Difference between ICP-OES and ICP-MS

Assessment of Genotoxic Impurities
January 27, 2021
Difference between ICP-OES and ICP-MS

Difference between ICP-OES and ICP-MS

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Elemental impurities affect drug effectiveness, it doesn’t have any therapeutic benefit but has a toxic effect on the patients. Elemental impurities may be present in drug products due to different sources such as catalysts, raw materials, excipients, equipment, or packing materials. As per recent necessities, elemental impurities guidance of ICH Q3D, USP Chapters <232>, made effective shifting the old requirements for heavy metals. The limits are much lower for most toxic metals. The earlier heavy metal method was not specific and accurate for each one hence new testing procedure applied by using sophisticated, costly, and sensitive technology such as inductively coupled plasma optical emission spectroscopy (ICP-OES) or inductively coupled plasma mass spectrometry (ICP-MS). 

Difference between ICP-OES and ICP-MS:

ICP-OES and ICP-MS are vital analytical techniques in determination of trace elements analysis from drug substances and drug products. This article describes the difference between ICP-OES and ICP-MS.

Easy Evaluation

CostCost of ICP-OES is less than ICP-MS but operation cost is high due to higher consumption of argon gas. Asper ICP-OES, photons have no mass, no memory effects hence it’s simple technique for use hence it requires less maintenance.ICP-MS is more expensive because of its handling cost and it requires a cleanroom. It requires extra maintenance due to its spare parts. Argon gas consumption is similar.
ConsumablesThe main consumable supplies in ICP-OES are in the plasma torch and in the sample introduction area.Consumables are placed inside the mass spectrometer which is, sampler and skimmer cones and another main consumable is the detector.
Handling and Sample PreparationHandling usually easier to operate than ICP-MS. ICP-OES is exceptional for its speed, cost and ease of sample analysis. It allows relatively big amount of dissolved solid and more matrix tolerant. In single sample analysis up to 60 elements can be screened within minute. sample requirement generally from 0.1g to 1.0gHandling is easy but sample preparation is more crucial because it dissolved in 2% HNO3 v/v, a total dissolved solids content. It’s is having the benefit of determining much lower concentrations of elements present. Analysis of high total dissolved solids samples is unfit because cones of the interface can be blocked. Ideally the conc. restricted to 0.2% (2 g/L) of dissolved solids which requires dilution of samples.
DetectionIt is moderately sensitive multi-element technique with a dynamic linear range and sensible detection range suitable over concentrations from ppm to ppb. Isotope ratio can’t establish.Exceptional sensitivity for a multi-element technique for trace analysis and for high precision isotope ratio studies. ICP-MS is capable of ultra-trace detection range from ppb to ppt.
PrincipalIn ICP-OES there is excitation of electrons of several elements in an atmosphere termed as plasma and the diffusion of light after electron release.Inductively coupled plasma source converts elemental atoms into ions to sample and were isolated and detected by a mass spectrometer. Mass of elemental ions formed by high-temperature argon plasma measured by ICP-MS. Ions formed in the plasma are divided from the mass to the load, making it possible to detect and quantify unknown materials. MS then categories the ions according to their mass/charge ratio followed by leading them to an electron multiplier tube detector that identifies and quantifies each ion.
Method DevelopmentMethod development is quite easy.Method development is significantly more difficult than for ICP-OES.
Grade of ChemicalsAnalytical grade chemicals, solvents and reagents can be used for analysis.It requires high purity grade solvents, reagents and chemicals.
Instrument Handling ExpertiseOperation of ICP-OES and samples analysis done by normal analyst and calibration can be done by expert analyst.Operation of ICP-MS is done by a highly sophisticated instrument and it’s supervised by a highly skilled professional.


Elemental impurity requirements are much more stringent than the past heavy metal. Due to the complex sample matrix and the stringent limits, analysis involve a more sensitive, precise, accurate method of analysis. It requires highly sophisticated, sensitive, and expensive testing instruments and procedures. 

This article describes the comparative difference between both techniques this information can be helpful to assess the usefulness of techniques as per requirement.

range of measurement


  1. ICH Q3D (R1) Guideline for Elemental Impurities,
  2. Elemental Impurities in Pharmaceuticals: Updates: USP Website: http://www.usp.org/chemical-medicines/elemental-impurities-updates,
  3. Approaches to Maximize Performance and Reduce the Frequency of Routine Maintenance in ICP-MS,” R. Brennan, J. Dulude, R.J Thomas, Spectroscopy
  4. Measuring Elemental Impurities in Pharmaceuticals: A Practical Guide, Robert. J. Thomas; CRC Press, Boca Raton, FL, ISBN 9781138197961, February 2018,
  5. Choosing the Right Trace Element Technique: Do you know what to look for,” R.J. Thomas, Today Chemist at Work.

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