****************************************************************************** From: samm@user.rose.com (Samm Brockhurst) Date: Thu, 30 Oct 1997 19:56:07 GMT Subject: Ammonia -ve CI on a Trio 1s Organization: Rose Media Incorporated, Canada We have an application that we are trying to implement on a VG/Fisons/Thermo Trio 1s benchtop quadrupole. In order to match the sensitivity achieved by others running this method on an HP Engine and a sectored machine running in lo-res, we have had to go to pure ammonia as a reagent gas. The supplier we purchased the ammonia from recommends only a high pressure regulator because they seem to have nothing else with the desired chemical resistance (i.e. staninless steel). The Trio has only a needle valve for flow control and we have not been able to stabilize the flow enough to get consistent responses. We have used 5% ammonia in helium and this gives us reproducible results but insufficient sensitivity. I do not have the budget to try various custom concentrations of ammonia in helium and I suspect by the time we get up to a workable level of ammonia, the mixture will not be stable anyway. Can anyone suggest a technique or supplier that will provide us with the necessary low pressure flow control and chemical stability? Please do not reply to this email address. My normal server has refused to accept posts for a week and I am borrowing this access. If you do wish to email me please respond to: Patrick_Calway@inet.NOSPAM.hwc.ca (after removing the NOSPAM) Thanks Patrick Calway Health Protection Branch Scarborough Ont. ****************************************************************************** From: "Little, James L" Date: Sat, 1 Nov 1997 10:51:44 -0500 Subject: Ammonia Chemical Ionization Organization: * We have been doing ammonia CI for several years and our work is summarized in two different sections on my Web page listed below. Ammonia is rough on regulators. We mainly use a Matheson regulator which we can rebuild every one to two years. All these regulators are expensive. Be sure when rebuilding the regulator to remove the regulator from the tank and release the pressure on both sides of the diaphragm! James Little jllittle@eastman.com http://www.preferred.com/~s_little/mspec/index.html Eastman Chemical Company Kingsport, TN 37662 423-229-8685 ****************************************************************************** From: Cameron Dorey Date: Sun, 02 Nov 1997 16:21:14 -0600 Subject: Re: Ammonia -ve CI on a Trio 1s Organization: University of Arkansas at Little Rock I've been using a Matheson 3141 regulator (which is available in a 2-30 psig delivery version) for over 10 years now for ammonia, with no problems. You really might think about your needle valve as the possible (IMHO, probable) source of flow instability. If it has Viton o-rings (most seem to have these as default), they will degrade in ammonia. You would be better off replacing the o-rings with Buna-N or other ammonia-resistant ones. In my experience, any polymeric o-rings, however, will absorb ammonia and the flow through the needle valve will slow for about an hour after it has been opened, after which it is stable as a rock. If fast setup is needed, you might consider a toggle valve after the needle valve, so that the needle valve is always in an ammonia atmosphere and needs no presaturation time. (The two-valve technique has not been tested in my lab.) YMMV. Cameron Dorey camerond@mail.uca.edu ****************************************************************************** From: Gary Radford Date: Mon, 03 Nov 1997 20:18:07 -0500 Subject: Re: Ammonia -ve CI on a Trio 1s Organization: Radford Scientific -- Hi Pat, You should be able to get a metal diaphram flow controoller like the one HP uses in their 5989. Call me if you want one (416)822-4537 Gary Radford, Radford Scientific The opinions expressed here represent the company I work for. Cutting the salaries of the H? Board of Directors by 10% could result in the hiring of 80 new support techs.....that would increase customer satisfaction.( or maybe get the phone answered in under 7 minutes ) ****************************************************************************** From: Jack Martin Miller Date: Wed, 5 Nov 1997 13:37:28 -0500 Subject: Ammonia CI pressure regulation Organization: * If you are using a small ammonia cylinder - stick it in a thermostatically controlled bath and you will hold the vapour pressure constant and make it easy to regulate with a needle valve. Jack Martin Miller Professor of Chemistry Adjunct Professor of Computer Science Brock University, St. Catharines, Ontario, Canada, L2S 3A1. Phone (905) 688 5550, ext 3402 FAX (905) 682 9020 e-mail jmiller@sandcastle.cosc.brocku.ca http://chemiris.labs.brocku.ca/~chemweb/faculty/miller/