New approach to sequential injection analysis: using the sample as carrier

Abstract

A new way of implementing sequential injection analysis involving the use of the sample as a carrier is proposed. These systems are especially suitable for constructing continuous monitoring set-ups with no restrictions regarding the amount of sample which can be processed. A new standard addition methodology was used to calibrate the proposed system. The methodology was applied to the determination of Fe^II with o- phenanthroline (a reaction which involves a single reagent) and that of phosphorus by formation of a blue heteropolyacid (a reaction involving two reagents). The analysis rate is 8 min per sample (3 standard additions). The manifold design together with an adequate programme of aspiration–impulsion movements avoids the memory effects between samples. Determination of Fe^II is linear between 0.25 and 6 mg l^–1 Fe^II. In the analysis of a sample containing 2.3 mg l^–1 Fe^II (n = 10) a relative standard deviation of 1.7% has been obtained. The detection limit (3s) is 0.06 mg l^–1 Fe^II and the determination limit (10s) 0.2 mg l^–1 Fe^II. Determination of P is linear between 0.1 and 1 mg l^–1 P and in the analysis of a sample containing 0.75 mg l^–1 P (n = 10) a relative standard deviation of 4.1% has been obtained. The detection limit is 0.02 mg l^–1 P and the determination limit 0.1 mg l^–1. Both methods have been applied to the determination of Fe and P in spiked waters. The use of the methodology based on the standard addition has been evaluated in the case of P determination in order to eliminate interferences of the multiplicative type.

References

1. J. Ruzicka and G. D. Marshall, Anal. Chim. Acta, 1990, 237, 329.
2. J. Nyman and A. Ivaska, Anal. Chim. Acta, 1995, 306, 286.
3. T. Gubeli, G. D. Christian and J. Ruzicka, Anal. Chem., 1991, 63, 2407.
4. A. Cladera, C. Tomàs, E. Gómez, J. M. Estela and V. Cerdà, Anal. Chim. Acta, 1995, 302, 297.
5. J. Ruzicka and E. H. Hansen, Flow Injection Analysis, Wiley, New York, 2nd edn., 1988, p. 68.
6. Z. Fang, J. H. Harris, J. Ruzicka and E. H. Hansen, Anal. Chem., 1985, 57, 1457.
7. R. E. Stanller, Anal. Chem., 1983, 55, 1205.