Determination of metals in Lime and Limestone using borate fusion for ICP-OES

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(Free-Press-Release.com) August 26, 2011 -- Authors: Janice Pitre, C.S. Claisse, Inc.; Melanie Bedard . C.S. Claisse Inc. ; Aaron Hineman, PerkinElmer, Inc.

Introduction

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Determination of metals in Lime and Limestone using borate fusion for ICP-OES

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Limestone (CaCO3) is an inorganic mineral found in abundance all over the world. The determination of metals in lime samples by inductively coupled plasma combined with optical emission spectrometry (ICP-OES) is not difficult to perform in itself but will require multiple steps if approached with acid digestions in mind. A single method that could include all raw, finished and waste products involved in lime production would be very appealing to many because of increased productivity factors.

This article describes the automated borate fusion method designed by Claisse to obtain the full dissolution of common lime products such as limestone, dolomite, calcium hydroxide and residues, without the need of harsh acids or extensive sample dissolution for ICP-OES determination.

Experimental

In this project, fusions were performed using a Claisse M4 Fluxer. The M4 is a 3 burner Fluxer which provides quick, safe and complete dissolution for the samples of interest. It was specifically designed to offer inter-burner flame stability for the best repeatability and consistency. The software allows full control over different operating parameters such as speed of agitation, temperature, duration of each step and others. The adjustable parameters allow the user to optimize the fusion process in order to obtain complete dissolution of the samples in the quickest time possible.

In a platinum-gold crucible, the ground sample was mixed with Ammonium Nitrate 66.67% lithium tetraborate/32.83% lithium metaborate/0.5% lithium bromide flux (67/33/LiBr). The crucible containing the mixture was placed on a Claisse M4 Fluxer, fused for 6 minutes, then automatically poured into a Teflon Beaker containing about 90 mL of HNO3/HCl (10%v/v) solution which was, in turn, automatically magnetically agitated for 5 minutes. The measurements were performed using the PerkinElmer Optima 7300 DV ICP-OES instrument.

Results and Discussion

The following criteria were taken into consideration in selecting the wavelength: (a) the freedom from spectral interferences; (b) the different sensitivities and expected concentration in the samples. Observed interferences were compensated for by modifying the processing parameters (e.g. adjusting the background correction points, applying multi-component spectral fittings (MSF) or inter-elemental corrections (IEC)).

Method detection limits (MDLs) were based on ten replicate measurements of a series of low concentration or diluted sample solutions. The MDL was calculated by multiplying the standard deviation of the ten replicate measurements by 3 and the correction factor. The accuracy and precision of the method was evaluated. The accuracy was determined by calculating the elemental recovery of certified reference materials (CRMs). The precision was determined by preparing and measuring 10 replicates of the various CRMs. The accuracy and precision obtained demonstrates that the developed method performs very well. Pre-fusion spikes were performed on samples and CRMs to monitor the recovery of the elements and further validate the method.

Conclusion

Borate fusions combined with the simultaneous ICP-OES have the analytical capabilities to perform the analysis of limestone and lime products with good accuracy (average of 102%), precision (average of plus or minus 2%), recovery (ranging from 86% to 100%), analysis speed and robustness and fulfills the requirements normally set for the analysis of high matrix samples such as fusion samples. The borate fusion approach to dissolution of lime products is an excellent alternative as its success resides in the simplicity of the method; its speed (complete sample dissolution in less than 12 minutes); automation and the absence of harsh acids.

More information can be found online at http://www.claisse.com

Automatic fusion fluxer     borate fusion     claisse     Claisse M4 Fluxer     limestone     sample preparation by fusion     xrf analysis