Beryllium spectrophotometric determination

Bahrain, M., T. Madrakian, E. Bozorgzadeh, and A. Afkhami. 2007. Micelle-mediated extraction for simultaneous spectrophotometric determination of aluminum and beryllium using mean centering of ratio spectra. Talanta 72 408-414. 

Discussion. Minute amounts of beryllium may be readily determined spectrophotometrically by reaction under alkaline conditions with 4-nitrobenzeneazo-orcinol. The reagent is yellow in a basic medium in the presence of beryllium the colour changes to reddish-brown. The zone of optimum alkalinity is rather critical and narrow buffering with boric acid increases the reproducibility. Aluminium, up to about 240 mg per 25 mL, has little influence provided an excess of 1 mole of sodium hydroxide is added for each mole of aluminium present. Other elements which might interfere are removed by preliminary treatment with sodium hydroxide solution, but the possible co-precipitation of beryllium must be considered. Zinc interferes very slightly but can be removed by precipitation as sulphide. Copper interferes seriously, even in such small amounts as are soluble in sodium hydroxide solution. The interference of small amounts of copper, nickel, iron and calcium can be prevented by complexing with EDTA and triethanolamine. 

Spectrophotometric and fluorometric reagents, once used extensively for determination of beryllium (26,27), are seldom employed. Reviews of beryllium analysis are available (15—17,24—30). 

A large number of spectrophotometric methods for determining beryllium are based on azo reagents. Beryllon II (formula 9.1) forms a blue complex with beryllium at pH 12-13 [7,30,39,40] the molar absorptivity e = 1.2-10 at 630 nm. 

Fluorometric methods for the determination of beryllium are based on measurement of the intensity of the fluorescence being given by its compounds with certain organic compounds. The sensitivity of individual fluorometric methods is comparable to that of spectroscopic methods and is much higher than that of spec-trophotometric methods. Fluorometric methods also are commonly more selective than spectrophotometric methods [17]. 

---