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Topic History of: LC Services Ltd - Welcome you to our forum Max. showing the last 6 posts - (Last post first)
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Dr. Chris Duffell
I am currently developing a new hydrogen generator for use as a carrier gas in GC's. Due to the nature of the system there is a pressure cycle as the cell tops up the delivery pressure for the required flowrate. I was wondering if any GC users could let me know what the maximum acceptable pressure variation would be per cycle, i.e. +/- 5psi??
Thanks,
Summer
I am using the LaChrom D-7000HPLC Machine System and I use the autosampler instead of the manual injection. Does the Autosampler have a separate column since I cannot figure out how is the autosampler connected to the Column Oven. Thanks for helping.
sheyna yang
May I ask what happened to my LC? No matter what I injected, and no matter what mobile phase I used on the RP HPLC (waters), I only got some peaks between 1 to 2 mins,and they might change height with concentration. No other peaks could be seen.
NIck Bayliss
Having once worked for Gelman Sciences( jost recently known as Pal Gelman) in filtration - and also Merck ( eurolab, VWR, or what ever they're deciding to call their chemical division nowadays.. )I fully agree with Harvey's last comment - \"never trust HPLC grade chemicals..\"
Gelman Science produced a clever product called the SOLVAC - don't know if it's still available-but it was made of Reusable, chemically resistant polypropylene. Resistant to common HPLC mobile phase solvents such as methanol, acetonitrile, and tetrahydrofuran.It's trick was to Draw directly from HPLC solvent bottle. Replacing traditional pour-and-wait filtration when filtering large volumes. Less likely to spill aggressive solvents than glass funnels or disposable cups and indeed less likely to break than glass funnels...
Filters were set within a simple magnetic seal enabling ANY-GH Polypro, PTFE, Nylon, and PVDF standard 47mm filter to be used..and replaced..
Offering a large effective filtration area-
it's claim was not only to degass but to filter - >
Harvey G.
am a user of columns. I agree completely with Gerhard. When I first started performing HPLC determinations, 30 years ago, I was included in a group of 4, none of us knowing anything about chromatography. We would regularly replace columns at a rate of 3 to 4 a week. Of that group, I am the only one still working with chromatography. Over the years I have learned that columns are not the source of problems. If you have proper methods using mobile phases that consider column chemistry, include proper sample preparation, provide instructions for column preparation prior to and after analysis as well as proper storage instructions between uses, a column's life span can be longer than a chromatographer's career. I have in use in my lab today 3 columns that are 10 years old. One has been used for 1 analysis jost of its lifetime. The other 2 have been used for various analytical tasks and are now each dedicated to 1 of 2 new methods developed in my lab in the last 3 weeks. I offer the following advice;
[1]Clean your columns immediately after AND IMMEDIATELY BEFORE using them.
[2]If you are not interested in seeing a sample component with your detector, do not inject it into your system, USE SAMPLE PREPARATION TECHNIQUES TO CLEAN UP YOUR SAMPLES.
[3]Using an ion pairing agent changes the stationary phase forever, so restrict use of any column that has been exposed to an ion pairing agent to methods that employ that particular ion pairing agent ONLY.
[4]Do not trust HPLC grade chemicals. Vacuum filter, degas all eluents prior to use even HPLC grade solvents, water, acetonitrile methanol, etc. and even if using remnants of previously prepared eluent. I was the only one that used a batch of contaminated Caledon HPLC acetonitrile without loosing any columns. The supplier replaced the bad solvent but did not replace anyone damaged columns.
Gerhard Kratz
Hi Nick, as a manufacturer of HPLC columns we get a lot complaints of users that the column is not performing well. After my work in analytical labs in the pharmaceutical industry, and now about 14 years in sales and marketing, I can say in jost cases the problem was not the column. But it is always very difficult to point out the source of the problem. Therefore such chromatography forums are a good opportunity for all users to share there problem with other users. It's always helpful to ask, before going mad in the lab, and loose a lot time and money. Therefore I hope and wish this new \"internet chat\" LC forum all the best, to be a useful tool for all colleagues working with chromatographic techniques. Good luck. Gerhard Kratz, HPLC Manager Europe, Tosoh Bioscience GmbH
