Ester Generation for the Determination of Ultratrace Amounts of Boron in Volatile High-purity Process Chemicals by Inductively Coupled Plasma Mass Spectrometry

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Abstract
A method for the determination of boron at nanogram and sub-nanogram levels in volatile high-purity process chemicals, e.g. , hydrofluoric acid, with ICP-quadrupole-MS (ICP-QMS) is described. An evaporation of the matrix allows the separation and preconcentration of boron. When applying mannitol as a trace collector the sample can be evaporated to dryness without loss of analyte. To determine ultratrace amounts of boron, a miniaturized methyl borate ester generation system is combined with an ICP-QMS instrument. Methyl borate is generated by adding methanol and concentrated sulfuric acid to the dry residue. After a reaction time of 15 s, an argon carrier gas flow is passed through the esterification vessel and the volatile product is transferred directly into the plasma. Limits of detection of 50 pg can be achieved. A preliminary test of ICP-sector field-MS as an alternative method is also presented.