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. 2013 Jan 16;121(3):283–286. doi: 10.1289/ehp.1206093

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On-line SPE-HPLC-MS/MS configuration, adapted from a previous publication (Ye et al. 2008), with guard cartridges after SPE and HPLC pumps. The 10-port switching valve configuration shown corresponds to the time period when the sample is loaded onto the SPE cartridge.