Journal of Chromatography B, 1004 (2015) 1–9 Contents lists available at ScienceDirect Journal of Chromatography B jou rn al hom ep age: www.elsevier.com/locate/chromb Direct injection human plasma analysis for the quantification of antihypertensive drugs for therapeutic drug monitoring using hydrophilic interaction liquid chromatography/electrospray ionization mass spectrometry Stefanos Meimaroglou a , Ariadni Vonaparti a , George Migias b , Dimitra Gennimata c , Sofia Poulou d , Irene Panderi a,∗ a University of Athens, School of Pharmacy, Division of Pharmaceutical Chemistry, Athens, Panepistimopolis—Zografou, 157 71 Athens, Greece b Athens General Hospital “Alexandra”, 80 Vas. Sofias Avenue, 115 28 Athens, Greece c Athens General Hospital “Korgialenio-Benakio National Red Cross” Erithrou Stavrou 1, 11526 Athens, Greece d Integrated Scientific Solutions, Protesilaou 101, 131 22 Athens, Greece a r t i c l e i n f o Article history: Received 17 July 2015 Received in revised form 31 August 2015 Accepted 2 September 2015 Available online 25 September 2015 Keywords: Direct injection analysis Hydrophilic interaction liquid chromatography Mass spectrometry Therapeutic drug monitoring Antihypertensive drugs Human plasma a b s t r a c t The concept of personalized medicine is related to the development of new sensitive, precise and accurate analytical methods for therapeutic drug monitoring. In this article a rapid, sensitive and specific method was developed for the quantification of aliskiren, losartan, valsartan and hydrochlorothiazide in human plasma. Sample preparation was performed by protein precipitation with acetonitrile followed by filtra- tion. All analytes and the internal standard (tiamulin) were separated by hydrophilic interaction liquid chromatography using an X-Bridge-HILIC analytical column (150.0 × 2.1 mm i.d., particle size 3.5 m) under isocratic elution. The mobile phase was composed of a 10% 5 mM ammonium formate water solu- tion pH 4.5, adjusted with formic acid, in acetonitrile and pumped at a flow rate of 0.25 mL min -1 . The assay was linear over the concentration range of 5–500 ng mL -1 for all the analytes. Intermediate preci- sion was less than 5.2% over the tested concentration ranges. The method is the first reported application of HILIC in the analysis antihypertensives in human plasma. With a small sample size (50 L human plasma) and a run time less than 6.0 min for each sample the method can be used to support a wide range of clinical studies and therapeutic drug monitoring. © 2015 Elsevier B.V. All rights reserved. 1. Introduction Hypertension increases the risk for a variety of cardiovas- cular diseases, including stroke, coronary artery disease, heart failure and peripheral vascular disease [1]. In the antihypertensive treatment clinical trials document that achieving blood pressure targets is usually not possible with a single agent. The majority of patients with hypertension require two or more agents, which either interfere with different pressure mechanisms or effectively block counter regulatory responses, so as to lower blood pressure effectively [2]. Aliskiren [3,4] is the first in a new class of orally active direct renin inhibitors that has been approved since 2007 for use in ∗ Corresponding author at: University of Athens, School of Pharmacy, Division of Pharmaceutical Chemistry, Panepistimiopolis, Zografou, Athens 157 71, Greece. Fax: +30 210 7274747. E-mail addresses: ipanderi@pharm.uoa.gr, irenepanderi@gmail.com (I. Panderi). the treatment of hypertension. It is administered alone [5] or in combination with other antihypertensive agents, including thi- azide diuretics like hydrochlorothiazide [6] or angiotensin receptor blockers like valsartan or losartan [7,8]. Hydrochlorothiazide is used in many cases as initial antihypertensive treatment. However, the addition of an agent acting on the renin-angiotensin system is a commonly used therapeutic strategy for patients with an unsat- isfactory blood pressure response to hydrochlorothiazide [9]. The concept of personalized medicine along with the intro- duction of new drug combinations for therapy is related to the development of new sensitive, precise and accurate analytical methods for therapeutic drug monitoring. The purpose of this study was to develop a new method for the detection and identification of some of the most commonly prescribed antihypertensive drugs in human plasma. Literature survey revealed only a few methods that have been applied to the determination of aliskiren in combination with other antihypertensive drugs in biofluids. These methods include, http://dx.doi.org/10.1016/j.jchromb.2015.09.001 1570-0232/© 2015 Elsevier B.V. All rights reserved.