Measuring the ABV of a macerated spirit

[Ankaa13]

Hi all!
I am working on a campari-esque red aperitif. Currently my recipe involves a maceration of some ingredients, followed by a distillation and then another maceration of other ingredients. I use an ultrasonic cleaner to speedily macerate the ingredients. Invariably there is some loss of liquid to the solid ingredients but I believe also potentially from the heat generated by the ultrasonic cleaner. I'm trying to determine if/how I can measure the ABV of the spirit post maceration so I can accurately proof down. Or do we think that the ABV has stayed much the same during that final maceration?
Some real numbers: I put 250ml of distillate at 80% and about 35g of ingredients in the ultrasonic cleaner. When it was finished I had 150ml of macerated spirit. 
 

Thanks in advance!

[jocko]

Depends on the ingredients.  Ingredients that contain water/juice will lose water content and gain ethanol content. 

The only way to do it properly is to distill it per the TTB test, or run it through an alcohol meter like an Anton Pair Alcolyzer and Density Meter.  Or, spend $30 and send it to White Labs for a measurement on their equipment. 

You'd be surprise how far off your manual questimate can be based on the ingredients macerated. I was.

[Bourbonbeard]

jocko hit the nail on the head with the alcohol content loss. I did a triple sec before and the botanicals added sucked up a lot more alcohol than we had thought. Manual hydrometer was off big time because of the sugar added to the mix. Put it through the Anton Paar and it was off from what we estimated by about 5% abv if I remember correctly

[meerkat]

The small volume and the high ABV make this measurement more difficult. If the maceration is for flavors only (like gin) then you can measure the ABV using an electronic density meter. But with a campari you are probably looking at around 2.5 brix of sugar and you need to take obscuration into account.

The small volume rules out precision hydrometers and lab distillation. The NIR and density plus RI methods won't cope with anything above 65 ABV unless you dilute the sample - and therefore decrease the accuracy.

If you have an EDM that can give you an accurate density with a small sample you could combine this with the solids content measured by gentle drying to calculate the ABV using software like AlcoDens LQ or similar. At a given temperature the ABV, brix and density are inter-dependent so if you know any two you can calculate the third.