Home About us Contact
|
Home About us Contact | ||
|
|
||
Spectral Interference (spectral + interference)
Selected AbstractsAccounting for co-extractable compounds (blank correction) in spectrophotometric measurement of extractable and total-bound proanthocyanidin in Leucaena sppJOURNAL OF THE SCIENCE OF FOOD AND AGRICULTURE, Issue 8 2002Scott A Dalzell Abstract Methods to account for the spectral interference of co-extractable compounds (blank correction) in the spectrophotometric analysis of both extractable and bound proanthocyanidin (PA) using the proanthocyanidin (butanol/HCl) assay were evaluated. Crude extractable and bound PA sample matrices of PA-free Leucaena magnifica were used. Extractable PA blanks generated in heated 95% butanol/5% H2O reagent underestimated the optical density (absorbance) of co-extractable compounds by 24% (P,<,0.01), whereas unheated 95% butanol/5% HCl blanks, incubated at room temperature, accurately measured the absorbance of the background matrix (P,<,0.01). Current procedures that estimate bound PA concentrations using the proanthocyanidin assay produce intensely coloured background matrices. Recovery measurements from total-bound PA extracts spiked with 1071 and 2142,µg anthocyanidin per tube indicated that existing analytical procedures that do not account for the spectral interference of co-extractable compounds overestimated (P,<,0.01) bound PA concentrations by 69 and 38% respectively. An innovative technique that generated an internal correction factor for each sample, using wavelength-scanning spectrophotometry and non-linear curve-fitting computer software, was developed. This procedure recovered 100% of added anthocyanidins from bound PA matrices. © 2002 Society of Chemical Industry [source] In vivo 13C magnetic resonance spectroscopy of human brain on a clinical 3 T scanner using [2- 13C]glucose infusion and low-power stochastic decouplingMAGNETIC RESONANCE IN MEDICINE, Issue 3 2009Shizhe Li Abstract This study presents the detection of [2- 13C]glucose metabolism in the carboxylic/amide region in the human brain, and demonstrates that the cerebral metabolism of [2- 13C]glucose can be studied in human subjects in the presence of severe hardware constraints of widely available 3 T clinical scanners and with low-power stochastic decoupling. In the carboxylic/amide region of human brain, the primary products of 13C label incorporation from [2- 13C]glucose into glutamate, glutamine, aspartate, ,-aminobutyric acid, and N-acetylaspartate were detected. Unlike the commonly used alkanyl region where lipid signals spread over a broad frequency range, the carboxylic carbon signal of lipids was found to be confined to a narrow range centered at 172.5 ppm and present no spectral interference in the absence of lipid suppression. Comparison using phantoms shows that stochastic decoupling is far superior to the commonly used WALTZ sequence at very low decoupling power at 3 T. It was found that glutamine C1 and C5 can be decoupled using stochastic decoupling at 2.2 W, although glutamine protons span a frequency range of ,700 Hz. Detailed specific absorption rate analysis was also performed using finite difference time domain numerical simulation. Magn Reson Med, 2009. © 2009 Wiley-Liss, Inc. [source] Comparison of Artificial Neural Networks with Partial Least Squares Regression for Simultaneous Determinations by ICP-AESCHINESE JOURNAL OF CHEMISTRY, Issue 11 2007Mohamad KHAYATZADEH MAHANI Abstract Simultaneous determination of several elements (U, Ta, Mn, Zr and W) with inductively coupled plasma atomic emission spectrometry (ICP-AES) in the presence of spectral interference was performed using chemometrics methods. True comparison between artificial neural network (ANN) and partial least squares regression (PLS) for simultaneous determination in different degrees of overlap was investigated. The emission spectra were recorded at uranium analytical line (263.553 nm) with a 0.06 nm spectral window by ICP-AES. Principal component analysis was applied to data and scores on 5 dominant principal components were subjected to ANN. A 5-5-5 (input, hidden and output neurons) network was used with linear transfer function after both hidden and output layers. The PLS model was trained with five latent variables and 20 samples in calibration set. The relative errors of predictions (REP) in test set were 3.75% and 3.56% for ANN and PLS respectively. [source] Coprecipitation with calcium hydroxide for determination of iron in fish otoliths by collision cell ICP-MS,JOURNAL OF MASS SPECTROMETRY (INCORP BIOLOGICAL MASS SPECTROMETRY), Issue 5 2007Stephanie L. Daniels Abstract A method has been described for the determination of iron from fish otoliths containing high levels of calcium by collision cell technology (CCT) ICP-MS. Iron (Fe) in otolith solutions was quantitatively coprecipitated with small amounts of calcium hydroxide by adding 1.0 M sodium hydroxide solution. The performance of CCT-ICP-MS pressurized with He/H2 cell gas was investigated on the elimination of Ca-based spectral interferences at m/z 54, 56 and 57. Molecular ion interferences at m/z 54 and 56 were reduced by 2 orders of magnitude. However, the interferences at m/z 57 increased by the same amount in the presence of Ca in solutions owing to the formation of 40Ca16 OH+ through reactions with H2 in collision cell, indicating that 57Fe was not suitable for the determination of Fe from otoliths. Results for 56Fe suffered significantly from interferences of Ca-based molecular ions when the Ca concentration in solution exceeded 100 µg ml,1, for which matrix-matched calibration was required for accurate determination. CCT with the aid of He/H2 cell gas proved to be very effective in eliminating the interferences (40Ar14N+ and 40Ca14N+) at m/z 54. Presence of Ca up to 300 µg ml,1 had virtually no effect on the ion signals of 54Fe, which with low background signals, afforded accurate determination of Fe from otoliths by using aqueous external standards. Copyright © 2007 John Wiley & Sons, Ltd. [source] | ||||||||||