Fractionation of lead in soils affected by smelter activities using a continuous-flow sequential extraction system

A continuous-flow sequential extraction system was used to study the distribution of Pb, and its association with other elements (Fe, Al and Ca), in soils around a Pb smelter. Soil samples were analysed by a four-step continuous-flow sequential extraction procedure employing a modified Tessier/BCR scheme. Recoveries of Pb using the flow system (88–111%) were higher than those obtained using a conventional batch extraction system. There were also some differences in Pb distribution between fractions as determined using the two extraction systems. The most abundant fraction of Pb was extracted during the dissolution of soil oxides (Fe/Al). Extractograms (plots of concentration of elements vs. extractant volume/time) indicated that anthropogenic Pb was predominantly adsorbed onto Fe oxide surfaces in contaminated soils. In soil profiles, the highest amounts of Pb were found in the topsoil surface layers (0–5?cm) of the contaminated soils with only limited movement into subsurface layers.     

Study of phosphorus distribution in coastal surface sediment by sequential extraction procedure (NE Mediterranean Sea, Antalya-Turkey)

The paper presents the results of the distribution of phosphorus (P) bioavailability (total P, organic and inorganic P) in marine surface sediments collected from four coasts that are under different anthropogenic pressures of NE Mediterranean Sea (Alanya, Serik, Kemer, Finike — Antalya, Turkey) in May, 2009. Speciation of inorganic phosphorus (IP) was carried out using a method on sequential extractions, with each releasing four forms of IP — loosely bound P, phosphorus bound to aluminum (P-Al), phosphorus bound to iron (P-Fe), and phosphorus bound to calcium (P-Ca) and determined by the inductively coupled plasma-optical emission spectrometer (ICP-OES). The total P contents ranged from 152.18 to 275.12 mg/kg. It was found that more than 96% of the total P is IP. Among the four forms of IP, IP distribution ranges were 1.20-3.59% for loosely bound P, 2.38-4.74% for P-Fe, 4.43-8.55% for P-Al, and 84.36-91.99% for P-Ca. The region of Alanya was characterized by the highest total P concentration in the surface sediment than Serik, Kemer, Finike sediments. For all the marine surface sediment samples, the rank order of inorganic P-fractions was Ca-P > Al-P > Fe-P > loosely bound P.     

Continuous-flow extraction system for elemental association study: a case of synthetic metal-doped iron hydroxide

A continuous-flow extraction system originally developed for sequential extraction was applied to study elemental association of a synthetic metal-doped amorphous iron hydroxide phase. The homogeneity and metal association of the precipitates were evaluated by gradual leaching using the system. Leachate was collected in fractions for determination of elemental concentrations. The result obtained as extractograms indicated that the doped metals were adsorbed more on the outermost surface rather than homogeneously distributed in the precipitates. The continuous-flow extraction method was also used for effective removal of surface adsorbed metals to obtain a homogeneous metal-doped synthetic iron hydroxide by a sequential extraction using acetic acid and small volume of hydroxylamine hydrochloride solution. The system not only ensures complete washing, but the extent of metal immobilization in the synthetic iron hydroxide could be determined with high accuracy from the extractograms. The initial metal/iron mole ratio (M/Fe) in solution affected the M/Fe mole ratio in homogeneous doped iron hydroxide phase. The M/Fe mole ratio of metal incorporation was approximately 0.01–0.02 and 0.03–0.06, for initial solution M/Fe mole ratio of 0.025 and 0.100, respectively.     

Iron fractionation for corrosion products from natural gas pipelines by continuous-flow sequential extraction

The forms and quantities of iron species in corrosion product samples from natural gas pipelines were examined, using a continuous-flow sequential extraction system. Sequential extraction consists of four steps that dissolve water soluble iron (FeSO₄), acid soluble iron (FeCO₃), reducible iron (Fe-(oxyhydr)oxides) and oxidisable iron (FeS₂) fractions, respectively. Selectivity of extracting reagents for particular iron species was evaluated by determination of co-extracted anions, using ion chromatography, and evolved CO₂, using indirect flame atomic absorption spectrometer (FAAS). Iron was found predominantly in the reducible fraction (61–99%), indicating that Fe-(oxyhydr)oxides are the major constituents of the corrosion products.      

Fractionation of heavy metals in sediment by using microwave assisted sequential extraction procedure and determination by inductively coupled plasma mass spectrometry

In this work, a fast microwave assisted extraction procedure was developed and optimized for the heavy metals (Cu, Ni, Cr, Pb and Cd) partitioning in the three-stage sequential extraction procedure proposed by the European Standards, Measurements and Testing (SM&;T) Program, formerly the Community Bureau of Reference (BCR). The microwave oven procedure was optimized to obtain extraction efficiencies similar to the conventional BCR procedure, in less time, while using smaller volumes of reagents. In the optimization process, three variables (extraction time, ramping time and microwave power) were considered as factors and as a response the concentration of different metal ions in each individual BCR fraction. Interactions between analytical factors and their optimized levels were investigated using a central composite design. Extractable metals obtained by both comparable methodologies were measured by inductively coupled plasma mass spectrometry. With the use of optimal microwave conditions, steps 1–3 of the sequential extraction (including the hydrogen peroxide digestion in step 3) could be completed between 21 and 22 min. Detection limits were between 1 and 18 ng l^{− 1}. The accuracy of the proposed method was checked with a certified reference material (CRM) of Lake Sediment BCR 701. Values obtained were in accordance with those reported for the certified material with only a few exceptions. Different origin sediments (river and marine) were analyzed by both BCR and MW procedures, and the results obtained were comparable according to the t-paired-test for a 95% confidence level.     

Should acid ammonium oxalate replace hydroxylammonium chloride in step 2 of the revised BCR sequential extraction protocol for soil and sediment?

The revised, four-step BCR sequential extraction for soil or sediment has been compared with an alternative procedure in which 0.2 mol l⁻¹ ammonium oxalate (pH 3) replaced 0.5 mol l⁻¹ hydroxylammonium chloride (pH 1.5) in step 2, the reducible step. A variety of substrates were studied: BCR CRM601, a sewage sludge amended soil, two industrial soils, and a steel manufacturing by-product (basic oxygen furnace filter cake). Greater amounts of iron were recovered in step 2 when acid ammonium oxalate was used, for all substrates. Similar trends were observed for copper. Manganese and zinc were not strongly affected by the procedural modification, except for zinc in the two industrial soils, where oxalate extraction proved more efficient than use of hydroxylammonium chloride. A large proportion of the calcium and lead isolated in step 2 of the BCR procedure was not released until step 3 when the alternative procedure with oxalate in step 2 was used. This is probably due to rapid precipitation of analyte oxalates from solution. Thus, whilst oxalate offers superior dissolution of iron-containing matrix components, it should not be used if calcium or lead concentrations are to be measured. Selection of the most appropriated sequential extraction protocol for use in a particular study must always be carried out on the basis of “fitness for purpose” criteria. However, the revised BCR protocol, involving use of 0.5 mol l⁻¹ NH₂OH·HCl in the reducible step, appears to be more generally applicable than procedures involving acid ammonium oxalate.     

Ultrasound and microwave-assisted extraction of metals from sediment: a comparison with the BCR procedure

In this paper we investigate alternatives to mechanical stirring for the extraction of the mobile fraction of metals from sediment, and analyze whether these techniques can reduce extraction time and improve reproducibility. We compare the quantities of metal extracted from BCR601 and BCR701 certified sediments using ultrasound bath, microwave-assisted extraction and the first step in the certified BCR sequential extraction procedure. Some environmentally important not-certified metals such as As, Mn, Co, Fe and Al have been included in this study. In the case of microwave-assisted extraction, we compare tests in which samples are exposed to constant, low power irradiation with tests using pulsed high power.

In the tests using the ultrasound bath, less metal was extracted than with the other extractive techniques and standard deviations were comparable to those obtained with the BCR procedure; in assays using microwaves at constant power, extraction efficiencies were different for different metals and for different reference materials and, in some cases, standard deviations were higher than those for the reference method. In contrast, tests with microwaves and constant temperature produced encouraging results: R.S.D.s lay in the 2–4% range, both for certified and not-certified metals; these values are very low compared to those for the reference method. Extraction efficiencies for certified metals were close to 100% for Cd, Zn, Cu and Ni and around 80% for Pb and Cr.     

Integration of continuous-flow sampling with microchip electrophoresis using poly(dimethylsiloxane)-based valves in a reversibly sealed device

Here we describe a reversibly sealed microchip device that incorporates poly(dimethylsiloxane) (PDMS)-based valves for the rapid injection of analytes from a continuously flowing stream into a channel network for analysis with microchip electrophoresis. The microchip was reversibly sealed to a PDMS-coated glass substrate and microbore tubing was used for the introduction of gas and fluids to the microchip device. Two pneumatic valves were incorporated into the design and actuated on the order of hundreds of milliseconds, allowing analyte from a continuously flowing sampling stream to be injected into an electrophoresis separation channel. The device was characterized in terms of the valve actuation time and pushback voltage. It was also found that the addition of sodium dodecyl sulfate (SDS) to the buffer system greatly increased the reproducibility of the injection scheme and enabled the analysis of amino acids derivatized with naphthalene-2,3-dicarboxaldehyde/cyanide. Results from continuous injections of a 0.39 nL fluorescein plug into the optimized system showed that the injection process was reproducible (RSD of 0.7%, n = 10). Studies also showed that the device was capable of monitoring off-chip changes in concentration with a device lag time of 90 s. Finally, the ability of the device to rapidly monitor on-chip concentration changes was demonstrated by continually sampling from an analyte plug that was derivatized upstream from the electrophoresis/continuous flow interface. A reversibly sealed device of this type will be useful for the continuous monitoring and analysis of processes that occur either off-chip (such as microdialysis sampling) or on-chip from other integrated functions.     

Investigation of distribution of soil antimony using sequential extraction and antimony complexed to soil-derived humic acids molar mass fractions extracted from various depths in a shooting range soil

Trace metal contamination from bullet fragments in shooting ranges is a major environmental concern. In particular, trace metals such as lead, antimony, and copper are toxic and have the potential to enter groundwater supplies and to be absorbed by plants. Soil humic acids can play a critical role in mobilizing some of these released metals through complexation. The purpose of this study is to investigate the antimony complexed to soil-derived humic molar mass fractions extracted from various depths in a shooting range soil and to examine the distribution of antimony in various fractions of shooting range soils using sequential chemical extraction approach. The surface soil and soil core samples from a local shooting range were collected. Soil-derived humic acids were extracted from different depths of the top soil layer and characterized by various spectroscopic methods. Results of sequential chemical extraction demonstrated that Sb was found in shooting range in the upper 30 cm depth of the soil core. Highly elevated Sb is present in the exchangeable and ammonium acetate extracted fractions. Antimony is also present in the residual fraction in both surface and core soil samples, but is most likely present in a lithic phase which may not be readily bio-available. Leached antimony complexed to soil humic acid molar mass fractions was determined by size exclusion chromatography coupled to inductively coupled plasma-mass spectrometry (SEC-ICP-MS). The results demonstrate that Sb is ‘tightly’ bound to humic acid mass molar mass fractions and confined in the top 10 cm of soil-derived humic acids.     

Determination of available phosphorus in soils by using a new extraction procedure and a flow injection amperometric system

A new extraction procedure based on an off-line extraction column was proposed for extracting of available phosphorus from soils. The column was fabricated from a plastic syringe fitted at the bottom with a cotton wool and a piece of filter paper to support a soil sample. An aliquot (50 mL) of extracting solution (0.05 M HCl + 0.0125 M H₂SO₄) was used to extract the sample under gravity flow and the eluate was collected in a polyethylene bottle. The extract was then analyzed for phosphorus contents by a simple flow injection amperometric system, employing a set of three-way solenoid valves as an injection valve. The method is based on the electrochemical reduction of 12-molybdophosphate which is produced on-line by the reaction of orthophosphate with acidic molybdate and the electrical current produced was directly proportional to the concentration of phosphate in range of 0.1-10.0 mg L⁻¹ PO₄-P, with a detection limit of 0.02 mg L⁻¹. Relative standard for 11 replicate injections of 5 mg L⁻¹ PO₄-P was 0.5%. A sample through put of 35 h⁻¹ was achieved, with consumption of 14 mg KCl, 10 mg ammonium molybdate and 0.05 mL H₂SO₄ per analysis. The detection system does not suffer from the interferences that are encountered in the photometric method such as colored substances, colloids, metal ions, silicate and refractive index effect (Schlieren effect). The results obtained by the column extraction procedure were well correlated with those obtained by the steady-state extraction procedure, but showed slightly higher extraction efficiency.     

Application of a wavelength-dispersive particle-induced X-ray emission system to chemical speciation of phosphorus and sulfur in lake sediment samples

The chemical speciation of phosphorus and sulfur in lake sediment was performed by analyzing Kα X-ray spectra recorded with a high-resolution wavelength-dispersive particle-induced X-ray emission (WD-PIXE) system. The concentrations of phosphorus and sulfur in the sediment were 2500 and 7000 ppm, respectively. To measure both minor elements in a reasonable measurement time, a 2-MeV proton beam with a high current density (6 nA/mm²) was used for the chemical speciation. The possible chemical state change caused by the proton irradiation was studied in order to determine the maximal irradiation time without significant change. We found that the chemical states of phosphorus and sulfur were stable under a beam current density of 6 nA/mm² and a measurement time of 60 min (phosphorus) and 90 min (sulfur). The chemical states of phosphorus and sulfur were determined to be P⁵⁺ and a mixture of S²⁻ and S⁶⁺, respectively.     

Method development based on all injection analysis for the determination of phosphorus in soil and sediment extracts

In this work, we have modified the technique of all injection analysis (AIA) by changing the position of the detector. The detection is then located as a part of the circulatory loop. With this new detector position, we could monitor for many numbers of circulation. The sensitivity was improved by using the cumulative signal data obtained when the number of circulation rounds was increased. The dilution effect using this new detector location was also less than that with the previous system. We employed a four-channel peristaltic pump to aspirate four types of liquids into the system together at one time. The AIA method was then developed for determination of phosphorus in soils and sediment extracts. The method was optimized for the new harmonized scheme of extraction that has been developed by the European Commission.     

Microwave extraction of phthalate esters from marine sediment and soil

Summary As part of an on-going ASEAN⁺⁾-Canada Cooperative Programme on Marine Science, microwave-assisted solvent extraction has been employed for the extraction of six phthalate esters from marine sediment and soil samples. Five of the six esters studied are among the United States Environmental Protection Agency's list of top priority pollutants. The effects of extraction solvent, extraction temperature, duration of extraction and extraction volume on the mean recoveries of the six phthalate esters were quantitatively evaluated by means of an analysis of variance, followed by testing the differences among the level means for each condition with least significant difference method. Microwave-assisted solvent extraction allowed comparable or higher recoveries of the six phthalate esters (70.1–91.0%) in comparison with conventional soxhlet (65.5–89.5%) and sonication (64.6–88.6%). The precision of results by microwave-assisted solvent extraction was improved significantly compared to the conventional techniques. The microwave extraction system has many advantages over the soxhlet and sonication extraction, e.g., no laborious clean-up procedure, lower usage of hazardous organic solvent, and larger sample throughput. The technique has been employed for the analysis of native marine sediment and soil samples in Singapore.     

Rapid, highly efficient extraction and purification of membrane proteins using a microfluidic continuous-flow based aqueous two-phase system

Membrane proteins play essential roles in regulating various fundamental cellular functions. To investigate membrane proteins, extraction and purification are usually prerequisite steps. Here, we demonstrated a microfluidic aqueous PEG/detergent two-phase system for the purification of membrane proteins from crude cell extract, which replaced the conventional discontinuous agitation method with continuous extraction in laminar flows, resulting in significantly increased extraction speed and efficiency. To evaluate this system, different separation and detection methods were used to identify the purified proteins, such as capillary electrophoresis, SDS-PAGE and nano-HPLC-MS/MS. Swiss-Prot database with Mascot search engine was used to search for membrane proteins from random selected bands of SDS-PAGE. Results indicated that efficient purification of membrane proteins can be achieved within 5-7s and approximately 90% of the purified proteins were membrane proteins (the highest extraction efficiency reported up to date), including membrane-associated proteins and integral membrane proteins with multiple transmembrane domains. Compared to conventional approaches, this new method had advantages of greater specific surface area, minimal emulsification, reduced sample consumption and analysis time. We expect the developed method to be potentially useful in membrane protein purifications, facilitating the investigation of membrane proteomics.     

Comparison of metal analysis in sediments using EDXRF and ICP-OES with the HCl and Tessie extraction methods

The work presents an investigation on metal availability in sediments during 13 months using the dispersive-energy X-ray fluorescence (EDXRF) and atomic emission spectrometry with induced argon plasma (ICP-OES) techniques and single extraction (0.1 mol l⁻¹ HCl) and Tessie’s sequential speciation methods. The EDXRF technique could yield essentially the same profile as ICP-OES for the seasonal variation of metals in sediments, but in a more practical way. The sequential extraction procedure (SEP) was more efficient in metal dissolution than single extraction. The Pb, Ni, Al, Cr, and Fe elements were less efficiently extracted with single extraction in relation to sequential extraction. For Co both methodologies were equivalent, but for Cu and Mn the extraction was higher with single extraction. Single extraction does not mobilize Pb, Ni, Al, Cr, and Fe adsorbed on oxides and bound to organic matter. However for Cu and Mn, not only extracted these metals from the four fractions, but it also dissolved part of the fifth fraction (residual). Principal Component Analysis discriminated seasonal variations in the content of several metals, mainly Fe, Co, Ni, and Zn. The mobility of metallic ions in the sediments is conditioned to the seasonal flow of organic and inorganic material coming from the river or by the erosion of adjacent soils.     

Chemical speciation and contamination assessment of Zn and Cd by sequential extraction in surface sediment of Klang River, Malaysia

The concentration and chemical speciation of Cd and Zn as well as total organic carbon (TOC) were studied in surface sediments from 21 stations along Klang River. Sequential extraction technique (SET) was applied to assess the four (exchangeable, acid-reducible, oxidisable-organic and residual) fractions in surface sediment. And also, to obtain an overall classification of cadmium and zinc pollution in this area. This investigation was the first study on the basis of the chemical speciation of Cd and Zn in surface sediments of the Klang River. The total concentrations of metals were ranged (0.60–2.26 µg g^{− 1}) for Cd and (33.26–268.24 µg g^{− 1}) for Zn. The chemical speciation of Cd and Zn in most sampling stations were in the order of residual > acid-reducible > oxidisable-organic > exchangeable, and it showed that the Zn in Klang River surface sediments existed in the nonresistant fractions, whilst Cd existed in the resistant fraction. The degree of surface sediments contamination was determined for individual contamination factors (ICF) and global contamination factor (GCF). The result of ICF and GCF values showed that those stations located vicinity of municipal area had high potential risk to fauna and flora of the Klang River. The relationship between the concentration of cadmium and zinc at the oxidation-organic fraction with TOC in surface sediment was identified. The results showed that TOC had a positive function to complex with Cd and Zn in the surface sediment of Klang River.     

固相萃取-顺序注射分光光度法快速测定微生物菌落中的麦白霉素

在顺序注射系统中引入C18固相萃取柱进行生米卡链霉菌菌落样品的纯化富集,建立了快速测定菌落中麦白霉素的分光光度法。用超声波破碎菌落细胞后,将样品溶液通过固相萃取柱,用少量甲醇洗脱吸附在C18微珠上的麦白霉素,232 nm检测。进样量为2 ml,洗脱液体积为100μL,麦白霉素的富集倍率为14;线性范围为0.1~10μg/mL,检出限为0.02μg/mL,RSD为2.5%(0.5μg/mL,n=7)。菌落样品中麦白霉素的加标回收率为96%~100%。     

Oxidative extraction versus total decomposition of soil in the determination of thallium

An aqua regia extraction and a total decomposition of soil were compared in terms of thallium determination. A sequential extraction of soil, according to the BCR protocol, was also performed for additional information on thallium distribution in soil fractions. Certified reference material—soil GBW 07401 of Chinese origin, containing 1 ± 0.2 ppm of thallium was used in these experiments. Thallium was determined by flow injection-differential pulse-anodic stripping voltammetry (FI-DP-ASV). Only 35% of total thallium was extracted in the aqua regia extraction, while the total decomposition led to satisfactory recovery. The sequential extraction showed that only 5% of thallium in GBW 07401 is dissolvable in the four BCR procedure fractions, and that 95% of the element is entrapped in the residual parent matter. These results show that the aqua regia extraction does not ensure complete thallium extraction from soil. Surprisingly, the total decomposition is significantly less time consuming than the aqua regia extraction.     

Fractionation of Sb and As in soil and sludge samples using different continuous-flow extraction techniques

The fractionation of Sb and As in soil and sludge samples had been comparably studied using two continuous-flow systems: a microcolumn (MC) and a rotating coiled column (RCC). The leachants were applied in correspondence with a five-step sequential extraction scheme addressing water-soluble, non-specifically sorbed, specifically sorbed, and bound to amorphous and crystalline Fe/Al oxide fractions of Sb and As. Inductively coupled plasma atomic emission spectroscopy was applied to determine antimony, arsenic, and major elements in the effluent and in the residual fractions after their digestion. Resemblances and discrepancies of the two methods were evaluated by the fractionation of Sb and As in forest soil, river sludge, and dumped waste (soil) samples. For the forest soil sample, which is very poor in organic matter, RCC and MC extractions yielded similar quantitative values of As and Sb contents in individual leachable fractions. However, for the river sludge sample with a moderate concentration of C _org (3.3 %), the results obtained by both continuous-flow methods are in satisfactory agreement. RCC extraction enabled water-soluble and non-specifically sorbed As fractions to be recovered, whereas after MC leaching, these environmentally relevant forms of As were not detected. For the soil rich in organic matter (C _org = 11.5 %), the discrepancy between the data of RCC and MC fractionations is significant. RCC extraction provides about six times higher recoveries of As and Sb bound to amorphous Fe/Al oxides. More efficient leaching of As and Sb in RCC may be attributed to the migration of organic-rich particles with low density inside the column that might enhance the mixing of the solid and liquid phases.     

Photosensitized addition of isopropanol to furanones in a continuous-flow dual capillary microreactor

A novel continuous-flow photoreactor with parallel capillaries was constructed and successfully tested for the DMBP-sensitized addition of isopropanol to furanones. Complete conversions were achieved after a maximum of 10 min of irradiation with a single 350 nm lamp. The results were compared to analogous batch experiments using a conventional Rayonet chamber reactor equipped with 16 UVA lamps. The capillary tower generally showed higher space-time yields.