Inductively Coupled Plasma Mass Spectrometery

The ASU has just purchased a 7700x ICP-MS spectrometer from Agilent Technologies with an ASX-500 series autosampler and a clean enclosure. This will allow us to offer our clients much lower detection limits than are currently achievable with our ICP-OES spectrometer.

7700x ICP-MS

Image from Agilent Technologies Brochure


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.

HMI technique

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.

Simple, Reliable Analysis of High Matrix Samples According to US EPA Method 6020A using the Agilent 7700x ICPMS (PDF, 236 KB)

Direct Analysis of Undiluted Soil Digests Using the Agilent High Matrix Introduction Accessory with the 7500cx ICP-MS (PDF, 264 KB)

Performance Characteristics of the Agilent High Matrix Sample Introduction (HMI) Accessory for the 7500 Series ICP-MS (PDF, 235 KB)

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

Dr. Graham with the ICP-MS

Good detection limits, instrument stability and relatively straightforward to use!