In vivo sample uptake and on-line measurements of cobalt in whole blood by microwave-assisted mineralization and flow injection electrothermal atomic absorption spectrometry

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Abstract
An on-line automated microwave-assisted mineralization and flow injection system was developed for the determination of cobalt in whole blood with in vivo sample uptake by electrothermal atomic absorption spectrometry. The samples were drawn and at the same time pumped directly from the vein of a patient's forearm to a timed injector, which is automatically controlled to inject the sample–nitric acid–anticoagulant mixture into the carrier stream. Volumes (20 µl) of the mineralized samples, collected in a capillary of a sampling arm assembly, were introduced by means of positive displacement with air through a time-based solenoid injector (TBSI) into the graphite tube atomizer. The spectrometer autosampler, used for the introduction of 10 µl of the chemical modifier, magnesium nitrate, and the furnace programme were re-programmed to synchronize with the operation of the flow system. The linear range was from 0 to 50 µg l–1 of cobalt, achieving a precision of 2.6 and 3.1% for 10 replicate analyses of a 5 µg l–1 cobalt standard solution and a certified sample, respectively, with a detection limit of 0.3 µg l–1. The agreement between the observed and certified values obtained from Seronorm Whole Blood Standard Reference Materials was good. The results obtained by using an in-batch procedure were found to linearly increase by 5% during the time interval between sample collection and analysis for the first hour; after this time the results for cobalt levelled off and were then in close agreement with those obtained by the on-line procedure proposed here.

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