RATIONALE: Electrospray ionisation mass spectrometric (ESI-MS) analysis of Pd in complex matrices is difficult due to the multiplicity of matrix effects. Two different approaches, internal standard and matrix separation, were investigated for developing a reliable analytical procedure for the trace level determination of Pd in simulated high-level liquid waste (SHLLW) solutions. METHODS: An ESI mass spectrometer with a quadrupole-time-of-flight analyser was used to study the speciation of the palladium-benzoylthiourea (Pd-BTU) complex and to determine the Pd content. The Pd-BTU complex was selectively pre-concentrated using disposable pipette extraction (DPX). Extraction parameters as well as ESI-MS parameters such as concentration of BTU, acidity, composition of medium and capillary voltage, etc., were optimized based on the major species [Pd(BTU)2S]+. RESULTS: The method gave quantitative and selective pre-concentration of the Pd-BTU complex from SHLLW. Linearity from 5 ppb to 200 ppb and a limit of detection of 0.012 ppb were obtained for Pd. No interference from the neighboring elements, viz. ruthenium, rhodium, silver and cadmium, was observed during the determination of Pd based on the [Pd(BTU)2S]+ peak. The ESI signal intensity was not influenced by the presence of the many other elements in the SHLLW solution. CONCLUSIONS: Good sensitivity, tolerance to matrix concentration and the absence of interference from neighboring elements make the method very promising for the determination of Pd at low levels in complex samples. We have demonstrated the capability of ESI-MS for the quantification of Pd in complex matrices and its potential for providing data on speciation, using the Pd-BTU complex. Copyright © 2012 John Wiley & Sons, Ltd.