Borate and rosocyanine wont react

[DaveOB]

Hi all

New to chemistry and needing some advice please.

I am busy with a DIY project for my home pool analysis. I have assembled an RGB LED and a color sensor to read the color of water in a test tube ( using an Arduino board and LCD screen ). Firstly I am using this to better read the color of the DPD 1 tablet color in the water that gives me a better free chlorine reading. Very happy with the results so far.

Next I am working on pH reading, and also want to add reading color for borates.

This is the bit where I am stuck - the borates.

Here's where I am at so far :

I have created a 'known control solution' of 5000ml water, 44 g Borax power and 22ml hydrochloric acid.
My research tells me that this should create a 1000 ppm borate ( or is that Boric Acid ) solution, so :
= 1000 parts per 1000ml
= 1 part per 1 ml.

Next, I have 2 test bottles :
b1 contains 248 ml water + 2 ml of Control Solution. ( 2ml = 2 parts in 250ml = 8 parts in 1000 ml = 8 ppm )
b2 contains 240 ml water + 10 ml of Control Solution. ( 10ml = 10 parts in 250ml = 40 parts in 1000 ml = 40 ppm )

As a reagent to create different colors in the water, I should be able to use curcumin, an extract from the spice turmeric.
I have created a reagent solution with 30 ml acetone + 1 curcumin extract capsule dissolved in the acetone.

I read that curcumin reacts with borate ions in an acidic solution to create rosocyanine. The pH of samples b1 and b2 is around 6.7

So far, I have not been able to find a reliable way to get the curcumin to react with the borates. Only happened when I added some dissolved caustic soda flakes ( drain cleaner ) to the control solutions b1 and b2.
But the volume needed to create the rosocyanine reaction was around 50%, and at that point I discovered that even plain water + caustic soda solution ( without borates ) would create the rosocyanine reaction, so am wondering if I am totally off track here.

My suspicion, ( although I have no chemical background and very little understanding ) is that I am missing a step that would convert the boric acid in the control solution ( and then later also in the sample being tested ) from boric acid to borate ions, that would then react with the curcumin.

On top of this, we live in an area where resources are limited, so I am trying to set up this test using basic components that are available easily.

Any advice would be greatly appreciated.