To get the lowest detection limits on a single quad ICP-MS you can use reaction chemistry for example using Xe as a reaction gas to reduce the O2 backgrounds. If the DL requirements are less stringent then we have a mode called High Energy Helium mode which helps on the 34 isotope (or you can measure SH under hydrogen mode).
The 8800 & 8900 have a quadrupole before the Collision Reaction Cell capable of operating at unit mass resolution which removes all isotopes other than the target m/z, it can also operate as a bandpass filter should this be of interest but the unique feature is the ability of Q1 to operate at unit mass resolution.
Having two separate mass filters also significantly improves abundance sensitivity (a measure of peak tailing from an intense matrix peak) which has benefits in itself even when using no cell gas (or He KED). An example would be having access to the boron isotopes in a heavy organic or Mn in a high Fe content.
Having Q1 and Q2 either side of the CRC also means that using a fixed mass difference when operating under mass shift can preserve the isotopic information - in fact S measurement by isotope dilution (in biodiesel) was one of the first pieces of work we performed in conjunction with the University of Gent (they have a paper on this) and only took a couple of day's work.
This example uses O2 as reaction gas to shift S away from the O-based and C-based interferences. However at SO there are several potential interferences such as Ca, Ti ... having a quad before the cell removes those interferences beforehand. Finally S can interfere with itself, for example 34S has interferences from 32S18O & 33S17O - but fixing the mass difference to 16amu means ONLY the +16 transition is used (so 34S16O) preserving the isotopic information.
This is the same even when using complex reaction chemistry such as for Ti under ammonia reaction mode, one of the cluster ions can be Ti(NH3)6 so fixing the mass difference to 102 and scanning the isotopes of Ti will preserve the ratios/isotopic pattern. Even if isotopic ratios are not important it provides a level of confidence when confirming that 2 or more isotopes give the same results. When using bandpass this is not necessarily the case so it can be difficult to have confidence in the result when each isotope gives a different answer (i.e. which isotope is less wrong...).
When designing a test for any instrument it's important to make it appropriate/difficult enough to separate the systems' true performance.
Just as a BTW:
QQQ in inorganic terms has become a little confused. This is not the case in organic chemistry where the term QQQ has been used for many years - the original organic QQQ actually had 3 quads Q1 operated at unit mass resolution as did Q3 but Q2 was as an r.f. ion guide inside an enclosure which could be pressurised and induce collision-based fragmentation of the organic compound. As more became understood they realised that a Quad was not so efficient as an ion guide so changed to multipoles such as Hexapole and Octopole designs as these offer greater ion transmission efficiency inside the pressurised cell.
Moving forwards in time and back to inorganic QQQ this is what is used today on our Agilent systems with an Octopole as a collision/reaction cell separated by two "true" quadrupoles capable of operating at unit mass resolution (sorry for using the term "true"). The only real definition of QQQ should be one that is capable of MS/MS (or tandem MS) as I mentioned above.
This may sound like a minor rant but there is a lot of confusion in the community regarding terminology but according to the IUPAC definition (term 538 from the 2013 Recommendations), the term "triple quadrupole" applies to a "Tandem mass spectrometer comprising two transmission quadrupole mass spectrometers in series, with a (non-selecting) RF-only quadrupole (or other multipole) between them to act as a collision cell."
Either way - run a set of hard samples to separate the performance characteristics and make an informed decision.
ICP-MS Applications Specialist
Agilent Technologies LDA UK Ltd.
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From: PLASMACHEM-L: Analytical Chem.(ICP's, DCP's, MIP's). [mailto:[log in to unmask]] On Behalf Of Lyndon Palmer
Sent: 07 March 2017 02:50
To: [log in to unmask]
Subject: Agilent Triple Quad ICPMS? - 8800 or new 8900
For any users of the Agilent Triple Quad, I am wondering what peoples experience has been with the Agilent Triple Quad - 8800 or new 8900 compared to the Agilent 7900?
Are there any other Triple Quad instruments or equivalent on the market as yet?
We are currently using an old Agilent 7500CX at present for plant / grain / food analysis. We are happy with the performance except for the non-analysis of S, which we would like to be able to analyse in the same run rather than on ICPOES or some other way.
We currently analyse the following elements: Al, As, B, Ca, Cd, Co, Cr, Cu, Fe, K, Mg, Mn, Mo, Na, Ni, P, Pb, Se, Ti & Zn.
Expanded areas of particular interest and other questions are:
1. S analysis.
* I have read that the 7900 can analyse S - is that so and how is it done?
2. Better P analysis.
3. As and Se at quite low levels and removal of potential interferences - oxides and doubly charged species.
4. Does the Triple Quad reduce or get around the oxide interferences on elements e.g. MoO and Cd etc.
Mr. Lyndon Palmer
Flinders University Plant Nutrition
School of Biological Sciences
Carpark7, Room 201
South Australia, AUSTRALIA 5042
Tel. +61 8 8201 3536
email : [log in to unmask]<mailto:[log in to unmask]>