Development of recoverable adsorbents for Cr(VI) ions by grafting of a dimethylamino group-containing monomer on polyethylene substrate and subsequent quaternization.

A polymeric adsorbent for removal of hexavalent chromium (Cr(VI)) ions was developed by the photografting of 2-(dimethylamino)ethyl methacrylate (DMAEMA) to a polyethylene (PE) mesh and subsequent quaternization with iodoalkanes of different alkyl chain lengths. The grafting of DMAEMA and subsequent quaternization were verified by the FT-IR and XPS measurements. The Cr(VI) ion adsorption capacity of the DMAEMA-grafted PE meshes had the maximum value at the grafted amount of 2.6 mmol/g in a 0.20 mM K2Cr2O7 solution at pH 3.0 and 30°C. The adsorption behaviour obeyed the pseudo-second order kinetic model and well expressed by Langmuir isotherm. These results suggest that the Cr(VI) ion adsorption occurs through the electrostatic interaction mainly between protonated dimethylamino groups and hydrochromate (HCrO4-) ions. The adsorption capacity of the quaternized PE-g-PDMAEMA meshes increased with an increase in the degree of quaternization and/or the alkyl chain length of the iodoalkanes used and the maximum adsorption ratio was obtained at the degree of quaternization of 54.2% for the iodoheptane-quaternized PE-g-PDMAEMA (PE-g-QC7PDMAEMA) mesh. This value was about 1.86 times higher than that of the PE-g-PDAMEMA mesh. Cr(VI) ions were successfully desorbed from the PE-g-PDMAEMA and PE-g-QC7PDMAEMA meshes in eluents such as NaOH, NaCl, and NH4Cl. In 0.50 M NaCl, 0.10 M NH4Cl, and 0.50 mM NaOH, the adsorption and desorption process was repeatedly performed without any considerable decrease and the desorption behaviour obeyed the pseudo-second order kinetic model. These results emphasise that the PE-g-PDMAEMA meshes and their quaternized products can be applied as an adsorbent for Cr(VI) ions.

Kinetic, Isotherm, and Equilibrium Investigation of Cr(VI) Ion Adsorption on Amine-Functionalized Porous Silica Beads.

The hexavalent chromium (Cr(VI)) ion adsorption properties were conferred to porous silica beads by introducing alkylamine chains through functionalization with an aminosilane coupling agent, [3-(2-aminoethylamino)propyl]triethoxysilane (AEAPTES), or with an epoxysilane coupling agent, (3-glycidyloxypropyl)triethoxysilane (GOPTES), and polyfunctional amine compounds or poly-ethylenimines (PEIs). The presence of amino groups on the silica beads was confirmed by XPS and the amount of amino groups increased to 0.270 mmol/g by increasing the AEAPTES concentration and/or reaction time. The adsorption capacity of the silica beads functionalized with AEAPTES was the maximum at the initial pH value of 3.0 and the initial adsorption rate increased with an increase in the temperature. The adsorption capacity increased with an increase in the amount of amino groups at pH 3.0 and 30 °C. The adsorption behavior obeyed the pseudo-second order kinetic model and was well expressed by the Langmuir isotherm. These results support that Cr(VI) ion adsorption is accomplished through the electrostatic interaction between protonated amino groups and HCrO4- ions. In addition, the adsorption capacity further increased to 0.192-0.320 mmol/g by treating the GOPTES-treated silica beads with triethylenetetramine, pentaethylenehexamine, or PEI. These empirical, equilibria, and kinetic aspects obtained in this study support that the porous silica-based adsorbents prepared in this study can be applied to the removal of Cr(VI) ions.

Enhancement of Cr(VI) ion adsorption by two-step grafting of methacrylamide (MAAm) and 2-(dimethylamino)ethyl methacrylate (DMAEMA) onto polyethylene plate.

Polyethylene (PE) plates grafted with a neutral hydrophilic monomer, methacrylamide (MAAm), and a cationic monomer, 2-(dimethylamino)ethyl methacrylate (DMAEMA), (PE-g-PMAAm)-g-PDMAEMA plates, were prepared by the two-step photografting. The Cr(VI) ion adsorption of the resultant (PE-g-PMAAm)-g-PDMAEMA plates was investigated as a function of the initial pH value, temperature, and grafted amounts of PMAAm and PDMAEMA. The adsorption capacity of the (PE-g-PMAAm)-g-PDMAEMA plates had the maximum at the initial pH value of 3.0 and the initial adsorption rate increased with the temperature and increased with the amount of grafted DMAEMA. This result suggests that protonated dimethylamino groups present in the inside of the grafted layer are increasingly involved in the Cr(VI) ion adsorption by the increase in the water absorptivity through the formation of the intermediate grafted layer of PMAAm. The maximum adsorption ratio of 0.510 was obtained for a (PE-g-PMAAm)-g-PDMAEMA plate with GMAAm = 30 µmol/cm2 and GDMAEMA = 1.7 µmol/cm2. The maximum adsorption capacity obtained in this study was comparable to or higher than those of other adsorbents for Cr(VI) ions. The adsorption behaviour obeyed the pseudo-second order kinetic model and was well described by the Langmuir isotherm model, suggesting that the adsorption of Cr(VI) ions occurs through the electrostatic interaction between protonated dimethylamino groups and HCrO4- ions. Cr(VI) ions were successfully desorbed in such eluents as NaCl, NaCl containing NaOH, NH4Cl, NH4Cl containing NaOH, and NaOH and (PE-g-PMAAm)-g-PDMAEMA plates were repeatedly used without considerable loss in the adsorption capacity.

Hexavalent Cr ion adsorption and desorption behaviour of expanded poly(tetrafluoro)ethylene films grafted with 2-(dimethylamino)ethyl methacrylate.

A new polymeric adsorbent for Cr(VI) ions based on an expanded poly(tetrafluoroethylene) (ePTFE) film was prepared by the combined use of the pretreatment with oxygen plasma and photografting of 2-(dimethylamino)ethyl methacrylate (DMAEMA). The grafting of DMAEMA was characterized by XPS and FT-IR spectroscopic measurements. The adsorption behaviour of DMAEMA-grafted ePTFE (ePTFE-g-PDMAEMA) films was investigated as a function of the experimental parameters, such as the initial pH value, temperature, and grafted amount. The adsorption capacity and initial adsorption rate had the maximum values at the initial pH value of 3.0. On the other hand, the adsorption capacity became almost constant at temperatures higher than 30°C, although the adsorption rate increased over the temperature. The adsorption behaviour obeyed the pseudo-second-order kinetic model and well expressed by the Langmuir isotherm equation with higher correlation coefficients. These results indicate that the adsorption of Cr(VI) ions occurs through the electrostatic interaction between protonated dimethylamino groups on a grafted PDMAEMA chain and HCrO4- ions. Cr(VI) ions were successfully desorbed from Cr(VI)-loaded ePTFE-g-PDMAEMA films in the eluents, such as NaCl at 0.50 M, NH4Cl at 0.50M, and NaOH at 1.0 mM, and ePTFE-g-PDMAEMA films were repeatedly used for adsorption of Cr(VI) ions without appreciable loss in the adsorption capacity. It should be noted that Cr(VI) ion adsorptivity with a high initial rate was conferred to the ePTFE films. The results obtained in this study emphasize that ePTFE-g-PDMAEMA films can be applied as an adsorbent for Cr(VI) ions.

[A Method Based on Ru(bpy)3 3+ Electrogenerated Chemiluminescence for Assessment of Antioxidant Property of Naturally Occurring Antioxidants].

We developed a flow injection analysis (FIA) method based on tris(2,2'-bipyridine)ruthenium(III) [Ru(bpy)3 3+] electrogenerated chemiluminescence for assessment of antioxidant property. The hydroxyl radical (∙OH) were generated by H2O photolysis using an ultraviolet/H2O photoreactor. The reactor comprised a polytetrafluoroethylene tube, a quartz container, and a low-pressure mercury lamp that predominantly emitted radiation at around 185 nm. When the hydroxyl radical and Ru(bpy)3 3+ were in contact, chemiluminescence was generated as background emission. The background emission decreased when antioxidant samples were injected to the system. The antioxidant property of the naturally occurring antioxidants tested are listed herein, starting with the highest: gallic acid>ascorbic acid>quercetin. Moreover, our method allowed a sample throughput of approximately 100 samples/h. The proposed high throughput method can be used to assess the antioxidant property of the naturally occurring antioxidants.

Two-step grafting of 2-hydroxyethyl methacrylate (HEMA) and 2-(dimethylamino)ethyl methacrylate (DMAEMA) onto a polyethylene plate for enhancement of Cr(VI) ion adsorption.

Polyethylene (PE) plates grafted with a neutral monomer, 2-hydroxyethyl methacrylate (HEMA), and a cationic monomer, 2-(dimethylamino)ethyl methacrylate (DMAEMA), (PE-g-PHEMA)-g-PDMAEMA plates were prepared by the two-step photografting. The Cr(VI) ion adsorption behavior of the (PE-g-PHEMA)-g-PDMAEMA plates was investigated as a function of the amounts of grafted HEMA, amount of grafted DMAEMA, initial pH value, and temperature. The adsorption capacity of the DMAEMA-grafted PE (PE-g-PDMAEMA) and (PE-g-PHEMA)-g-PDMAEMA plates had the maximum value at the initial pH value of 3.0, independent of the temperature. The adsorption capacity of (PE-g-PHEMA)-g-PDMAEMA plates increased with the amount of grafted HEMA (GHEMA) in the first-step grafting. The increase in the water absorptivity of the grafted layers and thereby the increase in the degree of protonation of dimethylamino groups on grafted PDMAEMA chains were found to lead to the increase in the adsorption capacity. This adsorption capacity was higher than or comparable to those of other polymeric adsorbents for Cr(VI) ions. The Cr(VI) ion adsorption behavior on both PE-g-DMAEMA and (PE-g-PHEMA)-g-PDMAEMA plates obeyed the mechanism of the pseudo-second-order kinetic model and was well expressed by Langmuir isotherm. The high values of the Langmuir constant suggest that the adsorption of Cr(VI) ions occurs through an electrostatic interaction between protonated dimethylamino groups on grafted PDMAEMA chains and HCrO4- ions. Cr(VI) ions were successfully desorbed from PE-g-PDMAEMA and (PE-g-PHEMA)-g-PDMAEMA plates in eluents such as NaCl, NaCl containing NaOH, NH4Cl, NH4Cl containing NaOH, and NaOH.

Determination of Miglitol by Column-Switching Ion-Pair HPLC with Tris(2,2'-bipyridine)ruthenium(II)-Electrogenerated Chemiluminescence Detection.

We have developed a highly sensitive, simple method for the quantitative determination of miglitol in standard serum samples using column-switching ion-pair HPLC with tris(2,2'-bipyridine)ruthenium(II)-electrogenerated chemiluminescence detection. The serum samples were directly injected into a column-switching HPLC system with a Shim-pack MAYI-SCX precolumn to remove the serum matrix. Chromatographic separation of miglitol was achieved on a TSKgel ODS 100-V column using a mobile phase containing sodium 1-octanesulfonate as an ion-pair reagent. The detection and quantification limits of miglitol were 3 and 10 ng/mL, respectively. The calibration curve for miglitol in the serum samples showed good linearity (r(2)=0.9997) in the range of 10-2500 ng/mL. The recovery rate of miglitol from the serum samples was more than 94% as calculated from blank serum samples spiked with miglitol 50, 100, 500, 1000, and 2000 ng/mL. Therefore, this method can be applied to routine therapeutic monitoring of miglitol in serum samples.

Application of an improved proteomics method, fluorogenic derivatization-liquid chromatography-tandem mass spectrometry, to differential analysis of proteins in small regions of mouse brain.

To identify age-related proteins in small regions of mouse brain, we improved a proteomics approach, fluorogenic derivatization-liquid chromatography-tandem mass spectrometry (FD-LC-MS/MS), and applied the method to the differential proteome analysis of aging in cerebral cortex, hippocampus and brainstem. The method showed good accuracy with RSDs <10% for between-day protein peak heights, and much better sensitivity for the detection of proteins compared to other proteomics approaches. The existence of 28 regionally specific age-related proteins in mouse brain was demonstrated. These results verified that the small brain regions could be the targets for proteome analysis by the FD-LC-MS/MS method.

Existence of low-molecular-weight thiols in Caenorhabditis elegans demonstrated by HPLC-fluorescene detection utilizing 7-chloro-N-[2-(dimethylamino)ethyl]-2,1,3-benzoxadiazole-4-sulfonamide.

A highly sensitive and simple method using HPLC-fluorescence detection with 7-chloro-N-[2-(dimethylamino)ethyl]-2,1,3-benzoxadiazole-4-sulfonamide (DAABD-Cl) as a fluorogenic reagent demonstrated the existence of the low-molecular-weight thiols in the extract of Caenorhabditis elegans (C. elegans). The method includes derivatization of the thiols with DAABD-Cl at 40 degrees C for 10 min in borate buffer (pH 9.0) containing TCEP, CHAPS and EDTA, separation of the derivatives on an ODS column and fluorometric determination of the derivatives at 510 +/- 15 nm with excitation at 400 +/- 15 nm. The identification of the thiols was made by HPLC-electrospray ionization mass spectrometry (LC-MS) following isolation of the derivatives using HPLC-fluorescence detection. Low-molecular-weight thiols were found to exist in the extract of C. elegans, such as cysteine, cysteinylglycine, gamma-glutamylcysteine, reduced glutathione and two other unidentified thiol compounds, confirming the existence of the 'glutathione cycle' in C. elegans similar to the mammalian body.