrichment of divalent mercury (IHg) and monomethylmercury (MMHg) in the water samples, based on the prepared G-SH, with good hydrophilicity, strong affinity towards mercury species and huge surface area. The large amount of active adsorption sites, thiol groups, on the bulk and edge of the surface of the G-SH play a key role in extraction of mercury species. Under the optimal conditions, the enrichment factors were 78 and 77 based on only 40mL samples, the detection limits (3δ) by high-performance liquid chromatography-inductively coupled plasma mass spectrometry (HPLC-ICP-MS) were 3.8 and 1.3ngL−1 for IHg and MMHg with good recoveries, respectively. The proposed CPEL-HPLC-ICP-MS method was successfully applied for speciation of mercury in surface water, underground water, domestic sewage and even sea water; moreover, the results suggested that it is a simple, sensitive and environment-friendly technique for speciation of mercury at trace levels.

Microwave-assisted headspace solid-phase microextraction for the rapid determination of organophosphate esters in aqueous samples by gas chromatography-mass spectrometry

The rapid and solvent-free determination of organophosphate esters (OPEs) in aqueous samples via one-step microwave-assisted headspace solid-phase microextraction (MA-HS-SPME) followed by gas chromatography–mass spectrometry (GC–MS) analysis is described. Tri-n-butyl phosphate (TnBP) and tris-(2-ethylhexyl) phosphate (TEHP) were selected as model compounds for the method of development and validation. The effects of various extraction parameters for the quantitative extraction of these analytes by MA-HS-SPME were systematically investigated and optimized. The analytes, in a 20mL water sample (in a 40mL sample bottle containing 2g of NaCl, pH 3.0), were efficiently extracted by a polydimethylsiloxane-divinylbenzene (PDMS-DVB) fiber placed in the headspace when the system was microwave irradiated at 140W for 5min. The limits of quantification (LOQs) for TnBP and TEHP were 0.5 and 4ng/L, respectively. Using the standard addition method, MA-HS-SPME coupled with GC–MS was utilized to determine selected OPEs in surface water and wastewater treatment plants (WWTP) influent/effluent samples. Preliminary results show that TnBP was commonly detected OPEs in these aqueous samples, the correlation coefficients (r2) of the standard addition curves were greater than 0.9822, indicating that the developed method appears to be a good alternative technique for analyzing OPEs in aqueous samples.

Formation of a Liquid Organic Ion Associate in Aqueous Solution and Its Application to the GF-AAS Determination of Trace Cadmium in Environmental Water as a Complex with 2-(5-Bromo-2-pyridylazo)-5-(N-propyl-N-sulfopropylamino)phenol

The formation of a liquid organic ion associate in an aqueous sample was applied to the concentration and determination of cadmium in environmental water samples. Cadmium was converted into a complex with 2-(5-bromo-2-pyridylazo)-5-(N-propyl-N-sulfopropylamino)phenol (5-Br-PAPS) in a 40-mL sample solution, and was extracted into a liquid ion associate of phenolsulfonate and benzethonium during phase formation. More than 400-fold enrichment was easily attained by this technique, because the volume of the liquid organic phase formed was very small, ca. 2 microL. After dilution of the organic phase with a small volume of 2-methoxyethanol, the cadmium in the solution was determined by GF-AAS. The detection limit was 0.09 ng/L (3sigma(b)). This method was applied to the determination of cadmium in river water and seawater.

Thiourea catalysis of MeHg ligand exchange between natural dissolved organic matter and a thiol-functionalized resin: a novel method of matrix removal and MeHg preconcentration for ultratrace Hg speciation analysis in freshwaters

Ultratrace analysis of dissolved MeHg in freshwaters requires both dissociation of MeHg from strong ligands in the sample matrix and preconcentration for detection. Existing solid phase extraction methods generally do not efficiently adsorb MeHg from samples containing high concentrations of natural dissolved organic matter. We demonstrate here that the addition of 10-60 mM thiourea (TU) quantitatively releases MeHg from the dissolved matrix of freshwater samples by forming a more labile complex (MeHgTU+) that quantitatively exchanges MeHg with thiol-functionalized resins at pH approximately 3.5 during column loading. The contents of these columns were efficiently eluted with acidified TU and MeHg was analyzed by Hg-TU complex ion chromatography with cold-vapor atomic fluorescence spectrometry detection. Routinely more than 90% of MeHg was recovered with good precision (average relative standard deviation of 6%) from natural waters-obtained from pools and saturated sediments of wetlands and from rivers-containing up to 68.7 mg C L-1 dissolved organic matter. With the preconcentration step, the method detection limit of 0.29 pg absolute or 0.007 ng L-1 in 40-mL samples is equivalent to that of the current state-of-the- art as practiced by skilled analysts. MeHg in 20-50-mL samples was completely trapped. On the basis of our knowledge of the chemistry of the process, breakthrough volume should depend on the concentrations of TU and H+. At a TU concentration of 12 mM breakthrough occurred between 50 and 100 mL, but overall adsorption efficiency was still 85% at 100 mL. Formation of artifactual MeHg is minimal; only about 0.7% of ambient MeHg is artifactual as estimated from samples spiked with 4 microg L-1 HgII.

Improved method for the storage of groundwater samples containing volatile organic analytes

The sorption of volatile organic analytes from water samples by the Teflon septum surface used with standard glass 40-ml sample collection vials was investigated. Analytes tested included alkanes, isoalkanes, olefins, cycloalkanes, a cycloalkene, monoaromatics, a polynuclear aromatic, and two chloroethenes. Both laboratory prepared test mix solutions and petroleum contaminated groundwater from three field sites were tested. A rapid loss of n-alkane and isoalkane concentrations (>10%) was observed within 24 h when stored at room temperature. Aliphatic losses were also observed (>10%) over a 21-day holding period when samples were held at 4 degrees C. Loss of the less sorptive analytes was demonstrated by exposing analyte solutions to greater Teflon surface areas. The demonstrated sorption of aliphatics from water samples by Teflon-lined septa indicates that the accuracy of volatile petroleum hydrocarbon determinations may be reduced by the traditional storage method. An alternative storage protocol is reported combining a lead foil septum surface and 1% (w/w) tribasic sodium phosphate dodecahydrate (Na3PO4. 12H2O) preservative. This method prevented loss of the test analytes, including alkanes and isoalkanes for at least 21 days at room temperature.

Radiolabelled mixed leukocytes and pure granulocytes with stabilized 99Tcm-exametazime.

Although the methylene blue stabilizer extends the shelf life of 99Tcm-exametazime to 4-6 h after reconstitution, the dark blue appearance of the mixture of stabilized 99Tcm-exametazime and blood components makes it impossible to separate out the leukocyte button. The aim of this study was to assess the feasibility of using stabilized 99Tcm-exametazime to radiolabel mixed leukocytes separated by Volex sedimentation with hypotonic lysis (VL) and pure granulocytes isolated by a single-density Ficoll-Hypaque gradient with hypotonic lysis (FL). Isolated cells from 40-ml and 80-ml donor blood samples were mixed with 0.5 ml stabilized 99Tcm-exametazime (approximately 925 MBq 99Tcm and 62.5 micrograms exametazime) and incubated at room temperature for 15 min. After incubation, two dilution steps with 3 ml and 9 ml of 12.6% ACD/NS (anticoagulant citrate dextrose, solution A, USP, mixed with 0.9% NaCl, v/v) were conducted to dilute the dark blue mixture and to remove any unbound 99Tcm activity. With the addition of 9 ml of 12.6% ACD/NS solution to the 1-ml bottom portion from the first dilution, the supernatant of the centrifuged preparation was clear enough to be withdrawn. The overall labelling efficiency (LE) of labelled leukocytes and granulocytes was 87.1 +/- 4.9% and 87.7 +/- 6.2%, respectively (n = 12 each). Overall, radiolabelled cells (n = 12) from the 80-ml blood samples (LE = 90.3 +/- 2.8%) had an approximately 6% higher labelling efficiency than from the 40-ml blood samples (LE = 84.5 +/- 6.0%) and also had a slightly better in vitro stability compared to the 40-ml samples. The in vitro stability studies showed that only approximately 2% (n = 48) 99Tcm activity was eluted each hour from the radiolabelled leukocytes or granulocytes for the 40-ml or 80-ml blood samples during the 6-h evaluation period. Cell viability of all labelled leukocyte samples was confirmed by the trypan blue staining technique. In conclusion, mixed leukocytes separated by the VL method and pure granulocytes isolated by the FL method can be effectively labelled with stabilized 99Tcm-exametazime with the use of the 'double dilution' technique.

Gas chromatographic—mass spectrometric determination of lower aliphatic tertiary amines in environmental samples

A method is described for determining lower aliphatic tertiary amines in environmental samples such as river water and bottom sediments. The method consists of distillation of aliphatic tertiary amines and determination by headspace gas chromatography—mass spectrometry. The detection limits for final 40-ml samples were 50 ng for trimethylamine, 10 ng for triethylamine, 5 ng for triallylamine, 10 ng for tripropylamine and 5 ng for tributylamine. The recoveries were over 70% and the relative standard deviations of the recoveries were below 12% ( n = 5). The method is easy to operate, shows excellent sensitivity and selectivity and is applicable to environmental samples.

Spectrophotometric determination of iodide at the 10–6mol l–1level by solvent extraction with methylene blue

Iodide is separated from other chemical species by its oxidation and subsequent extraction into carbon tetrachloride. The proposed method is based on the extraction of the back-extracted iodide into 1,2-dichloroethane as an ion pair with methylene blue. When a 40-ml sample solution is used, the apparent molar absorptivity for iodide is 3.15 × 105 l mol–1 cm–1 and the Sandell sensitivity for a 0.001 absorbance is 4.3 × 10–4µg cm–2 of l– at 657 nm. A linear calibration graph is obtained over the range 7.5 × 10–8–3 × 10–6M iodide and the relative standard deviation is 0.87% at the 1.5 × 10–6M iodide level. The proposed method was successfully applied to the determination of various amounts of iodide in natural water samples.

Hygroscopicity of synthetic oils

In our studies of oil hygroscoplcity, we stored 40-ml samples of predried oils in a 100% relative humidity atmosphere for 72 h at 20 • 3~ after which the quantity of absorbed moisture was determined. These particular conditions ensure that the oil will be saturated with water. The oils examined were the mineral oils MS-8 and MS-8p; the isoparaffinic oil IPM-10; the dioctyl ester of sebacic acid (DOS); two esters of polyhydric alcohols, one the pentaerythritol ester (PEE) and the other the diethylene glycol ester (DEGE) of a Cs--C9 cut of synthetic fatty acids; the synthetic oils VNII NP-50-1-4f, VNII NP-7, 36/1 KU-A, B-3V, and non-Sovlet oils conforming to the U.S, specifications MIL-L-78080 and MIL-L-23699B.