Implementation of chemiluminescence detection in the multisyringe flow injection technique

Abstract

The feasibility of multisyringe flow injection analysis (MSFIA) to perform liquid phase chemiluminescence (CL) analysis of trace metals using a newly developed laboratory-made luminometer is demonstrated. The noteworthy features of both the flow detector and the automated set-up are their robustness, operational simplicity and ease of construction and design. The CL reaction between 3-aminophthalhydrazide (luminol) and an oxidant species catalyzed by traces of metals in alkaline medium was chosen as a model to assess the potentialities and applicability of MSFIA with multicommutation for CL reactions. The methodology is based on merging the sample segment with plugs of an oxidant (hydrogen peroxide) and the luminol solution in alkaline medium at a total flow rate as high as 25 ml min −1 through a four-way junction point placed as close as possible to the photosensor module. Under the optimum conditions, a linear log–log regression between light emission intensity and catalyst concentration was found over the range from 15 ng l −1 to 5 μg l −1 for Co(II), although all experimental data better fitted a quadratic calibration graph. An injection throughput as high as 180 h −1 for 200 μl samples, a repeatability of 1.0% ( n=8) at the 1 ng ml −1 level and a 3 σ detection limit of 15 ng l −1 were the analytical features of the developed analyzer for determination of ultratrace levels of cobalt. The developed CL–MSFIA method was successfully applied to degradation studies of Vitamin B 12 (cyanocobalamin) at low acid concentrations based upon the release of cobalt from the tetrapyrrole complex.