Weigh another small rotary evaporator flask. Dissolve and transfer the extract with a volatile solvent (either the one you used for the extraction or another similar solvent with a lower boiling point).

Rotary evaporate Again. Weigh the flask with the extract and subtract the weight of the empty flask.

- Dissolve extract to 40% concentration and perform serial dilutions.

If you have very little extract, transfer it to a pre-weighed and lighter container. Dry it with a nitrogen flow or under vacuum.

If you want a solution with a specific concentration in terms of dry matter (rather than a solution with the concentration of the thick extract you got in the rotary evaporator), I would recommend extracting the resulting extract from the evaporator, drying it to a constant weight, and then diluting it.

Alternatively, you can determine the moisture content of the extract (e.g. in an infrared moisture analyser), then recalculate and dilute your thick extract with the moisture present in the thick extract

Marlyn Sabocojan The extract appears to be semi solid either because of the metabolites or because of incomplete dryness in rotavap. Before preparing the concentrations, the extract must be subjected to complete dryness in desiccator or oven. Then dry weight could be taken and percentage solutions could be prepared in the respective solvent

To prepare solutions with concentrations of 20%, 30%, or 40%, you need to decide whether you are working with weight/volume (w/v), weight/weight (w/w), or volume/volume (v/v) percentages. Here’s how to prepare each type:

1. Weight/Volume (% w/v)

This means grams of solute per 100 mL of solution.

• 20% w/v: Dissolve 20 grams of solute in enough solvent to make 100 mL of solution.
• 30% w/v: Dissolve 30 grams of solute in enough solvent to make 100 mL of solution.
• 40% w/v: Dissolve 40 grams of solute in enough solvent to make 100 mL of solution.
• 2. Weight/Weight (% w/w)

This means grams of solute per 100 grams of solution.

• 20% w/w: Mix 20 grams of solute with 80 grams of solvent (for a total of 100 grams of solution).
• 30% w/w: Mix 30 grams of solute with 70 grams of solvent.
• 40% w/w: Mix 40 grams of solute with 60 grams of solvent.

3. Volume/Volume (% v/v)

This means milliliters of solute per 100 mL of solution.

• 20% v/v: Add 20 mL of solute to enough solvent to make 100 mL of solution.
• 30% v/v: Add 30 mL of solute to enough solvent to make 100 mL of solution.
• 40% v/v: Add 40 mL of solute to enough solvent to make 100 mL of solution.

Hi,

You may use the web tool to calculate

https://www.alfa-chemistry.com/solution-dilution-calculator.htm

https://www.alfa-chemistry.com/mass-molarity-calculator.htm