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By Anonymous on Wednesday, June 25, 2003 - 05:00 am:
Does anyone calibrated an autosampler in order for volumetric analysis to be carried out?
Does anyone know if it can be done?
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By Anonymous on Sunday, July 6, 2003 - 12:28 pm:
If you use a heated injector port, the syringe needle dwell time (fast or slow injections) and selecting differing temps will give varying amounts of sample into the port. Not sure what you mean by calibrating an autosampler for GC.
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By Anonymous on Friday, July 18, 2003 - 04:50 am:
Raising the head abouyt PhDs again, the reason I am asking is that we have one, a belligerent minded old so and so who insists the autoinjector is not injecting the correct sample volume repeatedly.
This does not help as he has already changed the syringe over three times for new ones, however he is now insisting on some sort of calibration on injection volume (which I think is a bit ridiculous) however he is superior to me and his opinion holds a lot of sway
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By Anonymous on Friday, July 18, 2003 - 10:05 am:
The amount any syringe will inject will vary, depending upon the solvent used, the temperature of the injector port, and the resident delay and syringe injection speed.
Injecting a volume of pentane solution will not duplicate an injection of chloroform if based on exact volume under the same conditions.
Commercial autosamplers will have a initial setup procedure where the area of a component of a test mix must duplicate ±1% by area. This is as accurate as most autosamplers will inject a sample solution and is used to demonstrate the equipment is working properly when initially setup after purchase.
Very early in GC method development the internal std was used to correct for this factor.
With a Chaney adapter an analyst should be able to duplicate this reproducibility.
At least I could 20 years ago and the two chemists who performed GC in our lab before me could do so as well.
If your syringe or septum is of poor quality/worn, or, if your resident time and/or injection port temperature is excessive, reproducible injections are only a dream.
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By Scott Fredrickson on Wednesday, November 26, 2003 - 01:08 pm:
Just for the record, I have seen 2 different Agilent ALS units fail to correctly control injection volumes--hardware failure is possible.
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By Gemma Ellison on Friday, January 9, 2004 - 02:28 am:
I am trying to devise a test mix for testing the precision of our autosamplers that will give RSD below 0.8 every time. Has anybody got any suggestioms?
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By Anonymous on Friday, January 9, 2004 - 03:53 am:
Most vendors will suggest a 1000-5000ppm C16, C14, and C12 alkanes in hexane solution or something to that effect.
But it is not the test mix that will cause your RSD to be above 0.8%.
It is the hardware installation or the inappropriate GC conditions that will cause the problem.
Good luck.
Does anyone calibrated an autosampler in order for volumetric analysis to be carried out?
Does anyone know if it can be done?
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By Anonymous on Sunday, July 6, 2003 - 12:28 pm:
If you use a heated injector port, the syringe needle dwell time (fast or slow injections) and selecting differing temps will give varying amounts of sample into the port. Not sure what you mean by calibrating an autosampler for GC.
-------------------------------------------------------------------------------------------------------
By Anonymous on Friday, July 18, 2003 - 04:50 am:
Raising the head abouyt PhDs again, the reason I am asking is that we have one, a belligerent minded old so and so who insists the autoinjector is not injecting the correct sample volume repeatedly.
This does not help as he has already changed the syringe over three times for new ones, however he is now insisting on some sort of calibration on injection volume (which I think is a bit ridiculous) however he is superior to me and his opinion holds a lot of sway
-------------------------------------------------------------------------------------------------------
By Anonymous on Friday, July 18, 2003 - 10:05 am:
The amount any syringe will inject will vary, depending upon the solvent used, the temperature of the injector port, and the resident delay and syringe injection speed.
Injecting a volume of pentane solution will not duplicate an injection of chloroform if based on exact volume under the same conditions.
Commercial autosamplers will have a initial setup procedure where the area of a component of a test mix must duplicate ±1% by area. This is as accurate as most autosamplers will inject a sample solution and is used to demonstrate the equipment is working properly when initially setup after purchase.
Very early in GC method development the internal std was used to correct for this factor.
With a Chaney adapter an analyst should be able to duplicate this reproducibility.
At least I could 20 years ago and the two chemists who performed GC in our lab before me could do so as well.
If your syringe or septum is of poor quality/worn, or, if your resident time and/or injection port temperature is excessive, reproducible injections are only a dream.
-------------------------------------------------------------------------------------------------------
By Scott Fredrickson on Wednesday, November 26, 2003 - 01:08 pm:
Just for the record, I have seen 2 different Agilent ALS units fail to correctly control injection volumes--hardware failure is possible.
-------------------------------------------------------------------------------------------------------
By Gemma Ellison on Friday, January 9, 2004 - 02:28 am:
I am trying to devise a test mix for testing the precision of our autosamplers that will give RSD below 0.8 every time. Has anybody got any suggestioms?
-------------------------------------------------------------------------------------------------------
By Anonymous on Friday, January 9, 2004 - 03:53 am:
Most vendors will suggest a 1000-5000ppm C16, C14, and C12 alkanes in hexane solution or something to that effect.
But it is not the test mix that will cause your RSD to be above 0.8%.
It is the hardware installation or the inappropriate GC conditions that will cause the problem.
Good luck.
