Analytical Chemistry 4/8/19

By Richard Bleil

Recently I have been disappointed in the movie selection in my services, and decided to binge watch the remake of an old science fiction sci-fi space series. I like the original series better, but with many seasons, and a few entertaining characters, it is good “background noise”, relatively entertaining and, most importantly, it is not necessary for me to find movies for at least a week or so.

Although this series is presumably based roughly 350 years in the future, when they are faced with unknown substances, in several episodes, their first response was to check the mass spectrometer. The irony is that mass spectrometry dates back to 1920(ish). This futuristic sci-fi series called for an analytical technique that was, in their time setting, nearly four and a half centuries old.

There are two forms of analytical chemistry, called “qualitative” and “quantitative”. There can be considerable overlap between these two, but in essence, “qualitative” analytical chemistry seeks out to identify unknown components, and “quantitative” analytical chemistry is used to determine how much there is.

Perhaps an easy example of the difference dates back to my time as director of a forensic lab. Our “drug chemist” was tasked with qualitative analysis. His job was to identify if illegal drugs are in samples, and identify what drugs they are. Is the powder cocaine, methamphetamine, or laundry detergent? For substances such as these, it doesn’t matter how pure the samples are; possession of these drugs in any concentration is illegal. The chemist did not know what he was looking for, but tasked with simple identification, using, among other instrumentation, the mass spectrometer in the process. This is qualitative (think “quality”) analysis.

Down the hall was the blood-alcohol lab. In this lab, the chemist was tasked with identification of one, and only one, compound, namely, ethanol, the active and intoxicating agent in alcoholic beverages. In the samples, ethanol was either present, or not present, but in current laws, this is not enough. Provided you are over the legal drinking age, you are allowed to be drinking, and even drunk, provided you are not driving. But, the presence of alcohol is not enough; it is important to know the exact concentration of the alcohol in the blood. In many states, it is illegal to drive if the blood alcohol concentration is over 0.08%. Here, the material of interest is known, but it is the concentration that is important, making this quantitative (think “quantity”) analysis.

Analytical chemistry is one of the more interesting disciplines, in my humble opinion. In colonial days, the Native Americans would chew on a type of bark to treat their headaches. Eventually, it was an analytical chemist that separated out the naturally occurring chemicals in the bark, isolating and identifying the compound aspirin. Qualitative analysis actually dates back to the earliest chemists, Islamists from around 600 AD who asked, quite simply are these things the same? They were the first to classify compounds as inorganic or organic.

Today, qualitative and quantitative analysis are frequently used. Quantitative analysis is a key component in manufacturing. For example, in food processing, qualitative analysis is used to check for impurities both before and after processing and packaging. In the environment, qualitative and quantitative are used together. Many years ago, I studied soils for pesticides. The presence of pesticides was not necessarily illegal, provided the contamination level was below a certain level (in the parts per million range). So we first had to identify the pesticide, then determine the concentration.

Such an analysis has two components. The first is separation of the substances in the sample. Any analysis, whether quantitative or qualitative, must begin with singling out the material of interest. In blood alcohol, the alcohol had to be separated from the sample of blood. In the analysis of bark, the active ingredient aspirin had to be separated from the other chemicals and components of the bark. Once separation has occurred, there are a myriad of wet chemical tests and instrumental methods to identify the structure of compounds, and the concentration.

I have long considered analytical chemistry to be the “heart” of the field. It is the fundamental and first step in identification of active ingredients in things like bark before a synthesis can be made to make it less expensively. It is also the discipline that checks for concentrations to be sure that our water, foods, air, and surroundings are not so toxic as to be dangerous. It is analytical chemistry that monitors concentration of effluent from mines into rivers and streams to be sure heavy metal contamination is within acceptable limits. It is analytical chemistry that tests soils and water from abandoned manufacturing areas to ensure no toxins at dangerous levels are left behind. It is analytical chemistry that identifies poisons used for nefarious purposes so it can be treated. It is even analytical chemistry that tests my blood to be sure my heart disease does not come back.

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