Fast Inspection of Quality of Indigo Naturalis by Multiple Light Scattering

The protocol can accurately and rapidly assess the quality of Chinese medicine without altering the nature of the sample or using organic reagents. They main advantage of this technique provides a fast, accurate, and method for quantity evaluation and supports the development and the transformation of high quality Chinese medicine. We believe that this method will be helpful in the field of traditional Chinese medicine quality control, particularly in the assessment of authenticity.

Begin by selecting four distinct batches of Indigo naturalis herbal powder for testing. For each sample, pass it successively through the seventh and ninth sieves and collect the powder that remains between these two sieves. Now accurately weigh 0.2 grams of the collected powder on a piece of weighing paper and set aside this measured quantity for later use.

Next, set up an iron support stand and place an iron ring with a five centimeter diameter funnel on top of it. Pipette 20 milliliters of pure water to the sample glass bottle, then place the sample glass bottle directly under the funnel, ensuring the lower edge of the funnel aligns with the mouth of the bottle. Release the sample at a height of 80 centimeters from the lower edge of the funnel, allowing it to slide freely along the funnel and into the sample bottle.

Turn on the Turbiscan lab instrument and allow it to warm up for 30 minutes. Click on the New File button at the top menu to create a new empty measurement file. Click on the Turbiscan lab temperature icon in the top menu to set the instrument target temperature to 25 degrees Celsius.

Next, click on Programmed Analysis to enter the setup analysis program. Add the program to the list. Then input a 10 minute task duration with 30 second task periods as a cycle and 21 scans into the analysis sequence within the taskbar.

Place the prepared sample vial into the measurement system. Once the program has been set up, click on Start to begin measurement. After data acquisition, click on the list of calculated parameters to automatically calculate the Turbiscan stability index.

High quality Indigo naturalis showed the same light transmittance at all heights within 0 to 10 minutes. The transmittance of common Indigo naturalis showed slight fluctuations over time. Fake Indigo naturalis products showed a rapid decrease in transmittance with significantly lower light at the bottom of the sample bottle.

Inferior samples showed stable transmission at zero time, which decreased over time. The back scatter of stable samples one and two showed little to no fluctuations, whereas unstable samples three and four showed sedimentation-derived turbidity. High Turbiscan stability index values were observed in samples three and four, indicative of instability.

However, the slopes of samples one and two were close to zero. A key step in the process is that the glass bottle containing the sample should be moved inside the sample tank as quickly as possible while avoiding shaking