Nicholas H. Snow is the Founding Endowed Professor in the Department of Chemistry and Biochemistry at Seton Hall University, and an Adjuncy Professor of Medical Science. During his 30 years as a chromatographer, he has published more than 70 refereed articles and book chapters and has given more than 200 presentations and short courses. He is interested in the fundamentals and applications of separation science, especially gas chromatography, sampling, and sample preparation for chemical analysis. His research group is very active, with ongoing projects using GC, GC-MS, two-dimensional GC, and extraction methods including headspace, liquid-liquid extraction, and solid-phase microextraction. Direct correspondence to: LCGCedit@mmhgroup.com
From Gas to Gas: Fundamentals of Static Headspace Extraction-Gas Chromatography
August 9th 2024In this article, we discuss the fundamentals of headspace extraction, including static versus dynamic extraction, establishing equilibrium in the vial, consequences of the partition coefficient, temperature, pressure, and transfer to the gas chromatograph.
From Detector to Decision, Part IV: Demystifying Peak Integration
March 1st 2024In this installment, we examine several of the common parameters that can affect automated peak integration and the resulting peak areas. We will consider how the data system detects the beginning and end of the peak, how it determines the peak maximum, how real peaks are differentiated from noise, and how signals at individual time intervals are summed to generate the peak area.
From Detector to Decision, Part III: Fundamentals of Calibration in Gas Chromatography
January 1st 2024Gas chromatography is a premier technique for quantitative analysis. As gas chromatographs have become simpler to use and data systems more powerful, much of the data processing involved in delivering quantitative results now happens in the background and is seemingly invisible to the user. In this installment, we will review the calibration techniques used with gas chromatography. We will compare calibration methods and the assumptions that underlie them. We will explore common mistakes and challenges in developing quantitative methods and conclude with recommendations for appropriate calibration methods for quantitative problems.
Are You Ready to Switch to Comprehensive Two-Dimensional Gas Chromatography?
September 1st 2023Comprehensive two-dimensional GC×GC has made great strides in the past 20 years. The author discusses advances in instrumentation, column sets, data analysis, and the range and types of samples amenable to this method.
Does High Polarity Mean High Retention on Stationary Phases in Gas Chromatography (GC)?
January 1st 2023This instalment examines the idea of stationary phase polarity in detail. The assumptions inherent in the most popular stationary phase polarity-evaluating systems—McReynolds constants and the polarity scale—are discussed.