Chromatography Online
November 12th 2024. Liquid chromatography and tandem mass spectrometry (LC–MS/MS) was used to show that repeated stress can cause delayed but sustained changes in blood plasma proteins associated with water conservation, immune responses, fat metabolism, insulin sensitivity, iron recycling, and hormone transport in elephant seals.
Chromatography Fundamentals, Part V: Theoretical Plates
Nov 1, 2018 · Conclusions. The number of theoretical plates, which forms the basis of chromatographic theory, is a key parameter used in all modes of chromatography for measuring column efficiency. It is simply the ratio of retention squared to peak variance, a relationship first realized by Martin and Synge.
Reversed-Phase HPLC Mobile-Phase Chemistry — Explained
Nov 1, 2014 · Table I: Solvochromatic and physicochemical properties of common solvents used in reversed-phase HPLC. Modern approaches to working with ionizable analytes often involve working at pH extremes to avoid variations in selectivity because of changes in the mobile-phase pH. The pH is typically altered using trifluoroacetic acid, formic acid ...
Stationary Phase Selectivity: The Chemistry Behind the Separation
Nov 1, 2018 · Selectivity comes from the difference in free energy change for the partitioning of the analyte (s) from the mobile phase into the stationary phase, as seen in Equation 3. We have now seen the fundamental and thermodynamic basis of selectivity. Next, we discuss the impact of selectivity on the separation and resolution.
Estimating Resolution for Marginally Separated Peaks
Sep 1, 2014 · That is, the resolution is the difference in retention times divided by the average baseline peak width (thus the factor of 2 in equation 1). The peak width at the baseline for a Gaussian peak is 4σ (4 standard deviations), whereas at the half-height, it is 2.354σ, so the factor in equation 2 is (2 × 2.354/4) = 1.18.
Peak Shapes and Their Measurements: The Need and ...
Dec 1, 2017 · Volume 35. Issue 12. Pages: 846–853. A number of approaches for peak shape measurement are available in modern chromatography software. We discuss the advantages and drawbacks of those approaches, and present a new concept, “total peak shape analysis.”. Gaussian peak shapes in chromatography are indicative of a well-behaved system.
The Essence of Modern HPLC: Advantages, Limitations, …
Jun 1, 2013 · This article reexamines the fundamental concepts of high performance liquid chromatography (HPLC) to bring fresh insights to how we perform HPLC today. It reviews the prominent advantages that render HPLC indispensable and comments on its many perceived limitations. Several opportunities with far-reaching impacts in life science for the ...
Back to Basics: The Role of pH in Retention and Selectivity
Jan 1, 2017 · Peak 3 (orange) has a similar p Ka (2.75), so very similar behavior is seen for peaks 3 and 4, with stable retention above pH 4.0. Although the retention times of these two peaks change with pH, the selectivity, α, changes only a small amount (range of α = 1.36–1.40), so they nicely separated at all pH values shown.
Chromatography Fundamentals, Part VIII: The Meaning ...
Nov 1, 2019 · The general resolution equation is defined as. where â s is the spacing between the apex of two signals with respect to their average baseline width, wav = (w1 + w2)/2. This equation is applicable to all signal shapes; however, the significance of the calculated value depends upon the geometry or shape of the signal.
Ion Chromatography: An Overview and Recent Developments
Jul 1, 2010 · The basics of IC are reviewed and recent advances that may extend this technology to new applications are discussed. The term ion chromatography (IC) was first used in 1975 to describe the chromatographic determination of inorganic anions using an anion-exchange separation and conductivity detection (1). This development allowed analysts to ...