Uses of silica cells for the static cold vapour atomic-absorption determination of mercury without background correction
A static cold vapour procedure for the determination of mercury by atomic-absorption spectrometry using a silica cell as the reduction vessel and for the absorbance measurement is described. Background absorption, found to be caused by the reagents used and not by water itself, was reduced and the precision improved when a silanised cell was used so that background correction was unnecessary. The peak absorbance exhibited a marked decline for hydrochloric acid at concentrations above 0.5 M and for nitric acid at concentrations above 2 M. Antimony and bromide interfered seriously and iodide very seriously with the mercury determination. The calibration graph obtained for mercury(II) in 4.5 M sulphuric acid using a silanised 4-cm cell was linear from 0 to 20 ng ml–1; the sensitivity and detection limit were 0.13 and 0.27 ng ml–1, respectively. A clean non-silanised 4-cm cell could also be used when the sample contained 10%V/V of ethanol with slightly reduced sensitivity. The relative standard deviation was found to be 3.2% and 4.7% at the 10 ng ml–1 of mercury level for the silanised and non-silanised 4-cm cells, respectively. The accuracy of the proposed method was checked by determining the mercury content in standard reference materials and fish samples.