Analytica Chimica Acta 721 (2012) 147–153 Contents lists available at SciVerse ScienceDirect Analytica Chimica Acta j ourna l ho me page: www.elsevier.com/locate/aca High-performance liquid chromatography with fluorescence detection and ultra-performance liquid chromatography with electrospray tandem mass spectrometry method for the determination of indoleamine neurotransmitters and their metabolites in sea lamprey plasma Huiyong Wang, Erin J. Walaszczyk, Ke Li, Yu-Wen Chung-Davidson, Weiming Li ∗ Department of Fisheries and Wildlife, Room 13 Natural Resources Building, Michigan State University, East Lansing, MI 48824, USA a r t i c l e i n f o Article history: Received 2 November 2011 Received in revised form 13 January 2012 Accepted 15 January 2012 Available online 24 January 2012 Keywords: Neurotransmitters Plasma HPLC UPLC–MS/MS Liquid–liquid extraction Solid phase extraction a b s t r a c t We present a comparison of two sensitive methods, HPLC with fluorescence detector (HPLC/FLD) and UPLC with electrospray tandem mass spectrometry (UPLC/MS/MS), for the determination of indoleamine neurotransmitters (NTs) and their metabolites in sea lamprey plasma samples. Liquid–liquid extraction (LLE) and solid-phase extraction (SPE) were also tested for recovery and matrix effect. The recoveries of SPE determined by HPLC/FLD and UPLC/MS/MS ranged from 75 to 123% and 78 to 105%, respectively, while the recoveries of LLE ranged from 45 to 73% and 48 to 75%, respectively. SPE combined with HPLC/FLD and UPLC/MS/MS to determine the target analytes in plasma samples were validated of the sensitiv- ity, reproducibility, accuracy and precision. Both methods exhibited excellent linearity in the range of 0.2–50 ng mL -1 for all analytes. The limits of detection (LOD) varied from 0.04 ng mL -1 to 0.13 ng mL -1 for HPLC/FLD method and 0.003 ng mL -1 to 0.02 ng mL -1 for UPLC/MS/MS method. The inter-day accuracy ranged from 82.5 to 127.0% for HPLC/FLD and 93.0 to 113.0% for UPLC/MS/MS. The inter-day precision ranged from 9.9 to 32.3% for HPLC/FLD and 5.4 to 13.2% for UPLC/MS/MS. These results demonstrated that the values obtained by both methods were within the satisfactory range and the UPLC/MS/MS method provided more accurate and precise measurements than HPLC/FLD method. The comparison is of great importance to determine the available detectors, considering the complexity and expensiveness versus quality parameters. These two methods were applied to the analysis of four important indoleamine neuro- transmitter analytes (5-hydroxytryptamine, 5-hydroxyindole-3-acetic acid, tryptamine and melatonin) in sea lamprey plasma samples. © 2012 Elsevier B.V. All rights reserved. 1. Introduction Sea lampreys are an invasive parasitic jawless vertebrate in the Laurentian Great Lakes of the North America. They contribute to the decline of many economic fish species in the Great Lakes. They are also a unique advantageous model for pheromone appli- cations in vertebrate pest control [1]. Male sea lampreys release a sex pheromone, 7, 12, 24-trihydroxy-5-cholan-3-one 24- sulfate (3kPZS), to attract ovulating females in a long distance in the spawning stream [2–5]. The neural substrates for this behavioral response have not been fully elucidated. Indoleamine neurotrans- mitters (NTs) play an important role in behavioral regulations. For example, 5-hydroxytryptamine (5-HT or serotonin) is involved in the regulation of mood, depression, sleep, sexual arousal and func- tions. N-acetyl-5-methoxytryptamine (melatonin) is involved in ∗ Corresponding author. Tel.: +1 517 432 6705; fax: +1 517 432 1699. E-mail address: liweim@msu.edu (W. Li). maintaining the circadian rhythm of several biological functions. It would be beneficial to develop quantitative methods to study the indoleamine NTs and their metabolites in sea lampreys to under- stand the behavioral effects of the sex pheromone (Fig. 1). Extreme low levels of indoleamine NTs and their metabolites as well as the complexity of biological sample matrices have chal- lenged and prompted the researchers to develop sensitive and accurate analytical methods. Most studies quantified these analytes by radioimmunoassay (RIA) and chromatographic techniques, such as gas chromatography (GC), liquid chromatography (HPLC, UPLC), and capillary electrophoresis (CE), coupled with various detection techniques including ultraviolet (UV) detection [6,7], fluorescence detection (FLD) [8–11], electrochemical detection (ECD) [12,13], laser-induced fluorescence detection (LIFD) [14–16], and mass spectrometry [17]. These techniques are limited and unable to meet the increasing requirements for routine analyses. UV detector is not sensitive and specific for monoamine NTs. ECD lacks reproducibil- ity mainly due to hysteretic degradation of the electrode. GC/MS is not preferable because of the time-consuming derivatization step 0003-2670/$ – see front matter © 2012 Elsevier B.V. All rights reserved. doi:10.1016/j.aca.2012.01.025