Hyphenation of capillary high‐performance ion‐exchange chromatography with mass spectrometry using sheath‐flow electrospray ionization

Abstract

RATIONALE: Mass spectrometry (MS) is an attractive method for extending capillary-size ion chromatography (cHPIC) to create a valuable technique for speciation analysis. For hyphenation, the aqueous effluent of cHPIC has to be transformed into a volatile mixture for MS while preserving analytical concentrations as well as peak shapes during transfer from cHPIC to MS. Finally, the approach should technically be flexible and easy-to-use. A combination of cHPIC and sheath-flow electrospray ionization (ESI)-MS offers to solve all these challenges. METHODS: cHPIC/sheath-flow-ESI-TOFMS was used in this study for the speciation analysis of various arsenic model compounds. These model compounds were analyzed with different hyphenation setups and configurations of cHPIC/MS and their respective assets and drawbacks were examined and discussed. The parameters (flow rate and composition of sheath liquid) of sheath-flow ESI and their influence on the performance of the spray and the sensitivity of the detector were investigated and compared with those of sheathless ESI. RESULTS: Using an injection valve to couple cHPIC and MS was found to be the best method for hyphenation, since it constitutes a flexible and dead-volume-free approach. The investigation of sheath-flow ESI revealed that the flow rate of the sheath liquid has to resemble the flow rate of the IC effluent to ensure a stable spray and that a composition of 2-propanol/water/ammonia at 50:50:0.2 (v/v/v) suits most applications without unilaterally promoting the sensitivity for either organic or inorganic compounds. The optimized setup and conditions were successfully applied to the analysis of a mixture of important arsenic species and used to determine limits of detection of organic and inorganic arsenic species (3.7 μg L À1 elemental arsenic). CONCLUSIONS: A method for cHPIC/sheath-flow-ESI-MS was developed. The method was shown to be a valuable tool for speciation and trace analysis. It features no dead volume, fast transfer from IC to MS, only minimal peak-widening, high reproducibility, and the ability to fine-tune the ESI spray for higher sensitivity and stability by adjusting the composition of the sheath-liquid.

Targeted and non-targeted forensic profiling of black powder substitutes and gunshot residue using gradient ion chromatography – high resolution mass spectrometry (IC-HRMS)

“…Secondly, their compatibility with traditional organic solvents used for sample extraction is limited, since most sampling protocols involve the use of organic solvents to ensure recovery of both the inorganic and organic compounds. Usually, these two problems are addressed by infusing organic solvents in the eluate using an auxiliary pump prior to ESI and solvent exchange with water before injection [26,27]. The full procedure is nonetheless lengthy and complicated, and often results in sub-optimal sensitivity.…”

Advanced analytical methods and sample preparation for ion chromatography techniques

“…129 Applying a 0.32 Â 100 mm column packed with 3 mm octadecyl silica (ODS) microparticles coated with hexadecyltrimethylammonium bromide and mixed eluent containing 1 mM sodium salicylate with 5% acetonitrile, Takeuchi's group developed another CIC method for inorganic anions. [135][136][137][138][139] Using an injection valve to couple CIC and MS was found to be the best method for hyphenation, since it constituted a exible and dead-volume-free approach. The BSA molecule, immobilized on 5 mm ODS particles, was protonated at specic pH condition and affected the anionic analyte retention.…”

“…130 Stationary phases coated with immobilized biological macromolecules, such as bovine serum albumin (BSA), has been introduced to the CIC technique innovation. 139 Fluorescence detection can be easily hyphenated with CIC as well. Using 0.35 Â 75-150 mm columns and an eluent containing NaI and tartaric acid, this method was successfully applied for indirect photometric detection of nitrite and bromide in tap water.…”

“…134 MS is an attractive method for extending capillary IC to create a valuable technique for speciation and trace analysis. [135][136][137][138][139] Using an injection valve to couple CIC and MS was found to be the best method for hyphenation, since it constituted a exible and dead-volume-free approach. Matysik's group developed a CIC/sheath-ow-ESI-MS method, which featured no dead volume, fast transfer from IC to MS, only minimal peakwidening, high reproducibility, and the ability to ne-tune the ESI spray for higher sensitivity and stability by adjusting the composition of the sheath-liquid.…”

“…Matysik's group developed a CIC/sheath-ow-ESI-MS method, which featured no dead volume, fast transfer from IC to MS, only minimal peakwidening, high reproducibility, and the ability to ne-tune the ESI spray for higher sensitivity and stability by adjusting the composition of the sheath-liquid. 139 Fluorescence detection can be easily hyphenated with CIC as well. Aluminum and magnesium were determined by uorimetric detection via pre-column and/or in-column derivatization with 8-hydroxyquinoline (oxine) in the microcolumn format (0.32 Â 100 mm, ODS packing).…”