Chapter 16
Searching for Internal Standard for Chemical
Routine Analysis of Lipophilic Shellfish Toxins
Trude S. Guldberg, T. Hatlen, and K. Aarstad
Introduction
Analytical methods based on liquid chromatography (LC) coupled to mass spectrometry (MS) have been used for several years to detect and quantify lipophilic
marine biotoxins in crude methanol shellfish extracts. Identification and quantification in routine analysis relies on retention time and peak area response compared to
certified standards. The analytical applications can be challenging as marine toxins
are complex analytes which are present in complex biological matrices. Response
drift and matrix effects (ion suppression or ion enhancement) in LC-MS analysis
can lead to an over or underestimation of the toxin concentration.
Various approaches can be used to overcome these potential errors, including
internal standards, standard addition, or by various clean-up techniques for removal
of interfering matrix components. To our knowledge, no internal standards are
available yet. Due to cost and limited availability of certified standards, the standard
addition approach is generally not feasible in routine analysis. Clean-up applications
by using solid phase extraction are rather time consuming and not necessarily
successful with regards to eliminating matrix effects (Gerssen et al. 2009b; These
et al. 2009). The lack of internal standards in LC-MS determinations makes the
analysis vulnerable to analytical and instrumental variations. Correct quantification
is dependent on accurate volumes during extraction and response stability during
instrumental analysis.
An adequate internal standard requires non-interference with the masses specified for the toxin of interest and should be able to mimic the behavior of a particular
analyte by being as similar as possible; ideally isotope labeled. Non-labeled internal
standards are often homologs which elute close to the analyte thus appearing in the
same vicinity with respect to any matrix effect.
T.S. Guldberg () • T. Hatlen • K. Aarstad
Department of Clinical Pharmacology, St. Olav’s University Hospital, Trondheim, Norway
e-mail: trude.guldberg@stolav.no; tone.hatlen@stolav.no; kjell.aarstad@live.no
G. Sauv´ e (ed.), Molluscan Shellfish Safety, DOI 10.1007/978-94-007-6588-7 16,
© Springer ScienceCBusiness Media Dordrecht 2014
187
Searching for Internal Standard for Chemical
Routine Analysis of Lipophilic Shellfish Toxins
Trude S. Guldberg, T. Hatlen, and K. Aarstad
Introduction
Analytical methods based on liquid chromatography (LC) coupled to mass spectrometry (MS) have been used for several years to detect and quantify lipophilic
marine biotoxins in crude methanol shellfish extracts. Identification and quantification in routine analysis relies on retention time and peak area response compared to
certified standards. The analytical applications can be challenging as marine toxins
are complex analytes which are present in complex biological matrices. Response
drift and matrix effects (ion suppression or ion enhancement) in LC-MS analysis
can lead to an over or underestimation of the toxin concentration.
Various approaches can be used to overcome these potential errors, including
internal standards, standard addition, or by various clean-up techniques for removal
of interfering matrix components. To our knowledge, no internal standards are
available yet. Due to cost and limited availability of certified standards, the standard
addition approach is generally not feasible in routine analysis. Clean-up applications
by using solid phase extraction are rather time consuming and not necessarily
successful with regards to eliminating matrix effects (Gerssen et al. 2009b; These
et al. 2009). The lack of internal standards in LC-MS determinations makes the
analysis vulnerable to analytical and instrumental variations. Correct quantification
is dependent on accurate volumes during extraction and response stability during
instrumental analysis.
An adequate internal standard requires non-interference with the masses specified for the toxin of interest and should be able to mimic the behavior of a particular
analyte by being as similar as possible; ideally isotope labeled. Non-labeled internal
standards are often homologs which elute close to the analyte thus appearing in the
same vicinity with respect to any matrix effect.
T.S. Guldberg () • T. Hatlen • K. Aarstad
Department of Clinical Pharmacology, St. Olav’s University Hospital, Trondheim, Norway
e-mail: trude.guldberg@stolav.no; tone.hatlen@stolav.no; kjell.aarstad@live.no
G. Sauv´ e (ed.), Molluscan Shellfish Safety, DOI 10.1007/978-94-007-6588-7 16,
© Springer ScienceCBusiness Media Dordrecht 2014
187