Studying long

Looks like November wasn't a great month for posting, for me. Well, I'm back, and this time with another medical term. As with the others, if a medical doctor reads this and I'm wrong about something, I would love to hear about it so I can fix it. I am writing from a non-medical person's perspective for other non-medically trained people, but I hope I'm not making any doctors cringe.

So this time it's "longitudinal study". The basic idea behind a longitudinal study is that the study follows specific people for a long time—years, or decades. These can be used to tease out things like what affects aging or why some kids develop asthma but others don't, and many more.

Chemical telephones

The folks at UCLA have come up with a way to use cell phones to test for allergens in food. And we're not talking looking it up in a database somewhere, we're talking an actual lab test, which tests the actual piece of food in front of you.

Potentially useful if you have a life-threatening allergy, such as to peanuts, the example used in their paper.

While this does use the camera built into the phone, as a lab test, it is more than just taking a picture. Specifically, it uses a colorimetric process to measure how much allergen is in the sample.

I've used colorimeters before, and they are generally quick and handy (and portable, if you buy the portable version of the reader). However, that "generally" is important. While I've used some colorimetric kits that only take 5 minutes, I've used some that take over half an hour, and that's not counting sample preparation time.

And all of those kits require sample preparation of some sort, adding chemicals, and waiting for the reaction to finish before measuring. Most of the stuff I tested required dilution of a water sample to bring it into the testing range. The peanut test described requires the sample to be finely ground and dissolved first, and is described as taking 20 minutes, not including grinding time.

The good kits come with either pre-measured chemicals or easy quantities of liquid chemicals to measure, such as with a standard pipette or a supplied dropper, to minimize test error. The reaction of the compound of interest with the added reagents causes a colour change, which the sensor (or camera) measures. Generally, at least for the kits I've used, the darker the colour, the more of the compound of interest is present. From the paper, it looks like the peanut test turns red.

Realistically, now that the photo processing and colour measurement has been sorted out, any pre-existing colorimetric kit could be adapted for cel phone use. But then, most people who might get these things for personal use would be more interested in allergens than the stuff I have tested for at work. Most people don't care all that much how much calcium is in their water, because it isn't a health issue.

(Ok, technically this one is almost year old, but I don't restrict myself to only talking about new discoveries.)

Food chemicals

I was tossing around the idea of doing some posts on the various food additives one sees (and which some people are frightened by, due to their long chemical names) when I ran across Science Fare's list of The Ingredients of Scientific Cooking. Some of these every cook has used (sodium bicarbonate aka baking soda; sodium chloride aka table salt; ethanol aka drinking alcohol, to name the three most instantly recognizable ones), and some are a bit more specialty (such as pectin to gel a jam - mmmmm, I remember my mom's jam) and some I didn't realize people used in home kitchens. Although in hindsight, the fact that I have seen a bag of MSG in the supermarket means that yeah, people do actually use them.

This list looks like an excellent resource, though I may branch out from it and look into some of the things used only in commercially produced food, because I am curious about some of these. Especially items such as preservatives, since without them, food (and even non-food items such as sunscreen) doesn't last very long and provides a potential base for bacteria and mould, some of it potentially harmful, to grow.

Chopping up pollution

Normally I just post whatever interesting bit of chemistry catches my interest on a given week, but today I'm posting about something of special interest to me. It's not about my work specifically, but it is about pollution remediation—and that, in a broad sense, is what I do.

This fascinating bit of cleanup chemistry targets some of the most difficult to remove pollutants. The unsightly colour of lignin stained water coming out of a pulp mill, pharmaceuticals passing through sewage plants (page 2), pesticide and herbicide runoff from farms, parks, golf courses, and lawns, and many others. Chemical warfare agents are even on the list of targets.

Unfamiliar noises

I had just picked up a rental car to use during a work trip, of a make and model I'd never driven before. Just as I pulled out of the parkade onto the road leaving the airport and the speedometer moved above the 10, the car shook and a made a sound that had me frantically looking in the rearview mirrors to see what piece of itself the car had just dropped on the road behind me.

Nothing. The road was clear, the car wasn't shaking or making any funny noises anymore, and was accelerating smoothly. Weird.

Just as I pulled off the airport road onto the freeway, and accelerated further, it happened a second time. This was really weird. Still nothing on the road behind me.

It was probably 5 minutes later, as I was driving around a 270 degree freeway ramp to get going the way I wanted, that I figured out what the noise and vibration was. Something not visible inside the rental car parkade, and not in my line of sight when driving the car due to keeping my line of sight on the road.

Impeccable timing on that thunder, Mother Nature.

I'm glad the funny noise wasn't a sign of anything damaged or about to fail, but I've encountered those conditions more than a few times. One reason I pay attention to them!

Biodegradation experiment

Quite a few months ago, I mentioned a test I thought I might run. I didn't start it at the time because it was winter and my assistants for this particular test tend to be sluggish when it's cold out. Then I forgot about it for a while.

For those who followed the link above, yes, I'm talking about that test.

Meet my lovely assistants, who will be doing the actual work of the biodegradation test! It's summer now, and they're happily eating through my kitchen scraps.

Gold, with or without cyanide

Some things are unavoidably toxic, and some things were unavoidably toxic until a new, less toxic process was discovered. Less toxic is always a good thing. Sometimes it's less expensive in terms of direct costs such as how much the reagents cost, sometimes less expensive in terms of indirect costs, such as safety precautions and environmental protection.

Sodium hydroxide is one such; the old industrial method of making it involved mercury, which is highly toxic. The new industrial method doesn't. (There are still toxic chemicals involved, but they're not mercury.)

One thing that will hopefully one day be added to the past-tense version of unavoidably toxic is gold mining. Currently, if gold can't be panned from a streambed (placer mining) where it's present as pieces of fairly pure gold, it has to be dissolved out of the rocks, often using cyanide. A newly discovered process is being described as possibly displacing the cyanide.

Timely prizes

Here's something fun that I feel like I should have heard about before now, what with following science news and all that.

The Center for Communicating Science has an annual challenge to (surprise!) communicate a scientific subject—in a way that an 11-year-old will understand. Which means no university level math. Obviously, my posts here are not even close to what they're looking for, since I assume at least high school chemistry, most of the time, and I like including math.

One of the two winners is a canadian PhD student in chemistry and, from the look of his videos, an all-around goof. I certainly got a few laughs out of his video, and I thought his explanation was the clearest I've ever heard.

Anti-fizz

While in Europe on a work trip and grabbing a bite for lunch at a café, I grabbed a bottle of water on my way to pay without checking the label. Checking the label is important, because in Europe, "still" water and "sparkling" (carbonated) water are sold side by side—and I can't stand the taste of sparkling water. Halfway through eating lunch, I opened the water bottle to have a drink and it sprayed water all over my tray and my clothes.

I'd grabbed the wrong sort of water. Not only that, I'd obviously shaken it at some point.

Because I'd opened it, I couldn't return it for a bottle of still water, so I decided to de-sparkle the sparkling water, in the hopes that it would improve the taste. Fortunately, this requires no special equipment and can be done in a café, although it might draw some funny looks.

Seeing at the surface

One of the quirks of chemistry is that we measure the bulk solution, but the reaction often happens on a surface - whether it's precipitation, dissolution, or catalysis.

While we usually calculate reaction rates based on the concentrations found in the bulk solution, in a case of a surface reaction, that's out where no reaction is happening! The equations for reaction rates empirically account for this in the constants, where the reaction rate is rolled together with the rate the reagents diffuse toward the surface to react and the rate the reaction products diffuse away from the surface and out of the way.

But in terms of designing a reaction, controlling it to get, say, the product we want instead of a byproduct if there are two possible reactions, or speeding it up or slowing it down, what happens at the surface can be key. And whether we watch or measure, knowing what happens at the surface is the first step toward changing what happens at the surface.