Simple Analytical Model Predicting Some Features of the Electrolytic Steel-Pickling Process

Electrolytic pickling of steel with neutral solutions, to remove the surface scale, reduces the need for the use of strong acids as needed in conventional pickling. This study is a step towards a more in-depth understanding of the factors affecting the former process. A theoretical model, sufficiently simplified to allow analytical solution, is developed and evaluated to provide a first approximation of the potential and current distributions in the electrolyte and steel band. To gain knowledge and validate the model, a small electrolytic pickling cell is constructed, and experiments, including bubble generation and motion observation, are conducted. The experimental work has shown the remarkable bubble production and adherence to the surfaces, and its effects on reducing pickling efficiency and uniformity. The pickling efficiency is about 30%, confirming other researchers" results. The analytical model shows trends very similar to those observed in the experiments, and provides very valuable guidance. It shows, for example, that the current efficiency decreases as the electrode–band distance increases, and it increases with the band thickness and the band-to-electrolyte conductivity ratio. The energy efficiency decreases by orders of magnitude faster than the current efficiency with all of the above-mentioned parameters, because of the correspondingly strong drop in the band–surface potential. A large amount of current is lost due to interelectrode short circuiting.     

Analysis of urban dust (PM<Subscript>2</Subscript>/PM<Subscript>10-2</Subscript>) in Daejeon city by instrumental neutron activation analysis

Summary As part of an air pollution monitoring study, airborne particulate matter (PM₂/PM_10-2) samples were collected from 2000 to 2003 at two sampling sites in an urban region, Daejeon, the middle of Korea. Mass concentrations of both fine and coarse fractions and that of the black carbon in the fine particles were measured using the Gent stacked filter unit sampler and the smoke stain reflectometer, respectively. In the collected samples the concentrations of 24 elements were analyzed using instrumental neutron activation analysis. Monitored data were investigated for their temporal trends under different environmental conditions and their seasonal correlation patterns. Crustal enrichment factors were also estimated to establish the contribution between anthropogenic and crustal origin. Patterns for airborne particle matter (APM) and elemental concentrations, seasonal variation of some marker elements were investigated. The results can be applied for the investigation of further air pollution sources and for the evaluation of air quality.     

Airborne particulates (PM2.5/PM10) monitoring in Korea by instrumental neutron activation analysis

Instrumental neutron activation analysis was used for the analysis of 25 trace elements in airborne particulate matter (PM) for air pollution monitoring. For the collection of air samples, the Gent stacked filter unit low volume sampler and two types of Nuclepore polycarbonate filters were employed. Samples were collected at selected sampling dates in suburban and industrial regions of Daejon city in the Republic of Korea. Mass concentrations and black carbon of PM were measured, and enrichment factors were calculated. The results were used to describe the emission sources and their correlation patterns.     

Rapid analysis of dosage forms of some pharmaceuticals by nonaqueous thermometric titrimetry

The use of the technique of solution thermochemistry is proposed for the rapid assay for quality control and quality assurance of dosage amounts of some ethical formulations of some antimalarial drugs. The active ingredients are chloroquine, hydroxychloroquine, dapsone, proguanil hydrochloride, and pyrimethamine.Assay is done without the separation of the excipients and without isolation or derivatisation of the analytes. The titrations are done in glacial acetic acid and utilise the catalysed hydrolysis of acetic anhydride by perchloric acid to indicate the endpoint of the reactions.The time taken for a typical assay, of a typical dosage amount is about 3–5 minutes. The reproducibility is of the order of 1% for the milligramme amounts of analyte present in the dosage amounts of the drugs.

---

Zusammenfassung Es wird die Anwendung eines lösungsthermochemischen Verfahrens zu Schnellbestimmungen bei der Qualitätskontrolle und — sicherung von Wirkstoffeinsatzmengen einiger rezeptpflichtiger Präparate von einigen antimalarischen Arzneimitteln empfohlen. Die aktiven Bestandteile sind Chloroquin, Hydroxychloroquin, Dapson, Proguanilhydrochlorid und Pyrimethamin.Die Bestimmungen werden ohne jegliche Abtrennung der Bindestoffe und ohne Isolierung oder Derivatisierung der zu bestimmenden Substanzen durchgeführt. Die Titrierungen werden in Eisessig durchgeführt und bedienen sich der katalytischen Hydrolyse von Essigsäureanhydrid durch Perchlorsäure als Endpunktindikation der Reaktion.Die Dauer für eine typische Probe bei einer typischen Wirkstoffmenge beträgt etwa 3–5 Minuten. Die Reproduzierbarkeit liegt in der Größenordnung von 1% für Milligrammengen der zu analysierenden Stoffe im Arzneimittel.

---

. , , , . - . . 3–5 . 1% , .

---

---

We acknowledge the Nigerian Government for the provision of a grant to one of us (S.I.A.). We acknowledge the following for the gifts of samples of the authentic drugs and the tablets assayed in this work: Imperial Chemical Industries plc; May and Baker plc; Winthrop Laboratories plc; Wellcome Foundation (Medical Division).     

Simultaneous measurement of glucose and glutamine in aqueous solutions by near infrared spectroscopy

A method is described for measuring the concentrations of both glucose and glutamine in binary mixtures from near infrared (NIR) absorption spectra. Spectra are collected over the range from 5000–4000/cm (2.0–2.5μm) with a 1-mm optical path length. Glucose absorbance features at 4710, 4400, and 4300/cm and glutamine features at 4700, 4580, and 4390/cm provide the analytical information required for the measurement. Multivariate calibration models are generated by using partial least squares (PLS) regression alone and PLS regression combined with a preprocessing digital Fourier filtering step. The ideal number of PLS factors and spectral range are identified separately for each analyte. In addition, the optimum Fourier filter parameters are established for both compounds. The best overall analytical performance is obtained by combining Fourier filtering and PLS regression. Glucose measurements are established over the concentration range from 1.66–59.91 mM, with a standard error of prediction (SEP) of 0.32 mM and a mean percent error of 1.84%. Glutamine can be measured over the concentration range from 1.10–30.65 mM with a SEP of 0.75 mM and a mean percent error of 6.67%. These results demonstrate the analytical utility of NIR spectroscopy for monitoring glucose and glutamine levels in mammalian and insect cell cultures.     

A novel photoinduced ring opening and isomerization of adamantane-2-spiro isoxazolines using Mo(CO)6

The Mo(CO)₆-mediated photoinduced ring-opening reactions of adamantane isoxazolines involve novel rearrangement that provide enaminoketones as major products and β-hydroxy ketones as minor ones; in contrast, only β-hydroxy ketones and α,β-unsaturated ketones were obtained under thermal condition.     

Direct determination of estriol 3- and 16-glucuronides in pregnancy urine by column-switching liquid chromatography with electrospray tandem mass spectrometry

Using column-switching liquid chromatography/tandem mass spectrometry (LC-MS/MS), we developed an improved analytical method of urinary estriol glucuronides. This new method is derived predominantly from maternal and fetal precursors in pregnancy. We used in the following procedure: first, we filtered urine samples with a membrane filter. Next, we directly injected the 50 microL aliquot of urine samples onto a pre-column. Then, after activating the column-switching valve, we backflushed the loaded samples onto the C(18) analytical column. Urine samples can be assayed within 20 min without any sample preparation steps. We monitored separated estriol glucuronides by negative electrospray ionization (ESI) and selected-reaction monitoring (SRM). The calibration range of estriol-3-glucuronide (E3-3G) and estriol-16-glucuronide (E3-16G) was 0.1-20 microg/mL and the linearity of the method was 0.9984 for E3-3G and 0.9987 for E3-16G. The limits of detection at a signal-to-noise (S/N) ratio of 3 were 10 ng/mL (E3-3G) and 5 ng/mL (E3-16G). The analytical recovery was over 85% and, in general, inter-day and intra-day variability for precision and accuracy were less than 10%. When applied to a pregnancy urine sample to biomedical monitoring of the function of the maternal/fetal unit, the proposed method allowed rapid and sensitive screening for the detection of E3-3G and E3-16G.     

A new thermoelectric material: CsBi4Te6

The highly anisotropic material CsBi(4)Te(6) was prepared by the reaction of Cs/Bi(2)Te(3) around 600 degrees C. The compound crystallizes in the monoclinic space group C2/m with a = 51.9205(8) A, b = 4.4025(1) A, c = 14.5118(3) A, beta = 101.480(1) degrees, V = 3250.75(11) A(3), and Z = 8. The final R values are R(1) = 0.0585 and wR(2) = 0.1127 for all data. The compound has a 2-D structure composed of NaCl-type [Bi(4)Te(6)] anionic layers and Cs(+) ions residing between the layers. The [Bi(4)Te(6)] layers are interconnected by Bi-Bi bonds at a distance of 3.2383(10) A. This material is a narrow gap semiconductor. Optimization studies on the thermoelectric properties with a variety of doping agents show that the electrical properties of CsBi(4)Te(6) can be tuned to yield an optimized thermoelectric material which is promising for low-temperature applications. SbI(3) doping resulted in p-type behavior and a maximum power factor of 51.5 microW/cm.K(2) at 184 K and the corresponding ZT of 0.82 at 225 K. The highest power factor of 59.8 microW/cm.K(2) at 151 K was obtained from 0.06% Sb-doped material. We report here the synthesis, physicochemical properties, doping characteristics, charge-transport properties, and thermal conductivity. Also presented are studies on n-type CsBi(4)Te(6) and comparisons to those of p-type.