Inductively Coupled Plasma Mass Spectrometer

What is the Inductively Coupled Plasma Mass Spectrometer?

An ICP-MS ionizes samples in an argon plasma and measures ions by mass spectrometry. It is chosen for the lowest trace-element detection limits, multi-element analysis and isotope ratio measurement in environmental, clinical and pharmaceutical work.

Overview

A plasma torch at atmospheric pressure ionizes the sample, and ions pass through interface cones into a vacuum region where a mass analyzer separates them by mass-to-charge ratio. Quadrupole instruments scan rapidly across masses for multi-element analysis, while sector field and multicollector instruments provide higher resolution or precise isotope ratios. Collision and reaction cells filled with helium or hydrogen suppress polyatomic interferences so that elements such as arsenic, selenium and vanadium can be measured in chloride and sulfate matrices. Sample introduction uses a nebulizer and spray chamber, and laser ablation or chromatography interfaces extend the technique to solids and speciation. Detection limits reach nanograms per litre and below, making ICP-MS the method of choice for elemental impurities and ultra-trace studies.

How does it work?

In atomic spectroscopy a sample is converted into free atoms in a flame, graphite furnace, plasma or hydride generation cell. The atoms absorb or emit light at wavelengths characteristic of each element. Atomic absorption passes a hollow-cathode lamp emission line through the atom cloud and measures the decrease in intensity according to the Beer-Lambert law. Atomic emission excites atoms in a plasma or flame and measures the light they emit as they relax. Atomic fluorescence excites atoms with a source and measures emitted light at a right angle, giving high sensitivity for hydride-forming elements. Inductively coupled plasma sources reach 6000 to 10000 K, atomizing and ionizing most elements; the resulting ions can be counted by mass spectrometry for very low detection limits. Calibration uses series of standards, internal standards, and background and matrix correction.

What are the key features?

• Quadrupole, sector field or multicollector mass analyzers
• Collision or reaction cell for interference suppression
• Detection limits in the nanogram per litre range
• Isotope ratio measurement capability
• Laser ablation and speciation interface options
• Automated tuning, internal standardization and software QA

What are the technical specifications?

A typical inductively coupled plasma mass spectrometer configuration offers mass range of 2–260 amu, detection limit of 1–100 ng/L typical, mass analyzer of quadrupole with collision cell, resolution of 0.3–1.0 amu, plasma power of 1500–1600 W and collision gas of helium or hydrogen. Values are indicative of the product class; the exact figures for each configuration are confirmed on the quotation and the calibration documents supplied with the instrument.

Which applications is it used for?

The Inductively Coupled Plasma Mass Spectrometer is used in elemental impurities per ICH Q3D and USP <233>, ultratrace metals in water and soil, clinical and forensic trace element measurement and isotope ratio studies in geochemistry and nutrition. Across the wider Atomic Spectroscopy class, laboratories also deploy it for elemental impurity testing of pharmaceutical materials, trace metals in drinking water, wastewater and soil and food safety and nutritional element analysis.

Which standards and certifications apply?

Relevant standards and methods include USP <730> Plasma Spectrochemistry, USP <233> Elemental Impurities — Procedures, ICH Q3D Elemental Impurities, ISO 11885 Water quality — ICP-OES determination of elements, ISO 17294-2 Water quality — ICP-MS determination of elements, US EPA Method 200.7, US EPA Method 200.8, ISO/IEC 17025 and IEC 61010-1. Certification candidates for this model are CE, ISO 9001 manufacturing and 21 CFR Part 11 software compliance; each is to be confirmed for the specific configuration before shipment, and certificates are supplied only where they have been issued.

Atomic spectroscopy installations need gas supplies, extraction and, for plasma systems, argon of high purity and substantial electrical power. Acetylene and nitrous oxide require proper regulators, flashback arrestors and ventilation. Sample preparation by acid digestion is a major source of error and contamination, so ultrapure acids and clean vessels are essential. Hollow-cathode lamps have limited life and may need warm-up and alignment. Background correction, internal standards and matrix matching control interferences from easily ionized elements, molecular species and viscosity. Verify performance daily with calibration standards and check stability with a continuing calibration verification. Maintain service records and monitor lamp, torch and graphite tube usage.

How do I select the right Inductively Coupled Plasma Mass Spectrometer?

Select ICP-MS when detection limits or isotope information are decisive, for example elemental impurity testing, clinical trace analysis or geochemistry. Specify the element list, detection limits, matrices and whether speciation or solid sampling is required. Confirm argon, vacuum and electrical services, and choose collision cell or high-resolution configuration based on the interferences expected.

How does it compare with other Atomic Spectroscopy variants?

Choose the atomic technique by element, concentration and matrix. Flame atomic absorption is simple, robust and suited to milligram per litre levels in routine water, soil and metal samples. Graphite furnace atomic absorption reaches microgram per litre and below for a limited number of elements with small sample volumes. Inductively coupled plasma optical emission handles multi-element analysis at microgram per litre to percent levels with wide linear range. Inductively coupled plasma mass spectrometry reaches nanogram per litre and below for most elements and can measure isotopes. Atomic fluorescence is efficient for mercury, arsenic, selenium and antimony after hydride generation. Microwave plasma emission is an alternative to flame for some elements using nitrogen instead of acetylene. Confirm required detection limits, sample throughput, number of elements and available gases before selecting.