Arsenic Binding to Thiols and Applications to Electrospray Mass Spectrometry Detection

• Author / Creator

  McKnight-Whitford, Anthony Nicholai

• Arsenic is a widespread environmental contaminant whose toxicity depends on its valence and its chemical form. Arsenic species have been typically determined using high pressure liquid chromatography coupled to inductively coupled plasma mass spectrometry (HPLC-ICPMS), however ICPMS cannot differentiate the co-eluting arsenic species. This thesis explores the use of electrospray mass spectrometry (ESI-MS) with HPLC separation for arsenic speciation and demonstrates applications of various HPLC-ESI-MS methods for the determination of toxicologically and environmentally relevant arsenic compounds.
  The trivalent arsenicals, such as arsenite (AsIII) and its metabolites monomethylarsonous acid (MMAIII) and dimethylarsinous acid (DMAIII) are not easily detected using ESI-MS due to their poor ionizability, but they are known to have high affinity for thiols. Thus, the easily ionizable dithiol dimercaptosuccinic acid (DMSA) was used to derivatize the trivalent arsenicals prior to ESI-MS. Selection of the derivatizing reaction was based on studies of arsenic-thiol interactions. An HPLC-ESI-MS/MS method was developed for the detection of derivatized AsIII, DMAIII and MMAIII and underivatized arsenate (AsV), monomethylarsonic acid (MMAV) and dimethylarsinic acid (DMAV), and was used to analyze multiple types of samples including urine, plasma and water. One set of groundwater samples from the site of a former pesticide manufacturing plant contained concentrations of MMAIII as high as 3.9-274 mg/L, the highest ever observed in the environment.
  
  Another HPLC-ESI-MS/MS method, without the need of derivatization, was developed for the detection of the toxic thio-arsenicals dimethylmonothioarsinic acid (DMMTAV) and monomethylmonothioarsonic acid (MMMTAV). DMMTAV was present in rat plasma and human urine and both DMMTAV and MMMTAV were detected in rat urine.
  
  The method of derivatization and ESI-MS/MS detection was extended to the speciation of inorganic SbIII and SbV. The use of the HPLC-ESI-MS/MS method using DMPS derivatization enabled the speciation of SbIII and SbV in water samples from mine waste.

• Subjects / Keywords

  • ESI-MS
  • Arsenic

• Graduation date

  Spring 2010

• Type of Item

  Thesis

• Degree

  Doctor of Philosophy

• DOI

  https://doi.org/10.7939/R3ZM61

• License

  This thesis is made available by the University of Alberta Libraries with permission of the copyright owner solely for non-commercial purposes. This thesis, or any portion thereof, may not otherwise be copied or reproduced without the written consent of the copyright owner, except to the extent permitted by Canadian copyright law.