Measurement of Lithium
in Sea Water

The effect of potential interference from other constituents of sea water was studied, including sodium, chloride and potassium.    

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It was found that pre-concentration of the sea water was not necessary prior to analysis. A filtration of the sample was only necessary if sample contained suspended material.   

 

Introduction

The effect of potential interferences from other constituents of sea water was studied, including sodium, chloride and potassium and the effects were considered negligible in the analysis. Preconcentration of the sample was not necessary prior to analysis. Filtration of the sample was recommended due to the presence of microscopic particulate matter present such as seaweed and plankton.

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Procedure

Deionised distilled water is used throughout. Glassware is acid cleaned in nitric acid and rinsed thoroughly in deionised water prior to use to avoid contamination.

 

A single point calibration should be carried out to estimate the concentration of Lithium. From this estimate, standard solutions should be made to cover a range to give a better determination of the samples lithium concentration.

 

The sample was filtered into a 100ml volumetric flask using a fine grade filter paper and funnel. The sample did not require any further pre-treatment and was ready for analysis.

 

Further considerations which could be carried out is measuring the weight of the filter paper prior to filtration, drying it post filtration and measuring the additional materials filtered out by reweighing the dry filter paper. This can then be wet ashed with a strong acid and a high temperature oven, then diluted into a 100ml volumetric flask ready for analysis. This would give a reading of available lithium in sea water as well as a “trapped” lithium reading.

 

Preparation of Standard Graph

Set the flame photometer in accordance to MultiPoint/Single Ion Calibration found on page 24 of the BWB Technologies Installation and Operation Manual, to measure potassium emission. Nebulize the working standard solutions and adjust the controls until steady zero and maximum readings are obtained. Nebulize the intermediate working standard solutions and construct a graph relating raw emission data (known as RAW in  BWB the flame photometer) to concentration of all the standard solutions.