{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,3,15]],"date-time":"2026-03-15T04:49:40Z","timestamp":1773550180973,"version":"3.50.1"},"reference-count":31,"publisher":"Wiley","issue":"22","license":[{"start":{"date-parts":[[2025,9,23]],"date-time":"2025-09-23T00:00:00Z","timestamp":1758585600000},"content-version":"vor","delay-in-days":0,"URL":"http:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"DOI":"10.13039\/501100004240","name":"Akademie V\u011bd \u010cesk\u00e9 Republiky","doi-asserted-by":"publisher","award":["RVO 61388963"],"award-info":[{"award-number":["RVO 61388963"]}],"id":[{"id":"10.13039\/501100004240","id-type":"DOI","asserted-by":"publisher"}]},{"DOI":"10.13039\/501100004240","name":"Akademie V\u011bd \u010cesk\u00e9 Republiky","doi-asserted-by":"publisher","id":[{"id":"10.13039\/501100004240","id-type":"DOI","asserted-by":"publisher"}]}],"content-domain":{"domain":["analyticalsciencejournals.onlinelibrary.wiley.com"],"crossmark-restriction":true},"short-container-title":["Electrophoresis"],"published-print":{"date-parts":[[2025,11]]},"abstract":"<jats:title>ABSTRACT<\/jats:title>\n                  <jats:p>\n                    This work focuses on the separation of oligonucleotides (ONs) in a free solution by capillary electrophoresis\u2014mass spectrometry (CE\u2010MS). Specifically, we evaluated a combination of separation in acidic background electrolytes (BGEs), nanospray ionization, and time\u2010of\u2010flight mass spectrometry in positive mode. A mixture of synthetic ONs, ranging in length from 15 to 78\u00a0nt, was employed as the test compounds. The key to a good separation selectivity of ONs lies in the different protonation of individual nucleobases. To this end, we assessed the acidity constant (p\n                    <jats:italic>K<\/jats:italic>\n                    <jats:sub>a<\/jats:sub>\n                    ) of the nucleobases in nucleotides experimentally as 3.3 for adenine, 4.4 for cytosine, 2.5 for guanine, and &lt;\u00a02 for thymine. From a set of separations in the 2\u20139\u00a0pH range, it was found that optimum peak shape and resolution are achieved in the interval of acidic pH 2\u20132.5. The BGE can be conveniently composed of either formic acid (FA) or a combination of ammonium hydroxide and FA. Nanospray ionization provided ions with charge numbers ranging from +4 to +8, proportional to the length of the ON. For short sequences, sheath liquid (SL) comprising 0.5%\u20131% (v\/v) FA + 20% (v\/v) methanol was sufficient in order to generate ions in positive mode MS, whereas a stronger SL of 5% (v\/v) FA + 20% (v\/v) methanol was required for longer ON sequences of approximately &gt;\u00a040\u00a0nt.\n                  <\/jats:p>","DOI":"10.1002\/elps.70036","type":"journal-article","created":{"date-parts":[[2025,9,24]],"date-time":"2025-09-24T06:55:26Z","timestamp":1758696926000},"page":"1621-1629","update-policy":"https:\/\/doi.org\/10.1002\/crossmark_policy","source":"Crossref","is-referenced-by-count":1,"title":["Free Solution Oligonucleotide Separation by CE\u2010MS in Acidic Buffers and Positive ESI Ionization"],"prefix":"10.1002","volume":"46","author":[{"ORCID":"https:\/\/orcid.org\/0000-0003-1811-3145","authenticated-orcid":false,"given":"Maria","family":"Butnariu","sequence":"first","affiliation":[{"name":"Institute of Organic Chemistry and Biochemistry of the Czech Academy of Sciences  Prague Czech Republic"},{"name":"Department of Analytical Chemistry Faculty of Science Charles University  Prague Czech Republic"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-0379-8428","authenticated-orcid":false,"given":"Veronika","family":"\u0160ol\u00ednov\u00e1","sequence":"additional","affiliation":[{"name":"Institute of Organic Chemistry and Biochemistry of the Czech Academy of Sciences  Prague Czech Republic"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-6424-3891","authenticated-orcid":false,"given":"Du\u0161an","family":"Koval","sequence":"additional","affiliation":[{"name":"Institute of Organic Chemistry and Biochemistry of the Czech Academy of Sciences  Prague Czech Republic"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-1719-1432","authenticated-orcid":false,"given":"V\u00e1clav","family":"Ka\u0161i\u010dka","sequence":"additional","affiliation":[{"name":"Institute of Organic Chemistry and Biochemistry of the Czech Academy of Sciences  Prague Czech Republic"}],"role":[{"role":"author","vocabulary":"crossref"}]}],"member":"311","published-online":{"date-parts":[[2025,9,23]]},"reference":[{"key":"e_1_2_9_2_1","doi-asserted-by":"publisher","DOI":"10.1038\/s41565-021-00898-0"},{"key":"e_1_2_9_3_1","doi-asserted-by":"publisher","DOI":"10.1002\/jssc.202000833"},{"key":"e_1_2_9_4_1","doi-asserted-by":"publisher","DOI":"10.1038\/s41598-023-36193-2"},{"key":"e_1_2_9_5_1","doi-asserted-by":"publisher","DOI":"10.1021\/jasms.3c00217"},{"key":"e_1_2_9_6_1","doi-asserted-by":"publisher","DOI":"10.1016\/j.jpba.2022.114928"},{"key":"e_1_2_9_7_1","doi-asserted-by":"publisher","DOI":"10.1016\/j.trac.2023.117215"},{"key":"e_1_2_9_8_1","doi-asserted-by":"publisher","DOI":"10.1002\/1521-3773(20001215)39:24<4463::AID-ANIE4463>3.0.CO;2-8"},{"key":"e_1_2_9_9_1","doi-asserted-by":"publisher","DOI":"10.1126\/science.1058040"},{"key":"e_1_2_9_10_1","doi-asserted-by":"publisher","DOI":"10.1016\/j.ygeno.2015.11.003"},{"key":"e_1_2_9_11_1","doi-asserted-by":"publisher","DOI":"10.3390\/biology12070997"},{"key":"e_1_2_9_12_1","doi-asserted-by":"publisher","DOI":"10.1002\/elps.200410278"},{"key":"e_1_2_9_13_1","doi-asserted-by":"crossref","unstructured":"L.Pont M.Vergara\u2010Barber\u00e1n andE. 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