We can’t be the only ones looking forward to taking a dip in the swimming pool this summer while enjoying an ice cold drink. Fingers crossed, your swimming pool of choice is urine free, but if we are being honest, that’s likely not the reality. Luckily, the sanitation of pools can be controlled with chemicals such as chlorine. As a testing lab, we remain consistently curious about how analytical science can be used to produce answers to nagging questions. Let’s take the question of pee in the pool—how much is there? How would you even begin to assess this?
Foundationally, it is worth considering how urine would even be detected since the chemicals used to make the pool sanitary destroy common compounds found in urine, urea for example. Scientists at the University of Alberta decided to tackle this analytical challenge and come up with a way to quantify urine in the pool. They started with a widely consumed compound, acesulfame-K (ACE).
ACE is present in common artificial sweeteners. When ACE is consumed it enters the stomach and the rest of the food gets digested. However, ACE leaves your stomach and passes through your blood unchanged. From there, it gets filtered into the kidneys, still unchanged. Next, it enters the urine stream, (can you guess what comes next?) still unchanged. If the person happens to be in a pool when they urinate (yes, that is so gross), it enters the pool still unchanged. Based on this knowledge, researchers discovered that if they could test for the presence of ACE in a swimming pool, they could extrapolate the amount of urine present based on other research efforts done to establish the average amount of ACE in urine.
The amount of ACE within swimming pools is measured on the nanograms per liter order, which means roughly a part per trillion level. In order to accomplish analysis this sensitive an incredible instrument was required—one we are fortunate to have on site—Liquid Chromatography/Mass Spectrometry (LC/MS). LC/MS has extreme sensitivity and is suited for an analysis of this nature.
Chromatography, in general, is the right choice when trying to separate out mixtures, like pool water full of chemicals and possibly urine. LC-MS rather than Gas Chromatography-Mass Spectrometry (GC-MS) was used because ACE is a non-volatile compound. In order to analyze a sample with GC-MS it must be heated and the volatiles are then analyzed, ACE doesn’t have a boiling point, it degrades when temperatures are high enough. Mass-spectrometry is what allows for the identification of the individual components within a mixture of compounds.
For this research, a controlled study was not conducted. The lack of a controlled study was one known limitation and resulted in conducting this research based on a variety of assumptions. However, can you imagine what a controlled study related to urine in pools would be like? Potentially lots of people drinking lots of diet drinks and then taking a dip in the pool. Science can be strange, that’s for sure.
A vulnerability of this study is that ACE in a swimming pool could be the result of something other than urine. For example, if someone accidentally dropped a diet soda into the pool it would immediately give false-positive results for copious amounts of urine. Based on the calculations and information provided in this study, if you dropped 8-ounces of soda in a pool it would give results of 56 liters or urine in the swimming pool.
So what can we conclude from this strangely fascinating scientific study? Many things! Once again, we are able to see the everyday application of specialized analytical techniques, like LC-MS. We are also struck by the curious minds that endeavored to measure urine in the swimming pool in the first place. We can conclude above all else, science is anything but dull.