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Chemistry Forums for Students => Analytical Chemistry Forum => Topic started by: m-khalili on July 08, 2011, 03:11:47 PM

Title: spectrophotometery
Post by: m-khalili on July 08, 2011, 03:11:47 PM

hi
I want to know detection of lead ion (Pb2+) in a solution by spectrophotometer without any additive is possible?

Title: Re: spectrophotometery
Post by: Stepan on July 08, 2011, 11:21:44 PM

Lead ion in water is colorless.

Title: Re: spectrophotometery
Post by: m-khalili on July 09, 2011, 03:29:16 AM

thanks for your favor
so you mean that for determining the concentration of a metal ion in a solution with spectrophotometer, solution must be colorful?
how about cobalt ?are cobalt salt solution colorful?does the solution color of cobalt salt depend on the PH of solution?
best regard

Title: Re: spectrophotometery
Post by: Stepan on July 09, 2011, 07:34:41 AM

Cobalt ion in water has natural colour and can be detected with spectrofotometer. The colour and its intensity depends on everything: pH, other ions, inorganic impurities (NH3, H2S, Cl,...), some organic impurities (amines, .)

Title: Re: spectrophotometery
Post by: m-khalili on July 09, 2011, 09:13:18 AM

thanks so much
may you please help a little more
you mean with out any addition of ligand the concentration of Cobalt can be obtain with spectrophotometer?
 how about using uv visible spectrophotometer for determining  pb2+ or  Hg2+ concentration in the solution (with out addition of any ligend)?

Title: Re: spectrophotometery
Post by: BluePill on July 09, 2011, 11:15:10 AM

Pb²⁺ and mercury²⁺ cannot be measured without a ligand with spectrophotometry. You could do AAS if you don't want to use a ligand.

Title: Re: spectrophotometery
Post by: TheUnfocusedOne on July 09, 2011, 12:24:20 PM

+1 to AAS, probably your best bet.

Title: Re: spectrophotometery
Post by: m-khalili on July 09, 2011, 04:23:55 PM

I havent ASS so i should determine concentration Hg 2+ and Pb2+ by UV VIS spectrophotometer UNICO 2800
can any one suggest some reasonable and availble ligand for determination by this equipment(UV VIS spectrophotometer UNICO 2800_ wavalength range 190_1100 nm and spectral bandwidth of 4nm)?

Title: Re: spectrophotometery
Post by: m-khalili on July 09, 2011, 05:27:31 PM

Quote from: m-khalili on July 09, 2011, 04:23:55 PM

I havent ASS so i should determine concentration of Hg 2+ and Pb2+ by UV VIS spectrophotometer UNICO 2800
can any one suggest some reasonable and availble ligand for determination by this equipment(UV VIS spectrophotometer UNICO 2800_ wavalength range 190_1100 nm and spectral bandwidth of 4nm)?

Title: Re: spectrophotometery
Post by: aeacfm on July 10, 2011, 04:20:31 AM

i think additives to produce coloure is a must!!!

Title: Re: spectrophotometery
Post by: m-khalili on July 10, 2011, 04:36:33 AM

may you please suggest an additive:

Title: Re: spectrophotometery
Post by: aeacfm on July 10, 2011, 06:21:19 AM

depending on your field:
http://www.google.com.eg/#hl=ar&source=hp&q=spectrophotometric+determination+of+lead&oq=spectrophotometric+determination+of+lead&aq=f&aqi=&aql=t&gs_sm=e&gs_upl=2752l14404l0l40l37l0l21l21l0l547l3202l2-3.3.2.1l9&fp=6f6203ab33971ce&biw=1366&bih=535

Title: Re: spectrophotometery
Post by: m-khalili on July 10, 2011, 07:27:51 AM

though  cobalt salt are colorful,but I have read in some paper which researcher have added some additive  for determining cobalt concentration in solution,you think whats the reason?

Title: Re: spectrophotometery
Post by: Stepan on July 10, 2011, 08:07:59 AM

Cobalt and some other ions can be DETECTED in solution without any additional ligands, anions, or reactions. But result is qualitative and usually not sensitive enough.

When you use extra steps of analysis by introducing co-reagents, you increase selectivity, accuracy and sensitivity tremendously.

This is very old area of chemistry developed in 1890-1940's. The methods are well developed. Check the handbooks of analytical chemistry on-line or in your library

Regards

Title: Re: spectrophotometery
Post by: m-khalili on July 10, 2011, 11:02:13 AM

tanks
may you please introduce some useful study source for Pb2+ and Hg2+ ligand?

Title: Re: spectrophotometery
Post by: Stepan on July 10, 2011, 11:21:13 AM

I am sure you will be able to find enough methods in library or even on Google

Title: Re: spectrophotometery
Post by: m-khalili on July 10, 2011, 03:42:49 PM

Can I use xylenol orange (as a ligand) for determining concentration
of Pb2+  in a solution which following material are in :HCl, NaOH,
acetic acid,  sodium tripolyphosphate, NO3-
how about Hg(II) ?

Title: Re: spectrophotometery
Post by: Stepan on July 10, 2011, 04:49:30 PM

Dear m-khalili, your questions require intensive literature research and lab experimenting. Your problem cannot be resolved through forum - your questions are very broad. The answer depends on: you industry, your legal requirements, range of concentrations you need to cover, your matrix, composition of the sample, your resources, your background,.

You need either develop appropriate analytical method yourself or hire somebody who can do it for you.