Sciencemadness Discussion Board - homemade natural indicator

homemade natural indicator

tito-o-mac - 1-7-2007 at 00:16

I've been trying to make a homemade natural indicator over the past few weeks.

I would like some ideas on producing them. I still need four more examples to go. My first one is cabbage juice. I can't think of anymore.

Xenoid - 1-7-2007 at 00:56

I assume you mean RED cabbage juice!

Most coloured plant materials will act as pH indicators to a certain extent!

Try beetroot, onion skin, various coloured flowers - extract the colour with alcohol if you have it!

Xenoid

tito-o-mac - 1-7-2007 at 01:05

Thanks Xenoid! I'm working on that now!

By the way you mentioned different coloured flowers work. Do red rose petals work?

[Edited on 1-7-2007 by tito-o-mac]

[Edited on 1-7-2007 by tito-o-mac]

garage chemist - 1-7-2007 at 02:20

There have been several threads on this subject on this board:
https://sciencemadness.org/talk/viewthread.php?tid=1372&...

https://sciencemadness.org/talk/viewthread.php?tid=2464&...

tito-o-mac - 1-7-2007 at 05:04

Thanks. I didn't know there was another forum going on. Anyway, I managed to make the Red cabbage,the tumeric based indicator, and accquire black berries,blueberries(from the local store), and even currry powder(curry is my favourite).

chemkid - 1-7-2007 at 12:26

I have a bunch of tumeric adn red cabbage indicator strips.

Just dip little pieces of paper towel or even just normal white paper into either an aqueous solution of tumeric (or curry powder) or to make red cabbage indicator just dip into cabage juice.

My tumeric and indicator papers have worked just fine for my pruposes.

Elttil - 21-9-2007 at 01:48

I made red cabbage juice some days ago, works really really great. It owns all kinds of expensive liquid indicators.

woelen - 21-9-2007 at 03:53

Red cabbage juice indeed is very nice. It can make 5 different colors, depending on pH:

Red: dilute hydrochloric acid
pink: plain vinegar
blue/purple: dishwashing soap
green: dilute sodium carbonate or ammonia
yellow: concentrated sodium carbonate or dilute sodium hydroxide

[Edited on 21-9-07 by woelen]

hodges - 25-9-2007 at 15:25

Even food coloring will change color at extreme enough pH.

Hodges

chemrox - 25-9-2007 at 21:16

I'm impressed! I had no idea the red cabbage was such a versatile indicator. I'll pass this on to my biodiesel clients who like this sort of thing. I think I do too now come to think of it. We should callibrate it a little more rigorously though. I'd like number ranges. This stuff looks almost as good as the 0-14 paper in the little brown spool. It's bound to be popular; its vegatarian and organic!

I'd like to followup on the threads. Ozone suggested:

"Get a small pump. Wash some activated carbon in boiling water. Slurry the carbon into a column. Pump the liquid extract though the carbon (better if you can heat this *jacketed column* at about 80°C) to yield clear, colorless liquid. Drain the carbon and dry it (a vacuum oven at 50°C, ~24mmHg works well). Elute the carbon with (DMSO works better, but is very hard to remove) DMF (which is still hard to remove). Remove the DMF with a rotary evaporator or vacuum oven (it does not take much solvent to do this). The residue will contain all of the stuff you are interested in (mostly anthocyanines, polyphenolics, cinnamic acid derivatives, and flavanoid derivatives (quercetin is a flavone)."

Instead of the above couldn't one extract dried cabbage in a soxhlet with IPA or maybe acetonitrile?

[Edited on 25-9-2007 by chemrox]

Antwain - 26-9-2007 at 00:59

You could probably extract with any one of several solvents. Best bet is probably to try them on a small scale and see what you get, if it works your coloured compound will move into the solvent (duh). No idea what it applies to, but I have found that several natural indicators are too easily destroyed by moving out of moderate pH's. Can't say I have ever tried red cabbage, but IIRC beetroot juice turns green in alkali, then fades to clear and never works again. I tried some flowers, then gave up to settle for the 2 industrial indicators I have. I would be interested to see your results, may be worth doing.

contrived - 26-9-2007 at 14:19

I saw a process for making red cabbage indicator that simply used water to extract and left the water in it. It was used as the aqueous solution. What's wring with that? Would it last longer as an alcohol or ether solution? If it breaks down, why? To what? I ask because it seems like a very nice indicator.

Slimz - 26-9-2007 at 14:31

anyone know about this plant
http://web.vet.cornell.edu/CVM/HANDOUTS/plants/Phytolacca%20...

Ozone - 26-9-2007 at 15:51

If you macerate (mush it up and grind it with hot water) the plant and press it you will get a mix juice (with a lot of floating crap, plant colorants, ash, etc.). If you add to this Ca(OH)2 (suspended at 5% m/m in H2O) until the pH is 7-8 (litmus) then heat rapidly to boiling (microwave works well) then add 5 ppm (or so) of anionic polyacrylamide (flocculant, used in water treatment) you will get a dark clarified juice.

This tends to remove the bulk of chlorophyll (which you will get with most organic solvents--and waxes), polysaccharide, protein, etc whilst passing though roughly 60% of the phenolic material intact (these don't ionize too well with lime). This also tends to remove some of the wax.

Soxhlet with hexane prior to this will get rid of the wax problem, but not remove much else.

Decolorize this with your carbon (which, I forgot to mention above, needs to be thotoughly washed with hot water to remove the water soluble non-adsorbed stuff) and fractionate on silica gel (TLC first. I'd try eluting with TFA:meOH:toluene after first eluting with ethyl acetate:toluene; you need to tune this depending upon which bands you want to capture).

I have had good results with cyanopropyl silica eluted with MeOH/TFA (0.1%), but this would be very hard to do b/c the packing is quite expensive.

This seemed like an interesting application:

Color changing hand soap composition

page:http://www.freepatentsonline.com/20050090414.html

Abstract:A composition can indicate whether hands have been washed for an approximate predetermined period of time. The composition includes a pH indicator and a delivery system. The delivery system contains a pH-altering compound. The delivery system is added to the pH indicator approximately when hand washing begins. A method of washing hands is also presented. The pH indicator is applied to the hands. The delivery system is applied to the hands approximately when hand washing begins. The pH indicator and delivery system are mixed. A system for washing hands is also presented. The system includes a pH indicator, a delivery system, and a dispenser that releases the pH indicator and delivery system to hands. The hands are washed until the pH indicator changes color.

Cheers,

O3

[Edited on 26-9-2007 by Ozone]

not_important - 26-9-2007 at 16:31

Quote:

Originally posted by Slimz
anyone know about this plant
http://web.vet.cornell.edu/CVM/HANDOUTS/plants/Phytolacca%20...

It can be used to poison mammals, although not birds. The pigments in poke as betalains and do not function nearly as well as indicators as anthocyanins do.

P. dioica is more interesting than P. americana.

Slimz - 27-9-2007 at 05:27

Yeah i experimented last night... the dye has virtualy no reaction... too bad because i have a fenceline full of em.

UnintentionalChaos - 27-9-2007 at 15:47

Eh, I've worked with phytolaccum americana before...It's very similar chemically to beet juice and the pigment is not very stable. I have done extractions of curcumins from turmeric before. I have a few grams in the freezer and some dissolved as indicator. I will warn you that the endpoint is not terribly easy to see. It starts bright yellow and you have to watch for a tinge toward orange to find the endpoint. It helps to have a reference beaker to compare color.

Lemme find those notes on the extraction somewhere.....ah yes...

Take 15 grams of turmeric powder and place in a flask with 75ml of alcohol (I used denatured alcohol 50:50 ethyl methyl blend) Lacking a full apparatus, I simply brought the mix to boiling for a few minutes and allowed to cool (reflux 5-10 minutes if you have proper labware) I gravity-filtered the resulting solution to make sure it was free of particles. Outdoors or in a fume hood, heat the resulting solution in an open beaker/flask until the volume has been reduced to around 10ml (extraction was much better with large initial solvent volumes). At this point, the solution will be intensely red and somewhat thick. Allow to cool. Measure out two 25ml portions (3 or more would be better, in retrospect) of an aliphatic hydrocarbon solvent (I used n-heptane since it is what I had on hand). Add one portion to the curcumin solution and stir for a minute or two (I found that if acetone is used as a solvent for the extraction, emulsions tend to form in this step). Using a pipette, remove the alcohol phase after it settles to the bottom and pools together. Repeat this extraction with the other portions of hydrocarbon solvent. In a beaker with about 50ml (you can add more if necessary) of distilled water, place @5g NaOH (or KOH, mass isn't very important, but a large excess seems to be necessary). Add the curcumin solution to the NaOH and stir until it dissolves entirely (This may be hard to see since the solution will be intensely dark reddish brown at such a high pH...add more water to thin out if necessary) Cool to room temperature if the solution is still hot. To this, add a chilled acid solution (I used standard white distilled vinegar) until the color suddenly changes from dark red to pale yellow filled with flakes of orange material. Filter off these flakes. Yield will appear deceptively large and it contains much trapped water. Actual yield is a fraction of a gram. You can immediately dissolve them into alcohol or acetone if an indicator was your goal. I used a rate of 1g/100ml of the mixed alcohols.

Explanations:
If the hydrocarbon extractions are not performed, it seems that much oily material remains in the curcumin. When lye was still hot, I got drops of red liquid floating after neutralizing the base. When the lye was cold, I got semisolid, sticky flakes.

If the lye mixture was still hot, even with hydrocarbon extractions, I tended to get a possibly colloidial dispersion of curcumin in the mixture which refused to settle after days of sitting and made the water look rather orange-juice like.

Amos - 30-4-2015 at 08:45

Recently I made what could possibly be seen as an alternative to universal indicator from the wild violets growing in my back yard, by extracting the dyes with hot methanol. Below is a picture of the dye displaying various colors in different pH conditions.

In the picture, pH decreases as you go from left to right.
The dye is in solutions of, from left to right: sodium hydroxide, sodium carbonate, sodium bicarbonate, just methanol(neutral), distilled white vinegar, citric acid, dilute hydrochloric acid, concentrated nitric acid.

The camera didn't pick it up well, but the vinegar solution(5th from left) is actually more violet than it is blue. The concentrated nitric acid solution actually turned to more of a yellow-orange with time, but I suspect this is due to oxidation occurring.

So if you've got any of these growing near you, you might want to harvest some before it's too late!

blogfast25 - 30-4-2015 at 08:50

Quote: Originally posted by Amos

Recently I made what could possibly be seen as an alternative to universal indicator from the wild violets growing in my back yard, by extracting the dyes with hot methanol.

That's quite impressive!

Can you describe the extraction process a little better?

Have you done any paper/silica chromatography on the extract?

Morgan - 30-4-2015 at 09:33

Has anyone changed the color of a morning glory flower by touching it with a lit cigarette or merely holding it almost touching the flower? The ones that are a deep blue or purple make a pretty green if I recall. You can sort of put an interesting dot pattern on the flowers this way. And other flowers are susceptible too, maybe pansies I can't remember. Perhaps the effect was caused by heat but maybe it was something in the smoke.

What household substances can be used as acid/base indicators?
http://antoine.frostburg.edu/chem/senese/101/acidbase/faq/pr...

[Edited on 30-4-2015 by Morgan]

Amos - 30-4-2015 at 09:39

Sure, I simply took the whole, freshly-picked flowers(I would have to guess maybe 50 grams or so, including moisture content), removed the stems, and placed them into a round bottom flask, refluxing them in about ~75mL of methanol for about 15 minutes. I then filtered the entire contents of the flask, collecting the liquid and pressing the flowers to remove any remaining solvent. The flowers themselves were nearly devoid of color after this, and a highly concentrated blue dye was collected.

The dye obtained this way is water-soluble, air-stable(I've had it exposed to the atmosphere for at least 10 days so far), and is capable of easily staining paper. It's also quite potent; the dye in the vials pictured is at most composed of 10% of the already dilute methanol solution.

Unfortunately I don't have any equipment for chromatography, nor any way of testing the pH to give exact figures. It would be wonderful if someone else could do this and report back, though!

blogfast25 - 30-4-2015 at 09:55

Quote: Originally posted by Amos

Unfortunately I don't have any equipment for chromatography, nor any way of testing the pH to give exact figures. It would be wonderful if someone else could do this and report back, though!

At its simplest, take a narrow strip of filter paper, add a drop of concentrated extract near the bottom of the strip, then put the strip in a vertical test tube with a small amount of methanol at the bottom. As the solvent travels up the paper (capillary action) it may separate the extracted material into its components.

Other solvents like water, EtOH etc can also be used.

The Volatile Chemist - 30-4-2015 at 12:03

The violet idea is very cool! I might have to try it.
Acetone extracts rather well, according to arkoma, at least for roses.

Amos - 30-4-2015 at 12:16

Quote: Originally posted by The Volatile Chemist

The violet idea is very cool! I might have to try it.
Acetone extracts rather well, according to arkoma, at least for roses.

Last year I made an extract from the violets using acetone, and it gradually faded in color to a light brown over the next few days, even in a closed bottle. Either there was some kind of impurity in my hardware store acetone, or acetone and the dye really don't like each other.

The Volatile Chemist - 30-4-2015 at 12:43

How well does oxygen dissolve in acetone? Just a wild guess.

Morgan - 3-5-2015 at 08:36

I happened to see a cluster of petunias growing by the sidewalk and picked one for an experiment. The color changing effect of touching it with a cigarette wasn't all that I hoped for. Other flowers are more dramatic but at least this one changed, from purple to a deep blue. I tried to blow the ashes off but they stuck to the surface and it was starting to wilt. Once picked, these are not long-lived flowers.
For an artistic slant, it might be interesting to try a wicking capillary action to change the color of some flowers with pH or to decorate the petals with some affecting solution or maybe with some carefully applied vapor or heat - hopefully something more unique than hydrangeas and what's already been done. There's probably a lot of strange things you could come up with.

Tidbits
Synchrony between flower opening and petal-color change from red to blue in morning glory, Ipomoea tricolor cv. Heavenly Blue
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3559195/figure/f...
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3559195/

Heaveny blue possible use as a food colorant, very stable in the pH range of 2-8.
https://books.google.com/books?id=1mSCl4Hd5dwC&pg=PA261&...

Fantasma4500 - 3-5-2015 at 08:56

anthocyanins are in many plants, i recall even in leaves, resulting in their colour change
red cabbage is 28.7mg/100g, blueberries is 48mg/100g and elderberries as much as 1217mg/100g
elderberries can be picked in large amounts if you have the plants growing near you, potentially as much as 121.7g anthocyanins could THEORETICALLY be extracted from 10kg elderberries.. i dont know if the 100 grammes is dried out, and/or without seeds, but its still a whole lot more than red cabbage

a proposed solvent for extracting anthocyanins would be 70% EtOH(30% H2O i guess?) with 1% citric acid, i could have gotten some of the numbers wrong

but if youre looking for random show chemistry, anthocyanins is one of the better, i have several times picked random uneatable berries hanging around on bushes and what not, crushed them up and boiled the water to get the anthocyanins into solution, to then play abit around with its colour absorbance properties

elderberries grows mainly after summer, if anybody was really thinking about doing this others than me, i recall also seeing on alibaba that the extracts are around 75% pure anthocyanins, so i guess its quite a struggle to purify.. extracting it with basic pH is best avoided, anthocyanins arent very stable in basic pH, dont know if were talking hours or months or years, it does however at acidic pH store quite well, red wine is my reference for this