Determination of lead content in medicinal plants by pre-concentration flow injection analysis-flame atomic...

Although medicinal plants are widely used throughout the world, few studies have been carried out concerning the levels of heavy metal contaminants present. Such metals are highly toxic to living organisms even in low concentrations owing to their cumulative effect. The present paper describes the the development of a pre-concentration flow injection analysis-flame atomic absorption spectrometric system to determine the lead content in medicinal plants at the ppb level.

To develop a pre-concentration flow injection analysis-flame atomic absorption spectrometric system to determine the lead content in medicinal plants at the ppb level.

A pre-concentration flow system was coupled to a flame atomic absorption spectrometer. The plant samples were analysed after nitroperchloric digestion. The proposed system was optimised by evaluating the following parameters: nature, concentration and volume of the eluent solution, elution flow rate, elution efficiency, pre-concentration flow rate and pre-concentration time.

The proposed system exhibited good performance with high precision and repeatability (RSD < or = 2.36%), excellent linearity (r = 0.9999), low sample consumption (10.5 mL per determination) and an analytical throughput of 55 samples/h. Lead concentrations ranged from 3.37 + or - 0.25 to 7.03 + or - 0.51 microg/g in dry material. This concentration interval is greater than that previously published in the literature.

The inclusion of a pre-concentration column in the flow manifold improved the sensitivity of the spectrometer. Thus, it was possible to determine the analyte at the ng/mL level in sample solutions of medicinal plants. This is a very important accomplishment, especially when the cumulative effect of heavy metals in living organisms is considered.