Increasing the Productivity of ICP-OES Soil and Plant Analysis By Selecting the Optimum Sample Introduction System.

Modern ICP-OES analytical instrumentation is widely used by Agricultural Soil and Plant Laboratories due to it’s high productivity and reliability. At the same time analysis of the agricultural soil extracts by ICP-OES is often challenged by difficult and complicated chemical nature of the employed extractants - Mehlich 3, ammonium chloride or ammonium acetate , as well as by particulate content in the samples.

Analysis of plant digests also requires reaching low detection limits. That is why choosing the optimum sample introduction system to utilize the high analytical potential of today’s ICP spectrometers still remains a very critical task.

The most common concentric type nebulizers offer good sensitivity and detection limits, but suffer from frequent clogging in presence of even tiny particles. In addition concentric nebulizers require daily maintenance when running high salt matrices. In order to increase the productivity ICP spectrometers are connected to a different type of Fast Valve systems. The commonly used by the manufacturers sample line adapters with very small internal diameter of 0.25 mm are frequently getting clogged. This along with the time consuming maintenance needed for concentric Nebulizers significantly decreases the productivity of the ICP-OES analysis .

The alternative nonconcentric Nebulizers are either made from an expensive and resistant to Hydrofluoric Acid plastic material which has no value for agricultural soil analysis, or do not offer enough sensitivity required for plant analysis.

That is why quite often Agricultural Laboratories are forced to use two different Nebulizer types for the ICP-OES analysis of Soil extracts and Plant digests . Applying more sensitive concentric Nebulizers for Plant digests requires additional and time consuming filtration step to eleminate silica partuculates that cause clogging. This reduces the productivity and increases the cost of analysis.

To effectively address these problems sample introduction system with nonconcentric Nebulizer types - OptiMist ^® -Soil and OptiSolids XL ^TM was applied. The design approach includes a simple concept: employing larger 0.50 mm ID sample line adapter for Fast Valve in combination with unrestricted sample passage internal diameter of 0.50 mm for OptiMist ^® -Soil and 1.0 mm for OptiSolids XL ^TM .

Performance data for the most challenging Mehlich 3 agricultural soil extracts and plant digests will be presented.