Critical review and re-assessment of analyte protectants in gas chromatography

Authors: RODRIGUEZ-RAMOS, RUTH - UNIVERSITY OF LA LAGUNA; Lehotay, Steven; MICHLIG, NICOLAS - UNIVERSIDAD NACIONAL DEL LITORAL; SOCAS-RODRIGUEZ, BARBARA - INSTITUTO NACIONAL DE INVESTIGACION Y TECHNOLOGIA AGRARIA Y ALIMENTARIA; RODRIGUEZ-DELGADO, MIGUEL - UNIVERSITY OF LA LAGUNA

Submitted to: Journal of Chromatography A
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/28/2020
Publication Date: 9/29/2020
Citation: Rodriguez-Ramos, R., Lehotay, S.J., Michlig, N., Socas-Rodriguez, B., Rodriguez-Delgado, M.A. 2020. Critical review and re-assessment of analyte protectants in gas chromatography. Journal of Chromatography A. https://doi.org/10.1016/j.chroma.2020.461596.
DOI: https://doi.org/10.1016/j.chroma.2020.461596

Interpretive Summary: Gas chromatography (GC) has been a central tool in analytical chemistry for more than 60 years to analyze organic molecules that remain stable and volatilize when heated, but active sites on glass and metal surfaces in the system have always reduced GC performance. Introduced in 2003, the use of analyte protectants (APs) are an advantageous way to overcome active sites in GC. The APs preferentially fill the active sites that would otherwise detrimentally affect the analytes. This work critically reviews the scientific literature about APs for the first time and presents new research findings involving the use of APs with state-of-the art instruments. APs provide benefits of lower detection limits, enhanced signals, sharper and more symmetrical peaks, and more consistent retention times. The article will help to disseminate the usage of APs in GC to improve results for millions of samples analyzed per year, if fully implemented.

Technical Abstract: Despite nearly 80 years of advancements in gas chromatography (GC), indirect chemical matrix effects (MEs), known as the matrix-induced response enhancement effect, still occur to cause a high bias in the GC analysis of susceptible analytes, unless precautions are taken. Matrix-matched calibration is one common option used in GC to compensate for the MEs, but this approach is usually inconvenient, imprecise, and inefficient. Other options, such as the method of standard additions, surface deactivation techniques, chemical derivatizations, priming the GC, and/or use of internal standards, also have flaws in practice. When methods are accommodating, the use of analyte protectants (APs) can provide the best practical solution to not only overcome MEs, but also to maximize analyte signal by increasing chromatographic and detection efficiencies for the analytes. APs address the source of MEs in every injection by filling active sites in the GC inlet, column, and detector, particularly in GC-MS, rather than the analytes that would otherwise undergo degradation, peak tailing, and/or diminished response due interactions with the active sites. The addition of an adequate amount of APs (e.g. sugar derivatives) to all calibration standards and final extracts alike often leads to lower detection limits, better accuracy, more consistent retention times, narrower peaks, and greater robustness than the other options to compensate for MEs in GC. This article consists of a critical review of the scientific literature, proposal of mechanisms and theory, and re-evaluation studies involving APs for the first time in GC-orbitrap and GC-MS with a high-efficiency ion source design. The findings showed that 1 µg each of co-injected shikimic acid and sorbitol in the former case, and 1 µg shikimic acid alone in the latter case, led to high quality results in multi-residue analysis of pesticides and environmental contaminants.