Quality Control of Ayurvedic Medicines
D. Suresh Kumar in Ayurveda in the New Millennium, 2020
Shifts in chromatographic retention time interfere with fingerprint analysis. They are caused by successive degradation of the stationary phase, minor changes in the composition of the mobile phase, detector and other instrumental shifts, column overloading or interactions between analytes. To avoid erroneous results, these shifts need to be corrected before the evaluation of similarities and differences between chromatograms (Li et al. 2004a; Liang et al. 2004; Wenzig and Bauer 2009). Peak synchronization is achieved by several methods. A useful method is the addition of an internal standard (Liang et al. 2004). Retention time can be corrected mathematically using local least square analysis or spectral correlative chromatography (Li et al. 2004b; 2004c).
Planar Chromatography
Joseph Chamberlain in The Analysis of Drugs in Biological Fluids, 2018
Using the ascending technique, the paper can be formed into a cylinder and placed with its lower 1 to 2 cm in the mobile phase a few centimeters away from the spotted sample. This method takes longer than the equivalent descending system, particularly if a heavy solvent such as dichloromethane is used in the mobile phase. Although this simple type of paper chromatography would appear to be absorption chromatography, there is usually sufficient water absorbed into the cellulose fibers to make the separation depend partly on an organic-aqueous partition. To make the chromatography more reproducible, and to make the system completely liquid-liquid partition, the paper is usually pre-equilibrated with the vapor of the stationary phase, which should be saturated with the mobile phase. The usual practice is to enclose the whole system in an airtight jar containing a mixture of the phases, and after a suitable period of equilibration, perform the elution with the mobile phase saturated with the stationary phase. For partition chromatography, temperature can be critical, and even in modern, temperature-controlled laboratories, local air currents can distort the flow of the mobile phase, making the chromatography irreproducible. Thus, most paper chromatography requires temperature control, usually by placing the solvent tank in an incubator. This not only allows reproducible chromatography, but the mass transfer between phases is also more rapid and chromatographic efficiency is improved.
Analysis and Interpretation
John M. Wayne, Cynthia A. Schandl, S. Erin Presnell in Forensic Pathology Review, 2017
Answer A is incorrect. Gas chromatography has many uses in forensics but is primarily used in the determination of low molecular weight volatiles such as ethanol. It is not useful for determining trace elements such as selenium. Gas chromatography uses a mobile phase and a stationary phase. The mobile phase or gas phase consists of an inert carrier gas such as nitrogen. The stationary phase consists of a solid support material coated by a waxy substance. The test substance is injected into the instrument where it separates into its components and interacts with the stationary phase. The components then elute or come off of the stationary phase at different times and a plot is made of the times. The retention time is used to identify the compounds in question.
Prevalence of Hemoglobinopathies (β-Thalassemia and Sickle Cell Trait) in the Adult Population of Al Majma’ah, Saudi Arabia
Published in Hemoglobin, 2020
Shabir A. Mir, Bader M. Alshehri, Mohammed Alaidarous, Saeed S. Banawas, Abdul Aziz A. Bin Dukhyil, Mohammad K. Alturki
In the present retrospective study, 3755 cases were analyzed for Hb variants at the premarital screening laboratory of KKGH, Al Majma’ah, Saudi Arabia. Clinical data of Saudi adults who voluntarily attended premarital screening from 1 October 2016 to 30 September 2019 were obtained and analyzed. Subjects with a recent history of transfusion, i.e. within 3 months before sample collection, were excluded from the study. Fresh whole blood (3 mL) collected in EDTA-containing tubes was the clinical specimen. All study samples were processed and stored at ambient temperature and analyzed within 48 h after collection. Cation-exchange high-performance liquid chromatography (HPLC) was used for screening, detection and identification of various hemoglobinopathies in the study subjects [11]. Each specimen was subjected to complete blood count (CBC) and analyzed on the VARIANT II™ cation-exchange HPLC system using the β-Thalassemia Short Program (Bio-Rad Laboratories, Hercules, CA, USA). Hemoglobin concentration (%) was calculated by determining the ratio of the area of a peak to the total area of all Hb peaks, as observed on a standard cation-exchange HPLC chromatogram. The retention time was measured in minutes. Hematological tests for CBC were performed using an automated hematology analyzer.
Heparin chromatography as an in vitro predictor for antibody clearance rate through pinocytosis
Published in mAbs, 2020
Thomas E. Kraft, Wolfgang F. Richter, Thomas Emrich, Alexander Knaupp, Michaela Schuster, Andreas Wolfert, Hubert Kettenberger
Analytical FcRn affinity chromatography was performed using a commercially available FcRn affinity column (Part No. 08128057001, Roche), pre-equilibrated with 80% buffer A (20 mM MES sodium salt, 140 mM NaCl, pH 5.5) and 20% buffer B (20 mM Tris/HCl, 140 mM NaCl, pH 8.8) at a flow rate of 0.5 mL/min and a column temperature of 25°C. Samples were prepared as above. A total of 30 µg protein was injected. Ten minutes post injection, a linear gradient from 20% to 100% buffer B over 70 min was started. One hundred percent buffer B was held for 10 min before the column was re-equilibrated with 80% buffer A and 20% buffer B. Detection was performed with a UV detector set at 280 nm. In order to make results from different runs and different buffer and column lots comparable, and to compensate for slight retention time drifts, a standard sample was measured at the beginning and the end of each sequence and after every 10th run. The relative retention time (Equation 2.
Removal efficiency of PAH’s from five wastewater treatment plants in Jordan
Published in Toxin Reviews, 2018
Mahmoud A. Alawi, Ibrahim N. Tarawneh, Zahra’ Ghanem
There are two ways for the qualitative and quantitative analysis in GC-MS, the full scan mode and the selected ion monitoring (SIM) mode. In the full scan mode, the detection is performed over a wide range of (m/z) and so it detects all the fragments according to its (m/z) values. So, it is useful for the identification of unknown compounds. In the SIM mode, the detection is performed only for a specific (m/z) (2–4) values, thus the sensitivity increases compared to that in the scan mode. In this study, the qualitative analysis has been done using the scan mode to determine the PAH’s. Each compound is represented by a peak of a definite retention time. Table 1 represents the identifying ions for each PAH compound. The quantitative analysis was done using the SIM mode. The peak of each analyte in the sample chromatogram was identified by comparing its relative retention time (RRT) with the RRT of the analyte in the chromatogram of the standard mixture. The quantitative calculation for each compound was done by comparing its relative peak area (RPA) in the unknown sample chromatogram with its (RPA) in the chromatogram of the standard mixture using the one-point calibration method (Alawi, 2008).
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