Using LC-MS & GC-MS to Decode Photoredox Catalyst Stability

Описание: In this episode of Concentrating on Chromatography, we sit down with Lindsay Repka to discuss how LC-MS and GC-MS transformed her lab’s approach to photoredox chemistry.

What began as a project to develop a visible-light photocrosslinking handle unexpectedly led to a major discovery: the solvent (DMF) was reacting with the photocatalyst itself. Using high-resolution LC-MS, Lindsay’s team observed multiple solvent adducts forming — sometimes with complete catalyst consumption. That discovery reshaped their research direction.

Drawing from her ACS Northeast presentation and this in-depth conversation, Lindsay explains:

🔬 How photoredox catalysts become activated under visible light
📊 Why LC-MS was essential when NMR couldn’t resolve complex mixtures
📈 How to design reproducible calibration curves for percent catalyst remaining
📉 Why extracted ion chromatograms (EIC) outperform total ion chromatograms (TIC) at low concentrations
⚗️ How solvent activation chemistry led to selective N-demethylation
🧪 Why GC-MS with an internal standard streamlined reaction screening
📐 What relative response factors mean — and why they can’t always be assumed constant
🧑‍🔬 Practical tips for improving reproducibility (microbalances, deoxygenated solvents, temperature control)

This episode is a rare deep dive into both LC-MS and GC-MS within the same research project, showing how chromatography-driven insight can turn unexpected degradation into productive new reactivity.

If you work in:

Photoredox chemistry
Reaction optimization
Mass spectrometry method development
Catalyst screening
Academic synthetic chemistry

…this conversation will resonate.

🧪 Key Topics Covered

Photocatalyst stability in DMF, DCE, and MeCN
Demethylation under mild visible-light conditions
High-resolution Q-TOF LC-MS quantitation
Internal standard methodology in GC-MS
Signal-to-noise improvement using extracted ion chromatograms
Reaction reproducibility and quality control strategy

🎙 About the Guest

Lindsay Repka is a chemistry professor at Middlebury College whose research explores photoredox chemistry, catalyst stability, and visible-light-driven transformations. Her lab emphasizes both mechanistic insight and hands-on student training in advanced analytical instrumentation.

If you enjoy conversations at the intersection of chromatography and real-world chemistry research:

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💬 Comment with your LC-MS / GC-MS questions
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