My response would be: Looking at the two chromatographs, the approach to peak area measurement is not the same (ie you are not comparing the same data) the main point is that lab A have treated the shoulder at RT 7.887 as a separate peak. Looking at lab B's report, you can see a similar shoulder which is not treated as a separate peak.
Of course any assessment is based on the principle that the chromatographic conditions are suitable to separate impurities from the desired peptide.
In the end, you have to either make the peptide yourself or assume that the supplier can provide the product at the specification they have stated - this isn't saying that you shouldn't perform your own QC when you receive the sample (remember that whatever data they provide is only true about the sample they measured at that time and it is possible that the sample you receive may be of different quality for any number of reasons)
If you are interested in other possible suppliers check out ChemSpider (I think the correct record is: http://www.chemspider.com/Chemical-Structure.8136267.html)
Thanks for your response. It is my understanding that the sample reports of the HPLC and results will always be variable meaning it is an average taken at a certain point in time as the structure itself will never be completely uniform or the results consistently exact et. However my own or third party QC to verify structure and purity should be within the stated or same parameters.
Basically, what you are saying is that the HPLC reports do reflect the stated percentages in regards to purity and the separation of impurities (albeit by different methods/means) but what it comes down to is whether or not I can lend credence to the supplier and that they will supply the peptide at the stated purity from these reports, correct?
LAB A has stated that they are going to bring the purity level up to 98%, they just wanted me to verify that the compound/structure (HNMR report) is satisfactory before they proceed in furthering the purification and yield et.
As stated, I have sent them an email stating that the HNMR report is unsatisfactory due to the missing Aldehyde signal and the ppm being cut off on the report at the critical region et. They have responded by forwarding the information onto their engineers and will forward a revised document. So I will likely post that for further feedback once it arrives.
In my humble opinion, I don't think LAB B would go to the trouble of fabricating an HPLC when they have produced (what appears to be) supportive data (HNMR and Mass Spec) that is satisfactory in terms of verifying the compounds identity et. The quality/resolution of the report is an issue in itself but the
data, from what others have stated, seems to be accurate with the desired compound. Would you agree with this statement?
I have in fact contacted a 3rd supplier and received an initial quote with a guarantee of purity and identity of the peptide with supportive data of a HPLC and Mass Spec. They will not however, produce and provide tests until I commit to an order, at which point, they will provide a written guarantee in regards to the purity and identity by internal test reports et. Obviously if things were to not mesh, the guarantee would be void and funds reimbursed (as you outlined).
Essentially, it would seem that LAB B has the correct or desired structure and purity, so purchase from this lab and third party verification is an option with this supplier. I will however, perhaps wait on LAB A to correct and forward the HNMR so it includes the missing information. Still,
some of the other experts in this thread have stated that LAB A seems to be slightly off not only due to the missing Aldehyde signal but also on the subsequent structure itself.
Thank you again for your time and comments.