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Author Topic: Chemical Identification of an unknown alkali  (Read 49570 times)

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Alpha-Omega

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Re: Chemical Identification of an unknown alkali
« Reply #15 on: January 01, 2008, 03:48:50 PM »

Can you tell me exactly what you are looking for?  If you want an exact ID you need to use elemental analysis.  Thhat would be ICP...ok not an option...AA is a good second....that will give you any metals in there...XRF is x-ray fluorescence.  It is used for qualitative and quantitative id of any lemental substance from Na (Z=11) to PU (Z=92) in the periodic table.

There are two versions of XRF...WDXRF and EDXRF...wavelength dispersive and energy dispersive.  WDXRD relies on optics and not the detector.  EDXRD relies heavily on the detector and all spectra can be displed in terms of wavelength as well as in terms of energy.  See www.panalytical.com....or www.bruker.co....they give all the theory and many applications...it is used extensively in forensics...which is where I got my taste..and in pharm...

I can certainly tell you ablout detection of cations and anions...IC Ion Chromatography is your #1 bet...and I work for the leader in IC analysis....

Go to www.dionex.com....on the homepage go to upper right hand corner  go to search...type in cations and many hits for literature will come up.....do the same for cations....

Now it is impt regarding matrix...what you are going to want to look at....for common anions EPA uses AS14 and AS14A columns...or AS4A, AS9-HC and sometimes AS11 and AS11-HC.

Cations they use CS12, CS12A, CS5..

You can also check out the Metrhome site...

Borek is correct spot tests are just that an initial ID used them all the time at US Customs....was a Forensic Chemist there for 5 years....BUT you must validate...with an absolute qual/quant method void of false pos/neg results....and that would require instrumental analysis.

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Edward

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Re: Chemical Identification of an unknown alkali
« Reply #16 on: January 01, 2008, 04:11:00 PM »

Thanks Alpha-Omega.  I suppose my lab doesn't have the equipment you mentioned except Atomic absorption.  We are looking for a protocol to detect any unknown substances that come to us and that is an acid/ base measured by a pH meter.  My lab is a clinical toxicology reference lab and we usually receive samples from patients with clinical problems usually after ingestion or contact with household products.  Spot test and AA are probably what we have got.  From your expert forensic knowledge, could you pls suggest any references or protocol ?
Grateful for your *delete me*
« Last Edit: January 16, 2012, 08:45:26 AM by Arkcon »
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Alpha-Omega

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Re: Chemical Identification of an unknown alkali
« Reply #17 on: January 01, 2008, 04:34:06 PM »

Metrohm has some titrimetric apps for cations:  phosphate, chloride, flouride, sulfate....not sure if you are using an autotitrator:

http://www.analysis-food.com/beverage/beer.html

This is a good pdf for titrimetric analysis of a few differnt types of species.....you can download the pdf

http://oncampus.richmond.edu/~rdominey/301/local/Titrimetry_Methods.pdf

You can do very good elemental analysis via AA....what OEM is the AA? 

If you go to their website and are an owner...you should be able to register and get access to their applications...
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Edward

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Re: Chemical Identification of an unknown alkali
« Reply #18 on: January 01, 2008, 05:07:54 PM »

Don't know if my concept is right or not.  Is that titration kit fit for determination of any acids and bases known?  Is it expensive to buy one (we don't have autotitrator)? 
We've got a Varian SpectrAA800.  I just have a quick glimpse of the company website and have not found any application related to id of macro quantity of acid /base/ cation and anion.  Afraid that will damage the analyzer.  Maybe I can ask the company for more information.  Is a preliminary titration method and AA confirmation of possible cations a sufficient approach?  How about the species other than metal which are ?not detectable by AA?
Thanks!
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Alpha-Omega

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Re: Chemical Identification of an unknown alkali
« Reply #19 on: January 01, 2008, 05:15:35 PM »

Hang on...let me do a few things...are you with Truman College downtown Chicago??
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Edward

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Re: Chemical Identification of an unknown alkali
« Reply #20 on: January 01, 2008, 05:18:30 PM »

No, I work in a Hospital of Hong Kong.
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Edward

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Re: Chemical Identification of an unknown alkali
« Reply #21 on: January 01, 2008, 05:19:37 PM »

Please take your time and really appreciate your great *delete me*  Don't know if I can leave email here?!
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Alpha-Omega

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Re: Chemical Identification of an unknown alkali
« Reply #22 on: January 01, 2008, 05:23:46 PM »

If I go to http://www.varianinc.com/cgi-bin/nav?applications/aa&cid=JMJMQHLNFM  all of the Application Notes Varian offers are on the left.

Click on AANow you have to choose your search criteria

By Martix/Application
By Element
By Title

In this case I would choose Element....maybe matrix...do you know the matrix of your sample(s)?  Wher do they come from?  What is their origin?  For example, if you had groundwater samples I would imagine they would be tainted with mineral deposits and trace metals...like iron....this will definitly produce interferences in a method like IC.  The sample matrix has to be accounted for....

Try this...these are Applications....they give you a guideline to follow....basically it is an application designed for a specific analysis by Varian known to work on thier AA system....
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Edward

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Re: Chemical Identification of an unknown alkali
« Reply #23 on: January 01, 2008, 05:41:23 PM »

The specimen types can be diverse.  But most frequently, some drain cleaner (acids or caustics), soap powder, detergent.
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Edward

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Re: Chemical Identification of an unknown alkali
« Reply #24 on: January 01, 2008, 05:53:22 PM »

Away for an hour or so.  Please keep sending messages here   Thanks!
« Last Edit: January 17, 2008, 05:24:33 AM by Edward »
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Alpha-Omega

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Re: Chemical Identification of an unknown alkali
« Reply #25 on: January 01, 2008, 05:54:13 PM »

Basic and contain surfactants....I would choose elements...go thru those steps and check those notes...
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Edward

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Re: Chemical Identification of an unknown alkali
« Reply #26 on: January 01, 2008, 05:55:20 PM »

Sure! 
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Borek

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Re: Chemical Identification of an unknown alkali
« Reply #27 on: January 01, 2008, 08:37:47 PM »

Do you have references for a more comprehensive systematic analysis of cations and anions?

Only in Polish :)

Quote
For acids identification, is it possible to use titration method to determine their identity?  From titration with NaOH, is it possible to obtain molar mass and pKa?  From these data, can I identify all existing acids?  Are there any good references on this?

Not molar mass but equivalence mass, and pKa only for acids with pKa > 3 (approximately).

Vogel's Quantitative Chemical Analysis comes to mind.
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Edward

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Re: Chemical Identification of an unknown alkali
« Reply #28 on: January 02, 2008, 04:38:37 AM »

I am thinking to perform an acid base titration, then use systematic inorganic qualitative analysis by different solubilities in acids, H2S, NaOH, then Na2CO3 to detect cations.  But I don't know if this approach covers all acids or bases.  I don't know know if this approach covers all organic acids, either.
For titration experiment, is there a complete list of acid and base identification by equivalence mass and pKa/pKb? 
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Edward

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Re: Chemical Identification of an unknown alkali
« Reply #29 on: January 02, 2008, 04:39:00 AM »

If pKa or pKb is unique, together with equivalence mass, is it possible to deduce the identity of an acid or base respectively?  If I don't know whether the substance is inorganic or organic, can I approach it by assuming it is inorganic, i.e. use systematic inorganic qualitative analysis for cation and anion.  Then perform acid base titration to confirm.  If I can't identify any known inorganic ions or inorganic base/acid (?at least some organic acids may also be identified by acid base titration)by these methods, I can treat the sample as an organic substance.  But there are limitless possibilities of organic substances in this world!?  Maybe I can find ways to identify some common household products such as detergent, soap, washing powder, which I don't have any idea yet.
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