Short communication Martin Pumera 1 Jindr ˇich Jindr ˇich 2 Michal Valás ˇ ek 2 Jaroslav Pecka 2 1 Department of Chemistry, Universitat Autonoma de Barcelona, Bellaterra, Barcelona, Spain 2 Department of Organic Chemistry, Charles University, Hlavova, Prague, Czech Republic Nonaqueous capillary electrophoretic assays of p-phenylene-bis-4,4’-(1-aryl-2,6-diphenylpyridinium) molecular wires A nonaqueous CE system for separation and detection of novel electron-dopable molecular wires based on p-phenylene-bis-4,4’-(1-aryl-2,6-diphenylpyridinium) oligo- mers is described. The method is based on the coupling of CE separation in pure organic solvent, DMF with 50 mM acetic acid, and UV detection at 338 nm. The system offers a rapid measurement in less than 20 min for two priority nanowires and their impurities. Calibration data confirmed linear response for all compounds of interest in the concentration range 0.1–1.0 mg/mL. A highly stable response was observed for repetitive injections (RSD  2.8%, n = 10). Keywords: Dimethylformamide / Electron dopable molecular wires / Nanowires / Nonaqueous capillary electrophoresis DOI 10.1002/elps.200500414 Molecular electronics (molectronics) have witnessed enormous advances toward the realization of electronic computer on molecular scale over the past few years [1, 2]. These great achievements were realized by using bio- molecules, semiconductor nanowires, and/or aromatic organic molecules as parts of molecular semiconductor logic circuits [3, 4]. One of the last developments toward “nanotransistors” is the construction of rigid linear mo- lecular wires based on p-phenylene-bis-4,4’-(1-aryl-2,6- diphenylpyridinium) (PPBADPP) oligomers, which are easily dopable with electrons, by Michl and co-workers [5]. To use such nanowires as parts of nanocomputers, it is necessary to provide them in high degree purity. This paper describes nonaqueous CE (NACE) protocol for rapid purity control of PPBADPP oligomers. NACE has recently received considerable attention and it has been demonstrated that substitution of the aqueous phase by nonaqueous systems offers new possibilities for capillary electrophoretic separations [6–11]. The use of organic solvents offers several advantages, including: tailored selectivity of separations via changes in solvatation or acid-base properties of analytes [12], effective sample introduction into the mass spectrometer [13], reduced electrophoretic currents, and improved solubility of hydrophobic compounds [14–17]. The usefulness of NACE has been demonstrated on wide scale of exam- ples, ranging from environmental analysis [14, 15] through pharmaceutical [17, 18], forensic [6, 7, 19], and food sci- ence [20] toward genomic applications [21]. The need to quantitate newly prepared PPBADPP mono- mer and trimer molecules (structural representations are shown in Fig. 1) and their by-products, which are not sol- uble in aqueous media nor in wide range of organic sol- vents [5], led us to use NACE in DMF-based media. So far, the purity of PPBADPP oligomers has been controlled only by 1 H NMR spectra (in DMSO-d 6 ) [5]. There has not been yet described any analytical method for the quanti- tation and purity control of such compounds. The aim of this study is to demonstrate effective separa- tion of PPBADPP monomer and trimer from their by- products using NACE with UV detection. Figure 2 dis- plays typical electrophoregrams of PPBADPP monomer (Fig. 2A) and trimer (Fig. 2B) purity analysis by NACE (using equipment Crystal CE with UV detector Unicam 4225, ATI Unicam, Great Britain). Separations were per- formed in untreated, open-tube silica capillaries (effective length 50.0 cm, total length 63.0 cm, internal diameter 100 mm, provided by Composite Metal Services, Great Britain; 50 mM acetic acid in DMF; separation voltage 130 kV; injection at 1000 Pa for 6 s; detection at 338 nm). Well-defined and resolved peaks are observed for both major components. Migration times of the PPBADPP monomer and trimer are 3.19 and 7.54 min, which results Correspondence: Dr. Martin Pumera, Department of Chemistry, Universitat Autonoma de Barcelona, E-08193 Bellaterra, Barce- lona, Spain E-mail: martin.pumera@uab.es Fax: 134-93581-2379 Abbreviations: NACE, nonaqueous CE; PPBADPP , p-pheny- lene-bis-4,4’-(1-aryl-2,6-diphenylpyridinium) Electrophoresis 2005, 26, 4465–4467 4465  2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim CE and CEC