RA Koster currently works as Associate Director of Bioanalytical Science at the LC-MS/MS department at PRA Health Sciences in the Laboratory in Assen, The Netherlands. He is responsible for the LC-MS/MS analytical method development and leads a team of method development analysts and scientists. As global microsampling specialist within PRA he is interested in all developments regarding microsampling and aims to continuously improve microsampling techniques. He has been working in the field of bioanalysis for 19 years, in which he performed and supervised numerous analytical method developments using LC-MS/MS. He started his career in 2001 at Pharma Bio-Research (before it was acquired by PRA) as an LC-MS/MS analyst. In 2005, he moved to the University Medical Center Groningen where he focused on the development and validation of analytical methods for drugs and drugs of abuse in matrices like blood, plasma, hair, saliva, dried blood spots and volumetric absorptive microsampling with LC-MS/MS. In 2015 he obtained his PhD on the subject 'The influence of the sample matrix on LC-MS/MS method development and analytical performance'. In 2017, he started as Senior Scientist at PRA Health Sciences and in 2019, he accepted his current role of Associate Director of Bioanalytical Science. He is a (co-)author of more than 35 publications.