Μm Silica Particles Research Articles

High-Performance Liquid Chromatographic and Derivative Ultraviolet Spectrophotometric Determination of Pindolol and Clopamide Mixture in Tablets

Abstract Two rapid assay procedures based on high performance liquid chromatography (HPLC) and derivative ultraviolet (UV) spectrophotometry have been developed for the simultaneous determination of pindolol and clopamide in two component tablets. An HPLC assay with RP-18 column, of 250 × 4.6 mm ID as dimension and 10 μm silica particles, was used. The mobile phase consisted of water-methanol-acetonitrile (50–45–5) with pH of 3 and a flow rate of 1.5 ml min−1. Detection was at 264 nm with a band width of 10 nm. The derivative spectrophotometric procedure depends on the measurements of 2D amplitude in methanol at 264 nm for pindolol and ▴1D amplitude of the delta absorption spectra (methanolic HCl -methanolic NaOH) at 249 nm for clopamide. For HPLC procedure the calibration graphs were linear in the ranges of 10–20 and 5–10 μg ml−1 for pindolol and clopamide, respectively. For the derivative method, they were linear in the ranges of 10–26 and 10–20 μg ml−1 for pindolol and clopamide, respectively. The cali...

A fluidized-bed sampler for direct powder introduction inductively coupled plasma atomic emission spectrometry: particle size segregation

The determination of trace elements in powdered solids with direct powder introduction ICP-AES and ICP-MS is subject to errors associated with particle-size if (a) the powder sampler hardware introduces bias in the particle size distribution during the sample transport, or (b) if the efficiency of the processes leading to emission of analytes in the plasma is a function of particle size. The magnitude of particle size-segregation which is caused by a fluidized-bed powder sampler was estimated with two simple fluid dynamic models of powder collection: the first based upon the relative forces of gravity and the viscous drag on particles moving through a gas, and the second based upon the relative effects of particle inertia and the force of viscous drag on the particles. Experimental measurement of size-segregation was based on a series of 13 synthetic binary mixtures of 21 ± 6 (±1 SD) and 34 ± 10 μm silica particles ranging in composition from 1 to 99% by weight of the smaller particle, the balance made up of the larger particle. The smaller particle was labelled with Mn and Co via complexation with immobilized 8-hydroxyquinoline, and the larger was labelled with Cu and Cd. Mixtures of the particles were analyzed by add extraction of these labels, followed by conventional liquid nebulization ICP-AES. The composition of the particle mixture after passage through the sampler was related to the original mixture by ( y a / y b ) = 1.96 ( x a / x b ) where y a , and y b are the fractions by weight of 21 and 34 μm particles after, and x a and x b are the fractions before, transport through the sampler. A mixture which was 1:1 by weight of these particles prior to transport, contained about 65% small and 35% large particles (by weight) after passage through the fluidized-bed sampler. Hardware designs which minimize the particle size-segregation should include mechanical provision for continuous formation of an aerosol of sample in the vicinity of the uptake capillary.

亜鉛めっきした高張力鋼の水素脆化挙動及びシリカ共析の影響

The hydrogen embrittlement of 145kgf/mm2-class high strength steel was evaluated, with the concomitant measurement of hydrogen absorbed during pretreatment and zinc plating of the steel using zincate bath with or without suspended silica particles. It was found that almost all of the absorbed hydrogen was located in the plated zinc layer and at the zinc/steel boundary layer of a thickness of less than 100μm. During a series of tensile tests conducted using a notched tensile test piece at strain rates of from 4.2×10-5 to 4.2×10-3sec-1, a clear relationship was established between hydrogen content and tensile strength. Thus it was concluded that the tensile test can be used as a quick method of evaluating hydrogen embrittlement. When 0.018μm silica particles were codeposited with zinc in an amount of only 0.2wt%, the notch-tensile strength as well as elongation were much greater than with plain zinc coated steel. This effect may be ascribed to the dispersed particles lowering the diffusion barrier height for hydrogen diffusion.

Determinations of catechols in small volumes of plasma using ion-pair reversed phase liquid chromatography/electrochemistry

A method with improved sensitivity for detection of catechols (CA) in small volumes of plasma using an ion-pair reversed phase HPLC system with electrochemical detection is presented. Fast isocratic separations were obtained by using 7.5 cm × 4.6 mm (i.d.) reversed phase columns with 3C 18 3 μm silica particles. The CA: s L-DOPA, Noradrenaline (NA), Adrenaline (A), Dihydroxybenzylamine (DHBA, i.s.), DOPAC and Dopamine (DA) were separated in less than 4 min. The performance of three different electrochemical cells was compared with respect to hydrodynamic voltammogram, band broadening effect, linearity and detection limit. The sample preparation procedure using alumina extraction of CA: s, was modified to improve recoveries and decrease dilution factors. A modified carbon paste cell (CP-O) gave a response 4–8 times higher than what is previously reported for GC cells. Detection limits were: L-DOPA 80, NA 1.25, A 1.25, DHBA 0.4, DOPAC 1.25 and DA 0.6 pg/injection. Application to plasma from rat and fish (cod) under rest, exercise and stress is reported. The method allows determination of CA: s in small volumes of plasma (<500 μl) obtained several times a day from the same animal even if it is small (< 1 2 kg) , is under rest and parts of the plasma sample are to be used for analysis of other parameters than CA: s.

Steric stabilization of St�ber silica dispersions using organosilanes

Organosilanes of the general formula RxSi(OR′)4−x (where R is an alkyl group and R′ = CH3 or CH2CH3) were used to sterically stabilize hexane dispersions of submicrometre silica spheres. The dispersions were characterized according to sediment volume results. For 0.5μm silica particles, the sediment density increased by more than a factor of three up to 50 to 55% of theoretical in the presence of organosilanes with 12 or more carbons in the R group. Solid-state13C nuclear magnetic resonance was used to characterize the powder-dispersant interaction; this technique can distinguish between carbons in the R group of the organosilane and residual organic groups in the silica. Scanning electron micrographs of filter compacts were used to further characterize the dispersions and indicated the presence of primary particles as well as small agglomerates.

シランカップリング処理した亜鉛‐シリカ複合めっき皮膜の耐食性

The effect of treatment with γ-aminopropyltriethoxy silane (γ-APS) on the corrosion resistance of zinc-silica composite which was electroplated onto mild steel substrate has been studied by salt spray testing, measurement of spontaneous electrode potential in concert with contact angle to water, and FT-IR spectroscopy. Composite surface roughness was regulated with the aid of surfactants in the bath. The red rusting time of non γ-APS treated composite containing 3.6wt% of 0.018μm silica particles was found to be 1200hr, which corresponds to about twelve times the salt spray resistance of the pure and fan-shaped zinc electroplate of the same mean thickness. A red rusting time of 2800hr was recorded when the same sample was treated with γ-APS solution. Spontaneous electrode potential measurement of the nontreated composite showed that a protective film is formed on the composite surface in 5% NaCl solution. The excellent red rusting resistance of the treated composite is ascribed to formation of a chemically fixed hydrophobic layer on the composite surface.

Packing procedure of silica columns for HPLC with aqueous slurries

AbstractSuccessful packing of high quality HPLC columns is dependent upon a number of parameters. Especially when using slurry packing techniques, the absence of conglomerates of particles in the slurry and the wettability of the particles are important. The method described in this paper fulfills these conditions, imparting a ξ potential to the 5 and 10 μm silica particles by applying a pH gradient. This results in repulsive forces between the particles and hence leads to a well‐controlled monodisperse situation. Water is used as a slurry and displacement liquid; it combines the advantages of excellent wetting properties and non‐toxicity.