A colloidal graphite-coated emitter is introduced for sheathless capillary electrophoresis/nanoelectrospray ionization time-of-flight mass spectrometry (CE/ESI-TOFMS). The conductive coating can be produced by brushing the capillary tip to construct a fine layer of 2-propanol-based colloidal graphite. The fabrication involves a single step and requires less than 2 min. Full cure properties develop in approximately 2 h at room temperature and then the tip is ready for use. The coated capillary tip is applied as a sheathless electrospray emitter. The emitter has proven to bear stable electrospray and excellent performance for 50 microm i.d. x 360 microm o.d. and 20 microm i.d. x 360 microm o.d. capillaries within the flow rate of 80-500 nL/min; continuous electrospray can last for over 200 h in positive mode. Baseline separation and structure elucidation of two clinically interesting basic drugs, risperidone and 9-hydroxyrisperidone, are achieved by coupling pressure-assisted CE to ESI-TOFMS using the described sheathless electrospray emitter with a bare fused-silica capillary at pH 6.7. It is found that the signal intensity of m/z in sheathless CE/ESI-TOFMS at pH 6.7 is approximately 50 times higher than that at pH 9.0 for the two analytes, although the electroosmotic flow (EOF) at pH 9.0 provides sufficient flow rate (approximately 150 nL/min) to maintain electrospray.

中文翻译：

---

用于无鞘毛细管电泳/纳米电喷雾电离质谱的胶体石墨涂层发射体。

引入了涂有胶体石墨的发射器，用于无鞘毛细管电泳/纳米电喷雾电离飞行时间质谱（CE / ESI-TOFMS）。可以通过刷毛细管尖端以构造2-丙醇基胶体石墨的精细层来生产导电涂层。制造仅需一个步骤，所需时间不到2分钟。在室温下约2小时内，会完全固化，然后即可使用。涂覆的毛细管尖端用作无护套电喷雾发射器。事实证明，该发射器在流量为80-500 nL / min的条件下对50微米x 360微米和20微米x 360微米的毛细管具有稳定的电喷雾性能和优异的性能；连续电喷雾在正模式下可以持续200个小时以上。通过使用描述的无鞘电喷雾发射器和裸露的熔融石英毛细管在pH 6.7下将压力辅助的CE与ESI-TOFMS偶联，可以实现两种临床上有趣的基础药物利培酮和9-羟基利培酮的基线分离和结构解析。发现在两种条件下，pH 6.7的无鞘CE / ESI-TOFMS中m / z的信号强度比pH 9.0的m / z信号强度大约高50倍，尽管pH 9.0的电渗流（EOF）提供了足够的流速（约150 nL / min）以保持电喷雾。