**LC*GC**

Volume 37, Number 2, February 2019

**LC*GC February 2019 Table of Contents**

LC TROUBLESHOOTING
Reversed-Phase Liquid Chromatography and Water, Part I: How Much is Too Much?
Dwight R. Stoll
In reversed-phase separations, retention generally increases as the fraction of water in the eluent increases. When we encounter situations where retention is too low for an analyte of interest, we tend to use eluents with higher and higher levels of water. But how much water is too much?
GC CONNECTIONS
GCxGC: From Research to Routine
Nicholas H. Snow
Two-dimensional gas chromatography (GCxGC) is becoming the technique of choice for analysis of highly complex samples such as petroleum, pharmaceuticals, biological materials, food, flavors, and fragrances. Here, we explain how GCxGC works and provide examples that illustrate its advantages.
THE ESSENTIALS
Optimizing Sensitivity in GC–FID Analysis
It is often possible to achieve better sensitivity and lower limits of detection and quantitation using standard gas chromatography instrumentation. Paying attention to fundamental variables—like sample solvent, initial oven temperature hold, carrier gas operating mode, and thermal gradients— can lead to much improved method performance.

The 2019 LCGC Awards
Jerome Workman Jr.
The contributions of Milos V. Novotny and Ken Broeckhoven, the winners of the 2019 LCGC Lifetime Achievement and Emerging Leader in Chromatography Awards, are presented.
Data Integrity Focus, Part II: Using Data Process Mapping to Identify Integrity Gaps
R.D. McDowall
Data integrity is paramount when working in a regulated environment. Data process mapping is an excellent way to identify and mitigate data gaps and record vulnerabilities in a chromatographic process. This approach is simple and practical.

Volume 37, Number 1, January 2019

SAMPLE PREP PERSPECTIVES
Is Headspace Sampling Quantitative?
Douglas E. Raynie
Whether or not headspace sampling is quantitative depends on the information gleaned from the analysis.
LC TROUBLESHOOTING
What’s Trending in LC Troubleshooting?
Dwight R. Stoll
We look at problems in LC that can be traced to contaminated solvents or reagents, and how sample solvent effects can lead to poor performance in HILIC.
GC CONNECTIONS
Stopping GC and GC–MS Problems Before They Start
Nicholas H. Snow
By taking simple proactive troubleshooting steps, GC users can ensure that instruments will operate correctly over time, thus avoiding workflow disruptions.
FOCUS ON BIOPHARMACEUTICAL ANALYSIS
Methods and Purposes for Determining Higher Order Structures of Biopharmaceuticals
J. Auclair, A. Rathore, and Ira S. Krull
Determining the higher order structure of a protein pharmaceutical is important. Here, we review the approaches for HOS determination that are currently receiving the most attention in the literature and at scientific meetings.
THE ESSENTIALS
Essential Theory of HPLC
The elution mechanisms for gradient and isocratic HPLC are fundamentally different from each other. Here is what you should understand about both.

Data Integrity Focus, Part 1: Understanding the Scope of Data Integrity
R.D. McDowall
There are many factors to consider in a data integrity and governance program. Fortunately, a simple diagram can help us understand what needs to be covered.

Suspect Screening of Chemicals in Food Packaging Plastic Film by Comprehensive Two-Dimensional Gas Chromatography Coupled to Time-of-Flight Mass Spectrometry
Yelena Sapozhnikova and Eunha Hoh
The occurrence of additives like plasticizers in plastic food packaging has been documented, but information on their potential migration into foods is limited. In this pilot study, 2D GC–MS was used to identify chemicals extracted from a common stretch plastic film with a series of organic solvents. In total, 91 compounds were tentatively identified, including five PCBs.