Fused-silica capillaries for capillary electrophoresis and gas chromatography: Inner surface corrosion, within-batch differences, and influence of drawing parameters studied by atomic force microscopy

Fused-silica capillaries for capillary electrophoresis (CE) and gas chromat ography (GC) were investigated by atomic force microscopy (AFM). Difference s from batch to batch and within one batch were often observed. Surface het erogeneity can be caused by bulk material, manufacturing parameters, or by aging effects. One batch of a fused-silica capillary was stored in water fo r three years at room temperature. The significant increase in surface roug hness (measured as rms = root mean square) during this time is demonstrated . The effect of different drawing temperatures was investigated. Other draw ing parameters were kept constant using one capillary batch. If the chosen drawing temperature was too low, the roughness Values more than doubled. Th is increase in roughness did not affect the separation efficiency. However, the relative standard deviation (RSD%) of migration times and peak areas i ncreased at the same time. Three capillary batches for gas chromatography o f different inner diameters (250 mu m, 320 mu m, 530 mu m) were also invest igated. In ail cases the higher rms values for surface roughness could be f ound at the beginning of the drawing process, although all values were clos e to atomic flatness.