Graphite furnace : capacitively coupled plasma - atomic spectrometry and inductively coupled plasma - mass spectrometry for the determination of silica and trace metals in water
Abstract of thesis entitled
GRAPHITE FURNACE - CAPACITIVELY COUPLED PLASMA -ATOMIC SPECTROMETRY AND INDUCTIVELY COUPLED PLASMA -MASS SPECTROMETRY FOR THE DETERMINATION OF SILICA AND
TRACE METALS IN WATER
Yu Tung Man
for the degree of Master of Philosophy
at The University of Hong Kong
in December 2002
A newly-developed Graphite Furnace - Capacitively Coupled Plasma -Atomic Absorption Spectrometry (GF-CCP-AAS) method was used for the determination of trace silica in aqueous media. The sensitivity for trace silica determination was improved using the GF-CCP-AAS method when compared with traditional method, such as Graphite Furnace - Atomic Absorption Spectrometry (GF-AAS). An Inductively Coupled Plasma - Mass Spectrometry (ICP-MS) method was also used to determine trace elements in drinking water and mineral water samples available in Hong Kong.
The GF-CCP-AAS method was developed to meet the demand in the determination of silica for type E-3 and type E-4 high-purity water. The GF-CCP-AES (or FAPES) method with single sample injection was also developed to meet the demand in the determination of silica for type E-2 high-purity water. The detection limits for using the GF-CCP-AAS and FAPES methods are 7.2 ng/L and 3.5 |xg/L respectively. The GF-CCP-AAS method can overcome chemical interference which occurs in conventional GF-AAS methods such as matrixes containing sodium chloride, sodium orthophosphate and sodium sulfate but not magnesium sulfate due to the high temperature as the result of using an CCP during atomization.
The presence of plasma in the atomization step in GF-CCP-AAS was found to affect the silicon absorption signal. The effects of the solution volume, the peak shape, and the.plasma background correction on the absorption signal of silicon using GF-CCP-AAS were studied. Procedures using the fast-drying pre-concentration step were developed, coupled with GF-AAS, GF-CCP-AAS and FAPES. The use of fast-drying pre-concentration GF-CCP-AAS and fast-drying pre-concentration FAPES was found to satisfy the requirements of total silica content in type E-1, type E-1.1 and type E-1.2 high-purity water. The detection limits of GF-CCP-AAS and FAPES coupled with pre-concentration were 0.46 p,g/L and 0.3 pg/L respectively.
The extent of the destruction of the quartz and amorphous silica by the plasma was found to be dependent on the size of particles. Amorphous silica with particle size less than 2.5 microns is more completely destroyed by the plasma while quartz silica with particle size greater than 2.5 microns is more favorably
destroyed by the plasma.
An ICP-MS method was developed for the determination of elements of concern as listed by the World Health Organization in drinking and mineral water. Different sources of mineral water can be distinguished using isotope ratio analysis under favourable conditions. Magnesium was shown to be the major chemical interference in ICP-MS analysis. Cadmium, antimony, copper nickel, chromium, manganese and uranium were found to show signal suppression in solutions containing magnesium concentrations higher than 30 mg/L.
School:The University of Hong Kong
School Location:China - Hong Kong SAR
Source Type:Master's Thesis
Keywords:silicon spectra drinking water furnace atomic absorption spectroscopy inductively coupled plasma emission spectrometry
Date of Publication:01/01/2003