Abstract:

Bonded stationary phase of sub-micron diameter for the preparation of columns f or capillary electrochromat-ographic analysis was prepared. The procedure was as follows: From a raw material of the mixture of tetraethoxy-silane and triet hoxy vinylsilane, an inorgano-organo hybrid siliceous particles with bonded vin yl groups were prepared using the Sol-gel technique. On the basis of the prepa red particles, copolymer of methoxy styrene-styrene-divinylbenzene was encapsu lated onto its surface to prepare a new kind of stationary phase.The new stationary phase was packed into capillary columns (i.d. 0.32 mm) and their electrochromatographic characteristics tested. It was found that much higher analytical speed could be obtained on this new phase.From the electrochromatogram obtained on a previously synthesized stationary pha se which used the same matrix and which was encapsulated with polystyrene a poly mer containing no methoxy groups, it can be seen that although the applied volta ge was 15 kV, the non-retaining solute, thiourea, eluted the column in as much as 3.9 min, benzene, toluene and naphthalene eluted the column in 4.9, 5.1 and 6.32 min, respectively; whereas on the column of the same length packed with met hoxystyrene polymer encapsulated phase of similar length, thiourea eluted the co lumn in only 0.53 min, and benzene, toluene and naphthalene eluted the column in 0.53, 0.62, 0.69 and 0.79 min, respectively. Thus this kind of high-speed elec trochr omatographic stationary phase can offer analytical speed several times higher th an “normal” phases. For the abovementioned solutes, the ratio between their re tention times on the two kinds of stationary phases were 7.3,7.9,7.4 and 8.0, respectively.The reason of the aforementioned high analytical speed might be elucidated as fo llows: the methoxy groups on the stationary phase surface might result in some p henolic hydroxyl groups (upon preparation of the columns we rinsed the columns w ith acidic solution, this probably hydrolyzed the methoxy groups, producing phen olic hydroxyl groups). These hydroxyl groups resulted in higher electroosmotic f low, and the latter in turn greatly boosted the analytical speed.