Experimenting with the Megacrop PH and Buffering 📈

[Doulovebeef]

around December 2018…

[anon32470837]

@Doulovebeef

i dont imagine they changed the buffering in V2.0 so we should be able to apply our findings to the new formula.

i have MC2.0 in route, so ill be able to play along with the new stuff.

I have been emailing them about buffering specifically and they did increase the buffering capacity in V2. Dont know how or what they added or changed. Ive been under the weather and not able to follow. Im surorised they have not jumped in to this thread.

New MC formula released last month has improvements in bufferings.
Also, the range for Mega Crop is 5.5 - 6.5 pH.

Up-date on my two samples. The new one, that was crystal clear, now looks just like the first one - slightly cloudy. No precipitate on the bottom of the jar and no scum on top. Im thinking this has to be algae or some form of bacterial growth.

Based on the fact that keeping the jar sealed better delayed the onset of the cloudy, Im guessing its something in the air getting into the water and growing like mad once it gets some Mega Crop. That could be algae or bacteria.

The second sample has had the lid on 90% of the time other than for some stirring when I check PH. Both samples are now up to 5.8.

Unfortunately, I have not been checking regularly so I dont know when the PH started to climb, but I suspect at the same time the cloudiness started up.

I will try some other tests once Im feeling better - kidney stones. I will try keeping a sample in the dark to see if light has an effect or not, plus one totally sealed and not opened at all. Im pretty sure that last test will stay clear. I have had jugs of mega crop mixed for months that looked perfect.

I will also try a sample with AN PH perfect.

Im sure this is an issue with my air/water/environment and not really a Mega Crop problem. Any nute would provide food for algae or bacteria, but a test will be good.

Sorry, too much pain to go through the other posts in detail for now…

[Northern_Loki]

@anon32470837

they did increase the buffering capacity in V2

Great! We’ll have something to compare against.

Re-ran the MC (no MES) titration curve using the new pipette set at 20uL

Compared to a glass pipette, these things are easy. Surprisingly close match on the curve considering that I had to count drops from a needle on the first go around.

[Northern_Loki]

Updated OP with three different MES buffer concentrations along with the two straight MC (v1) titrations.

Moving onto item #4, Phosphate Buffer.

[Esrgood4u]

My ppm from the tap is around 170. The ph is in the high 7s it sometimes even hits 8. Megacrop, calmag and vitalink PK gets it down to around 6.8 at around 900 ppm I’m using Growth Technology ph down https://www.growthtechnology.com/product/ph-down/

[Northern_Loki]

Thanks </></></>

[anon32470837]

@Northern_Loki

edit: One thing that caught my eye from reading that link is how he says “volume” doesn’t matter. Which is a bit misleading the way it reads but I think what he is trying to say is important. Need to relate this back to reality when we consider “how” much buffer ingredient is actually needed in a real system. We’re talking quantities of the OH and H+ and how it changes over time. Will get back to this.

I saw that too. I take it to mean that if you mix up a certain quantity of buffer - like your 0.01M solution - it will buffer a specific amount of added acid - lets say again 0.01M of acid - it wont matter if that amount of buffer (number of moles) is mixed into a 1 liter jar or a swimming pool. It will still buffer the same exact amount of acid - measured in moles. In other words - its the molarity that counts, not the size of the container or the dilution rate.

On another note - Ive been reading and now Im confused again - or still

It looks like you are using the acid form of MES all by itself as a buffer, but I was just reading on some of those links above that they are using the acid form of MES mixed with the salt form of MES to create the buffer. I assume this is the “conjugate salt” thing.

So, MES can work either way or? Im still very vague about this whole weak/strong/acid/base/salt conjugate thing. Now you see it now you dont?

Im not even sure what my question is… hmmmm could be the pills I guess…

EDIT: Love the new graphs! My new question is - has anyone run across any references to how strong a solution of MES is safe to use? I have not seen anything on that yet. I am assuming ‘safe’ doses would be a matter of PPM rather than molarity, so we should be able to dilute the stuff and still have it work - maybe?

[Northern_Loki]

@anon32470837

I saw that too…it wont matter if that amount of buffer (number of moles) is mixed into a 1 liter jar or a swimming pool.

Yes, precisely.
Molarity refers to the number of moles per liter of solution. The way it was stated is somewhat ambiguous. When the volumes are undefined, it’s easier (in my mind) to get a handle on this by simply using moles or grams. Volume really doesn’t matter, then. Or, say something like 100ml of 1M solution. But, I guess that’s how chemists think.

@anon32470837

they are using the acid form of MES mixed with the salt form of MES to create the buffer

That is an option.

When we think of buffers, we are thinking of a weak acid or, perhaps, a weak base as the primary constituent. A weak acid will partially de-protentate and come to an equilibria with the solution. De-protenate meaning, gives up an H+.

This is the MES acid:

This is the conjugate base:

Note the difference between the two. MES acid give up an H+. Once it does that you have it’s conjugate. This is the Brønsted definition of an acid / conjugate. That’s it!

Let’s look at some more:

Acid…Conjugate Base
H20…OH-
NH3…NH2-
H2SO4…HSO4-

Base…Conjugate Acid
H20…H3O+
OH-…H2O
H2NCONH2…H2NCONH3+

Under Brønsted:

If a molecule contributes H+ to solution it’s an acid. Once it contributes the H+ to the solution it becomes the conjugate base of it’s former self.

If molecule wants to absorb an H+, it is the base. Once it absorbs the H+ it become a conjugate acid of its former self.

Now let’s talk strong / weak.
A strong acid will readily want to give up it’s H+ turning itself into a weak conjugate base. The weak conjugate base derived from a strong acid is relative stable and doesn’t strongly attract H+ ions. What this indicates is that the interaction of a strong acid in solution will tend to favor conversion into it’s conjugate base form. It gives up all of it’s H+ ions.

A weak acid doesn’t “as” strongly give up it’s H+ ions but when it does, the conjugate base is likewise formed. The conjugate base may attract H+ ions to convert back into the acid form. An equilibrium is created between the acid and it’s conjugate depending on the concentration of the acid and the quantity of H+ ions in solution. The amount of the weak acid and it’s conjugate base will vary as a result.

So, what this is saying, by having the MES acid in solution, you already have some of it’s conjugate! How 'bout that. Albeit small. By adding more conjugate base, the effect is to alter the ratio and force a shift in the PH. The underlying Ka, pKa remains the same. The point of equilibria is the Ka value (or pKa value when thinking PH).

Alternatively, if we add some OH-, we deplete some of the H+ freely available. The weak acid will try to maintain it’s equilibria by then giving up more of it H+ ions (pulling the solution to a more acidic state by neutralizing some of the OH-). This is the buffering effect.

The chemistry nomemclature is as follows:

HA = weak acid.
A- = conjugate base

For a solution containing a weak acid and it’s conjugate base, the reaction is as follows:

HA + A- → A- + HA

e.g. nothing happens, they happily swap back and forth between an acid and conjugate base.

If we add a strong base (OH-) to the solution:

HA + OH- → A- + H2O

We convert the strong base into the conjugate base and water. Since the OH- is consumed, the PH change is slight.

How about a strong acid:

H+ + A- → HA

The conjugate base reacts with the strong acid converting it into the weak acid.

A salt of the conjugate, in essence, is the addition of an atoms/metal to the conjugate forming a stable compound. A conjugate salt when added to a solution will disassociate into the conjugate and the metal.
For instance:

Acetic Acid (acid) … Sodium Acetate (conjugate salt)
CH3COOH …CH3COONa

Here is an example of PH adjustment using a strong base as opposed to it conjugate salt: https://www.goldbio.com/documents/3550/MES+Buffer+0.5M+Stock+Solution+with+table.pdf

That would be my current understanding on how this stuff works…

@anon32470837

has anyone run across any references to how strong a solution of MES is safe to use?

I have paged through some papers on MES concentrations and, for certain crops, no detrimental effect. Other crop, they see a detrimental effect when exceeding certain concentrations.

Stabilization of pH in solid-matrix hydroponic systems.b4d64c4bbeda07241088152de2dab332e873 (1).pdf (83.5 KB)

2-[N-morpholino]ethanesulfonic acid (MES) buffer or Amberlite DP-1 (cation-exchange resin beads) were used to stabilize substrate pH of passive-wicking, solid-matrix hydroponic systems in which small canopies of Brassica napus L. (CrGC 5-2, genome : ACaacc) were grown to maturity. Two concentrations of MES (5 or 10 mM) were included in Hoagland 1 nutrient solution. Alternatively, resin beads were incorporated into the 2 vermiculite : 1 perlite (v/v) growth medium at 6% or 12% of total substrate volume. Both strategies stabilized pH without toxic side effects on plants. Average seed yield rates for all four pH stabilization treatments (13.3 to 16.9 g m-2 day-1) were about double that of the control (8.2 g m-2 day-1), for which there was no attempt to buffer substrate pH. Both the highest canopy seed yield rate (16.9 g m-2 day-1) and the highest shoot harvest index (19.5%) occurred with the 6% resin bead treatment, even though the 10 mM MES and 12% bead treatments maintained pH within the narrowest limits. The pH stabilization methods tested did not significantly affect seed oil and protein contents.

An evaluation of MES (2(N-Morpholino)ethanesulfonic acid) and Amberlite IRC-50 as pH buffers for nutrient solution studies.

All buffering agents used to stabilize pH in hydroponic research have disadvantages. Inorganic buffers are absorbed and may become phytotoxic. Solid carbonate salts temporarily mitigate decreasing pH but provide almost no protection against increasing pH, and they alter nutrient absorption. Exchange resins are more effective, but we find that they remove magnesium and manganese from solution. We have tested 2(N-Morpholino)ethanesulfonic acid (MES) as a buffering agent at concentrations of 1 and 10 mol m-3 (1 and 10 mM) with beans, corn, lettuce, tomatoes, and wheat. MES appears to be biologically inert and does not interact significantly with other solution ions. Relative growth rates among controls and MES treatments were nearly identical for each species during the trial period. The pH was stabilized by 1 mol m-3 MES. This buffer warrants further consideration in nutrient research.

Evaluation of buffer toxicity in tobacco cells:
Borgo_2017.pdf (792.1 KB)

Haven’t gone through the literature thoroughly. Beat me to the punch. Keywords, for instance, Hydroponic MES buffer.

[anon32470837]

@Esrgood4u

So since megacrop has changed its ingredients does this thread even matter anymore?

Almost forgot to respond to this - yes, I think it does. The main reason is that this thread isnt so much about Mega Crop specifically as it is about buffering in general. Mega Crop just happens to be the focus nute.

Anything we learn here should be applicable to any nutrient you use if you are wanting better control of the PH in the solution.

At least, I hope so

[anon32470837]

@Northern_Loki

When we think of buffers, we are thinking of a weak acid or, perhaps, a weak base as the primary constituent. A weak acid will partially de-protentate and come to an equilibria with the solution. De-protenate meaning, gives up an H+.

This is the MES acid:

All of that helps - but Im going to have to go through it a few more times…
Thanks!!

[Northern_Loki]

Ok, decided to look at the citric acid instead of the phosphate buffer for the moment.

The formulation of MC is using mono-potassium phosphate as a primary ingredient which is the weak acid component of the phosphate buffer we’d be interested in. The conjugate is dipotassium phosphate and is a base. In order to increase the buffering capacity against the upside, we’d add more mono-potassium phosphate to formula. The feeling is the quantity needed would throw too much potassium and phosphate into the solution. So, I’m going to defer this for the moment to think about it.

Here’s a look at a citric acid buffer calculated to 20mM in the 500ml MC solution. I don’t know the plant safe amounts for the citric acid and it’s conjugate. And, I’m guessing that this concentration is likely exceedingly high. An interesting note is that the previously observed precipitates at high PH are not noticeable until >9PH with this solution.

edit: updated graph to add titration of 5mM citric acid in 500ml MC solution.
edit: updated graph to add titration of 10mM citric acid in 500ml MC solution.
edit: normalize starting point on graph to PH4.

[anon32470837]

@Northern_Loki

Beat me to the punch. Keywords, for instance, Hydroponic MES buffer.

Still trying to decode this, but it looks to have some good info.

b4d64c4bbeda07241088152de2dab332e873.pdf

[anon32470837]

@Northern_Loki

Here’s a look at a citric acid buffer calculated to 20mM in the 500ml MC solution. I don’t know the plant safe amounts for the citric acid and it’s conjugate.

At first look, the citric acid doenst seem to be nearly as effective as the MES - by a lot.

So, is this a single buffer element or did you also add the conjugate base to the citric acid?

So far, it looks like all these tests are with the acid component only rather than mixing acid with conjugate base or salt?

[Northern_Loki]

@anon32470837

At first look, the citric acid doenst seem to be nearly as effective as the MES - by a lot.

Yes. There is a significant difference. We are on the far end of the pKa for citric acid while for MES we are closer to the pKa being in the middle of the range for the PH we’d want.

Oh, and I really have no idea of what is a safe amount of citrate buffer would be. The only references that indicate concentrations that I have found so far have to do with soil remediation and plant uptake. They are using citric acid applied to the soil in that case. For that, it appears the concentrations were higher than what we’ve tried here. So, I could use some guidance or thoughts from anyone who may have experience with citric acids in a hydro-solution. One thing is for certain, a citric acid buffer is not to be used in an Aquaponics set-up.

@anon32470837

these tests are with the acid component only rather than mixing acid with conjugate base or salt?

Ahhh, but the conjugate is already hidden in there
HA + OH- → A- + H2O
I was not looking to “pre” adjust the buffer PH since we are doing a titration curve on the slurry. In essence, we are making the conjugate on the fly! Three KOH’s produces potassium citrate + H20 as the conjugate, I believe.

Hence, this is one of the reasons I’ve deferred looking at the phosphate buffer. For a phosphate buffer, the weak acid is the mono-potassium phosphate and the conjugate salt is dipotassium phosphate. MC already has the weak acid in the formulation. By adding the conjugate base, all that we’d be doing is moving the PH more basic. We aren’t adding more buffer capacity to the upside by doing this (downside is a different matter but we are already starting off acidic). In order to add more capacity, we’d have to add more mono-potassium phosphate. Perhaps this is why MC notes that they’ve increased the buffering in V2 by the addition of additional mono-potassium phosphate?

I think this is what we are looking at (with the arrows being bidirectional between the acid and base)

acid(HA) … conjugate (A-) … conjugate salt
KH2PO4 → KHPO4- +(H+) → K2HPO4

I may try some pre-PH’ed buffers that are a combination of a phosphate and acid such as a phosphate-citrate buffer to see if there are any significant differences.

[anon32470837]

More new stuff to process. Thanks!

[Doulovebeef]

I’m following along, if there’s anything I can do to assist just let me know. Ur grasp on chemistry is much stronger than mine

[Northern_Loki]

Ahhh, well, figuring it out as I go my friend. Thoughts are certainly welcome. And, if you have some of the MC version 2, any observations that you have would be interesting!

[Doulovebeef]

I never worked with mc v1 but the smell of v2 is, well, strong…

Once I bring myself to open the bag I’ll let ya know.

I have a NBC respirator around here somewhere…

[Northern_Loki]

I’ve added a low concentration MES titration at 0.000854M and 0.002M free acid in conjuction with MC (v1) at a 1.7EC.

See the OP for the plot of the titration curve and the transfer function.

[anon32470837]

I see the new plots and notes in the first post. Very very helpful!

So, am I thinking about these formulas correctly?

Is it ok to call these x multipliers a slope or buffer factor or ratio? So, 2.9903 would be the slope of the plain MC graph, and 2.2407 would be the slope of the Megacrop + 0.852mM MES?

@Northern_Loki

MC
1.7EC Megacrop : y=2.9903x + 5.4262 (5.6<=PH<6.5)
MC + MES Buffer
1.7EC Megacrop + 0.852mM MES free acid : y=2.2407x + 5.3674 (5.6<=PH<6.5)
1.7EC Megacrop + 2mM MES free acid : y=1.3363x + 5.2768 (5.6<=PH<6.5)
1.7EC Megacrop + 5mM MES free acid : y=0.67x + 5.2229 (5.6<=PH<6.5)

Then, adding the 0.852mM of MES to plain MC increases the buffer factor by 2.9903/2.2407 = 1.33

Does that mean that if the PH in my rez with plain MC is going up say 0.5 PH in 12 hours, that adding 0.854mM of MES would extend that to 12 x 1.33 = 15.9 hours?

And if I added MES at 2mM concentration, the time for that same 0.5 PH increase would go to 2.9903/1.3363 x 12 = 26.8 hours?

P.S. You are putting in a lot of time, thought, and spending a significant chunk of change getting us this information. This is way above and beyond. I have not seen anything even vaguely close to this amount of information, at this level of detail and with this quality, clarity of presentation by anyone ever on any of the forums. Im talking about the theoretical background info and explanations as well as the data collection, graphs etc.

This thread needs to be a FAQ.

Thank you sir!!!