No, it's not possible to get negative values for total phenolic content. The total phenolic content measures the amount of phenolic compounds in a sample, which is always a positive number because you can't have less than zero of these compounds. If you see a negative value, it might be due to an error in the measurement process or data entry. Potential reasons for obtaining negative values: 1. Blank Subtraction Errors: -Incorrect subtraction of the blank sample can lead to negative values. -Ensure the blank is properly prepared and its absorbance is correctly subtracted from the sample readings. 2. Calibration Curve Issues: -Errors in preparing or using the calibration curve can lead to incorrect TPC values. Verify that the calibration curve is correctly plotted, and the equation used to calculate the TPC is accurate. -Ensure the standard solutions for the calibration curve are prepared correctly and their absorbances fall within the linear range of the curve. 3. Sample Preparation Errors: -Inaccurate dilution or errors in sample preparation can affect the results. Double-check the volumes and concentrations used in the assay. -Ensure that the samples are homogenized properly and that no particulate matter could scatter light and affect absorbance readings. 4. Reagent Issues: -Degradation or contamination of reagents can lead to erroneous results. Verify the quality and expiration dates of the reagents used in the assay. -Ensure the reagents are prepared fresh and stored under appropriate conditions.

Sorry I'm not really familiar with that assay

The concentration in mg/mL is calculated by dividing the amount of sample (in mg) by the volume of the solvent (in mL). Concentration = Amount of Sample / Volume of Solvent = 50 mg / 2 mL = 25 mg/mL Therefore, the concentration of your stock solution is 25 mg/mL. Hope this helps 😀

I apologize for the confusion; my student used a different term. The blank you understood is actually the "control" as shown in the video. The blank should be treated the same as the standard and samples, but instead of using 2 mL of the sample, you use 2 mL of the solvent, eg MeOH, that was used to dissolve your sample. The purpose of the blank is to subtract the absorbance caused by the reagents. In the video, my student was just noting the differences in absorbance between the 'blank' and the 'control'. In conclusion, the control shown in the video is the BLANK BLANK = solvent (without sample) + reagents hope i'm answering your question 😊

@@NaturalProductThings thank you for the clarification. This was really helpful

1. First Dilution (1/2): - You took a portion of your original solution and added an equal amount of solvent. This means the concentration of your solution is now half (1/2) of what it originally was. 2. Second Dilution (1/25): - From the solution you made in the first dilution, you took a portion and mixed it with 24 parts of solvent. This means the concentration is now 1/25 of the first diluted solution. To find the total dilution factor, you multiply the dilution factors of each step together: Total Dilution Factor = (First Dilution Factor) x (Second Dilution Factor) So: Total Dilution Factor = (1/2) x (1/25) = 1/50 This means your original solution is diluted 50 times in total. To find the original concentration: If you have a measured concentration after dilution, you can find the original concentration by multiplying the measured concentration by the total dilution factor. Example: - Let's say you measured a concentration of 2 mg/mL after dilution. - The original concentration would be: Original Concentration = Measured Concentration x Total Dilution Factor Original Concentration = 2 mg/mL x 50 = 100 mg/mL So, if your UV results gave you 2 mg/mL after the dilution, the original concentration of the phenolic content in your sample was 100 mg/mL. I hope I'm answering your question 👉👈

You're welcome ☺

So nice of you <3

The standard error of the mean (SEM). Calculating the SEM with 3 replicates provides a basic estimate of how much your average result might differ from the true average if you repeated the experiment many times, which helps you understand how reliable your findings are.

Glad it helped!

You're welcome :) yes, that is true. Multiply the TPC value by 100 to get the amount per 100g of extract. eg: TPC (mg GAE/g extract) × 100 = TPC (mg GAE/100g extract) 112 mg GAE/g extract × 100 = 11,200 mg GAE/100g extract

you're welcome ! all the best for your studies :)

May I ask what CD you are referring to?

@@NaturalProductThings critical difference

Critical difference as that in anova table for Randomized Block Design

Do you mean how I got the weight of the dry extract? Watch at 2:53 to see how I calculate the weight of the extract in g. 1. You need to know the concentration of the extract used for the reaction. 2. For example, I used 0.1 mg/mL (concentration) of the extract, which means 0.1 mg of the extract was dissolved in 1 mL of methanol. So, the mass of the extract here is 0.1 mg. Convert 0.1 mg to g, which means the weight of the extract used to determine the TPC per 1 mL is 0.0001 g. 3. The volume of the extract used doesn't matter to find the dry sample's weight because the part where you need the volume is 'v' as in the formula. I hope I'm answering your question.