Volatile germanium tetrachloride for sample introduction and germanium determination by inductively coupled plasma atomic emission spectroscopy

The chemical vaporization of germanium(IV) with chloride ions is described as a means of introducing gaseous germanium into an inductively coupled pla sma atomic emission spectrometer for the determination of Ge. The vapour is produced in a discontinuous mode by injection of 200 mul of aqueous soluti on of Ge-IV and 380 mul of 10% m/v sodium chloride solution into 385 mul of concentrated sulfuric acid. The gaseous analyte is introduced into the pla sma torch by a flow (1.2 1 min(-1)) of Ar carrier gas. The analytical metho d was studied by experimental design. The main effects and interactive effe cts of five experimental variables on the germanium atomic emission signal were evaluated by a two-level fractional factorial design. After the experi mental study the three most influential factors (sulfuric acid volume, sodi um chloride concentration and sample volume) were optimized by the modified simplex method. Under the optimized conditions, germanium could be determi ned by measuring its atomic emission at 209.426 nm produced in an inductive ly coupled plasma. The analytical method shows an absolute detection limit (3 sigma) of 0.6 ng for the injection of 200 mul of sample solution. The pr ecision was 3.2%, expressed as the relative standard deviation, when seven replicates of 100 ng (200 mul of a 0.5 mug ml(-1)) solution were measured. The interference effects of alkali, alkaline earth, metallic and metalloid elements were studied; anions were also considered. A high selectivity of t he reaction was observed and only Pb and alkaline earth elements interfered when present in amounts 50-fold greater than the Ge-IV concentration. The method was applied to determine germanium in coal and lignite samples and t he results obtained were validated by a standard method.