| Article ID | Journal | Published Year | Pages | File Type |
|---|---|---|---|---|
| 1243424 | Talanta | 2015 | 7 Pages |
•Paired emitter detector diode as miniaturized fluorometric detector for phosphate.•Sufficient sensitivity of FPEDD for detection of phosphate in soil leachates.•Hybrid flow system for reliable dynamic bioaccessibility tests of phosphate in soils.•On-line analysis of extracts without delay after dynamic extraction.•On-line manipulation of sample/extracts using the secondary flow injection setup.
An integrated Sequential Injection (SI)/Flow Injection (FI) system furnished with a miniaturized LED-based fluorometric detector is presented in this work for expedient bioaccessibility tests of orthophosphate in soils. Equipped with a microcolumn of conical shape containing 50 mg of soil, the hybrid flow system was resorted to on-line dynamic leaching and real-time quantification of pools of mobilizable orthophosphate using a bi-directional syringe pump and multiposition valve. The flexibility of the flow manifold was harnessed to explore both bi-directional and uni-directional flow extraction modes with the added degree of freedom of on-line dilution of extracts whenever needed. Bioaccessible orthophosphate was split in three fractions, the so-called NH4Cl fraction containing labile exchangeable phosphates, the alkaline fraction with Fe and Al-bound phosphates and the acidic fraction containing Ca-bound phosphates.The prevailing molybdenum blue photometric detection method is replaced by spectrofluorometric detection based on the ion pair formation between the phosphomolybdate heteropolyacid and rhodamine B with the subsequent quenching of the dye fluorescence. The dedicated optoelectronic detector was integrated in a secondary FI manifold and operated according to the fluorometric paired emitter–detector diode (FPEDD) principle involving two light emitting diodes as fluorescence inductors and one as detector of LED-induced fluorescence.Demonstrated with the analysis of a standard reference material (SRM 2711) and a real agricultural soil, the developed FI/SI fractionation system with FPEDD detection is proven reliable against the standard molybdenum blue method (p>0.05), and useful for investigation of the leaching kinetics of orthophosphate in bioaccessibility tests through in-line recording of the extraction profiles.
Graphical abstractAutomatic bioaccessibility tests of orthophosphate in soils using dynamic sequential extraction combined with a miniaturized fluorometric detector.Figure optionsDownload full-size imageDownload as PowerPoint slide
