Duri Eun

21 Questions 3 Answers 0 Followers

Questions related from Duri Eun

What to do when the autosampler needle was lowered, it hit a foreign object causing excessive force to be exerted to it?

I suddenly got an error on our HPLC system saying : when the autosampler needle was lowered, it hit a foreign object causing excessive force to be exerted to it. What could have possibly...

28 July 2023 4,287 0 View

How to compute FRAP value?

I am confused on how to present my data on the Ferric reducing antioxidant power FRAP assay. I have prepared my samples on a concentration range but i do not know how to present in percentage to...

01 November 2022 7,309 4 View

How do you get an extraction percent yield using dry weight?

May I know how to compute for plant extraction yield with regards to its dry weight? For example, I used fresh samples with 80% Moisture content. 150g leaves were macerated and the total extract...

18 October 2022 1,102 5 View

Can I quantify a certain compound using HPLC if I keep getting merged & splitting peaks?

I have a problem with my HPLC analyses. I keep getting split peaks and I am not sure if I can quantify those compounds. I do have reference standards and I should do a calibration curve to be able...

13 October 2022 9,233 4 View

What are the appropriate DPPH and FRAP assay values?

Why is DPPH expressed as IC50 and not EC50? Or could they be used interchangeably? Also for FRAP assay I am confused as some studies used EC50 and some used Ferrous Sulfate equivalents. Which...

18 September 2022 245 1 View

Should TFC always be lower than TPC?

I am getting the total phenolics content and total flavonoids content of a sample. Should the TFC be always lower in value? I know that flavonoids are prt of phenolics but since the protocols and...

21 August 2022 117 3 View

How to quantify compounds in LC MS?

Im curious as to whether the software for LCMS (Labsolutions from Shimadzu) already has a quantification feature or do I have to compute and compare the AUCs to the standards manually? If so, what...

05 July 2022 2,000 2 View

How do you keep sa sample frozen during lyophilization?

I am having a hard time with freeze drying as the water extracts melts quickly during lyophilization. I do not know what to do or if something is wrong. The sample is purely a water extract of...

11 May 2022 1,157 1 View

How to prepare 20mM FeCl • 6H2O?

I will be using the solution for the FRAP assay. How is this prepared and how long can it be stored? Is it sensitive to light?

10 May 2022 8,562 1 View

How many mg of standard would i need for an LC MS analysis?

I will be buying a reference standard fpr my LC MS analyses. Most of he standards in sigma aldrich is available in 1 mg only. I am not sure if this is enough for my LC-MS analyses. At what...

05 November 2021 7,853 7 View

For biological replicates, do i still have to analyze each biological replicate in triplicates?

It says in the manual that for metabolomic analyses, we should use biological replicates instead of the regular replicates. I am just concerned if even though i already have 3 biological...

05 November 2021 339 4 View

What mass analyzer should I choose for LC-PDA-ESI-MS?

I am confused about the method I found in the study. It does not state the type of mass analyzer I should use. Please help me understand this method: Flavonoid analyses from FIII and from...

05 November 2021 7,699 3 View

What is the difference between sheath, auxillary, drying, and nebulizng gas in a mass spectrometer?

What is the difference between sheath, auxillary, drying, and nebulizng gas in a mass spectrometer? Should I make sure that I have all these types of gases for polyphenol analysis via...

05 November 2021 7,143 0 View

Do I still need a positive control for DPPH assay if I intend to get the EC50?

I am confused if I still need to use a positive control (i.e quercetin) for my dpph assay. I will be presenting the values in EC50 and i do not know where should i use the positive control for.

03 November 2021 4,718 5 View

How do I prepare the 500 microM DPPH in ethanol?

Here is the procedure i am following for the DPPH assay. I am not sure on how do I prepare the 500 microM DPPH in ethanol like how many mg of DPPH should be dissolve to get this molarity. I am...

03 November 2021 4,228 3 View

How much is the Umetrics SIMCA software? ae there alternative softwares that are cheaper or free?

I am planning to use PCA and OPLS DA for my study in biochemometrics but i quite tight on budget. I am not sure how much is the SIMCA software although they have a trial version, I am worried if...

26 October 2021 9,180 2 View

Is collision gas only used for tandem MS?

Can collision gas be used in regular LC-MS (not any tandem MS) ?

22 October 2021 3,328 4 View

Can you recommend me any LC MS books I can study as a beginner?

I need to study about LC MS since I will be using it for my thesis. I know nothing beats practical application but physical classes are not going to start anytime soon i need to equip myself with...

14 October 2021 949 5 View

What are arbitrary units in LC-MS analyses? How do we measure it?

This is an excerpt from the paper of Gustavo Costa et al., 2015. I am not sure what is the meaning of arbitrary units and how do I translate this to flow rate in volume per minute. "Mass analyses...

14 October 2021 2,739 3 View

Can I directly inject the methanol extract to LC MS analyses?

I have 2 samples extracted with different solvents. One is water and one is methanol. Can I directly inject the methanol extract to LC MS analyses? And since I have to lyophilize the sample from...

14 October 2021 1,879 5 View

Choice of standards for TPC and TFC

Why is gallic acid for TPC and quercetin for TFC the standards used in these assays? All studies I have come across use Gallic acid equivalents and quercetin equivalents to express TPC and TFC...

01 January 1970 7,201 4 View