ICP-MS (CRF Owned Facility) IIT Delhi

Brief on ICP-MS: Inductively Coupled Plasma Mass Spectrometry or ICP-MS is an analytical technique used for elemental determinations. The technique was commercially introduced in 1983 and has gained general acceptance because of its superior detection capabilities, particularly for the rare-earth elements (REEs). ICP-MS has many advantages over other elemental analysis techniques such as atomic absorption and optical emission spectrometry, including ICP Atomic Emission Spectroscopy (ICP-AES) are

• Detection limits for most elements equal to or better than those obtained by Graphite Furnace Atomic Absorption Spectroscopy (GFAAS)
• Higher throughput than GFAAS.
• The ability to handle both simple and complex matrices with a minimum of matrix interferences due to the high-temperature of the ICP source.
• Superior detection capability to ICP-AES with the same sample throughput.
• The ability to obtain isotopic information.
• Fast analysis of multiple elements
  
  

An ICP-MS combines a high-temperature ICP (Inductively Coupled Plasma) source with a mass spectrometer. The ICP ionizes the atoms of the elements in the sample. These ions are then separated and detected by the mass spectrometer.

Figure1 shows a schematic representation of an ICP-MS. Argon gas flows inside the concentric channels of the ICP torch. The RF load coil is connected to a radio-frequency (RF) generator. As power is supplied to the load coil from the generator, oscillating electric and magnetic fields are established at the end of the torch. When a spark is applied to the argon flowing through the ICP torch, electrons are stripped off of the argon atoms, forming argon ions. These ions are caught in the oscillating fields and collide with other argon atoms, forming an argon discharge or plasma.

The sample is typically introduced into the plasma as an aerosol, either by aspirating a liquid or dissolved solid sample into a nebulizer or using a laser to directly convert solid samples into an aerosol. Once the sample aerosol is introduced into the ICP torch, it is completely desolvated and the elements in the aerosol are converted first into gaseous atoms and then ionized towards the end of the plasma. The most important things to remember about the argon plasma are:

• The argon discharge, with a temperature of around 6000-10000°K, is an excellent ion source.
• The ions formed by the ICP discharge are typically positive ions, M+ or M+², therefore, elements that prefer to form negative ions, such as Cl, I, F, etc., are very difficult to determine via ICP-MS.
• The detection capabilities of the technique can vary with the sample introduction technique used, as different techniques will allow differing amounts of sample to reach the ICP plasma.
•Detection capabilities will vary with the sample matrix, which may affect the degree of ionization that will occur in the plasma or allow the formation of species that may interfere with the analyte determination.

Feature of Agilent ICP-MS 7900 with UHMI

1. Unprecedented matrix tolerance—Agilent’s 7900 ICP-MS has a robust plasma and optional Ultra High Matrix Introduction (UHMI) technology that enable the user to routinely measure samples containing up to 25% total dissolved solids (TDS)—100 times higher than the traditional matrix limit for ICP-MS.
2. Widest dynamic range—the new orthogonal detector system (ODS) delivers up to 11 orders of magnitude dynamic range from sub-ppt to percent-level concentrations, enabling you to measure trace elements and majors in the same run.
3. Better trace level detection—novel interface design and optimized expansion-stage vacuum system increase ion transmission, providing >109cps/ppm sensitivity at <2% CeO, while the ODS provides increased gain and reduced background for improved signal to noise.Faster analysis of transient signals—with 10,000 separate measurements per second, the 7900 ICP-MS provides short integration times for accurate analysis of transient signals.
4. Improved productivity—Ultra-high matrix introduction (UHMI) technology combined with optional Integrated Sample Introduction System (ISIS 3) and ODS ensures almost any sample can be run and quantified across the widest dynamic range, eliminating the extra time and cost associated with reruns due to over range results.

Brochure of the system

Application notes and other literatures

Samples

Sample Preparation for ICP-MS

List of elements can be analysed using ICP-MS (Agilent 7900) at IIT Delhi

Note : It is recommended to the user, to discuss the nature of the samples and the data quality required with the ICP-MS operator, this way, proper isotopic selection and/or sample preparation methods can be undertaken to meet the end user's needs.

Recommended Sample Preparation Methodologies:

Recommended Sample Preparation Methodologies:
Samples which doesn’t require acid digestion prior analysis –
Minimum Quantity Required – Liquids: 5-10ml 
Water/ Aqueous Samples – Water samples containing particulates must be removed before analysing using ICP-MS. Hence, requires the samples to be have been filtered through 0.2 µm filter and/or acidified during collection.

Samples which require digestion prior analysis –

Minimum Quantity Required – Solids: 100-500mg ; Liquids: 5-10ml

Sediment, Soil and Rock Samples – Samples are digested using acid digestion procedure in order to dissolve most silicate minerals. This digestion is carried out in open vessels on a hot-plate or using microwave digester (in order to digest volatile elements). 

Geological Samples – Rare-earth-element (REE) samples are typically prepared using a sodium peroxide sinter method. In this method the ground sample is mixed with sodium peroxide in a carbon crucible and placed in a muffle furnace. The resulting sinter is leached with water and acidified with nitric acid before analysis.

Biological and Organic Samples – These samples are generally digested using a closed-vessel microwave digestion procedure that is appropriate to the matrix of the sample. The high temperature and pressures reached in the microwave digestion system can dissolve most biological samples, including fatty tissues. This is also the best method for digesting organic samples, including crude oils.

Note: The above mentioned sample preparation methodologies are just for information purposes and has to be undertaken by the user itself at their own facility. Only acid–digestion facility shall be provide by CRF- IIT Delhi, in which case, the protocol if any has to be discussed with the operator before submitting the samples for analysis. Blood, Serum, Urine, Stool, Viral or other contagious micro-organism, or any other biological samples which require special handling, discarding and/or ethical requirements will not be accepted directly. For any such samples, kindly discuss with the operator before submission for the required procedures/ sample preparation to follow if any.

Analysis time: Samples are run in batches of 50-100 samples at one run, although each samples roughly takes 2-3 mins for analysis, the total analysis time depends on the number of elements to be detected, number of standards to be run, and setup and calibration time. Post analysis, data needs to be processed so as to be consumed as usable information.

Important – Samples submitted in person or via post, without proper communication and prior approval by the operator or the consent authority, will not be entertained. Payments processed regarding the same, without prior approval of the operator or the consent authority, will not be the direct responsibility of CRF-IIT Delhi.