On-line hyphenation of solid-phase extraction to chromatographic separation of sulfonamides with fused-core columns in sequential injection chromatography Alex D. Batista a , Petr Chocholouš b,n , Dalibor Šatínský b , Petr Solich b , Fábio R.P. Rocha a a Centro de Energia Nuclear na Agricultura, Universidade de São Paulo, P.O. Box 96, 13400-970 Piracicaba SP, Brazil b Department of Analytical Chemistry, Faculty of Pharmacy, Charles University in Prague, Heyrovského 1203, Hradec Králové, Czech Republic article info Article history: Received 15 December 2013 Received in revised form 14 July 2014 Accepted 21 July 2014 Keywords: SPE-SIC Sequential Injection Chromatography Pentafluorophenylpropyl F5 Fused core Sulfonamides On-line SPE Anion-exchange abstract On-line sample pretreatment (clean-up and analyte preconcentration) is for the first time coupled to sequential injection chromatography. The approach combines anion-exchange solid-phase extraction and the highly effective pentafluorophenylpropyl (F5) fused-core particle column for separation of eight sulfonamide antibiotics with similar structures (sulfathiazole, sulfanilamide, sulfacetamide, sulfadiazine, sulfamerazine, sulfadimidine, sulfamethoxazole and sulfadimethoxine). The stationary phase was selected after a critical comparison of the performance achieved by three fused-core reversed phase columns (Ascentis s Express RP-Amide, Phenyl-Hexyl, and F5) and two monolithic columns (Chromo- lith s High Resolution RP-18 and CN). Acetonitrile and acetate buffer pH 5.0 at 0.60 mL min À1 were used as mobile phase to perform the separations before spectrophotometric detection. The first mobile phase was successfully used as eluent from SPE column ensuring transfer of a narrow zone to the chromatographic column. Enrichment factors up to 39.2 were achieved with a 500 mL sample volume. The developed procedure showed analysis time o10.5 min, resolutions 41.83 with peak symmetry r1.52, LODs between 4.9 and 27 mgL À1 , linear response ranges from 30.0 to 1000.0 mgL À1 (r 2 40.996) and RSDs of peak heights o2.9% (n ¼6) at a 100 mgL À1 level and enabled the screening control of freshwater samples contaminated at the 100 mgL À1 level. The proposed approach expanded the analytical potentiality of SIC and avoided the time-consuming batch sample pretreatment step, thus minimizing risks of sample contamination and analyte losses. & 2014 Elsevier B.V. All rights reserved. 1. Introduction Aiming multidetermination, sequential injection analysis (SIA) was coupled with chromatographic monolithic columns, introdu- cing the sequential injection chromatography (SIC). This approach combines the versatility of SIA for solutions handling with the potential of chromatography for highly efficient separations [1]. Monolithic columns, which operate at pressures within 300– 750 psi, were until recently the only option for SIC separations. The major hindrance was the lack of different stationary phases, being the RP-C18, RP-C8 and silica phases, the only commercially available options. The introduction of chromatographic columns with fused-core particle technology increased the applicability of SIC [2]. These columns are filled by 2.7-mm diameter solid fused-silica core particles which 1.7-mm core is impermeable to the mobile phase (as well as to the analytes) and a 0.5-mm thick layer shell of porous silica gel that acts as stationary phase. Thus, the mobile phase has shorter diffusion path in the particle, which reduces axial disper- sion of the analytes and minimizes peak broadening. Short fused- core particle columns with lower dead volumes then provides better separation performance than longer monolithic columns [2] and it is possible to exploit different commercially available stationary phases to improve selectivity [3]. The F5 stationary phase is composed by pentafluorophenyl- propyl groups that provide a stable, reversed-phase packing with electron-deficient phenyl rings due to the presence of electro- negative fluorines, which can retain compounds by forming p–p and polar interactions [4]. This phase exhibits higher ion-exchange character compared to its alkyl counterparts (i.e. C18 and C8) and thus it provides excellent chromatographic separations of analytes with different ionization grades. Then, F5 columns can show a dual-mode retention (reversed-phase and hydrophilic interaction). Contents lists available at ScienceDirect journal homepage: www.elsevier.com/locate/talanta Talanta http://dx.doi.org/10.1016/j.talanta.2014.07.056 0039-9140/& 2014 Elsevier B.V. All rights reserved. n Corresponding author. E-mail address: petr.chocholous@faf.cuni.cz (P. Chocholouš). Please cite this article as: A.D. Batista, et al., Talanta (2014), http://dx.doi.org/10.1016/j.talanta.2014.07.056i Talanta ∎ (∎∎∎∎) ∎∎∎–∎∎∎