Chemical Intelligence

'E-nose' sniffs out mixtures of volatile organic compounds

Jun 2022, phys.org

https://phys.org/news/2022-06-e-nose-mixtures-volatile-compounds.html

Electric nose with porous metal-organic framework films that distinguish xylene isomer mixtures for environmental health monitoring.

Previously, researchers used gas chromatography analysis to identify the three forms of xylene. But this procedure requires large instruments that are expensive, and the analyses are time intensive. 

The researchers prepared six different porous MOF films known to adsorb xylene isomers and applied them to gravimetric sensors in an array called an "e-nose." By analyzing the sensor array data with a machine learning algorithm, the team could determine the composition of the mixtures with 86% accuracy for the 10-ppm mixture and 96% accuracy for the 100-ppm mixture. 

via Karlsruhe Institute of Technology's Institute of Functional Interfaces and University of Pittsburgh Department of Chemical & Petroleum Engineering: VOC Mixture Sensing with a MOF Film Sensor Array: Detection and Discrimination of Xylene Isomers and Their Ternary Blends, ACS Sensors (2022). DOI: 10.1021/acssensors.2c00301

https://dx.doi.org/10.1021/acssensors.2c00301

Image credit: AI Art - Top Secret Blueprint of God - 2022

a detailed blueprint of god, top - secret document 

Nano-sensor detects pesticides on fruit in minutes

Jun 2022, phys.org

https://phys.org/news/2022-06-nano-sensor-pesticides-fruit-minutes.html

Current techniques for detecting pesticides on single products before consumption are restricted in practice by the high cost and cumbersome manufacturing of its sensors.

Uses flame-sprayed nanoparticles made from silver to increase the signal of chemicals, "The flame spray can be used to quickly produce uniform surface-enhanced Raman scattering (SERS) films across large areas, removing one of the key barriers to scalability,"

To test the sensors' practical application, the researchers calibrated them to detect low concentrations of parathion-ethyl, a toxic agricultural insecticide that is banned or restricted in most countries. A small amount of parathion-ethyl was placed on part of an apple. The residues were later collected with a cotton swab that was immersed in a solution to dissolve the pesticide molecules. The solution was dropped on the sensor, which confirmed the presence of pesticides.

via Karolinska Institutet: SERS Hotspot Engineering by Aerosol Self-Assembly of Plasmonic Ag Nanoaggregates with Tunable Interparticle Distance, Advanced Science (2022). DOI: 10.1002/advs.202201133

https://dx.doi.org/10.1002/advs.202201133

Damaged plants and fake perfumes can be identified rapidly and reliably in real time

Jun 2022, phys.org

https://phys.org/news/2022-06-fake-perfumes-rapidly-reliably-real.html

Chiral detection:

Most natural chiral substances are found in two mirror-image forms present in different relative quantities. Therefore, every plant and every perfume must have its own individual chiral signature.

The relative ratios of the two enantiomers of pinene naturally vary in the emissions of such plants, but critically depend on the state of health of the plant.

Fake perfumes will have a chiral signature that differs from that of the originals.

The Mainz-based researchers have developed a cavity-enhanced polarimetric method for optical chiral analysis to detect the differing optical rotation effects of chiral molecules under polarized light. The researchers have been able to achieve a sensitivity that is better than that of the current state-of-the-art equipment by several orders of magnitude.

via Universitaet Mainz and the Max Planck Institute for Chemistry: Lykourgos Bougas et al, Absolute optical chiral analysis using cavity-enhanced polarimetry, Science Advances (2022). DOI: 10.1126/sciadv.abm3749

https://dx.doi.org/10.1126/sciadv.abm3749

 

The Ever Impending Electronic Nose

CMOS Sensor, image source

The electronic nose has been coming forever. We already have artificial noses in the form of mass spectrometers. The new kind use integrated circuits, the same CMOS chips that are in cellphones. They aren’t tied to a thinking, feeling human, but at least the initial step of identification is happening.

This article in particular is touting the use of an artificial nose to analyze breath samples, citing that “breaths contain gases from the stomach and that come out of blood when it comes into contact with air in the lungs. The breath test is a blood test without taking blood samples. Breath contains information about practically every part of a human body.”

This is good stuff, and explains why your breath starts to smell funny when you’re hungry, or why diabetic-breath smells like acetone, but I must keep going and repeat the sales pitch of this scientist:

"If you think about the industry around sensors that emulate our senses, it's huge," said Dr. O, also a professor in the Erik Jonsson School of Engineering and Computer Science and holder of the Texas Instruments Distinguished University Chair. "Imaging applications, hearing devices, touch sensors—what we are talking about here is developing a device that imitates another one of our sensing modalities and making it affordable and widely available. The possible use of the electronic nose is almost limitless. Think about how we use smell in our daily lives."

But yes, let’s think for a minute about how we use smell in our daily lives. Smell is so below the radar that we don’t consciously register most of its ongoings. So when we take this CMOS sensor to a brain, what exactly would we like it to do? Of course we can’t engineer the olfactory bulb itself, or the subsequent limbic system (in concert with our memory) that ultimately creates our experience of smell. But if we were to isolate it, and use it for specific things, like breath analysis, then what else would it do?

Gas leaks, obviously. Maybe it could alert my roommate to change the litter box? Or tell a parent that their teenager was drinking last night (that’s a simple breathalyzer built into the air system of the house; watch out kids). You would think we’d already have one to smell the maple syrup smell coming from the burning transmission fluid in your engine. And what else? Can I smell the presidential candidates with my CMOS supernose? Who knows. Smell a house on Zillow? Let’s bring it to Japan and see what they do with it.

Post Script:

On thinking about this further, I must stress the difference between what I’ll call active smelling and passive smelling. What we do as humans is passive smelling. For the most part, we are not actively looking for a particular smell. (And, in fact, this is no way to smell, unless you’re a fragrance artist.) It’s more like the Tao of Perception – you must have a “soft awareness” where you are ready for any smell, but you’re not actively smelling for anything in particular. That’s just the way smell works. So this is passive smelling.

Active smelling would be a sensor fitted for one particular odor compound. Acetone, for diabetic-breath, for example. Or it may be fit for a bunch of things on top of that. But you could never fit the sensor for all potential smells. That’s not how the human epithelium works. We would need an artificial olfactory bulb for that, because the bulb turns our 450 receptors into the trillion potential smells available. And further, to attach that to meaning, we would need, again as mentioned above, an entire body, and more than that, a body that has lived from birth. A Frankenstein created at 20 years old would not be able to smell. This must be a baby Frankenstein we’re talking about here, zygote even.

In closing, we can’t have an electronic nose that is “open ended.” It can look for particular things on Zillow – mold? Wet paint? (who cares) Frito Feet? (that’s the smell of dog feet, which could indicate a pet lived in the house?). Thanks for listening.

Notes:

Electronic nose using CMOS integrated circuits analyzes breath

phys.org, June 2016