For me, I decided to get buy a clean container from the store that with a penis-size opening ( clean male donor ). It seemed logical to me to use this clean bottle to reduce the risk of cross-contamination by somthing like shampoo -- which if, btw, is BASIC in nature ( most cases ). This may ultimately interfere with the testing of your sample. Maybe that's just paranoia but it's how I rolled.
Also, instead of a container --which I had a very unfortunate and MESSY experience with a pressure-resistant nozzle -- try using a condom. They are easy to mold and designed not to break ( good thing, last thing we need is more crack babies = law enforcement ). Condoms are also thin enough that they transfer heat well from the body.
Try looking for non-lubed but if you couldn't find any ( like me ), just rinse it out with WATER only -- as soap is also BASIC in nature and may adulterate the pH of the samle.

TIP: Try using as few containers as possible to transfer your sample. The less surfaces the sample reaches, the decreased chances for contamination. Hey, there's ALOT to be said about peace of mind.

Still waiting on my results. Keep those fingers crossed and blunts rolled!