The Limit of Detection - Chromatography Online
WEBFeb 1, 2009 — The concept of the limit of detection (LOD) has been, and still is, one of the most controversial in analytical chemistry. The multiple definitions and calculation methods proposed have contributed to this situation. Although in the last years, several international organizations, such as ISO or IUPAC, have tried to reach a consensus in their definitions and have issued guidelines for the ...
Mobile-Phase Degassing: What, Why, and How - Chromatography …
WEBJul 1, 2014 — If mobile-phase outgassing occurs within the LC system, the most common problem areas are the pumps and detector. At the extreme, air in the pump will cause the pump to stop delivering mobile phase to the column. If only an occasional bubble is present, the flow rate will be erratic, causing retention time problems.
LC–MS Sensitivity: Practical Strategies to Boost Your Signal and …
WEBSep 1, 2018 — In liquid chromatography–mass spectrometry (LC–MS), sensitivity directly relates to the effectiveness of producing gas-phase ions from analytes in solution (ionization efficiency) and the ability to transfer them from atmospheric pressure to the low pressure zone of the MS system (transmission efficiency) (3). The optimization of ionization ...
Chromatography Fundamentals, Part V: Theoretical Plates: …
WEBNov 1, 2018 — Volume 36. Issue 11. Pages: 830–835. The number of theoretical plates forms the basis of chromatographic theory, and is a key parameter used in all modes of chromatography for measuring column efficiency. Fortunately, it’s easy to measure. Plates are generated during the elution of solutes through a …
Troubleshooting Gas Chromatography: Reduced Peak Size (Loss of …
WEBJun 1, 2020 — Run a column test mix and compare with the result obtained originally. If loss of column efficiency is suspected, trim 0.5–1 meters of column at the inlet end. Verify that the column has been installed to the correct distance within the GC inlet and detector. For flame-based and ionizing detectors, check that the gas flows are correct paying ...
Evaluating the Goodness of Instrument Calibration for …
WEBNov 1, 2020 — Consider a calibration curve that extends from 1 ppb to 100 ppb. A residual of 10% at 1 ppb = 0.1 ppb, while a residual of 10 at 100 ppb =10 ppb. Because the squares of the absolute residuals are minimized, then residual for the 100 ppb level will have 10 2 /0.1 2 = 10,000 times more impact than the residual at the 1 ppb level.
From Detector to Decision: How Does the GC Instrument Generate …
WEBSep 1, 2020 — Using the flame ionization detector (FID) as an example, we will explore how the detector generates a signal, what that signal is, and how it is processed into the chromatograms and other information that is stored and provided by a modern data system. We will do this by walking through the evolution of …
Analysis of Ethylene Oxide and 2-Chloroethanol in Food Products ...
WEBAug 4, 2022 — Volume 18. Issue 8. Pages: 10–16. Ethylene oxide (ETO) and its metabolite 2-chloroethanol (2-CE) represent a new emerging food safety issue, with significant product recalls and more than 800 notifications on the EU RAFSS portal. Determination of these contaminants is presented based on the EURL Single …
Going Low: Understanding Limit of Detection in Gas …
WEBLCGC North America May 2021. Volume 39. Issue 5. Pages: 232–235. Limit of detection (LOD) is among the most important and misunderstood analytical variables of merit for both instruments and analytical methods. In this installment, we review the history and fundamentals for determining and reporting LOD for analytical instruments and methods.
Chromatography Fundamentals, Part VIII: The Meaning and …
WEBNov 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.