『Abstract
A field filtration method for the concentration and separation
of suspended particulate matter (SPM) from freshwater systems
and the subsequent determination of minor, trace and ultra trace
elements (As, Ba, Be, Cd, Co, Cr, Cs, Cu, Ga, Hf, Mo, Nb, Ni,
Pb, Rb, Sb, Sc, Sn, Sr, Ta, Th, Tl, U, V, W, Zn and Zr) is validated
with respect to detection limits, precision and bias. The validation
comprises the whole procedure including filtration, sample digestion
and instrumental analysis. The method includes two digestion procedures
(microwave acid digestion and alkali fusion) in combination with
inductively coupled plasma atomic emission spectrometry (ICP-AES)
and inductively coupled plasma quadrupole mass spectrometry (ICP-QMS).
Total concentrations of these 27 trace and minor elements have
been determined in suspended particulate matter (SPM) from lake
and river water with low levels of suspended solids (＜2 mg L-1
DW), and a wide range of element concentrations. The precision
of the method including filtration, digestion and instrumental
determination ranges between 8％ and 18％RSD for most elements on
a dry weight basis. Higher recovery after acid digestion is found
for some elements, probably because of volatilization or retention
losses in the fusion procedure. Other elements show higher recovery
after fusion, which is explained by more efficient decomposition
of refractory mineral phases relative to the non-total acid digestion.
Non-detectable concentrations of some elements are reported due
to small differences between blank filter levels and the amounts
of elements present on the filters after sampling. The method
limits of detection ranges between 0.7 ng and 2.65μg, as estimated
from the blank filter samples. These detection limits are 10-550
times higher compared to the corresponding instrumental limits
of detection. The accuracy and bias of the overall analytical
procedure was assessed from replicate analysis of certified reference
materials. A critical evaluation of the instrumental capabilities
of the ICP-QMS instrumentation in comparison with a double focusing
sector field plasma mass spectrometry technique (ICP-SFMS) is
also included. It was found that a modified microwave acid digestion
procedure in combination with ICP-SFMS could replace ICP-AES determinations
and fusion digestions for most of the investigated elements. Guidelines
and limitations for this time- and labour- efficient procedure,
offering accurate results for the majority of elements studied
are discussed.』
1. Introduction
2. Sampling sites
3. Experimental
3.1. Sample collection and handling procedures
3.2. Instrumentation and analytical procedure
4. Results and discussion
4.1. Reagent blanks and blank filter levels compared to instrumental
LODs
4.2. Sampling of SPM from natural water systems - amounts of
elements collected
4.3. Comparison of recovery of individual elements between microwave
and fusion dissolutions
4.4. Bias
4.5. Uncertainty introduced in normalization of SPM data
4.6. Analytical performance of ICP-SFMS in comparison with ICP-QMS
and ICP-AES
4.7. Analytical capabilities of a modified microwave digestion
procedure
5. Conclusions
Acknowledgements
References