Graeme J. Gardner

Electrospray interfacing for the coupling of ion-exchange and ion-paring chromatography to mass spectrometry☆

Abstract Electrospray was evaluated as an interface for coupling ion-exchange and ion-pairing chromatography to mass spectrometry. Effective separation and good sensitivity were demonstrated for a liquid flowrate as high as 50 μl/min and a matrix ion concentration as high as 10 mM. Minimum detectable amounts were estimated to be five to ten times poorer than those obtained in the absence of ion-exchange buffers or ion-pairing reagents. The minimum detectable amount for arsenobetaine after a dynamic ion-exchange separation was estimated to be about 20 pg.

Photochemical alkylation of inorganic arsenic

Volatile arsenic species generated by UV irradiation of aqueous solutions of arsenite in low molecular weight (LMW) carboxylic acid media (formic, acetic, propionic and butyric) were identified using ICP-TOF-MS and GC-MS.Cryogenic trapping-GC-MS reveals that inorganic arsenite can be alkylated to yield AsH 3 in the presence of formic acid, trimethylarsine in acetic acid, triethylarsine in propionic acid and tripropylarsine in butyric acid solutions. Mixed ligand arsenic species such as methylarsine, dimethylarsine, dimethylethylarsine and diethylmethylarsine are also formed when a mixture of acids is used. Using 0.05 mg l - 1 As(III) as the test solution in 3.1 M acetic acid, a methylation efficiency of approximately 75% was achieved.

UV photochemical generation of volatile cadmium species

Photochemical generation of a volatile molecular Cd species from an acetic acid medium was accomplished using a thin film generator comprising a 20 W low pressure UV source. Argon gas was used to sweep the product vapor to a quartz tube atomizer heated to 900 °C. No signal was generated below about 770 °C and optimum atomization conditions required addition of 10% hydrogen to the Ar transfer gas, indicative of a thermochemical atomization process similar to that undergone for metal hydrides. UV generation efficiency exceeded 90% but the transfer of the analyte to the detector was problematic and precision of measurement was near 30% RSD. Despite such conditions, an estimated limit of detection was 2 μg l−1.

Ion/molecule reaction between sulphur hexafluoride negative ion and water under atmospheric pressure ionization mass spectrometric conditions

Reaction between SF6− and water to form SF4O−1 has been observed in the ion source of an atmospheric pressure ionization mass spectrometer.

Hypercoulometry in a pulsed conventional electron-capture detector☆

Abstract Hypercoulometric response was observed in an electron-capture detector with conventional dimensions and geometry, and under typical pulsed conditions. This response is linked speculatively to the space charge mechanism.