I Olivia Ho, 

In order to perform solubility test by saturation method as the above article, you should use an excess of your sample in relation to the solvent amount. In other words, you should saturate the medium with your sample, in order to measure how much of your sample can fully solubilise in that medium, up to its maximum level. After, the sample is centrifuged, and you can quantify from the supernatant  how much of your sample was able to solubilize.

Did you understand me?

I hope I have clarified the solubility test for you.

Best regards,

Juliana

Let's try use little part of ethanol. You can also try to change protocol and use e.g. ethanol injection method to make this solution.

Hi Juliana,

Correct me if I'm wrong:

1) If I want to check solubility in water. I should use water as the solvent?

2) Doenst matter how much solvent is used?Just maintained it for all samples?

3) So if I want to compare before and after spray drying:

Before: maximum maybe 10mg in 5ml h20

After: maximum maybe 10gm in 5ml h20

I should go ahead with 10gm instead of 10mg for after?

4) Must the solvent be in a specific temperature?

5) excess sample i presume presence of precipitate in the solvent

1) Yes, if you want to check solubility in water, you should use water as the solvent. So you can know how much of your sample is able to solubilize in that solvent.

2)It doesn't matter how much solvent is used. It matters that you use an excess of your sample in relation to your solvent. In order to compare samples you should maintain the same amount of the solvent and sample used.

3) I did not understand what you said.

4) Temperature should be the same for all samples if you want to compare each other. Also, temperature is determined depending on what you want to test. For example, I've recently published an article (attached to this answer) and the solubility test was performed at 25°C (room temperature). I used this temperature because my formulation (inclusion complexes) would be applied in water at this temperature to acting as a larvicide.

5) Yes, this excess will be separated by the centrifuge step, and you will be able to use the supernatant to quantify the amount of your sample was able to solubilize.

I hope I have helped you.

Let me know if you have not understand yet,

Best regards,

Juliana

Article β-cyclodextrin inclusion complexes containing Citrus sinensi...

Hi Juliana,

Thanks fore replying.

1) I see from your paper. you stir it for 24 hours. I guess that steps is somewhat similar to vortex and sonification?

2) You mentioned excess amount of sample has to be used.

Because I want to compare before and after spray drying of my sample.

for example in 5ml h20:

Before spray-dry: 10mg excess in 5ml

after spray-dry: 5gm excess in 5ml

Since you said excess required, I should go ahead with 5gm for after spray-dried treatment? 

because my understanding is

if you want to compare before and after spray-drying treatment. I should use the same amount of sample (10mg) to show how many times improvement in solubility. similar to ur paper 

u mention 16-times improvement in solubility. 

wont that only possible, if use the same amount to compare?

thanks~

Hi Olivia Ho,

Sorry for the late response, I was very busy these days.

1) I used magnetic stirring in this case. Because of the time of the experiment (24 hours). I needed to perform solubility test at this time.

2) You should use in both cases the same amount of sample in order to compare. This is also my opinion.

Best regards,

Juliana

I agree completely with you Juliana and I thank you for helping Olivia out. Your very last opinion is also agreeable. Olivia please use 5 gm or 10 gm excess in 5 ml in both cases to achieve comparable results. God bless

As long as the spray drying does not change the chemical composition solubility should be the same before and after the process, however, kinetics might be changed considerably.

Hi everyone,

I would appreciate if you can help me to check, as I am not 100% confident and sure.

Can you see if my calculation for aqueous solubility is correct?

Papers always report aqueous solubility as value μg/mL.

Protocol:

- Excess amount of sample; lets say added 10mg sample to 10ml water; not dissolve= excess

- 10mg sample in 10ml water, magnetic stir for few hours. Centrifuge 2000g; 1minute; followed by Filter paper 1 (not sure if this is necessary step but some paper added a filter step as well; anyone got any view on this?). 1ml Supernatant top up to 20ml methanol and subjected to HPLC.

3) Sample retention time HPLC at 10 minutes= Area 56.96 mAU

Sample standard curve (y (Absorbance) = 350.0X(Concentration (μg/mL))

= 56.96/350.0 = 0.163μg/mL X 20ml (dilution factor) = 3.25 μg/mL

Aqueous solubility of sample = 3.25 μg/mL

IS this correct? I do not need to Add with 10ml of (initial sample solution)