Fourth Order Derivative Spectrophotometric Determination of Benzyl Alcohol in Piroxicam Injections

Piroxicam is a drug with analgesic and anti‐inflammatory properties. It is present in numerous pharmaceutical preparations. Injectable forms usually contain benzyl alcohol as an excipient, which is used as a blocking anesthetic (4%) and an antiseptic (4–10%). In this work, spectrophotometric methodology was used in order to determine benzyl alcohol in piroxicam injectable formulations by applying the fourth derivative method adopting the zero‐crossing technique. The results obtained show that the method has significant advantages over other reported methods and is appropriate for routine pharmaceutical analysis. The method showed excellent linearity in the range of 2–100 μg mL^?1 with limit of detection (S/N = 3) 0.07 μg mL^?1 (6.47 × 10^?7 M). The proposed method could be applied successfully for the determination of benzyl alcohol in injectable formulations with average % recovery of 100 ± 0.61.     

Plastic membrane electrodes for amprolium

The construction and general performance characteristics of two PVC membrane sensors responsive to the amprolium (AmpH²⁺) cation are described. These sensors are based on the ion-associates amprolium-tetraphenylborate (AmpH-TPB) and amprolium-reineckate (AmpH-Rk). The electrodes exhibit near-Nernstian response for the doubly charged amprolium cation over the concentration ranges 0.1–100 and 0.01–100 mM for AmpH-TPB and AmpH-Rk, respectively. The pH does not affect electrode performance within the range 7.0–11.0. No interferences are caused by many inorganic cations, sugars and amino acids. The isothermal coefficients are found to be 0.0001306 and 0.0010438 V/ °C for AmpH-TPB and AmpH-Rk, respectively. Potentiometric titration and standard addition methods were used to determine amprolium in pure solutions and in veterinary soluble powder, with high accuracy and precision.     

Numerical simulation of particulate-flow in spiral separators: Part I. Low solids concentration (0.3% & 3% solids)

The aim of the present study is the simulation of the particulate flow in spiral separators. The study is based on Eulerian approach and turbulence modeling. The results focus on particulate-flow characteristics such as the velocity, the distribution, and concentration of particulates on the spiral trough. The predicted results are compared with the experimental findings from LD9 coal spiral. The comparison shows good agreement and indicates that the most accurate turbulence model is RNG K–ε.     

流体力学半径对估算胶体微球聚集速率常数的影响

胶体粒子聚集速率常数实验值远低于理论值一直是被普遍关注的问题.聚集速率常数的理论推导是基于粒子的几何半径来考虑的,但决定粒子扩散速率及聚集速率的应该是粒子的流体力学半径(大于几何半径),因而它是使聚集速率常数实验值低于理论值的因素之一.影响流体力学半径的因素很多,其中,带电粒子在溶液中因表面存在双电层,会明显增大流体力学半径,造成聚集速率减慢.而双电层的厚度又随溶液中离子强度的不同而改变.本工作在聚集速率的公式中引入了修正因子,即几何半径与其流体力学半径之比,以修正由于用几何半径代替流体力学半径带来的误差.其中几何半径和流体力学半径可以分别用扫描电镜(SEM)和动态光散射(DLS)来测定.以两种粒径的聚苯乙烯带电微球为例,考察了在不同离子强度下,该误差的大小.结果发现,对于半径为30 nm的微球,用流体力学半径计算的慢聚集速率常数比理论值偏低约8%.该误差随离子强度增加而减少.对于快聚集情况,流体力学半径对聚集速率基本没有影响.     

Effect of electron repelling and electron attracting groups on the optical activation energy and the dipole moment of some ethylenes and butadienes

The optical activation energy and the dipole moment of some ethylenes and butadienes have been examined. The possible effect of attaching electron repelling or electron attracting groups either to one end of the molecule (as in the case of ethylenes) or to both opposite ends of the molecule (as in the case of butadienes) have been investigated.In case of ethylenes, it has been found that the transmission maxima lie at 440 mu. Also, the transmission maxima of the butadienes lie close to 865 mu. A linear relationship has been observed between the measured value of the dipole moment and log ₀ for these materials which were previously determined by the authors [1, 2].The authors would like to express their sincere gratitude to Prof. Dr. K.Vacek, head of the department of chemical physics, Charles University for his encouragement, continuous interest and for his invaluable help and comments to conduct this work.     

Spectrophotometric Determination of Thioctic Acid in its Dosage Forms through Complex Formation with Pd(II)

A simple and sensitive spectrophotometric method has been developed for the determination of thioctic acid in pharmaceutical preparations. The proposed method is based upon the formation of a complex with palladium(II) in acetate buffer of pH 4.8 with an absorption maximum at 318 nm. The absorbance obeyed Beer's law over the range of 2–20 μg mL^?1 with a minimum detection limit of 0.15 μg mL^?1 and molar absorptivity (ζ) of 7 × 10³ L mol^?1.cm^?1. The different experimental parameters affecting the development and stability of the color were carefully studied and optimized. The proposed method was successfully applied to the analysis of commercial tablets and ampoules. The results obtained were in good agreement with those obtained using a reference spectrophotometric method. A proposal of the reaction pathway is presented.     

Extraction-spectrophotometric determination of amprolium hydrochloride using bromocresol green, bromophenol blue and bromothymol blue

A new procedure for the determination of amprolium hydrochloride by reaction with bromocresol green (BCG), bromophenol blue (BPB) and bromothymol blue (BTB) has been developed. The method consists of extracting the yellow ion-pair formed into chloroform from aqueous medium. The ion-pairs have absorption maxima at 420, 410 and 415 nm with molar absorptivities of 3.64 × 10⁴, 3.12 × 10⁴ and 2.31 × 10⁴1 mol^–1 cm^–1 for BCG, BPB and BTB, respectively. The method obeys Beer's law over the concentration ranges 0.6–12.0, 0.12–8.8 and 1.2–11.3 ag/ml amprolium hydrochloride for BCG, BPB and BTB, respectively. The method is simple, precise (relative standard deviation 0.665–2.210%), accurate (recovery 97.8–100.8%) and easily applied for pharmaceutical quality assurance for amprolium hydrochloride in raw materials and in formulated veterinary soluble powder.     

On-line nuclear ash gauge for coal based on gamma-ray transmission techniques

Developments and applications of on-line nuclear gauges in the coal industry are highly requested. In this work, a nuclear ash gauge for coal, based on γ-ray transmission techniques is developed. Single and dual energy γ-ray beams are used to determine the ash content of coal. The percentage ash content as a function of the γ-ray intensities transmitted through coal samples is measured and sensitivity curves are obtained. An empirical formulation relating the ash content values to the γ-ray intensities is derived. Preliminary results show that both single and dual energy γ-ray transmission techniques can be used to give a rapid on-line estimation of the ash concentration values in coal with low cost and reasonable accuracy, but the dual one is much preferable.     

Light-induced defects in plasma-hydrogenated InP: Zn

PhotoLuminescence (PL) measurements are used to investigate the effects of a H₂ plasma treatment in heavily doped p-type InP: Zn. Beside the large decrease in free hole concentration in the hydrogenated samples, a new Broad Luminescence Band (BLB) centered at about 1.32 eV appears upon laser irradiation during PL experiments above 50 K, and saturates for large values of the fight intensities. It is inferred that the plasma treatment produces some kind of non-radiative defects which can then rearrange into new BLB centers under illumination provided it is applied above a threshold temperature (50K). This mechanism is interpreted in terms of Recombination-Enhanced Defect Reaction (REDR) involving the two kinds of photogenerated carriers and appears to be low thermally assisted. The BLB is associated with the radiative emission at a phosphorus vacancy (V_p) close to a Zn acceptor (V _p ⁺ Zn _In ^– ). It is believed that the formation of BLB centers originates from V_p-related defects initially present in the freshly plasma-treated InP sample. The mechanisms involved in the Light-Induced Creation (LIC) of BLB centers are discussed.