If we want to live healthy lives, we need to know the nature and content of undesirable chemical elements in our environment. If a municipal council wants to clean up a piece of land to develop a new suburb, it needs to know whether heavy metals or toxic substances such as arsenic remain in the soil from the previous use of the land. Likewise, the managers of drinking water sources, surface water bodies and fishing areas need to know about the quality of their water, to determine whether it contains excessive levels of undesirable substances that will have to be removed. And in order for air quality to be considered good, the trace element content in the solid particles floating in the air must not be too high.
If you are looking for more details, kindly visit our website.
Outside of the environmental field, there are other places where it is helpful to be able to identify and quantify the elements that are present – such as establishing the concentration of metal in lubricating oil to determine how quickly an engine will wear out, or the concentration of fertilisers in agricultural soil to determine whether additional fertiliser is required. Flow meters and controllers also play a major role here. As an industry specialist in the analytical market, allow me to explain how it all works.
The fundamental principle of inductively coupled plasma mass spectrometry (ICP-MS), which gives the technique its unequalled isotopic selectivity and sensitivity, also unfortunately contributes to some of its weaknesses. The fact that the sample “flows into” the spectrometer and is not “passed by it” at right angles, such as flame AA and radial inductively coupled plasma optical emission spectroscopy (ICP-OES), means that the potential for thermal problems, corrosion, chemical attack, blockage, matrix deposits, and drift is much higher than with the other atomic spectrometry (AS) techniques. However, being fully aware of this fact and carrying out regular inspection of instrumental components can reduce and sometimes eliminate many of these potential problem areas. There is no question that a laboratory which initiates a routine maintenance schedule stands a much better chance of having an instrument ready and available for analysis whenever it is needed, compared to a laboratory that basically ignores these issues and assumes the instrument will look after itself.
Let us now look at the areas of the instrument that require inspection and maintenance on a routine basis include the following components:
The majority of imprecision problems in ICP-MS arise due the potential of sample matrix depositing itself either in the nebulizer tips, the sample injector of the torch and/or the interface cones. In this article, we will focus on the sample introduction system, and in particular how to maximize the efficiency of the peristaltic pump tubing, nebulizer and spray chamber to deliver the sample aerosol to the plasma torch free of problems.
Robert (Rob) Thomas has worked in the field of trace element analysis for over 40 years, including 24 years for an ICP-MS manufacturer and 17 years as a principal of his own consulting company, Scientific Solutions (www.scientificsolutions1.com) He has served on the American Chemical Society (ACS) Reagent Chemical Committee for the past 17 years as leader of the elemental impurities task force where he has worked closely with the United States Pharmacopeia (USP) to align heavy metal testing procedures in reagent chemicals with those of pharmaceutical materials.
He has authored almost 100 publications on the fundamental principles and applications of plasma spectrochemical and sample preparation techniques. In addition, he has written three textbooks on trace element analysis, including a new book, which focuses on the new global directives on elemental impurities in pharmaceutical and related materials (1). He is currently editor and frequent contributor to the Atomic Perspectives Column in Spectroscopy Magazine. He has an advanced degree in Analytical Chemistry from the University of Wales in the UK and is a Fellow of the Royal Society of Chemistry (FRSC, and a Chartered Chemist (CChem).
Goto Naen to know more.
1. Robert. J. Thomas, Measuring Elemental Impurities in Pharmaceuticals: A Practical Guide, CRC Press, Boca Raton, FL, ISBN13:978-1-138- ()
The sample is pumped at about 1 mL/min into the nebulizer. The constant motion and pressure of the pump rollers on the pump tubing, ensures a continuous flow of liquid into the nebulizer. However, over time, this constant pressure of the rollers on the pump tubing has the tendency to stretch it, which changes its internal diameter, and therefore, the amount of sample being delivered to the nebulizer.
Therefore, the condition of the pump tubing should be examined every few days, particularly if the laboratory has a high sample workload or if extremely corrosive solutions are being analyzed. The peristaltic pump tubing is probably one of the most neglected areas, so it is absolutely essential that it be a part of a routine maintenance schedule. Here are some suggested tips to reduce pump tubing related problems:
The larger diameter of the liquid capillary and longer distance between the liquid and gas tips of the cross-flow design make it far more tolerant to dissolved solids and suspended particles in the sample than the concentric design. On the other hand, aerosol generation of a cross-flow nebulizer is far less efficient than a concentric nebulizer, and therefore it produces droplets of less optimum size than that required for the ionization process. As a result, concentric nebulizers generally produce higher sensitivity and slightly better precision than the cross-flow design, but are more prone to clogging.
So, the choice of which nebulizer to use is usually based on the types of samples being aspirated and the data quality objectives of the analysis. Whichever type is being used, attention should be paid to the tip of the nebulizer to ensure it is not getting blocked. Sometimes, microscopic particles can build up on the tip of the nebulizer without the operator noticing, which, over time, can cause a loss of sensitivity, imprecision, and poor long-term stability. In addition, O-rings and the sample capillary can be affected by the corrosive solutions being aspirated, which can also degrade performance. For these reasons, the nebulizer should always be a part of the regular maintenance schedule. Some of the most common things to check include:
The digital thermoelectric flow meter described earlier is also very useful to diagnose problems with the nebulizer, even if a self-aspirating nebulizer is being used. By placing the device in-line, you always know what your sample uptake is and can take immediate corrective action if there is any change. You can also record your sample flow in order to check that you are using the same flow from day to day. If the flow meter indicates a blocked nebulizer tip, there are also nebulizer-cleaning devices available. Traditionally if particulate matter from the sample lodges itself in the end of the nebulizer, cleaning wires or ultrasonic baths were the only way to remove the obstruction, which often resulted in permanent damage. These new cleaning devices are designed to efficiently deliver a pressurized cleanser through the nebulizer capillary to safely dislodge particle build-up and thoroughly clean the nebulizer, without fear of damage.
Want more information on ICP Plasma Cleaner? Feel free to contact us.