Greetings,
Does anyone have a reference that provides an accurate list of the m/z
values of BSA on electrospray? Thank you!
Return to TopI have had this problem and believed myself to have resolved it by changing the plumbing in (and leading up to) the instrument. Sources of contamination include; Vac Pump oil: Rough pumps frequently oil surfaces around them and this is usually the same place where the CI gas enters the instrument. And where unused regulators and connectors sit exposed to oil mists. Note that there is an environmental issue attendent in the discovery of this oil. "Bad" tanks of gas; we blamed isobutane once as it usually is supplied (or used) at lower purities than are recommended by instrument manufacturers for use in CI. Regulators: never blamed one yet Contaminated tubing: seen this one following switching an instrment from ESI to CI. Put new copper tubing on and it got better. I have thought that contamination tends to move further along (spreads) with time. This has led me to want to cap these gas inlets and outlets when not in use. Poppet Failure: The little solenoids or valves can some times bleed lubricant into the system and contaminate the gas lines. I'd try to determine the first moment that you noticed the contamination and then make a list of what changed. Then reconfigure it in the intial state (or the state in which it last worked) and try it. I have used a Finnigan XSQ intrument which allows one to directly connect the instruments rough pump draw to the CI line to flush it. Leaving the ion source hot, the manafold warm and letting the pump pull on the lines has seemed to clean things up on occaision. You might try using methane for trouble shooting as it is usually cleaner. Remember that it may be difficult to ascertain that you have fixed the problem as the contamination may remain after the "source" has been removed. This speaks to using long "wait" periods after a change to see if some improvement has been made, however slight. It may be a case of step-wise improvement towards your orignal "spec". Good luck these are frustrating at times. matt sweeneyReturn to Top
You can use the tfa (113 m/z) it is always there as background if you use it much. The Mehdi Moini paper on Ultramark as a positive and neg cal. solution is useful for over 500 m/z but below that you might try some small sulphate anions. Carboxylate will work but you have to pH adjust it with ammonia to insure ionization sometimes. If you need it you can sray solutions of NO3- or PO4- or SO4- obtained from the strong acids of these. Very, Very dilute solutions to these will spray fine especially if they are 1:1 meoh:h2o. I don't know if you really need much esi tuning down low anyway as most compounds analyzed are above that weight. Putting acids in to the source is not so nice either in my opinion. Low end tuning is pretty flat on all the instruments I've run. matt sweeneyReturn to Top
We are in the process of setting up a University based centre for ICP-MS analysis. The purpose of this centre is to provide research infrastructure support to a variety of research groups across four Universities. The research groups are in soil science, geology, mineral processing, water, etc, and involve staff, postdoctoral fellows, postgraduates and Honours level students. We intend if possible to buy one instrument to be dedicated to solution analysis, and another to be dedicated to the analysis of solid samples via laser ablation. It is intended to use the equipment to obtain results which extend from numerous low grade "routine" analysis to high accuracy research data acquired on a small number of samples. There are about four major players in the instrument manufacture arena. We would appreciate any comments you might have about the ability of existing equipment to meet the demands we have in mind. For example: * are the systems robust enough to be able to stand multiple usage from a range of users? * how long does it take to train a PhD student to operate the equipment adequately? * how friendly is the software? * how often is instrument tune-up required? * what can be expected in terms of instrument downtime? * how much technician time is required to keep the instruments operational and in good condition? Full time? Half time? We would be particularly pleased to receive advice from any persons who have had experience of operating this kind of facility in a University environment. Please contact Ian Sills i.sills@cc.curtin.edu.auReturn to Top
[This is forwarded from sci.chem.analytical - DB] Hello everybody! I am looking for any shareware or freeware software to interprete mass-spectra. If you know a address where I can get such software from please post it here or send me an email. Thanks Klaus +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ ++++++ Dipl.-Chem. Klaus Heitkamp Bergische Universitaet - Gesamthochschule Wuppertal Fb 9; Analytische Chemie Gauss-Strasse 20 42097 Wuppertal Germany heitkamp@mailgate.uni-wuppertal.de Tel.: 0202/439-3438 Fax.: 0202/439-2580Return to Top
Try Ivory soap (the liquid dishwashing detergent). The old, white, milky variety is a mixture of sulfate surfactants that give a nice negative-ion ESI mass spectrum. Avoid the new, clear, Ivory liquid. PEG sulfates also work well -- Mark Hemling first reported their use for negative-ion FAB, and he was kind enough to send me some to try for ESI. The only problem is that they are not commercially available, so we usually use Ivory soap instead. -- ========================================================================= |____________ |_ Robert B. Cody, Ph.D |________________________________ Applications Manager |__ Mass Spectrometry |________________________ JEOL USA, Inc. |_ |__________ http://www.jeol.com |_ e-mail: cody@jeol.com =========================================================================Return to Top