Which is a better choice?- ICP-OES or ICP-MS
In this concluding part of this series, we will be comparing the two ICP techniques in order to know which one is right for you and when.
ICP-OES and ICP-MS are preferred techniques for trace and ultra-trace metal estimations. Merits and demerits of both techniques along with Graphite furnace Atomic Absorption Spectroscopy have been discussed earlier. The present article will help you decide between the two based on your budget and analysis requirements.
ICP-MS Schematic Diagram (Image Courtesy : http://biochem.pepperdine.edu/)
ICP-OES Schematic Diagram (Image Courtesy : http://www.chemiasoft.com/)
The initial cost is a limiting factor for most laboratories. However, the cost can be weighed against requirements of level of sophistication, sample handling capabilities, automation and software features. Generally, the initial investment on ICP-MS will be higher but it is difficult to quantify as the quoted price will be dependent on accessories and the backup support offered by the supplier.
ICP-MS requires greater maintenance due to limited lifetime of some critical components. The cost can escalate further for ultra trace analysis because of requirement of clean room and ultra pure reagents.
Both ICP-OES and ICP-MS are highly sophisticated techniques but ICP-MS does require special operator skills. However, user friendly software available today have reduced the gap.
The working range for routine determination is an important deciding factor. Both techniques require sample introduction in liquid form. ICP-OES is suitable over concentrations from 0.0002 to 1000ppm whereas ICP-MS is capable of ultra-trace determinations from 0.0005 to 100ppb.
Total Dissolved Solids
ICP-OES is capable of handling samples with a total solids content up to 20%. In comparison ICP-MS is limited to about 0.2%for trouble free operation. This makes ICP –OES a preferred choice for analysis of geological and other inorganic materials.
Sample availability is often a limiting factor. ICP-OES has sample requirement generally from 0.1 to 1.0g but ICP-MS can be used when smaller sample sizes from 0.01-0.1g are available.
ICP-OES provides analysis of elements from Li- U except for C,H,O, N, F, Cl, Br and noble gases. ICP-MS can be used for all elemental determinations with the exception of S.
Linear Dynamic Range
ICP-MS offers a wider linear dynamic range of 108 whereas ICP-OES is lower 106.
Both techniques give high sample throughputs with capabilities of up to 40 elements /minute in each sample. The turn-around time between samples ranges from 3-5 minutes.
ICP-MS has a distinct advantage as detection is based on mass to charge ratios thereby enabling determinations of isotopes of same element. Such estimations are important for environmental and pharmaceutical studies where different isotopes of same element can have adverse health impacts.
In summary, you have to keep in mind your present and future applications in making a choice between the two techniques . Demands of applications and skill requirements besides cost implications are key considerations that you should keep in mind before you make your choice on procurement of such highly sophisticated techniques.
Dr. Deepak Lab-training.com
Posted by Muyiwa Adebola