Polarographic analysis for corticosteroids: Part 4. Determination of Corticosteroids in Multicomponent and Complex Pharmaceutical Preparations

Differential pulse polarographic methods for determination of corticosteroids in multicomponent and complex pharmaceutical preparations are described. The influence of other reducible common components of such preparations and excipients on the height of the reduction peaks of corticosteroids and the accuracy of the results was investigated, as well as the interference of excipients by adsorption processes at the electrode or at solid particles of the preparations. In the procedures developed, variations in composition of the supporting electrolyte according to the lipophilicity of the preparation, and the use of standard additions, produce results quickly and reliably. Standard deviations vary from 0.8 to 2.8%.     

Photophysical properties of borondipyrromethene analogues in solution

The photophysical properties of seven new 8-(p-substituted)phenyl analogues of 4,4-difluoro-3,5-dimethyl-8-(aryl)-4-bora-3a,4a-diaza-s-indacene (derivatives of the well-known fluorophore BODIPY) in several solvents have been studied by means of absorption and steady-state and time-resolved fluorimetry. For each compound, the fluorescence quantum yield and lifetime are lower in solvents with higher polarity owing to an increase in the rate of nonradiative deactivation. Increasing the electron withdrawing strength of the p-substituent on the phenyl group in position 8 also leads to lower fluorescence quantum yields and lifetimes. When the p-substituent on the phenyl group in position 8 is a tertiary amine [8-(4-piperidinophenyl), 8-(4-N,N-dimethylaminophenyl), and 8-(4-morpholinophenyl)], the low quantum yields of these compounds in more polar solvents can be rationalized by the inversion of the energy levels of an apolar, highly fluorescent and a polar, nonfluorescent excited state, where charge transfer from the tertiary amine to the BODIPY unit occurs. These amine analogues can be protonated at low pH in aqueous solution. Fluorescence titrations yielded pK(a) values of their conjugate ammonium salts which are in agreement with the electron donating tendency of the amine group: piperidino (4.15) > dimethylamino (2.37) > morpholino (1.47), with the pK(a) values in parentheses. The rate constant of radiative deactivation (k(f)) is the same for all compounds in all solvents studied (k(f) = 1.4 x 10(8) s(-1)).     

Residue study of doxycycline and 4-epidoxycycline in pigs medicated via-drinking water.

A study was performed to determine the residues in edible tissues of healthy pigs after continuous administration of doxycycline with drinking water for five consecutive days at a dose rate of 10.5 mg doxycycline kg-1 body weight (BW) per day. Quantitation was performed using a validated HPLC method with fluorescence detection. The method was able to separate doxycycline and its 4-epimer, 4-epidoxycycline. This epimer was found in kidney, liver, skin, fat and muscle tissue. The method was validated at the maximum residue limit (MRL), at half the MRL and at double the MRL for both doxycycline and 4-epidoxycycline. Linear calibration curves were obtained in spiked tissues (r > 0.99). The accuracy of the calibrators of the calibration curves was within -20% to +10%. The accuracy and precision (expressed as the within-run repeatability) were found to be within the required ranges for the specific concentration. The limits of detection and limits of quantification were below one-half of the MRL. The quantification limits were 50 micrograms kg-1 for doxycycline and 100 micrograms kg-1 for 4-epidoxycycline in kidney and liver, 20 micrograms kg-1 for doxycycline and 50 micrograms kg-1 for 4-epidoxycycline in skin and fat and 10 micrograms kg-1 for doxycycline and 50 micrograms kg-1 for 4-epidoxycycline in muscle tissue. The withdrawal time was calculated according to the recommendations of the European Agency for the Evaluation of Medicinal Products (EMEA/CVMP/036/95) and was set at 3 days. The plasma concentration of doxycycline and the stability of doxycycline in drinking water were also determined during the treatment period. The mean plasma concentration of doxycycline during the treatment period ranged from 0.83 to 0.96 microgram ml-1. Thirty-six hours after the withdrawal from medicated drinking water, no plasma levels could be detected. Samples of medicated water were taken at time zero and at 24 h after addition of doxycycline to the drinking water. No statistically significant difference in the mean drinking water concentration was seen at time zero and at time 24 h (Student's t-test, alpha = 0.05).     

Preparation and characterization of a set of IAEA reference air filters for quality control in air-pollution studies

Several sets of reference air filters were prepared as part of an IAEA evaluation of the performance of laboratories involved in air-pollution studies. Each set comprised three polycarbonate membrane filters, two of which were loaded with urban air particulate matter (APM) obtained in Vienna or Prague, and one unloaded filter. The filters were loaded by filtration of a suspension of the APM materials in water. The homogeneity both of bulk APM materials and of the loaded filters was evaluated and found suitable by determining several elements by instrumental neutron-activation analysis (INAA), proton-induced X-ray emission (PIXE), and micro-X-ray energy-dispersive fluorescence analysis (micro-EDXRF). After evaluation of the homogeneity, INAA, PIXE, EDXRF, atomic absorption spectrometry (AAS), inductively coupled plasma optical emission spectrometry (ICP-OES), and ICP mass spectrometry (ICP-MS) were used to characterize the filter materials and establish "target values" and their associated standard deviations for 15 elements. Problems encountered during the preparation of these unique, simulated air filters and the criteria for setting both the target values and standard deviations are presented.     

迭代目标转换因子分析光度法同时测定钇和其它稀土合量

以三氯偶氮胂为显色剂，根据钇(Y^3 )与其它稀土组分的显色络合物吸收光谱差别较大的特点，提出应用迭代目标转换因子分析光度法同时测定钇和其它烯土合量的计算光度分析法，通过对不同组成的人工模拟样品和龙南稀土氧化物标准样中的钇和其它稀土合量的测定，取得了满意的结果。     

Reactions of organomercury fulminates with acetylene derivatives

Organomercury fulminates react with acetylene derivatives to give unstable 3-(organomercurio)isoxazoles, which isomerize to 2-cyanoenolates. These are hydrolyzed with hydrochloric acid to the corresponding enols and are cleaved by water at the double bond. With monosubstituted acetylenes, substitution at the free position by the organomercury residue is predominant.