I'm new to DIY and this is a bit off topic but I know a thing or two about maths and measurement and it might help you make more consistent samples. Every time you measure something, you have a degree of error that is built into the method of measurement. The most accurate methods of measurement eliminate the need to "read" a scale as a human interpreting something is another error factor that you don't need.
So let's say you're using a syringe to measure out your quantities. The syringe itself isn't 100% accurate but for these purposes it's fine. The error here comes with your interpretation of the amount you've drawn into the syringe - sometimes you'll be a little bit shy and sometimes you'll be a little bit over the amount you're after. Let's say, for arguments sake that you're average error is +/-0.1ml. If you're making a total of 5ml and you do it all with one syringe pull, you have a potential error value of 0.1ml or 1/50 of your total amount of juice. If you make up a 1ml sample, your error range won't change, so you'll have a potential error of 1/10. That's a pretty bloody big error value. The point being, the largest sample you can make, the more consistent you'll be when it comes to replicating the sample. Clearly you can't make 100ml samples though, you have to balance out cost against accuracy.
Yeah, I know that the more juice you make the more syringe pulls are required and therefore the amount of error will increase, but when you make larger batches you tend to use a larger syringe, meaning your error value does decrease (up to a point).
Hopefully this lot will help you make more consistent samples - I got on a bit of a roll with the typing there though. Sorry!
