Chromatography Forum

I have been working with a new Agilent 5975 MS since last March so am still learning the system. Recently I have been having trouble getting my system to hold a tune for more than a day or two. Also saw a marked jump in abundance on the 69 peak in the tune window when switching from filament #1 to filament #2. Based on this I'm pretty sure the filament is deteriorating but want to get some feedback on filament deterioration symptoms from operators who have years of experience working with these instruments. Thanks everyone.

It is possible. What I have seen in the past is that the filaments usually burn out before you notice a large drop in performance. I wouldn't use the Filament #2 position for any analysis. I've been told by Agilent reps that the performance of a filament in that position tends to be bad. It's there more as a sales gimmick than anything else. I would take out the source and swap the #1 and #2 filaments around and see if you get better performance.

Agilent said that the #2 filament tends to "sag" down away from the ion volume when it heats up reducing it's ionization effect. Not sure if it's true because I always use filament #1 to be safe. Anyway, these filaments should last you about 1-2 years running daily if you are not blasting them with solvents.

P.S. Nice screen name. If you're in a contract environmental lab it doesn't get much better.

Ty

Thanks. I switched over to filament #2 and things are running much better now, holding a tune as it should. Thank you for the information about filament #2 position and the tendency to sag. I'll swap it over as soon as time and sample flow allows. Regarding my screen name, it's even worse than a contract lab-state lab. However, it's good to still be employed. Thanks again for the valuable information.

Regarding your last post:

Another rule I try to always follow is "Don't fix it if it's not broken." What I mean here is that if it is working reliably for you in the filament #2 position then there is no need to switch it over to #1 later. I would only if it starts showing poor performance.

In my experience, a good trained GC/MS chemist (assuming you're in the US) should make $50k and above. Of course this is location dependent. I know of some local companies that start "Chemists" at around $35k but they aren't expected to run GC/MS much less do method development and data interpretation. This knowledge is what sets them apart.

Next time you open it up, make sure all the wires are tight. If they come off with a gentle pull using forceps they are too loose. You can carefuly tighten them with needle nose pliers.

be very careful if you are adjusting the pins as the above post mentions. I have fixed one where the connector fell off the cable before, but if you tighten it too much you might make it worse (which would require replacing the ceramic feed through board $$.)

Sounds like you fixed your problem, when is the last time you cleaned the source? Besides filament age a dirty source would be the first thing I'd expect to cause these types of problems.

Thanks everyone. Aldehyde, thanks for the tips on those pins. I just did a source clean a couple days before this problem started. Dirty source was the first thing I suspected. Since switching to the second filament the system has been holding a tune throughout each sample analysis. Abundance on the 69 peak is roughly double what it was with the other filament keeping all other parameters pretty much the same (repeller, horn, etc). The older filament hadn't burned out but was about 9 months old. From what I've been told this is short life for one of these but I guess stranger things have happened. Anyway, thanks for the help everyone.

Filaments can stretch and uncoil a bit over usage but usually when they go, it's more catastrophic. AKA no emission at all. When you have to clean the source again, see if filament 1 is deformed.

New filaments from Agilent should last at least six months if not a year... provided you have great vacuum and are not turning them on w/o solvent delay. Obviously, poor vacuum, hitting them with solvents or air will shorten their life. If you're using rebuilt filaments, it's more like playing the lottery. Sometimes you get 6 months or more out of them, sometimes you get 6 days.

You should be able to use filament 1 or 2 reliably. From my experience, it's not a gimmick.

Don't adjust the filament or heater pin collars unless you KNOW it's causing a problem. They will fit somewhat loosely. Very normal.

Thanks jvettleson. I run nothing but air samples on this system so that could likely account for the wear and tear. No highly concentrated solvents though. Thanks for your input on this also about filament 1 and 2.

It is possible. What I have seen in the past is that the filaments usually burn out before you notice a large drop in performance. I wouldn't use the Filament #2 position for any analysis. I've been told by Agilent reps that the performance of a filament in that position tends to be bad. It's there more as a sales gimmick than anything else. I would take out the source and swap the #1 and #2 filaments around and see if you get better performance.

Agilent said that the #2 filament tends to "sag" down away from the ion volume when it heats up reducing it's ionization effect. Not sure if it's true because I always use filament #1 to be safe. Anyway, these filaments should last you about 1-2 years running daily if you are not blasting them with solvents.

P.S. Nice screen name. If you're in a contract environmental lab it doesn't get much better.

Ty

Hi, I realize this is a 6 year old post but I just wanted to correct this for other people who stumble upon it.

The second filament is definitely no marketing gimmick -- it is actually critical to the function of the EI source. When you are using filament 1 the electrons emitted are reflected back by the 2nd filament. The electron can make several reflections back and forth in the ion volume before making a collision.

It is definitely true that if filament 1 has stopped working well that switching to filament 2 may not work. Sometimes if a filament stops working you can get away with running on the other filament until you have a chance to vent and change the filament, other times it won't work at all.

Filaments will sag and twist when they become very worn, and if they are operated with an air leak they will deteriorate rapidly.

There should be no functional difference between using filament 1 or 2, they are identical filaments and the design of the source is symmetrical.


As far as the original question, watch for filament shorting. If you do an extracted ion and notice "drop outs" in the continuity of the peak your filament is likely the problem. As the filament is worn the wire may sag and go off target, causing fewer electrons to enter the source.

You may notice during tunes that your EM voltage increases to compensate for the decrease in ionization. The repeller voltage may also increase in order to propel more tuning ions to the detector. This can also happen when the source gets dirty. If you clean your source and still have poor performance it may be time to change the filament.

Seems to me you are suggesting filament 2 is energized if its able to do this reflection. I don't recall seeing wear on filament 2 unless I am forced to use it by sudden loss of filament 1. I just lost my #1 in my 5973 a week ago #2 is definitely not as well behaved. But that may be because the source is a year dirty.

I see loss of intensity, fluctuations in signal and the need to quicktune and then I know I am about to lose the filament. As usual, I have samples to do and am limping a bit trying to get a good tune out of it. No trouble passing BFB but needs 100 higher EV and the 50/69 and 219/69 ratios are both rather flat at 0.8-1.2% and 50-55% respectively; which makes it harder to use the Atune followed by Ion Focus hat trick.

I sent my last used pair off to Scientific Instrument Services for repair and yttria coating to see if yttria gives any benefit. When I get them back, I will do a source cleaning and install them.

I will be interested to hear how the yttria works out, I have been thinking about getting that done also.

The "plate" or "target" on the opposing filament is used at opposite charge to the active filament to draw electrons through the source, not actually reflecting them. The source on the 5970/5995 had T shaped targets that were separate from the filaments to hold the opposite charge, then with the 5971 and 5972 they tried just using the opposing filament at the target, but that resulted in more wear on the unused filament and less draw on the electrons. The 5973 and onward they put the target plate on the filaments to hold the opposing charge improving the efficiency of the electron flow once again. If you look at the way the filaments are made that plate is attached to one leg of the filament holder, when the filament is inactive it holds an opposing charge but very minimal current while the active filament holds a current high enough to cause the filament to glow and emit electrons.

I have never had problems using either filament #1 or #2. I tune both and then use which ever gives the best abundance with lowest EMV when I do an initial tune after cleaning and replacing filaments. I then run that filament until it burns out then switch to the other and run until it blows out or I clean the source again. (Running volatiles I usually only need to clean about every 1.5 to 2 years if the filaments don't burnout first).

It is possible. What I have seen in the past is that the filaments usually burn out before you notice a large drop in performance. I wouldn't use the Filament #2 position for any analysis. I've been told by Agilent reps that the performance of a filament in that position tends to be bad. It's there more as a sales gimmick than anything else. I would take out the source and swap the #1 and #2 filaments around and see if you get better performance.

Agilent said that the #2 filament tends to "sag" down away from the ion volume when it heats up reducing it's ionization effect. Not sure if it's true because I always use filament #1 to be safe. Anyway, these filaments should last you about 1-2 years running daily if you are not blasting them with solvents.

P.S. Nice screen name. If you're in a contract environmental lab it doesn't get much better.

Ty

That bit about the filament #2 "sag" is very pertinent. I've installed my two SISalloy plus Yttria coating in my 5973 and the first calibration attempt was a disaster. It seems that since the new filiments are not as bulky as the old style filaments so I decided to position the filaments as far from the source body hole as possible. This increases the gap maybe 0.1-0.2 mm between the source body and the filament.

I use a 70 ppb ISS and 20,40,80,120,160,240,320,400,480 ppb standard curve. What happened is that response for the second half of the chromatogram (higher boiling point) compounds rolled off dramatically at about 160 ppb. I tried again the next day with the same result. So, being in a time bind for getting some samples done. I did the following.

I vented and replaced the SIS filament with my remaining original filament in the #1 position and left the other SIS filament in the #2 position. I made sure they were snugged in the opposite direction. So filaments as close to the source body hole as possible; and of course aligned parallel to the hole. I figured I would try to use the SIS filament in #2 first and if that failed, fall back on the old style unused filament in #1.

I went for vacuum and the next day put on a full calibration using the SIS Filament #2 and the Atune hat trick; I went for a 219/69 ratio of 55%. Ramping the repeller gave me a nice set of responses for 69, 219, 502 centered on 30 volts. Its never shown so "clean" before with the standard filaments. Maybe that was just luck with such a good vacuum after only 12 hours and having opened it three times after cleaning: water 0.90%, Nitrogen 1.18%, Oxygen 0.5%, Carbon Dioxide 0.36%. I purged a 240 ppb standard and saw that it had very similar response to my old calibration back in May 2017. I went ahead and put on a full calibration.

So, by 10 pm I had a very nice calibration. Most compounds had an RSD of 4-7%. My dibromofluoromethane, 1,2-dichloroethane, toluene-d8, and BFB were respectively 1.04%, 1.58%, 0.63%, and 0.85% RSD. I am using helium carrier gas. Compounds that have been non linear in the past or were affected (low response due to decomposition) by hydrogen carrier like carbon tetrachloride 2.01%RSD, dibromochloromethane 2.91%RSD, bromoform 4.55%RSD, and 1,2-dibromo-3-chloro propane 5.63%RDS were good from 20 all the way to 480 ppb.

I had a little higher RSD for acetone 12.3%, diethyl ether 10.4%, MEK 14.3%, tetrahydrofuran 14.6%, and MIBK 11.7%. But, I think that is more of a purge and trap issue. I'm purging at 70C but still using a water management coil rather than a bypass line on my Tekmar 3000.

One thing I have read on the SIS yttria filaments is that you need to lower the emission current a little because they produce more electrons at a given current. Not sure if that would cause the falloff with the first attempt or not.

One thing I have read on the SIS yttria filaments is that you need to lower the emission current a little because they produce more electrons at a given current. Not sure if that would cause the falloff with the first attempt or not.

I've not seen that. Their own SISweb Note 92: Yttria Coated Mass Spectrometer Filaments says to leave the Agilent default EIEnergy at 69.9 and that current and voltage will be correspondingly lower because it happens at about 500C lower temperatures while still producing 70eV. See figure #4.

I did have a source thermocouple fault on the second pump down (temperature was all over the place (target: 230C: 225,226,227,228,350, 450, 225, 228, 229, 280, etc...) I had the same fault during my May 2017 source cleaning and then it stabilized when I checked the mount. The instrument ran without problem right up till I burnt the filament. So I had bought a new thermocouple back in May and had it available and put it in right away when the fault happened again. I had wondered if temperature drift might be responsible but hard to see how it could vary enough without tripping a fault and I think I would have noticed changes while calibrating because I keep the source temperature visible on the Top App.