As a precision measuring instrument, the cleanliness of capillary viscometer directly affects the accuracy of rheological experiments. Residual samples, solvents, or microorganisms not only clog capillaries, but also lead to repeatability errors. This article will summarize a phased cleaning plan based on laboratory experience to help researchers efficiently restore instrument performance.

　　1、 Preprocessing: Physical removal of residues

After the experiment is completed, an appropriate amount of cleaning solvent (such as acetone or ethanol) should be immediately extracted with a syringe to rinse the pipeline, in order to prevent the sample from drying up and solidifying. For stubborn residues, the "segmented backwash method" can be used: invert the viscometer, slowly inject solvent from the outlet end with a syringe, and use the pressure difference to push the sediment out of the measuring end. If encountering oily pollutants, soak in petroleum ether for 10 minutes first, and then shake with an ultrasonic cleaner for 3 minutes, but pay attention to controlling the power (recommended not to exceed 50W) to prevent capillary deformation.

　　2、 Deep cleaning: chemical dissolution and ultrasound synergy

Corresponding solvents need to be matched for different pollutants:

1. Proteins: 0.5% pepsin solution (pH 2.0), sonicated at 40 ℃ for 15 minutes

2. Polymer residue: Soak in a 1:1 mixture of xylene and toluene at room temperature for 2 hours

3. Inorganic salt crystallization: Rinse with 5% dilute nitric acid at room temperature for 30 minutes

Attention should be paid during operation:

1. The solvent level should cover the capillary measurement section

2. Select the 40kHz low-frequency mode for ultrasound frequency to avoid damage to the scale lines caused by high-frequency cavitation effects

3. After each stage of cleaning, rinse with deionized water three times to prevent cross contamination

　　3、 Final processing: drying and validation

Adopting the "gradient drying method" to prevent water marks:

1. First, blow the pipeline with compressed nitrogen gas (pressure ≤ 0.2MPa)

2.60 ℃ vacuum drying oven treatment for 2 hours (vacuum degree -0.09MPa)

3. Let it stand at room temperature for 4 hours to reach natural equilibrium

The cleaning effect can be verified through:

1. Visual inspection: The inner wall of the capillary tube should be free of oil and water stains when observed against a black background

2. Blank test: Repeat the measurement 3 times with a standard solution (such as castor oil), and the CV value should be ≤ 0.5%

3. Infrared spectroscopy: detecting peak intensity of residual organic compounds (optional)

Maintenance suggestion: Establish a cleaning archive to record solvent types, processing times, and validation data; Perform capillary inner diameter calibration every quarter; Fill with inert gas and seal away from light during long-term storage. By standardizing the cleaning process, the service life of the viscometer can be significantly extended, ensuring the traceability and reliability of experimental data.