This article describes challenges and opportunities in separation science in the rapidly emerging field of RNA modifications. Recent advances in sample preparation have permitted the analysis of RNA modifications in single cells by liquid chromatography–mass spectrometry (LC–MS). The sample handling and microextraction methods described here pave the way for new insights into the function of these unusual molecules in the brain and biological systems.
This installment is the second part of a discussion on the origins and uses for determining the height equivalent of a theoretical plate (HETP) calculations in gas chromatography (GC). This month, I discuss the good and challenging consequences of the Golay theory, its relevance, and some alternatives. Many of the variables that chromatographers view as independent have some interdependence, and we see several limitations of the theory. The complex relationships between HETP and temperature present a particular challenge when thinking about temperature-programmed GC compared to isothermal GC. This article concludes with comments regarding the continued relevance of this classical theory.
The buzz at the 2021 Cannabis Science Conference in Baltimore was palpable: People of widely disparate backgrounds were excited to address the ever-growing challenges and opportunities afforded by this burgeoning marketplace. The phenomenon known as the “green rush” outpaces all significant analytical market areas. Given all this excitement, it is worth stepping back to examine the overarching trends and nuances of the cannabis testing environment and offer some opinions about the key players and disruptive technologies gaining traction throughout this burgeoning marketplace.
The retention of large molecules, such as peptides and proteins, is strongly dependent on mobile-phase composition and temperature. Consequently, the retention times (tR) of these molecules often fluctuate from one separation to the next. In two-dimensional liquid chromatography (2D-LC), this fluctuation can be challenging to deal with, especially if only one or a few specific peaks in the first dimension (1D) separation are targeted for further separation. In this installment, we describe instrumental concepts that are useful for coping with this challenge.
Monitoring the characteristic components in tipping paper is important to ensure the quality of cigarette products. This study establishes a method based on gas chromatography (GC) for determining cooling agents in tipping paper. The tipping paper was cut into pieces and extracted by ethanol under specific temperatures in a shaker. Then, the characteristic cooling agents of (-)-menthone, L-menthol, and (-)-menthyl lactate in extract were determined using GC coupled with a flame ionization detector (GC-FID). The limits of detection (LODs) and limits of quantification (LOQs) for the three cooling agents ranged from 0.15~0.32 μg/mL and 0.49~1.06 μg/mL, respectively. Results demonstrated a good linear relationship with high correlation coefficients for the three tested cooling agents. The extraction conditions of the cooling agents were optimized through a single-factor experiment as well as an orthogonal experiment. The standard addition recovery experiment showed that the average recoveries range from 81.23 to 100.62%, and the relative standard deviations (RSDs) of the measured values (n = 5) ranged from 0.34 to 1.64%.
The quadrupole mass analyzer is now available to many analytical chemists as a detector for high performance liquid chromatography (HPLC) and gas chromatography (GC), thanks to its increasingly accessible price point. Although it’s not vital to understand the working details of these detectors, insight into their design and operation can help enormously when planning, optimizing, or troubleshooting analytical methods.
Two-dimensional liquid chromatography (2D-LC) offers new insights into modern polymeric materials such as biodegradable polymers, polymers made from renewable feedstock, and complex formulated systems. Advances in instrumentation and the development of new modulation techniques enable more combinations of different separation modes. Hyphenation with universal and information-rich detectors further enhances the versatility and flexibility of the analytical strategy. Detailed characterization of copolymer composition heterogeneity and identification of polymeric ingredients in complex consumer products are key highlights of new applications.
I am pleased to present our annual review of new products in gas chromatography (GC), introduced between spring 2021 and spring 2022. With the Covid-19 pandemic still impacting travel and conferences, the 72nd meeting of the Pittsburgh Conference on Analytical Chemistry and Applied Spectroscopy (Pittcon) from March 8–12, 2022, originally scheduled to take place in Atlanta, Georgia, was canceled at the last minute. Although many of the technical presentations were conducted virtually, there was not sufficient time to re-tool the exposition, so this review was conducted virtually for the second year in a row.
This article provides an overview of the pharmaceutical industry for the separation scientist, including its historical, societal, and economic impacts, marketing landscape, therapeutics trends, and career opportunities in analytical chemistry.
Some LC troubleshooting topics never get old, because there are some problems that persist in the practice of LC, even as instrument technology improves over time. There are many ways for things to go wrong in an LC system that ultimately manifest as peak shapes that are not good. Developing a short list of the likely causes of these results can help streamline our troubleshooting experience when peak shape-related problems occur.
A biosimilar is a drug product that has been deemed to be highly similar to its off-patent reference product in terms of purity, molecular structure, and bioactivity. Approvals to such products are granted on the basis of unambiguous demonstration of “no clinically meaningful differences” between the reference and the intended biosimilar. For a successful biosimilar approval, establishing analytical and functional biosimilarity across all relevant critical quality attributes is an essential prerequisite. This critical activity is performed using a combination of orthogonal, high-resolution tools that can accurately quantitate the minor differences that exist. In this article, we review key findings from some of the recent biosimilarity assessments that we have published on biosimilars of granulocyte-colony-stimulating factor (G-CSF), insulin glargine, rituximab, and trastuzumab.
Injecting too much sample onto a chromatographic system will eventually overload the column. Analytical chemists are concerned about column overloading because it reduces column efficiency, and, as a result, the resolution is sacrificed. Surprisingly, there is little data in the literature about the overloading of the porous layer open tubular (PLOT) columns. This month’s article looks at the basic types of column overload, volume and mass, and defines the variables that most affect the sample loading capacity in PLOT column chromatography.
Py-GC–MS Investigation of Pyrolysis Behaviors and Decomposition Products of α- and β-2,7,11-cembratriene-4,6-diols May 1, 2022 Shen Huang, Chen Yang, Ning Ma, Lifeng Zhou, Chunxiao Jia, Tao Wei, Duobin Mao LCGC North America, May 2022, Volume 40, Issue 5 Pages: 223–228 To study the thermal stability of cembratriene, α- and β-2, 7, 11-cembratriene-4, 6-diols (α- and β-CBT) were isolated from tobacco leaves. Thermogravimetric (TG) and differential thermogravimetric (DTG) analyses were used to evaluate the cleavage differences between the two compounds. The TGA results showed the peak temperatures (Tp) were 263.3 °C and 254.1 °C with the largest weight loss rate; the significant weight losses were 90.96% and 99.45%. Pyrolysis gas chromatography–mass spectrometry (Py-GC–MS) was employed for the pyrolysis products at different temperatures (300, 600, and 900 °C) under either N2 or an O2:N2 (10%:90%) mixture. The results showed that the major pyrolysates from α- and β-CBT were simple hydrocarbons, such as toluene, 1, 4-pentadiene, and p-xylene, as well as several important flavor compounds, such as 2-methylfuran, benzaldehyde, and 4-methylbenzaldehyde. More pyrolysis products were obtained at higher temperatures, and almost all of the harmful aromatic ingredients were produced at 900 °C. Importantly, solanone, a significant flavor component, was only obtained from the pyrolysis of α-CBT under 10% O2 in N2 at both 600 and 900 °C. The number of the pyrolysates changed with the change in pyrolysis temperature and the presence of oxygen. The study of the thermal behavior and pyrolysis products of these terpenoids could possibly suggest flavor precursors that could be used to provide specific flavors.
I was fortunate to be raised in an environment where I was never told that I couldn’t do or study something just because I was a girl. I have, however, dealt with gender bias many times in my career, and know that it is something that I will continue to face in the future to some extent. From each experience, I try to learn and grow.
