2025-11-17 – Weekly Chemist News : Choosing SPME fibers for amines

Last week’s discussions tackled a range of topics, from practical advice on selecting SPME fibers for volatile amines, to insights into career beginnings and essential skills for chemists. Members also shared experiences, including the challenges of mixing chemicals incorrectly and the unusual samples they’ve encountered. A recurring theme was the importance of proper training and education in the field.


This Week’s Hot Topics

SPME fiber choices for volatile amines
Choosing the right SPME fiber for volatile amines can significantly affect your results. This thread offers practical tips and experiences from those who have navigated these choices.
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Where to get real trace/tox training
Finding quality trace/tox training is crucial for those in analytical chemistry. This discussion provides recommendations and insights into respected programs.
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FAQ/Guidelines
For those new to the forum, this FAQ provides important guidelines and tips to get the most out of your experience here.
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Admin Guide: Getting Started
An essential resource for admins, this guide walks you through the setup process to ensure you can manage the forum effectively.
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Thinking About a Career as a Chemist? Here’s What You Need to Know!
Considering a career in chemistry? This thread outlines the key considerations and realities of being a chemist today.
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How Did You Land Your First Chemist Role?
Members share personal stories and advice on securing that first role in the chemistry field, offering a range of perspectives and strategies.
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What Skills Make a Great Chemist?
A lively discussion focused on the technical and soft skills that distinguish successful chemists in today’s job market.
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Where Did the Term ‘Organic Chemistry’ Originate?
For those curious about the history of chemistry, this thread delves into the origins of the term ‘organic chemistry.’
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That Time You Mixed the Wrong Chemicals
A lighter topic where chemists share stories of their mishaps in the lab, offering both humor and learning moments.
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The Weirdest Sample You’ve Ever Analyzed
From bizarre to baffling, chemists recount the strangest samples they’ve worked with, providing an entertaining read.
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Looking forward to another week of engaging discussions. Your contributions make this community a valuable resource for all.

For ‘volatile amines’, CAR/PDMS headspace, pH>10 with NaCl; short exposures to avoid breakthrough.

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I get steadier recoveries on C1–C3 amines by swapping NaCl for a pinch of solid K2CO3, which bumps salting‑out and pH in one cheap step, then sealing with PTFE‑lined crimp caps to curb headspace losses during a 4–6 min pull. Small caveat: if the matrix is even slightly acidic, add carbonate slowly to avoid fizz and fiber fouling — echoing the OP’s “proper training” point — and @analytix, a quick blank plus bake‑out between runs kills carryover.

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Quick tip from my bench: switching to pre‑silanized headspace vials stopped low‑ppm methyl/ethyl amines from vanishing to the glass and tightened my RSDs without changing the fiber or salt… Small caveat: run a couple blank bakeouts first — fresh vials can bleed a little at 80–100 °C and throw ghost peaks, which is where ‘proper training’ pays off.

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Swapping to a deactivated SPME inlet liner and giving the fiber a full 2‑minute desorb at 260°C finally stopped my light amines from vanishing at the inlet. @Kara tiny caveat: push much hotter or longer and the CAR layer gets cranky, so I watch the baseline after bakeouts — learned that the hard way.

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85 µm CAR/PDMS nailed C1–C2 last week; DVB/CAR/PDMS better beyond C3 — watch wet matrices, @Kara.

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“beyond C3 — watch wet matrices, @Kara.” I’ve had best luck salting to about 20% NaCl and bumping pH >11 with 0.1 M Na2CO3 to freebase the amines before HS‑SPME; small caveat: if your sample has ammonium, carbonate can shift equilibria — use NaOH instead…

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One thing that helped me last week: switching to an amine‑deactivated 5‑type column (30 m × 0.25 mm × 0.5 µm) killed the tailing I couldn’t solve with fiber choice or a hotter desorb. Echoing the “proper training” note, the real fix was realizing the column was the sticky site; with that, C1–C4 sharpened using a 60 s splitless desorb at 250°C. Small caveat: keep the oven under about 260°C or bleed creeps and the light amines wander.

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