What test method(s) are available to test for presence of honey in a food ingredient that claims to be suitable for those vegans who consider honey as "non-vegan"
What would the analyte be?
What are the limits of detection?
Appreciate any help you might be able to offer...
The question is going to be one of finding a marker for honey that isn't present in the food matrix you're looking to test, and that would be present at a sufficient level to be above the LOD even at a fairly low potential contamination level - assuming you're considering cross-contamination risks rather than significant intentional presence?
Eurofins can do some clever isotopic things with sugars that you could look at using effectively in reverse - normally these would identify non-honey sugars in honey, but in principle I'd expect the methods to also do the reverse.
I do think it will depend on the specific food you're looking to analyse, and potentially also on the honey, so it's the sort of question that probably lends itself to a lab.
Eurofins is certainly a good recommendation, and if they can't do it in the UK then ask them to check with their colleagues at the lab in Nantes - they do a lot of the compositional/authenticity work and may actually be the ones doing the honey analysis offered in the UK.
Personally I'd also get in touch with Gesellschaft fur Lebensmittel-Forschung in Berlin (aka GFL - https://www.gfl-berlin.com/). Their main focus is juices but there is a reasonably degree of overlap with some of the honey methods, and being far smaller than Eurofins they can often be considerably more flexible and accommodating, and the calibre of their work and knowledge of their staff is excellent.
Possibly a stupid question, but have you already tried the more typical methods of determining vegan status - traceability, site risk assessment etc?
For the meat/no meat question analysis can potentially be helpful, but there are a range of other problems for which it becomes something more of a challenge (e.g. very tiny potential presence of shellac in a product that may have been made from waxed fruit).