Rapid determination of indapamide in human urine using novel low-density solvent based ultrasound assisted emulsification microextraction coupled with high performance liquid chromatography-variable wavelength detection Abilasha Ramkumar, a Vinoth Kumar Ponnusamy a and Jen-Fon Jen * ab Indapamide belongs to the class of thiazide-type diuretic drugs and is widely used in the treatment of hypertension and nephrolithiasis. In this work, a simple, rapid and efficient low density solvent (LDS) based ultrasound assisted emulsification microextraction (USAEME) method combined with high performance liquid chromatography-variable wavelength detection (HPLC-VWD) was investigated for the determination of a popular drug of abuse, indapamide, in human urine samples. The target compound was extracted from acidified sample solution with a few microliter amount of LDS by a USAEME method. The influence of several important experimental variables such as selection of the extraction solvent and its volume, ultrasonication time, pH and ionic strength were thoroughly examined and optimized. Under optimal conditions, the calibration was linear in concentration range from 1–100 ng mL 1 with a correlation coefficient of 0.9977 for the target analyte. The limit of detection based on signal to noise ratio of 3 was 0.3 ng mL 1 and the relative standard deviations varied from 1.2–6.6%. The proposed method provides a rapid, sensitive, low cost, easy to handle, and convenient procedure to determine indapamide in human urine samples. 1 Introduction 3-(Aminosulfonyl)-4-chloro-N-(2,3-dihydro-2-methyl-1H-indol-1- yl)benzamide (indapamide) is a diuretic and antihypertensive drug and some of its pharmacodynamic activity is related to a thiazide-type effect. 1 Clinical uses of indapamide include the treatment of nephrogenic diabetes insipidus, hypertension, hypercalciuria, glaucoma, and edema, among other diseases. 2,3 Indapamide (a popular drug of abuse) is also misused by athletes in sports for several reasons including the reduction of body weight, to reduce urinary concentration of other pro- hibited substances in order to avoid a positive doping test and to overcome uid retention caused by the use of anabolic steroids. 4,5 Indapamide belongs to the group of diuretics that are banned substances in sports since 1986. 6 Moreover, to date the pharmacokinetic proles of indapamide pills compared with conventional tablets in vivo is unknown. The analytical determination of indapamide is desirable 7 taking into account that its overdose might lead to severe hyponatraemia, with symptoms varying from nausea to seizures and coma and hypokalemia, 8,9 which could lead to fatal arrhythmia. 10 In 2007, a case report linking indapamide and hyperparathyroidism was published. 11 According to literature evidence, indapamide deter- mination has been accomplished in various biological uids like urine, 12,13 serum 14 and plasma. 15,16 Therefore, a simple, rapid and efficient analysis method is needed for the determination of indapamide in urine sample so as to evaluate the pharmacoki- netic parameters and also to monitor its drug abuse in sports. Most sample preparation techniques available for the extraction of indapamide in various biological matrices include liquid–liquid extraction (LLE) and solid phase extraction (SPE). 17–19 However, the disadvantage of these methods is that they are either involved in several extraction steps or yield poor separation from the biological sample's endogenous interfer- ences, low extraction recovery and the need for a large amount of internal standard. 17,18 Ideally, sample-preparation techniques should be fast, inexpensive and compatible with a range of analytical instruments, so the current trend is towards decreasing the quantities of organic solvents, simplication and miniaturization of the sample-preparation steps. 20 To fulll this purpose, liquid-phase microextraction (LPME) techniques like single drop microextraction (SDME), hollow-ber LPME and dispersive liquid–liquid microextraction (DLLME) were developed. 21–25 More recently, a novel microextraction technique developed by Garcia-Jares et al., named ultrasound-assisted a Department of Chemistry, National Chung Hsing University, Taichung 402, Taiwan. E-mail: jen@dragon.nchu.edu.tw; Fax: +886-4-22862547; Tel: +886-4-22853148 b Department of Health and Nutrition Biotechnology, Asia University, Wufeng District, Taichung 413, Taiwan Cite this: Anal. Methods, 2013, 5, 2572 Received 31st January 2013 Accepted 15th March 2013 DOI: 10.1039/c3ay40187a www.rsc.org/methods 2572 | Anal. Methods, 2013, 5, 2572–2577 This journal is ª The Royal Society of Chemistry 2013 Analytical Methods PAPER Published on 15 March 2013. Downloaded by National Chung Hsing University on 16/12/2013 03:36:35. View Article Online View Journal | View Issue