Arsenic containing medium and long chain fatty acids in marine fish oil identified as degradation products using reversed-phase HPLC-ICP-MS/ESI-MS

Éderson R. Pereira, Johannes F. Kopp, Andrea Raab, Eva M. Krupp, Javier Del Campo Menoyo, Eduardo Carasek, Bernhard Welz, Jörg Feldmann*

*Corresponding author for this work

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Abstract

This study describes the identification and quantification of five new arsenolipids present in raw marine fish oil extracted mainly from Peruvian anchoveta (Engraulis ringens). The arsenolipids accumulated on bentonite, which has been used to clean-up raw fish oils in an industrial process for producing commercial fish oil rich in omega-3 fatty acids. The bentonite, which adsorbed the arsenolipids efficiently from the raw fish oil was extracted with different solvents and subsequently cleaned up by normal phase chromatography, which fractionated all absorbed compounds according to polarity. The arsenic containing fatty acids (AsFA) and arsenic containing hydrocarbons (AsHC) were determined using a separation by reverse phase high performance liquid chromatography coupled online to inductively coupled plasma mass spectrometry (RP-HPLC-ICP-MS) for quantification and simultaneously to electrospray ionization mass spectrometry (ESI-MS) for identification. A mixture of methanol/chloroform (1 : 2 v/v) was sufficient for the extraction of the majority of the adsorbed arsenic species (129 μg g-1 As bentonite). The pre-concentration using the adsorbent with subsequent fractionation made it possible to identify minor arsenolipids especially in the polar methanol fraction. Besides two major arsenic containing hydrocarbons (AsHC332 and AsHC360) three new arsenic containing medium chain fatty acids (As-MCFA) of molecular mass 250, 278, 292 and two new arsenic containing long chain fatty acids (As-LCFA) of mass 306 and 320 could be identified although their concentrations were as low as 0.004 μg g-1 As bentonite. The significance of MCFA is that these compounds usually occur not as free fatty acids but are conjugated to glycerol forming triglycerides. Confirmation of this hypothesis is given in the fact that a methanol extract which was directly analyzed without any clean up procedure did only contain traces of As-LCFA and no As-MCFA but the same concentration of the more inert AsHCs, which are not expected to be conjugated to other organic compounds. This highlights that a successful pre-concentration and clean up procedure is essential to determine traces of minor arsenolipids but it does not provide a guarantee for the integrity of all arsenolipid species.

Original languageEnglish
Pages (from-to)1836-1845
Number of pages10
JournalJournal of Analytical Atomic Spectrometry
Volume31
Issue number9
Early online date29 Jun 2016
DOIs
Publication statusPublished - 1 Sep 2016

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Electrospray ionization
Fish Oils
Arsenic
Mass spectrometry
Fatty Acids
Bentonite
Degradation
Methanol
Hydrocarbons
Inductively coupled plasma mass spectrometry
Omega-3 Fatty Acids
High performance liquid chromatography
Molecular mass
Inductively coupled plasma
Fractionation
Chloroform
Chromatography
Organic compounds
Nonesterified Fatty Acids
Glycerol

ASJC Scopus subject areas

  • Analytical Chemistry
  • Spectroscopy

Cite this

Arsenic containing medium and long chain fatty acids in marine fish oil identified as degradation products using reversed-phase HPLC-ICP-MS/ESI-MS. / Pereira, Éderson R.; Kopp, Johannes F.; Raab, Andrea; Krupp, Eva M.; Menoyo, Javier Del Campo; Carasek, Eduardo; Welz, Bernhard; Feldmann, Jörg.

In: Journal of Analytical Atomic Spectrometry, Vol. 31, No. 9, 01.09.2016, p. 1836-1845.

Research output: Contribution to journalArticle

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title = "Arsenic containing medium and long chain fatty acids in marine fish oil identified as degradation products using reversed-phase HPLC-ICP-MS/ESI-MS",
abstract = "This study describes the identification and quantification of five new arsenolipids present in raw marine fish oil extracted mainly from Peruvian anchoveta (Engraulis ringens). The arsenolipids accumulated on bentonite, which has been used to clean-up raw fish oils in an industrial process for producing commercial fish oil rich in omega-3 fatty acids. The bentonite, which adsorbed the arsenolipids efficiently from the raw fish oil was extracted with different solvents and subsequently cleaned up by normal phase chromatography, which fractionated all absorbed compounds according to polarity. The arsenic containing fatty acids (AsFA) and arsenic containing hydrocarbons (AsHC) were determined using a separation by reverse phase high performance liquid chromatography coupled online to inductively coupled plasma mass spectrometry (RP-HPLC-ICP-MS) for quantification and simultaneously to electrospray ionization mass spectrometry (ESI-MS) for identification. A mixture of methanol/chloroform (1 : 2 v/v) was sufficient for the extraction of the majority of the adsorbed arsenic species (129 μg g-1 As bentonite). The pre-concentration using the adsorbent with subsequent fractionation made it possible to identify minor arsenolipids especially in the polar methanol fraction. Besides two major arsenic containing hydrocarbons (AsHC332 and AsHC360) three new arsenic containing medium chain fatty acids (As-MCFA) of molecular mass 250, 278, 292 and two new arsenic containing long chain fatty acids (As-LCFA) of mass 306 and 320 could be identified although their concentrations were as low as 0.004 μg g-1 As bentonite. The significance of MCFA is that these compounds usually occur not as free fatty acids but are conjugated to glycerol forming triglycerides. Confirmation of this hypothesis is given in the fact that a methanol extract which was directly analyzed without any clean up procedure did only contain traces of As-LCFA and no As-MCFA but the same concentration of the more inert AsHCs, which are not expected to be conjugated to other organic compounds. This highlights that a successful pre-concentration and clean up procedure is essential to determine traces of minor arsenolipids but it does not provide a guarantee for the integrity of all arsenolipid species.",
author = "Pereira, {{\'E}derson R.} and Kopp, {Johannes F.} and Andrea Raab and Krupp, {Eva M.} and Menoyo, {Javier Del Campo} and Eduardo Carasek and Bernhard Welz and J{\"o}rg Feldmann",
note = "Acknowledgements The authors are grateful to Conselho Nacional de Desenvolvimento Cient{\'i}fico e Tecnol{\'o}gico (CNPq), and Coordena{\cc}{\~a}o de Aperfei{\cc}oamento de Pessoal de N{\'i}vel Superior (CAPES) for financial support and scholarships. The present research was mostly financed through Project no. CNPq 406877/2013-0. Our thanks to Golden omega that provided suitable bentonite samples and to University of Aberdeen for total support and collaboration. Open access via RSC Gold4Gold.",
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T1 - Arsenic containing medium and long chain fatty acids in marine fish oil identified as degradation products using reversed-phase HPLC-ICP-MS/ESI-MS

AU - Pereira, Éderson R.

AU - Kopp, Johannes F.

AU - Raab, Andrea

AU - Krupp, Eva M.

AU - Menoyo, Javier Del Campo

AU - Carasek, Eduardo

AU - Welz, Bernhard

AU - Feldmann, Jörg

N1 - Acknowledgements The authors are grateful to Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq), and Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) for financial support and scholarships. The present research was mostly financed through Project no. CNPq 406877/2013-0. Our thanks to Golden omega that provided suitable bentonite samples and to University of Aberdeen for total support and collaboration. Open access via RSC Gold4Gold.

PY - 2016/9/1

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N2 - This study describes the identification and quantification of five new arsenolipids present in raw marine fish oil extracted mainly from Peruvian anchoveta (Engraulis ringens). The arsenolipids accumulated on bentonite, which has been used to clean-up raw fish oils in an industrial process for producing commercial fish oil rich in omega-3 fatty acids. The bentonite, which adsorbed the arsenolipids efficiently from the raw fish oil was extracted with different solvents and subsequently cleaned up by normal phase chromatography, which fractionated all absorbed compounds according to polarity. The arsenic containing fatty acids (AsFA) and arsenic containing hydrocarbons (AsHC) were determined using a separation by reverse phase high performance liquid chromatography coupled online to inductively coupled plasma mass spectrometry (RP-HPLC-ICP-MS) for quantification and simultaneously to electrospray ionization mass spectrometry (ESI-MS) for identification. A mixture of methanol/chloroform (1 : 2 v/v) was sufficient for the extraction of the majority of the adsorbed arsenic species (129 μg g-1 As bentonite). The pre-concentration using the adsorbent with subsequent fractionation made it possible to identify minor arsenolipids especially in the polar methanol fraction. Besides two major arsenic containing hydrocarbons (AsHC332 and AsHC360) three new arsenic containing medium chain fatty acids (As-MCFA) of molecular mass 250, 278, 292 and two new arsenic containing long chain fatty acids (As-LCFA) of mass 306 and 320 could be identified although their concentrations were as low as 0.004 μg g-1 As bentonite. The significance of MCFA is that these compounds usually occur not as free fatty acids but are conjugated to glycerol forming triglycerides. Confirmation of this hypothesis is given in the fact that a methanol extract which was directly analyzed without any clean up procedure did only contain traces of As-LCFA and no As-MCFA but the same concentration of the more inert AsHCs, which are not expected to be conjugated to other organic compounds. This highlights that a successful pre-concentration and clean up procedure is essential to determine traces of minor arsenolipids but it does not provide a guarantee for the integrity of all arsenolipid species.

AB - This study describes the identification and quantification of five new arsenolipids present in raw marine fish oil extracted mainly from Peruvian anchoveta (Engraulis ringens). The arsenolipids accumulated on bentonite, which has been used to clean-up raw fish oils in an industrial process for producing commercial fish oil rich in omega-3 fatty acids. The bentonite, which adsorbed the arsenolipids efficiently from the raw fish oil was extracted with different solvents and subsequently cleaned up by normal phase chromatography, which fractionated all absorbed compounds according to polarity. The arsenic containing fatty acids (AsFA) and arsenic containing hydrocarbons (AsHC) were determined using a separation by reverse phase high performance liquid chromatography coupled online to inductively coupled plasma mass spectrometry (RP-HPLC-ICP-MS) for quantification and simultaneously to electrospray ionization mass spectrometry (ESI-MS) for identification. A mixture of methanol/chloroform (1 : 2 v/v) was sufficient for the extraction of the majority of the adsorbed arsenic species (129 μg g-1 As bentonite). The pre-concentration using the adsorbent with subsequent fractionation made it possible to identify minor arsenolipids especially in the polar methanol fraction. Besides two major arsenic containing hydrocarbons (AsHC332 and AsHC360) three new arsenic containing medium chain fatty acids (As-MCFA) of molecular mass 250, 278, 292 and two new arsenic containing long chain fatty acids (As-LCFA) of mass 306 and 320 could be identified although their concentrations were as low as 0.004 μg g-1 As bentonite. The significance of MCFA is that these compounds usually occur not as free fatty acids but are conjugated to glycerol forming triglycerides. Confirmation of this hypothesis is given in the fact that a methanol extract which was directly analyzed without any clean up procedure did only contain traces of As-LCFA and no As-MCFA but the same concentration of the more inert AsHCs, which are not expected to be conjugated to other organic compounds. This highlights that a successful pre-concentration and clean up procedure is essential to determine traces of minor arsenolipids but it does not provide a guarantee for the integrity of all arsenolipid species.

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