Identification of molecules in graphite furnace by laser ionization time-of-flight mass spectrometry: sulfur and chlorine containing compounds

Abstract

An electrothermal vaporizer (ETV) coupled to a time-of-flight mass spectrometer (TOF-MS) with laser ionization (LI) was applied to the identification of molecules from sulfur and chlorine matrices in the furnace. An interface was developed to entrain furnace vapors from the matrices under study, i.e., sulfur, sulfuric acid, magnesium sulfate, chlorides of sodium, potassium, caesium, magnesium, calcium and strontium, into the TOF-MS. These were then ionized on the TOF axis with 219, 240 and 266 nm laser radiations. The S⁺ and SO⁺ ions were mainly detected from sulfuric acid and magnesium sulfate in the furnace when ionized with a 219 nm beam. SO₂⁺ was observed with 266 nm. Mainly S⁺ and S₂⁺ were detected when sulfur was ionized with 219 and 266 nm.

The spectra obtained at 219 nm were identical to those attained at 240 nm for the chloride matrices. The MCl⁺, M₂Cl⁺, M⁺, and M₂⁺ (where M is the metal) were observed for Na, K and Cs. Various compositions of oxides (M_xO_y)⁺, M₂OCl⁺ and chlorides MCl⁺ and MCl₂⁺ were identified for Ca and Sr. Mg only produced the Mg⁺ isotopes.