Issue 10, 2001

A novel flow-through disk-based


A novel, versatile and sensitive flow-through optical fiber diffuse reflectance sensor to implement disk-based solid-phase extraction in a flow injection analysis (FIA) system is presented. Nitrite optosensing at trace levels is chosen as a model of chemistry to demonstrate its applicability. The methodology is based on on-line nitrite derivatization with Shinn reagent to form a moderately polar azo dye, whose preconcentration on to octadecyl covalently bonded silica gel particles tightly bound to an inert matrix (C18 disk) is continuously monitored using a plug-in diode-array spectrophotometer. After the analytical signal has been recorded, fast sensor regeneration is achieved with a methanolic eluent, rendering the system ready for the next extraction. Selection of the solid disk support and the suitable flow-through cell configuration to reduce back-pressure effects are discussed in detail. By matching the illumination and retention zones, concentrations of nitrite as low as 1 ng ml−1 are easily determined using 2.5 ml of sample. A detection limit (3σblank) of 0.1 ng ml−1 of nitrite, repeatability and reproducibility better than 3.2%, an analytical throughput of 11 h−1 and an enrichment factor of 140 are the figures of merit of the proposed optrode. The utility of the flow-through optosensing system, wherein minimization of additive matrix interferences is feasible, was testified by the satisfactory results obtained in its application to tap, ground, harbor and aquarium water samples.

Article information

Article type
23 May 2001
11 Jul 2001
First published
19 Sep 2001

Analyst, 2001,126, 1740-1746

A novel flow-through disk-based solid-phase extraction diffuse reflectance optrode. Application to preconcentration and determination of trace levels of nitrite

M. Miró, W. Frenzel, J. M. Estela and V. Cerdà, Analyst, 2001, 126, 1740 DOI: 10.1039/B104553A

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