An apparatus for measuring an optical property of a sample, the apparatus comprising: a. a swing arm; b. a light source; c. a first pedestal surface coupled to i) the swing arm and to ii) the light source; d. a magnet; e. a base plate; f. a mechanical stop coupled to the base plate; g. a spectrometer; h. a second pedestal surface mechanically coupled to said base plate and configured to receive a liquid sample, said second pedestal surface being coupled to the spectrometer, wherein said second pedestal surface is further operable so as to adjust a separation between said first and said second pedestal surfaces (13, 15) at a variable distance to pull said liquid sample into a column so as to be contained by surface tension, or to squeeze the sample during optical analysis, thereby providing an optical path for photometric or spectrometric measurement; i. a magnetic flux sensor located such that a null plane of north and south magnetic flux fields of the magnet is centered on the magnetic flux sensor while the mechanical stop is in physical contact with the swing arm, and wherein the magnet is coupled to the swing arm, and the magnetic flux sensor is coupled to the base plate or wherein the magnetic flux sensor is coupled to the swing arm, and the magnet is coupled to the base plate; j. a processor adapted to calibrate the point for minimum optical path length by utilizing a threshold magnetic flux field emitted from the magnet and detected by the magnetic flux sensor; k. a microprocessor configured to control an offset voltage of the magnetic flux sensor output; and l. an analog-to-digital converter configured to digitize the offset magnetic flux sensor output. a. a swing arm; b. a light source; c. a first pedestal surface coupled to i) the swing arm and to ii) the light source; d. a magnet; e. a base plate; f. a mechanical stop coupled to the base plate; g. a spectrometer; h. a second pedestal surface mechanically coupled to said base plate and configured to receive a liquid sample, said second pedestal surface being coupled to the spectrometer, wherein said second pedestal surface is further operable so as to adjust a separation between said first and said second pedestal surfaces (13, 15) at a variable distance to pull said liquid sample into a column so as to be contained by surface tension, or to squeeze the sample during optical analysis, thereby providing an optical path for photometric or spectrometric measurement; i. a magnetic flux sensor located such that a null plane of north and south magnetic flux fields of the magnet is centered on the magnetic flux sensor while the mechanical stop is in physical contact with the swing arm, and wherein the magnet is coupled to the swing arm, and the magnetic flux sensor is coupled to the base plate or wherein the magnetic flux sensor is coupled to the swing arm, and the magnet is coupled to the base plate; j. a processor adapted to calibrate the point for minimum optical path length by utilizing a threshold magnetic flux field emitted from the magnet and detected by the magnetic flux sensor; k. a microprocessor configured to control an offset voltage of the magnetic flux sensor output; and l. an analog-to-digital converter configured to digitize the offset magnetic flux sensor output.