Nanoliter osmometer and method of operation

A method for measuring a temperature at which a phase change occurs in a sample, with an apparatus including a temperature sensing device for sensing a temperature of the sample held in a sample cell to provide direct collection of the sample from a sample source which is collected and retained at a collecting end thereof by capillary attraction between the collecting end and the sample, the sample cell including a longitudinal passage extending from the collecting end to a far end through which light is transmitted to provide an image of the sample retained at the collecting end of the passage with a cross sectional area of the passage being greater at the far end than at the collecting end, a heating and cooling assembly including the temperature sensing device which holds and thermally contacts the sample cell during determining the temperature at which the phase change occurs by the temperature sensing device at which the phase change occurs while the sample is retained at the collecting end, an illumination system for directing a light beam to the collecting end, through the sample, through the longitudinal passage and out of the far end to permit viewing of the sample to determine the temperature at which the phase change occurs comprising the steps:

• positioning the collecting end of the sample cell in contact with a source of the sample to collect the sample by capillary attraction;
• positioning the sample cell in thermal contact with the heating and cooling assembly;
• cooling the sample within the sample cell to cause a first phase change in the sample by refrigerating the sample with the heating and cooling assembly;
• raising a temperature of the sample within the sample cell with a controlled temperature gradient provided by the heating and cooling assembly to cause a second phase change in the sample;
• illuminating the collecting end of the sample cell with light from the illumination system during the raising the temperature of the sample to direct light through the collecting end, through the sample, along the longitudinal passage and out of the far end to provide an image of the sample;
• viewing the image of the sample from the far end to visually detect when a first phase change occurs upon freezing and a second phase change occurs upon melting the sample being completed by the application of the controlled temperature gradient;
• and
• determining the temperature sensed by the temperature sensing device when the second phase change caused by raising the temperature of the sample has occurred.