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- Posts: 10
- Joined: Sat Mar 27, 2010 8:53 pm
Greetings,
Sincere thanks for your responses and constructive criticism. I try to keep it brief, because I understand that your time is valuable.
Yeah, it's still the statement that "any C18 will do" that I question, and I have no lab. I do intend to hire a contract lab for this method transfer and another lab for method validation. For now, I have no lab.
Because I am legally liable for the results, which are subject to GLP, the details matter to me, and yeah, I have no formal training nor experience with LC, just book learning and talking with various experts over the last year. Before hiring a chemist (contract lab) for the required analytical (& preparative) chemistry, I would like to understand the specifications to the labs, the columns, the solvents, and the conditions, why these specs would work, and what to vary, if it fails.
It's not that I am not listening to the advice of experts, but various experts can have various opinions. Consultants, like experts, sometimes contradict themselves. The history of science is full of raging debates and bitter disputes of what the objective reality is and how to see it optimally. I'm also just naturally sceptical of experts.
Nevertheless, if nobody has used C18 with hexane, then why not try it, as you suggest? I agree. I accept this advice, pending selection of a competent laboratory. As previous stated, I have no lab.
Before hiring a lab, I still have questions concerning the specifications to the lab:
If hexane is too strong a solvent, then what if we mixed hexane with ethanol (though not in Germany, where it is taxed more) or methanol 50/50 ?
For less solvation, what if we lowered the flow or lowered the injection volume, or even used hexane:ethanol/methanol 10:90 ?
By the way, can someone please give me an expert opinion of the review of columns by Mac-Mod (linked to my previous posting and also available by searching the www.mac-mod.com website, and you better believe that I have nothing to do with Mac-Mod, so this most certainly is not a sales pitch for them nor their products), and one of the sponsors of this website (not some lipophilic antipolar website according to a poster) ? This review seems believable to me, but perhaps this is because I am naive and gullible, wet behind the ears, naked in the woods, so I ask you, the experts, about the selection of the columns. So I will take one or all of the three columns that would most match the analyte, according to this C18 column review, because no expert can tell me why not, specifically an Inertsil ODS-3, Kromasil C18, or Develosil ODS-MG column. What these columns appear to have in column, by the way, at least according to the websites of their suppliers, is a much greater internal surface area, particularly with smaller particle sizes, compared with other C18 columns, though the details ("carbon load", ...) were not clear to me. If you think that the C18 column review by Mac-Mod is nonsense, completely biased, unreliable,or incomplete, then please tell me. You are the experts.
I accept the advice to go back to the library and to read books about development of HPLC methods, but most of these books are not specific to lipids found in natural products nor to these specific three columns. Mostly, they are oriented to Rx products & methods. I did read the earlier website and other websites about lipids, but found no answers. Also, this topic is more about the modification and optimization of a method, than it is about the development of a method.
If you are as smart as you think you are, then you should have answers to the simple questions in this posting.
Sincere thanks for your time and attention.
Regards,
Ben
Sincere thanks for your responses and constructive criticism. I try to keep it brief, because I understand that your time is valuable.
Yeah, it's still the statement that "any C18 will do" that I question, and I have no lab. I do intend to hire a contract lab for this method transfer and another lab for method validation. For now, I have no lab.
Because I am legally liable for the results, which are subject to GLP, the details matter to me, and yeah, I have no formal training nor experience with LC, just book learning and talking with various experts over the last year. Before hiring a chemist (contract lab) for the required analytical (& preparative) chemistry, I would like to understand the specifications to the labs, the columns, the solvents, and the conditions, why these specs would work, and what to vary, if it fails.
It's not that I am not listening to the advice of experts, but various experts can have various opinions. Consultants, like experts, sometimes contradict themselves. The history of science is full of raging debates and bitter disputes of what the objective reality is and how to see it optimally. I'm also just naturally sceptical of experts.
Nevertheless, if nobody has used C18 with hexane, then why not try it, as you suggest? I agree. I accept this advice, pending selection of a competent laboratory. As previous stated, I have no lab.
Before hiring a lab, I still have questions concerning the specifications to the lab:
If hexane is too strong a solvent, then what if we mixed hexane with ethanol (though not in Germany, where it is taxed more) or methanol 50/50 ?
For less solvation, what if we lowered the flow or lowered the injection volume, or even used hexane:ethanol/methanol 10:90 ?
By the way, can someone please give me an expert opinion of the review of columns by Mac-Mod (linked to my previous posting and also available by searching the www.mac-mod.com website, and you better believe that I have nothing to do with Mac-Mod, so this most certainly is not a sales pitch for them nor their products), and one of the sponsors of this website (not some lipophilic antipolar website according to a poster) ? This review seems believable to me, but perhaps this is because I am naive and gullible, wet behind the ears, naked in the woods, so I ask you, the experts, about the selection of the columns. So I will take one or all of the three columns that would most match the analyte, according to this C18 column review, because no expert can tell me why not, specifically an Inertsil ODS-3, Kromasil C18, or Develosil ODS-MG column. What these columns appear to have in column, by the way, at least according to the websites of their suppliers, is a much greater internal surface area, particularly with smaller particle sizes, compared with other C18 columns, though the details ("carbon load", ...) were not clear to me. If you think that the C18 column review by Mac-Mod is nonsense, completely biased, unreliable,or incomplete, then please tell me. You are the experts.
I accept the advice to go back to the library and to read books about development of HPLC methods, but most of these books are not specific to lipids found in natural products nor to these specific three columns. Mostly, they are oriented to Rx products & methods. I did read the earlier website and other websites about lipids, but found no answers. Also, this topic is more about the modification and optimization of a method, than it is about the development of a method.
If you are as smart as you think you are, then you should have answers to the simple questions in this posting.
Sincere thanks for your time and attention.
Regards,
Ben
