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Questions related from Duri Eun
Can anyone explain this method? Especially the last statement where it says only at 1.5 to 2.5mins was the MS/MS connected to the UPLC. How is that possible, is it a feature in this specific...
12 August 2024 9,326 3 View
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 4,516 0 View
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 7,535 4 View
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 1,326 5 View
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 9,461 4 View
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 462 1 View
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 334 3 View
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 2,220 2 View
I am going to do a solid phase extraction as the sample clean up prior to lcms analysis. My HPLC conditions are: C18 column, solvent system: 5% Formic acid & Methanol. But since I cannot...
05 July 2022 6,908 0 View
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 1,392 1 View
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 8,624 1 View
I am currently doing a research on targeted polyphenol profiling of one plant from different locations. Together with this i am going to test their antioxidant activities as well. I am confused if...
08 April 2022 2,003 5 View
I will be conducting the TBARS asay and it says to use BHT as the positive control. However, upon checking primary and secondary reference standards of BHT is too expensive. Can I use a food grade...
07 March 2022 7,432 1 View
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 7,902 7 View
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 399 4 View
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 7,764 3 View
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 7,456 0 View
I cannot find sources which gives a thorough explanation of PCA and how to assign the principal components 1 & 2 including their computations. Say for example, my study will explore polyphenol...
04 November 2021 7,427 3 View
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 4,779 5 View
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 4,274 3 View
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 9,232 2 View
Can collision gas be used in regular LC-MS (not any tandem MS) ?
22 October 2021 3,381 4 View
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 999 5 View
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 2,797 3 View
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 1,925 5 View
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 7,261 4 View
