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neptunium
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NMR ? no but MS yes
have you checked that one out ?
http://www.sciencemadness.org/talk/viewthread.php?tid=23422&...
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DistractionGrating
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Quote: Originally posted by aga  |
Personally i am thinking more along the lines of USB webcams (or similar) which are generally CCD, cheap, and sensitive to both visible and IR spectra
if you remove the IR filter.
[Edited on 14-4-2014 by aga] |
I believe that CCD webcams have limited sensitivity into the NIR range, up to only about 900 - 1100 nm. Most NIR specs cover a range beyond that,
more like 1100 nm up to around 1700-1900 nm. Usually InGaAs, Ge, or PbS detectors are required for that wavelength range, as far as I can tell.
I'm new around here, but have a strong desire to build a NIR spec. Please see my newly created thread about it here: DIY NIR Spectrometer?
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aga
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Specs on the sensors used in cameras are hard to find, as they tend to just say 'colour' and 'lo-lux' etc.
I have a couple, and will try to find some markings on them to identify the chip, and then try to get some specs.
There was one time i ordered two cameras (for FPV), and the supplier asked if i wanted the 'colour correction infra red filter' removing, which
suggests that IR sensitivity exists in these units, and a filter is needed to correct the colour responses.
Can i assume that NIR gets refracted by a prism ?
Update on Sources of Parts :-
I took a 3.5" hard drive apart today, and punched down thru a hole to see what happened.
After full disassembly, it seems i broke one of the two platters.
It is Glass (or some ceramic that shatters like glass).
It is also coated with a metal substance, is extremely Flat, and most likely mechanically stable over vast temperature and acceleration ranges.
It's a 'perfect' mirror as far as i can tell.
Stick it next to a surface and there is no perceptible 'ghosting' or colour difference in the reflected image when compared to the image seen
normally.
The chassis is anodised aluminium, but is rather small for my idea for the mel-temp.
A larger, older (5") hard drive chassis will probably serve well.
2 for 1 week in the electro-garbage if this idea works !
(also a 'no reserve' auction for 20 dental size #5 front-coated mirrors)
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Baffled
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A good old Thiele tube goes a long way, if you have a accurate scale you can even calculate the molar mass (with a certain margin of error depending
on your scale) using freezing point depression:
http://www2.vernier.com/sample_labs/CWV-15-COMP-freezing_pt_...
I have one of these: http://potassium.1338.at/upload/pictures/schmelzpunktbestimm...
The silicon oil (some high boiling PDMS) that goes with it is terribly expensive, but it works!
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Mildronate
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Yes its crioscopy there is also ebuloscopy (boiling point depresion). But there is only one problem you must have very clean chemicals.
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aga
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Still waiting for parts to arrive. Spanish Postage is not so fast.
I was wondering if this thread should be closed, and any useful efforts moved over to Radegast's thread, seeing as Rad actually has something built
and working, whereas this one is still just talk.
What i will attempt to build is an accurate spectrometer using cheap parts (when they arrive) which will be computer controlled and self-calibrating
if possible.
The detector will be a ccd camera of some sort, and as i have seen mention of time-synchronisation being useful somewhere, in relation to
irridescence/flourescence, my current thinking is to synchronise the laser pulse with the line-synch pulse of the camera, which is once every 64us.
Clearly the laser pulse duration and time offset will need to be varied and experimented with.
The notion of a polarimeter is interesting, so i will include the possibility of analysing the reflected, but polarised laser light reflecting off the
sample, passing through a rotationally-adjustable second polarising film.
Looking at the constructional possibilities, i would hope that this will end up as a hand-held unit which can be pointed at a substance, and read out
the composition, although i appreciate that will be a Tall Order.
The Melting Point aparatus seems trivial. USB microscopes are available for a few $, so all that is really required is a heating element, a block of
aluminium with some holes in it, a digital thermometer and a temperature/heating controller, so i suggest that it be spun off as a separate project,
unless anyone can suggest a valid reason that MP would be a clincher in determining the composition of a substance.
My only objection to MP is the sheer energy required to raise the temperature, and so not a hand-held device.
Does anyone have any suggestions regarding the quantitisation of the detected substances : i.e. work out how much of each there is ?
[Edited on 28-4-2014 by aga]
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Mildronate
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You need standart solutions for quantitative analysis, analitycal balances and A class volumetric flasks 10, 15, 25, 100, 250 mL more than one of
each.
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Blue Matter
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Semi off topic but you might find this interesting.
https://www.kickstarter.com/projects/903107259/scio-your-six...
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aga
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Bang on topic !
That's amazing.
Game On i guess. A Prism & some lenses arrived today, along with the heating elements for the MP thing.
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Etaoin Shrdlu
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I really don't like that they won't show the spectra. Why? That should be something they are eager to allow people access to (and also the
simplest part of the data to grant access to).
Otherwise, that device is quite cool. So small and accessible, too. I'm excited to see how this plays out.
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Blue Matter
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"We will consider providing access to the raw spectra to specific users according to their needs."
I suppose if you shell out the cash you can get a model that shows the raw spectra?
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aga
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SCIO Pro i guess @ $15,000
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Mildronate
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I actualy interesting about polarograph building, its very interesting method and more possible at profesional level @ home than diY FTIR or NMR
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Blue Matter
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out of curiosity how many people are actually planning on building one in this thread?
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Mildronate
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I am planing polaragraph  Actually i have polarograph, but i doesn't have
droping mercury electrodes for it, mercury is not a problem, problem is electrodes design.
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The Volatile Chemist
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I'm interested! At least a spectrophotometer of sorts.
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aga
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measuring the spectral response is the key.
all the rest is applying a stimulus and factoring it out of the reading.
So, spectrometers all the way..
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The_Taxidermist
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Brewing Analysis
Interesting topic, and responses. Being new, and a subject dear to my heart, I note that there is an element of discussion missing, which I can fill
in. What type of analyses for brewers/homebrewers are there (should there be) in use?
Malt Analysis, provided per request as a sheet from the malt supplier.
Water Analysis, as provided, usually, by the Supply Company.
Sensory Analysis, as evaluated by the brewer and friends.
Colour Analysis, also as provided by brewer and friends.
For the (uber-keen and closet "mad scientist" in us all) hobbybrewer, this site outlines various instrumental techniques for analysing beer; Advanced Analytical Methods...for Beer
Beer Analysis (Molecular method of plant analysis) The Index to the book gives a good listing of various analyses;
and for Beer color determination, this from Lovibond Tintometer
Beer Colour is mostly judged by eye using beer color swatches and takes some practice and training to learn. Lovibond made a series of glass filter
disk standards (€137/disk 4 to the complete set) for their Lovibond 1000 Comparator system (now more or less superseded by newer tech, but still
supported) and was aimed at laboratory use. I have one of these but not the specific disks.
From my observations, analysis for bitterness and alcohol concentration would be desirable goals. NIR for fermentation analysis would be cool. We
already have specific gravity or refraction for sugar conc. Do we want to analyse how viable our ageing hops are? You bet! Do we want to check the
quality of our 1-2 year old (rodent/pest free) grain storage? Of course. But as a first step, for me, final beer colour is potentially accessible.
I myself have been slooooooly working on a 413nm transmission colorimeter that fits into the size of an iPhone 5 size-like packaging box, I have most
of the components an idea for the circuit but am missing one key element - basically I can't decide on the right Log Amplifier and am suffering
sticker shock around the one I thought would be best.
Also in short time, I'll be pulling up sticks and moving to Shanghai so al current project have been put on hold.
Good luck with this concept? I'd love to see more ideas about what we can hobbybrew-erise into stand-alone labtop instruments, that don't cost a
fortune, are easily diy-accessible, and produce satisfactory results – think 'food grade' reagent, as opposed to 'Analytical Reagent' grade. AR is
great, don't get me wrong, but as a hobbybrewer, FG would be exemplary, if I could only actually get it.
Last point, some of the Kickstarter ideas getting around, rely far too much on proprietary clouds to drive them. Whilst being networked is a nice
idea, I don't think I need some cloud system to drive an instrument, analyse the output, or store it for my personal data safety.
That's a bit like the doctor emailing me the results of my latest stool analysis when I didn't even know they'd already been storing and logging the
samples.
I think I can manage quite well without the implied beneficial extras. Simple instruments with a readable display, and a lab book. What ever happened
to the K.I.S.S Principle?
Cheers.
[Edited on 9-1-2017 by The_Taxidermist]
[Edited on 9-1-2017 by The_Taxidermist]
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bobm4360
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Cason's"Laboratory Text in Organic Chemistry", 2nd edition; and Amateur Science column in "Scientific American", September, 1967, have detailed info
on constructing gas chromatographs.
Regards,
Bob
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tsathoggua1
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For comparative analysis, wouldn't a simpler way to go about mass spec, use of the calutron principle? only, separating ionized compounds rather than
isotopic fractionation.
Might be interesting to try and build one even if it would be a shit for quantitative analysis (here, I am thinking comparisons via building up a
sample reference library, tedious and not exactly cheap, but say one could (just for example, using familiar examples) scan benzene, halobenzenes,
2,5-dimethoxybenzene, 4-substituted 2,5-dimethoxybenzene, then the benzaldehydes, equivalent phenethylamines, amphetamines and cathinones (the last
could be especially useful perhaps, and then scan similar ketones without the amine functionality, such as propiophenone and substituted
propiophenones, or for that matter, halomethanes, haloethanes, ethers, to build up a library.)
Of course such an approach depends on having a reference library.
Although such for specific areas of interest could be built up with relative ease, and especially for solvents.
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Chemetix
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I have a soft spot for LC, I think that a back yard version could give some repeatable reliable performance. It's not HPLC and it's not going to give
you the reliability of an alliance, but a low pressure pump some glass tube and a photodetector made from a pair of LEDs could make a fairly simple
system. Some have some pretty sort wavelengths these days. Ok it's not 254nm but it would show some absorbance from the baseline. With a clean sample
you might get the 3:1 signal to noise you need.
As for backyard reverse phase media...not calling this a success but I poked around with wax coated starch and packed a column with it. Caffeine gave
a reliable curve from methanol water, the detector was a hacked Waters 486 with a germicidal lamp as a UV source. But there are so many detection
systems that could be exploited.
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