Direct determination of oxygen and other elements in non-conducting crystal materials by pulsed glow discharge time-of-flight mass spectrometry with potassium titanyl phosphate as an example

Direct quantification of oxygen in dielectric materials using non-destructive or nearly non-destructive techniques still remains a nontrivial task. Simultaneous assessment of oxygen with other elements in a single analytical procedure is even more challenging. In the current study, a method of direct determination of oxygen and other matrix elements in solid samples, based on time-of-flight mass spectrometry with pulsed glow discharge in combined hollow cathode (CHC) is designed and tested. The possibility to effectively ionise oxygen owing to the electron impact mechanism under short repelling pulse delays has been shown. Stable sputtering and ionisation of dielectric samples were obtained via sample coating with thin conducting layer of silver. The parameters of oxygen quantification were optimised: duration and voltage of the discharge pulse, cell pressure, repelling pulse delay and material of the auxiliary cathode. The calibrations of oxygen, phosphorus and potassium are presented. The intensity of ¹⁶O⁺ was shown to be highly dependent on discharge cell pressure. The limits of detection were 0.001, 0.001, and 0.002 mass% for oxygen, phosphorus and potassium respectively. The designed approach enables direct, fast and accurate quantitative and in depth analysis of oxygen-containing samples.