Determination of aluminum oxide in and on high-purity aluminum by a phenol dissolution method

A simple rapid determination of aluminum oxide in aluminum is described. Aluminum reacts with phenol at 180°C forming aluminum phenoxide but aluminum oxide does not. After the reaction, the aluminum oxide is filtered off and brought into aqueous solution by fusion with potassium hydrogensulfate for determination by atomic absorption spectrometry or by the 8-quinolinol spectrophotometric method. The reaction between aluminum and phenol is stoichiometric. The procedure is applicable to the determination of aluminum oxide in commercial aluminum metals of various forms. The method is relatively rapid and appears to be superior to the conventional bromine—methanol method.     

Stalagmometric titrations

End-point detection in some precipitation titrations is achieved by measurement of the surface tension between mercury and the solution ("stalagmometric" titration). The drop-time of a polarographic dropping mercury electrode in open circuit is plotted against volume of surface-active titrant added, and shows a break or a peak at the end-point. The stalagmometric titration of sodium tetraphenylborate with Zephiramine (tetradecyldimethylbenzylammonium chloride) was satisfactory and made possible the determination of potassium by back-titration. Potassium was also titrated directly with tetraphenylborate and with calcium dipicrylaminate. Sodium dodecylbenzenesulphonate was titrated directly with Zephiramine and the results were compared with those obtained by the p-toluidine method and Epton's method.     

Flow-injection determination of L-histidine with an immobilized histidine oxidase from Brevibacillus borstelensis KAIT-B-022 and chemiluminescence detection.

A chemiluminometric flow injection analytical system for the quantitation of L-histidine is described. Histidine oxidase (EC 1.4.3.-) from Brevibacillus borstelensis KAIT-B-022 was immobilized on tresylated poly(vinyl alcohol) beads and packed into a stainless-steel column. The hydrogen peroxide produced was detected chemiluminometrically by a flowthrough sensor containing immobilized peroxidase (EC 1.1 1.1.7). The maximum sample throughput was 10 h(-1). The calibration graph was linear from 0.05 to 5 mM; the detection limit (signal to noise ratio = 3) was 0.01 mM. The activity of immobilized histidine oxidase reduced to 65% of the initial value after 350 injections. The system was applied to the determination of L-histidine in fish meat, such as salmon, tunny, bonito, and mackerel.     

Measurements of Room-Temperature Phosphorescence Spectra of Polycyclic Aromatic Compounds Using Pullulan Films Containing β-Cyclodextrin and 2-Bromoethanol

A clear film was easily prepared by air-drying anaqueous solution of pullulan (6%w/w) containing -cyclodextrin(CD, 1%w/w) and 2-bromoethanol (1%v/w). The resultingpullulan film was used as a substrate for simple measurements ofroom-temperature phosphorescence (RTP) spectra of polycyclicaromatic compounds (PACs). Only a drop (ca. 10 L) of a 100 gmL^-1 sample solution in 95% ethanol was spotted onto the surfaceof the disk film (7–8 mm diameter) and the solvent wasallowed to evaporate at room temperature. The sample-spottedfilm was pasted on a glass plate (75 × 20 × 1 mm) with smallamounts of a starch glue. The plate was mounted into a solidsample holder, or alternatively inserted diagonally into a 1-cm cell holder.Without a dry gas flush during the measurements, RTPspectra based on the CD inclusion complexes of PACs wereobtained from six typical two- and three-ring compounds,including naphthalene, acenaphthene, fluorene, phenanthrene,carbazole, and dibenzofuran. Only anthracene did notproduce a discernable phosphorescence signal by the presenttechnique. This technique was directly applied to the spectralidentification of acenaphthene in commercially available kerosene.     

Flow-through chemiluminescence sensor using immobilized oxidases for the selective determination of L-glutamate in a flow-injection system.

A selective and sensitive chemiluminometric flow sensor for the determination of L-glutamate in serum, based on immobilized oxidases such as glutamate oxidase (GOD), uricase (UC) and peroxidase (POD), is described herein. The principle for the selective chemiluminometric detection for L-glutamate is based on coupled reactions of four sequentially aligned immobilized oxidases, UC/POD/GOD/POD in a flow cell. The immobilized UC was employed to decompose urate, which is one of the major interfering components in serum for a luminol-H2O2 chemiluminescence reaction. The H2O2 produced from the UC reaction readily reacted with reducing components, such as ascorbate and glutathione, and then the excess H2O2 was decomposed by the immobilized POD. L-Glutamate in the sample plug was enzymatically converted to H2O2 with immobilized GOD. Subsequently, the peroxide reacts with luminol on the immobilized POD to produce chemiluminescence, proportional to glutamate concentration. The enzymes were immobilized on tresylated poly(vinyl alcohol beads). The immobilized enzymes were packed into TPFE tube (1.0 mm i.d. x 60 cm), in turn, and used as a flow cell. The sampling rate was 30 h-1. The calibration graph for L-glutamate is linear for 20 nM-5 microM; the detection limit (signal-to-noise = 3) is 10 nM.     

Parameters of ultrasonic dispersion of polymer-composite solutions

Conditions allowing the formation of three types of characteristic cavities in liquid via ultrasonic cavitations have been considered. The effect of the ultrasonic-field parameters on the dispersion efficiency has been analyzed, and the choice of criteria for the evaluation of the quality of steering and dispersion of a polymer-composite material (PCM) for reconstruction of body parts of automotive engineering has been grounded. The conditions for effective dispersion of a PCM solution have been established on the basis of the sound-pressure amplitude upon ultrasonic treatment and based on the maximum permissible level of the solution in an ultrasonic bath.