Inductively Coupled Plasma - Mass Spectrometry (ICP-MS)

Agilent 7900 Inductively Coupled Plasma – Mass Spectrometer

Agilent 7900 Inductively Coupled Plasma - Mass Spectrometer (ICP-MS) is an analytical instrument that can be used for elemental analysis. It is widely used in the trace analysis of metals in given samples. ICP-MS allows superior detection capabilities (in the ppb range) particularly for the detection of rare earth metals. This technique facilitates the analysis of both simple and complex matrices while maintaining the matrix interference at a minimum as the ICP source allows high temperatures that allow temperatures of around 6,000 to 10,000 K.

Principle

In an ICP-MS, the sample is introduced to the nebulizer where it mixes with Ar gas to form an aerosol and then is passed into the central channel of the plasma. As they travel through the high temperature Ar plasma the aerosol droplets are dried, decomposed, atomized and finally ionized producing a rich source of positively charged ions. The ions are then transferred into the high vacuum region containing ion lenses and mass analyser through the interphase and the skimmer cones. Electrostatic lenses focus the ion beam and separate the positive ions from the unwanted neutral species. The Octapole reaction system is allowed the larger polyatomic interferences collide more often with the He atoms than the analyte ions and lose more kinetic energy. The potential barrier at the cell exit allows only the higher energy analyte ions to pass through to the mass analyser. Then the analyte enters to the quadrupole mass filter and separated based on mass to charge (m/z) ratio. Only the ions with a single m/z ratio to pass through the rods to the detector. The detector translates the number of ions striking the detector into an electrical signal that can be measured and related to the number of atoms of that element in the sample via the use of calibration standards.

Strengths

• The Agilent 7900 ICP-MS allows a higher matrix tolerance when compared to other ICP-MS systems leading to less dilutions for samples of high total dissolved solids (TDS) values
• The instrument allows up to 11 orders of low and high-level calibrations in a single run, leading to a wide dynamic range for measurements.
• The improved orthogonal detector system offers higher sensitivity and lower background noises leading to very high signal to noise
• The Octapole reaction system facilitates the removal of polyatomic spectral interferences.
• ICPMS allows multiple element analysis while offering high throughput
• Detection limits in the sub PPB level are facilitated

Limitations

• The samples have to be completely digested/dissolved prior to the analysis
• During quantitation, multiply-charged ions or polyatomic species can lead to problems
• This technique cannot be used to determine the contents of Carbon, Nitrogen, Hydrogen, Oxygen and Halogens in a given sample

Applications

• Quanititative analysis of elements present in pharmaceutical raw materials, textile materials, dyes, paints, fertilisers, soils, agricultural products, sediments, natural products etc.

Technical Specifications

•Sample Introduction System
          Nebulizer : MicroMist (borosilicate glass)
          Spray chamber : Scott-type double-pass (quartz)
          Controlled temperature range: –5 °C to +20 °C
•Plasma
          RF generator:    Solid state digital drive
                                    27 MHz
                                    Variable-frequency impedance matching
                                    500 W to 1600 W
          Torch:                One-piece (quartz)
                                    2.5 mm id injector
                                    ShieldTorch system
•Interface
          Sampling cone:  1 mm diameter orifice
          Standard:            Ni-tipped with Cu base
          Skimmer cone:   0.45 mm diameter orifice
          Standard:            Ni
•Mass Analyzer
          Quadrupole : Frequency: 3 MHz Hyperbolic rod profile
          Mass range : 2–260 u
          Mass resolution : Variable from 0.3 u to 1.0 u
          Typical mass calibration stability : < 0.05 u per day < 0.1 u per 6 months
          Abundance sensitivity (at Cs) : Low mass side: ≤ 5 × 〖10〗^(-7)
          High mass side: ≤ 1 × 〖10〗^(-7)