『Abstract
To determine the bioavailability/mobility of phosphate from aquatic
sediments chemical fractionation, involving sequential extraction
procedures, has been widely applied. Among the several methods
proposed, two different approaches have been used: the first one
is based on the use of strong acids and bases as extractants,
and the second one based on the use of complexing agents (such
as NTA and EDTA). The lack of selectivity of the extractants implies
obtaining operational defined fractions and a high dependence
of the results on the experimental conditions. Consequently, results
cannot be compared and the procedures cannot be validated. To
validate them through interlaboratory exercises, first it is necessary
that each laboratory validates the determination of phosphate
in such matrices. This paper presents the validation of phosphate
determination by spectrophotometric and inductively coupled plasma-atomic
emission spectrometric techniques in the extracts obtained applying
the Williams and Golterman procedures, as well as the BCR method
(a sequential extraction scheme designed for heavy metal distribution
studies in sediments). The measurement conditions and the matrix
effects of the reagents were studied using standard phosphate
solutions, along with the effects of the concomitant species in
sediment extracts (Ca, Na, Na2S2O4, K2S2O8). The analytical characteristics (linear range,
accuracy, precision and limits of detection and quantification)
of each technique were studied. The optimum conditions were established
and applied to study the extractable phosphate content in several
sediment samples. Different distribution patterns were obtained
when applying schemes, pointing out the need of harmonised procedures
to study phosphate partitioning in aquatic sediments.
Keywords: Sequential extraction; Phosphate; Validation; Sediments』
1. Introduction
2. Experimental
2.1. Apparatus
2.2. Reagents
2.3. Sediment samples
2.4. Procedures
2.4.1. Sequential extraction procedures
BCR method
Williams method
Golterman method
2.4.2. Total phosphorus determination
2.4.3. Determination procedures
3. Results and discussion
3.1. Effect of the extracting agents
3.1.1. ICP-AES technique
3.1.2. Spectrophotometric technique
3.1.3. Comparison of the two determination techniques
3.2. Quality parameters
3.3. Stability studies
3.4. Determination of total P
3.5. Application of extraction procedures
4. Conclusions
Acknowledgements
References