Numbers of Atoms

Numbers of Atoms is a series focussing on analytical chemistry.

Wait a minute, you have a series on analytical chemistry? Why would you do that?

Short answer: because I like analytical chemistry.

Long answer: because when I tell people that I am an analytical chemist, I usually get one of three responses:

(1) “Oh cool, I’m also an analytical chemist!”

(2) “Oh yeah, well I’m an (organic/inorganic/physical/bio) chemist, and I never really liked analytical”

(3) “Oh… So what does that mean?”

Most people have no idea what an analytical chemist does, beyond assuming that he/she analyzes stuff (good on them for figuring that out). And among chemists, analytical chemistry tends to be quite under-appreciated.

What is your source for that last assertion?

My own scars and recollections from over a decade in various chemistry departments.

When most people think of chemistry, they think of reactions that make bubbly or fizzy things, and cause bad smells and sometimes explosions. But when we need to know how much of that bad-smelling stuff is in the town’s drinking water, that’s when the analytical chemist comes in.

I know an organic chemist. He says he hated analytical chemistry.  I think he was tired of all those calculations and formulas.

The plural of formula is actually “formulae”. But point taken. It does require some use of statistics, but I will try to keep that to a minimum – only when it’s necessary will I break out the equations.

As for organic chemists, chemical analysis is an unavoidable part of their work, a bit like balancing a checkbook every month. (Of course, chemists with large checkbooks can pay to have their analysis done elsewhere, but nothing beats doing the work on your own.) After all of the creative work in synthesizing a new compound, your friend still has to figure out whether that little bit of white powder at the bottom of the flask is really what he thinks it is, and then, how pure it is.

I just noticed that the abbreviation for analytical chemistry is “Anal Chem”. Tee hee.

Yes, tee hee. Actually, the abbreviation isn’t so inappropriate – it does require attention to detail to be a great analytical chemist. But I realize that’s not the play on words you were going for.

Alright, so what is analytical chemistry?

Analytical chemistry is the branch of chemistry that seeks to determine the chemical composition of materials. While the organic and inorganic chemist deals with creating (“synthesizing”) compounds and understanding how it reacts with other compounds, and physical chemists concern themselves with the thermodynamics and kinetics of chemical reactions, analytical chemists try to figure out what are the chemical species in a mixture, and then, how much of each species is in there.

That seems like an oversimplification of the branches of chemistry.

Of course it is. This is a blog post, not a Wikipedia entry.

Chemical analysis falls into two broad categories: qualitative analysis, which answers the general question of “what is in there?”, and quantitative analysis, which answers the general question of “how much of it is in there?”. In a complicated mixture like oil, blood or food, we’re probably only interested in knowing the concentration of one or a few chemical species. Each chemical species that we are interested in analyzing is known as an analyte.

Is there a machine or app that does all of that?

I hope not – otherwise, most analytical chemists would be out of their jobs. There are machines (we prefer the term “instruments“) that perform their own tasks quite well, but there is no universal instrument or method that can analyze everything.  Each instrument is limited in the type of compounds it can analyze and the information that it can give. As just one example, X-ray crystallography can tell us the structure of the atoms in a molecule within a crystal, but it will be useless for figuring out the concentration of that molecule in drinking water.

And remember that analytical chemistry existed long before computers and even electricity. Some analysis is as simple as mixing the analyte with a solution containing a compound that reacts only with it.  A change of colour would immediately indicate the presence of the analyte, and a few calculations can tell us the concentration of the analyte.

Ok then. I hope this will be interesting. I heard that you once taught analytical chemistry in a university, and that the attendance and general degree of awakedness for the Friday 8:15am lectures was not great.

Yeah, but at least these posts can be read at any time.

This series is not meant to be a substitute for a textbook; I can suggest Quantitative Chemical Analysis by Harris and Fundamentals of Analytical Chemistry by Skoog, West, Holler and Crouch as good analytical chemistry textbooks. This series will also not replace a good chemistry 2000-level class (which usually has an unimaginative name that is some variation of “Introduction to Analytical Chemistry”). It is aimed at readers with curiosity, and at least some basic chemistry knowledge.

What exactly will you be writing about?

This series will grow organically (pun intended), and I am open to any ideas about articles. The list of topics will be continually updated on this page.

 

Separating the raisins from the bran flakes (sampling)

If it’s not part of the solution, it could be analyzed (analyte extraction)

Overcoming separation anxiety with chromatography (paper/thin-layer chromatography)

Excelling with chromatographic columns (HPLC)

Finding the smallest traces (GC-MS) 

 

Old school analysis (general acid/base titrations)

Real chemists still do titrations (Kjeldahl method, primary standards)

Complex approaches for titrating metals (EDTA and complexometric titrations)

 

Spectroscopy, from Kool-Aid to Beer (general absorption spectroscopy)

Light absorption, spectrophotometers, and missing potato chips (how absorption spectroscopy works)

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