{"id":684340,"date":"2026-05-21T14:57:10","date_gmt":"2026-05-21T14:57:10","guid":{"rendered":"https:\/\/www.newsbeep.com\/ca\/684340\/"},"modified":"2026-05-21T14:57:10","modified_gmt":"2026-05-21T14:57:10","slug":"study-points-to-ammonia-contamination-in-water-microdroplets-saga-research","status":"publish","type":"post","link":"https:\/\/www.newsbeep.com\/ca\/684340\/","title":{"rendered":"Study points to ammonia contamination in water microdroplets saga | Research"},"content":{"rendered":"

New mass spectrometry\u00a0experiments challenge water microdroplet\u2019s purported ability to spontaneously generate hydroxyl radicals. Led by Ryan Julian<\/a> at the University of California, Riverside, US, the experiments point to trace ammonia contamination mimicking the signals previously attributed to these reactive species.<\/p>\n

Water microdroplets are typically about 10\u03bcm in size. They\u2019re generated naturally in the atmosphere, or using tools like ultrasonic humidifiers or gas nebulisers. The ions that do, or do not, form spontaneously within them have been a subject of significant debate since 2019, when Richard Zare<\/a> of Stanford University in the US announced that sprays of microscopic water droplets spontaneously produce hydrogen peroxide<\/a>.<\/p>\n

Spraying pure water into a mass spectrometer, Zare observed an ion at m\/z 36, which he interpreted as a hydroxyl radical as either [H3O + \u2022OH]+ or [H2O\u2022 + H2O]+. He also exposed two radical scavengers, melatonin and caffeine, to water microdroplets. The resulting spectra showed peaks 17Da above the m\/z of the protonated drugs, which he took to be their oxidised forms, and proof that the microdroplets contained hydroxyl radicals.\u00a0<\/p>\n

\u2018That was really the first report of something really unusual in a droplet. Since that time, people have debated whether that is a correct result,\u2019 explains Evan Williams<\/a> who researches mass spectrometry at the University of California, Berkeley, US, and was not involved in either study.\u00a0<\/p>\n

Julian had not followed the water microdroplet debate<\/a> prior to this research, first encountering it at a conference. \u2018Definitely it didn\u2019t seem to be making a lot of sense to me,\u2019 he says. While previous work presented alternative explanations for Zare\u2019s results, until now, no one has faithfully reproduced his original data. \u2018If you can reproduce the original results on which everything was based and show that it\u2019s all not what it was represented to be, then it\u2019s pretty difficult to argue against that,\u2019 says Julian.<\/p>\n

Working with graduate student Aidan Purcell, Julian used gas flow nebulisation on LC\/MS grade water to produce microdroplets in the absence of any voltage. The resulting spectra showed the expected large m\/z 36 peak, but when this ion was subjected to collision-induced dissociation (CID), the researchers saw m\/z 18, the expected mass for NH4+, not m\/z 19, which would correspond to H3O+.\u00a0<\/p>\n

Notably, the gas flow nebulisation data did not show a peak at m\/z 37, where [H3O + H2O]+ would be. \u2018That\u2019s the dominant ion that you expect to get from a protonated water droplet,\u2019 explains Williams. Its absence is further proof that m\/z 36 corresponds to protonated ammonia, not water, argues Julian.\u00a0<\/p>\n

When the team instead electrosprayed water into the mass spectrometer, a technique known to produce highly protonated water droplets through voltage input, a peak at m\/z 37 appeared alongside the one at m\/z 36. CID of the m\/z 37 peak gave m\/z 19, corresponding to H3O+, whereas CID of m\/z 36 again yielded m\/z 18, corresponding to NH4+.\u00a0<\/p>\n

\"Mass<\/p>\n

To be certain that the observed m\/z 18 CID products do correspond to NH4+, the researchers repeated the nebulisation and electrospray experiments using 18O water. Again, they saw a peak at m\/z 36, as well as one at m\/z 38 that they interpreted as [NH4 + H218O]+, but nothing at m\/z 40, which would correspond to [18OH3 + \u202218OH]+. CID of m\/z 36 and 38 peaks yielded exclusively m\/z 18 ions, consistent with NH4+ but not [18OH2]+\u2022, which would have given a m\/z 20 peak.\u00a0<\/p>\n

Williams describes this result as compelling, noting that \u00b9\u2078O labels water but not ammonia, making it a definitive test. And to him, ammonia contamination makes a lot of sense. As well as being a common solvent contaminant, \u2018your breath contains a few hundred parts per billion of ammonia. You also exude more ammonia out of your skin than you actually breathe, so even if you hold your breath, ammonia is going to be in the air around the instrument,\u2019 he explains.\u00a0<\/p>\n

Himanshu Mishra<\/a>, an environmental science and engineering professor at King Abdullah University of Science and Technology in Saudi Arabia, has long questioned Zare\u2019s experimental results<\/a>. He describes Julian\u2019s findings as beautifully logical, authoritative, and \u2018an important salvo in the field\u2019. Williams echoes these thoughts: \u2018Ryan Julian does a very elegant job breaking this ion up and showing that the results are consistent with protonated ammonia with a water molecule and that they are not consistent with protonated water with a hydroxyl radical.\u2019\u00a0<\/p>\n

Both Mishra and Williams note that several experiments disproving Zare\u2019s hypothesis have already been published, but that Julian\u2019s contribution was necessary for the water microdroplet debate to advance. However, no one Chemistry World spoke to believes this work will put an end to the debate, and Julian is prepared for pushback on it. \u2018I know other people who\u2019ve been involved with this controversy have had people question, \u201cwhy did you bother to do this?\u201d or say \u201cyou\u2019re just being a jerk\u201d\u2026 But at the end of the day science needs to be right for us to move on and progress, and so there\u2019s not really another way to do it, other than to publish diverging opinions where they exist.\u2019\u00a0<\/p>\n

Zare declined to comment.\u00a0<\/p>\n","protected":false},"excerpt":{"rendered":"New mass spectrometry\u00a0experiments challenge water microdroplet\u2019s purported ability to spontaneously generate hydroxyl radicals. Led by Ryan Julian at…\n","protected":false},"author":2,"featured_media":684341,"comment_status":"","ping_status":"","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[7],"tags":[49,48,66],"class_list":["post-684340","post","type-post","status-publish","format-standard","has-post-thumbnail","category-science","tag-ca","tag-canada","tag-science"],"_links":{"self":[{"href":"https:\/\/www.newsbeep.com\/ca\/wp-json\/wp\/v2\/posts\/684340","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.newsbeep.com\/ca\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.newsbeep.com\/ca\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.newsbeep.com\/ca\/wp-json\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"https:\/\/www.newsbeep.com\/ca\/wp-json\/wp\/v2\/comments?post=684340"}],"version-history":[{"count":0,"href":"https:\/\/www.newsbeep.com\/ca\/wp-json\/wp\/v2\/posts\/684340\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.newsbeep.com\/ca\/wp-json\/wp\/v2\/media\/684341"}],"wp:attachment":[{"href":"https:\/\/www.newsbeep.com\/ca\/wp-json\/wp\/v2\/media?parent=684340"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.newsbeep.com\/ca\/wp-json\/wp\/v2\/categories?post=684340"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.newsbeep.com\/ca\/wp-json\/wp\/v2\/tags?post=684340"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}