Re: ORGLIST: Spectra similarity indexing

Date view Thread view Subject view Author view Attachment view

From: Jacob Zabicky (zabicky$##$bgumail.bgu.ac.il)
Date: Thu May 23 2002 - 10:54:28 EDT


When trying to match IR spectra it much depends on the type of spectrum you
run, say, solution, mull, KBr tablet. The first one should be the most
reliable when run under cotrolled conditions on a good instrument.
Discrepancies between a specimen and a standard ne not necessarily mean a
different compound, but may point to the presence of impurities.
Quantitative analysis can be developed for solutions.

The other two methods are quite good for identification tasks. Look for
medium to strong peaks in the "fingerprint" range, absence of such peaks or
their presence at wrong frequencies is good indication for the wrong
identity. The peak intensity when using solid dispersions may be quite
uncertain, because in some regions the fraction of scattered light may be
significant when the crystallite size diminishes.

All the best,

Jacob

At 5:14 23/05/2002, mohamad mukharir wrote:
>Dear Mohsen,
>Thank You very much for your kind attention,
>I need a help for my problem in spectrum comparation (or matching). when I
>scan a sample using IR spectro, I have difficulty to decide whether the
>spectrum I got is what I want. I try to solve it by scanning some
>references, but I found that there are some difference between the
>sample's and the reference's spectra. so I search through internet for the
>problem and I found a simple equation
>P=A/n
>where P is matching factor A is agreements for some selected peak (
>strongest peak ) between sample's and standard's spectra, and n is the
>number of selected strongest peak. This equation was used in MS spectral
>guessing for some instruments. but i'm not so satisfied with this answer.
>because there are some differences between IR and MS spectral properties.
>IR spectrum have tendency to vary in it's wave number, not like MS
>spectrum did. and IR spectrum not that narrow as MS spectrum. so I think
>the equation need to be specified for IR spectrum matching. but How....?
>thanks a lot for any sugestion.
>salam,
>
>kharir
> mohsen fouad <fouad_m_m$##$yahoo.com> wrote:
>Dear Sir,
>I have experience in Industrial and Systems Engg science. If you need any
>help related with these sciences, tell me.
>thanks
>Dr. Engg. Mohsen Fouad
> mohamad mukharir <mohamad_mukharir$##$yahoo.co.uk> wrote:
>Dear all....
>
>I want to know how to find similarity index which shows the similarity
>between two IR or UV-Vis spectra. I ever search over internet, but I only
>find similarity indexing for mass spectra, as used in library searching in
>integrated GC-MS station. can you help me to solve this problem.
>
>
>
>best regards,
>
>
>
>
>
>kharir
>
>
>
>---------------------------------
>Do You Yahoo!?
>Yahoo! Health - your guide to health and wellness
>
>
>---------------------------------
>Do You Yahoo!?
>LAUNCH - Your Yahoo! Music Experience
>
>
>---------------------------------
>Do You Yahoo!?
>LAUNCH - Your Yahoo! Music Experience
><P>Dear Mohsen,
><P>Thank You very much for your kind attention,
><P>I need a help for my problem in spectrum comparation (or matching).
>when I scan a sample using IR spectro, I have difficulty to decide whether
>the spectrum I got is what I want. I try to solve it by scanning some
>references, but I found that there are some difference between the
>sample's and the reference's spectra. so I search through internet for the
>problem and I found a simple equation
><P>P=A/n&nbsp;&nbsp;&nbsp;&nbsp;
><P>where P is matching factor&nbsp; A&nbsp; is agreements for some
>selected peak ( strongest peak ) between sample's and standard's spectra,
>and n is the number of selected strongest peak. This equation was&nbsp;
>used in MS spectral guessing for some instruments. but i'm not so
>satisfied with this answer. because there are some differences between IR
>and MS spectral properties. IR spectrum have tendency to vary in it's wave
>number, not like MS spectrum did. and IR spectrum not that narrow as MS
>spectrum. so I think the equation need to be specified for IR spectrum
>matching. but How....?
><P>thanks a lot for any sugestion.
><P>salam,
><P>&nbsp;
><P>kharir
><P>&nbsp; <B><I>mohsen fouad &lt;fouad_m_m$##$yahoo.com&gt;</I></B> wrote:
><BLOCKQUOTE style="PADDING-LEFT: 5px; MARGIN-LEFT: 5px; BORDER-LEFT:
>#1010ff 2px solid">
><P>Dear Sir,
><P>I have experience in Industrial and Systems Engg science. If you need
>any help related with these sciences, tell me.
><P>thanks
><P>Dr. Engg. Mohsen Fouad
><P>&nbsp; <B><I>mohamad mukharir
>&lt;mohamad_mukharir$##$yahoo.co.uk&gt;</I></B> wrote:
><BLOCKQUOTE style="PADDING-LEFT: 5px; MARGIN-LEFT: 5px; BORDER-LEFT:
>#1010ff 2px solid">
><P>Dear all....</P>
><P>I want to know how to find similarity index which shows the similarity
>between two IR or UV-Vis spectra. I ever search over internet, but&nbsp;I
>only find similarity indexing for mass spectra, as used in library
>searching in integrated GC-MS station. can you help me to solve this
>problem.</P>
><P>&nbsp;</P>
><P>best regards,</P>
><P>&nbsp;</P>
><P>&nbsp;</P>
><P>kharir</P>
><P><BR>
><HR SIZE=1>
><B>Do You Yahoo!?</B><BR><A
>href="http://rd.yahoo.com/welcome/*http://health.yahoo.com">Yahoo!
>Health</A> - your guide to health and wellness</BLOCKQUOTE>
><P><BR>
><HR SIZE=1>
><B>Do You Yahoo!?</B><BR><A
>href="http://rd.yahoo.com/welcome/*http://launch.yahoo.com">LAUNCH</A> -
>Your Yahoo! Music Experience</BLOCKQUOTE><p><br><hr size=1><b>Do You
>Yahoo!?</b><br>
>LAUNCH
>- Your Yahoo! Music Experience

x-x-x-x-x-x-x-x-x-x-x-x-x-x-x-x-x-x-x-x-x-x-x-x-x-x-x-x-x-x-x-x-x-x-x-x-x
Prof. Jacob Zabicky
Institutes for Applied Research
Ben-Gurion University of the Negev Private: POB 12366, Beer-Sheva 84863
POB 653, Beer-Sheva 84105, ISRAEL Tel. +972-8-6496792
http://profiler.bgu.ac.il/site/main.cfm
Tel. +972-8-6461271/6461062/6472754
Fax. +972-8-6472969
x-x-x-x-x-x-x-x-x-x-x-x-x-x-x-x-x-x-x-x-x-x-x-x-x-x-x-x-x-x-x-x-x-x-x-x-x

_______________________________________________
ORGLIST - Organic Chemistry Mailing List
Website / Archive / FAQ: http://www.orglist.net
To post a message (TO EVERYBODY) send to everybody$##$orglist.net
To unsubscribe, send to everybody-request$##$orglist.net the message: unsubscribe your_orglist_password your_address
List coordinator: Joao Aires de Sousa (coordinator$##$orglist.net)


Date view Thread view Subject view Author view Attachment view

This archive was generated by hypermail 2.1.4 : Fri Sep 19 2003 - 12:16:54 EDT