[quantumnoodle]

Hi everyone,

I am currently formulating a liquid laundry detergent and I need help in stabilizing the pH of the detergent.

This is my first time writing here and my first time handling this kind of task (I’ve no experience so I need to learn a lot from people). I’ve been doing a lot of research on how to stabilize the pH of liquid detergents, however, from the past few days, I had no luck. I tried adjusting the ratio of surfactants and foam booster. I also tried adding citrate and triethanolamine, however, pH decreases drastically after the addition of thickener (ex. started at pH 9.22, after addition of salt pH is already at 8.86).

I've been feeling down lately because of this though, I know it’s going to be trial and error however it seems nothing is working.

Any form of help would be much appreciated and any reading or reference recommendations will also be of great help.

[AWK]

Not enough data.

[quantumnoodle]

Hi everyone,

I am currently formulating a liquid laundry detergent and I need help in stabilizing the pH of the detergent.

This is my first time writing here and my first time handling this kind of task (I’ve no experience so I need to learn a lot from people). I’ve been doing a lot of research on how to stabilize the pH of liquid detergents, however, from the past few days, I had no luck. I tried adjusting the ratio of surfactants and foam booster. I also tried adding citrate and triethanolamine, however, pH decreases drastically after the addition of thickener (ex. started at pH 9.22, after addition of salt pH is already at 8.86).

I've been feeling down lately because of this though, I know it’s going to be trial and error however it seems nothing is working.

Any form of help would be much appreciated and any reading or reference recommendations will also be of great help.

Regarding the formulation, I am using the following ingredients for the base:

Linear alkylbenzene sulfate
Sodium lauryl ether sulfate
Caustic soda flakes
Coco diethanolamine/ide
Water

I am also adding the following to the formulation:

Fragrance
Colorant
Salt (for my thickener)

I tried adjusting the ratio of the surfactants, first by increasing their concentrations in the formulation, however, nothing happened. The pH (as is) dropped below 8 at the end of the day (I am targeting a pH of 9 - 10).

I also tried adding citrate and neutralizer to increase the pH, however, as mentioned, pH dropped drastically.

I am planning to decrease the concentrations of the surfactant, though I have a few concerns with this:

1. %active will decrease thus, lowering the cleaning efficiency
2. foam height will decrease

Hope this data helps. Thanks in advance.

[AWK]

You have at least 3 substances that influence the pH of the mixture significantly and without knowing all the concentrations it is difficult to advise anything.
Besides, the Forum does not provide advice to producers remotely. Contact an on-site chemist.

[Corribus]

I have not much advice on this problem generally, but I will add that I would not consider a drop from 9.2 to 8.9 to be "drastic". Whether this small drop is significant depends a lot on how you are measuring the pH, how good your standards are, what standards you are using, how well your meter is calibrated and the range it is calibrated over, etc. My suggestion would first be to ensure your analysis of pH is up to snuff before you worry about the effect of your formulation, especially since this is your "first time handling this task". Validation of your method would be a first step in any real R&D laboratory, and measuring pH accurately and precisely isn't as easy as people think it is - particularly in complex mixtures with very high ionic strength.

[quantumnoodle]

You have at least 3 substances that influence the pH of the mixture significantly and without knowing all the concentrations it is difficult to advise anything.
Besides, the Forum does not provide advice to producers remotely. Contact an on-site chemist.

Hi, thank you for pointing this out. I'd consider these on my next experimentation.

[quantumnoodle]

I have not much advice on this problem generally, but I will add that I would not consider a drop from 9.2 to 8.9 to be "drastic". Whether this small drop is significant depends a lot on how you are measuring the pH, how good your standards are, what standards you are using, how well your meter is calibrated and the range it is calibrated over, etc. My suggestion would first be to ensure your analysis of pH is up to snuff before you worry about the effect of your formulation, especially since this is your "first time handling this task". Validation of your method would be a first step in any real R&D laboratory, and measuring pH accurately and precisely isn't as easy as people think it is - particularly in complex mixtures with very high ionic strength.

Hi, I haven't much thought about this but, our work instructions suggest to measure liq det samples 'as is' (no dilution, however, some study suggest to measure pH of liq det at 1% solution) using a calibrated pH meter. I will consider your suggestion and will take a look into our method and may be conduct a re-validation. Thank you for the help, much appreciated.

[Corribus]

For that matter, you will want to make sure you are using the right pH meter for the intended purpose. Liquid detergents are usually pretty viscous, and no every probe is suitable for measurement in viscous solutions, see, e.g.,

https://www.coleparmer.com/blog/2013/01/31/measuring-ph-in-viscous-samples-too-hard-to-handle/

Also note that diluting your solution will also affect your pH reading.