We present a design for a sheath-flow cuvette that uses a relatively inexpensive quartz cuvette. The cuvette has a high optical quality square flow chamber that is fused to quartz tubes at each end. PEEK/TEFZEL fittings hold and seal the quartz flow chamber without putting strain on the cuvette. The performance of the cuvette is evaluated as a laser-induced fluorescence detector for capillary electrophoresis. The cuvette produces mass detection limits of 50 yoctomoles (30 copies) for 5-carboxyl tetramethylrhodamine (5 TAMRA SE) with a separation efficiency of 400,000 theoretical plates.