Communication Purge NMR: Effective and easy solvent suppression Andre J. Simpson * , Sarah A. Brown Department of Chemistry, University of Toronto, 1265 Military Trail, Toronto, Ont., Canada M1C 1A4 Received 25 February 2005; revised 23 April 2005 Available online 16 June 2005 Abstract Presaturation utilizing relaxation gradients and echoes is an extremely easy and effective approach to solvent suppression in solu- tion state nuclear magnetic resonance spectroscopy. The experiment produces flat baselines, excellent phase properties, and highly selective suppression that betters that of commonly used sequences. Furthermore, the only parameter that needs adjusting is the presaturation power, making it easy to implement even for non spectroscopists. Considering these factors, we envisage the approach will have wide spread applications. Ó 2005 Elsevier Inc. All rights reserved. Keywords: Solvent suppression; Solution state NMR; HR-MAS NMR; Metabonomics; Aqueous systems 1. Introduction Solvent suppression is used widely in modern NMR especially with the increased popularity of hyphenated techniques such as LC-NMR, and the need to study many chemical and biological systems in non deuterated solvents. Numerous solvent suppression approaches are available today but the classical presaturation experi- ment is probably still the most commonly employed in routine chemical studies due mainly to its easy imple- mentation. Classical presaturation, however, has numer- ous drawbacks, which can include poor phase properties and lack of suppression in comparison to more recent gradient based solvent suppression approaches [1]. However, many modern gradient based approaches re- quire careful calibration of power levels, the use of shaped pulses, and often the optimization of parameters in real time to obtain optimal suppression. In this com- munication, we introduce Presaturation utilizing relaxa- tion gradients and echoes (PURGE) as an alternative approach to solvent suppression. PURGE is a novel ap- proach that is as simple to use as the classical presatura- tion experiment but performs at least as well as more complex approaches such as WET [2], WATERGATE [3,4], and excitation sculpting [5]. 2. Results Presaturation utilizing relaxation gradients and ech- oes (PURGE) is an extremely easy and effective ap- proach to solvent suppression in solution state NMR spectroscopy. The basic purge sequence is highlighted in Fig. 1. The initial presaturation period is analogous to that in the classic presaturation experiment and is car- ried out, on resonance, during the relaxation delay. This is followed by a 90° pulse which flips the magnetization into the XY plane. After a short delay d (200 ls for rou- tine applications, during which presaturation is applied using the main channel, note power switching delays (4 ls in our case) are not shown) the magnetization is in- verted by a 180° pulse, and then refocused by an identi- cal delay d. During this period (segment A highlighted in Fig. 1) the magnetization is aligned along the XY plane. This block primarily helps suppress exchangeable www.elsevier.com/locate/jmr Journal of Magnetic Resonance 175 (2005) 340–346 1090-7807/$ - see front matter Ó 2005 Elsevier Inc. All rights reserved. doi:10.1016/j.jmr.2005.05.008 * Corresponding author. Fax: +1 416 287 7279. E-mail address: andre.simpson@utoronto.ca (A.J. Simpson).