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Calibration Lines (calibration + line)
Selected AbstractsQuantitative analysis of an oligomeric hindered amine light stabilizer in polypropylene by matrix-assisted laser desorption/ionization mass spectrometry using a solid sampling techniqueRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 8 2006Yoshihiko Taguchi A small amount of an oligomeric hindered amine light stabilizer (HALS) (Adekastab LA-68LD) in polypropylene (PP) materials was directly determined by solid sampling matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS) using an internal standard method. First the matrix reagent (dithranol), 20,mg, and the empirically selected internal standard, angiotensin I (MW,=,1296.5), 5,µg, were premixed in the solid state. The matrix mixture was then co-ground with the PP sample containing the HALS in liquid nitrogen using a freezer mill. The powdered sample mixture was spotted on the sample plate, suspended in ion-exchanged water, dried to adhere on the plate, and subjected to MALDI-MS. Three series of the HALS components accompanied by the oxidized species were clearly observed as their molecular ions (M.+) along with that of the internal standard in the mass spectra. A fairly good linear relationship (R2,=,0.9991) with a relative standard deviation of ca. 11% was observed between the relative peak intensities of the HALS components and the HALS contents ranging from 0.1,2.5,wt%, which could be used as the calibration line to determine the HALS content in PP composites directly by MALDI-MS. The UV-exposed PP composite samples were evaluated by this method to interpret the photostabilizing action of HALS in the PP materials based on the observed change in the relative abundances of the original and oxidized HALS components as a function of UV-exposure time. Copyright © 2006 John Wiley & Sons, Ltd. [source] Determination of the operational pH value of a buffering membrane by an isoelectric trapping separation of a carrier ampholyte mixtureELECTROPHORESIS, Issue 5 2008Robert Y. North Abstract The operational pH value of a buffering membrane used in an isoelectric trapping separation is determined by installing the membrane as the separation membrane into a multicompartmental electrolyzer operated in the two-separation compartment configuration. A 3 Oxygen isotope analysis of phosphate: improved precision using TC/EA CF-IRMS,JOURNAL OF MASS SPECTROMETRY (INCORP BIOLOGICAL MASS SPECTROMETRY), Issue 6 2009D. F. LaPorte Abstract Oxygen isotope values of biogenic apatite have long demonstrated considerable promise for paleothermometry potential because of the abundance of material in the fossil record and greater resistance of apatite to diagenesis compared to carbonate. Unfortunately, this promise has not been fully realized because of relatively poor precision of isotopic measurements, and exceedingly small size of some substrates for analysis. Building on previous work, we demonstrate that it is possible to improve precision of ,18OPO4 measurements using a ,reverse-plumbed' thermal conversion elemental analyzer (TC/EA) coupled to a continuous flow isotope ratio mass spectrometer (CF-IRMS) via a helium stream [Correction made here after initial online publication]. This modification to the flow of helium through the TC/EA, and careful location of the packing of glassy carbon fragments relative to the hot spot in the reactor, leads to narrower, more symmetrically distributed CO elution peaks with diminished tailing. In addition, we describe our apatite purification chemistry that uses nitric acid and cation exchange resin. Purification chemistry is optimized for processing small samples, minimizing isotopic fractionation of PO4,3 and permitting Ca, Sr and Nd to be eluted and purified further for the measurement of ,44Ca and 87Sr/86Sr in modern biogenic apatite and 143Nd/144Nd in fossil apatite. Our methodology yields an external precision of ± 0.15, (1,) for ,18OPO4. The uncertainty is related to the preparation of the Ag3PO4 salt, conversion to CO gas in a reversed-plumbed TC/EA, analysis of oxygen isotopes using a CF-IRMS, and uncertainty in constructing calibration lines that convert raw ,18O data to the VSMOW scale. Matrix matching of samples and standards for the purpose of calibration to the VSMOW scale was determined to be unnecessary. Our method requires only slightly modified equipment that is widely available. This fact, and the demonstrated improvement in precision, should help to make apatite paleothermometry far more accessible to paleoclimate researchers. Copyright © 2009 John Wiley & Sons, Ltd. [source] Monitoring of biomass composition from microbiological sources by means of FT-IR spectroscopyBIOTECHNOLOGY & BIOENGINEERING, Issue 1 2009Arthur M.A. Pistorius Abstract An FT-IR spectroscopic method was developed for the simultaneous quantitative analysis of biomacromolecular components in biomass, originating from various microbiological sources. For the determination of protein, lipid and carbohydrate content, creatine phosphokinase, egg phosphatidyl choline and starch hydrolysate were chosen as external standards. This selection was based on spectral similarity and ease of availability. Protein content was based on the area under the amide II band profile around 1,545 cm,1. Because of the heterogeneous lipid composition in the different species, lipid content was determined using integration over the CH stretching vibrational population between 2,984 and 2,780 cm,1. Carbohydrate content was determined using integration over a CO and COC stretching band area between 1,180 and 1,133 cm,1. Linear regression analysis provided three calibration lines, according to which biomasses from ten species were analyzed. This approach showed good intra-batch reproducibility. With this method we could demonstrate good reproducibility between batches of the same species with similar growth conditions while large differences in biomass composition were observed between the various species. Protein content as determined by FT-IR spectroscopy compared well with the results obtained from elemental analysis. Biotechnol. Bioeng. 2009;103: 123,129. © 2008 Wiley Periodicals, Inc. [source]
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