Chemistry World Podcast - June 2008
00:10 -- Introduction
02:00 -- How carbon nanotubes measure the strength of hot chilli sauces
04:14 -- The mystery aroma of Shiraz has been revealed - and it's peppery
07:00 -- Andy Meharg explains his research measuring potentially dangerous levels of arsenic in rice
10:48 -- A chemical compass clue to the mystery of bird migration
13:35 -- Electronics' missing link has been found: the nanoscale memristor
16:54 -- Andrea Sella laments the vanishing art of glassblowing
22:15 -- X-ray crystal studies suggest governments should stockpile a selection of bird flu drugs
25:32 -- Spinach can ward off stomach ulcers, thanks to bacteria in the mouth
27:39 -- The first artificial element, and this month's wine-based conundrum
(Promo)
Brought to you by the Royal Society of Chemistry, this is the Chemistry World Podcast.
(End Promo)
(00:10 -- Introduction)
Interviewer - Chris Smith
Hello! Welcome to Chemistry World with Mark Peplow, James Mitchell Crow, Victoria Gill, Richard Van Noorden, and I'm Chris Smith. This month: why rice isn't necessarily nice.
Interviewee - Andy Meharg
Baby rice we have looked at has high levels of inorganic arsenic in it, purchased within the UK, but we don't know what effects the carcinogen might cause at those early stages of development, but all the evidence seems to suggest that the risks are higher from the effects of exposure during early infancy.
That's Andy Meharg who recently analyzed the rice that we import into Britain and found that it contains worryingly high levels of arsenic. There will be more from him shortly. Also be careful with your glassware, because before long there may be no one around, who is capable of repairing it.
Interviewee - Andrea Sella
Consider for example, University College London, where I work, there used to be eight glassblowers and with time, as these people have retired, they have not been replaced. The result is we only have one glassblower.
Andrea Sella and he will be turning his blow torch on the system, that's doing away with glassblowers later in the program. Plus Popeye thanked spinach for making his muscles bulge, but the chances are, those have given him the cast-iron stomach too.
Interviewee - Victoria Gill
According to new Swedish research, a diet rich in nitrates, in vegetables that contain high level of nitrates, particularly spinach, which is very high in nitrates, can protect you against stomach ulcers.
The science of spinach is on the way. Meanwhile, did you manage to solve last month's Chemical Conundrum?
Interviewee - Mark Peplow
What was the world's first artificial element?
Well! The answer is on the way, and if you sent in a solution, keep listening to find out if you are one of this month's winners.
The Chemistry World Podcast is brought to you by the Royal Society of Chemistry. Look us up online at chemistryworld dot org
(End Advertisement)
(02:00 -- How carbon nanotubes measure the strength of hot chilli sauces)
Now Mark, you've promised to tantalize my taste buds this month.
Yeah that's right. Do you like a curry, Chris?
I'm very partial to curry.
But have you have ever wondered how you can measure, how hot a hot curry is? There is a new method in town and it uses latest technology. It uses carbon nanotubes to actually measure how hot your hot curry or your hot sauce is. Now the old fashion way of measuring the heat of a Tabasco sauce or something like that is based on the Scoville rating. Basically what happens is you take some food and you dilute it continually until a panel of experts can't actually detect any of that spicy heat anymore.
So, give us an example then, a vindaloo versus some kind of softer curry like korma or something?
Well, in terms of the peppers and spices that go in that, if you are looking down a Cayenne pepper or something like that, you might have a Scoville rating of about 30,000. Whereas if you go up to a Scotch bonnet and you are in the hundreds of thousands.
With the pure chemical itself?
The main chemical that's responsible for this heat is capsaicin and that's 15 or 16 million on the Scoville rating that means you have to dilute it that many times before it is undetectable in the sample.
So, what are researchers doing with the nanotubes to make this easier?
Basically, the carbon nanotube, which are like tiny rolled up straws of carbon atoms, tens of thousands of times thinner than a human hair, they have this electrochemical response when a capsaicin molecule attaches to it, changes the current that flows through it basically, and you can measure that and effectively turn into a measure of how many capsaicin molecules there are in the sample you are looking at.
So it is much more sort of standardized and it is much easier to get reproducible hotness levels.
The key thing is of course, these days in factories they don't always have a panel of experts standing around. So, there is a way that you can do this using high performance liquid chromatography, where you should measure the individual amounts of all the range of capsaicin compounds that are in it, but actually this is never a reliable method and cost of the kit is tens of thousands of pounds.
But presumably with this, you could deploy it, like some kind of even handheld analyzer that you could dip into a curry.
And that's exactly what the scientists developing this thing they can do. When we spoke to Richard Compton, whose team developed this at Oxford University, they are working on something that could be effectively a handheld device, costing something around 30 quid.
Most certainly a hot and peppery story.
(04:14 -- The mystery aroma of Shiraz has been revealed - and it's peppery)
And talking of hot and peppery, James, you've got something interesting in the wine industry here as well.
Interviewee - James Mitchell Crow
Yeah that's right, Chris. If you've ever opened a bottle of Australian Shiraz and thought, you detected a hint of pepper in the bouquet that oozed out of the bottle, you'd be spot on. Wine makers have long-known that certain vintages of Shiraz do have particularly peppery flavour to the aroma and researchers at the Australian wine research institute took up the challenge of trying to work out exactly what this peppery compound was?
How did they do that?
Well, they analyzed the wine using a technique called GC-MS, which is basically Gas Chromatography combined with Mass Spect, but also sniffing the compounds that come out at the end of the GC.
Sounds like some research, so what did they find?
Oh! They found that the compound responsible was a natural product called Rotundone, which had been isolated back in the '60s, but never been noted for its flavour before, but when they took a sniff of this stuff, they were really struck by how similar it smelled to peppercorns themselves. So, these guys went and brought us a few peppercorns, ground them up and tested those as well and were surprised to find that this compound actually is found in peppercorns as well, not only is it found there, but it is by far the strongest flavour compound in peppercorns.
So, what is it doing in the wine?
Well, it's just naturally produced by the grapes and ends up in the wine in the final product.
Why doesn't the grape taste peppery then, why just the wine?
It depends on your insensitivity to the compound as it turns out. Certain people are very sensitive to this compound and so they probably would say that the grape extract tastes quite peppery. Interestingly, other people are not sensitive to this compound even at very high concentrations. So the highest concentrations these guys tested was 400 nanograms per litre, just in pure water, 20% of their panel of testers couldn't detect it all, whereas other people were detecting it at only 8 nanograms per litre. That suggests that some people drinking a bottle of wine would be experiencing in any way, different to other people.
So do you think, given that the people now know about this stuff that they will be synthetically producing and putting in loads of wines to make a really cheap nasty wine taste really good and high quality.
I think, the approach that these guys are taking is now that they know what the compound is they can analyze different wines grown in different climates or made use in different wine making techniques and work out which wines it is particularly that has a high level of this compound and so then use those techniques if they want to improve or increase the amount of this flavour to make a peppery wine.
Thanks James. So now you know, in order to fool people into thinking it's a really expensive Pinot, you just have to reach for the pepper grinder. Now talking of pepper, Mark mentioned the spicy stuff, and a common accompaniment for curry is rice, but you might want to switch to Nan breads from now on as Andy Meharg explains.
(07:00 -- Andy Meharg explains his research measuring potentially dangerous levels of arsenic in rice)
Interviewee - Andrew Meharg
Well! We've been looking at arsenic levels in rice, it's becoming apparently clear that rice compared to most of the food in fact especially all other food has the highest levels of arsenic for a staple that is something that is eaten routinely and regularly by people.
Why do you think it does have such a high level?
Well, there is two major reasons for that. One is that rice unlike firstly every other major staple crop is grown under flooded conditions, where the water levels have low oxygen in them and basically that changes the conditions in the soils. We call it reducing conditions and that changes the speciation of arsenic present in the soil, make them more mobile and more available to the plant and secondly, it's human pollution, so anthropogenic pollution, where specifically paddy fields are being contaminated through range of processes such as pesticide application or industrial effluent.
And the levels of arsenic that you are detecting, how high are they in the grand scheme of things.
The only real comparisons we have are with water standards, because water is really quite regulated throughout the world including within the EU and within Britain, but food is very poorly regulated, but when we look at the element of inorganic arsenic which is this arsenic species or the form of the arsenic which is of concern, compared against the ones we have laid under EU regulations to have in water, then take some arsenic from rice to be quite considerable for those people who eat high amounts or rice in their diets.
Are there geographical hotspots, so if we get rice from a certain place, is that going to be worse than rice from another place?
Yes, rice imported from the US or imported from Europe tends to be much higher than rice imported from Southeast Asia or from Africa.
We knew it was a bit toxic, but why should we be more worried now that we have been since say 1959, when the levels we use today were set.
Because arsenic has not been classified as a non-threshold human carcinogen, i.e., the worst type of carcinogen. Basically no level of arsenic is safe. Every level of exposure we thought routinely will have cancer risk associated with that and that's lung and bladder cancer risk. So, when international bodies such as the WHO or national body such as USDA come to try and consider the risks posed by chemicals, they are basically for non-thresholds class I human carcinogens, say that they want to try and have zero exposure or the lowest exposure as possible.
And what do you think we should do about it?
I think we have to go back and set food standards for inorganic arsenic, which there are no food standards for inorganic arsenic within Europe or within UK and we should go back and reconsider what the safe levels of exposure, again those safe levels of exposure should really consider people who are taking high levels of arsenic into their diets and those are really quite surprised. They are these health-food conscious people and Asians are the main people.
Yes, because I would think that people are very worried because young babies might be even more vulnerable to the effect because a) they are going to have a longer lifetime exposure and b) they might be more vulnerable to the chemical effects as well.
Baby rice we've looked at has high levels of inorganic arsenic in it purchased within the UK, but we are to remember that they are only going to be on that baby rice for may be from 4 to 6 months, but again it can start, we don't know, what effects the carcinogen might cause at those early stages of development, but all the evidence seems to suggest that the risks are higher from the effects of exposure during early infancy than it is for an adult.
Aberdeen's University's Andy Meharg who has found high levels of arsenic in rice.
(10:48 -- A chemical compass clue to the mystery of bird migration)
Well let's change direction now and here's how scientists in Oxford have shown how chemicals can behave like compasses and respond to the earth's magnetic field, Victoria.
Yes, exactly. This is an entirely artificial compound that is being created by chemists, Peter Hore and Christiane Timmel at the University of Oxford, but it could be an analogue of the chemicals that are found in the cryptochromes in animal's eyes, which are sensitive to light. It's been a long hypothesis that animals use compounds that are sensitive to light to drive chemical reactions that then guide them and tell them where to migrate to, that's how swallows find their way from one hemisphere to the other when they migrate. But so far, no chemical has been found that is sensitive to the very, very tiny magnetic field that the Earth has.
So, what have they done to work out what's going on?
So, they have created an artificial compound that is sensitive to this tiny, 50 micro Tesla magnetic field, which is very approximately 100 times weaker than a Fridge magnet, and what they've done is they've made a molecule that comprises of a carotenoid, porphyrin and fullerene which is essentially a sphere of carbon atoms and this molecule dubbed CPF, they have shown in a chemical reaction that it is sensitive to this tiny magnetic field. Now when this CPF molecule is exposed to light, it goes to an excited state and it forms two radicals that are at either end of the molecules and it is these two radicals, these two unpaired electrons that make that molecule sensitive to the magnetic field. So, when the radicals in this molecule are exposed to the magnetic fields, they change their spins and move to a different state, and its this change of states that means that the molecule rather than just returning very quickly to its ground state, to its original state, it's a sort of slower process for it to go back to its ground state.
And how would you envisage if this was actually in a real animal, in a real eye. How would that, then be used to detect what the Earth's magnetic field was doing.
It's the speed of this reaction that changes the biochemical process within the eye that would then alter the chemical reactions that drive signalling processes, so once this reaction changes, it's going to change subsequent reactions and that is going to give the animal different information.
But basically what this shows is that what we've been debating for 30 years or so is that animals really possibly could detect the Earth's magnetic field because it's possible to produce molecules that are sensitive to magnetic fields of the very tiny strength of the Earth.
Yeah. Exactly! This is like I said, an entirely artificial molecule and they are not claiming that this is the stuff that is found in the cryptochromes within animals, but because they've shown chemically that it is possible; it could be very, very similar.
Well, from molecules that's going to tell magnetism to perhaps the missing link on the average circuit board, Richard what's this all about.
(13:35 -- Electronics' missing link has been found: the nanoscale memristor)
Interviewee - Richard Van Noorden
Yeah, really interesting, this one. US scientists have created a new circuit element called a memristor and in case you think this is just to do with electronics and therefore almost nothing to do with chemistry at all, it is actually a nanoscale thin film of titanium dioxide that has made this possible. It's actually fascinating what's going on inside this thing, but basically it's like a resistor with a memory. It remembers the voltage that's recently been put across it, or the charge that's recently been put through it, and then you can use that to make some very sophisticated circuits and in fact, shrink the size of components that you want fit on, say your computer chips.
But why would this be useful and what sorts of applications.
Well, first of all there is obviously a massive drive to get components as small as possible, to get chips smaller and smaller, to pack more components into the same space, and at the moment, transistors look like they are going to be hitting a wall in about 10 years from now, where you just can't make them any smaller. Now the interesting thing about this memristor is that it actually makes use of that effect to work, so the smaller it gets the better.
Talk us through how you actually make it and how it actually works?
I should say this is the work of Stan Williams, Hewlett-Packard labs in California and his team. You get a titanium dioxide film and you put it between platinum electrodes. Now it's about 5 nanometres thick. The bottom half of the film is just pure titanium dioxide, it's an insulator. The top half has vacancies where oxygen should have been and they are positively charged. Now when you apply your voltage, the vacancies move through into the bottom half, making the whole film conducting, charge can pass through it. Now you can un-switch the voltage and pull the vacancies back up again, making the film insulating.
But how does it remember, what's gone before?
If you just turn the voltage off, the dopants stay where they got to, so if you have the positive voltage pushing the dopants down to the bottom and there would be some level of conductivity there, you turn everything off the dopants stay where they are. You turn it on again; it remembers that previously there was a positive voltage applied to it so much. Now if you have a negative voltage, it pulls things back, but cleverly it doesn't go back in the same way that it went forward, there is a slight hysteresis, so it actually remembers whether you had a negative or positive voltage and it's so useful that people have tried to make this kind of architecture before, by putting together all the other elements of a circuit, resistors and inductors and certain architecture, but of course it was much large and more complicated bit of a kit.
How easy are these things to make and therefore will we actually be able to make these in an amount and at a size, which does make them commercially useful.
Well, that's the question and you just have to go by the word of Stan Williams. He says he has made chips with transistors, with memristors and he says it's quite feasible to make. Now, his team is the only one with the expertise to do it, so we all have to go on his way, but no doubt this will launch a flurry of research.
So making computer chips in future will be a PC of cake. Thanks Richard.
This is the Chemistry World podcast with me Chris Smith. Still to come, how bird flu is becoming resistant to antivirals and why spinach is good for your guts. But first to an under-appreciated art, especially where chemistry is concerned. Here's Andrea Sella.
(16:54 -- Andrea Sella laments the vanishing art of glassblowing)
I've been writing the classic kit column for Chemistry World for the last year and it's been a wonderful opportunity to really pick up and take a look at glassware and apparatus that is used in the lab. And one of the piece of glassware that I focussed on was something called a Vigreux's Column and it is a wonderful piece of glassware, which is used for distillations and it's a glass tube with indentations in it. I began to ask myself, who is Vigreux? Vigreux was a glassblower. Glassblowing has been absolutely essential for chemistry and to physics and to many of the physical sciences, really since the middle of the 19th Century.
Why is that, because the link is not immediately obvious?
Well, if you think about the work that chemists do, chemists work almost exclusively in glass until very recently when gradually when a bit of plastic and other materials, particularly vacuum systems out of stainless steel for example came in. Everybody worked either in glass or in quartz and the development of glass and the improvements in glass technology really altered the way in which chemists could work, but they really needed experts side by side who could actually build kits for them and I think one of the most spectacular examples is probably the work of Rutherford. When Rutherford was trying to characterize the different kinds of radioactivity, he had a real problem because the quantities were so tiny and he got the Manchester glassblower, a man called Otto Baumbach to make tiny capillaries and Baumbach who was really the only person who could make capillaries so fine, so narrow and so thin and in his papers when he characterized radon and shown that it was the emanation, Rutherford then thanked Baumbach saying that without him it wouldn't have been possible.
Well, these days we can just go to a manufacturer and we buy these things off the shelf, don't we?
As time has gone on there has been a huge amount of automation that has come in and there is no doubt that the conical flasks, the round bottom flasks, all of those things are pretty standard, but these loads of stuff, there are vacuum lines and things like that which really continue to have to be made by hand, they cannot be done by machine and so chemists still require glassblowers.
When we say glassblower though, are we talking about the stereotypical person who has got the big long pole in the hand, a furnace and big red cheeks where they've been blowing so hard?
Well, scientific glass blowing differs in essential ways from the work of the traditional artistic glassblower. Nowadays a lot of glassware components are first of all made of Pyrex, which is fantastic piece, it doesn't expand, it doesn't contract and so on, but we get tubing, we get round bottom flask and basic components that way and those are essentially automated. What the glassblower does is he takes these components and assembles them into more complex apparatus and so when you take a look at, for example, the twin manifold Schlenk line which is used by organic and organometallic chemists for handling air-sensitive materials, each and every one of those is made by hand by glassblowing.
So historically speaking I suppose, anywhere there was a big chemistry department, there would have been probably a whole triad of glassblowers producing the materials those people needed to their research.
Absolutely! I mean, if you consider for example, University College London where I work, there used to be 8 glassblowers, four of them are in chemistry and four of them are in physics and with time as these people have retired, they've not been replaced and to some extent that's reflection of the fact that we do buy an awful lot of kits straight off the shelf. But the result is that we only have one glassblower and what this is doing is breaking that longstanding link between the technical person downstairs who can quickly fix that crucial piece of apparatus at short notice and who has the expertise and the knowledge to be able to do these things.
And one presumes that unlike the glassware, we are very fond of using these days, you can't get those kind of people with that kind of calibre or skill off the shelf.
I was speaking to a man who actually owns a commercial glassblowing firm in London. He told me that he expected his employees to spend 6 years on their apprenticeship, before he could let them loose on a proper commercial contract.
How long is the chemistry Ph.D.?
Well, it is kind of interesting. A chemistry undergraduate will spend 4 years learning and then they will go on and do a 3 or 4 year Ph.D. So, actually the time spent by a glassblower isn't that far off from a chemistry graduate student and so these two skills, which used to go hand-in-hand that link is being lost and the other thing is that there are fewer and fewer people in chemistry departments who actually do any glassblowing themselves. I am only aware of two members of the staff in my department who have a glassblowing torch and who can even join together two pieces of glassware. I would like to think that I am one of them, I do terrible jobs that you know when I need to I can join stuff together and then there is another physical chemist who uses vacuum lines and who occasionally needs to sort of fix things up. But we are the last guys
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