Sciencemadness Discussion Board - Identifying a blue food colorant

Identifying a blue food colorant

Eddygp - 15-6-2012 at 13:13

So I had this blue water-soluble food colorant and I wanted to know which one it was. I checked through the blue colorants in E numbers (wikipedia here) and I came up with two possibilities: indigo carmine (E132) and Patent Blue V (E 131).
Both are good pH indicators at very basic conditions. So I just bought some more caustic soda (running out of it) and prepared to test it. Results:

1) Colour of colorant solution changes from blue to violet when NaOH is added, exothermically.
2) When acetic acid is added and mixed, it turns a bit darker and then, exothermically, again, changes to a reddish solution.
3) When magnesium sulfate is added, a white precipitate forms (I have filtered it out and I will try to purify it to know what these are).

Not much more information at the moment. Any ideas?
EDIT: Indigo carmine should have turned in step 1 to yellow-pale brown, not violet. Patent Blue V should have changed to a greenish yellow.

[Edited on 15-6-2012 by Eddygp]

mineralman - 17-6-2012 at 03:21

would you say its bright blue, dull blue, royal blue??? ive seen 2 mentioned via a google search, but theres the issue of the identification of the type of blue coloue, and then its issue of natural/artificial, who stocks it (that may require u2u??)
Is there anything you can say from observation? I love a challange

Eddygp - 17-6-2012 at 04:35

I'll take a photo of 1 drop of the colorant in 40ml H2O.

[Edited on 17-6-2012 by Eddygp]

[Edited on 17-6-2012 by Eddygp]

mineralman - 17-6-2012 at 04:48

MAYBE i SHOULD HAVE DEFINED MY DEFFANITION OF CHALLANGE

ERR, Please let me know if blue food colouring could be used to make explosive devices or illicit substances, Id hate to break my bail terms

[Edited on 17-6-2012 by mineralman]

Eddygp - 17-6-2012 at 05:06

Uhhh... what do you mean? I don't think so...

[Edited on 17-6-2012 by Eddygp]

mineralman - 17-6-2012 at 05:28

ok, LIGHT COBOLT BLUE would everyone agree with that?

where did it originate from? a large multi store ie: tescos, morrisons UK or wallmart/greens US OR OTHER? ANYTHING WOULD HELP MM DAMN CAPS LOCK

mineralman - 17-6-2012 at 05:38

Will it filter out with kitchen paper as a filter?
you can try laying the paper on the surface and observe the colour change if any.

do you have hard/soft water or was it distilled or deionised?

mineralman - 17-6-2012 at 05:48

one possiblility , Blue food coloring is made with the FD&C Blue No.1 dye and usually includes a glycerine liquid

YOU READY FOR THIS ONE...........monkey pee FACT, Just trying to find the species, but i guess it would be acidic in nature

The same dye in blu jeanes is used in blue M`N`M's

more to come and Im not a chemist or have I had any training as one, so if theres anything that im missing, need to understand, please let me know MM

mineralman - 17-6-2012 at 06:25

Every site or publication points to this.
could the water be responcible for the indescrepancys in your PH tests?

Name - PATENT BLUE-V Revision No - 00
Classification E - 131 / C.I FOOD BLUE#5 / C.I. NO 42051./ACID BLUE#3
Effective Date - 01/17/2000
No. Characteristic Requirement
DESCRIPTION
DARK BLUE POWDER.

1) Total colour/Assay, percent by Mass, min.
85.00
2) Water-insoluble matter, percent by mass, Max.
00.20
3) Combined ether extracts, percent by mass, Max.
00.20
4)
Subsidiary dyes, percent by mass, Max.

02.00
5)
Dye intermediates, percent by mass, max.
Leuco base.
00.50
04.00

6) Unsulfonated primary aromatic amine (calculated as aniline) percent by mass, max.
00.01
7) Lead, mg/kg, Max.
10.00
8) Arsenic, mg/kg, Max.
03.00
9) Heavy metals, (as pb) mg/kg, max.
40.00
10) Mercury, mg/kg ,Max.
01.00
11) Cadmium, mg/kg, Max.
01.00

OR its monkey pee

Eddygp - 17-6-2012 at 11:18

Bought in European Union. Soft water. Doesn't change colour in kitchen paper. It's not monkey pee, at least I don't think so

peach - 17-6-2012 at 16:11

Quote:

Any ideas?

You've checked the pack I'm hoping.

Quote:

Patent Blue V is banned as a food dye in Australia and USA, because health officials in these countries suspect that it may cause allergic reactions, with symptoms ranging from itching and nettle rash to nausea, hypotension, and in rare cases anaphylactic shock; it is therfore not recommended for children in those countries.

Have you got any kids or know any parents who don't mind you borrowing theirs? Preferably misbehaving kids.

Quote:

Indigo carmine should have turned in step 1 to yellow-pale brown, not violet. Patent Blue V should have changed to a greenish yellow.

If this came in some unmarked bag or bottle as unbranded, unlabelled dye, it's possible you may have a blend of more than one dye in there, or at least, 'other stuff' (e.g. acidity regulators) that may be messing with your pH observations.

Quote:

Any ideas?

Right, more seriously...

-You could try evaporating off the water / alcohol.

-Then buy samples of the two dyes you suspect it to be (also evaporate those off), dilute them all down to a stock concentration, compare the colours.

-Try swinging the pH of them all around and follow those colour changes.

-Try treating these with ozone

To check if you have one dye, two or more mixed together, or a load of random stuff in there you could:

-Try chromatography (a piece of fine filter paper may be enough to show there's more than one in there)

-Check if your pH swings correlate to the amount of alkali that should be needed (to rule out pH modifiers)

-Recrystalise?

If it's not labelled, don't put it in any food. There are good reasons for chemical additives having to adhere to strict regulations on labelling. You don't want to be adding some repackage clothing dye mix to your cupcakes. Certainly don't add it to any food being sold or given to anyone else, or you may end up in a lot of trouble if anyone has any problems with them there cakes.

[Edited on 18-6-2012 by peach]

Eddygp - 17-6-2012 at 23:32

OK, I have new information now:
- The addition of ethanol slows process no. 1. (this one, I don't know for sure, so do not think of it as if it were certain)
- If it is exposed to relatively strong light (near a lightbulb, for example), the process speeds up. (This information I discovered by mistake)
- If you leave the violet solution for approx. 10 minutes, it turns light red progressively.
- If you add sodium silicate NOTHING happens.
- Once it's red, if you expose it to relatively strong light NOTHING happens.

EDIT: Maybe contains triphenylmethyl groups?

[Edited on 18-6-2012 by Eddygp]

Eddygp - 22-6-2012 at 06:37

I think the turning red is due to oxidation or slow acidification (maybe it reacted with caustic soda?). It is not reversible, I think.

francis - 24-6-2012 at 02:00

You could evaporate the solvent and then check the melting point of the solute - according to Wikipedia, at least, the melting points of each colourant are appreciably different, enough to tell which of the two you've got.