By Robert Herman on Wednesday, October 15, 2003 - 12:34 pm:
Has anyone observed the following problems when using the HP1100 autosampler (G1329 or G1313 ALS):
1. a vial is skipped during a sequence run (eg., septa not pierced), but autosampler continues without apparent error message.
2. syphoning of liquid/air between the needle seat and the waste line (port 4 of Rheodyne 7750 valve)during sample loading, causing air to be injected.
These issues were observed when using high-salt mobile phases (~0.2M Na2SO4), which leave salt deposits on the needle seat and drain tubing. We are injecting ~100 vials per run, 1 injection every 7 minutes, using 100 uL injection volume with 100 uL capillary loop in the metering pump. The autosampler is being controlled by Waters Millenium32 data system.
Agilent is investigating an alternative design of the "leak plane" which ensures that the waste line is positioned exactly at "needle seat height" to avoid syphoning. Any other suggestions to prevent syphoning or deal with missed injections would be very welcome.
Has anyone else observed similar issues ?
By Anonymous on Wednesday, October 15, 2003 - 01:31 pm:
When I've tried to do many 100uL injections overnight, the drain tube "well" overflowed and gave a leak error. We began just collecting it in a vial, but below the seat level. Is it really that important to maintain the correct height of drain tube?
By Tim on Thursday, October 16, 2003 - 06:50 am:
I've not heard of the issue with missed vials. Does this just affect one system (possible firmware corruption)/analyst(could they be programming the sequence wrong in Millennium). If it's more than one system/analyst, it could be the Millennium control of the 1100 not functioning correctly, in which case you will need to report it to Waters.
For the syphoning, we have had similar problems with some of our methods, especially higher injection volume ones. We get round this by placing the drain tube from the rheodyne directly into the main drain outlet on the ALS (rather than into the designated "holder", which seemed to be the main cause as it gets clogged with salts so increasing the syphoning effect) and connecting a wide bore tube (one of the corrugated ones that Agilent supply with the system) from this to the waste container (if you let high volumes of liquid run down the cascade route the 1100 is designed to use, it just accumulates in the column compartment and shuts the system down, especially with higher volume injections).
By Tom Mizukami on Thursday, October 16, 2003 - 12:47 pm:
Hi Robert,
Agilent has a new leak pan avaliable, at no cost to user that are having problems. I installed 10 of them last year.
The seat capillary is 2.3 uL in volume. Some other arrangements of the wase line from the injector valve can cause this seat capilary to drain. This will cause the injction of 2.3 uL of air. This can cause some problems at low wavelegth.