This report describes the development of a compact and versatile, micromachined chip device enabling the efficient coupling of capillary electrophoresis to electrospray mass spectrometry (CE-ESMS). On-chip separation provides a convenient means of achieving rapid sample cleanup and resolution of multicomponent samples (typically 2-5 min) prior to mass spectral analysis. A low dead volume connection facilitating the coupling of microfabricated devices to CE-ESMS was evaluated using two different interfaces. The first configuration used disposable nanoelectrospray emitters directly coupled to the chip device via this low dead volume junction, thereby providing rapid separation of complex protein digests. The performance of this interface was compared with that of more traditional configurations using a sheath flow CE-ESMS arrangement where a fused-silica capillary of varying length enabled further temporal resolution of the multicomponent samples. The sensitivity and analytical characteristics of these interfaces were investigated in both negative and positive ion modes using standard peptide mixtures. The separation performance for synthetic peptides using a chip coated with amine reagent ranged from 26,000 to 58,000 theoretical plates for a sheath flow CE-ESMS interface comprising a 15-cm CE column. Replicate injections of a dilution series of peptide standards provided detection limits of 45-400 nM without the use of on-line preconcentration devices. The reproducibility of migration time ranged from 0.9 to 1.5% RSD whereas RSDs of 5-10% were observed on peak areas. The application of these devices for the analysis of protein digests was further evaluated using on-line tandem mass spectrometry.

Fused-silica capillaries have been connected to microfluidic devices for capillary electrophoresis by drilling into the edge of the device using 200-μm tungsten carbide drills. The standard pointed drill bits create a hole with a conical-shaped bottom that leads to a geometric dead volume of 0.7 nL at the junction, and significant band broadening when used with 0.2-nL sample plugs. The plate numbers obtained on the fused-silica capillary connected to the chip were about 16-25% of the predicted numbers. The conical area was removed with a flat-tipped drill bit and the band broadening was substantially eliminated (on average 98% of the predicted plate numbers were observed). All measurements were made while the device was operating with an electrospray from the end of the capillary. The effective dead volume of the flat-bottom connection is minimal and allows microfluidic devices to be connected to a wide variety of external detectors.

Luminescence from Earth-abundant metal ions in solution at room temperature is a very challenging objective due to the intrinsically weak ligand field splitting of first row transition metal ions, which leads to efficient non-radiative deactivation via metal-centered states. Only a handful of 3d n metal complexes (n ≠ 10) show sizeable luminescence at room temperature. Luminescence in the near-infrared spectral region is even more difficult to achieve as further non-radiative pathways come into play. No Earth-abundant first-row transition metal complexes display emission > 1000 nm at room temperature in solution up to now. Here we report the vanadium(III) complex mer-[V(ddpd) 2 ][PF 6 ] 3 yielding phosphorescence around 1100 nm in valeronitrile glass at 77 K as well as at room temperature in acetonitrile with 1.810 -4 % quantum yield (ddpd = N,N '-dimethyl-N,N'-dipyridine-2-ylpyridine-2,6-diamine). In addition, mer-[V(ddpd) 2 ][PF 6 ] 3 shows very strong blue fluorescence with 2 % quantum yield in acetonitrile at room temperature. Our comprehensive study demonstrates that vanadium(III) complexes with d 2 electron configuration constitute a new class of blue and NIR-II luminophores, which complement the classical established complexes of expensive precious metals and rare-earth elements.