Depleted uranium (DU) is a by-product of the uranium enrichment process for nuclear fuel. According to the Commission Decision 2002/657/EC, a confirmatory method for the quantification of DU in freeze-dried fish was developed by isotope ratio dynamic reaction cell inductively coupled plasma-mass spectrometry (IR-DRC-ICP-MS). A preliminary study was performed to determine the following parameters: instrumental detection limit (IDL), isotopic ratio measurement limit (IRML), percentage of DU (P(DU)) in presence of natural uranium (NU) and limit of quantification (LoQ(DU)). The analyses were carried out by means of IR-DRC-ICP-MS. Ammonia was the reaction gas used for the dynamic reaction cell. In addition, a sector field inductively coupled plasma mass spectrometer (SF-ICP-MS) was employed to calculate the within-laboratory reproducibility. For the confirmatory method the following parameters were determined: (a) trueness; (b) precision; (c) critical concentrations alpha and beta (CC(alpha), CC(beta)); (d) specificity; (e) stability. Trueness was assessed by using the recovery tests. The recovery and within-laboratory reproducibility were determined by fortifying the blank digested solution of dogfish tissue: six aliquots were fortified at 1, 1.5 and 2 times the LOQ(DU) with 25.0, 37.5 and 50.0 ng L(-1) or 4.16, 6.24, 8.32 microg kg(-1) with a recovery of -8.2, +9.5 and +9.6%, respectively and a within-laboratory reproducibility (three analytical run) of 15.5, 8.0 and 11.0%, respectively. The results for the decision limit and the detection capability were: CC(alpha) = 11.69 ng L(-1) and CC(beta) = 19.8 ng L(-1). The digested solutions resulted to be stable during testing time (60 days) and the method can be considered highly specific as well. 相似文献
The lipophilicity of thirty-two novel acetylcholinesterase (AChE) inhibitors — 1,2,3,4-tetrahydroacridine and 2,3-dihydro-1H-cyclopenta[b]quinoline derivatives was studied by thin layer chromatography. The analyzed compounds were chromatographed on RP-18, RP-8, RP-2, CN and NH2 stationary phases with dioxane — citric buffer pH 3.0 binary mobile phases containing different proportions of dioxane. RM values for pure water were extrapolated from the linear Soczewiński-Wachtmeister equation and six compounds with known literature log P values were used as reference calibration data set for computation of experimental log P values. The obtained results were compared with computationally calculated partition coefficients values (AlogPs, AClogP, AlogP, MlogP, KOWWIN, XlogP2, XlogP3) by PCA and significant differences between them were observed. 相似文献
The lipophilicity of the novel 12 products of the reaction of N3-substituted amidrazones with cis-1,2-cyclohexanedicarboxylic anhydride (4 linear, 4 triazole-like and 4 isoindole ones) with potential pharmacologic activity was evaluated by thin layer and liquid chromatography. Using organic-aqueous eluent systems (with methanol or acetonitrile) on RP18 plates and C18 column, a linear relationship between the volume fraction of modifiers and the retention indices was obtained. The retention values, log k or RM were extrapolated to zero organic modifier content to obtain the log kw or RMW values. 12 compounds with known literature lipophilicity were used as a calibration dataset. The results were compared in a multivariate way with in silico methods (ALOGPs, AC_logP, AB/LogP, COSMOFrag, miLogP, ALOGP, MLOGP, KOWWIN, XLOGP3).
The 6 antihyperlipidemic agents-bezafibrate, ciprofibrate, clofibrate, clofibric acid, fenofibrate, and gemfibrozil-were separated on octadecyl (C18) and cyano (CN) chemically bonded columns using mobile phases containing phosphate buffer and different amounts of acetonitrile, dioxane, propan-2-ol, methanol, and tetrahydrofuran. Relationships between log k values and mobile phase composition have been examined for these systems. Analysis was performed on a Waters LC system with Merck LichroCART C18 and CN 125 mm columns using a flow rate of 1 mL/min and 227 nm detection. More than one-half of the results fitted Snyder-Soczewinski equations with r >0.995. Separation of all drugs was achieved on the C18 column with a mobile phase containing 45% propan-2-ol in phosphate buffer (pH = 2.145) and on a CN column with 20% acetonitrile in the same buffer. The best mobile phase, containing 45% propan-2-ol, was used to quantitate bezafibrate, ciprofibrate, fenofibrate, and gemfibrozil in pharmaceutical formulations. The active substances were extracted with methanol. The calibration curve was constructed in the 0.1-0.8 mg/mL range for all drugs and provided satisfactory linearity (Lack-of-Fit test and Mandel's test). The recovery function was sufficiently linear in all cases, with an insignificant intercept and slope very close to 1. Accuracy was tested by quantitating 3 fortified samples (50, 100, and 150%), which gave results without significant differences. None of the excipients interfered in the analysis. The recovery was 99.85% for bezafibrate, 99.02% for ciprofibrate, 99.53% for fenofibrate, and 99.92% for gemfibrozil, with relative standard deviation values of 0.63, 1.61, 1.84, and 0.88%, respectively. 相似文献
This paper deals with some important (but often neglected) details about the uncertainty of retention measurement in thin layer chromatography, the propagation of uncertainty during computing simple and more complex values from the retention data, ending in influence of the retention uncertainty onto the regression estimates during extrapolation and lipophilicity estimation. Theoretical considerations are tested on data from previous study. It can be concluded that when TLC spots are broad and the retention uncertainty exceeds about 0.02 of RF value, the uncertainty should be taken into the account in further computations. 相似文献
Seven sartans have been chromatographed with acetonitrile-buffer and methanol–buffer in different proportions as mobile phases. The retention values, log k or RM were extrapolated to zero organic modifier content to obtain the log kw or RMW values. Calibration equations were obtained for standards of known lipophilicity. A simple method employing a gradient procedure of 10–100% acetonitrile or methanol in 60 min and standards of the extreme lipophilicity was also elaborated. Chromatographic log P values were compared to those calculated by use of different software products. Finally, principal component analysis was performed to explore and visualize similarities and differences among the drugs and among the methods. 相似文献
A highly enantioselective, organocatalytic, and scalable synthesis of a very unusual cis-decalin-cis-hydrindane tricyclic diterpenoid system has been achieved. Despite the prevalent pharmacological space that the related trans,trans and trans,cis-systems occupy, there have been no reports of an asymmetric synthesis of the cis,cis systems in the literature until now. We demonstrate the flexibility of our approach not only through access to a diverse range of products, all of which are attained in exceptionally high selectivities, but also by showing their easy conversion to the corresponding trans,cis-system and other derivatives. 相似文献
This paper presents a preliminary study in building discriminant models from solid-state NMR spectrometry data to detect the presence of acetaminophen in over-the-counter pharmaceutical formulations. The dataset, containing 11 spectra of pure substances and 21 spectra of various formulations, was processed by partial least squares discriminant analysis (PLS-DA). The model found coped with the discrimination, and its quality parameters were acceptable. It was found that standard normal variate preprocessing had almost no influence on unsupervised investigation of the dataset. The influence of variable selection with the uninformative variable elimination by PLS method was studied, reducing the dataset from 7601 variables to around 300 informative variables, but not improving the model performance. The results showed the possibility to construct well-working PLS-DA models from such small datasets without a full experimental design. 相似文献