Atomic spectrometry and flow injection analysis: a synergic combination

The combination of flow-injection techniques with atomic spectrometry (flame atomic absorption and emission spectrometry and inductively-coupled plasma/atomic emission spectrometry) is reviewed, with particular reference to the more recent contributions. The considerable growth in the number of directly couple pre-concentration and matrix isolation is noted, together with the increasing number of reports of indirect methods for metals, inorganic anions and even drug molecules. Many developments are motivated by a desire to increase the performance of the spectrometry over that obtained with conventional methods of sample introduction. Conflicting statements concerning the possible benefits of reduced uptake rate, of air compensation and of peak-area measurement are examined critically. The conflicting requirements of obtaining freedom from stable-compound interferences coupled with god detection limits are discussed, as are means of obtaining the best detection limits. Modifications to nebuliser and spray-chamber design are suggested for maximising peak height (to obtain detection limits) and for working with reduced uptake rates (to reduce stable-compound interferences in flame-based spectrometries). The single well-stirred tank model is used to model nebuliser response and results are presented for the flow-injection behaviour of a Philips Scientific SP9 instrument under conditions of low flow rate which show reasonable agreement with the model. With the instrument, the best detection limits are obtained on the basis of peak-height measurements at the flow rate producing maximum signal-to-noise ratio.