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Linear Calibration (linear + calibration)
Terms modified by Linear Calibration Selected AbstractsApplication of FAIMS to anabolic androgenic steroids in sport drug testingDRUG TESTING AND ANALYSIS, Issue 11-12 2009Sven Guddat Abstract Mass spectrometric identification of anabolic androgenic steroids challenges standard doping-control methods. To reveal a doping offence the presence of prohibited anabolic androgenic steroids at trace levels in the picogram-per-millilitre range must be confirmed as reliable. Human urine samples containing epitrenbolone, metandienone metabolite (17, -hydroxymethyl-17,-methyl-18-norandrost-1,4,13-trien-3-one), stanozolol, 16,-hydroxystanozolol and 4,-hydroxystanozolol were analysed using LC-FAIMS-MS/MS. These substances are prohibited in sport according to World Anti-Doping Agency (WADA) regulations. Glucuronides were hydrolysed and prepared by liquid-liquid extraction. Excellent recovery and precision were obtained for all compounds. Linear calibration results for epitrenbolone and metandienone metabolite were obtained and concentration information could be determined in the ranges of reliable response between 750,1200 and 100,600 pg/mL, respectively. Limits of detection were estimated at 25 pg/mL (stanozolol), 50 pg/mL (metandienone metabolite, 16,-hydroxystanozolol), 100 pg/mL (4,-hydroxystanozolol) and 500 pg/mL (epitrenbolone). The assay was applied to doping-control samples. For all analytes, LC-FAIMS-MS/MS resulted in excellent interference removal, which effectively extends the post-dose detection time. Copyright © 2009 John Wiley & Sons, Ltd. [source] Analysis of Rhizoma Polygoni Cuspidati by HPLC and HPLC-ESI/MSPHYTOCHEMICAL ANALYSIS, Issue 5 2007Tao Yi Abstract An HPLC method with photodiode array detection (PAD) and ESI/MS detection was developed for the qualitative and quantitative analysis of the major chemical constituents of the dried rhizome of Polygonum cuspidatum Sieb. et Zucc. (Rhizoma Polygoni Cuspidati; Chinese name Hu-Zhang). Based on the chromatographic separation on an Altima C18 column using 0.5% aqueous acetic acid and acetonitrile as the mobile phase, nine compounds, including stilbenes, stilbene glucosides, anthraquinones and anthraquinone glucosides, were identified by online ESI/MS analysis and seven were quantified by HPLC-PAD. A full validation of the method including sensitivity, linearity, repeatability and recovery was conducted. Linear calibration was achieved over the concentration range 1,200 mg/L with R2 > 0.999, whilst the limits of detection ranged from 0.51 to 1.57 ng. Repeatability was evaluated by intra- and inter-day assays and the RSD value was within 1.79%. Recoveries of the quantified compounds were within the range 96.0,100.1% with RSD values of less than 2.2%. Five samples of Rhizoma Polygoni Cuspidati from different regions were analysed using the developed method. The major constituents piceid, resveratrol, emodin-8- O - , - d -glucoside and emodin were selected to provide an index for the quality assessment of the herbal drug. Copyright © 2007 John Wiley & Sons, Ltd. [source] Determination of uranium, iron, copper, and nickel from ore samples by MEKC using N,N,-ethylene bis(salicylaldimine) as complexing reagentELECTROPHORESIS, Issue 3 2008Muhammed Aslam Mirza Abstract An analytical procedure has been developed for the separation of dioxouranium(VI), iron(III), copper(II), nickel(II), cobalt(II), cobalt(III), palladium(II), and thorium(IV) by MEKC using N,N,-ethylene bis(salicylaldimine) (H2SA2en) as a complexing reagent with total runtime <4.5,min. SDS was used as micellar medium at pH,8 with sodium tetraborate buffer (0.1,M). An uncoated fused-silica capillary with an effective length of 50,cm×75,,m id was used with an applied voltage of 30,kV with photodiode array detection at 231,nm. Linear calibrations were obtained within 0.111,1000,,g/mL of each element with LODs within 37,325,ng/mL. The developed method was tested for analysis of uranium ore samples indicating its presence within 103,1789,,g/g with RSD within 0.79,1.87%. Likewise copper, nickel, and iron in their combined matrix were also simultaneously determined with RSD 0.4,1.6% (n,=,6). [source] The evolution of volatile compounds profile of "Toscano" dry-cured ham during ripening as revealed by SPME-GC-MS approach,JOURNAL OF MASS SPECTROMETRY (INCORP BIOLOGICAL MASS SPECTROMETRY), Issue 9 2010C. Pugliese Abstract The volatile compounds profile is an important feature for the characterization of dry-cured hams. Some minor typical Italian products, such as ,Toscano' ham, have been poorly studied in regards to their composition of volatile compounds. In this article, we studied the evolution of the aromatic profile of ,Toscano' dry-cured ham by solid-phase microextraction-gas chromatographic-mass spectrometry (SPME-GC-MS) with ripening. Ten right thighs were cured according to the ,Toscano' PDO protocol, sampled at 0, 1, 3, 6 and 12 months and submitted to volatile compounds analysis by SPME with a Divinylbenzene (DVB)/Carboxen/Polydimethylsiloxane (PDMS) 75-µ Stable Flex fibre. An Agilent 5975C mass selective detector (MSD) spectrometer with electron ionization (EI) source operating in scan mode within the m/z 29,350 range was used for data collection. Seven internal standards, either deuterium labeled or absent in the specimens and chosen to represent low or high boiling esters, alcohols, acids or phenols, were added to the homogenized samples and used to normalize the SPME fibre response to account for response changes upon wearing. Linear calibrations were obtained in this way for selected representative compounds. Over 60 compounds belonging to esters, aldehydes, organic acids, ketones and alcohols were identified by comparison with spectral libraries and Kovats indices. Aldehydes were the most represented chemical family, followed by organic acids, alcohols, ketones and esters. The aldehydes and ketones increased during the first 3 months, when the larger formation of volatiles occurred. For other families, the evolution over time was less evident. The principal component and discriminant analyses of the aromatic profile were effective in classifying the hams at 0, 6 or 12 months of ripening while for 1 and 3 months' samples a partial overlapping was shown. These results represent the first characterization of ,Toscano' ham and may constitute the basis to identify the best ripening time and define an analytical quality standard for this typical ham. Copyright © 2010 John Wiley & Sons, Ltd. [source] An In Situ Device to Measure Oxygen in the Vadose Zone and in Ground Water: Laboratory Testing and Field EvaluationGROUND WATER MONITORING & REMEDIATION, Issue 2 2008Bradley M Patterson Oxygen probes developed to measure in situ oxygen concentrations in gaseous and aqueous environments were evaluated in laboratory tests and during long-term field evaluation trials at contaminated sites. The oxygen probes were shown to have a linear calibration and to be accurate compared to conventional dissolved oxygen electrodes and gas chromatography, both of which require labor-intensive sample collection and processing. The probes, once calibrated, required no maintenance or recalibration for up to a period of 7 years in low-oxygen environments, demonstrating long-term stability. Times to achieve 90% of the stabilized concentration (t90) after a step change in aqueous oxygen concentration were 100,120 min in laboratory experiments and up to 180 min in field experiments, which is adequate for monitoring subsurface changes. Field application data demonstrated that the oxygen probes could monitor oxygen concentrations in hydrocarbon-contaminated ground water to a depth of 20 m below the water table or in pyritic vadose zones over extended periods. During bioremediation field trials, oxygen monitoring enabled estimation of oxygen utilization rates by microorganisms and hydrocarbon biodegradation rates. Also, probes were able to monitor the development of ground water desaturation during air sparging trials, enabling the automated assessment of the distribution of injected air. [source] Skew-normal linear calibration: a Bayesian perspectiveJOURNAL OF CHEMOMETRICS, Issue 8 2008Cléber da Costa Figueiredo Abstract In this paper, we present a Bayesian approach for estimation in the skew-normal calibration model, as well as the conditional posterior distributions which are useful for implementing the Gibbs sampler. Data transformation is thus avoided by using the methodology proposed. Model fitting is implemented by proposing the asymmetric deviance information criterion, ADIC, a modification of the ordinary DIC. We also report an application of the model studied by using a real data set, related to the relationship between the resistance and the elasticity of a sample of concrete beams. Copyright © 2008 John Wiley & Sons, Ltd. [source] Multivariate calibration of covalent aggregate fraction to the raman spectrum of regular human insulinJOURNAL OF PHARMACEUTICAL SCIENCES, Issue 9 2008Connie M. Gryniewicz Abstract Insulin aggregates were prepared by exposing samples of formulated regular human insulin to agitation at 60°C. Aliquots were drawn from the samples periodically over a time range spanning 192 h, and their aggregate compositions were determined with size exclusion chromatography. The complete data set was composed of 39 separate aliquots. The Raman spectra of three separate 10 µL volumes from each aliquot were measured using the drop-coat deposition Raman (DCDR) method. The spectra were calibrated to aggregate composition by partial least squares regression (PLS), resulting in linear calibration (R2,=,0.997) with a root mean squared error of calibration (RMSEC) of 1.3% and a root mean squared error of cross validation (RMSECV) of 5.1% in aggregate composition. Though the time required for aggregates to form under stressed conditions showed substantial sample-to-sample variation, the correlation between aggregate composition and Raman spectrum was remarkably consistent, indicating that Raman spectroscopy may be a viable screening method for aggregation of protein drugs. © 2008 Wiley-Liss, Inc. and the American Pharmacists Association J Pharm Sci 97:3727,3734, 2008 [source] | ||||||||||