Protocol Received: 27 June 2014
Revised: 8 August 2014
Accepted: 15 September 2014
Published online in Wiley Online Library
Rapid Commun. Mass Spectrom. 2014, 28, 2670–2680 (wileyonlinelibrary.com) DOI: 10.1002/rcm.7056
Hyphenation of capillary high-performance ion-exchange chromatography with mass spectrometry using sheath-flow electrospray ionization Sven Kochmann and Frank-Michael Matysik* Institute of Analytical Chemistry, University of Regensburg, Universitätsstr. 31, D-93053 Regensburg, Germany 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 1 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. Copyright © 2014 John Wiley & Sons, Ltd.
Ion-exchange chromatography (IC) is a well-established analytical technique exploiting the diverse ion-exchange affinities of different analytes for their separation.[1] Today IC is utilized in a wide range of applications such as the analysis of wine,[2] aerosols,[3] low-explosive residues,[4] and arsenic compounds.[5] Most modern IC instruments work on an analytical scale (i.e. microbore columns with 1–4 mm ID),[6] and are operated at high pressure.[7] In conformity with high-pressure/ performance liquid chromatography (HPLC), this technique is labeled high-pressure/performance ion chromatography (HPIC). Although the first capillary-scale (i.e. columns with
Revised: 8 August 2014
Accepted: 15 September 2014
Published online in Wiley Online Library
Rapid Commun. Mass Spectrom. 2014, 28, 2670–2680 (wileyonlinelibrary.com) DOI: 10.1002/rcm.7056
Hyphenation of capillary high-performance ion-exchange chromatography with mass spectrometry using sheath-flow electrospray ionization Sven Kochmann and Frank-Michael Matysik* Institute of Analytical Chemistry, University of Regensburg, Universitätsstr. 31, D-93053 Regensburg, Germany 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 1 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. Copyright © 2014 John Wiley & Sons, Ltd.
Ion-exchange chromatography (IC) is a well-established analytical technique exploiting the diverse ion-exchange affinities of different analytes for their separation.[1] Today IC is utilized in a wide range of applications such as the analysis of wine,[2] aerosols,[3] low-explosive residues,[4] and arsenic compounds.[5] Most modern IC instruments work on an analytical scale (i.e. microbore columns with 1–4 mm ID),[6] and are operated at high pressure.[7] In conformity with high-pressure/ performance liquid chromatography (HPLC), this technique is labeled high-pressure/performance ion chromatography (HPIC). Although the first capillary-scale (i.e. columns with
