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I nductively C oupled P lasma M ass S pectrometry or ICP-MS. What you can do using ICP-MS instrument. Maather Sawalha ( Ph.D ) Water and Environment Studies Institute (WESI) An- Najah National University. ICP-MS. What is it? How does it work? Main components Cost to analyze samples
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Inductively Coupled Plasma Mass Spectrometry or ICP-MS What you can do using ICP-MS instrument MaatherSawalha (Ph.D) Water and Environment Studies Institute (WESI) An-Najah National University
ICP-MS • What is it? • How does it work? • Main components • Cost to analyze samples • Applications (idea’s)
What is ICP-MS • Inductively Coupled Plasma Mass Spectrometry or ICP-MS is an analytical technique used for elemental determinations • Employs plasma as ionization source and a mas spectrometer (MS) analyser for detect ion • It can perform qualitative, semi quantitative, and quantitative analysis. • Developed in 1980’s.
Reasons for the growing popularity • Performs multi-elemental analysis with excellent sensitivity and high sample throughput • Instrument detection limits are at or below ppt level • Productivity is unsurpassed by any other technique • Isotopic analysis (one isotope or ratio)
How does ICP-MS work? • Samples introduced into an argon plasma as aerosol droplets. • The plasma dries the aerosol, dissociates the molecules, and then removes an electron from the components, forming singly-charged ions, • Ions are directed into a mass filtering device known as the mass spectrometer. • Figure 1. The ICP Torch showing the fate of the sample (PerkinElmer, Inc.)
An ICP-MS consists of • Sample introduction system • ICP torch and RF • Interface • Vacuum system • Collision/reaction cell • Ion optics • Mass spectrometer • Detector • Data handling and system controller
Sample introduction system • provides the means of getting samples into the instrument • composed of a nebulizer and spray chamber • The liquid sample may be introduced to a nebulizer by a peristaltic pump or through self aspiration that creates an aerosol of fine droplets. • The fine droplets are passed through a spray chamber before they are allowed to enter the plasma
ICP torch and RF coil • ICP torch generates the argon plasma (6000 °C) • plasma is generated by passing argon through a series of concentric quartz tubes (the ICP torch) that are wrapped at one end by a radio frequency (RF) coil. • Energy supplied to the coil by the RF generator couples with the argon to produce the plasma. • During their voyage into the plasma, the liquid droplets, are dried to a solid and then heated to a gas, then absorb more energy, release one electron to form • singly charged ions. • The singly charged ions exit the plasma and enter the interface region. • Figure 1. The ICP Torch showing the fate of the sample (PerkinElmer, Inc.)
The interface – sampling ions • Allows the plasma and the ion lens system to coexist (Due to highly different T and P of each) • Allows ions generated by the plasma to pass into the ion lens region. • It consists of two or three inverted funnel-like devices called cones (opening is about 1mm). • Downstream focusing of the ion beam is required by the use of a single or a series of charged devices called ion lenses • If three cones are used then there is no need for ion lens Figure 2. The interface region of an ICP-MS.
The vacuum system • provides correct operating pressure • The distance from the interface to the detector <=1 meter • ions need not to collide with gas molecules during the travel • so gas molecules are removed by using a combination of a turbo molecular pump and mechanical roughing pump
Ion deflection device • separates ions from neutrals and photons • Ion beam exiting the interface region of the instrument contains some non-ionized materials – neutrals – and photons. • the ions are turned by the quadrupole at a right angle for their entry into the filtering quadrupole or universal cell • The ion beam is so well focused not to make contact with the quadrupole (then no need to clean it)
The collision/reaction cell “the universal cell” • Interferences caused when ions carry a mass-to-charge ratio that is identical to that of the analyte ion • the interfering ion is physically larger than the analyte ion. • Passing both through a cloud of inert gas molecules, the interferent ion will collide more frequently with the inert gas atoms this removes a certain amount of the kinetic energy possessed by the ion. • Analyte ion will retain more of its energy when compared to the interferent ion. • An energy barrier is placed at the exit of the cell • Collision cell can be a rxn cell by using un inert gas that converts charged interfering ions into inert ones
It can perform on all modes to remove interference The ability of a well-designed ICP-MS to remove interferences using its standard mode, collision mode, and reaction mode can be readily seen in Figure 4.
The mass spectrometer • The mass spectrometer separates the singly charged ions from each other by mass, serving as a mass filter. • A quadrupole works by setting voltages and radio frequencies to allow ions of a given mass-to-charge ratio to remain stable within the rods and pass through to the detector, while others are ejected. • the quadrupole is capable of scanning at a rate > 5000 atomic mass units (amu) per second. Schematic of quadrupole mass filter.PerkinElmer, Inc.)
The detector – counting ions • The ions exiting the mass spectrometer strike the active surface of the detector (dynode) and generate a measurable electronic signal. • a dynode, releases an electron each time an ion strikes it. • released electrons strike a second dynode where more electrons are released until a measurable pulse is created. By counting the pulses generated by the detector, the system counts the original ions. Discrete dynode detector used on the ELAN ICP-MS systems.(Courtesy of PerkinElmer, Inc.)
Data handling and system controller • The software compares the intensities of the measured pulses to those from standards, which make up the calibration curve, to determine the concentration of the element. • The software translates the ion counts measured by the detector into information • provide data in one of four ways – semi-quantitative analysis, quantitative analysis, isotope dilution analysis, and isotope ratio analysis.
liquid samples limitations • ICP-MS has some limitations as to the amount of total dissolved solids in the samples. • Generally, no more than 0.2% TDS for best instrument performance and stability • many sample types, including digested soil and rock samples must be diluted • If samples with very high TDS levels are run, the orifices in the cones will eventually become blocked, causing decreased sensitivity and detection capability and requiring the system to be shut down for maintenance.
Approximate costs Costs depends mainly on Number of samples Number of elements to be analyzed Time required
Applications Elements and isotopes in • Soil • Water/wastewater • Food • Human and biological samples • Industrial like pharmaceutical………..