Technically YES.

You are going to extract something from the raw material so after extracting with one solvent that component will be extracted and there will be very less component left in that sample. In order to extract more component or to compare the extraction yield, you have to use new sample. However, you can use the same sample if your purpose is not to compare the extraction yield with different solvents and you just want to extract maximum component from that sample.

Hope you got your answer

Technically YES.

You are going to extract something from the raw material so after extracting with one solvent that component will be extracted and there will be very less component left in that sample. In order to extract more component or to compare the extraction yield, you have to use new sample. However, you can use the same sample if your purpose is not to compare the extraction yield with different solvents and you just want to extract maximum component from that sample.

Hope you got your answer

As it is known, the extracts may be mixtures of compounds of different polarity. By changing the solvent you can also change its polarity. In this way, the compounds can be selectively extracted with a different polarity, e.g. fatty acids (non-polar) and polyphenols (polar). In this case, the charge may remain the same until all of the useful compounds will be extracted. Otherwise, the charge should be changed. Of course, sometimes it is cheaper or faster to run with new samples.

Generally, it is not necessary to take fresh samples each time with different solvents, but it depends on what you are expecting from the extract. for a general extraction, start with a nonpolar solvent like hexane, which extract the non polar compounds like waxes, hydrocarbons and other low polar terpenoids etc. extract the same plant powder, after evaporating hexane completely using a polar solvent like methanol, which extracts most of the polar compounds. Thus sequential extraction of the same plant material is the preferred technique, where you will getlow polar and polar compounds separately in the two extracts. but if you use fresh plant material for the second extraction using methanol, you will end up with some low polar compounds as well in the methanol extract.

Not necessary. If you have a limited amount of plant material, then you weigh it and pack the soxhlet with the material. Run the solvents in increment of polarity till consistent TLC is seen (approx 25-30 flasks). Then change the solvent with the next higher polarity. This way you can get extracts from the plant from different solvents.

Now after you finish, don not throw the plant material. Air dry it and take aqueous extracts.

Please refer to my publications on this topic and also of prof M. Ali (Jamia Hamdard).

For successive solvent extraction, you have to use the same exhausted drug after each extraction. This way you will fractionate the components of the crude drug according to their solubility in the solvents in order of increasing polarity. 

If you want pure extract in a particular solvent, then you have to use separate sample every-time. 

 No, not necessary you need not have to have new samples of plant for each solvent during soxhlet extraction. 

Hi

When you change solvent, its means that you change a polarity of the solvent in consequence the solubility of the specific molecules present in the plant can be changed.

If you targeted molecules are lipo- soluble and hydro soluble you don't need to change the raw material each time.

so the conclusion is just for phytochemical analysis same sample with different solvents is best..but if we want large quantity of particular component wehave to use change sample for each solvent. is that right??

Hi Kavitha 

Even if you want large quantity of a particular component, you will have to do it with the same sample and different solvents. This is the best way to avoid problems in isolation of single compound. There may be other components which are also soluble or partially soluble in the same solvent and would interfere with the component of interest. 

If you are sure that only the compound of interest is coming in a particular solvent, you can do extraction directly with that solvent. This purely depends on the nature of compound. When we don't know, we follow successive solvent extraction to avoid problems later. 

Regards 

hello Alok sir

thank you for your response and support. my doubt is, for example if a want to extract mainly the alkaloids; these alkaloids are soluble both in methanol and ethanol right. then when i am doing series extraction of same sample with different solvents. the alkaloid content will be present in both the solvent extract. 

so if i want to extract that kind of one particular phytochemical  component which should be concentrated in one solvent then changing of sample each time along with solvent will be that necessary?  

Yes the alkaloid would appear in both extracts. 

Once you take a sample, you extract with any solvent, say A, and do it till all the A soluble material is extracted from the sample. Now if this extract has your compound of interest, then to increase the quantity of A soluble extract, you will have to take new sample because the old sample is already exhausted. This is it. 

Or your compound doesn't come in A, but comes in B or C, you will have to follow the same procedure with the new drug sample to get the B or C soluble component. This is successive solvent extraction. 

Hope you got my point. 

thank you sir. I got your point.

Then how can we estimate the percentage(concentration of perticular phytochemical present in the extract (in each solvent ) by soxhlet.

No,  you should use the same plant sample, what you should do is to dry the previously wet sample from its solvent then repack it and use the next solvent which is supposed to be of higher polarity and so on, it is supposed to be successive extraction. God luck

Soxhlet will give you the extract. You can then determine the presence of phytoconstituents by qualitative chemical tests. Once confirmed about the presence of a particular compound in the extract, try to isolate it by column chromatography. As far as the concentration of a particular phytochemical in the extract, this can be determined by HPLC or HPTLC which will give a quantitative estimate of the phytochemicals present. So you can find out the amount of particular compound in the extract. 

Thank you sir.