Peruvian salt mines, seaside rust, HPLC precipitates and electrospray ionization – gas-phase ionic solids: is it all the same?

I enjoy very much the history behind the science. When reading the lecture about the Electrospray Nobel prize of 2002 from John Fenn: Electrospray wings for molecular elephants, that I start to note how a similar effect surround me and I never noted. In this lecture Fenn said that in 1976 two meteorologists were doing research on something they called “Atmospheric Pressure Ion Evaporation”, a kind of precursor of actual electrospray Ionization for mass spectrometers. The goal was to investigate “the possibility that charged droplets of sea water might be a source of some of the ions found in the atmosphere”.

Interesting, so we can have ionic salts on atmosphere? I never knew about that. Hmmm, so that’s why on seaside things seems to rust more easily, the “Maresia” effect (sorry, couldn’t really found a English word for that!!).

During a trip to Peru I visited a salt mine (not really a mine), where Peruvians directed a stream of salted water that came from a mountain to “pools” where it was dry out and the salt recovered.
The region was dry, few rainy days per year. But all place was covered with salt, I exclude the possibility of spills during rain for the reason I just described. The only possibility I see is salt carried by micro droplets during evaporation. You can see a photo at left.

Last month after my vacations I came back to work and saw some crystals growing from connection on HPLC (left), outside and inside the oven. No one had a previously leaking, the crystals came from the thin film of mobile phase from connections. Time was passing and during drying out the solvent carried the salt buffers over the metal. This explains how the salt covered the metal surface without a visible leaking but don’t explain how the mobile-phase evaporated so much without we see any leaking. By the way, we have leaking detector on ovens, and they work.

Anyone out there already did a 30% NaOH solution out a hood? Did you smell anything? Well, it seems that ionic solids are not so not-volatile as they taught to us…I think it follow that universal answer on chromatography: It depends of…

Almost the same principle is applied to Electrospray Ionization interface for mass spectrometers (left). But in this case the substance you want to analyse is ionized (with charge)and the equipment applies some potential to make the drop literally explode, they call coulombic explosion. And then, the ion free of solvent can be weighted using a magnetic field.

Last photo: Agilent Technologies.

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The Medicine Man – How Sean Connery made me become a chromatographer

This sounds a little “Cliché” but is true: I owe part of my few papers to Sean Connery.

Although he made me cry in "Untouchables", was in “Medicine Man” that he did the greatest impact on my life.

I don’t really remember when I saw Medicine Man of the first time, but was in Technical school (during high school) that I could understand that fantastic technique he used in the middle of jungle to identify the cure of cancer.

For those who never saw, in Medicine Man, Sean Connery is Dr. Campbell, a botanic performing studies in the middle of Amazon. For achieve his results Dr. Campbell request a Gas Chromatograph and an assistant, The assistant wasn’t exactly what Dr. Campbell requested so the problems stated.

Today I recognize that movie made some mistakes like:

Identify NaCl and FeCl3 in a plant extract by GC, Instantaneous structures using a Flame ionization detector and maybe the worst: using sugars as calibrators.

LEFT: Dr. Campbell in two scenes of Medicine Man, both with some columns and separation funnels on background.

NaCl and FeCl3 are non-volatile compounds and since the main limitation of gas chromatography is analyse compounds that can vaporize, they just shouldn’t be there.

LEFT: A closer view of the GC system in Medicine Man.

The FID detector is not able to differ ethanol and methanol, so take structures from this chromatogram is just impossible.

Even actual mass spectrometers cannot predict the structure of compounds, unless they are very know and be part of a reference library. To establish a structure of unknown compound techniques such as NMR is essential.

Use sugar as calibrator, hhmmm, let’s use our good will and think he used glucose derivative as “internal standard”. Still have a lot of issues against him, like, the anomer conversion problem.

LEFT is  Dr. Campbell discovery,  this would be the cure of cancer, the peak #37, a clearly terpenoid related compound.

Although with some technical mistakes the Medicine Man is the embryo of all chromatograms in TV and movies. All CSI people should thank Sean Connery for this.

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Estrange places to find a chromatographer, Part II: Thermoelectrical plant

Photo by Tomhe

 I do not consider myself a man with “networking” but I know some people, and was during some long distance car travels that I had my most important “class” on the fuel topic.

First class: it is incredibly simple all the chemistry involved in the process of burn something, like wood to coal and coal (or whatever) to CO2.

In many countries people burn wood(biomass) to create coal. Basically you pyrolyze the carbohydrates (mainly) and finish with Carbon:

C6H12O6 + heat +12O2 → 6CO2 + 6H2O (1)

C6H12O6 + heat + little O2 → C + CO + H₂O (2)

Equation 2 has nothing new, but what is cool is that you can stop in the middle of way:

C6H12O6 + heat →6CO + 6H2 (3)

Equation 3 describe the gasification of solid fuel and the result is the Syngas (Synthesis gas), which was used since second war as source for preparing liquid fuels with help of catalysts.

But what this has to do with chromatography? Well in the second car travel I met a man who worked exactly monitoring equation 3 with GC.

His main work was on research with new energy fields, but this technology is widely used and one of the problems in the process is that you have more than just carbohydrates on biomass, In the end of reaction you also can find SO2, Volatile Organic compounds, CO and NOx (NO and NO2) which all create environmental concerns and need to be measured.

For finish, most of work was done with packed columns, from Porapak family and molecular sieves, something really different for me “an organic”, even more than a sample matrix that can explode.

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Estrange places to find a chromatographer, Part I: Cattle farm

During undergraduate studies I worked for 4 years in the lab where most of students came to do the chromatography part of their work. In that time, I met some Veterinary students ( it seems that in Brazil you can have a bachelorship in veterinary , but in other places as USA, Veterinary is a Ph.D tittle). Well, among the studies they carried out , on was really interesting: In animal nutrition studies they monitor the amount of acids created in rumen depending on diet. Well, how they monitor that? With Gas Chromatography of course.
However in, 2006 an old mate from collegue start to look for me and asking stuffs about the Nukol columns, which is specific for free acids. My surprise was that he was doing GC analysis (as Chemist) in a big cattle farm in west part of Brazil, not that I couldn’t imagine farms operating with some technological improvement, I just could imagine a chromatograph beside the cow's enclosure!
Photo by tricky ™

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Make-up flow – why the same solution of gas chromatography don’t apply to liquid chromatography?

For those who don’t know, the evolution from Gas Chromatography (GC) columns from packed to capillary wasn’t a smooth change. The packet columns with 1/8” diameter were a widespread application and many of them using the traditional Flame Ionization Detector (FID) at that time.
When the capillary columns came to market the conversion from one column diameter to other needed also detector adaptations, mainly, because FID were optimized to work with a flow of 30 ml/min coming from column and it dropped to 2 ml/min in a capillary column. The solution was to make-up the column flow with a Nitrogen stream.
The same situation happens in HPLC with column diameters less than 4.0 mm. However, to do a make-up flow in HPLC is not a very common practice. This situation has a drawback:
The FID signal is proportional to mass, not concentration. The UV-Vis (most used in HPLC) is the inverse.

This means that one answer to “why narrow columns give sharper peaks” is that: because the peaks are less diluted in mobile-phase. When you make-up the flow, the “peak” become more diluted and less intense and broader.
However, we can find uses of make-up flow in literature, most of them for adjust the pH of mobile-phase before detection, like in Electrospray in which the analyte needs to be ionized.

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What drives me

I really think that chromatography is a special field in analytical chemistry, because of its thousand ways to solve the same problem (not all time, I know!!).
But there is something more, I really like it because the more complex the analysis the more skilled the analyst needs to be. The personal effort of the analyst makes difference.
However, everyday I see someone trying to kill that spirit, with rules and rules, ISO, pharmacopeias, guidances, etc…we are losing some critical view…that is why I started this blog, to complain about that, to disseminate knowledge, doubts and opinions.
Welcome aboard.

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