You can see if there’s a lab tech nearby that you can post samples to on their website. Also the classwork goes on sale pretty often. Pressures above 150PSI will definitely kill your brew, both in the pump and when it’s impacting the leaf surface/ground. I’m sure you’re using a pretty big spray tip to accommodate possible chunks in the tea. I use a gravity-fed boom system at work that works good, but I’m looking into a cheap air diaphragm pump and a little pancake compressor from harbor freight to get some better spray capabilities. Air diaphragms are extremely gentle and easy to use, and small ones can be found for about the same price as a paint sprayer, so with all the other nuts and bolts it would be slightly more expensive.