I know that the decaffeination process is not perfect and that it leaves some caffeine. I've looked online and there was a company in 2009 that offered caffeine test strips but they seem to be no longer offered.

Another approach would be to use a GCMS, but used GCMS devices are expensive and it takes alot of effort to keep them in calibration (at least it did when I was in college).

Are there services where I can send a sample off and they will tell me how much caffeine they contain? Failing that, how would I reasonably test how much caffeine is in my tea and coffee?

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    $\begingroup$ Why do you want to do that? $\endgroup$ – Karl Mar 2 at 17:32
  • $\begingroup$ Yes, there are many labs that do food testing, and include caffeine testing among their services. But it's expensive; the pricing is designed for businesses rather than consumers. E.g., mydrinkbeverages.com/services/new-beverage-development/… does caffeine testing by LC/UV, but it costs $150 per sample (search this document for "caffeine": 4557656.app.netsuite.com/core/media/… ) $\endgroup$ – theorist Mar 3 at 3:22
  • $\begingroup$ Why do it yourself when others have already done the analysis? As this report shows. $\endgroup$ – matt_black Mar 3 at 12:08
  • $\begingroup$ I want to do it for myself because every cup is different. And every batch of tea is different. And I want to know what’s going on with my food, not other food. $\endgroup$ – vy32 Mar 3 at 19:03

You may try to extract the caffeine with DCM and determine its concentration by spectrophotometry.

  • $\begingroup$ So the idea would be to get a used UV spectrometer? $\endgroup$ – vy32 Mar 3 at 19:03
  • $\begingroup$ I would suggest so. See ncbi.nlm.nih.gov/pmc/articles/PMC4641934. The spectrum of caffeine has a peak of absorbance at 274 nm (UV). $\endgroup$ – Lemoine Mar 3 at 19:28

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