Hi

There is a wealth of literature in this area, along with a wealth of different organometallics.  However there is a big difference between metal containing drugs eg cisplatin, where the metal is covalently bound in the drug molecule and metal-ligand complexes eg haemoglobin where the metal is held non-covalently.  I think you need to specify in your question which you are interested in as there is a fundamental difference and this will be a major deciding factor in the methods used.

If you look on my researchgate opage you will find 2-3 publications on the quantification of cisplain by LC-MS/MS and HPLC-ICPMS, along with some on metalloproteins and small organometallic compounds containing mercury, tin, arsenic. Most of this was separated by reversed phase chromatography with a buffer and some organic modifier such as methanol.

 I also publish a review of the previous years literature on the analysis of these compounds (Atomic Spectrometry Updates Elemental Speciation), also on my researchgate page.  You will see from this there are about 200-300 publications we review each year. Happy reading!

Hello,

This is fairly common with siderophores.  They tend to elute in both the free and metal bound complexes, each at a different retention time (metal bond tend to elute later in reverse phase).  You can almost always identify the metal by looking at the mass difference between free and metal bound complex, then verify by looking at the isotope pattern diagnostic for the individual metal.  I hope this helps.

Best regards,

Gabriel Navarro

the answer of the colleague Herrington is correct

The answer depends on many factors but always remember physicochemical properties not only of your compounds but also of the type of column employed. Even with covalent, coordinative, ionic or mixtures of these bonding schemes you should be careful to thorough analyse your results. I recommend to first try standard techniques and depending on the results and analysis develop modifications to the standard as some colleagues stated herein. First of all always read related contributions to make notice of the ruling factors in those published experimental procedures. E.g. if your compound is mostly ionic as well as the material of the column they could interact in such a degree that demetallation occurs as in a double displacement or metathesis reaction. Wish you good experimental setups.

Dear colleagues,

Thank you very much for your pragmatic in-put! I strongly admit the point "whether the metal is covalently bound or not" by Chris Harrington is critical. And, a nice point by Gabriel Navarro who explains the closest point of my question with the example of free siderophores and the metal-complexes of siderophores.

Yes! there are plethora of literature and works on chromatographic-mass spectrometric study of Inorganic complexes, among them some are very familiar compounds like cisplatin, vitamin B12 (organo-metallic), hemoglobin, or compounds like them. But, my point is chromatography of compound type Z-m or Z-m-X.

Consider complex like Z-m, where Z may be an anti-diabetic drug or an organic ligand, and m= a transition metal and the complex is a coordinated complex, where Z remain as coordinated Z with m. Pharmacologically active Z can be quantified (assay) freely by LC-UV (say reversed phase). Now, the RPLC-UV investigation for Z-m: practically,  the complex's chromatogram slightly differs from the retention time of the Z but different in peak (size) area, (Z-m preparation was made maintaining the same amount, as the amount used during preparation of Z). What is happening here actually???...In my experience, the complex also retained like Z, chromatographic response also like Z at fixed length of UV zone but the peak size was lower than Z, (may be metal or other non-UV responsive groups may not signaled thus deducted from peak area). However, I am not sure Gabriel Navarro! We may not identify the metal by looking at the mass/peak area difference between free ligand and metal-complex, but we can almost estimated the ligand (if it has no synthetic change). And, obviously Hiram Isaac Beltran, we must need a suitable stationary phase as well as a detector, the same Z-m complex will give additional idea if we consider the ion-exchange chromatography, to understand the quantity of metal and other ions.

Regards.

Hi

I'm not sure I fully understand what you are trying to do, but if you included atomic spectroscopy such as atomic absorption spectroscopy or inductively coupled plasma mass spectrometry (either by collecting fractions or on-line) as one of your detectors you would at least be able to do a mass balance to see if the eluting compounds contained the same amount of metal as the amount injected.  Atomic spectroscopy techniques, unlike molecular detection methods such as UV and mass spec do not require an identical compound for calibration; an inorganic standard of Pt can for instance be used to quantify the amount of cisplatin, the only caveat to this is you need to know the structure/stoichiometry of the compound to get full quantitation of the compound.

In your example you would be able to determine if the change in peak height/area was due to loss of the metal from the complex to the stationary phase.  Often silica based stationary phaes without complete coverage are able to strip metals from the complex.

Dear Chris Harrington, you got the point!!! As I have some facility constraint (like LC-ICPMS), I am trying to quantify the metal part at separate AAS as well as combining the results from LC (ligand one) and AAS( metal one). Well, I will try silica based column, this point probably give me some new out come. 

My experimental way is quite unusual (combination of LC and classic) and also, may be it would be complex type specific. Surely, your such brilliant participation helps me a lot. Although, I have started browsing Harrington's article on RG page but  I would appreciate if you link me some good specific article of such kind of work.

Thanks.

Hi

I'll try to look something out for you.  The point about the silica column was refering to older silica based reversed phase columns where the exposed silica could remove the metal.  This is clearly not something you want to happen as it will lead to ghost peaks and poor quantitation.  Newer silica C18 columns or resin based C18 columns would be better if you have them.

Thanks Chris, my above separation discussion was based on my experiment through C18 RPHPLC (already)!