Dowex 1X8 Research Articles

Core3 O-Glycan Synthase Suppresses Tumor Formation and Metastasis of Prostate Carcinoma PC3 and LNCaP Cells through Down-regulation of α2β1 Integrin Complex

Although there are numerous reports of carbohydrates enriched in cancer cells, very few studies have addressed the functions of carbohydrates present in normal cells that decrease in cancer cells. It has been reported that core3 O-glycans are synthesized in normal gastrointestinal cells but are down-regulated in cancer cells. To determine the roles of core3 O-glycans, we transfected PC3 and LNCaP prostate cancer cells with beta3-N-acetylglucosaminyltransferase-6 (core3 synthase) required to synthesize core3 O-glycans. Both engineered cell lines exhibited reduced migration and invasion through extracellular matrix components compared with mock-transfected cells. Moreover we found that alpha2beta1 integrin acquired core3 O-glycans in cells expressing core3 synthase with decreased maturation of beta1 integrin, leading to decreased levels of the alpha2beta1 integrin complex, decreased activation of focal adhesion kinase, and reduced lamellipodia formation. Upon inoculation into the prostate of nude mice, PC3 cells expressing core3 O-glycans produced much smaller tumors without metastasis to the surrounding lymph nodes in contrast to robust tumor formation and metastasis seen in mock-transfected PC3 cells. Similarly LNCaP cells expressing core3 O-glycans barely produced subcutaneous tumors in contrast to robust tumor formation by mock-transfected LNCaP cells. These findings indicate that addition of core3 O-glycans to beta1 and alpha2 integrin subunits in prostate cancer cells suppresses tumor formation and tumor metastasis.

Optimization and validation of a methodology to determine total arsenic, As(III) and As(V), in water samples, through graphite furnace atomic absorption spectrometry

The Graphite furnace atomic absorption spectrometry (GF AAS) was the technique chosen by the inorganic contamination laboratory (INCQ/ FIOCRUZ) to be validated and applied in routine analysis for arsenic detection and quantification. The selectivity, linearity, sensibility, detection, and quantification limits besides accuracy and precision parameters were studied and optimized under Stabilized Temperature Platform Furnace (STPF) conditions. The limit of detection obtained was 0.13 µg.L-1 and the limit of quantification was 1.04 µg.L-1, with an average precision, for total arsenic, less than 15% and an accuracy of 96%. To quantify the chemical species As(III) and As(V), an ion-exchange resin (Dowex 1X8, Cl- form) was used and the physical-chemical parameters were optimized resulting in a recuperation of 98% of As(III) and of 90% of As(V). The method was applied to groundwater, mineral water, and hemodialysis purified water samples. All results obtained were lower than the maximum limit values established by the legal Brazilian regulations, in effect, 50, 10, and 5 µg.L-1 para As total, As(III) e As(V), respectively. All results were statistically evaluated.

Determination of stability constants between complexing agents and At(I) and At(III) species present at ultra-trace concentrations

A competition method is proposed to determine the complexation constants between At(I) and At(III) species and complexing agents. The method, tested with an inorganic ligand, thiocyanate ion (SCN −), and an organic macromolecule, thiacalix[4]arenetetrasulfonate (LH 4) is based on solid/liquid separation or liquid/liquid extraction. For the solid/liquid separation, the cationic exchanger Dowex 50X8 was used. The interaction of At(I) and At(III) with the cationic exchanger is specific but could not be described by the expected cation exchange process. Most probably, At(I, III) interacts with a “strong” site (in weak amount) to form a surface complex at the surface of the resin organic skeleton. For the liquid/liquid separation, chloroform, toluene and hexane were used. All solvents extract astatine species with distribution coefficients varying between 0.7 and 120. The extraction process was shown to be independent of aqueous phase characteristics (pH, ionic strength) and was explained by the solvation of astatine species by the organic solvent. The effect of the addition of the thiacalix[4]arenetetrasulfonate on the solid/liquid or liquid/liquid distribution coefficients could be well described by the formation of a 1:1 complex with stability constants of log β 1 = 4.5 ± 0.4 and 3.3 ± 0.3 for At(I) and At(III), respectively. For the thiocyanate ion, the data measured in the presence of the organic solvents could be explained by the formation of both 1:1 and 1:2 At:SCN complexes. In the case of the solid/liquid separation, data analysis was hampered by the probable formation of a ternary complex between At(I, III), SCN − and the functional groups of the resin. As for the calixarene, the interaction strength appeared slightly higher for At(I) (log β 2 = 5.9 ± 0.3 and log β 1 = 3.8 ± 0.2 for 1:2 and 1:1 complexed species, respectively) than for At(III) (log β 2 = 5.3 ± 0.2 and log β 1 = 2.8 ± 0.2 for 1:2 and 1:1 complexed species, respectively).

Estrogen activity of Silkworm (Bombyx mori) Pupa water extract and its fractions

SUMMARY This study was conducted to evaluate the estrogen activity of silkworm (Bombyx mori) pupa extracts and their fractions. Powdered samples of freeze-dried silkworm pupa were extracted at room temperature (RT), 40 oC, 60 oC, 80 oC, and 100 oC in water (D.W), chloroform, ethyl acetate, and methanol for 6h and then filtered (0.45 um). The extracts were then freeze-dried. The estrogenic activity of these extracts was then investigated by competition binding assays using estrogen receptor α (ERα) and ERβ, and by evaluating their effects on the proliferation of the human breast cancer cell line, MCF-7. Among the extracts evaluated, water extracts prepared at RT showed the highest binding affinity to ERα (IC , 1.76 ug/ml) and ERβ (IC , 0.07 ug/ml). In addition, MCF-7 cells that were treated with 62.5 ug/ml of the RT extract showed the greatest increase in proliferation (2-fold; 1291.79%) when compared to control cells (659.82%). Next, the water extract that was prepared at RT (sample 1) was dissolved in D.W. and further fractionated using a Dowex 50W - 8X (H ) column. The flow-through and wash were then pooled together and freeze-dried (sample 2). The bound materials were then eluted with 20 mM NaCl, after which they were applied to a Dowex 1X2 - 200 (Cl ) column and washed with D.W. to remove the sodium ions. The eluants were then freeze-dried (sample 3). Of these fractions, sample 2 showed the highest binding affinity to ERα (IC , 1.44 ug/ml) and ERβ (IC , 1.18 ug/ml). In addition, MCF-7 cells that were treated with sample 2 (15.6 ug/ml) showed the largest increase in growth (1159.39%) when compared to control cells (525.26%). Taken together, these results suggest that the fraction of the RT water extract of silkworm pupa referred to as sample 2 may be useful as a phytoestrogen.

Characterization and degradation of pectin derived from Budimka apple

The characterization of apple pectin and its oligogalacturonic fractions derived from the autochthones apple variety Budimka, characteristic for central Serbia, is described in this paper. After extraction, the apple pectin was subjected to controlled enzymatic hydrolysis by polygalacturonase (PG) and pectin lyase (PL) from Aspergillus niger and then fractionated by ion-exchange column chromatography on Dowex 1X-8 (200-400 mesh). Saturated oligo?galacturonic acids, obtained by controlled hydrolysis with PG, were efficiently separated by elution with a gradient of Na acetate buffer (pH 6.0), while unsaturated oligogalacturonic acids, obtained by controlled hydrolysis with PL, were separated on the same resin, using a gradient of Na formate buffer (pH 4.7) as the eluent. The yields of the fractions with the particular degree of polymerization (DP) were also determined. The total content of neutral saccharides in the original Budimka apple pectin was detected by HPLC analysis of the 4-nitrobenzoyl derivatives of the sugar, and amounted to 5.31%. Among the neutral saccharides, contents of galactose, glucose, rhamnose, arabinose, xylose and mannose were detected.

Determination of tellurium at ultra-trace levels in drinking water by on-line solid phase extraction coupled to graphite furnace atomic absorption spectrometer

In this paper, two time-based flow injection (FI) separation pre-concentration systems coupled to graphite furnace atomic absorption spectrometry (GFAAS) for tellurium determination are studied and compared. The first alternative involves the pre-concentration of the analyte onto Dowex 1X8 employed as packaging material of a micro-column inserted in the flow system. The second set-up is based on the co-precipitation of tellurium with La(OH) 3 followed by retention onto XAD resins. Both systems are compared in terms of limit of detection, linear range, RSD%, sample throughput, micro-columns lifetime and aptitude for fully automatic operation. The features of the Dowex system are: 37% efficiency of retention and an enhancement factor of 42 for a pre-concentration time of 180 seconds (sample flow rate = 3 ml min − 1 ) with acetic acid elution volumes of 80 μl. The detection limit (3 s) is 7 ng l − 1 and the relative standard deviation ( n = 7200 ng l − 1 ) is 5.8%. The analytical performance of the XAD system is: 72% efficiency of retention and an enhancement factor of 25 for a pre-concentration time of 180 s (sample flow rate = 3 ml min − 1 ) with nitric acid elution volumes of 300 μl. The detection limit is 66 ng l − 1 and the relative standard deviation ( n = 7200 ng l − 1 ) is 8.3%. Applications to the determination of tellurium in tap water and the validation of the analytical methodology employing SRM 1643e as certified reference material are shown.

Inorganic selenium speciation in groundwaters by solid phase extraction on Dowex 1X2

A Dowex 1X2 resin separation technique followed by analysis with atomic absorption spectroscopy was evaluated for the study of inorganic selenium speciation in groundwaters. After Se(IV) and Se(VI) were retained on the resin column, Se(IV) and Se(VI) were eluted out by 0.1 and 1 M nitric acid solutions. The method detection limit was 5.6 ng/L for both Se(IV) and Se(VI). Analysis of synthetic solutions consistently yielded more than 90% recovery of these two selenium forms with negligible cross-contamination. The results of spiked well waters show that this method can be applied at ultra-trace level of Se in groundwater and the interference of chloride ion can be neglected. Water samples collected from the monitoring wells in the Science-based Industrial Park, Hsin-Chu, Taiwan, were analyzed. Average dissolved selenium concentrations were 32.1 ± 17.6 ng/L. The proportion of Se(VI) to the total dissolved selenium ranged from 47.6 to 61.2% and an average of 53.8% in water samples analyzed.

Determination of Silicate in Anthropogenically Impacted Natural Waters Using Flow Injection Spectrophotometry

An optimised flow injection (FI) method suitable for the determination of silicate in the presence of high concentrations of arsenate (216 µg As L -1 ) in anthropogenically impacted natural waters is presented. The proposed method has a practical limit of detection of 10 µg Si L -1 and typical RSDs of ≈1.5 % (n = 3) and a sample throughput of 40 samples h -1 . Strategies are presented for the removal of matrix interferences. The manifold incorporates a thiosulfate stream to remove arsenate (AsO4 3) by reduction to arsenite (AsO3 3) and two micro-columns containing a chelating resin (iminodiacetate) to remove metal ions and an anion exchange resin (Dowex 1X8, 200–400 mesh, Cl - form) to remove phosphate. The chelating column successfully removed matrix cations; Cu(II) at 0.1 mg L -1 , Ni(II), Co(II), Fe(II) and Fe(III) at 1.0 mg L -1 and Mn(II), Zn(II) and Pb(II) at 10 mg L -1 . The anion exchange column effectively removed phosphate interference by complexing up to 1.5 mg P L -1 and had no effect on the silicate response. A linear calibration was obtained with the optimised manifold in the range 10 - 1000 µg Si L -1 (R 2 = 0.998). This method was applied to the determination of Si in the Tamar Estuary, an area of historical mining activity, and the results compared well with those from a segmented flow analyser standard method with spectrophotometric detection (P = 0.05; tcal = 1.44 and tcrit = 2.14).

Evaluation of New Anion Exchange Resins for Plutonium Processing

This paper presents the results of studies comparing the performance of two new anion exchange resins for plutonium processing with the well proven and widely used benchmark, Dowex 1X4 resin. In this connection, the experiments on distribution ratio measurement of plutonium as a function of nitric acid concentration, Pu(IV) sorption kinetics, chemical, thermal, and radiation degradation of the two commercially available anion exchange resins namely, Tulsion A‐PSL 4 and Tulsion A‐PSL 6 have been studied, vis‐à‐vis the benchmark. Tulsion A‐PSL 6 was found to have higher plutonium sorption capacity and polymer matrix stability as well as better kinetics of sorption than the other two resins, while Tulsion A‐PSL 4 and Dowex 1X4 were found to have comparable sorption capacity, kinetics, and resistance to chemical and radiation degradation. The small‐scale evaluation of these new anion exchange resins shows that they can be used for the purification and concentration of plutonium.

Determination of Ca, Mg, Fe and Zn partitioning in UHT cow milks by two-column ion exchange and flame atomic absorption spectrometry detection

An operationally defined fractionation protocol was developed to study the partitioning of Ca, Mg, Fe and Zn in UHT cow milks. The method was based on sorption of distinct metal species by two ion exchange columns, namely strong cation exchanger Dowex 50Wx4 and strong anion exchanger Dowex 1x4, connected in a series. The evaluation of the donation of metal species classes distinguished, that is cationic and anionic fractions, was made after splitting the columns and elution of metal groupings with a 2.0 mol l −1 HCl solution, followed by the determination of metal concentrations in the resulting eluates. The amount of third, inert fraction was assessed by measuring metal contents in the effluents obtained after passage of the samples through the columns. The results achieved utilizing two-column ion exchange based procedure were compared with those obtained for the approach in which the columns were considered separately. The fractionation pattern for each metal studied was thoroughly discussed in light of available knowledge relating to the composition of milk.

Simple and versatile operational fractionation of Fe and Zn in dietary products by solid phase extraction on ion exchange resins

A simple and versatile protocol, based on use of solid phase extraction on strong ion exchangers and off-line detection by flame atomic absorption spectrometry, was devised to fractionate iron and zinc in common dietary food and beverages products, i.e., bee honeys, fruit juices and tea infusions. In the procedure proposed, cation exchanger Dowex 50Wx4 and anion exchanger Dowex 1x4 were used separately for distinguishing broadly meant the cationic metal fraction and the fraction of stable anionic metal complexes, respectively, after retention of metal species and their exhaustive elution by means of a 4.0 mol l −1 HCl solution. The third fraction, referred to the residual metal species, was retrieved by difference between total soluble metal contents and sum of metal quantities in separated cationic and anionic fractions. The fractionation pattern observed for both metals was described and discussed.

Fractionation of calcium and magnesium in honeys, juices and tea infusions by ion exchange and flame atomic absorption spectrometry

An analytical procedure was proposed to study the operational fractionation of Ca and Mg in bee honeys, fruit juices and tea infusions. The protocol devised was based on the solid phase extraction of distinct metal fractions on different sorbents, namely strong acidic cation exchanger Dowex 50Wx4, weak acidic cation exchanger Diaion WT01S and strong basic anion exchange resin Dowex 1x4. For the evaluation of the amounts of the metal fractions distinguished, a flame atomic absorption spectrometry was used off-line prior to the determination of Ca and Mg concentrations in the effluents obtained. It was established that Ca and Mg are mostly present in the analysed samples in the form of cationic species (96–100%). The accuracy of the entire fractionation scheme and sample preparation procedures involved was verified by the performance of the recovery tests.

Synthesis in vitro of novel nucleic-acid-like polymers of Ehrlich ascites tumor cells.

1 When cytoplasmic particles isolated from Ehrlich ascites tumor cells were incubated with [14C]ribose, es and inorganic phosphate in the presence of MgCl2 and Tris/HCl (pH 7.0), radioactivity was incorporated into trichloroacetic-acid-insoluble materials. 2 Radioactive products, extracted and purified by DEAE-cellulose column chromatography, were hydrolyzed in i M HCl at 100°C for 1 h and the resultant radioactive neutral sugar components were purified and identified as ribose, glucose and rhamnose by gas chromatography and mass spectrometry. 3 When [14C]glucose was incubated in the same reaction system, radioactivity was also incorporated into trichloroacetic-acid-insoluble materials. Purified radioactive products were hydrolyzed in 1 M HCl at 100°C for 1 h and the resultant radioactive neutral sugar components were also shown to be ribose, glucose and a little rhamnose, as was the case with the products synthesized from [14C]ribose. 4 When [14C]deoxyribose was incubated in the same reaction system, little incorporation was observed. 5 The radioactive products were incubated with venom phosphodiesterase and the digests were analyzed by Dowex lX4 column chromatography. The results suggest that the radioactive products contained ribo-nuclcotides and ‘nucleotides’ containing glucose (glucose ‘nucleotides’). 6 When the radioactive products were incubated with both venom phosphodiesterase and alkaline phosphatase, ribonucleosides and glucose ‘nucleosides’ were detected. In Dowex 1X4 (borate form) chromatography, tibonuclcosides were eluted coincidentalhy with ribonucleoside markers (Cyd Ado Urd and Guo), whereas the elution profiles of glucose ‘nucleosides’ were totallydifferent fromfacto of ribonucleosides.

Lipase immobilized by different techniques on various support materials applied in oil hydrolysis

Batch hydrolysis of olive oil was performed by Candida rugosa lipase immobilized on Amberlite IRC-50 and Al2O3. These two supports were selected out of 16 carriers: inorganic materials (sand, silica gel, infusorial earth Al2O3), inorganic salts (CaCO3, CaSO4), ion-exchange resins (Amberlite IRC-50 and IR-4B, Dowex 2X8), a natural resin (colophony), a natural biopolymer (sodium alginate), synthetic polymers (polypropylene, polyethylene) and zeolites. Lipase immobilization was carried out by simple adsorption adsorption followed by cross-linking, adsorption on ion-exchange resins combined adsorption and precipitation, pure precipitation and gel entrapment. The suitability of the supports and techniques for the immobilization of lipase was evaluated by estimating the enzyme activity, protein loading immobilization efficiency and reusability of the immobilizates. Most of the immobilizates exhibited either a low enzyme activity or difficulties during the hydrolytic reaction. Only those prepared by ionic adsorption on Amberlite IRC-50 and by combined adsorption and precipitation on Al2O33 showed better activity, 2000 and 430 U/g support, respectively, and demonstrated satisfactory behavior when used repeatedly. The hydrolysis was studied as a function of several parameters: surfactant concentration, enzyme concentration, pH and temperature. The immobilized preparation with Amberlite IRC-50 was stable and active in the whole range of pH (4 to 9) and temperature (20 to 50 ?C), demonstrating a 99%degree of hydrolysis. In repeated usage, it was stable and active having a half-life of 16 batches which corresponds to an operation time of 384 h. Its storage stability was remarkable too, since after 9 months it had lost only 25 % of the initial activity. The immobilizate with Al2O3 was less stable and less active. At optimal environmental conditions, the degree of hydrolysis did not exceed 79 %. In repeated usage, after the fourth batch, the degree of hydrolysis was reduced to 53.5 %.

Ion‐Exchange Separation of Pu from Macro Concentration of Th in HNO3 Medium

Sorption behavior of Th and Pu from anion‐ as well as cation‐exchange resin was investigated from nitric acid medium by both batch and column methods. The anion‐exchange studies involved anionic nitrate complexes of Pu4+ and Th4+ sorbed onto DOWEX 1x4 resin (50–100 mesh), and the cation‐exchange studies involved the sorption of Pu3+ and Th4+ onto BIORAD AG 50Wx8 (50–100 mesh) or DOWEX 50Wx4 (50–100 mesh) resin. The batch data gave a separation factor (K d,Pu/K d,Th) of 22 for the anion‐exchange method and 0.017 for the cation‐exchange method at 3 and 2 M HNO3, respectively. A two‐stage ion‐exchange separation method was developed for the quantitative separation of Pu (8 g/L) from a macro amount of Th (200 g/L) in nitric acid medium. The first step involved the quantitative sorption of plutonium from the mixture while about 90% of Th could be washed in 6 column volumes. The plutonium, eluted (as Pu3+) using 0.5 M HNO3 + 0.2 M hydrazinium nitrate (HN) + 0.2 M hydroxyl ammonium nitrate (HAN), and the residual (∼10%) Th were subsequently loaded onto a cation‐exchange column in the second step. Greater than 99% Pu was recovered with 2 M HNO3 (in ∼8 column volumes) containing 0.2 M HN + 0.2 M HAN. The final elution of thorium from the cation‐exchange column was achieved in about 6 column volumes of 1 M α‐hydroxy isobutyric acid. A (Pu, Th)O2 fuel scrap sample was dissolved in 16 M HNO3 containing 0.005 M HF and was used subsequently as the feed for the anion‐exchange column. The eluted Pu was subsequently loaded onto a cation‐exchange column for final purification. The recovery of plutonium and thorium was found to be >99% and >98%, respectively, while the respective decontamination factors were estimated to be 215 and 292.

Efeito estrutura da matriz na adsorção de cianocomplexos metálicos em resinas de poliestireno

O objetivo desse trabalho é a utilização de resinas de troca-iônica, base forte, na adsorção de cianocomplexos metálicos, visando a sua reciclagem. São utilizadas soluções sintéticas que simulam diferentes efluentes da lixiviação do minério de ouro, contendo concentrações de ferro, de zinco e de cobre, variando entre 50 e 500mg/l. São realizados ensaios de adsorção, em batelada, utilizando dois tipos de resinas comerciais: Ionac SR-7 (matriz de poliestireno, tripropilamônio quaternário como grupo de troca) e Dowex 1X8 (matriz de poliestireno, trimetilamônio quaternário como grupo de troca). Em ambas resinas houve uma adsorção maior do cianocomplexo de zinco com relação aos outros cianocomplexos metálicos existentes em solução. A ordem do carregamento, nesse caso, foi Zn>Cu>Fe. A resina Dowex 1X8 apresentou um maior carregamento dos cianocomplexos de zinco e de cobre, quando comparados com os carregamentos da outra resina. As diferentes afinidades são discutidas em função das características físico-químicas dos complexos e das estruturas das resinas.

Copper, zinc and manganese determination in saline samples employing faas after separation and preconcentration on Amberlite XAD-7 and Dowex 1x-8 loaded with Alizarin Red S

Two procedures have been proposed and compared for separation and preconcentration of trace amounts of manganese, copper, and zinc in saline samples. The procedures are based in the use of Amberlite XAD-7 and an anion-exchanger Dowex 1X8-50 loaded with Alizarin Red S (ARS). In order to obtain quantitative recoveries of metal ions, various experimental parameters such as pH, shaking time, sample volume, amounts of solid phase, effects of concomitants, capacity and cations desorptions from solid phases were optimized. For Amberlite XAD-7 impregnated with ARS (XAD 7-ARS), Mn, Cu, and Zn were quantitatively retained, in the pH range 8.5-10.0, by using 0.50 g of solid phase, stirring time of 5 min and a total mass up to 200 µg of each cation. The sorbed elements were subsequently eluted with 5 mL of 3 mol L-1 HNO3, with recovering over 95%, and a fifty-fold preconcentration factor for Zn and a ten-fold preconcentration factor for Mn and Cu were obtained. For Dowex 1X8-50 impregnated with ARS (Dowex-ARS), Cu and Mn were quantitatively retained in the pH range 8.1 to 9.0, and Zn pH 8.1, by using 0.75 g of solid phase, 90 min of stirring time and a total mass up to 50 µg of each cation. The sorbed elements were subsequently eluted with 20 mL of 2 mol L-1 HNO3, and a five-fold preconcentration factor to Cu and Zn was obtained. The precision of the procedure was determined by running 10 replicate samples, each one containing 250 µg L-1 of each element and the relative standard deviations were 0.2% (Cu), 0.4% (Mn), and 0.4% (Zn), to XAD 7-ARS and 0.3% (Cu), 0.5% (Mn), and 0.3% (Zn), to Dowex-ARS. The procedures were used for determining of Mn, Cu, and Zn in physiological solutions and seawater samples, from Salvador-Bahia. The analyte addition technique was used and the recoveries obtained (³ 95%) revealed that the proposed procedure shows good accuracy and precision.

Screening of Dowex<SUP>®</SUP> Anion-Exchange Resins for Invertase Immobilization

Commercial yeast invertase (Bioinvert) was immobilized by adsorption on anion-exchange resins, collectively named Dowex(R) (1x8:50-400, 1x4:50-400, and 1x2:100-400). Optimal binding was obtained at pH 5.5 and 32 degrees C. Among different polystyrene beads, the complex Dowex-1x4-200/invertase showed a yield coupling and an immobilization coefficient equal to 100%. The thermodynamic and kinetic parameters for sucrose hydrolysis for both soluble and insoluble enzyme were evaluated. The complex Dowex/invertase was stable without any desorption of enzyme from the support during the reaction, and it had thermodynamic parameters equal to the soluble form. The stability against pH presented by the soluble invertase was between 4.0 and 5.0, whereas for insoluble enzyme it was between 5.0 and 6.0. In both cases, the optimal pH values were found in the range of the stability interval. The Km and Vmax for the immobilized invertase were 38.2 mM and 0.0489 U/mL, and for the soluble enzyme were 40.3 mM and 0.0320 U/mL.

Simple, Rapid and Sensitive Determination of Bismuth in Iron and Steel Based on In-line Preconcentration/separation Directly Coupled with Spectrophotometric Detection in a Continuous Flow System

A novel flow injection system is presented for simple, rapid and selective determination of bismuth at sub-ppm levels in iron and steel by coupling in-line anion exchange preconcentration/separation directly with spectrophotometric detection. Bismuth in 0.5 M HCI solution was adsorbed on a small column packed with Dowex 1X8 anion exchange resin and desorbed with a small volume of 0.5 M H 2 SO 4 , which allowed effective preconcentration/separation of bismuth from a large excess of iron(III) and other coexistent elements in the steel samples. Bismuth was detected by complex formation with iodide in 0.5 M H 2 SO 4 yielding a yellow color. Various analytical parameters were investigated, and optimal conditions and manifold configurations were established. A linear calibration using a 10 m sample loop was obtained for bismuth in the range of 0.005-0.30 ppm. The relative standard deviation for 0.1 ppm bismuth in the solution was 0.8% (n=5). The estimated limit of determination is ca. 0.2ppm in steel sample when a 5 m sample loop (1.0 mm i.d.) is used. The results for analyses of steel samples by the present Fl system correspond well with those obtained by AAS methods. The present Fl system affords a rapid and simple analysis: only 12 min is required for analytical measurement after sample injection, and no complicated manual operation is involved.

HPLC–ICP-MS speciation of selenium in enriched onion leaves – a potential dietary source of Se-methylselenocysteine

In this work chromatographic separation was coupled with mass spectrometry detection to study the speciation of selenium in selenium enriched onion leaves. The plants of onion ( Allium cepa L.) were grown hydroponically for one week in standard medium containing inorganic selenium. The leaves and bulbs were separated from roots, the two types of material (leaves and bulbs) were dried and homogenized. The sodium hydroxide (0.1 mol l −1) extracts were analyzed by size exclusion chromatography (with spectrophotometric and mass spectrometric detection) showing the incorporation of selenium to the high molecular weight fraction, which was more pronounced in the leaves relative to the bulbs. This incorporation was better with Se(IV) enrichment (33% in leaves and 26% in bulbs) than with Se(VI) (3% and 5%, respectively). After extraction of the low molecular weight compounds (chloroform–methanol–water or 0.4 M perchloric acid–ethanol) and elimination of inorganic selenium (Dowex 1X8), selenium speciation was carried out by ion-pairing high performance chromatography [5 mmol l −1 citric acid, 5 mmol l −1 hexanesulfonic acid, pH 4.5: methanol (95:5)]. The primary organic selenium species found in leaves extracts was Se-methylselenocysteine, which has been reported as one of the most active chemopreventive selenium species as found in cell and animal experiments. The percentage contribution of selenium in this species was 4.0% and 1.9%, respectively, of the total selenium in leaves enriched with Se(IV) and Se(VI). It may be possible to use selenium enriched leaves as a dietary source of Se-methylselenocysteine. The important advantage of this source is the simple and fast enrichment process.