David Vassallo

Iron pentacarbonyl determination in carbon monoxide

Abstract Iron pentacarbonyl, Fe(CO) 5 , was previously employed to calibrate the sealed inductively coupled plasma (SICP) for Fe in a 50% chlorine discharge. The same technique is used to determine Fe as Fe(CO) 5 , one of the most important metallic compound impurities present, in carbon monoxide cylinders. Iron concentrations in various CO cylinders were determined directly by SICP in 30% (v/v) CO. Operating parameters including incident power and maximum tolerable CO and Cl 2 concentrations in the discharge were optimized. The detection limit for Fe(CO) 5 in CO was 0.18 μl l −1 (172 ng absolute). Statistically similar results were obtained when Fe(CO) 5 content was determined by FTIR and SICP-AES. Two- and sevenfold increases in Fe(CO) 5 concentrations were observed over a 1-year period in two different carbon steel cylinders containing CO.

The synthesis of iron and nickel carbonyl as calibration materials for spectroscopic systems

Abstract Iron pentacarbonyl, Fe(CO) 5 , was employed in a number of spectroscopic systems as the calibration source for Fe during the analysis of toxic and reactive gases such as anhydrous hydrogen chloride and chlorine. Although nickel tetracarbonyl, Ni(CO) 4 , has similar properties to Fe(CO) 5 , its use is limited owing to the unavailability of low ppm (v/v) standard gas mixtures. Gas mixtures of these two compounds were produced by synthesizing Fe(CO) 5 and Ni(CO) 4 and diluting them with Ar or N 2 as required. Low ppm (v/v) gas mixtures of both metal carbonyls were stable for at least 20 days. The fluctuations in concentration were negligible. The %R.S.D.’s were 2.22 and 0.59 for Fe(CO) 5 and Ni(CO) 4 , respectively. The other step in synthesizing these compounds as standard materials was to determine their concentrations. Concentrated nitric acid (70% v/v), was employed to absorb the carbonyls. The solutions were subsequently analyzed with a graphite furnace atomic absorption spectrometer (GFAAS). When compared against a reference gas mixture, the recovery for Fe(CO) 5 was 98%.

The behavior of moisture in high pressure inert cylinder gases

Abstract The moisture concentration inside cylinder gases changes according to the cylinder pressure: at high cylinder pressures, the moisture concentration is undetectable, while the moisture level increases as the cylinder pressure decreases. This phenomenon is traditionally explained by the dilution theory, which predicts a linear relationship between cylinder pressure and moisture concentration. However, experimentally this phenomenon has never been observed. The focus of this talk lies upon the development of a theoretical model describing the moisture interaction with a solid surface at various high cylinder pressures.