Hi, I am new in the field of practical usage of the HPLC technique, I am working on a project that deals with characterizing vanadium within seawater samples. I have started using the technique for sometimes and faced few challenges. My first question is how can I be sure that the peak I see is that of vanadium, I have used a standard sample, yet how can I make sure? In another word, can more than one element have the same retention time using the HPLC technique?
Thanks Michael.
For detecting the vanadium metal ion, I am aware that the species would depend on the pH.
- Detector is UV
- I am looking for V(V) and V(IV)
- For the concentration I am not sure I need to quantify the seawater sample using a standard vanadium sample calibration,
- For the pre-treatment. I have started with evaporation and filtration. Then I have tried filtration only and to my surprise I got a nice peak . I am planning to use a precomplexing reagent as well and then analyze the differences
- I am using a C18 column and an eluent that consists of (MeOH:Water, 50:50)
Hello Iman: To answer your first question, "how can you be sure the HPLC peak you see is vanadium", well you can't. Many other metals (and/or organic compounds) could elute at exactly the same retention time. A well developed HPLC method will minimize this from happening, but can not guarantee an error will not be made. From a scientific perspective, to make a positive ID you would need to employ several (~3) different orthogonal methods/detection techniques to be confident that the peak is what you think it is. If the compound can be resolved by HPLC, then you could collect the peak and submit it for ICP analysis to get a second dimension of analysis.
It sure would help us if you provided ALL of the details of your HPLC method and of course the sample prep used. The detection levels needed would also be useful info too as some methods may or may not be sensitive enough. *HPLC is a rather complex technique and, unless the operator is highly skilled/trained, subject to a high degree of error (as is the case with most instrumental methods). I hope that you have an experienced person helping you with this project. Also, have you considered using a more conventional approach of AA or ICP-AES to determine the levels? Lots of journal articles on this topic which can be found on the web using a simple keyword search. If you have not done so already, please review the literature for different methods and techniques.
Example links :
http://link.springer.com/article/10.1007%2Fs00216-002-1532-3
https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=2&ved=0ahUKEwid6_OdgafJAhWIYiYKHU2oD9UQFggoMAE&url=http%3A%2F%2Fwww.ajol.info%2Findex.php%2Fsajc%2Farticle%2FviewFile%2F123097%2F112637&usg=AFQjCNFjSfCJ13dSY4OdQbhexlS06Hlrfg&bvm=bv.108194040,d.eWE&cad=rja
https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=7&ved=0ahUKEwid6_OdgafJAhWIYiYKHU2oD9UQFghKMAY&url=http%3A%2F%2Fproj3.sinica.edu.tw%2F~chem%2Fservxx6%2Ffiles%2Fpaper_8165_1269159121.pdf&usg=AFQjCNGoP1Vn50n_Q5z3cUCaFDR4P70aRQ&bvm=bv.108194040,d.eWE&cad=rja
Thanks Bill. To make sure about the positive ID for my element I would need then to use another technique. I have used before the atomic absorption, so it would not be hard to do that. Yet, I don't have any experience with using ICP-OES
For the literature, I have read many articles as per qualifying and quantifying vanadium within environmental matrices using different techniques. Now, my objective from this project is to find an simple method to qualify and quantify total vanadium as well as to qualify and quantify vanadium species using the HPLC technique.within environmental samples.
Thanks Michael. As I said I am interested in vanadium speciation. Any help is welcome.
Dear Bill and Michael,
I wanted to check the following with you please. As I said, I will be using AAS for a positive identification of the metalion, But I will need to do that later as the technique is running of gas and we have just ordered it.
I was thinking of doing a simultaneous identification of a mixture of metal standard solutions (V, Ni, Cu) using HPLC. Do you think, this is a good idea? I have read few articles that referred to such protocol.
I am working at 200 nm, which concentrations of each metal standard solution do you think would be relevant? I am hoping that at low concentration, we may be able to see a difference in retention time of V, Ni and Cu.
This is very easy. use standard sample for comparison. In higher version HPLC sytem eluted peaks can further be evaluated by collecting the peak concerned followed by evaluation either by UV or MS etc.
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