Hello dear researchers,
I'm asking about the concentrations that I must prepare to analyse Organic Extracts (of polyphenols) by HPLC, and Essential Oils by GC,GC/MS. I have ideas (that concentration shouldn't be more than 1mg/ml) but I need more clearings about. Any advice before using it, what should I know ? what is preferable to do ? from your experience and wisdom.
Thank you in advance.
Dear Dr Radjah,
I would not use ethanol (as well as methanol) for several reasons.
Being the solvent it is present in huge amount and MS could be damaged and the exposure of the filament to the solvent vapour flow will reduce the filament life. Moreover, the presence of these solvent will produce very bad peaks when eluting.
There are some instrument settings to minimize these problems (i.e. a programmed turn on and off the detector; changing split ratio) but if you may solubilize the samples in a different solvent it should be better.
Another suitable solvent is ethyl acetate. While chloroform or dichloromethane should be avoided since plastic parts (if present) of the instrument might be damaged.
Moreover, if you need to recover the EO it may be easily done by exposing the solution to a nitrogen (or air stream) since these solvents are highly volatile. The same is not possible if ethanol was used, and require also the heating of the sample. But in these conditions also the essential oil components may be evaporated.
Hey there,
I dont know about GC, but the proper concentration for HPLC considerably depends on the chromatography conditions such as type of column, solvents, and etc. In HPLC, sharp peaks are appreciable; therefore, the best approach is to inject a little more concentrated sample (I say not more than 500 μg/mL). Then, if you took broad peak/s, dilute your sample further. In contrast, if you did not see any peak/s or they were too small, use more concentrated sample. Keep in mind that broad peaks may cause by different reasons too; however, if you are following a standard procedure or a valid published article, then it is mostly due to high concentration.
I have got good looking peaks that are required for proper analyzing with concentration of 100 μg/mL with a number of compounds.
Good Luck
Good information by Dr. Seyed. I'm following your project. Best regards
Many thanks Mr Seyed for your valuable answer. I really appreciate it !
For what concern the essential oils analysis in GC-MS generally a concentration of 1 mg/ml in a suitable solvent i.e hexane or diethyl ether is used to prepare a batch solution. Then you may inject 1 or 2 microliters of this solution.
Thank you for the answer Dr. Alessandro, I usually prepare essential oil in EtOH. Is it suitable for GC-MS ?...if no, what are the reasons ?
Dear Dr Radjah,
I would not use ethanol (as well as methanol) for several reasons.
Being the solvent it is present in huge amount and MS could be damaged and the exposure of the filament to the solvent vapour flow will reduce the filament life. Moreover, the presence of these solvent will produce very bad peaks when eluting.
There are some instrument settings to minimize these problems (i.e. a programmed turn on and off the detector; changing split ratio) but if you may solubilize the samples in a different solvent it should be better.
Another suitable solvent is ethyl acetate. While chloroform or dichloromethane should be avoided since plastic parts (if present) of the instrument might be damaged.
Moreover, if you need to recover the EO it may be easily done by exposing the solution to a nitrogen (or air stream) since these solvents are highly volatile. The same is not possible if ethanol was used, and require also the heating of the sample. But in these conditions also the essential oil components may be evaporated.
Dear Dr. Radjah,
Concerning the analysis of organic extracts (polyphenols) by HPLC-UV and/or HPLC-MS, in general the extract is solubilized in methanol HPLC grade at concentration of 10 mg/mL and the volume to be injected in column is 10 μL.
Thank you all dear researchers for sharing your wisdom with me .. thank you so much !
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