|
| ||
|
|
||
Calibration Equation (calibration + equation)
Selected AbstractsPreliminary study on the use of near-infrared reflectance spectroscopy to assess nitrogen content of undried wheat plantsJOURNAL OF THE SCIENCE OF FOOD AND AGRICULTURE, Issue 1 2007Alejandro Morón Abstract Near-infrared reflectance (NIR) spectroscopy combined with chemometrics was used to assess nitrogen (N) and dry matter content (DM) and chlorophyll in whole-wheat plant (Triticum aestivum L). Whole-wheat plant samples (n = 245) were analysed by reference method and by visible and NIR spectroscopy, in fresh (n = 182) and dry (n = 63) presentations, respectively. Calibration equations were developed using partial least squares (PLS) and validated using full cross-validation (leave-one-out method). Coefficient of determination in calibration (R2CAL) and the standard error of cross-validation (SECV) for N content in fresh sample presentation, after second derivative, were 0.89 (SECV: 0.64%), 0.86 (SECV: 0.66%) and 0.82 (SECV: 0.74%) using the visible + NIR, NIR and visible wavelength regions, respectively. Dry sample presentation gave better R2CAL and SECV for N compared with fresh presentation (R2CAL > 0.90, SECV < 0.20%) using visible + NIR. The results demonstrated that NIR is a suitable method to assess N concentration in wheat plant using fresh samples (unground and undried). Copyright © 2006 Society of Chemical Industry [source] Electrocatalysis and determination of uracil on polythionine/multiwall carbon nanotubes modified electrodeJOURNAL OF APPLIED POLYMER SCIENCE, Issue 5 2008Hongying Liu Abstract A new type of poly (thionine)/multiwall carbon nanotube/glassy carbon (PTH/MWNTs/GC) electrode was fabricated by electropolymerization thionine onto the surface of MWNTs modified GC electrode. The properties and behaviors of the modified electrode were characterized by scanning electron microscopy (SEM) and cyclic voltammetry (CV). The results show that the high sensitivity and selectivity are mainly caused by the unique carbon surface of the carbon nanotubes and the catalytic activity of thionine. The modified electrode exhibited excellent electrocatalytic behavior to the oxidation of uracil, and was firstly applied to determinate the concentration of uracil for the differential pulse voltammograms. Under the optimum conditions, linear calibration equation was obtained over the uracil concentration range from 1.0 × 10,5 to 5.5 × 10,2M with a correlation coefficient of 0.9978 and a detection limit 2.0 × 10,7M (based on S/N = 3) was also gained. The good electrocatalytic response of uracil at PTH/MWNTs/GC electrode suggests that the PTH/MWNTs are an excellent platform for electrochemical biosensing. The modified electrode displays excellent repeatability, stability, and high sensitivity. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 [source] Modified calculations of hydrocarbon thermodynamic propertiesJOURNAL OF COMPUTATIONAL CHEMISTRY, Issue 5 2006Min Hsien Liu Abstract A test set of 65 hydrocarbons was examined to elucidate theoretically their thermodynamic properties by performing the density-functional theory (DFT) and ab initio calculations. All the calculated data were modified using a three-parameter calibration equation and the least-squares approach, to determine accurately enthalpies of formation (,Hf), entropies (S), and heat capacities (Cp). Calculation results demonstrated that the atomization energies of all compounds exhibited an average absolute relative error ranging between 0.11, 0.13%, and an ,Hf of formation with a mean absolute absolute error (M.|A.E.|) ranging from only 5.7,6.8 kJ/mol (1.3,1.6 kcal/mol) (i.e., those results correlated with those of Dr. Herndon's 1.1 kcal/mol). Additionally, the entropy ranged from 3.5,4.2 J/mol K (0.8,1.0 cal/mol K) M.|A.E.|; a heat capacity between 2.3,2.9 J/mol K (0.5,0.7 cal/mol K) M.|A.E.| was obtained as well. © 2006 Wiley Periodicals, Inc. J Comput Chem 27: 537,544, 2006 [source] Reclassification and thermal history of Trenzano chondriteMETEORITICS & PLANETARY SCIENCE, Issue 12 2007A. M. FIORETTI The quenched intracrystalline Fe2+ -Mg ordering state in orthopyroxene preserves the memory of the cooling rate near closure temperature Tc, thus yielding useful constraints on the last thermal event undergone by the host rock. The orthopyroxene Tc of 522 ± 13 °C, calculated using a new calibration equation obtained by Stimpfl (2005b), is higher than in previously published H chondrite data. The orthopyroxene cooling rate at this Tc is about 100 °C/kyr. This fast rate is inconsistent with the much slower cooling rate expected for H6 in the onion shell structural and thermal model of chondrite parent bodies. A petrographic study carried out at the same time indicated that the Trenzano meteorite is an H5 chondrite and not an H6 chondrite, as it is officially classified. Furthermore, the two-pyroxene equilibrium temperature of Trenzano (824 ± 24 °C), calculated with QUILF95, is similar to the two-pyroxene temperature of 750,840 °C obtained for the Carcote (H5) chondrite (Kleinschrot and Okrusch 1999). [source] Authentication of Green Asparagus Varieties by Near-Infrared Reflectance SpectroscopyJOURNAL OF FOOD SCIENCE, Issue 2 2001D.P. Perez ABSTRACT: Near-infrared reflectance spectroscopy (NIRS) was used for the authentication of 2 green asparagus varieties (Taxara and UC-157), grown in Huetor-Tajar (Granada, Spain) protected by the Quality Specific Appellation "Espárragos de Huétor-Tájar". To develop the prediction model, the method chosen was modified partial least square (MPLS) regression. Two sample sets (N = 219 and N2 = 145 samples, respectively) were used to obtain the calibration equations. The standard error of cross-validation (SECV) and the r2 value were 0.082 and 0.97, respectively, for the 1st calibration set and 0.077 and 0.97 for the 2nd calibration set. The 2nd chemometric model obtained was tested with independent validation sample set (N3 = 74 samples), and the resulting values for standard error of prediction (SEP) and for r2 were 0.07 and 0.96, respectively. These results prove that NIRS is an accurate technology for identification and authentication of asparagus varieties and easily implemented in industry. [source] A near-infrared method for the assay of cineole in eucalyptus oil as an alternative to the official BP methodJOURNAL OF PHARMACY AND PHARMACOLOGY: AN INTERNATI ONAL JOURNAL OF PHARMACEUTICAL SCIENCE, Issue 1 2001Nicola D. Wilson Eucalyptus oil of British Pharmacopoeia (BP) and European Pharmacopoeia standard must contain not less than 70.0% w/w 1,8-cineole (eucalyptol). The official assay is a freezing-point method which involves the addition of o -cresol to the eucalyptus oil, whereupon the o -cresol and the 1,8-cineole form a solid complex. The assay has several disadvantages and we aim to show that near-infrared (NIR) spectroscopy is an attractive alternative to this method, in that it is simple to use, requires no sample preparation and is potentially as accurate as the traditional method. Thirty different eucalyptus oil samples were scanned on the FOSS NIRSystems 6500 Rapid Content Sampler using a reflectance vessel as sample presentation method. The cineole content of each sample was determined by the BP method and these reference data were used to construct two calibration equations for cineole content in the oils using Vision software. The mean accuracy for the NIR method differed by 1.01% or less, and the mean bias by ±0.33% or less, compared with the BP method. Calculation of the 95% confidence intervals for the slope and intercept of plots of NIR predicted values against BP method reference values showed that there was no evidence of fixed or relative systematic errors. Tests for short-term and intermediate repeatability were conducted. The standard deviation was 0.83% w/w or less and the coefficient of variation was 1.11% or less. The confidence intervals for both short-term and intermediate repeatability overlapped with that for the BP method, suggesting that there was no evidence for a difference in values obtained by the BP and NIR methods. The range of cineole contents used in the calibrations was extended by incorporating five samples of eucalyptus oil spiked with cineole, and five samples of two essential oils known to have a lower cineole content than eucalyptus oil, to give a range of 52.5 to 99.0% w/w. The mean accuracy decreased to an error of 1.26% or less and the bias to ±0.50% or less. Again, confidence intervals suggested there was no evidence for fixed or systematic errors in the NIR calibrations. We propose that NIR spectroscopy could be used as an alternative method for the determination of cineole content in eucalyptus oils. [source] Validated analysis of fluvastatin in a pharmaceutical capsule formulation and serum by capillary electrophoresisBIOMEDICAL CHROMATOGRAPHY, Issue 6 2001Dilek Do, rukol-Ak The capillary electrophoretic behavior and the determination of fluvastatin (FLU) in capsule and serum is described in this study. Method development was conducted in a fused-silica capillary (L,=,86,cm, Leff,=,58,cm and 75,µm i.d.) and a background electrolyte consisting of 10,mM borate at pH 8 was used. The separation was performed by current-controlled system applying 41,µA, detecting at 239,nm and injecting 0.5,s vacuum injection. A good electropherogram and excellent repeatability was obtained. FLU and phenobarbital sodium (internal standard) migrated (with RSD%) at 4.8 (0.3),min and 5.2 (0.6),min, respectively. Limit of detection (LOD) and limit of quantitation (LOQ) values were found to be 1,×,10,6,M and 2.89,×,10,6,M, respectively. Linearity in the range of 1.03,×,10,5 ,5.15,×,10,5 M was examined employing intra-day and inter-day studies and well-correlated calibration equations were obtained. FLU in a capsule (Lescol® 40,mg declared) was found to be 41.9,±,0.4,mg. Furthermore, FLU was determined in serum applying standard addition technique. Good repeatability and no interference were observed. The method proposed is simple, sensitive, precise and easy to use for the determination of FLU in capsule and serum. Copyright © 2001 John Wiley & Sons, Ltd. Abbreviations used: FLU fluvastatin HMG-CoA hydroxymethylglutaryl coenzyme [source] | ||||||||||