Improved colorimetric analysis of liquid samples is provided. A sample holder is used that delivers predetermined volumes of sample individually to each of several colorimetric test patches at the same time with a sliding action. An opaque housing is employed to prevent ambient light from reaching the test patches when color images of the test patches are acquired. Preferably, a mobile electronic device including a camera is attached to the opaque housing to acquire the images. Optical microscopy can be performed in addition to the colorimetric analysis.