Open tubular anion exchange chromatography. Controlled layered architecture of stationary phase by successive condensation polymerization

The preparation and performance of a multilayered stationary phase for open tubular anion exchange chromatography in relatively large bore (75 microm diameter) columns are described. The inner surface of a fused-silica capillary tube is coated with up to 25 successive porous polymeric layers formed by condensation polymerization of a primary amine with a diepoxide. Each layer of the anion exchange stationary phase consists of copolymer of methylamine (MA) and 1,4-butanedioldiglycidyl ether (BDDE). The polymer layers are sufficiently porous or permeable; each successive layer of the stationary phase incrementally increases the observed column capacity and chromatographic performance in the open tubular mode. Even though the column inner diameter is far from optimum for open tubular liquid chromatography, we demonstrate the baseline separation of a suite of inorganic anions (F-, Cl-, NO2-, Br-, NO3-) in a 5 m x 75 microm column coated with 25 layers of the anion exchange polymer using 1 mM KOH eluent and suppressed contactless conductometric detection at a flow rate of 1 microL/min (operating pressure of approximately 1 bar) with a plate count of >30,000. Strategies for construction of microsuppressor devices used in open tubular ion chromatography are discussed.     

Dietary effect of gamma-linolenic acid on the lipid profile of rat fed erucic acid rich oil

This study evaluated the effects of dietary supplementation of gamma-Linolenic acid (18:3n-6, GLA) on the lipid profile of serum and other tissues of rats fed erucic acid (C22:1) rich oil like mustard oil. The rats were fed diet containing 20% mustard oil as erucic acid rich oil and 20% groundnut oil as dietary fat. These groups were kept as reference groups. Another group fed diet containing 20% fat to which evening primrose oil as a source of GLA was blended with mustard oil and groundnut oil at 5% level. The feeding experiment was done for 4 weeks. In another set mustard oil fed group was kept as control while the experimental group was fed evening primrose oil as a source of GLA blended with mustard oil at 2.5% level. The feeding experiment was carried out for 12 weeks. The other dietary components remained same for all the groups. After the scheduled feeding period, it was found that there was no significant change in weight gain, food intake and food efficiency ratio. It was found that dietary GLA resulted in significant decrease in serum triglyceride (TG) and very low density lipoprotein (VLDL) cholesterol and significant increase in high density lipoprotein (HDL) cholesterol in serum in the experimental group. In liver total cholesterol (TC) is significantly higher and in heart and liver TG is significantly lower in GLA fed group.     

Influence of material characteristics on the abrasive wear response of some hardfacing alloys

This study examines the abrasive wear behavior of two iron-base hardfacing materials with different combinations of carbon and chromium after deposition on a steel substrate. Effects of applied load and sliding distance on the wear behavior of the specimens were studied. Operating material removal mechanisms also were analyzed through the scanning electron microscopy (SEM) examination of typical wear surfaces, subsurface regions, and debris particles. The results suggest a significant improvement in the wear resistance of the hardfaced layers over that of the substrate. Further, the specimens overlaid with the material with low carbon and high chromium contents attained better wear resistance than the one consisting of more carbon but less chromium. The former specimens also attained superior hardness. Smoother abrasion grooves on the wear surfaces and finer debris formation during the abrasion of the hardfaced samples were consistent with wear resistance superior to that of the substrate.     

Effect of experimental parameters on the high-stress abrasive wear behavior of steels and a software package for its prediction

The effect of different experimental factors on the high-stress abrasive wear properties of steels has been studied. A correlation among the factors has been established by linear regression analysis. A computer software in Microsoft Basic language utilizing linear regression analysis has been developed with the capability of predicting the wear response of steels from the experimental factors.     

‘SMART’ ELECTRONIC SYSTEMS FOR CONDITION-BASED HEALTH MANAGEMENT

Condition-based health management of electronic systems involves monitoring the system condition using real-time, in-situ sensing techniques and taking appropriate maintenance actions based on the physics-of-failure (PoF) interpretation of the collected data. This paper discusses the applicability of monitoring condition degradation in printed wiring assemblies (PWA) due to potential wearout failure mechanisms. Techniques are provided to assess the remaining life. © 1997 by John Wiley & Sons, Ltd.     

Mineral element composition of spinach

An extensive study has been made on the mineral element compositions of spinach leaves and stems. Twenty two locally grown different spinach samples have been analysed for 16 elements using ICP and atomic absorption spectrophotometric techniques. Both spinach leaves and stems were analysed separately. A detailed elucidation of the inorganic matrix in spinach leaves and stems has been provided. © 1998 SCI.     

Versatile gas/particle ion chromatograph

A new, compact gas/particle ion chromatograph has been developed for measuring ionic constituents in PM2.5 (particulate matter of aerodynamic diameter < or = 2.5 microm) and water-soluble ionogenic gases. The instrument has separate sampling channels for gases and particles. In one, a membrane denuder collects soluble gases for preconcentration and analysis. In the other, a cyclone removes larger particles, a membrane denuder removes soluble gases, and a continuously wetted hydrophilic filter collects particles. A single, multiport, syringe pump handles liquid transport, and one conductivity detector measures anions and ammonium for both channels. Electrodialytically generated gradient hydroxide eluent permits 20 min chromatographic runs. Gas/particle samples are each collected for 40 min, butthe sampling intervals are staggered by 20 min. Liquid samples from the gas denuder and particle collector are aspirated and preconcentrated on sequential cation and anion concentrators and transferred respectively to an ammonia transfer device and an anion separation column. The flow configuration results in an ammonium peak before anion peaks in the chromatogram. The system measures ammonia, organic acids (such as acetic, formic, and oxalic acids), HCl, HONO, SO2, HNO3, and the corresponding ions in the aerosol phase. Low ng/m3 to sub-ng/m3 limits of detection (LODs) are attained for most common gases and particulate constituents, the LODs for gaseous SO2 to NH3 range, for example, from sub parts per trillion by volume (sub-pptv) to approximately 5 pptv.     

Black box linearization for greater linear dynamic range: the effect of power transforms on the representation of data

Power transformations are commonly used in image processing techniques to manipulate image contrast. Many analytical results, including chromatograms, are essentially presented as images, often to convey qualitative information. Power transformations have remarkable effects on the appearance of the image, in chromatography, for example, increasing apparent resolution between peaks by the factor √n and apparent column efficiency (plate counts) by a factor of n for an nth-power transform. The profile of a Gaussian peak is not qualitatively changed, but the peak becomes narrower, whereas for an exponentially tailing peak, asymmetry at the 10% peak height level changes markedly. Using several examples we show that power transforms also increase signal-to-noise ratio and make it easier to discern an event of detection. However, they may not improve the limit of detection. Power responses are intrinsic to some detection schemes, and in others they are imbedded in instrument firmware to increase apparent linear range that the casual user may not be aware of. The consequences are demonstrated and discussed.