Increase safety when using Hydrogen

Neither of my 5890s have sensors. I've used hydrogen carrier on all of my capillary GCs for over 12 years without an incident. About a decade ago, Walt Jennings visited me, and as I was showing him our 0.1mm columns used for triglycerides and sterols, and the mass flow controllers we put upstream of our older GCs that just had pressure control. He said that the only hydrogen explosion that he had ever had, occurred when he forgot to block off a 1/4" packed column injection port fed just by a pressure regulator, and hydrogen was flooding into the GC :-). Virtually all modern GCs have sprung loaded doors, so that if an explosion does occur, the over doesn't disintegrate with debris hurtling around the laboratory. I would recommend using hydrogen all the time, unless you have a very good reason for not using it, it's faster, provides better resolution ( only nitrogen at 10 cm/sec beats it ), and is cheaper than helium. We use industrial grade hydrogen as carrier, passed through indicating drierite/molecular sieve traps, followed by an oxy-trap, followed by a indicating oxy-trap, followed by an activated carbon trap. Our three capillary GCs ( two with liquid autosamplers ) are in use nearly 24 hours/day seven days a week - only closing for Christmas/New Year break, at which time every year or so, we regenerate the driers and oxy-trap. Most of our columns last 4-10 years, the trick is never to allow a column or injector to be exposed to air at above-ambient temperatures, and to use a packed split liner to collect all the junk. We try for minimal sample preparation ( grinding up meat in chloroform and methanol, 0.45um filtering and injecting the solution for triglyceride and sterol analysis ), and the columns will last for years. Using industrial grade gases is also a lot cheaper and they tend to be fairly pure ( for detectors, the gases pass through drierite/molecular sieve and activated carbon traps only ). It's worthwhile having a purge valve on the high-pressure cylinder manifold to purge any air that gets into the hose when changing cylinders - and we keep all lines from cylinder to GC toggle valves pressurized at all times ( they all have pressure relief valves at around 400psi should the regulator leak through - bursting disks can also be used. The first thing I do to new GC is to mount Swagelok on/off toggle valves on the carrier gas lines as close as possible to the controllers ( we plumb both Helium and Hydrogen to GCs, as some standard methods still specify He, with a 1psi non-return valve on the He to ensure H2 never gets into the He line if somebody inadvertently opened both toggles at once ). I ensure all lines are 1/8" copper or SS, with 2-stage regulators with SS diaphragms, and no plastic anywhere. Using toggle valves means that changing septa etc. can be easily performed without affecting settings. I have no worries at all about hydrogen leaks, we have a Matheson ( actually from Gow-Mac ) leak detector that we use to check any new plumbing, and when people are learning how to change columns. I tend to operate at much higher linear velocities with hydrogen so we can perform rapid analyses, e.g. one GC analyzing free fatty acids currently has a 10 meter column where the solvent peak is coming out in 5 secs, and the total analysis time is 2.5 minutes. So, in summary, provided the GC is designed to cope with a hydrogen explosion ( spring-loaded door or vent ), hydrogen is an excellent carrier gas for both manual and automated unattended operation. There is no need for additional safety devices, but if you wish you can get sensors, and can install mass flow controllers upstream of the GC to limit the maximum flow to about 250 ml/min if using pressure-controlled carrier gases that doesn’t have a flow controller. SOURCE: http://yarchive.net/chem/gas_chromatography.html

Also, you could ensure all split vent ( and septum purge if paranoid ) lines are metal and lead to a location where they can be safety vented. I use a long 1/4" copper line from each instrument to outside the instrument room. Don't manifold the lines from different instruments. You can put a metal sinter on the outlet if the vent line does not go to a restricted ( no flames ) area. But if you use a sinter, ensure that it is cleaned regularly to prevent backpressure. I allow the septum purge lines ( 2.5 ml/min ) to vent into the laboratory, but if you have sensors, or a small room with poor circulation you should also vent them, and they can be connected to the 1/4" split vent line. I cut the split vent line on 5890s and put a 1/8" tee in it. I then put a toggle valve on the line going outside and a cap on the split vent outlet on the front of the instrument. This means that when I want to set split flows, I just uncap the front, add the soap bubble meter, and close the toggle. I suppose richer people could just buy a three-way valve to ensure people can't get the sequence wrong and completely block the split flow, over pressuring the injector if mass flow control is used. SOURCE: http://yarchive.net/chem/gas_chromatography.html