I think colorimetric methods were used to determine Cu and Zn very successfully during early days of the development of instrumental analysis and are still useful but this method is time- and labor intensive. Thus it was replace by rapid techniques of instrumental analysis which are time-and cost effective. Hence in the recent literature, colorimetric methods are followed. Equally is important the compulsion imposed by reviewers of documents and partly by the publishers asking for recent analytical techniques or studies.

  Dear  Mauricio Molina

I have glad welcome with you

I invite you to submit paper for publishing in journal as well

look web page http://www.sciencepublishinggroup.com/j/ijmpem  

All the best

Ahmet Haxhiaj

[email protected]

I think colorimetric methods were used to determine Cu and Zn very successfully during early days of the development of instrumental analysis and are still useful but this method is time- and labor intensive. Thus it was replace by rapid techniques of instrumental analysis which are time-and cost effective. Hence in the recent literature, colorimetric methods are followed. Equally is important the compulsion imposed by reviewers of documents and partly by the publishers asking for recent analytical techniques or studies.

I think AAS method is more suitable and cost effective as well as reliable. analyzing these metals with labour intensive and time consuming colorimetric method is not economically feasible

For soil samples, XRF may be a choice for the determination of total Cu and Zn. However, its performance was generally poor in the determination of plant and water samples.

Thanks all for your comments. Still, If you can suggest any method (although expensive), I'd  really appreciate it.

 Dear Dr. Molina

You can check the provided method for Zn. I did not yet verify this method but do soon.

thanks

I think very valid points have been  raised by Dr Ghafoor, colorimetric methods have become obsolete for the reasons highlighted by earlier.

Dr. Srivastava. The point made above related to the disadvantages of colorimetric methods are pretty clear. But is important having alternative methods when you dont have, for ANY reason, an spectrophotometer or similar equipment easily available at your working lab. An alternative method can be used as an 'starting point' or 'initial screening' before the final determinations.

The literature is old as you suggest but the complexation/extraction reactions are the basis of reliable and efficient measurement techniques..  Dithizone was a common reagent, but many others were used during the 70s and 80s in preconcentration steps before quantitation using AAS.  You might consider ion exchange as a separation/  concentration technique before colorimetry.   

Sir,

Pual Milham sir rightly sadi Dithizone method can be used for colorimetric estimation of Zn. Here Na-Dithionate-Dithiozone reagent is used for estimation which gives near to true value as that of AAS analysis.

Pl see book 'Soil Chemical  Analysis by ML Jacksom, 1958, Printice Hall INC

Page :406 Chapter Dithizone extractant for soil Zinc

Thanks

Kindly go through this paper for further clarification..These might be useful to you...

Thanks, the second paper shows an interesting rapid method for classification.

Welcome Molina