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Posted 7/3/2009 10:13:39 AM

In the lab I work. I do trace metal elements on urines. I use Perkin Elmer 6100 ICP-MS analyzer. I use Thorium as an internal standard for the heavy mass metals like lead.

I am encountering a problem of erratic ion counts on the heavy mass elements like lead or mercury.and thorium.

Anybody out there have encountered this problem before and found a solution for it. Thanks.




Posted 10/31/2009 12:05:50 AM
I know that this is an older post, but I am going to respond to it anyway just in case you are still having issues or just in the event that someone else may be interested in the issue and question that you have posed.

I worked in a clinical lab for several years and one of the assays that I ran on a daily basis was the heavy metal urine screen on a Perkin Elmer Elan 6000 (which is still about the same instrument with a slightly different look from the outside and possibly the addition of a DRC).

At any rate, I never had any issues with this panel, and it was actually one of the easier ones that I had.  First off I am curious as why you chose Th as your internal standard (other than its specific AMU)?  I would suggest switching your internal standard to Tb as it is is much easier to deal with (at least in my experience).

As for the erratic counts, that could be caused by a number of different things.  The first thing I always check is the sample introduction system (basically, unless you see the issue right away, just start at the begining).  If you have any leaks or blockages in your sample lines (I.e. Probe to peri-pump to sample neb tip to spray chamber to injector tube and ultimatley the sampler and skimmer cones), then it will cause the jumpy counts in which you describe.

If your sample introduction system checks out, then I would look to the vacuum system.  In many cases if there is a leak in the vacuum system (even a small one), then it can cause some significant issues with your counts.  Look again for leaks, except this time look for the leaks in the vacuum system (I.e. vacuum chamber, interface reigon, interface roughing pump (big pump on right), vacuum backing pump (small pump on right) and turbomolecular pump (behind the vacuum chamber).  Really examine the cones as well.  If the O-rings get too loose or worn, then they can cause for air to leak into the system and cause the vacuum pressure to bounce around, which then leads to erratic counts (make sure to keep an eye on that vacuum gague on your instrument panel and see if it is bouncing around or unusually eleveated).  Also check the orafices in those cones.  If they become too wide then you need to go ahead and replae them.  Also remember all of your little o-rings and ferrels that are thoughout the sytstem.  I have beat my head against a wall a few time in the past after replacing all of the large components and then finding out that the entire issue was a result of a teeny tiny ferrel being loose in a line somewhere.

What did your Daily Performance Report look like?  Specifically your Rhodium counts (in cps), your Ba ++ number, your Ce/Ceo Ratio, Background and especially those RSDs (minus the RSD for the background)?

If you see those RSDs jumping around and going a lot higher than 4 or so, then you have some instability somewhere in your system.  Also if your Rhodium counts are too low or too high, then this too can cause you some issues.

One thing to remember as well in regards to Hg analysis, is that Hg is really susceptible to memory interferences.  So I would suggest that you add some Au to your rinse water as well as your calibration standards, blanks and diluent.  It will not interfere with the other metals, but will help to reduce the memory intereferences for Hg.

I do not believe that you are having any issues with a matrix effect, since you are dealing with urine.  It is possible that you could use more diluent.  In my method I went with 500 ul of sample into 5 mL of diluent/sample matrix.  Of course you would need to make sure to adjust your calibration standards to match, unless you can still get your results within your calibration range without changing the calibration dilution factor.

Let me know if you still have issues and need any more assistance.

Posted 10/31/2009 7:10:42 PM
I really appreciate your response to this problem of mine. Everything on what you mention in your reply checks out. Let me be more specific in describing the problem, because the way I described it the first time is kind of in general, and not to the point. 

If is not really of a jumpy counts but it is more of a drifting counts, with maybe a slight reasonable and tolerable up or down fluctuation. 

Tolerable and reasonable "Some (not too often) time"

I did not really formulated the assay to start with. lets say I inherited it since I am assigned to run this assay and for the last two to three years now.  So the person or director of the lab decided to use Thorium as the internal standard for heavy mass elements. When they formulated the assay. Forgive my ignorance but what is Tb.

Now we are using Thorium for heavy mass and Ytrium for lighter mass for internal standard. 

Now, the problem specifically would be that the Thorium Counts will drift down to say about as low as 50,000 counts or maybe close to 50% between the readings of the first injection to the third injection, on a three consecutive injections. But it doesn't do it on Ytrium and lighter mass elements. Thorium for example can drift from 125,000 to as low as 80,000 to 65,000 counts. Whether you are using water or urine for a sample.

With all the physical conditions in the instrument that you mentioned checks out. If there is a problem. You would expect it, to also affect the lower masses. So why are the heavier mass are the ones behaving this way. Specially Thorium. Off course the heavy mass element consentration are calculated against the Internal standard. So my control results goes hay wire. Also what I have experienced is that on the same sample, if injected the second time or third, the Thorium counts would either go up or down. When its up my control result would be down sometime within range, and vice versa.

I have checked everything needed to be checked on the instrument that could possibly cause the problem. but to now avail. Even to the point of trying to reduce Thorium and Ytrium consentrations to lower counts, because I thought there might be some over saturation. But did not make any difference. I also rinse the instrument spray chamber every day with DI water to make sure it is clean to start with. And I have been doing this even before this phenomenon occurred.

I am using a ratio of 700 uL of sample to 6 ml of DI diluent.

Now I use to use 5% Nitric Acid for rinse. Now I am using just plane Metal ion free water. You think that can cause it?. Although I have used water for a while already before this phenomenon, started to show.

I have also have the Perkin Elmer Service engineers check it out and they can not find any problem. That may cause it. To the extent for them to run stability runs. and came up with no solution to the problem.

The stabiliity runs they say were Okay. And also the lab director that supposed to have helped do R&D in formulating this assay have not come up with a specific cause to the problem. Maybe it is just the instrument is OLD.

Again thanks for your reply. If you think this is something you can research on. When you have time. I will appreciate it very much. When you let me know.

By the way I have presented this problem with the Perkin Elmer "Specialist" and Research people and the diagnosis that they come up with, for me to check I already did.

So I am at a lose. So my solution is to reinject or realiqoute my controls to get a control result with in range. You think that is "Okay" QC when nobody have any solution to the problem.

I don't feel comfortable with it. But nothing I can do since even the manufacturer of these instruments that supposedly have done research and development on it before putting it to market can not come up with a solution.  Well good luck to me.

Posted 10/31/2009 9:38:35 PM
I do not know reigon you are in, so I do not know who your PE service engineer is, but it sounds odd to me that they are not able to figure it out.  The main engineers I work with are in the North Carolina Area, and have always been able to correct any issues with my 6000s, 9000s and DRCe units.  Where are you located?

Now, back to the issue at hand.  Tb is just the symbol for Terbium (159).  It is a much better internal standard for your heavier masses than Th.  It is extremley simple to change it over.  Just purchase some Tb CRM from CertiPrep, Fisher, VHG, VWR or whoever you use in the same concentration as you do the Th, and then switch.  In the Elan software, just pull up your method and then go into the calibration tab and go to the row where you have Th enetered in.  Delete the Th and type in Tb.  The go up to options at the top of the screen and then click on "set as internal standard" when the drop down box appears.  Once you have done that, then save the method and it is done.  Then you just need to make sure to make up new calibration standards subing in the Tb for the Th at the same levels and then in every other solution and sample prep methods where you added Th, just sub in Tb and that will be the end of it..internal standard is now changed.  I believe that you will see less stability issues with Tb just dew to its mass.

Now moving onto the instrument.  There are two things that I think of off hand when you tell me that all of your troubleshooting of the hardware has checked out.  One of those things is your detector and/or mass calibration.  The 6100 has a dual detector electron multiplier (and most likely you are using it in the dual detection mode-both analog and pulse).  So it is possible that your detector may be on its way out.  It is a consumable, and after time (especially if you use your internal standard at a high concentration, or are scanning for a great deal of isotopes) these detectors will become spent.  In some cases it will cause certain groups of isotopes (by AMU) to reflect issues before other groups.  This also holds true for your mass calibration.  It is possible that your mass calibration is falling off on the heavy side, and that would be the reason why your lighter weight isotopes are not giving you any issues, whereas your heavier ones are causing you issues.

The second thing, and this is something that a PE service engineer would not be able to detect, as they do not stay in your lab all day long every day of the week like you do, is your ambient temperature.  ICP-MS instruments are VERY sensitive to the surrounding temperature.  If you have fluctuations in the room temp within your laboratory (going from hot to cold to hot to cold again) then this will definatley show up in your counts on your internal standards.  I actually have a stabelizer on my thermostat so that if the air conditioning system indicates a temperature below or above my mean range it gives me an alarm, because before I had the AC guys in to work on this, the temp in my lab was going back and forth constantly causing my internal standards and counts to fluctuate all of the time, to the point where I was having to run blanks all of the time throughout the run, so that I could use them to reprocess with, and even then in some cases the drifting was too severe to even reprocess.  Unless you have already done this, grab a thermometer (if you have a datalogger one then use it) and sit it within the vacinity of your Elan (not on it, just somewhere near it) and keep a record of the temperature throughout the day.  Try to take it every 30 minutes if you can and write it down and do it for a week.  If you have a datalogger then you will get even more data on temp as they take the temp every few seconds or so and automatically store it.  Then if you notice fluctuations you can go back through your data and compare it to the temperature info you logged and see if you notice a correlation between temperature shifts and internal standard shifts.

You say that your internal standard % recovery is all over the place, going from arounf 60% all the way up to 150%.  Do you have the QC checking enabled on your method?  If you do not, then I strongly suggest doing this.  I can very easily walk you through how to do this one day via phone while I am sitting in front of my Elan.  In fact next week I plan on putting a new Lithium method online, so I will actually be going through the process already.  Depending on your time zone I can try to schedule my method set up to help you out.  If not then I can try to send you some very basic step by step instructions on how to do it.  By enabling this mode (at least for you internal standard), it could at least help you feel more comforatable with your results).  You would want to set it to the low end recovery at 70% and the high end at about 130%, and if your counts for Tb (or Th if you choose to stck with that Itsd) drop below or above it will flag the sample on the data summary report, letting you know that the internal standard has fallen outside of the set QC limits.  Then you can at least know to go back and repeat the sample and make sure that you have not gotten an erroneous result.  I use QC checking for all of my methods.  It just makes it so much easier when you are reviewing and interpreting your data.

Oh and always use HNO3 in your rinse water.  I go with 5% always!!!  I never use only ASTM Type 1 DI water alone.  About 5 years ago Perkin Elmer made it pretty clear with the research that some of their application chemists had done, that the addition of the HNO3 was the only way to go, as it adds with stabilization and keeping your system clean.  Also make sure you are using Ultra-Trace Metal Grade HNO3, not just the standard trace metal free, as there is a huge difference.  I only use EMD Omnitrace Ultra, and will use EMD Omnitrace Standard for cleaning and acid washing some of my labware (since it it much cheaper than the Ultra which comes in the plastic pre-leached FEP bottles).

You can email me at if you need some more help and if you would like for me to try to walk you through the QC checking function (if you do not already have that enabled).


Posted 1/20/2010 8:31:04 AM
Is it possible it could be sample tubing?  ToxLabRat is right in that the problem may originate from the sample introduction system.  I'm currently wrestling with drift problems myself and I've basically changed everything in the instrument to no avail.  The only thing I can think of is the tubing I used that comes off my autosampler probe to my peristaltic pump tubing is the wrong size.  The IS recoveries start off ok but then drop off drastically.  I too am using the ELAN 9000 instrument (no DRC) and I use methods 6020 and EPA 200.8.  I think ToxLabRat is right in suggesting Terbium as a replacement for Thorium.  Don't be afraid to try new things.  Unless your method specifically states that "thou shalt only use Thorium" then try Terbium and your results may come out better.  I buy the 100 ug/ml internal standard pre-made from Perkin Elmer and haven't had any problems with it.  The problem I'm currently having is definitely instrument related.

I hope this helps!


Posted 1/20/2010 6:30:36 PM

I see that you are experiencing Itsd drift as of late.  Are you seeing all  of your internal standards drift or is it just a select few of them?  Also when you start seeing the drift is it always a downward drift where the cps for the internal standard starts of higher and then just gets lower and lower the longer your instrument runs?  Or is the drifiting up and down or sporadic?

If you have changed everything in your sample intro system (this includes AS and all of its components and peri-pump and its components) and you are still having the issue then i strongly suggest monitoring your ambient temperature.  It is extremley common to get drifiting issues with temperature fluctuations in your laboratory environment.  In fact we had to install several ductless AC units in one laboratory where I worked just for this reason.  When I first arrived at my current laboratory the ambient temperature of that place was all over the grid and no surprise to me, I saw how sporadic the counts were.  As soon as I got the temperature stabelized that issue went away.

Depending on the type of drifting you have and what isotopes you are seeing it with, it could be some type of interference as well.  I know that Na and Cl will really screw with Sc and a few other common Itsd's.  The more of those interfering isotopes that build up, the lower and lower the % recovery becomes.  If you do not monitor for interfering isotopes currently, then I would just go into your method and add in Na, Cl, Kr and C.  Then you can see what is going on with your samples (especially since you are running wastewater and sludges).  You may notice that it is a result of some really dirty samples and in that case you could increase your rinse time or you could look at using a different prep method to get the interfering isotope out (I.e. reductive precipitation).

Other than the sample intro system (and aside from your peri-pump tubing you should also check all of the little ferrels and o-rings as well) I would look to your cones to see if the orafaces have become too wide and are causing your vacuum pressure to fluctuate. 

Let me know if I can be of any help to you.  Good luck with figuring it out.


Posted 1/22/2010 7:21:41 AM
Thanks for the help Tox.  It was all of the internal standards that I was having problems with and the counts would start off good and then they would all drift downwards as the run continued.  The temperature is pretty stable in the instrument room.

The tech from Perkin Elmer came in the last two days and was able to solve the problem.  He ended up changing out the lens and the cones and somehow that solved the problem.  I'm still not totally convinced since I only had one successful run.  I'll try running it again today and see what happens.  Li drifted down to around 64% recovery on some of the more yucky samples but at the end of the run I got around 75% with my reagent blank.  It still drifted down but not as bad.  I'm going to do my mass cal and dual detector today and see how it goes.

Other possiblities the tech came up with was the mass flow controller and the PA Tube (which controls power), but hopefully it doesn't come to that!  Thanks again.


Posted 1/22/2010 11:10:32 AM

Just curious but what reigon of the US are you in?  I am wondering who your PE Service Engineers are.  How old is your instrument?  It seems a little odd that you mass flow controller would already be causing you issues-unless the instrument has been subjected to some major flux.  Also not sure about that PA tube either.  The reason I say that is because if it were these things it seems as though you would see a consistant drift over time, so each day that passes the counts would get lower and lower and lower.  Whereas it sounds like you are saying that they are pretty good at the start of the day but then drift lower the longer the instrument runs.  Then you shut it down and bring it back up the next day and they start out at good counts again. 

Did your engineer put in new cones and a new lens or did he/she just clean and replace them?  If they just cleaned and replaced I would go ahead and order a new set of cones and a new lens if you do not already have those parts in stock at your lab and I would start out with just changing the cones and then if the problem still exists I would change the lens as well.  If he/she did put in new cones and a new lens then do you know if they put in new O-Rings with that sampler and skimmer cone?  If not I would slap new O-rings on there.  I would also monitor my vacuum pressure (plasma-on) and make sure it is not bouncing...or at least reference the RSDs on all of your Daily Performance reports and make sure they are all around 1 and not bouncing around or really high (less Bakgrd 220).

I know that in the clinical world I am really hard on my cones and have to replace them with new ones about every 4 weeks because the orafices get too wide.  However in the environmental world I do not have that problem and can use the same set of cones for months on end without ever changing them.  All I have to do is clean them and put them back in, as the wastewater, drinking water and sludge samples are just not as hard on the cones and therefore do not cause the orafices to widen like those blood, serum, plasma and urine samples do.  But, I guess it is possible that your samples, even though they are environmental, are comming from places where there is a different composition than what I usually deal with and therefore those isotopic differences are causing your cones to wear down more quickly. 

It almost sounds more like a dissipation issue.  Similar to what happens to Au when you try to analyze it.  If you do not do it quickly enough then it will begin to reduce before it even hits the tips.  Have you changed out your reference standard to make sure that it is not your CRM that has become unstable?  Sometimes those CRMs can start to floc or ppt out even though they are still in date.  In fact that is the reason that I will not order any CRMs from Ricca, because the standards I have purchased from them never last more than about 5 months before they start to floc out. 

Good luck...

Posted 1/25/2010 10:22:05 AM

I had no idea that people had problems with Ricca standards.  We've been getting them for years (AA standards and ICP-MS standards) and never have we had a problem with them Floc-ing out...I know ours are preserved with acid (which can prevent floc-ing), which ones are you using?  My CRMs are pretty good.  We order from two companies (Fisher and Ricca and haven't any problems with either).  Sometimes we get JT Baker and ERA.  Never had we had a problem with any of them...what concentrations are you using?  Ours are 1000 ppm standards preserved in acid (most are 3% nitric acid except Sb, which is in trace tartaric acid).  We buy seperate standards from Ricca for QA purposes and we get a mixed standard (100 ppm) from Perkin Elmer for our calibration standards.

I think the problem with drift has been solved.  I'm in the Northeastern region of the U.S. (Central NJ).  I'd give you the name of my service engineer(s) but I don't want to give their full names in an open forum like this, but we get the guys from Perkin Elmer itself to work on the ICP-MS and Thermo Elemental to work on our AA).  But we have 2 of them and I've only dealt with 1 so far.  Our instrument is only 2 years old (we started using it in January of 2008.  The engineer came in and did some daily performance checks as well as clean out the sample intro system.  He looked at the cones and lens on the first day and decided not to change those out since the cones looked good and so did the lens.  Everything was passing, which befuddled the engineer and myself.  But when we would do a run things would drift downward.  The next day he replaced the cones with new ones as well as new O-rings.  The O-rings I had on before he came were brand new ones that I put on the day before he arrived to look at the problem.  He also put in a brand new lens.  That seemed to clear up the issue and my internal standard stayed consistant throughout the run.  At the end, when I ran my reagent blank, all of my IS's were in the 90s for % recovery.


Posted 1/25/2010 10:45:49 AM
I know of your service engineers as I have met a few of them at conferences but have never really worked with them before.  One of them did just transfer down to my reigon but he is more into AA than ICP.  Anyway it sounds like your problem was in fact the lens, since after putting in a new one your drifting has subsided (at least within a normal SD).  You may have had a bad lens, or maybe your lens was just old.  Some people will clean them over and over again and then you end up a few years down the road with a lens that is just worn out.  It is hard to look at them with the naked eye and tell if they need to be retired, but in my experience when they start to get close to that point, what will happen is I will clean them and put them back in and when I optimize the lens voltage it will set much higher than I would expect a new or cleaned used lens in good condition to set (>7 Volts).  Once that happens I just get rid of them.

As for the CRMs, it is possible that I got my hands on a few bad lots from Ricca (who knows).  In the clinical world no one has ever heard of Ricca and the main manufacturers we work with are VHG Labs, Perkin Elmer, Fisher and CertiPrep.  When I started doing some environmental work I ordered in some single element reference standards for B, Sr and Li from Ricca because they had the best cost and all three of them were preserved in acid (each had a slightly different proprietary blend of a combination of typical stabelizing acids (HNO3, C4H6O6 and HCL).  At first I did not notice the floc or ppt because it was so fine and all I noticed was that my calibrations for these isotopes kept failing and in ways that did not point to an instrument or sampling issue. That is when I took them and poured an aliquot into a clear optical vial and held it up to a stability light with magnifier and then I could see all of that ppt and particulate matter suspended within the standard.  So, since then I have stuck with CertiPrep, Fisher, Ultra and am now getting some stuff from SCP Science (which by the way that have the best prices I have ever seen on trace and ultra trace metal grade acids, and their nickel cones and their glassware for the Elans is the cheapest as well and of good quality).  For most of my analytes I do not use as potent of a CRM as you do, just because it generates too much wasted standard.  Instead I have CertiPrep make me a custom standard at 20 mg/L for every isotope less the odd balls (Sr, In, Ga, Li and B) and then I work off of that.  At the end when the CRM is expired I have used almost the entire bottle, whereas with my odd ball isotopes which I do get in the higher concentrations just bc I buy them off the shelf, I have almost an entire bottle left when the expiration date comes up.  We use ERA and NSI but only for our PT/water study samples.  I am not aware of anyone in our lab that uses them for working standards, but we have always been very pleased with their PT samples.

Anyway, I am glad that you were able to get your instrument back up and running properly.  Two years is a newborn when it comes to ICP-MS instruments.  Mine is over 10 years old!!!

Posted 1/25/2010 10:53:21 AM
Thanks!  Our AA is about 7 years old.  Since we switched to ICP-MS it hasn't gotten much use (except for Ca, Mg, Fe, Zn, K, and Na.  Since 200.8 and 6020 say you can't run those, we don't. 

I'm pretty much a newborn when it comes to ICP-MS, but I'm catching on quick.

Posted 1/25/2010 5:35:04 PM
Just as an FYI, you can use ICP-MS for all of those isotopes that you listed and still be in compliance with EPA Method 200.8 and Standard Method 6020 (Just go to the EPA website and you can pull up the most recent SOP versions and analyte lists).  A few years ago those analytes were added to the SOPs as acceptable for analysis via ICP-MS.  The only exception lies with the analysis of drinking water samples for alkali metals less K (Na, Mg and Ca), as this still has to be done on the flame.  However K in drinking water can be done on ICP-MS and all of the alkalis can be done on ICP-MS for wastewater, solid and sludge samples.  Unless your state's division of water quality have instated some regulations which are specific to it, then you can transition these analytes to your ICP-MS and I would strongly recommend it.

I have my alkali metals on a method by themselves and look at Ca, K, Na and Mg and use a curve of 100 ug/L, 1000 ug/L, 5000 ug/L and 10000 ug/L with a QC check around 5000 ug/L.  It never gives me any trouble and is a very easy method to put online.  The benefit of course is that you can scan for all four isotopes at once whereas with the FAA you have to do one at a time.  This will save you time and overhead. 

As for Zn and Fe, I have those isotopes included in my standard metal method (which is pretty much everything minus the alkali metals and the odd balls that I have to use different Itsd for).  Zn is quite simple and should not give you too many issues.  The main thing (which is true regardless of method) is to watch what you use to prep and store your standards and samples and also to watch the lotions, skin products, hair products and colognes that you may use since Zn can leach out of almost everything.  The Fe will probably give you the most issues, but even still with an ICP-MS as new as yours is, I would not expect there to be any rust build up on your instrument.  Just make sure that you take Fe 57 and monitor for interferences and you should be fine.  I use the same line for Zn and Fe as I do for all of the rest of the isotopes in that method which is: 0.5 ug/L, 10 ug/L, 50 ug/L and 100 ug/L.  Iron tends to run high in wastewater samples so you would probably want to roll with a 1:10 sample to diluent to begin with and then go from there.  Zn can go either way, just depends on where the sample comes from.

I am glad that you are enjoying the instrument.  It does take a long time to really master and even when you think that you have seen it all, something happens that you have never seen before.  I have been working with ICP-MS for about 10 years now and still I get stumped every now and again with an issue that I have never seen and the same holds true for my PE service engineer who has been working with them since they first hit the commercial market back in the 80s.  In fact just last year he had to replace an quadrapole in an Elan 6000 and in all of the years he has been servicing them that was the first time he had ever seen that component need replacing.  Stick with it and you will find it will benefit you a lot, as most people get frustrated with ICP-MS because they are so fussy and require a lot of maintenance and TLC and so they throw in the towel and go back to GC or HPLC or AA-something a little more rustic and less needy.  It is because of that and steadily increasing regulations by EPA and FDA that ICP-MS specialists can be difficult to find, and so if you are one of them then you can pretty much have a lot of room to negotiate with a potential employer!

I hope that you continue to enjoy the instrument and if there is anything you need some help with, be it method development, troubleshooting, etc. then do not hesitate to hit me up.  It is always helpful to have other view points on an issue, especially if you have been staring at it for days on end!


Posted 1/26/2010 7:18:32 AM
Thanks for the input and help, Tox.  I'm pretty sure the NJDEP doesn't allow us to run Fe, Ca, Mg, Na, and K on the ICP-MS.  Last time I checked they didn't allow it, but I'll have to look into it again.  Our concentrations for those are very high (Ca in our influent runs around 60 ppm) and our school of thought tells us that if it's that high then there isn't any reason to run it ICP-MS.  In my mind, I'd love to since it would save me some time if I could run them all at the same time.

Thanks again, and if I have any problems I'll go to you, and if you have any questions, feel free to ask me.


Posted 2/7/2010 2:53:32 AM

Sorry for my English, but please go to the PerkinElmer website and you can find all field application notes on the analysis of Fe, Ca, Mg, Na and K. There is a very good one for drinking and waste waters. Even at high concentrations. If you have a DRC-type instrument you can adjust the RPa value (not RPq) to increase your dynamic range. If you do not have a DRC type you can easily adjust the resolution for these analytes. Please refer to your software manual how to do. It works great!


Posted 2/9/2010 9:08:54 AM
Your English is great!  Thanks for the suggestions, I'll be sure to check it out.


Posted 8/5/2010 8:02:38 AM
 I work with an Elan 6100 (simple, not DRC) four years now. I usually analyze water samples. I was using In as an internal std and some months before I have tried to use Rh. I have a serious problem with drifting of counts of the internal std and I wonder why since the conductivity of the samples does not exceed 200-400 μS/cm. Does anybody  could really help me with this problem?Thank you in advance!

Posted 8/5/2010 8:06:57 AM

I had a similar problem several months ago with drift.  All of my internal standards were drifting.  Changing cones and tubing did nothing, as well as changing pump oil.  What I did was change the lens and that seemed to correct the problem.  Try that, and see if that helps.  I hope it works for you!


Posted 8/5/2010 8:15:01 AM

firstly I would like to thank you for your fast response! I have changed the lens and altough that the lens optimization is very good I still have the same problem. Is there a possibility that Rh is not to stable for these applications?


Posted 8/5/2010 8:36:47 AM

No problem, you caught me at the right time!  It sounds a lot like the problem I had, changing the lens helped.  I have an Elan 9000, maybe that solves it on that instrument.  You can also see if your sample introduction system needs to be cleaned.  Sometimes clogged nebulizers can cause drift issues. 

First I would try just running deionized water through the instrument and see if it is your samples causing the drift, you may have to dilute the samples in order to get your IS's into an acceptable range.  

If worse comes to worse call in service and see if there is a more technical issue with the instrument.  How old is your detector?  I'm not really sure if detectors can cause drift problems but it may need to be replaced.

Hope this advice helps, keep me posted!


Posted 8/5/2010 8:50:55 AM

I have more or less the same problem with the three nebulizers that we have. Not only the meinhard nebulizer but also the crossflow and the ultrasonic one have the same problem. I have also replaced the torch and the cones but nothing seems to help. The technician also cannot find a solution to this problem. 

The instrument is ten years old but in a pretty good condition. We do not use it in an everyday basis and only for research. The problem started after the replacement of the controller and the detector! I do not know if this happed because the new detector was purchased directly from the ETP company. Do you believe that this could be the problem?

Posted 8/5/2010 9:50:07 AM

That could be the problem.  If you still have the old detector, try putting that back into the instrument and see if the problem comes back.  If not...try to find someone in your area that has an ICPMS and see if they can run your samples and replicate the problem.


Posted 8/5/2010 10:50:39 AM

thank you very much for your suggestions and your time. I will replace the detector with the old one and I hope it will help. 

Best regards,


Posted 8/5/2010 11:20:39 AM

No problem, that's what we are all here for!  Good luck and keep us posted!

Posted 8/5/2010 1:47:14 PM
How is your daily performance? Are all values meeting the specifications?

What are your settings for both the pulse and analog voltage detector?

Do you use the standards from perkin Elmer or do you use a different source?

Posted 8/5/2010 2:02:02 PM
Good evening,

the daily performance is very good, at least it reaches all the criteria. These values are with meinhard nebulizer but with the crossflow nebulizer the values are also very good.

Anal.         Net Int. Mean

Mg:           138673

Rh:           802067

In:             981279

Pb:           488273

U:           1078859

Ba/Ba++: 0.014

Ce/CeO: 0.029

Bkgd: 5.7

RSD: 0.9 - 2,1

neb. gas flow: 0,84

lens: 7

RF Power 1150

Anal Stage -1800

Pulse 1100

We use std2,std3 and std5 of perkin elmer and rhodium internal standard from fluka.


Posted 8/5/2010 6:51:01 PM

One thing that can cause drift in your counts is drastic changes in the ambient temperature within the laboratory space that the instrument exists in.  If over the course of the day, the ambient temperature drastically increases or decreases from what it was at the start of the analysis, then it can cause drifting of internal standard counts, thus throwing the % recovery out of control low or out of control high.  So that is something very simple that you can check out.  Make notes of the temperature within your lab space throughout the day and see if you are getting any major fluctuations and if so, see if those fluctuations correspond with your internal standard counts shifting.

I have never had any issues with Rh not being stable, and in fact the stability on Rh is usually pretty good.  I have never had any issues with In falling out of solution within a certified reference material either.  The only internal standard I have ever seen floc out is Ge, but even with that one I have only seen it happen once, and it was due to a manufacturing issue that was later discovered by the vendor.  You could try switching back to In and see if you are still experiencing drift issues.  If you are, then most likely it has nothing to do with your interlan standard selection or material.  However if once you change back to In the issue resolves, then it may be a bad lot of Rh standard that you have.

How is your vacuum pressure?  Looking back at your instrument log do you notice a drastic change in vacuum pressure that corresponds to the onset of your issues?  If your vacuum pressure gets jumpy and is not staying stable then that will cause your counts to shift all over the place. 

Since the problem seems to correlate with the replacement of the ICP Controller and the detector, I would say that those are the first places to dig into if you have ruled out all of the simple things.  I use ETP detectors and I have purchased them directly from the manufacturer as well as through other vendors, and I have never recieved a bad one, but that does not mean that it is not possible.  I would check to make sure that it was installed properly.  Also make sure that the instrument was fully tuned after replacement of the detector, because you should always go through the complete tunning process after putting in a new detector.

One thing that I have found in my experience, especially with environmental samples such as water and wastewater, is that if I have the instrument too sensitive then it will cause all kinds of problems.  With Rh counts as high as you have, I might try backing down the gas flow to bring the sensitivity down and then see if that helps.  Backing the gas down is something simple that you can try and the worst that can happen is that it will have no effect and in that case you can just put it back to the flow rate that you had it at before.

Good luck.


Posted 8/6/2010 3:23:01 AM

thank you very much for your reply. I also believe that it could be the solution. Perhaps it is not too pure and it causes problems. Do you have any suggestions for Rh internal std solutions from other companies. Which one do you use?

The technician checked the pumps and measured the vacuum and he saidit is pretty stable for both.  The temperature of the room is quite stable, at least more stable than in past but I will check it once more. I will also switch back again to In and I will see if the problem still exists.

All the calibrations and the optimizations were done after the detector replacement and everything seems to work really good. I am really happy to hear that sb else has also made the same purchase, so I am quiote sure it was not a bad choice!

I hope it will work and be sure that I will keep you informed.



Posted 8/6/2010 10:43:13 AM
I'm sure you can purchase standards from Perkin Elmer in your region, so I would go with them.  I've been getting standards from them since we started running ICP-MS in our lab and I have never had a problem with them.  You can also try a company called SPEX, located in New Jersey (United States).  I'm sure they can ship to you in Greece.

ToxLabRat makes a great point about sensitivity and temperature fluctuations because I've noticed some drift in my lab in the past due to temperature.  It was only slight drift and everything was within the control limits but temperature does play a role in recoveries.  And like Tox said, backing down on your neb flow will cause your counts to decrease as well as decreasing sensitivity a bit, but that might solve the problem.

Best of luck!


Posted 8/6/2010 11:45:44 AM

as I wrote yesterday we are using perkin elmer stds (std2, std3 and std5). From each main solution we dilute (water and istd) up to different concentrations (10 ppt, 100 ppt, 1 ppb, 10 ppb, 100 ppb, 1000 ppb). In case of std3 we could not use In as internal std because it is included in the solution. Perkin elmer has only multi element istds. It seems that Rh from Fluka is not too pure although it should because it is for ICP-MS applications.

Today I tried to use again In as ToxlabRat suggested to me. Ok, the drifting appeared not too soon but it appear again!

Talking about the high sensitivity that we are trying to get, ok you may be right but it is sth that we could reach easily and with stability two months before.   

Thank you very much for the information.


Posted 8/6/2010 12:09:56 PM
I strongly recommend SCP Science and CertiPrep as good places to order your reference standards from.  I have also used VHG Labs, Perkin Elmer, CPI International, Environmental Express, Fisher Scientific, Ricca and Ultra Scientific and out of all of those I have only had issues with one bottle of Ge from Ricca.  My first two choices are always CertiPrep and SCP Science as they have proved to have superior stability and very good pricing over the years.  If you would like, I can find out who your sales rep is with SCP and CertiPrep and get you those direct contacts.  Just let me know.


Posted 8/6/2010 12:18:07 PM
Thank you Tox!

You have helped me already too much! I will also like to thank you for the time that you have already spent for me. I think it will not be difficult to find out which are for my country. In case I will not be able, I will send you if you do not mind.


Posted 8/6/2010 12:18:11 PM
So you switched back to the Indium today and it also suffered from drift just as the Ge did?  If that is the case, then it is most likely not your solution after all and is probably something within the instrument that is causing the issues.  I still think that backing down on your sensitivity will be worth a try, because when I replace a detector and tune it all up I always get exceptional sensitivity, just as you have now, but I can never keep it that sensitive because it causes way too many issues, as the instrument will register even the slightest fluctuation in anything.  Back down your gas flow and see what happens.  You may have to back it down a lot.  In fact, why don't you back it down so that you are getting counts that are similar to those you had before changing detectors.

I would still suggest ordering standards from SCP and CertiPrep in the future.


Posted 8/6/2010 12:36:25 PM

I tried to use In today and I have seen that the stability is better than that I had with Rh but simmilar to that I had in the past. 

I believe that Rh solution was not the best we have ever bought, but I agree that sth else is also happening! With the old detector I used to work with at least 500000- 700000 counts for In and it was easy to keep it in a stable situation for at least the double time. I will follow your advise and I will bring the flow in lower values to see what happens there. 


Posted 10/17/2011 11:30:22 AM

I read that your service engineer had to replace a quadrapole in 2009. I believe that was on my instrument. Is your CSE out of Richmond, VA?

Posted 10/17/2011 5:48:24 PM
@ avitali:  Yes, my Perkin Elmer service engineer did replace a quadrapole on an Elan back in 2009 and he said it was the first time he had ever had to replace one in his entire career.  I am not sure where the instrument was located.  To the best of my knowledge his main area is in NC.  I know that on occasion when someone is on vacation he will extend his service area, so I guess it is possible that he could have replaced on in Richmond.  His name is Ron Buchanon--does that ring a bell?

Posted 10/19/2011 7:50:02 AM
@ ToxLabRat:

No, our service engineer is Gary Titi. He completely overhauled the instrument in the field!

New Power Board, Cleaned the DRC Cell (thought that was not possible, but it is), new AC Rods,

new quad, new lens, sample intro.

He did this work around September - October 2009. 
metal GeNIUS

Posted 2/10/2012 9:17:36 PM
 Hello ToxLabRat,

I have been reading your forums and realized you are a huge resource for troubleshooting.  I have been running sediment samples and use Yttrium for an Internal Standard for the mid-range masses., specifically for As and Se in this analysis.  During calibration, the percent recovery are around 105%; however, when the samples are analyzed the Y % recovery jumped to 500%-700%. None of the other IS are affected they remain within the acceptable range.  

I am a "newborn" to chemical analysis (2 years) and the instrument is only 4 years old. My understanding of matrices affect is usually an indication when the IS recovery is low.  

Can Y be in the sample? Any suggestion for correcting this?



Oh, I work with Elan 9000, no DRC

Posted 2/11/2012 4:42:39 AM
What amount of Yttrium are you adding to your solutions? Yttrium can be present in soils up to 20 ppm in my experience, so if you add 20 µg/L to a digest solution of 0.5 g soil/50 mL, you're bound to run into problems...

20 mg Y / kg soil * 0.0005 kg soil / 50 mL = 0.2 µg/mL of soil-based Yttrium in your digest...

Normally Y is mostly used as IR on soil digests for ICP-OES determinations, but the amount if Yttrium is much higher then (2-5 mg/L).

Try using Rh as IR for ICP-MS determination for light metals, and Ga or Ge for Se & As.

Posted 2/14/2012 10:44:55 AM
Yttrium is one of the best IS for alkali metals; Ca, K, Na, Mg and Ge is good with As and Se and you may use Tb (Terbium) for lead.


If you have problem with high IS recovery, you may dilute your sample to see if you have interferences in the sample caused to have high IS % recovery. Sc also works with alkali metals but I also avoided to have same IS for alkai metals as others since mostly you have alkali metals in any soils and IS % rec. might fell and I wasn't able to repoert my other metals too.

Posted 2/14/2012 12:18:54 PM
A clarification:

With 'light' metals I actually meant the 'light' transition metals (Ti - Zn), not the alkali or earth-alkali metals, IMO those metals are much better analyzed by ICP-OES

Posted 2/28/2012 5:22:36 PM
Why don't you run multiple internal standards at the same time, and if one fails but another within 50 amu of the analyte passes, recalculate the data. My internal standard solution contains Li, Be, Sc, Y, In and Bi.