Chromatography Forum

Dear All,

My name is Alberto Otero, Pharmacist.My question is based on Eucalyptol 100 % as raw material.Can I really demonstrate that two different suppliers of Eucalyptol 100 % are exactly the same using GC ?.

Waiting for your reply,

Thank you very much and kind regards,

Alberto Otero.

Assay procedure from USP:
Assay preparation— Transfer about 90 mg of eucalyptol, accurately weighed, to a 100-mL volumetric flask, dilute with methanol to volume, and mix.
System suitability solution— Prepare a solution of limonene and eucalyptol in methanol containing 0.2 mg per mL and 0.9 mg per mL, respectively.
Chromatographic system (see Chromatography 621)—The gas chromatograph is equipped with a flame-ionization detector and a 0.32-mm × 60-m fused-silica capillary column coated with phase G16. The temperatures of the injection port and the detector block are maintained at 250. The carrier gas is helium adjusted to a column head pressure of 30 psi. The split flow rate is about 50 mL per minute. The column temperature is initially maintained at 60, then increased to 200 at the rate of 6 per minute, beginning at the time of injection. Chromatograph the System suitability solution, and record the peak responses as directed for Procedure: the resolution, R, between limonene and eucalyptol is not less than 2.0; and the column efficiency determined from the eucalyptol peak is not less than 150,000 theoretical plates.
Procedure— Separately inject equal volumes (about 1 µL) of the Assay preparation and of methanol into the chromatograph, record the chromatograms, and measure the areas of the peaks. Identify by their retention times any peaks present in the chromatogram obtained from the Assay preparation that correspond to those in the chromatogram of methanol. Calculate the percentage of C10H18O in the portion of Eucalyptol taken by the formula:
100(rU / rT)
in which rU is the eucalyptol peak response obtained from the Assay preparation; and rT is the sum of the peak responses obtained from the Assay preparation, other than the responses corresponding to those in the chromatogram of methanol.

For non-USP assay, you need a sample you trust, like a reference standard. Make that up to a set concentration, make up similar concentration of the incoming material, and inject and compare the Area/concentrations.

The devil is in the details.

"exactly the same" ?

No, not by GC, nor by any single analytical technique. Even two lots of material from the same vendor may not be "exactly the same".

You set a very high bar to reach using those words.

You may be able to say that two samples have nearly the same content of a chemical, but a simple single test can NEVER PROVE they are "exactly the same".

best wishes,

Rod

We get asked all the time if vendor #2 material is the same or "identical" to that of vendor #1. We reply that we can do certain tests but the best we can report is "indistinguishable" from vendor #1 product.

Assay procedure from USP:
Assay preparation— Transfer about 90 mg of eucalyptol, accurately weighed, to a 100-mL volumetric flask, dilute with methanol to volume, and mix.
System suitability solution— Prepare a solution of limonene and eucalyptol in methanol containing 0.2 mg per mL and 0.9 mg per mL, respectively.
Chromatographic system (see Chromatography 621)—The gas chromatograph is equipped with a flame-ionization detector and a 0.32-mm × 60-m fused-silica capillary column coated with phase G16. The temperatures of the injection port and the detector block are maintained at 250. The carrier gas is helium adjusted to a column head pressure of 30 psi. The split flow rate is about 50 mL per minute. The column temperature is initially maintained at 60, then increased to 200 at the rate of 6 per minute, beginning at the time of injection. Chromatograph the System suitability solution, and record the peak responses as directed for Procedure: the resolution, R, between limonene and eucalyptol is not less than 2.0; and the column efficiency determined from the eucalyptol peak is not less than 150,000 theoretical plates.
Procedure— Separately inject equal volumes (about 1 µL) of the Assay preparation and of methanol into the chromatograph, record the chromatograms, and measure the areas of the peaks. Identify by their retention times any peaks present in the chromatogram obtained from the Assay preparation that correspond to those in the chromatogram of methanol. Calculate the percentage of C10H18O in the portion of Eucalyptol taken by the formula:
100(rU / rT)
in which rU is the eucalyptol peak response obtained from the Assay preparation; and rT is the sum of the peak responses obtained from the Assay preparation, other than the responses corresponding to those in the chromatogram of methanol.

For non-USP assay, you need a sample you trust, like a reference standard. Make that up to a set concentration, make up similar concentration of the incoming material, and inject and compare the Area/concentrations.

I appreciate all your help !!!

Thanks a lot !

Alberto.

We get asked all the time if vendor #2 material is the same or "identical" to that of vendor #1. We reply that we can do certain tests but the best we can report is "indistinguishable" from vendor #1 product.

Dear Consumer Products Guy,

So, my question is if:

eucalyptol A 100 % is in range with eucalyptol B 100 % , just at least 98,5 % of molecule 1,8 cineol are both raw materials the same?

Thank you very much and kind regards,

Thanks a lot !

Alberto.

We get asked all the time if vendor #2 material is the same or "identical" to that of vendor #1. We reply that we can do certain tests but the best we can report is "indistinguishable" from vendor #1 product.

Dear Consumer Products Guy,

So if the report is indistinguishnable, what it really means in a scientific point of view?

Thank you vaery much and kind regards,

Alberto.

The devil is in the details.

"exactly the same" ?

No, not by GC, nor by any single analytical technique. Even two lots of material from the same vendor may not be "exactly the same".

You set a very high bar to reach using those words.

You may be able to say that two samples have nearly the same content of a chemical, but a simple single test can NEVER PROVE they are "exactly the same".

best wishes,

Rod

Dear Rod,

So two raw materials (in this case from harmonized by Food Chemical Codex) with the same molecule in characteristics can never be really the same?

So if i have eucalyptol 100 % with supplier A for example, i´ll never be able to change for supplier B in case of dissapearation of supplier A ?

Thank you very much and kind regards,

Alberto.

Realize the level at which 'exactly the same' can be understood.

What if one lot of eucalyptol (so called 100%) contains 4 ppm water.

And another lot of eucalyptol contains 9 ppm water.

1. Are they exactly the same?

2. Would GC-FID show a difference?

3. Are they indistinguishable by GC-FID?

Answer:

1. NO

2. NO

3. YES

I hope you see the point I have tried to make.

Some 'impurities' may be VERY toxic, even at a 1 ppm level. So one lot of a chemical might be harmless, while another lot of the same chemical might be deadly.

"Exactly the same" are words that a sensible chemist NEVER uses.

best wishes,

Rod