3418 J. Sep. Sci. 2014, 37, 3418–3425 Fabrice Gritti 1 Stephen Shiner 2 Jacob N. Fairchild 2 Georges Guiochon 1 1 Department of Chemistry, University of Tennessee Knoxville, TN, USA 2 Waters Corporation, Milford, MA, USA Received July 22, 2014 Revised September 3, 2014 Accepted September 4, 2014 Research Article Characterization and kinetic performance of 2.1 × 100 mm production columns packed with new 1.6 m superficially porous particles The overall kinetic performance of three production columns (2.1 mm × 100 mm format) packed with 1.6 m superficially porous CORTECS-C 18 + particles was assessed on a low- dispersive I-class ACQUITY instrument. The values of their minimum intrinsic reduced plate heights (h min = 1.42, 1.57, and 1.75) were measured at room temperature (295 K) for a small molecule (naphthalene) with an acetonitrile/water eluent mixture (75:25, v/v). These narrow-bore columns provide an average intrinsic efficiency of 395 000 plates per meter. The gradient separation of 14 small molecules shows that these columns have a peak capacity about 25% larger than similar ones packed with fully porous BEH-C 18 particles (1.7 m) or shorter (50 mm) columns packed with smaller core–shell particles (1.3 m) operated under very high pressure (>1000 bar) for steep gradient elution (analysis time 80 s). In contrast, because their permeabilities are lower than those of columns packed with larger core–shell particles, their peak capacities are 25% smaller than those of narrow-bore columns packed with standard 2.7 m core–shell particles. Keywords: Column efficiency / Core–shell particles / Fast gradient / Peak capacity / Ultra high pressure chromatography DOI 10.1002/jssc.201400703 1 Introduction Chromatographic columns packed with sub-3 m core–shell particles [1] have remained tremendously successful over the last eight years [2]. Columns packed with 2.7 m core– shell particles can provide efficiencies comparable to that of columns packed with sub-2 m fully porous particles but can be operated at two to three times lower back pressures [3–5]. Many column manufacturers are now commercializing con- ventional or narrow-bore columns packed with sub-3 m core–shell particles (Advanced Material Technologies, Phe- nomenex, Agilent Technologies, Sigma–Aldrich/Supelco, ThermoScientific, Macherey-Nagel, Chromanik, and Wa- ters). The use of columns packed with these particles has helped scientists to decipher mass transfer mechanisms in chromatography [6–27] and to anticipate trends in the prepa- ration of the new generation of columns for very high- pressure liquid chromatography (vHPLC) columns [28]. One disadvantage of analytical scale columns packed with sub-3 m core–shell particles is the small width of peaks Correspondence: Dr. Georges Guiochon, Department of Chem- istry, University of Tennessee Knoxville, TN 37996, USA E-mail: guiochon@utk.edu Fax: 865-974-2667 Abbreviations: FIB, focused ion beam; LTNA, low- temperature nitrogen adsorption eluted from them. They are so narrow that it is no longer possible to neglect the instrument contribution to the width of the eluted bands of weakly or moderately retained com- pounds [29]. A first solution was to reduce the detector cell volume and the diameter of the connecting tubes of the stan- dard 400 bar instruments [29–31]. A second solution was to replace standard HPLC instruments with new, more costly low-dispersive vHPLC ones. These instruments are mostly designed to run narrow-bore columns packed with sub-2 m particles at pressures up to 1200 bar. So far, only one man- ufacturer has produced sub-2 m core–shell particles, first the 1.7 m Kinetex particles, recently the 1.3 m Kinetex particles. They provide columns having maximum efficien- cies exceeding 400 000 plates per meter and challenge the capacities of vHPLC instruments in terms of pressure limits (1200 bar) and system band spreading. Injection devices must be designed to minimize the widths of sample bands entering columns and detection cells should be small, not to broaden the bands exiting the column. Therefore, the actual kinetic performance of narrow-bore columns packed with sub-2 m particles depends very much on the nature of the instrument used. Additionally, there are no hybrid core–shell particles, so, one cannot use high pH mobile phases for extended peri- ods of time. Waters has recently developed sub-2 m superficially porous particles (1.6 m CORTECS-C 18 +). A preliminary Colour Online: See the article online to view Figs. 2–4 in colour. C  2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim www.jss-journal.com