Direct determination of Zn in individual Daphnia magna specimens by means of solid sampling high-resolution continuum source graphite furnace atomic absorption spectrometry

Abstract

In this work, the capabilities of solid sampling high-resolution continuum source graphite furnace atomic absorption spectrometry (GFAAS) for the direct determination of the Zn body burden in individual specimens of Daphnia magna (small aquatic invertebrates of approx. 2 mm length that are widely used in ecotoxicological research) were investigated. It was concluded that this technique offers interesting features for this type of application, permitting the fast (approx. 2 min for the measurement of a single sample) and practically contamination-free analysis of these invertebrates, as the only preparation required is drying. Moreover, one of the traditional disadvantages of line source-GFAAS, the narrow linear range achieved using a particular set of experimental conditions, can be overcome with this technique by the judicious selection of the detector pixels used for signal quantification, such that the linear range can be extended simply by reprocessing the data, without the need to carry out any additional measurement. This feature is particularly interesting for this application, since every Daphnia magna specimen can be monitored only once, and thus, there is no possibility to alter the conditions and repeat the analysis for samples displaying a Zn content outside the linear range. In this case, the use of central and/or side pixels permits achieving a working range between 5 and 400 ng for the 307.590 nm Zn line, which is fit-for-purpose. Analysis of two biological certified reference materials (SRM 1549 Non-fat milk powder and SRM 1577b Bovine liver) was also investigated, and accuracy could be demonstrated when carrying out the calibration versus aqueous standard solutions.