Please cite this article in press as: M. Greguˇ s, et al., Portable capillary electrophoresis instrument with contactless conductivity detection for on-site analysis of small volumes of biological fluids, J. Chromatogr. A (2015), http://dx.doi.org/10.1016/j.chroma.2015.11.088 ARTICLE IN PRESS G Model CHROMA-357104; No. of Pages 9 Journal of Chromatography A, xxx (2015) xxx–xxx Contents lists available at ScienceDirect Journal of Chromatography A j o ur na l ho me page: www.elsevier.com/locate/chroma Portable capillary electrophoresis instrument with contactless conductivity detection for on-site analysis of small volumes of biological fluids Michal Greguˇ s a,b , Frantiˇ sek Foret a , Petr Kubá ˇ n a,∗ a Bioanalytical Instrumentation, CEITEC Masaryk University, Veveˇ rí 97, 602 00 Brno, Czech Republic b Department of Chemistry, Masaryk University, Kotlᡠrská 2, 611 37 Brno, Czech Republic a r t i c l e i n f o Article history: Received 11 September 2015 Received in revised form 6 November 2015 Accepted 29 November 2015 Available online xxx Keywords: Portable capillary electrophoresis Contactless conductivity detection Low sample volume Exhaled breath condensate Methanol intoxication a b s t r a c t A novel, easy to use and portable capillary electrophoretic instrument for injection of small volumes of biological fluids equipped with contactless conductivity detection was constructed. The instrument is lightweight (<5 kg), all necessary parts including a tablet computer are accommodated in a plastic brief- case with dimensions 20 cm × 33 cm × 17 cm (w × l × h), allows hydrodynamic injection of small sample volumes and can continuously operate for at least 10 hours. The semi-automated hydrodynamic sample injection is accomplished via a specially designed PMMA interface that is able to repeatedly inject sample aliquots from a sample volume as low as 10 L, with repeatability of peak areas below 5%. The developed interface and the instrument were optimized for the injection of biological fluids. Practical utility was demonstrated on the determination of formate in blood serum samples from acute methanol intoxication patients and on the analysis of ionic profile (nitrosative stress markers, including nitrite and nitrate) in the exhaled breath condensate from one single exhalation. © 2015 Elsevier B.V. All rights reserved. 1. Introduction Portable analytical instruments have seen significant develop- ment in recent decades and find variety of uses in environmental, forensic and clinical analysis, as well as in food quality control and chemical warfare detection. Portable pH and conductivity meters [1], photometers [2] and flow injection analyzers [3] typically mea- sure only one analyte at the time and have found importance for instance in water quality testing (measurement of pH, chlorine etc. in public pools [4]) or in medical applications (blood glucome- ters [5] or portable NOx analyzers for asthma control [6]). Portable instruments that can determine multiple species, often based on separation techniques, play a dominant role. Conventional packed column liquid chromatographic techniques, such as HPLC or IC do not transfer easily into portable format due to the high demands on the liquid propelling systems and on the detection modes. On the other hand, gas driven separation systems (GC, IMS) or low pres- sure liquid separation systems, such as nano-LC or open tubular IC (OTIC) can be easily operated with miniaturized low pressure pumps [7–9] or even by gravity [10]. ∗ Corresponding author. Tel.: +420 532290201; fax: +420 541212113. E-mail address: petr.kuban@ceitec.muni.cz (P. Kubá ˇ n). CE surpasses others analytical techniques in terms of separation efficiency, short analysis time and low consumption of sample, sol- vents and energy; it is one of the best candidate techniques for miniaturization and portable instrumentation construction. All CE parts can be easily miniaturized also due to the “no-pump” design – the liquid flow in CE is accomplished by applying high voltage over the separation capillary with no moving parts. Recent reviews cover all significant aspects of chip-based [11] and non-chip based [12] portable CE (PCE) systems, the non-chip based CE systems having a slight advantage due to the higher separation efficiency, sensitiv- ity and easier sampling interfacing, but being more bulky and less energy efficient. The first non-chip based PCE instrument was pre- sented by Kappes et al. in 1998 [13]. Several PCE instruments have been developed later including a commercial PCE instrument avail- able on the market since 2001 [14]. The majority of recent research activity in the field of PCE was however devoted to construction of custom-built instruments due to the inherent limitations of the available commercial PCE [15–17]. Development of various, low energy detection schemes was within the scope of the early publications, including potentiometry [13], amperometry [18], and most importantly conductimetry [19], owing to the development of the capacitively coupled contactless conductivity detection (C4D) [20,21]. Selected applications of PCE instruments with electro- chemical detection include analysis of anions and cations in water http://dx.doi.org/10.1016/j.chroma.2015.11.088 0021-9673/© 2015 Elsevier B.V. All rights reserved.