ICP-OES vs ICP-MS

Both inductively coupled plasma optical emission spectroscopy (ICP-OES) and inductively coupled plasma mass spectrometry (ICP-MS) are analytical techniques important for the analysis of trace elements in a host of mediums, from measuring contaminants in water or soil, determining the origin of wines and foods, detecting heavy metals and rare earth elements and petrochemical analysis, to determining safety and purity of pharmaceuticals and cosmetics. But how do they work, how do they compare and when should one be employed over the other? In this infographic we explore the answers to these questions and more. As atoms may be excited or ionized, optical emission spectrometry shows atomic lines as well as ionic lines. The lower limit of detection for ICP-OES is parts per billion (ppb). The lower limit of detection for ICP-MS extends to parts per trillion (ppt). ICP-OES and ICP-MS use the same method of sample excitation, but with di„erent methods for detection. Whether you chose ICP-OES or ICP-MS will depend upon a number of factors including: However, for solid samples, pretreatment is typically required to breakdown the sample for analysis. This analysis is important for: As with ICP-OES, in ICP-MS, atoms and ions within a sample are excited with plasma. The excited species are directed to the mass spectrometer where they undergo separation at the quadrupole and their mass detected. What is ICP-OES? ICP-OES, sometimes also referred to as inductively coupled plasma atomic emission spectroscopy (ICP-AES), is based on the measurement of excited atoms or ions. Di„erent elements produce characteristic signatures which can be used to identify and quantify them within a sample. What is ICP-MS? How do ICP-OES and ICP-MS compare? Applications Sample Solution Drain Spray chamber and nebulizer signal conversion Cones Ar Ar Load Torch Vacuum pumps coil detector quadrupole Lens Solution introduction system Inductively coupled plasma Interface Mass spectrometer Argon supply Sample Detector ICP-OES Spectrum ICP-MS Spectrum Monochromator Mass separation device Nebulizer Radiofrequency Cell Plasma A B MS Interface Mass separation device Ion detector Available budget Regulatory compliance (which methods are approved for use by regulatory authorities for the element of interest in a given sample type) Properties of the sample being analyzed (complex or simple matrix) Laboratory throughput Sensitivity of detection required (ppb vs ppt) Skill of available personnel ICP-OES ICP-MS CONS Less sensitive Not suitable for radioactive elements requiring analysis by gamma-ray spectroscopy Requires high volumes of gas Has a high potential for spectral interference PROS Cheaper Copes with most matrix types Method development is easier Is suitable for high throughput Analytical grade solvents are suitable for use PROS CONS Su„ers from matrix and ionization e„ects More expensive to buy, maintain and run Needs high purity grade reagents Requires more specialist operators Method development is more complex Trace elements can be measured in liquid samples such as Drinking water • Organic solvents • Petrochemicals Foundation make-up • Wastewater • Beverages Soil • Rock • Tablets • Glass • Ceramics • Plants • Rice And solid samples such as Determining authenticity Detecting environmental contaminants Monitoring of radioactive waste Petrochemical analysis Checking food safety Ensuring the safety and purity of cosmetics and pharmaceuticals wavelength, nm signal intensity, counts 4000 250,000 300,000 350,000 400,000 450,000 500,000 8000 120000 160000 1 mg kg -1 Pu 1% nitric acid 1 mg kg -1 U ICP was developed for OES by Fassel et al. in the US and Greenfield et al. in the UK in the mid-1960s but weren’t available commercially as a combined instrument until 1974. Very sensitive Has a wide dynamic range Detects the ions themselves rather than the emitted photons, providing isotopic information and mass data Is able to detect the largest number of elements of the comparative elemental analysis techniques Works with small sample volumes Faster Only su„ers limited spectral and isotopic interference Plasma Photons Detector Polychromator Optical lattice Acid digestion and hydride generation are often used to prepare the sample solution for effective elemental analysis. The ICP is then used to excite and ionize the sample’s atoms. 1 Once the atoms in the sample are excited, they are no longer in a stable state. As the atoms and ions return to an unexcited, stable state, they spontaneously emit electromagnetic radiation at wavelengths characteristic of the sample’s elements. 3 A flowing gas, such as argon, is ionized to produce a high energy and temperature (7,000 – 10,000K) inductively coupled plasma (ICP) source. 2 Using a spectral device and mono- or polychromators, the emitted energy is fragmented into the constituent wavelengths and the photons are detected via charge-coupled devices (CCD) and charge injection devices (CID). 4