Development of a flow-sheet for the radiochemical processing of irradiated sulphate targets for the production of carrier-free 32P

Carrier-free ³²P was produced in KAlpakkam MINI reactor (KAMINI) via ³²S (n, p) ³²P using its small fast flux component. This method has established the flow-sheet for the production of ³²P from sulphate targets such as magnesium sulphate and strontium sulphate which can withstand high temperatures of fast reactors unlike the conventionally used sulphur powder. The chemical processing involved (i) struvite precipitation method for magnesium sulphate and (ii) co-precipitation with ferric hydroxide method for strontium sulphate.     

Generalized Racah method for the evaluation of CFP for mixed electronic configurations

The Racah method, proposed for the evaluation of coefficients of fractional parentage (CFP ) for single shell configurations, is generalized for the cases of two and more than two shells. On the basis of the generalized Racah method, we have evaluated one-particle CFP for all states of s^vp^μ electronic configurations. Two-particle CFP are expressed through one-particle CFP and Racah coefficients.     

Fast ultrasound-assisted method for the determination of the oxidative stability of virgin olive oil

A method for accelerating the determination of the oxidative stability of virgin olive oil by use of ultrasound energy is proposed. The most influential variables on the acceleration of the process were those characteristic of the ultrasound probe, namely irradiation time, duty cycle and pulse amplitude, and they were exhaustively optimized. The ultrasound device, a cylindrical titanium alloy microprobe (3 mm diameter), was immersed into the olive oil sample contained in a 5 cm long test tube where the ultrasound waves were applied directly. The oxidation process was monitored at 270 nm. Twelve samples of virgin olive oil with known oxidative stability, ranging between 19 and 129 h, calculated by the Rancimat method, were analyzed and the results obtained showed an excellent correlation (r=0.9961) with those provided by the Rancimat method. The proposed method drastically decreased the time required for the determination of this parameter, e.g. a virgin olive oil with oxidative stability 129 h, as calculated by the Rancimat method, required only 50.5 min, thus decreasing the determination time 110 times. The method was applied to the determination of the stability of five extra virgin olive oils from different varieties of olive seeds. The values obtained were interpolated in the correlation plot for the calculation of the values corresponding to the Rancimat method. They coincided with those calculated previously with this method, thus demonstrating the validity of the proposed method.     

Method for the preparation of aluminum hydride

A new method for the preparation of aluminum hydride is proposed by reacting SiCl₄ or SiHCl₃ with lithium aluminum hydride in ether/toluene. The method yields hexagonal crystalline AlH₃ with a low chlorine content, increased thermal stability, and high reproducibility.     

New method for allowance for the activity of the nucleophile in calculations of the reactivities of heteroaromatic compounds

A new method for allowance for the activity of the nucleophile in calculations of the reactivities of heteroaromatic compounds that is based on the special application of the valence molecular orbital (VMO) theory in the form of Dewar reactivity numbers is proposed. It is shown that there is a correspondence between the proposed method and the general VMO theory. The 5-azacinnoline molecule was calculated by both methods. According to the calculations, the 6-C atom should be the most active in reactions with hard bases, whereas the 4-C atom should be the most active in reactions with soft bases. A qualitative correspondence between the proposed method and the DMTS (delocalization model of the transition state) method is also demonstrated in the case of the quinolinium cation.More complex computational methods are presently not applicable to many-atom systems and not found in the literature.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 3, pp. 403–405, March, 1979.     

A Method for the polarographic determination of the stability constants of mixed complexes

A new method for determining the stability constants of mixed complexes is proposed which is especially appropriate when only the mixed complex 1:1:1 is formed. In order to verify this method, the coordinate system Pb(II)-SCN^?-NO^?₃ has been studied polarographically in aqueous medium of a constant ionic strength of μ = 1.0 M. Using our knowledge of the stability constants of simple complexes and applying this method we obtain β₁₁ = 8 for the mixed complex.     

A diagnostic tool for determining the quality of accuracy validation. Assessing the method for determination of nitrate in drinking water

Realistic internal validation of a method implies the performance validation experiments under intermediate precision conditions. The validation results can be organized in an X _Nr×Ns (replicates×runs) data matrix, analysis of which enables assessment of the accuracy of the method. By means of Monte Carlo simulation, uncertainty in the estimates of bias and precision can be assessed. A bivariate plot is presented for assessing whether the uncertainty intervals for the bias (E ± U(E)) and intermediate precision (RSDi ± U(RSDi) are included in prefixed limits (requirements for the method). As a case study, a method for determining the concentration of nitrate in drinking water at the official level set by 98/83/EC Directive is assessed by use of the proposed plot.     

A new algorithm for the variational solution of the vibronic problem for polyatomic molecules

A new effective algorithm for solving the complete vibronic problem by the variational method is proposed. The algorithm reduces the variational matrix by successively including the shift and entanglement of normal coordinates and using recurrent formulas for determining the eigenvectors of the matrix. No additional approximations are used. The method is faster than those used previously by two or more orders of magnitude. This work was supported by the Russian Fundamental Research Fund (93-02-3405). K. A. Timiryazev Moscow Agricultural Academy. Translated fromZhurmal Strukturnoi Khimii, Vol. 35, No. 6, pp. 23–30, November–December, 1994. Translated by O. Kharlamova     

qNMR for profiling the production of fungal secondary metabolites

Analysis of complex mixtures is a common challenge in natural products research. Quantitative nuclear magnetic resonance spectroscopy offers analysis of complex mixtures at early stages and with benefits that are orthogonal to more common methods of quantitation, including ultraviolet absorption spectroscopy and mass spectrometry. Several experiments were conducted to construct a methodology for use in analysis of extracts of fungal cultures. A broadly applicable method was sought for analysis of both pure and complex samples through use of an externally calibrated method. This method has the benefit of not contaminating valuable samples with the calibrant, and it passed scrutiny for line fitting and reproducibility. The method was implemented to measure the yield of griseofulvin and dechlorogriseofulvin from three fungal isolates. An isolate of Xylaria cubensis (coded MSX48662) was found to biosynthesize griseofulvin in the greatest yield, 149 ± 8 mg per fermentation, and was selected for further supply experiments. Copyright © 2016 John Wiley & Sons, Ltd.     

A spectrofluorimetric method for the determination of acitretin in pharmaceuticals

A simple, rapid, and highly sensitive spectrofluorimetric method for the determination of acitretin was developed based on the strong green fluorescence of acitretin. Influence of organic solvents on the fluorescence spectra of acitretin was studied. Effects of pH, standing time, and foreign ions on the determination of acitretin were also examined. Under the optimum conditions, linear relationship between the relative fluorescence intensity and the concentration of acitretin in the range of 30.0–1100 ng mL⁻¹ was obtained. Detection limit of this method is 9.56 ng mL⁻¹ for acitretin. Relative standard deviation for the determination of 480 ng mL⁻¹ of acitretin was 1.70 %. This method was used for the determination of acitretin in pharmaceuticals and the results were compared with those obtained by the HPLC method.     

An installation for the preparation of foraminifera micro samples for the isotopic analysis of carbon and oxygen

A technical modification of the traditional method of decomposition of carbonates in phosphoric acid was proposed for the determination of δ¹³C and δ¹⁸O in organogenic carbonate samples weighing 10–30 μg with an accuracy of 0.05%. The extraction of CO₂ was carried out under a vacuum at 95°C in 105% phosphoric acid. The isotopic composition of CO₂ was measured by CG-IRMS. The used feed-motion of samples to the reactor provides a consecutive delivery of the samples from the sample holders to the acid. This sample feeding method prevents the contamination of the acid with impurities from the surface of the sample, obviates the necessity of removing the sample holders from the acid, and allows the use of the same acid for performing a very large numbers of analyses. The accuracy and reproducibility of the δ¹³C and δ¹⁸O values was estimated by measuring international standards and comparing with the δ¹³C and δ¹⁸O values for organogenic carbonate samples obtained by the proposed method of analysis at a microgram level and the traditional method at a milligram level. The proposed technology was successfully used to study the isotopic composition of oxygen and carbon in the plankton and benthos foraminifers in order to reconstruct the Okhotsk Sea palaeotemperatures.     

Improved method for the synthesis of pentaphenylcyclopentadiene

An improved method for the synthesis of pentaphenylcyclopentadiene is suggested. It involves the reaction of tetraphenylcyclopentadienone with PhMgBr and subsequent treatment of the reaction mixture with an excess of LiAlH₄ in THF. The effect of arylating agents and reducing agents on the yield of the target product is studied. The method suggested can be used for synthesizing other polyaromatic cyclopentadienes, in particular, 1,2,5-triphenyl-3, 4-(1,8-naphthylene)cyclopentadiene.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 3, pp. 603–604, March, 1993.     

A Study for the Validation of Spectrophotometric Methods for Detection, and of Digestion Methods Using a Flow Injection Manifold, for the Determination of Total Phosphorus in Wastewaters1

A study for the validation of orthophosphate determination using an FI-manifold/spectrophotometric detection set-up is made. Under optimized conditions, the method with the largest valid range (0–50 mg L^–1), with the possibility of extending it even higher) is the molybdate/ascorbic acid method; its reproducibility and interferences are similar to other tested methods. A study among the conventional digestion methods is then made to test the adaptability of the method to FI systems. The persulfate digestion method was found to be more suitable for use with flow systems. The persulfate digester was connected in-line with the FI-manifold; under optimized conditions, the sensitivity of the method is decreased, especially when used with organic phosphorus compounds, but it is still reasonable for use. The sensitivity is also dependent on the nature of the phosphate species attached to the organic residue. In addition, it was found that colloid precipitate phase in the sample decreases the sensitivity. Finally, real wastewater samples were tested using the UV radiation-assisted, persulfate digester-implemented FI-system method, and using the batch method. It was found from the correlation of the two methods that the fraction of P-recovery in the FIA system was 2/3 of the total phosphate, suggesting that the rest was due to the polyphosphate content.     

A rapid method for determining the casein content of milk

A method is presented for the rapid determination of the casein content of milk by Direct Injection Enthalpimetry (DIE).A significant heat pulse of precipitation of casein is produced by adjusting the pH of the solution to the pH of the isoelectric point of casein. The method is calibrated against a real sample whose casein content has been determined by a standard method incorporating the time consuming Kjeldahl method, but once calibrated the proposed method can be operated routinely by non-skilled personnel. The method is sensitive and gives results as acceptable as those obtained by standard methods. The method can be applied to most liquid samples without the need for prior preparation. the main advantages of the method are those of time and costs of analysis and the potential of the enthalpimetric method for automation.

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Zusammenfassung Es wird ein Verfahren zur Schnellbestimmung des Kaseingehaltes von Milch mittels Direct Injection Enthalpimetry (DIE) beschrieben.Durch das Einstellen des pH-Wertes der Lösung auf den pH-Wert des isoelektrischen Punktes von Kasein kann infolge des Ausfällens von Kasein ein eindeutiger Wärmeimpuls erzeugt werden. Das Verfahren wurde anhand einer wirklichen Probe geeicht, deren Kaseingehalt mittels dem zeitaufwändigen Kjeldahl-Verfahren bestimmt wurde. Einmal kalibriert kann das neue Verfahren routinehaft auch von Laien durchgeführt werden. Die Empfindlichkeit der Methode ist gut, die erhaltenen Ergebnisse können genauso akzeptiert werden, wie die in Standardverfahren erhaltenen Ergebnisse. Dieses Verfahren kann bei den meisten flüssigen Proben ohne jede vorherige Vorbereitung angewendet werden. Der Hauptvorteil besteht in der Ersparnis von Zeit und Analysenkosten und in der Anwendbarkeit des enthalpiemetrischen Verfahrens zur Automatisierung.

     

A colorimetric method for the determination of carboxylic acids

A new colorimetric method for the determination of carboxylic acids using bromocresol green reagent is established. The formed color follows Beer's Lambert law and is stable for 24 hr. The method is successfully applied for measuring the disappearance of volatile fatty acids in P. oxalicum culture media. The method is reproducable and is used also for the quantitative determination of carboxylic acids in Dowex 1-X8 eluates. A linear relationship between the pK₁ of different carboxylic acids and the calculated molar extinction coefficients of the color formed at 440 nm is demonstrated.     

Use of a dynamic shift scheme for the levels of Brillouin states in the super-CI method

We propose a dynamic shift method for the levels of the Brillouin states, providing reliable and sufficiently rapid convergence of the iteration process in the CASSCF method with optimization of the orbitals according to the super-CI scheme. In each step of the super-CI procedure, the shift parameters are determined automatically and individually for each Brillouin state. The proposed method is simple and easy to carry out. It also guarantees that a physically incorrect solution cannot appear. The method was carried out using the CASSCF programming package; for the example of specific calculations for the¹⁺ state of the TiO molecule, we show that the method is efficient and preferred.Translated from Teoreticheskaya i Éksperimental'naya Khimiya, Vol. 26, No. 1, pp. 6–11, January–February, 1990.     

A numerical basis for the accurate representation of the continuum spectrum of atomic Hamiltonians

We present a method for the accurate calculation of the complete spectrum of the Schrödinger equation in terms of B-splines polynomial basis. The method is capable to represent numerically the bound and continuum spectrum of complex atomic systems. The theoretical method is discussed, and an application to hydrogenic Hamiltonian is given.AMS subject classification: 65705, 34L40     

Sensitive bromatometric methods for the determination of salbutamol sulphate in pharmaceuticals

The proposed methods allow semimicro and microlevel determination of SBS in authentic samples and in dosage forms. The spectrophotometric method is much more sensitive than most of the procedures known for the determination of SBS. The titrimetric method takes less than 15 min for analysis. All the procedures are simple and do not need elaborate treatment or tedious extractions. One titrimetric and two spectrophotometric methods are described for the assay of sulbutamol sulphate (SBS) in bulk drugs and in tablets using bromate-bromide mixture and two dyes, rhodamine B and methylene blue, as reagents. In titrimetry, an aqueous solution of SBS is treated with a measured excess of bromate-bromide mixture in a HCl medium, followed by iodometric determination of unreacted bromine. Spectrophotometric methods involve the addition of a known excess of bromate-bromide mixture to SBS in an acid medium, followed by the determination of residual bromine by reacting with either a fixed amount of rhodamine-B and measuring the absorbance at 555 nm (method A) or methylene blue and measuring the absorbance at 665 nm (method B). In all methods, the amount of in situ generated bromine reacted corresponds to the amount of SBS. The titrimetric method is applicable over the 3.0–8.0 mg range and the reaction stoichiometry is found to be 1: 2 (SBS: KBrO₃). In spectrophotometric methods, the absorbance is found to increase linearly with the concentration of SBS which is corroborated by the correlation coefficient of 0.9978 and 0.9991 for method A and method B, respectively. The systems obey Beer’s law for 0.25–2.5 μg/mL (method A) and 0.75–7.5 μg/mL (method B). The calculated apparent molar absorptivity values are found to be 8.96 × 10⁴ and 4.67 × 10⁴ L mol⁻¹ cm⁻¹, for method A and method B, respectively, and the corresponding Sandell sensitivity values are 6.43 and 12.34 ng/cm². The limits of detection and quantification are also reported for both spectrophotometric methods. Intraday and interday precision and accuracy of the methods were evaluated. The methods were successfully applied to the assay of SBS in tablet and capsule preparations and the results were compared with those of a reference method by applying Student’s t-and F-tests. No interference was observed from common pharmaceutical ajuvants. The text was submitted by the authors in English.     

Continuous photometric method for the screening of human urines for phenothiazines

A fully automated urinary screening system for five phenothiazines has been developed. The method is based on the oxidation of phenothiazines in acid medium to colourless sulphoxides via orange or purple coloured intermediates, which are continuously monitored at 520 nm. Two innovations have been implemented versus the conventional method; first, sulphuric acid (ideal reaction medium) has been changed by nitric acid (less corrosive, and compatible with pumping tubes) and second, problems associated with the instability of phenothiazonium radical cation are eliminated as the measurements are carried out simultaneously to the formation of the coloured products in the flow system. The configuration adopted permits selective retention of phenothiazines on a LiChrolut^®-EN sorbent column before their oxidation with hexacyanoferrate(III) ions in acid medium. The proposed method allows phenothiazines determination within the interval 3-50 μM (1-20 μg ml⁻¹), with a throughput of 12 h⁻¹; an average relative S.D. of 4% (n=11) was obtained for phenothiazine concentration of 5 μM. Finally, a comprehensive study of 50 real urine samples (phenothiazines free) obtained from different individuals provided 6% of false positives and 0% false negatives for chlorpromazine concentrations of 1.5 and 3 μM, respectively.     

Development and validation of the stability-indicating LC-UV method for the determination of cefoselis sulphate

The stability-indicating LC assay method was developed and validated for quantitative determination of cefoselis sulphate in the presence of degradation products formed during the forced degradation studies. An isocratic, RP-HPLC method was developed with C-18 (250 × 4.6 mm, 5 μm) column and 12 mM ammonium acetate-acetonitrile (95:5 V/V) as a mobile phase. The flow rate of the mobile phase was 1.0 mL min⁻¹. Detection wavelength was 260 nm and temperature was 30°C. Cefoselis similarly to other cephalosporins was subjected to stress conditions of degradation in aqueous solutions including hydrolysis, oxidation, photolysis and thermal degradation. The developed method was validated with regard to linearity, accuracy, precision, selectivity and robustness. The method was applied successfully for identification and determination of cefoselis sulphate in pharmaceuticals and during kinetic studies.