Selenium speciation by HPLC with tandem mass spectrometric detection.

Area of Science:

• Analytical Chemistry
• Biochemistry
• Environmental Science

Background:

• Selenium species analysis is crucial for understanding biological and environmental processes.
• Lack of commercially available standards complicates the identification of novel selenium compounds.
• Tandem mass spectrometry (MS-MS) offers structural and molecular information for species identification.

Purpose of the Study:

• To develop and optimize a high-performance liquid chromatography coupled with tandem mass spectrometry (HPLC/MS-MS) method for selenium species analysis.
• To establish a novel separation technique for selenium species using porous graphitic carbon (PGC).
• To demonstrate the method's applicability in identifying and analyzing a mixture of selenium compounds.

Main Methods:

• Development of a new HPLC separation method utilizing porous graphitic carbon (PGC) as the stationary phase.
• Optimization of HPLC/MS-MS conditions, including ionization techniques (ESI vs. APCI) and ionization modes (positive vs. negative).
• Comparison of mass spectrometry instruments: triple quadrupole (Quattro LC) and time-of-flight (Q-Tof-2) for mass resolution and sensitivity.

Main Results:

• Baseline resolution of selenium species (Se-methyl-selenocysteine, selenomethionine, selenocystine, selenoethionine, selenocystamine) within 16 minutes.
• Positive ionization yielded higher signal intensities compared to negative ionization.
• Electrospray ionization (ESI) proved more effective than atmospheric pressure chemical ionization (APCI) in the tested matrices.
• Time-of-flight mass spectrometry offered 20-fold higher mass resolution (m/Δm=5000) than the triple quadrupole instrument.

Conclusions:

• The developed HPLC/MS-MS method with PGC is highly effective for separating and identifying diverse selenium species.
• The method enables the analysis of selenium compounds lacking commercial standards, providing characteristic MS-MS fragmentation patterns.
• The study highlights the advantages of PGC chromatography and time-of-flight mass spectrometry for sensitive and high-resolution selenium speciation analysis.