1. If in doubt about the prism cleanliness, clean and dry prism with distilled/deionized water/alcohol. Previous sample residual and distilled/deionized water carryover will affect the results.2. Put approximately 1 mL beverage sample directly on the prism (enough to completely cover the prism, but not enough to overflow the prism area.) 3. Make sure all air bubbles and pulp is removed from the sample.4. Close the top if equipped. Wait about 20 seconds for temperature stabilization.5. Take Brix reading per manufacturer’s instructions if using temperature compensation mode.6. After reading, rinse prism with distilled/deionized water and/or alcohol and dry with lens tissue.7. If not in temperature compensation mode, check the temperature on the refractometer. If temperature is 20.0C (68F), then Brix reading is correct. If not, a temperature correction factor must be applied. These corrections apply only to instruments that have been zeroed with distilled/deionized water at 20.0 C (68oF).8. Periodically check the instrument calibration with distilled/deionized water and sucrose standard solution to prevent refractometer from drifting out of calibration.Refractive index is very sensitive to sample temperature; therefore temperature control is critical to obtaining good measurements. If features such as constant temperature water baths and automatic temperature compensation are not available, then refractometer readings must be corrected for temperature. The chart below illustrates the strong dependence of refractive index on temperature.
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