MicroBore (1 mm id) columns are a good choice when sample sizes are limited. They will improve detection limits 5 times over 2.1 mm id columns when the same sample mass is used. This increase in sensitivity can be critical. MicroBore columns use low flow rates (typically ~50 µL/min). Therefore, these columns are ideal for use with detectors requiring low flow ratessuch as some mass spectrometers. MicroBore columns perform optimally with HPLC systems purchased or modified for microboreuse. Guard columns are now available with an adjustable tube stop depth to provide a perfect zero dead volume connection every time.