The ASU has just purchased a 7850 ICP-MS spectrometer from Agilent Technologies with an SPS4 series auto-sampler (August 2025). This is an upgrade to our current 7700x instrument. This upgrade will allow us to continue offering offer our clients ICP-MS services with updated technology. Lower detection limits and greater matrix tolerance are expected as compared to the 7700x. The new SPS4 auto-sampler with extraction system and built-in enclosure are expected to contribute to these improved detection limits.
Image from Agilent Technologies Brochure
ICP-MS MATRIX TOLERANCE
Traditionally, ICPMS instruments were used to determine a samples elemental composition (through ion analysis) primarily for water samples and other samples of known composition.
For environmental laboratories, submitted water samples are quite variable in their composition and can range from 'clean' drinking water samples to solutions with total dissolved solids (TDS) exceeding the instruments tolerance of 0.1-0.2%. To minimize time consuming pre-analysis dilution steps, the 7700x employs a proprietary gas dilution technique known as HMI or high matrix introduction. The 7850 instruments continues to improve on the 7700x by offering an upgraded UHMI (Ultra High Matrix Introduction). This will allow the instrument to handle samples with up to 25% Total Dissolved Solids as compared to 3% for the HMI.This will help to prevent cone clogging (and signal drift), reducing maintenance requirements for difficult samples.
HMI-High Matrix Introduction
Image from Agilent Technologies Brochure
The following papers from Agilent Technologies illustrate how the HMI interface can be used to analyze samples with high TDS.
Collision/Reaction Cells in ICPMS
Isotopic (polyatomic and isobaric) interferencies are common in ICP-MS and there are many methods which these interferencies can be reduced or removed.
Reactive gas (such as hydrogen or ammonia), can be used to remove selected interferencies, but in certain instances, new matrix dependant interferencies can be created which can complicate an analysis. Sensitivity for certain analyte ions can also be significantly reduced using reactive cell gases.
For environmental samples, where information regarding the sample composition is not available, collision mode can be a preferred way to minimize interferencies.
Collision mode uses a non-reactive gas (such as helium) to remove interferencies by a process known as kinetic energy discrimination (or KED). The principle behind this interference removal technique is simply that molecular ions are bigger than single ions. Bigger = more collisions with the inert gas. The interfering ions are thus slowed down more than the analyte ion and with the appropriate hardware can be separated.
Our ICP-MS 7700x instrument employs a universal collision mode "octopole reaction system" (ORS3).
Octopole Reaction System3
Image from Agilent Technologies Brochure
For details on the operation of the collision mode, please refer to the following agilent literature:
Collision/Reaction Cells in ICP-MS (PDF, 717 KB)
7700x ORS3 and Helium Mode (PDF, 1.13 MB)
At the ASU ICP-MS Location (After Installation)
October 1st, 2013
Good detection limits, instrument stability and relatively straightforward to use!