{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,10,1]],"date-time":"2026-10-01T12:51:52Z","timestamp":1790859112957,"version":"4.1.0"},"reference-count":9,"publisher":"Oxford University Press (OUP)","issue":"10","license":[{"start":{"date-parts":[[2008,10,1]],"date-time":"2008-10-01T00:00:00Z","timestamp":1222819200000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/academic.oup.com\/journals\/pages\/open_access\/funder_policies\/chorus\/standard_publication_model"}],"funder":[{"DOI":"10.13039\/100007812","name":"University of Washington","doi-asserted-by":"publisher","id":[{"id":"10.13039\/100007812","id-type":"DOI","asserted-by":"publisher"}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":[],"published-print":{"date-parts":[[2008,10,1]]},"abstract":"<jats:title>Abstract<\/jats:title>\n               <jats:p>Background: High-performance liquid chromatography\u2013tandem mass spectrometric (LC-MS\/MS)1 analysis of plasma free metanephrines is the most diagnostically sensitive and specific screening test for the diagnosis of pheochromocytoma. We sought to develop an in-house method for this expensive test<\/jats:p>\n               <jats:p>Methods: We used off-line isopropanol protein precipitation of plasma to remove interfering substances before LC-MS\/MS analysis. We compared the extraction efficiency and limits of quantification of protein precipitation to those of previously reported solid-phase techniques.<\/jats:p>\n               <jats:p>Results: The new method had limits of quantification of 0.09 nmol\/L and 0.17 nmol\/L for metanephrine and normetanephrine, respectively. Method comparison with a previously described solid-phase extraction method revealed Deming regression slopes of 0.904 and 0.994, intercepts of 0.007 and 0.023, and SEs of the residuals (Sy|x) of 0.071 and 0.284 for metanephrine and normetanephrine, respectively. Extraction efficiency of isopropanol protein precipitation was 66% for metanephrine and 35% for normetanephrine, results that were superior to the efficiencies of 4% and 1% for our adapted solid-phase extraction method. No ion suppression was observed at the retention times for metanephrine and normetanephrine.<\/jats:p>\n               <jats:p>Conclusions: Isopropanol protein precipitation is a novel and effective off-line sample preparation method for metanephrines that offers a less expensive alternative to on-line solid-phase extraction for low-volume testing and requires a sample volume of only 200 \u03bcL. The mass spectrometric analysis time is equivalent to that of solid-phase techniques.<\/jats:p>","DOI":"10.1373\/clinchem.2008.104083","type":"journal-article","created":{"date-parts":[[2008,8,7]],"date-time":"2008-08-07T20:44:41Z","timestamp":1218141881000},"page":"1729-1732","source":"Crossref","is-referenced-by-count":49,"title":["Isopropanol Protein Precipitation for the Analysis of Plasma Free Metanephrines by Liquid Chromatography\u2013Tandem Mass Spectrometry"],"prefix":"10.1093","volume":"54","author":[{"given":"Luke C","family":"Marney","sequence":"first","affiliation":[{"name":"Department of Laboratory Medicine, University of Washington, Seattle, WA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Thomas J","family":"Laha","sequence":"first","affiliation":[{"name":"Department of Laboratory Medicine, University of Washington, Seattle, WA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Geoffrey S","family":"Baird","sequence":"first","affiliation":[{"name":"Department of Laboratory Medicine, University of Washington, Seattle, WA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Petrie M","family":"Rainey","sequence":"first","affiliation":[{"name":"Department of Laboratory Medicine, University of Washington, Seattle, WA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Andrew N","family":"Hoofnagle","sequence":"first","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"286","published-online":{"date-parts":[[2008,10,1]]},"reference":[{"key":"2020022800155751200_R1","first-page":"1427","volume":"287","year":"2002","journal-title":"JAMA"},{"key":"2020022800155751200_R2","doi-asserted-by":"crossref","first-page":"2","DOI":"10.1186\/1472-6823-4-2","volume":"4","year":"2004","journal-title":"BMC Endocr Disord"},{"key":"2020022800155751200_R3","doi-asserted-by":"crossref","first-page":"2957","DOI":"10.1001\/archinte.160.19.2957","volume":"160","year":"2000","journal-title":"Arch Intern Med"},{"key":"2020022800155751200_R4","doi-asserted-by":"crossref","first-page":"331","DOI":"10.1124\/pr.56.3.1","volume":"56","year":"2004","journal-title":"Pharmacol Rev"},{"key":"2020022800155751200_R5","doi-asserted-by":"crossref","first-page":"603","DOI":"10.1373\/clinchem.2003.024703","volume":"50","year":"2004","journal-title":"Clin Chem"},{"key":"2020022800155751200_R6","doi-asserted-by":"crossref","first-page":"1684","DOI":"10.1373\/clinchem.2007.087114","volume":"53","year":"2007","journal-title":"Clin Chem"},{"key":"2020022800155751200_R7","doi-asserted-by":"crossref","first-page":"1041","DOI":"10.1373\/49.7.1041","volume":"49","year":"2003","journal-title":"Clin Chem"},{"key":"2020022800155751200_R8","doi-asserted-by":"crossref","first-page":"1175","DOI":"10.1002\/(SICI)1097-0231(19990630)13:12<1175::AID-RCM639>3.0.CO;2-0","volume":"13","year":"1999","journal-title":"Rapid Commun Mass Spectrom"},{"key":"2020022800155751200_R9","doi-asserted-by":"crossref","first-page":"880","DOI":"10.1309\/LQ8U3UL956ET324X","volume":"126","year":"2006","journal-title":"Am J Clin Pathol"}],"container-title":["Clinical Chemistry"],"original-title":[],"language":"en","link":[{"URL":"http:\/\/academic.oup.com\/clinchem\/article-pdf\/54\/10\/1729\/32672997\/clinchem1729.pdf","content-type":"application\/pdf","content-version":"vor","intended-application":"syndication"},{"URL":"http:\/\/academic.oup.com\/clinchem\/article-pdf\/54\/10\/1729\/32672997\/clinchem1729.pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2020,2,28]],"date-time":"2020-02-28T00:18:22Z","timestamp":1582849102000},"score":1,"resource":{"primary":{"URL":"https:\/\/academic.oup.com\/clinchem\/article\/54\/10\/1729\/5628551"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2008,10,1]]},"references-count":9,"journal-issue":{"issue":"10","published-online":{"date-parts":[[2008,10,1]]},"published-print":{"date-parts":[[2008,10,1]]}},"URL":"https:\/\/doi.org\/10.1373\/clinchem.2008.104083","relation":{},"ISSN":["0009-9147","1530-8561"],"issn-type":[{"value":"0009-9147","type":"print"},{"value":"1530-8561","type":"electronic"}],"subject":[],"published-other":{"date-parts":[[2008,10,1]]},"published":{"date-parts":[[2008,10,1]]}}}