An improved method for nonbonded list generation: rapid determination of near-neighbor pairs

Generation of the list of near-neighbor pairs of atoms not bonded to each other is a key feature of many programs for calculating the energy and energy derivatives for large molecules. Because this step can take a significant amount of CPU time, more efficient nonbonded list generation can speed up the energy calculations. In this article, a novel nonbonded list generation algorithm, BYCC, is introduced. It combines certain features of other algorithms and achieves more rapid nonbonded list generation; a factor of approximately 2.5 for a molecule of 5000 atoms with a cutoff in the 10 A range is obtained on Hewlett-Packard (HP) and Alpha processors, without greatly increasing memory requirements.     

A rapid method for the determination of radiostrontium in river water

A rapid analytical method, applicable for the selective separation and determination of⁹⁰Sr and⁸⁹Sr in river water, is described. Strontium is extracted from the water sample at pH 10.5 by TTA/TOPO in cyclohexane in the presence of Tiron as masking agent for interfering ß-emitters. Radiostrontium is measured by liquid scintillation after back-extraction into 1N nitric acid. The distribution coefficient of strontium is over 400 and the separation factors from other radionuclides are higher than 5.0×10³.     

An improved sealed quartz‐tube method for the determination of hydrogen isotopes in water

Hydrogen stable isotope analysis has been a valuable tool in the fields of geochemistry and ecological research as well as many other research fields. The methods are mainly divided into the dual‐inlet method (off‐line method) and continuous flow method. The dual‐inlet method is complicated and inefficient, but it is still important because of its high precision and wide application range. Although the continuous flow method improves the experimental efficiency, the memory effect is noticeable and the accuracy is reduced. An improved sealed quartz‐tube method is proposed in this paper. The sample is sealed in a capillary tube and placed in a quartz tube containing chromium powder. It is then packaged, evacuated, reacted at a high temperature, and analyzed for hydrogen isotope ratio. Excellent data accuracy, good reproducibility (<1‰), and no memory effect occurred in the method. The process is relatively simple, and the experimental efficiency is greatly improved, which provides an effective method for the analysis of hydrogen isotopes in complex liquid samples.     

An improved ion chromatographic method for determination of trace levels of perchlorate in environmental water

An improved ion chromatographic (IC) method was developed to determine trace levels of perchlorate in environmental water samples. Perchlorate was separated in the hydroxide selective column IonPac AS16 using NaOH as an eluent with an organic modifier. To eliminate the coelution of perchlorate and 4-chlorobenzene sulfonate (4-CBS), an organic solvent as modifier was added to the eluent. Of four organic solvents studied, acetonitrile proved to be the most efficient based on the retention time of perchlorate and 4-CBS. To improve the method sensitivity, a concentrator column (AG19) was used to concentrate perchlorate online. With the adoption of a preconcentration step, the sensitivity of our method was improved and the method detection limit (MDL) was reduced to 0.1 μg/L. The linear range was from 0.2 μg/L to 200 μg/L with a linear correlation coefficient of 0.9989 and the relative standard deviation (RSD) of peak area for eleven successive injections of 0.5 μg/L perchlorate was 4.2%. The method had been applied to the determination of perchlorate in some real environmental water samples and recovery was between 93% and 113%. __________ Translated from Chemical Journal of Chinese Universities, 2007, 28(7), 1246–1250 [译自: 高等学校化学学报]     

An improved method for technetium determination in environmental samples

Summary The recent developments of extraction chromatography and ICP-MS made easier the determination of ⁹⁹Tc in environmental samples. However, in the non-contaminated area, a pre-concentration procedure is necessary, because usually a large amount of sample is used for analysis. In this study, the ferrous ion (Fe²⁺) added as a reductant can make chemical yield from 50 to 80%, when larger than 100 liter water samples or 500 g soil samples are analyzed. The extraction chromatography with TEVA resin (EIChrom) and the measurement by ICP-MS have been developed using ^95mTc and ¹⁰³Ru as yield tracers. Detection limits of 3σ are 0.054 mBq/kg for 500 g soil and 0.032 µBq/lfor 500 l water. A pond named Hinotani, Mie Prefecture in the central part of Japan, was selected to be investigated as a natural system in a non-contaminated area. Surface soil near this pond, pond water and sediment were collected and analyzed for ⁹⁹Tc. In a high fall-out area, Okuetsu, Fukui Prefecture forest soil was collected and analyzed. The ⁹⁹Tc in the surface (0-5 cm) was 10.5±0.8 mBq/kg. The ⁹⁹Tc in Hinotani surface (0-5 cm) soil were 0.77±0.06 mBq/kg less than in Okuetsu. Technetium-99 has been determined in pond water, sediment (0-5 cm) and shrimps in the Hinotani pond, 0.25±0.02 mBq/l, 3.3±0.3 mBq/kg, 1.5±0.2 mBq/kg, respectively.     

An improved method for the determination of free sphingosine in serum

Summary A rapid, sensitive and selective high-performance liquid chromatographic method has been developed for the determination of sphingosine in human serum. After precipitation with methanol, the samples were extracted using Carbopack B disposable columns; the sphingosine was eluted with 0.05 M hydrochloric acid in methanol-dichloromethane (20∶80, v/v) and the extract evaporated to dryness at 40°C. The sample residue was then reconstituted with methanol and reacted with o-phthaldialdehyde reagent to produce a fluorescent compound. Separation was performed using an LC-18 column with 0.05 M phosphate buffer (pH 7)-methanol-acetonitrile (15∶80∶5, v/v) as mobile phase. Fluorescence detection was performed with excitation and emission wavelengths of 340 and 455 nm, respectively. The serum extract was re-analyzed with a cyano LC column to minimize the possibility of false positive results. The possible interference of compounds having a structure similar to that of sphingosine was evaluated. The mean recovery of sphingosine was >94.5%. The limit of detection of the assay was 1 ng mL⁻¹. The between-run and within-run coefficients of variation for replicate analyses were <4.0% and <3.4%, respectively. The levels of free sphingosine in the serum of 40 normal subjects (20 male and 20 female) was investigated; the average level was 81.6±41.1 ng mL⁻¹ (mean ±S.D.) for males and 85.5±33.7 ng mL⁻¹ for females.     

Rapid fusion method for determination of actinides in fecal samples

A new rapid fusion method for the determination of actinides in fecal samples has been developed at the Savannah River National Laboratory that can be used for emergency response or routine bioassay analyses. If a radiological dispersive device, improvised nuclear device or nuclear accident occur, there will be an urgent need for rapid analyses of environmental, food and bioassay matrices. If an inhalation event occurs and there is confirmed radionuclide activity present via urine analyses of individuals, fecal analyses will typically be required to determine the soluble/insoluble fraction of actinides present as a result of the event to allow a more reliable estimate of radiological dose. The new method for actinides in fecal samples uses accelerated furnace heating, a rapid sodium hydroxide fusion method, a lanthanum fluoride matrix removal step, and a column separation process with stacked TEVA, TRU and DGA resin cartridges. The rapid fusion method provides rugged digestion of any refractory particles present, essential for reliable analysis of actinides in fecal samples. Alpha spectrometry was used to determine the actinide isotopes, but this method can be adapted for assay by inductively-coupled plasma mass spectrometry for actinide isotopes with longer half-lives that have sufficient mass to allow measurement. The method showed high chemical recoveries and effective removal of interferences. The determination of actinides in fecal samples can be performed in less than 12 h in an emergency with excellent quality for emergency samples. The new method, which is much less tedious and time-consuming than other reported methods, can be used for emergency or routine fecal sample analyses. This enables more timely estimates of radiological dose to be performed that utilize soluble/insoluble actinide ratios.     

Assay of actinides in human urine by rapid method

A method using DGA resin (N,N,N′,N′-tetra-n-octyldiglycolamide on an inert support) was developed for the rapid analysis of actinides in urine samples. Samples acidified with HCl to 4 M were loaded directly (without digestion) onto a DGA column. Actinides were stripped simultaneously, α-sources were prepared by co-precipitation with NdF₃. Americium, plutonium and uranium were separated with acceptable high recoveries (40–80%). The americium, plutonium and uranium content of 100–200 ml urine samples was determined within 24 h with detection limits as low as 0.01 Bq l^?1. Based on model experiments using ¹⁴C-spiked urea, it was proven that high urea content can affect americium separation deleteriously due to irreversible fixing of americium on DGA resin.     

An improved method for determination of 7Be in mosses

We have measured ⁷Be activity in moss samples collected from in and around Mumbai, India. The use of heavily shielded Compton suppressor system is more efficient than the conventional gamma spectroscopic system for detection of ⁷Be. The ⁷Be accumulation capacities of mosses are more than other plant samples. Therefore monitoring of young moss samples by Compton suppressor system is an excellent tool for determination of atmospheric fallout of ⁷Be. A positive bias in the high altitude samples has been observed which might be due to any of the two reasons (i) higher cosmic ray flux in the high altitude or (ii) high pollution in the lower altitude area ultimately inhibits uptake of ⁷Be.     

Rapid determination of actinides and Sr in river water

Nuclear accidents occurred in latest years highlighted the difficulty to achieve, in a short time, the quantification of alpha and beta emitters. Indeed, most of the existing methods, though displaying excellent performances, can be very long, taking up to several weeks for some radioisotopes, such as ⁹⁰Sr.     

An improved method for determination of air-borne polycyclic hydrocarbons

Summary In a search for a more effective solvent system than those discovered up to 1971 for separating the polycyclic hydrocarbon mixtures occurring in high-temperature tars, modifications were made to one found in 1957. Whatman No. 4 paper impregnated with 10% liquid paraffin solution in petrol ether was used as stationary phase, and methanol saturated with liquid paraffin as ascending mobile phase. Chromatography at 18° for 6 hr on 45×45 cm sheets of paper gave a separation considerably better than that achieved originally. Special attention was paid to the fraction containing carcinogenic hydrocarbons. No column chromatography or other pretreatment was necessary. Owing to the better separation it is possible to determine further polycyclic hydrocarbons such as 1,2, 5, 6-dibenzoanthracene, 3, 4, 9, 10-dibenzopyrene, and 3, 4, 8, 9-di-benzopyrene. A spot-evaluating procedure and a pretreatment of air samples have been developed. This procedure permits analysis of imponderable air samples.

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Zusammenfassung Auf der Suche nach einem besseren Lösungsmittelsystem zur Auftrennung polycyklischer Kohlenwasserstoffgemische aus Hochtemperaturteer wurde ein Verfahren aus dem Jahr 1957 modifiziert. Whatmanpapier Nr. 4 wurde mit einer 10% igen Lösung von flüssigem Paraffin in Petroläther als stationäre Phase imprägniert und Methanol, gesättigt mit flüssigem Paraffin, diente als aufsteigende Phase. Chromatographiert wurde bei 18° C durch 6 Stunden auf Papierblättern der Größe 45×45 cm. Die Trennung verlief erheblich besser als nach der Originalvorschrift. Besondere Aufmerksamkeit galt der Fraktion carcinogener Kohlenwasserstoffe. Säulenchromatographie oder eine andere Vorbehandlung ist nicht nötig. Infolge der besseren Auftrennung lassen sich polycyklische Kohlenwasserstoffe wie 1, 2, 5, 6-Dibenzoanthracen, 3, 4, 9,10-Dibenzopyren und 3, 4, 8, 9-Dibenzopyren bestimmen. Ein Verfahren zur Auswertung der Chromatogramm-flecken sowie die Vorbehandlung der Luftproben wurden ausgearbeitet. Die Analyse unwägbarer Luftproben wurde so ermöglicht.

     

An improved HPTLC method for the rapid identification and quantification of sulfonamides

Summary R_f values of twenty therapeutic sulfonamides have been estimated in seven solvent systems. Based on these data a simple identification scheme was developed demanding only three solvent systems for complete separation.Quantification of corresponding fluorescamine derivatives at nanogram level was performed by the use of an TLC-scanner configured online with a microcomputer. Mathematical treatment of standard curves using the computer program Curve Fitter are discussed. Validity and reproducibility of results are compared with data obtained by HPLC and show good correlation.     

An improved method for the determination of glycosyltransferases usingpara-nitrophenyl-glycosides as substrates

Due to their easy purification nitrophenyl-glycosides have become of increasing interest as acceptor substrates for the assay of glycosyltransferase activity. In this communication reversed-phase chromatography is shown to provide a convenient means for the isolation of the radioactively labelled nitrophenylglycoside(s) formed in this reaction, superior to the methods hitherto used with regard to speed and specifity.     

A rapid solvent extraction method for the determination of radio-iodine in sea water.

A solvent extraction procedure for the determination of radio-iodine in sea water is described. The water is treated with alkaline permanganate to remove algae, and, after removal of permanganate, the iodide is oxidized to iodine for extraction into toluene. The radio-iodine with carrier is stripped from the solvent then re-extracted into a smaller volume of toluene for liquid scintillation counting and colorimetric determination of carrier recovery as iodine. 2-Methyl-1-butene is used to decolorize the toluene-iodine solution under u.v. light and avoid colour quenching during counting. Samples spiked with iodine-131 showed essentially quantitative recovery from 1.0 l of sea water with a typical recovery of 80–85% of carrier. The method is applicable in the presence of high concentrations of many foreign ions and the decontamination factor for a number of radionuclides is greater than 10³. The limit of detection is less than 5.0 · 10^-9 μCi ml^-1.     

An improved iodometric method for the successive determination of copper and zinc

The method described by haider and khundkar for the succesive iodometric dctcrmination of copper and zinc gives results that arc too low both for copper and for zinc. The errors may amount to —20% for copper and to —5% for zinc. The causes of these errors arc traced and eliminated and an improved method for the succesive iodometric determination of copper and zinc is described.     

An improved method validation for rapid determination of acrylamide in foods by ultra-performance liquid chromatography combined with tandem mass spectrometry

An improved method was validated for the determination of acrylamide in foods using ultra-performance liquid chromatography (UPLC) coupled to eletrospray ionization tandem mass spectrometry (MS/MS) in the present study. This improved method supplies a rapid quantitative procedure of acrylamide with a run time of only 3 min. Results showed a good repeatability (RSD< or =4.5%) with 50, 100, 250, 500 and 1000 microg/kg spiked concentrations in potato crisps in within-day (n=5) and day-to-day (n=10) precision tests. Meanwhile, good recoveries (81.6-99.0%) were obtained with the same spiked concentrations in acrylamide-free cereal samples (n=3). The excellent method validation data and proficiency test results (Z-score: -0.1) of the official Food Analysis Performance Assessment Scheme (FAPAS) suggested that the present quantitative method could be applied for rapid determination of acrylamide in many investigations.     

An improved method for determination of light hydrocarbons in stabilized crude oil

Summary This paper reports a quick, and simple method for quantitative determination of C₂ to C₆ hydrocarbons in stabilized crude oil without using a back flush system. A mixture of crude oil and internal standard is injected into a GC equipped with a 6 meter length of fused silica capillary as a guard column. The light hydrocarbons are separated individually up to the last peak of the hexane group with the heavier components trapped in the guard column. The total analysis time for each sample is 15 minutes. The base line is table for up to 15 consecutive analyses. The guard column and the injector port are then reconditioned by simply heating them for one hour at 300 °C.