{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,9,6]],"date-time":"2026-09-06T04:46:21Z","timestamp":1788669981549,"version":"build-2803163510"},"reference-count":39,"publisher":"Wiley","issue":"5","license":[{"start":{"date-parts":[[2018,1,15]],"date-time":"2018-01-15T00:00:00Z","timestamp":1515974400000},"content-version":"vor","delay-in-days":0,"URL":"http:\/\/onlinelibrary.wiley.com\/termsAndConditions#vor"}],"funder":[{"DOI":"10.13039\/501100003243","name":"Ministerstvo Zdravotnictv\u00ed Cesk\u00e9 Republiky","doi-asserted-by":"publisher","award":["00064203"],"award-info":[{"award-number":["00064203"]}],"id":[{"id":"10.13039\/501100003243","id-type":"DOI","asserted-by":"publisher"}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Clinical Laboratory Analysis"],"published-print":{"date-parts":[[2018,6]]},"abstract":"<jats:sec><jats:title>Background<\/jats:title><jats:p>New high\u2010performance liquid chromatography (<jats:styled-content style=\"fixed-case\">HPLC<\/jats:styled-content>) method was developed for the determination of vitamin K<jats:sub>1<\/jats:sub> and two forms of vitamin K<jats:sub>2<\/jats:sub> (<jats:styled-content style=\"fixed-case\">MK<\/jats:styled-content>\u20104 and <jats:styled-content style=\"fixed-case\">MK<\/jats:styled-content>\u20107) in human serum, and the levels of vitamin K\u00a0were determined in 350 samples of postmenopausal women.<\/jats:p><\/jats:sec><jats:sec><jats:title>Methods<\/jats:title><jats:p>Vitamin K was determined by <jats:styled-content style=\"fixed-case\">HPLC<\/jats:styled-content> with fluorescence detection after postcolumn zinc reduction. The detection was performed at 246\u00a0nm (excitation) and 430\u00a0nm (emission). The internal standard and 2\u00a0mL of ethanol were added to 500\u00a0\u03bcL of serum. The mixture was extracted with 4\u00a0mL of hexane, and solid phase extraction was then used.<\/jats:p><\/jats:sec><jats:sec><jats:title>Results<\/jats:title><jats:p>The <jats:styled-content style=\"fixed-case\">HLPC<\/jats:styled-content> method was fully validated. The intra\u2010 and interday accuracy and precision were evaluated on two <jats:styled-content style=\"fixed-case\">QC<\/jats:styled-content> samples by multiple analysis, and <jats:styled-content style=\"fixed-case\">CV<\/jats:styled-content> were less than 10%. The limit of quantification for <jats:styled-content style=\"fixed-case\">MK<\/jats:styled-content>\u20104 was found at 0.04 ng\/mL, for K<jats:sub>1<\/jats:sub> 0.03\u00a0ng\/mL, and for <jats:styled-content style=\"fixed-case\">MK<\/jats:styled-content>\u20107 0.03\u00a0ng\/mL. The mean recoveries of the corresponding compounds were 98%\u2010110%. Serum levels of <jats:styled-content style=\"fixed-case\">MK<\/jats:styled-content>\u20104, K<jats:sub>1<\/jats:sub>, and <jats:styled-content style=\"fixed-case\">MK<\/jats:styled-content>\u20107 in postmenopausal women with osteoporosis were 0.890\u00a0\u00b1\u00a00.291\u00a0ng\/mL, 0.433\u00a0\u00b1\u00a00.394\u00a0ng\/mL, and 1.002\u00a0\u00b1\u00a01.020\u00a0ng\/mL, respectively (mean\u00a0\u00b1\u00a0<jats:styled-content style=\"fixed-case\">SD<\/jats:styled-content>). Serum levels of <jats:styled-content style=\"fixed-case\">MK<\/jats:styled-content>\u20104, K<jats:sub>1<\/jats:sub>, and <jats:styled-content style=\"fixed-case\">MK<\/jats:styled-content>\u20107 in postmenopausal women without osteoporosis were 0.825\u00a0\u00b1\u00a00.266\u00a0ng\/mL, 0.493\u00a0\u00b1\u00a00.399\u00a0ng\/mL, and 1.186\u00a0\u00b1\u00a01.076\u00a0ng\/mL, respectively (mean\u00a0\u00b1\u00a0SD).<\/jats:p><\/jats:sec><jats:sec><jats:title>Conclusion<\/jats:title><jats:p>New <jats:styled-content style=\"fixed-case\">HPLC<\/jats:styled-content> method for the determination of vitamins K<jats:sub>1<\/jats:sub>, <jats:styled-content style=\"fixed-case\">MK<\/jats:styled-content>\u20104, and <jats:styled-content style=\"fixed-case\">MK<\/jats:styled-content>\u20107 in serum was evaluated and validated. This method is highly specific and sensitive with the low limit of quantification.<\/jats:p><\/jats:sec>","DOI":"10.1002\/jcla.22381","type":"journal-article","created":{"date-parts":[[2018,1,15]],"date-time":"2018-01-15T07:02:41Z","timestamp":1515999761000},"source":"Crossref","is-referenced-by-count":37,"title":["Determination of vitamins K<sub>1<\/sub>, <scp>MK<\/scp>\u20104, and <scp>MK<\/scp>\u20107 in human serum of postmenopausal women by <scp>HPLC<\/scp> with fluorescence detection"],"prefix":"10.1002","volume":"32","author":[{"ORCID":"https:\/\/orcid.org\/0000-0002-9903-5662","authenticated-orcid":false,"given":"Eva","family":"Klapkova","sequence":"first","affiliation":[{"name":"Department of Medical Chemistry and Clinical Biochemistry Charles University 2<sup>nd<\/sup> Faculty of Medicine and University Hospital Motol  Prague Czech Republic"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Jana","family":"Cepova","sequence":"additional","affiliation":[{"name":"Department of Medical Chemistry and Clinical Biochemistry Charles University 2<sup>nd<\/sup> Faculty of Medicine and University Hospital Motol  Prague Czech Republic"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Katerina","family":"Dunovska","sequence":"additional","affiliation":[{"name":"Department of Medical Chemistry and Clinical Biochemistry Charles University 2<sup>nd<\/sup> Faculty of Medicine and University Hospital Motol  Prague Czech Republic"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Richard","family":"Prusa","sequence":"additional","affiliation":[{"name":"Department of Medical Chemistry and Clinical Biochemistry Charles University 2<sup>nd<\/sup> Faculty of Medicine and University Hospital Motol  Prague Czech Republic"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"311","published-online":{"date-parts":[[2018,1,15]]},"reference":[{"key":"e_1_2_7_2_1","first-page":"303","article-title":"The Anticancer Effects of Vitamin K","volume":"8","author":"Lamson DW","year":"2003","journal-title":"Altern Med Rev"},{"key":"e_1_2_7_3_1","first-page":"284","article-title":"Vitamin K2. 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