Linearity test: different inj volume [August 5, 2004]
Posted: Sun Aug 29, 2004 6:26 pm
By Leadna Brigola on Thursday, August 5, 2004 - 09:54 pm:
Under the validation guideline, linearity is conducted using solutions of different concentration range (50-150%). Is it acceptable if linearity is done using one solutions but different injection volume programmed at the HPLC autosamplers? What are the implications,if any? Will there be noncompliance to GLP, cGMP requirements? Please comment. Thank you
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By David Blais on Friday, August 6, 2004 - 04:24 am:
Unless your validation protocol states that the linearity will be conducting by preparing different *solutions* in the 50-150% range, then yes, I would say you could perform the linearity using different injection volumes. The on-column load is the same either way so there should not be any implications.
Regards,
David
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By Hugh on Friday, August 6, 2004 - 07:05 pm:
I guess the first question would be whether you have qualified your autosampler, and whether the qualification covers the injection volume range you plan to use.
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By JM on Saturday, August 7, 2004 - 01:03 am:
Use of different concentrations is always prefered over variable injection volume. Cos in the later case you have two variables to look at injector linearity and method linearity.
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By mike carolus on Saturday, August 7, 2004 - 03:04 am:
Hi
I agree with JM, there are two variables. When we validate the method we make up a stock linearity soln. and make dilutions for the linearity solns. (50 - 150%). We only use different inj's volume when we are doing method development(to check linearity).
Regards
MC
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By fred on Monday, August 9, 2004 - 11:13 am:
Often the error involved in preparing standard solutions manually is greater than "equipment" which can do it automatically. Also the time and effort involved. I know what method I would prefer. The auto samplers which can do variable volume injections are a great idea. Often using one position on an Autosampler for the range of standards. Like all these things you need to check the error variability with the manual and make sure it suits your method requirements.
Make sure you have it regularly checked and serviced ....
We use the Spark (from Holland) Autosampler and are very happy with it.
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By JA on Tuesday, August 10, 2004 - 04:17 pm:
Waters specify injection accuracy on their Alliance systems to within 1ul (2%) at 50ul.
Do many injector systems use a similar stepper-motor design and does it mean you've potentially got a 1ul error on any chosen injection volume?
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By Leadna N Brigola on Friday, August 13, 2004 - 12:32 am:
To David,Hugh,JM,Fred< JA,Mike
Thank you to all. Appreciate your responses. Actual target implementation for varied injection volume for the std calibration will be for routine analysis and stability testing. Linearity range using different conc solution was already eatablished during devlopment and validation. For the injector, calibration over the injection volume range used is being done to check accuracy and precision of delivery volume. We thought of this to reduce cost of reagents, manhours. We will automate aliquot withdrawal instead of the usual different conc solution where aliquot withdrawal is also done. We want to be assured that if use of variable injection volume is not violating regulatory requirements for phrama drug analysis. Thanks again and regards.
Leadna
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By HW Mueller on Wednesday, August 18, 2004 - 01:41 am:
You don´t have a solvent effect with various volume injections? (Are you using a standard solvent which has lower eluting power than the mobile phase?). Or is the range you use so small that a solvent effect wouldn´t show?
Also, no problems due to laminar flow in capillaries in those autosamplers?
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By Leadna on Thursday, August 26, 2004 - 11:30 pm:
Hello, HW Mueller!
The solvent peak is small(not quantified)but seemed to be unchanged. Plotting the responses the line is linear over the injection volume used. Can we say then that the variable injection volume method be used as the standard calibration line for the analysis?
Thanks
Leadna
Under the validation guideline, linearity is conducted using solutions of different concentration range (50-150%). Is it acceptable if linearity is done using one solutions but different injection volume programmed at the HPLC autosamplers? What are the implications,if any? Will there be noncompliance to GLP, cGMP requirements? Please comment. Thank you
-------------------------------------------------------------------------------------------------------
By David Blais on Friday, August 6, 2004 - 04:24 am:
Unless your validation protocol states that the linearity will be conducting by preparing different *solutions* in the 50-150% range, then yes, I would say you could perform the linearity using different injection volumes. The on-column load is the same either way so there should not be any implications.
Regards,
David
-------------------------------------------------------------------------------------------------------
By Hugh on Friday, August 6, 2004 - 07:05 pm:
I guess the first question would be whether you have qualified your autosampler, and whether the qualification covers the injection volume range you plan to use.
-------------------------------------------------------------------------------------------------------
By JM on Saturday, August 7, 2004 - 01:03 am:
Use of different concentrations is always prefered over variable injection volume. Cos in the later case you have two variables to look at injector linearity and method linearity.
-------------------------------------------------------------------------------------------------------
By mike carolus on Saturday, August 7, 2004 - 03:04 am:
Hi
I agree with JM, there are two variables. When we validate the method we make up a stock linearity soln. and make dilutions for the linearity solns. (50 - 150%). We only use different inj's volume when we are doing method development(to check linearity).
Regards
MC
-------------------------------------------------------------------------------------------------------
By fred on Monday, August 9, 2004 - 11:13 am:
Often the error involved in preparing standard solutions manually is greater than "equipment" which can do it automatically. Also the time and effort involved. I know what method I would prefer. The auto samplers which can do variable volume injections are a great idea. Often using one position on an Autosampler for the range of standards. Like all these things you need to check the error variability with the manual and make sure it suits your method requirements.
Make sure you have it regularly checked and serviced ....
We use the Spark (from Holland) Autosampler and are very happy with it.
-------------------------------------------------------------------------------------------------------
By JA on Tuesday, August 10, 2004 - 04:17 pm:
Waters specify injection accuracy on their Alliance systems to within 1ul (2%) at 50ul.
Do many injector systems use a similar stepper-motor design and does it mean you've potentially got a 1ul error on any chosen injection volume?
-------------------------------------------------------------------------------------------------------
By Leadna N Brigola on Friday, August 13, 2004 - 12:32 am:
To David,Hugh,JM,Fred< JA,Mike
Thank you to all. Appreciate your responses. Actual target implementation for varied injection volume for the std calibration will be for routine analysis and stability testing. Linearity range using different conc solution was already eatablished during devlopment and validation. For the injector, calibration over the injection volume range used is being done to check accuracy and precision of delivery volume. We thought of this to reduce cost of reagents, manhours. We will automate aliquot withdrawal instead of the usual different conc solution where aliquot withdrawal is also done. We want to be assured that if use of variable injection volume is not violating regulatory requirements for phrama drug analysis. Thanks again and regards.
Leadna
-------------------------------------------------------------------------------------------------------
By HW Mueller on Wednesday, August 18, 2004 - 01:41 am:
You don´t have a solvent effect with various volume injections? (Are you using a standard solvent which has lower eluting power than the mobile phase?). Or is the range you use so small that a solvent effect wouldn´t show?
Also, no problems due to laminar flow in capillaries in those autosamplers?
-------------------------------------------------------------------------------------------------------
By Leadna on Thursday, August 26, 2004 - 11:30 pm:
Hello, HW Mueller!
The solvent peak is small(not quantified)but seemed to be unchanged. Plotting the responses the line is linear over the injection volume used. Can we say then that the variable injection volume method be used as the standard calibration line for the analysis?
Thanks
Leadna