共查询到20条相似文献,搜索用时 15 毫秒
1.
Sarraguça MC Cruz AV Amaral HR Costa PC Lopes JA 《Analytical and bioanalytical chemistry》2011,399(6):2137-2147
This work compares the estimation of the particle size distribution of a pharmaceutical powder using near-infrared spectroscopy
(NIRS), powder flowability properties, and components concentration. The estimations were made by considering the former data
blocks separately and together using a multi-block approach. The powders were based on a formulation of paracetamol as the
pharmaceutical active ingredient. The reference method used to determine particle size distribution was sieving. Partial least
squares methods were used to estimate the multivariate regression models, and the results were compared in terms of figures
of merit. It was shown that the partial least squares methods gave similar prediction errors. Regarding the data blocks used,
the NIRS block was proven the most advantageous to estimate the particle size distribution. The prediction error of the NIRS
block was similar to the other data blocks with additional advantages such as less generalization problems and the possibility
of its use to predict additional physical and chemical properties with an improvement to analysis time. The multi-block approach
produced the worst results but nevertheless allowed a deeper understanding of the individual contributions of the data blocks
in the prediction of the particle size distribution. 相似文献
2.
Catherine Tessini Niels Müller Claudia Mardones Dietrich Meier Alex Berg Dietrich von Baer 《Journal of chromatography. A》2012
HPLC–UV and GC/MS determination of aldehydes in bio-oil were evaluated. HPLC–UV preceded by derivatization with 2,4-dinitrophenylhydrazine allows separation and detection of bio-oil aldehydes, but the derivatization affected the bio-oil stability reducing their quantitative applicability. GC/MS determination of aldehydes was reached by derivatization with o-(2,3,4,5,6-pentafluorobenzyl) hydroxylamine hydrochloride. Two approaches for this reaction were evaluated. The first: “in solution derivatization and head space extraction” and the second: “on fiber derivatization SPME”, the latter through an automatic procedure. Both sample treatments allows the quantification of most important aliphatic aldehydes in bio-oil, being the SPME approach more efficient. The aldehyde concentrations in bio-oil were ~2% formaldehyde, ~0.1% acetaldehyde and ~0.05% propionaldehyde. 相似文献
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Y Sun Y Du Y Liu L Chang Y Ren L Cao Q Sun X Shi Q Wang L Zhang 《Journal of separation science》2012,35(14):1796-1807
A novel quantitative method using high-performance liquid chromatography coupled to electrospray ionization tandem mass spectrometry was developed for simultaneous determination of the important active constituents including four steroidal saponins, two xanthone glycosides, two isoflavonoids, and one anthraquinone in different parts of Anemarrhena asphodeloides from different habitats. Hierarchical clustering analysis and principal components analysis were performed to differentiate and classify the samples. The separation was performed on a C(18) column with acidified aqueous acetonitrile gradients. Quantification of the analytes was achieved by use of a hybrid quadrupole linear ion-trap mass spectrometer. Multiple-reaction monitoring scanning was employed with switching electrospray ion source polarity between positive and negative modes in a single run. The validation results of the method indicated that the method was simple, rapid, specific, and reliable. The results demonstrated that the quantitative difference in content of nine active compounds was useful not only for chemotaxonomy of many samples from different sources but also for the standardization and differentiation of many similar samples. Simultaneous quantification of bioactive components by HPLC-ESI-MS coupled with chemometric techniques would be a well-acceptable strategy to comprehensively control the quality of A. asphodeloides. 相似文献
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A spectrofluorimetric method for the simultaneous determination of dysprosium, europium, gadolinium and terbium in ternary and quaternary mixtures by the use of pyridine-2,6-dicarboxylic acid as a chelating agent was developed. The influence of chemical variables affecting the analytical reaction was evaluated. A partial least-squares procedure and PC Quant software were used to assess data obtained from a variable number of calibration solutions and wavelengths. The ensuing method was validated by applying it to the analysis of synthetic ternary (Eu-Dy-Tb) and quaternary mixtures (Eu-Dy-Gd-Tb) over the concentration ranges 60-550 mug Eu l(-1), 30-400 mug Dy l(-1) and 30-400 mug Tb l(-1) in the former, and 20-220 mug Eu l(-1), 20-235 mug Dy l(-1), 25-230 mug Gd l(-1) and 75-230 mug Tb l(-1) in the latter. The results obtained by using the two quantitation procedures are compared. The relative errors in the determinations were less than 8% in most cases. 相似文献
6.
Matrix effect (ME) – ionisation suppression or enhancement – in liquid chromatography/electrospray ionisation mass spectrometry (LC/ESI‐MS) is caused by matrix components co‐eluting with the analytes. ME has a complex and not fully understood nature. ME is also highly variable from sample to sample making it difficult to compensate for. In this work it was studied whether the background ion signals in scanned mass spectra of the LC effluent at the retention time of the analyte offer some insight into the presence and extent of matrix effect. Matrix effects for six pesticides – thiabendazole, carbendazime, methomyl, aldicarb, imazalil and methiocarb – in garlic and onion samples used in the study varied from 1% (suppression 99%) to 127% (enhancement 27%) depending on the pesticide and sample. Also standards in solvent and solvent blanks were included in the study. The ions most strongly varying from sample to sample – and therefore best describing the changes in sample composition and ME – were selected for quantification according to principal component analysis (PCA) for all six pesticides under study. These ions were used to account for ME via partial least‐squares (PLS) regression. The calibration set was constructed from 19 samples and standards and the obtained calibration function was validated with seven samples and standards. The average errors from the test set were from 0.05 to 0.27 mg/kg for carbendazim and imazalil, respectively (the respective average pesticide concentrations were 0.22 and 0.88 mg/kg). The PLS results were significantly more accurate compared to the conventional solvent calibration resulting in average errors from 0.07 to 0.69 mg/kg for carbendazime and methiocarb, respectively. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
7.
Khoshayand MR Abdollahi H Shariatpanahi M Saadatfard A Mohammadi A 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2008,70(3):491-499
In this study, the simultaneous determination of paracetamol, ibuprofen and caffeine in pharmaceuticals by chemometric approaches using UV spectrophotometry has been reported as a simple alternative to using separate models for each component. Spectra of paracetamol, ibuprofen and caffeine were recorded at several concentrations within their linear ranges and were used to compute the calibration mixture between wavelengths 200 and 400 nm at an interval of 1 nm in methanol:0.1 HCl (3:1). Partial least squares regression (PLS), genetic algorithm coupled with PLS (GA-PLS), and principal component-artificial neural network (PC-ANN) were used for chemometric analysis of data and the parameters of the chemometric procedures were optimized. The analytical performances of these chemometric methods were characterized by relative prediction errors and recoveries (%) and were compared with each other. The GA-PLS shows superiority over other applied multivariate methods due to the wavelength selection in PLS calibration using a genetic algorithm without loss of prediction capacity. Although the components show an important degree of spectral overlap, they have been determined simultaneously and rapidly requiring no separation step. These three methods were successfully applied to pharmaceutical formulation, capsule, with no interference from excipients as indicated by the recovery study results. The proposed methods are simple and rapid and can be easily used in the quality control of drugs as alternative analysis tools. 相似文献
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Sedimentation Field-Flow Fractionation (SFFF), which is a one-phase chromatographic system, is shown to be a rapid and convenient method for the simultaneous determination of particle size and density in polydisperse colloidal samples. This can be done by a methodology based on the variation of the carrier solution density using various aqueous glycerol solutions having different concentrations. A polydisperse polyvinyl chloride (PVC) latex sample was used as a model colloid. The average diameters and densities found by the proposed methodology are in good agreement with those obtained from the normal. SFFF procedure using a carrier of constant density or given by the manufacturer. Number average, dN, and weight average, dw, particle diameters were determined for the PVC sample at various carrier solutions containing glycerol up to 40 % (w/w) in order to show whether sample aggregation has occurred or not in the presence of glycerol. In all cases, the ratio dw/dN was found to be constant, showing that PVC aggregation has not occurred. Therefore our results, obtained by the proposed methodology in SFFF, are accurate, showing that this approach has considerable promise for characterizing complex colloidal materials. 相似文献
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A simple and rapid method for the determination of particle size in emulsions from ultrasound data 总被引:2,自引:0,他引:2
Oil droplet size in emulsions can be determined from ultrasound velocity and attenuation spectra. We show that explicit solutions of the acoustic scattering matrix may be used to rapidly calculate a mean particle size for a limited but useful range of particle sizes. Our technique is well suited to in-line measurement. Both modelling and experiment indicate that the main scattering mechanism is thermal scattering. Calculations using the explicit solutions have been compared with experimental results from sunflower oil-in-water emulsions. 相似文献
13.
Laffort P Chauvin F Dallos A Callegari P Valentin D 《Journal of chromatography. A》2005,1100(1):90-107
An improvement in the characterization and the determination of the solvation parameters allows, not only a better knowledge of solutions, but also of some biological phenomena. In this paper, we test several published data and approaches in the field of solubility and solvation parameters in two ways: (i) the mutual independence of the parameters and (ii) their ability to take into account recently published gas-liquid chromatographic data. From this enquiry it arises that the most suitable published values are those of Abraham concerning 314 solutes. It also arises that the parameters of dispersion and orientation of this published data set are appreciably improved using two simple equations. In addition, a new set of optimized values for 133 solutes is given, by derivation from retention indices in gas-liquid chromatography (GLC) on five selected stationary phases, published by Kováts and co-workers and in the present study. The two sets have a total of 373 defined compounds. 相似文献
14.
Alumina sols were prepared using a modified Yoldas procedure, thus resulting in sols with high solids content, excellent long
term stability and small particle size. PH-value ranged between 3.7 and 0.6. Sols were characterised using rheological, UV-vis
transmission and particle size measurements. Depending on
molar ratio as well as solids content, sols vary. Analysis of reduced viscosities indicate the formation of chainlike polymeric
species above a critical solids fraction. 相似文献
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Ana M. Tarditi Noelia Barroso Agustín E. Galetti Luis A. Arrúa Laura Cornaglia María C. Abello 《Surface and interface analysis : SIA》2014,46(8):521-529
The surface properties of Ni/MgAl2O4 catalysts doped with Ce or Pr were analyzed by XPS after treatment in an inert and reductive atmosphere at 400 °C. The Ce‐promoted solids presented the Ce3+/Ce4+ couple on the surface even after treatment in a reductive atmosphere, H2(5%)/Ar. The promotion effect of Ce on these solids could be associated with their participation on the carbon deposition‐removal mechanism. Pr‐doped catalysts showed a very high concentration of Pr3+ under a reductive atmosphere and the redox behavior associated with the carbon removal could be partially inhibited or become slower. The size of the Ni0 particles after both an inert and a reductive atmosphere was estimated by XPS intensity ratio using the model proposed by Davis. The results obtained from the Davis model showed that an important increase occurred in Ni particle size after treatment in H2(5%)/Ar for the Pr‐promoted solids. The metal sintering under reductive atmosphere could be the reason for the higher loss of activity of the Pr‐doped solids under reforming conditions. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
17.
A number of powdered drugs and pharmaceutical excipients were used to demonstrate the ability of near-infrared spectroscopy to measure median particle size (d50). Sieved fractions and bulk samples of aspirin, anhydrous caffeine, paracetamol, lactose monohydrate and microcrystalline cellulose were particle sized by forward angle laser light scattering (FALLS) and scanned by fibre-optic probe FT-NIR spectroscopy. Two-wavenumber multiple linear regression (MLR) calibrations were produced using: NIR reflectance; absorbance and Kubelka-Munk function data with each of median particle size, reciprocal median particle size and the logarithm of median particle size. Best calibrations were obtained using reflectance data versus the logarithm of median particle size (NIR predicted lnd50 versus ln(FALLS d50) for microcrystalline cellulose and lactose monohydrate sieve fraction calibrations: r = 0.99 in each case). Working calibrations for lactose monohydrate (median particle size range: 19.2-183 microns) and microcrystalline cellulose (median particle size range: 24-406 microns) were set-up using combinations of machine sieve-fractions and bulk samples. This approach was found to produce more robust calibrations than just the use of sieved fractions. The method has been compared with single wavenumber quadratic least squares regression using reflectance and mean-corrected reflectance data with median particle size. Correlation between NIR predicted and FALLS values was significantly better using the MLR method. 相似文献
18.
K. I. Schiffmann Matthias Fryda Günther Goerigk Rolf Lauer Peter Hinze 《Analytical and bioanalytical chemistry》1997,358(1-2):341-344
Metal containing amorphous hydrocarbon films consist of nanometer size metallic particles in a hydrogen-carbon matrix. Scanning tunneling microscopy (STM) of Au and Pt containing amorphous C:H-films was performed in order to determine particle size- and distance distributions. To correct tip convolution effects, which lead to apparent particle enlargement and particle hiding (1) a method is presented which allows off-line STM tip radius determination by statistical analysis of apparent particle radii and thereby a correct particle radii determination. (2) A simple Monte Carlo model is proposed to compute fractions of hidden particles and their influence on particle distance distributions. Results of these evaluations are compared with results from small angle X-ray scattering (SAXS), transmission electron microscopy (TEM) and X-ray diffraction (XRD). 相似文献
19.
Simple and sufficiently accurate equations are suggested for calculating the particle size of most frequently used supported or unsupported platinum metal catalysts from the amount of chemisorbed gas.
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