Liquor-Store Spirits Provide Green Alternative To HPLC Solvents | Chemical & Engineering News
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Web Date: April 17, 2015

Liquor-Store Spirits Provide Green Alternative To HPLC Solvents

Analytical Chemistry: Rum or vodka combined with household products produces high-quality results when used in high-performance liquid chromatography
Department: Science & Technology | Collection: Green Chemistry
News Channels: Analytical SCENE, Environmental SCENE, Organic SCENE
Keywords: high-performance liquid chromatography, HPLC, eluents, acetonitrile, ethanol, grain alcohol, liquor, distilled spirits
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Green Chromatography?
Alcohol spirits can replace expensive and hazardous chemicals in high-performance liquid chromatography.
Credit: Shutterstock
Photo of liquor bottles.
 
Green Chromatography?
Alcohol spirits can replace expensive and hazardous chemicals in high-performance liquid chromatography.
Credit: Shutterstock

Long considered a lab workhorse, high-performance liquid chromatography (HPLC) typically requires expensive chemicals that need to be disposed of as hazardous waste. A new study shows that rum, vodka, and other distilled alcohols combined with household products can serve as low-cost and sustainable alternative eluents for HPLC, and in many cases produce excellent analytical results (ACS Sustainable Chem. Eng. 2015, DOI: 10.1021/acssuschemeng.5b00133).

Chemists most often use the solvent acetonitrile in HPLC separations to elute the components of mixtures from the instrument’s chromatographic column. During a worldwide shortage of acetonitrile in 2009, which caused the price to skyrocket, researchers found that ethanol was a good substitute. Still, the cost of HPLC-grade absolute ethanol is high, typically about $120/L.

Recent innovations have reduced the size and cost of HPLC-based instruments, raising the possibility that HPLC could someday be used in doctors’ offices and in labs in developing countries. So Erik L. Regalado, Christopher J. Welch, and colleagues of Merck Research Laboratories, in Rahway, N.J., wanted to see if cheaper and more readily available solvents could perform as well as HPLC-grade ethanol.

The researchers combined distilled spirits purchased from a local liquor store with ammonia and white vinegar from a supermarket and used the eluents to separate a mixture of five compounds—uracil, caffeine, 1-phenylethanol, butylparaben, and anthracene—in a conventional HPLC instrument.

In HPLC, compounds separate based on how quickly they move through the instrument’s column. The team found that grain alcohol, which cost $22/L, was a good substitute for HPLC-grade ethanol, especially when analyzing more hydrophilic compounds that move slowly through the column. Rum and the lower-proof alcohols were less effective at eluting the strongly retained components, but they cleanly separated compounds that came off the column in a shorter time. The liquor-store alcohol-based eluents also performed as well as HPLC-grade ethanol in HPLC combined with mass spectrometry (HPLC/MS) when measuring caffeine and theanine in brewed black teas and vitamin C from oranges and supplement pills.

Similar analyses on a microfluidic HPLC instrument required much less solvent. One high-throughput analysis of vanillin in a vanilla extract showed that a single “airline serving” of vodka was sufficient for 1,560 assays.

“In effect, distilled alcohol spirits are just a more convenient and more economical way to obtain ethanol,” Welch says. The liquors they tested—rum, vodka, cachaça, and aguardiente—contained at most 40% ethanol, while the grain alcohol was 95%.

The researchers admit these analytical results could be performed more quickly and perhaps with finer resolution using acetonitrile, which costs $50 to $130/L. “However, the green chemistry and cost advantages of this method open up some interesting possibilities for the use of HPLC/MS technologies outside the conventional laboratory setting,” Welch says.

Larry Miller, a principal scientist at Amgen and president of the nonprofit Green Chemistry Group, agrees that the nonhazardous substances can perform chromatographic separations that, in many cases, are roughly equivalent to using acetonitrile. “But there are still challenges, including the price and availability of the smaller instruments, that would have to be overcome before HPLC/MS can be routinely used in nontraditional settings,” Miller says.

 
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Comments
Louise Slade (April 18, 2015 8:41 PM)
Acetonitrile is an aprotic solvent, like ethyl acetate, another valuable aprotic chromatography solvent. Compounds that require the use of aprotic solvents would suffer with vodka (ethanol), vinegar (acetic acid), and water.
Schuyler Corry (April 23, 2015 1:19 AM)
They're talking about reversed phase HPLC. That typically uses water with varying amounts of acetonitrile, so wouldn't be suitable for any compound that can't handle protic solvents. Also, even the highest proof grain alcohol is a 95:5 azeotrope with water, while the lower proof alcohols are as low as 40% ethanol.

If you want a greener solvent for normal phase chromatography, CO2 is the way to go. I hear nice things about methyl THF as well.
Richard Goodin (April 20, 2015 3:30 PM)
An additional disadvantage of ethanol water mixtures is that they are much more viscous than Acetonitrile and result in high back pressures. Many UPLC methods are limited to 10000 PSI and older HPLC systems are limited to 4000 PSI
Matt Bosma (April 22, 2015 5:26 PM)
What is the long term effect of some of the "non-volatile" componenets of these non-traditional mobile phases? Will there be some "ghost" peaks associated with retained compounds that elute slowly? What about UHPLC and the sub micron frits - do they get clogged easier? What about the source in the MS units - will they be compromised by the quality?
Handles (April 22, 2015 8:20 PM)
Who pays $50 a litre for HPLC acetonitrile? I pay less than USD 20/L here in Australia, and the World Banks recent ICP report ranks us the fourth most expensive country in the world.

Benedetto Raimondi (April 23, 2015 4:06 PM)
I am an Italian chemistry teacher.
Italian schools are strongly penalized by the lack of money. I really hope that my students do with these separations HPLC green-eluents. It is also true that these green-eluents are much more viscous than acetonitrile but patience, they will work on separations that do not require it.
Robert Buntrock (April 24, 2015 4:19 PM)
Very interesting. Apparently, the presence of 5% water in the 95% ethanol (more of course in vodka, rum, etc.) does not interfere with the chromatography. When I was back in the lab, decades ago, 95% grain alcohol was available tax free for research purposes in the Midwest for presumably a lower price in bulk. When I went East for grad school, the avialble tax free research ethanol was 100%, synthetic from hydration of ethylene, and was dispensed in revenue stamp sealed quart bottles. of course, to run consistent UV spectra, we had to dilute it. Again, I have no idea what the cost was.
Tony Martin (April 24, 2015 6:11 PM)
One big problem might be keeping people out of it. They used to add phenolphalein to the 95% grain alcohol(led to some sick under graduates). but you couldn't do that with a HPLC solvent. Sounds like a interesting project.
Robert Buntrock (May 1, 2015 4:11 PM)
95% Ethanol has been the standard solvent for UV spectra for decades, no denaturant allowed. It's up toe lab management and lab mentors to keep everyone honest. Use of non-denatured ethanol is highly regulated with tax free stamps and inventory control. See my other note.

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