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I am no chemist, but a biologist who knows some biochemistry. I have some natural extracts at limited quantity, which I have been evaluating using mainly GC-MS. These extracts are rich in liquid alkaloids.

I was wondering whether a trivial "Nanodrop" could help me in some analyses -- e.g. estimating concentration of some main compound --, via UV/Vis absorbance scans. A typical nanodrop can scan for absorbance within the range 200-800 nm.

Usually molecular biologists are the only ones routinely making use of Nanodrop, strictly for DNA/RNA purity and quantitative estimations.

Has anyone here ever tried making use of a Nanodrop micro-spectrophotometre for general analytical purposes with other compounds?

[UPDATE]

I cannot add an answer as others for some reason closed it as "too broad". It isn't, see below.


After completing my tests, I have decided to come back to answer my own question.

A Nanodrop machine has served my purpose quite efficiently, as far as I can judge. I used have used it to evaluate the degree of purity of a natural alkaloid extract from insects, using synthetic alkaloid analogues as controls. See our published paper discussing the method here, along with raw data.

We have noticed no alterations nor cross-contaminations to other DNA/RNA samples running in parallel, highlighting on the fact that the equipment was properly cleaned between each use (with 100% ethanol & distilled water).

Therefore, yes: I recommend using the Nanodrop as a cheap & quick method to scan alternative biological/chemical samples, provided the chemicals and solvents involved are compatible with the pedestal according with the manual.

Hope this discussion encourage others to dare into multidisciplinary research!

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closed as too broad by Mithoron, airhuff, Todd Minehardt, M.A.R., bon Feb 18 '18 at 8:39

Please edit the question to limit it to a specific problem with enough detail to identify an adequate answer. Avoid asking multiple distinct questions at once. See the How to Ask page for help clarifying this question. If this question can be reworded to fit the rules in the help center, please edit the question.

  • $\begingroup$ Why the downvote? $\endgroup$ – Scientist Feb 9 '18 at 3:13
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    $\begingroup$ I didn't down vote this, but I suspect this isn't quite the right forum for this question. A literature search would likely yield more fruitful results than waiting for a random analytical chemist who happens to have some expertise here. $\endgroup$ – Zhe Feb 10 '18 at 4:02
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    $\begingroup$ Could you tell us what a nanodrop is? $\endgroup$ – pentavalentcarbon Feb 10 '18 at 16:55
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    $\begingroup$ We got the Nanodrop One-C in our lab. We use it for example for quick determination of tetrazine concentration (strong absorbance at 535nm) or other dyes. It works well with water or DMSO but it's not very accurate in some cases. But if you don't care about some % up or down it does the trick. $\endgroup$ – DSVA Feb 11 '18 at 19:16
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    $\begingroup$ I think this is a great question. Thanks for posting it! $\endgroup$ – Curt F. Feb 14 '18 at 0:46
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In short, i would say that you cant use Nanodrop for such work. Here is why:

From a quick google search it appears that a nanodrop is a UV-Vis spectrometer that can measure very small amounts of liquid. Looks like that bio-sciences people (I am not a biologist or biochemist) use it to quantify nucleic acids by knowing the approximate molar absorptivity for DNA, RNA etc. at a specific wavelenth, measuring the sample's absorption at that wavelength, and applying the Beer-Lambert law assuming that the only compounds that absorb in the wavelenght that measurement takes place in their sample are the nucleic acids (which i guess is a fair assumption for such samples).

However, I am not sure from your question if you want to measure nucleic acid content in a sample also containing alkaloids as part of the sample matrix or you want to quantify the various alkaloids in your sample.

I think you must mean the latter since you mention GC-MS in which case the nanodrop seems to be a poor choice: UV-Vis spectroscopy in general is a technique with very low resolution in terms of compound separation due to the broadness of the peaks in the absorption spectra. If you had only a few alkaloids in your mixture (which i dont think you do) maybe you could use nanodrop or a normal UV-Vis spectrometer followed by a lot of calibration and absorption band decomvolution in order to identify and quantify each component. If on the other hand you have a complex mixture (which is usually the case with natural extracts) any kind of UV-Vis spectroscopy will fall short. Even NMR spectroscopy which has a much higher resolution would struggle.

This is why GC-MS seems to be the best way for such work: the GC separates the mixture in simpler mixtures (or in the pure compounds if your sample is not too complicated) and then the MS identifies and quantifies the compounds present in each fraction. So i think that you will either need to find more sample or further optimize your GC-MS method to increase sensitivity.

I hope this helps.

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    $\begingroup$ The part about the Nanodrop is not quite correct. We got the nanodrop One-C (drop and cuvette) which can measure every wavelength between 200 and 800nm, also full spectra and even time resolved. $\endgroup$ – DSVA Feb 11 '18 at 19:14
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    $\begingroup$ Ok, the model i looked up was setup with certain wavelenths only. I should have thought that there would be more advanced versions of it! I ll edit accordingly. Thank you. $\endgroup$ – AMM Feb 11 '18 at 19:21
  • $\begingroup$ Now we're talking. Thanks for your insights, though still I haven't found someone who's experimented with that. I still see the application of a Nanodrop towards my alkaloids as in the same situation of nucleotide analyses of molecular biologists. Both are natural extracts. I'd emphasise that when molecular biologists assume the only compounds absorbing in a wavelength in their sample the nucleic acids, they are usually not right. For most DNA extracts there are intrinsic and added contaminants. Likewise their molecules have many analogues like mine; I'd like to estimate [] and purity. $\endgroup$ – Scientist Feb 12 '18 at 5:29
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    $\begingroup$ You are trying to estimate how much alkaloids you have in total in your extract or which ones and in what amount of each? $\endgroup$ – AMM Feb 12 '18 at 9:14
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    $\begingroup$ AMM is absolutely right here, @Scientist: UV-Vis is a terrible technique when you have a complex mixture. There's no way you'd be able to speciate a natural extract, and the complex mixture means you have no ability to even guess at a reasonable molar absorption coefficient for the mixture. AMM's suggestion of a chromatography method hyphenated with mass spec is likely your best bet. However, your sample size may be too small for a realistic analysis. You've posed a terrifically challenging analytical problem here. $\endgroup$ – hBy2Py Feb 13 '18 at 21:58

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