Ion-exchange Liquid Research Articles

Converting A/I values (ion exchange) to D/L values (reverse phase) for amino acid geochronology

Abstract Several analytical techniques have been used in amino acid geochronology to measure the relative abundances of D- and L-enantiomers. During the past two decades, reverse-phase (RP) liquid chromatography has become most common, whereas ion-exchange (IE) liquid chromatography was widely used prior to the mid-1990s. This study is based on intra-lab paired analyses of RP and IE liquid chromatography to mathematically convert A/I (allo-isoleucine:isoleucine) values determined with IE to corresponding D/L values for comparison with new RP results. Pooled results of 340 paired IE and RP analyses show that A/I values can be confidently converted to equivalent D/L values for aspartic acid, glutamic acid, alanine, valine and isoleucine, with 2σ uncertainties of ±24–41% depending on the amino acid. For specific sample types including gastropod, bivalve, eggshell and whole rock, A/I can readily be converted to D/L aspartic acid and D/L glutamic acid with 2σ uncertainties of ±20% and 26%, respectively, using sample-type-specific relations. A/I is also reliably converted to D/L valine and D/L isoleucine with 2σ uncertainties of ±31 and 35%, respectively. Regression equations are provided to convert A/I to an equivalent D/L value for five amino acids, thereby enabling the large literature base of AAR results from IE chromatography to be compared and integrated with AAR results from RP chromatography.

Conducting polymers with defined micro- or nanostructures for drug delivery.

Conducting polymers (CPs) are redox active materials with tunable electronic and physical properties. The charge of the CP backbone can be manipulated through redox processes, with accompanied movement of ions into and out of the polymer to maintain electrostatic neutrality. CPs with defined micro- or nanostructures have greatly enhanced surface areas, compared to conventionally prepared CPs. The resulting high surface area interface between polymer and liquid media facilities ion exchange and can lead to larger and more rapid responses to redox cycling. CP systems are maturing as platforms for electrically tunable drug delivery. CPs with defined micro- or nanostructures offer the ability to increase the amount of drug that can be delivered whilst enabling systems to be finely tuned to control the extent and rate of drug release. In this review, fabrication approaches to achieve CPs with micro- or nanostructure are outlined followed by a detailed review and discussion of recent advances in the application of the materials for drug delivery.

Synthesis and characteristics of Ce modified HY/SBA-15 and its desulfurization performance for simulated oil

A composite zeolite HY/SBA-15 has been synthesized by an overgrowth approach, and then doped with Ce by a liquid phase ion exchange process to form the Ce modified HY/SBA-15 catalyst. The synthesized materials were examined by X-ray diffraction (XRD), nitrogen adsorption–desorption, transmission electron microscopy (TEM), BJH analysis and pyridine adsorption Fourier-transform infrared spectroscopy (Py-FTIR). The results showed the existence of two different pores sizes of 1.8 and 6 nm. Thus, the HY/SBA-15 composite includes both microporous and mesoporous structures. Desulfurization activity of the composite materials was evaluated using as simulated oil gas. The results showed that the SOx adsorption capacity of Ce-HY/SBA-15 was enhanced by 1.97 mg/g compared to HY/SBA-15, which suggested that the Ce plays an important role in the desulfurization of simulated oil over composite zeolite. Furthermore, the Py-FTIR results revealed the relationship between the surface acids and the desulfurization performance. It was found that the weak Lewis acids were important for the improved desulfurization performance, while the Bronsted acids inhibited the desulfurization performance.

The calibration model in potassium ion flux non-invasive measurement of plants in vivo in situ

SIET (Self-referencing Ion Electrode Technique) provides a novel electrophysiological tool which can non-invasively measure the dynamic influxes and effluxes of ions caused by the diffusion along the concentration gradients in vivo. However, in this technique ion fluxes are converted to voltage signals using an ion selective microelectrode at a small amplitude of μV, which is easy to be interfered by the ambient noise. Hence, effective solutions to the suppression of noise and calibration of ion flux measurement system are very important for this method. A K+-selective microelectrode was constructed using liquid ion exchangers (LIX) to investigate ion transport over plant tissue. A standard concentration gradient which simulates plant living cells was produced by an electrode with a certain tip diameter, filled with a solution containing a known K+ concentration in 100mmol/L. An ion diffusion simulation model was established. This model evaluated the performance of ion flux measurement system in accuracy and reliability by comparing the consistency of the measured value and the predicted curve. K+ fluxes were measured within 25min at each measuring point of distance 10, 20, 30, 40, 50, 80, and 100μm from the K+ source, respectively. It can be seen that the K+ fluxes changes little, which indicates that ion flux measurement system has a reliable stability. The study provides a theoretical basis for a new non-invasive ion flux measurement method creation and a new sensors design.

On the Cu species in Cu/beta catalysts related to DeNOx performance of coupled NSR-SCR technology using sequential monoliths and dual-layer monolithic catalysts

Cu/beta catalysts are prepared starting from protonic or ammonic BEA zeolite following liquid ion exchange with copper. Alternatively, an intermediate ion exchange with Na ions is performed before copper ion exchange. Cu/beta catalysts are extensively characterized by XRF, N2 adsorption–desorption, FT-IR of NO and CO adsorption, EPR, H2-TPR, TEM and SEM in order to identify copper oxidation state (Cu+ or Cu2+) and copper species (agglomerated or Cu ions with different interaction with the support). Cu/beta catalyst prepared from ammonic BEA zeolite with intermediate Na ion exchange followed by copper ion exchange results in the most active catalyst in the NH3-SCR reaction, which is related to the coexistence of Cu+ and Cu2+ ions and to a more accessible location of such ions in the zeolite matrix. This catalyst is washcoated onto a monolithic substrate with an optimum loading of 0.32 g cm−3, in order to be placed downstream a NOx storage and reduction (NSR) monolithic catalyst, prepared by washcoating Pt-Ba/Al2O3 powder with an optimum loading of 0.25gcm−3. NSR-SCR catalyst in sequential beds results in a very active system with a NOx removal of 97% and a N2 selectivity of 96% at 275°C. NSR/SCR catalyst prepared in a unique dual layer device shows that top SCR layer loading can be tuned in order to improve DeNOx performance. Optimum SCR layer loading is observed for 0.02gcm−3, enhancing the NOx to N2 efficiency of single NSR catalyst but far away from the catalytic performance observed for the sequential NSR-SCR configuration.

Possibilities for removal of chlorinated dye Mordant Blue 9 from model waste water‡

AbstractThis comparative study focused on the different methods used for the treatment of model waste water polluted with the chlorinated acid dye Mordant Blue 9. Low-cost and commercially available ionic liquids – benzalkonium chloride and Aliquat 336 – were applied as liquid ion-exchangers to precipitate the Mordant Blue 9 by way of ion pair formation between the bulky ammonium cations of ionic liquids and anions of the above dye. The decolorisation efficiency of the ionic liquid application and the effect on reduction of the absorbance, adsorbable organic halogens, chemical oxygen demand and biological oxygen demand were compared with the conventional coagulation, sorption and Fenton oxidation techniques.

Process development and optimization for platinum recovery from PEM fuel cell catalyst

This paper presents the development of an efficient hydrometallurgical recovery process of platinum from Pt catalyst of PEMFC electrodes at laboratory scale, whereby leaching, Pt separation, precipitation and filtration steps were combined in order to optimize the recovery process. The efficiencies of two different leaching agents (H2O2/HCl and HNO3/HCl) and two different separation methods (liquid–liquid extraction and ion exchange resins) were compared in this study. Finally the platinum was recovered by precipitation as ammonium hexachloroplatinate (NH4)2PtCl6 (a PEMFC catalyst precursor) at the outlet of each process alternative. Thus four different process alternatives were tested and compared.At first the experiments were performed with Pt/C particles and hexachloroplatinic acid in order to study the influence of several experimental parameters on platinum recovery efficiency. Then the real PEMFC catalyst coated membranes (CCMs) were treated according to the optimized leaching/recovery process. Finally, the most efficient process alternative gave a 76% Pt recovery yield from CCMs.

NO의 암모니아 선택적 촉매환원반응을 위한 철 제올라이트 촉매의 내황성에 미치는 조촉매 효과

Fe/제올라이트 촉매의 저온에서의 NO의 암모니아 선택적 촉매환원반응 활성에 미치는 반응가스 중의 수분과 SO₂의 영향을 조사하였다. Fe/제올라이트 촉매에 조촉매로 Mn, Zr과 Ce를 첨가한 Fe/제올라이트 촉매로 수분과 SO₂가 포함된 저온에서의 NO의 암모니아 선택적 촉매환원반응에서 조촉매 첨가효과를 조사하였다. 조촉매는 이온교환법으로 철을 담지시킨 Fe/제올라이트 촉매에 건식 함침법으로 첨가하였다. 제올라이트는 디젤엔진에서의 SCR기술의 적용을 위하여 NH₄-BEA와 NH₄-ZSM-5을 사용하였다. 촉매의 특성은 BET, XRD, SEM/EDS와 TEM/EDS를 사용하여 조사하였다. 반응가스 중에 5% H₂O와 100 ppm SO₂이 존재하는 경우 Fe/BEA 촉매의 NO 전환율은 200 ℃에서 77%에서 47%로 감소하였다. MnFe/BEA 촉매는 수분과 SO₂가 존재하는 경우에 200 ℃에서 53% 이상의 NO 전환율을 나타내며 Fe/BEA 촉매보다 우수한 반응활성을 보였다. Mn은 Fe 성분의 분산도를 증가시키고 Fe의 소중합체 형성을 방지하는 효과를 나타내었다. 첨가제는 Mn이 Zr과 Ce보다 우수한 특성을 나타내었다. 250 ℃ 이하의 온도에서 Fe/BEA 촉매가 Fe/ZSM-5 촉매보다 우수한 반응특성을 나타내었다. The effects of H₂O and residue SO₂ in flue gases on the activity of the Fe/zeolite catalysts for low-temperature NH₃-SCR of NO were investigated. And the addition effect of Mn, Zr and Ce to Fe/zeolite for low-temperature NH₃-SCR of NO in the presence of H₂O and SO₂ was investigated. Fe/zeolite catalysts were prepared by liquid ion exchange and promoted Fe/zeolite catatysts were prepared by liquid ion exchange and doping of Mn, Zr and Ce by incipient wetness impregnation. Zeolite NH₄-BEA and NH₄-ZSM-5 were used to adapt the SCR technology for mobile diesel engines. The catalysts were characterized by BET, X-ray diffraction (XRD), SEM/EDS, TEM/EDS. The NO conversion at 200 ℃ over Fe/BEA decreased from 77% to 47% owing to the presence of 5% H₂O and 100 ppm SO₂ in the flue gas. The Mn promoted MnFe/BEA catalyst exhibited NO conversion higher than 53% at 200 ℃ and superior to that of Fe/BEA in the presence of H₂O and SO₂. The addition of Mn increased the Fe dispersion and prevented Fe aggregation. The promoting effect of Mn was higher than Zr and Ce. Fe/BEA catalyst exhibited good activity in comparison with Fe/ZSM-5 catalyst at low temperature below 250 ℃.

Properties and catalytic performance in phenol hydroxylation of iron on zeolite beta prepared by different methods

Iron (Fe) was loaded on zeolite beta (BEA) in ammonium (NH4BEA) or proton (HBEA) forms by various methods. Fe/HBEA-LSIE and Fe/NH4BEA-LSIE were prepared by liquid state ion exchange (LSIE). This method resulted in low Fe loading and a good dispersion. The form of Fe was Fe2O3 mainly located at the ion exchange position in the zeolite channels. Fe/HBEA-IWI and Fe/HBEA-PM were prepared by incipient wetness impregnation (IWI) and physical mixing (PM), respectively. Both catalysts had higher Fe loading and larger Fe2O3 particles located on both external surface and in the zeolite channels. Despite the different loadings, all samples gave similar phenol conversion in phenol hydroxylation, around 60 % and yielded products catechol (CAT) and hydroquinone (HQ) with the CAT/HQ mole ratio 2:1. After the catalytic testing, all catalysts had a dark color from coking. A further investigation revealed a formation of coke and organic acids. According to temperature programmed oxidation (TPO), heavy coke was produced from Fe/HBEA-LSIE and Fe/NH4BEA-LSIE. The coke from Fe/HBEA-LSIE was heavier than that from Fe/NH4BEA-LSIE. Only light coke was produced from Fe/HBEA-IWI and Fe/HBEA-PM.

ПОРІВНЯЛЬНЕ ВИВЧЕННЯ АМІНОКИСЛОТНОГО СКЛАДУ СУХИХ ПОРОШКІВ БІОМАСИ FLAMMULINA VELUTIPES, ЯКІ ОТРИМАНІ МЕТОДАМИ ПОВЕРХНЕВОГО ТА ГЛИБИННОГО КУЛЬТИВУВАННЯ

<p class="Default"><strong>Summary: </strong> qualitative composition and quantitative content of 17 amino acids, including 7 essential were defined in <em>Flammulina</em><em> velutipes</em> medicinal mushroom’s biomass dry powders. Biomass powders were received in static conditions and by submerged culture.</p><p class="Default"><strong>Key words:</strong> biomass, <em>Flammulina velutipes</em>, cultivation in static conditions, submerged culture, aminoacids, liquid chromatography.</p><p class="Default"><strong> </strong></p><p><strong>Introduction</strong><strong>. </strong>The medicinal mushroom <em>Flammulina (F.) velutipes</em> is widely used in non-traditional and officinal Eastern medicine as immunomodulatory, antitumor, antioxidant, antihypertensive, antibacterial, antifungal, antiviral agent [5; 6].</p><p>Polysaccharide content of <em>F. velutipes</em> biomass was identified in previous studies [7]. Continuing work on the study of bioactive substances of medicinal mushroom we conducted determination of biomass dry powders amino acid composition.</p><p>Amino acids are widely used in medicine for the treatment of neuropsychiatric disorders, some diseases of the gastrointestinal tract and liver, for the prevention of atherosclerosis, to increase immunity and to inhibit tumor development, etc. [1 - 4].</p><p>Thus, the purpose of this work was to determine and compare amino acids qualitative composition and quantitative content in <em>F. velutipes</em> biomass dry powders.</p><p><strong>Materials and methods</strong><strong></strong></p><p>The objects of our study were two types of medicinal mushroom <em>F. velutipes</em> biomass dry powders. They were obtained by two methods of microbiological synthesis – cultivation in static conditions and by submerged culture.</p><p>Water suspension with waste of CO<sub>2</sub>-extraction – Amaranthus flour (60 g/l) as a submerged culture medium for <em>F. velutipes</em> biomass production was explored. Mycelia were grown in 500 ml of microbial mattress at 26 ±1°C and pH value 6,0. Biomass was dried in a vacuum freeze dryer Cryodos-500 (Terrasa,Spain).</p><p>Amino acid composition was studied on an automatic amino acid analyzer T-339 («Mikrotechna», Prague, Czech Republic) by ion-exchange liquid chromatography at the laboratory of the Palladin Institute of biochemistry of the National Academy of Sciences of Ukraine.</p><p><strong>Results and discussion</strong></p><p>17 amino acids, including 7 essential (valine, isoleucine, leucine, lysine, methionine, threonine, phenylalanine), 2 conditionally essential (arginine and histidine) and 8 replaceable amino acids (alanine, aspartic acid, glycine, glutamic acid, proline, serine, tyrosine, cystine) were identified in <em>F. velutipes</em> biomass dry powders. Biomass dry powders obtained by different methods of microbiological synthesis (cultivation in static conditions and by submerged culture) do not differ in amino acids qualitative composition.</p><p>However, the biomass dry powder of medicinal mushroom that was obtained in static conditions contains 1.41 times more amino acids (essential to 1.27 times more; replaceable – 1.46 times more).</p><p><strong>Conclusions</strong></p><p>1. Using ion-exchange liquid chromatography in <em>F. velutipes</em> biomass dry powders were identified 17 amino acids, including 7 essential, 2 conditionally essential and 8 replaceable ones. Biomass dry powders were obtained by cultivation in static conditions and by submerged culture. The dominant of the essential amino acids in both investigated powders are leucine, of replaceable ones – glutamic and aspartic acid.</p>2. Cultivation of medicinal mushroom <em>F. velutipes</em> in static conditions allows to obtain in 1.41 times more amino acids compared to the submerged culture.

Distribution of Total Sulfur in Acidic, Basic, and Neutral Fractions on Brazilian Asphalt Cements and Its Relationship to the Aging Process

In this work, studies were performed in Brazilian asphaltic cements by separating fractions of maltenes and asphaltenes using nonaqueous ion exchange liquid chromatography (NIELC). Initially, three different aging processes (RTFOT, PAV, and SUNTEST) were applied to 23 different asphaltic cements for evaluating the changing of asphaltenic (12.7 ± 2.5%) and maltenic (90.6 ± 5.0%) compounds. The RTFOT+SUNTEST process was studied in a comparative way for 5 asphalt cements samples, since it caused the more pronounced changes in maltenes and asphaltenes among the asphaltic cements supplied by different Brazilian refineries. Asphaltenes presented the highest amount of polar compounds in all the studied samples, herein attributed to compounds of acidic and basic character that contain sulfur. It was also found that the aging of asphalt cement leads to an increase of the more reactive acidic (9.5–18.9%) and basic (14.6–30.9%) fraction in both asphaltenes and maltenes. As a result, a reactivity index (Ir) for asphaltic cements was calculated and proposed for classifying the studied samples regarding their aging susceptibility. It was also observed that the less reactive asphaltic cement presented the highest amount (>80%) of neutral sulfur compounds in maltenic fraction. Lastly, it was concluded that a higher content of total sulfur in asphalts does not imply necessarily in a higher chemical reactivity (susceptibility to aging) of the cement, as observed for 5 studied samples having total sulfur ranging from 1.8 to 3.4% (w/w). The presence of functional groups related to their specific heteroatoms, such as sulfur, suggest a possible way to explain a greater or lesser susceptibility of asphalts to aging.

液相イオン交換法によって調製したFe/ZSM-5によるNH3-SCR

液相イオン交換法によって調製したFe/ZSM-5によるNH3-SCR

Characterization and water adsorption properties of Ag- and Zn-exchanged A zeolites

Ag- and Zn-exchanged A zeolites are prepared by the liquid ion exchange method following the procedure reported in our previous studies. Samples with Ag and Zn metal loadings are obtained and characterized by physicochemical and thermal analyses. The obtained materials with improved physicochemical properties are promising candidates for use as haemostatic agents. Both powder X-ray diffraction and nitrogen adsorption measurements show good conservation of the zeolitic structure and texture after ionic exchange. Porosity measurements indicate that the variation of the porous volumes and the specific surface areas depends on the number and nature of exchanged cations. Thermal behavior of water adsorption studied by using TGA microbalance and differential scanning calorimetry highlights clearly the complexity of the adsorption and diffusion mechanisms of water molecules within the micropores of exchanged zeolites. The differences between sorption rates and hydration heats appear to be due mainly to the location and migration of Ag, Ca and Zn species in the cationic position of the A zeolite framework. The exothermicity of adsorption is attenuated by Ag and Zn exchange.

Research on Preparation and Stacking Performance of IPMC

In order to improve the performance of IPMC, a chemical deposition method was utilized to manufacture IPMC with silver electrodes (Ag-IPMC), and methods of ion exchange and ionic liquid penetration were adopted to conduct modified treatment for original IPMC. Additionally, the stacking performance of IPMC, which was disposed by ionic liquid penetration after the modified treatment, was analyzed. Results showed that: Ag-IPMC, which was modified by treating in 2mol/L LiCl solution for three hours, presented the optimal performance. Also, the IPMC after modified treatment by ionic liquid penetration swung longer in air, and its tip output displacement was stable at five millimeter; without any change with time. Furthermore, the stacked model of IPMC decreased the excursion of center in the process of swinging, and it also increased the output force of IPMC. The stacked model, which was composed with 3 sheets of IPMC after modifying treatment by ionic liquid penetration, was verified to have the optimal performance.

Isolation of Biogenic Amines Using Paramagnetic Microparticles Off-Line Coupled with Ion Exchange Liquid Chromatography

This study aims at the possibility of single structured paramagnetic microparticles (PMPs), composed of maghemite (γ-Fe2O3) core modified with chitosan called MAN8, or tetraethyl orthosilicate covered with Dowex called MAN35, to be helpful for isolation of biogenic amines prior to their further analysis. Primarily, we synthesized and characterized PMPs. To obtain the information about bead morphology, scanning electron microscopy was employed. Furthermore, X-ray fluorescence was employed to carry out the elemental composition analyses. To obtain further insight into interaction between PMP surface and biogenic amines, scanning electron microscope was employed. It was shown that binding of biogenic amines causes increase of relative current response of deprotonated microparticles. We tested the specificity of PMPs to bind biogenic amines on histamine, tyramine, spermine, spermidine, putrescine, and cadaverine. We found that two types of our PMPs were able to selectively bind spermidine, cadaverine, and histamine in the case of MAN35; and histamine, tyramine, and putrescine in the case of MAN8. Finally, we carried out the analyses of real samples obtained from patients suffering from prostate carcinoma, where histamine was determined as the most abundant biogenic amine (10.456–13.654 µg mL−1). The prepared PMPs were able to isolate the biogenic amines from real samples, and thus they may be helpful in construction of biosensors, or Lab-on-a-Chip platforms, enabling less painful, and more rapid diagnosis of prostate cancer.

Graphene/Ionic liquid composite films and ion exchange.

Wettability of graphene is adjusted by the formation of various ionic surfaces combining ionic liquid (IL) self-assembly with ion exchange. The functionalized ILs were designed and synthesized with the goal of obtaining adjustable wettability. The wettability of the graphene surface bearing various anions was measured systematically. The effect of solvent systems on ion exchange ratios on the graphene surface has also been investigated. Meanwhile, the mechanical properties of the graphene/IL composite films were investigated on a nanometer scale. The elasticity and adhesion behavior of the thin film was determined with respected to the indentation deformation by colloid probe nanoindentation method. The results indicate that anions played an important role in determining graphene/IL composite film properties. In addition, surface wetting and mechanics can be quantitatively determined according to the counter-anions on the surface. This study might suggest an alternate way for quantity detection of surface ions by surface force.

A new procedure based on column chromatography to purify bromelain by ion exchange plus gel filtration chromatographies

Bioproducts separation and purification processes are an important segment of the biotechnical industry. Bromelain is an enzyme which has great commercial value and is of wide interest in the pharmaceutical, alimentary, and textile industries, among others. The goal of this study was to develop a new method for bromelain purification from the stem residues resulting from agricultural processing of the pineapple plant. Bromelain was purified using two liquid chromatography steps, ion exchange plus gel filtration chromatography. Use of the methodology which was developed produced an enzyme with a molecular weight of 30kDa (confirmed by SDS-PAGE), high recovery of enzymatic activity (89%), and with a purification factor of 16.93, a result superior to the methodologies described in the literature. HPLC showed the presence of two peaks in the ion exchange chromatogram and only one protein in the gel filtration chromatogram. Results indicate that, depending on the destination of the bromelain, the process can be stopped after the first purification step. The MALDI-TOF MS provided the peptide mass fingerprint of bromelain and MALDI-MS/MS the fragmentation profile and sequencing of the ions of m/z 951 and 1584. Thus, the connectivity and chemical structure of bromelain was confirmed. Moreover, besides its superiority to other methodologies, it can be applied to take advantage of the agricultural and industrial pineapple plant residues.

A rapid method for the determination of free alpha-amino acids in pea (Pisum sativum) using ultra high performance liquid chromatography-high resolution accurate mass-mass spectrometry

The analysis of alpha-amino acids in biological matrices usually requires time-consuming ion exchange liquid chromatography with post column derivatisation.

구리 제올라이트와 철 제올라이트 촉매에 의한 질소산화물의 암모니아 선택적 촉매환원반응 특성

구리-제올라이트 촉매와 Fe-제올라이트 촉매로 과잉산소 분위기에서 일산화질소의 암모니아 선택적 촉매환원반응을 체계적으로 조사하였다. 촉매는 디젤엔진에서의 SCR기술의 적용을 위하여 구리와 철을 <TEX>$NH_4$</TEX>-BEA와 <TEX>$NH_4$</TEX>-ZSM-5 제올라이트에 이온교환법과 함침법으로 담지시켜 제조하였다. 촉매의 특성은 BET, XRD, FE-TEM과 SEM/EDS를 사용하여 조사하였다. 고정된 반응조건에서 선택적 촉매환원반응의 활성을 조사한 결과에서 구리를 BEA 제올라이트에 이온교환시켜 제조한 촉매가 <TEX>$200{\sim}250^{\circ}C$</TEX>의 저온영역에서 탁월한 성능을 나타내었다. <TEX>$250^{\circ}C$</TEX> 이하의 저온에서 구리-제올라이트 촉매가 Fe-제올라이트 촉매보다 높은 반응활성을 나타내었다. BEA 제올라이트에 담지된 촉매가 ZSM-5 제올라이트에 담지된 촉매보다 <TEX>$250^{\circ}C$</TEX> 이하의 저온에서 우수한 반응활성을 나타내었다. The <TEX>$NH_3$</TEX>-selective catalytic reduction (SCR) reaction of NO with excess of oxygen were systematically investigated over Cu-zeolite and Fe-zeolite catalysts. Cu-zeolite and Fe-zeolite catatysts to adapt the SCR technology for mobile diesel engines were prepared by liquid ion exchange and incipient wetness impregnation of <TEX>$NH_4$</TEX>-BEA and <TEX>$NH_4$</TEX>-ZSM-5 zeolites. The catalysts were characterized by BET, XRD, FE-TEM (field emission transmission electron microscopy) and SEM/EDS. The SCR examinations performed under stationary conditions showed that the Cu-exchanged BEA catalyst revealed pronounced performance at low temperatures of <TEX>$200{\sim}250^{\circ}C$</TEX>. With respect to the Fe-zeolite catalyst, the Cu-zeolite catalyst showed a higher activity in the SCR reaction at low temperatures below <TEX>$250^{\circ}C$</TEX>. BEA zeolite based catalyst exhibited good activity in comparison with ZSM-5 zeolite based catalyst at low temperatures below <TEX>$250^{\circ}C$</TEX>.

Ion exchange liquid chromatography method for the direct determination of small ribonucleic acids

Bioanalysis of siRNAs is challenging due to their size (5–14kDa) and negative charge across the backbone, which complicates both sample preparation and chromatography. We present here a one step sample preparation combined with non-denaturing anion exchange chromatography with UV detection for the quantitation of siRNA and its chain shortened metabolites. The sample preparation uses a novel lysis buffer with proteinase K to effectively isolate siRNA from cells and formulated media with greater than 95% recovery. The ion exchange chromatography allows for a lower limit of quantitation of 6ngmL−1 in cells and media equivalent to 6ng/200,000cells. This method is applied to study the uptake of siRNA in prostate cancer cells and the disappearance in the media and siRNA metabolism. siRNA metabolites are identified by matching the retention time of standards to metabolite peaks. Identification is further confirmed by mass spectrometry. To our knowledge this is the first ion exchange method reported for the quantitation of siRNA from a biological matrix. It is also the first non-denaturing chromatographic method reported for siRNA quantitation.