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Automatic sampling and analysis of organics and biomolecules by capillary action-supported contactless atmospheric pressure ionization mass spectrometry.

Hsieh CH, Meher AK, Chen YC - PLoS ONE (2013)

Bottom Line: Furthermore, the well containing the rinsing solvent is alternately arranged between the sample wells.No carryover problems are observed during the analyses.The feasibility of using this setup for quantitative analysis is also demonstrated.

View Article: PubMed Central - PubMed

Affiliation: Department of Applied Chemistry, National Chiao Tung University, Hsinchu, Taiwan.

ABSTRACT
Contactless atmospheric pressure ionization (C-API) method has been recently developed for mass spectrometric analysis. A tapered capillary is used as both the sampling tube and spray emitter in C-API. No electric contact is required on the capillary tip during C-API mass spectrometric analysis. The simple design of the ionization method enables the automation of the C-API sampling system. In this study, we propose an automatic C-API sampling system consisting of a capillary (∼1 cm), an aluminium sample holder, and a movable XY stage for the mass spectrometric analysis of organics and biomolecules. The aluminium sample holder is controlled by the movable XY stage. The outlet of the C-API capillary is placed in front of the orifice of a mass spectrometer, whereas the sample well on the sample holder is moved underneath the capillary inlet. The sample droplet on the well can be readily infused into the C-API capillary through capillary action. When the sample solution reaches the capillary outlet, the sample spray is readily formed in the proximity of the mass spectrometer applied with a high electric field. The gas phase ions generated from the spray can be readily monitored by the mass spectrometer. We demonstrate that six samples can be analyzed in sequence within 3.5 min using this automatic C-API MS setup. Furthermore, the well containing the rinsing solvent is alternately arranged between the sample wells. Therefore, the C-API capillary could be readily flushed between runs. No carryover problems are observed during the analyses. The sample volume required for the C-API MS analysis is minimal, with less than 1 nL of the sample solution being sufficient for analysis. The feasibility of using this setup for quantitative analysis is also demonstrated.

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Related in: MedlinePlus

Flow rate examination.(A) The extracted ion chromatogram (EIC) at m/z 531, which corresponds to the doubly charged bradykinin ions, and (B) the corresponding mass spectrum obtained at the 0.2 min time point from panel A. The results were obtained using a capillary tapered to ∼7 µm (1 cm in length) as the C-API sampling tube and spray emitter. The capillary was filled with acetonitrile/deionized water (1∶1, v/v) prior to MS analysis. The C-API capillary was placed in front (∼1 mm) of a mass spectrometer and then immersed into a sample droplet containing 10 µM bradykinin prepared in acetonitrile/deionized water (1∶1, v/v). Upon immersion of the capillary into the sample droplet, the mass spectrometer was activated.
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pone-0066292-g002: Flow rate examination.(A) The extracted ion chromatogram (EIC) at m/z 531, which corresponds to the doubly charged bradykinin ions, and (B) the corresponding mass spectrum obtained at the 0.2 min time point from panel A. The results were obtained using a capillary tapered to ∼7 µm (1 cm in length) as the C-API sampling tube and spray emitter. The capillary was filled with acetonitrile/deionized water (1∶1, v/v) prior to MS analysis. The C-API capillary was placed in front (∼1 mm) of a mass spectrometer and then immersed into a sample droplet containing 10 µM bradykinin prepared in acetonitrile/deionized water (1∶1, v/v). Upon immersion of the capillary into the sample droplet, the mass spectrometer was activated.

Mentions: This study focused on the development of automatic sampling MS analysis using the C-API setup. Faster sampling speeds are helpful for high-throughput analysis. In principle, a thinner capillary tube would provide a faster sampling speed. Thus, a capillary (150 µm o.d., 10 µm i.d., 1 cm in length) was tapered and used as the sampling tube and the C-API spray emitter. Bradykinin (10 µM) in acetonitrile/deionized water (1∶1, v/v) was initially used as the model sample. The tapered capillary filled with acetonitrile/deionized water (1∶1, v/v) was placed in front of a mass spectrometer (Fig. 1). After a 4 µL sample droplet was deposited on the aluminium plate on a XY stage, the plate was moved up to immerse the capillary inlet into the small droplet (Fig. 1). Simultaneously, the mass spectrometer acquired the MS signal. The sampling speed was estimated based on the time of doubly charged bradykinin ion signal observed in the extracted ion chromatogram (EIC) at m/z 531. Figure 2A shows the EIC at m/z 531, whereas Figure 2B shows the mass spectrum obtained at the 0.2 min time point when the peak at m/z 531 just appeared. The flow rate was estimated to be ∼4 nL min−1, whereas the linear velocity was estimated to be ∼5 cm min−1. The results indicate that the thin capillary tube provided a fast sampling speed. However, capillary tips that were thinner than used herein were too fragile to be held with tweezers in the current design. Thus, the smallest capillary tube with an original i.d. of 10 µm was used as the C-API sampling tube and spray emitter in this study.


Automatic sampling and analysis of organics and biomolecules by capillary action-supported contactless atmospheric pressure ionization mass spectrometry.

Hsieh CH, Meher AK, Chen YC - PLoS ONE (2013)

Flow rate examination.(A) The extracted ion chromatogram (EIC) at m/z 531, which corresponds to the doubly charged bradykinin ions, and (B) the corresponding mass spectrum obtained at the 0.2 min time point from panel A. The results were obtained using a capillary tapered to ∼7 µm (1 cm in length) as the C-API sampling tube and spray emitter. The capillary was filled with acetonitrile/deionized water (1∶1, v/v) prior to MS analysis. The C-API capillary was placed in front (∼1 mm) of a mass spectrometer and then immersed into a sample droplet containing 10 µM bradykinin prepared in acetonitrile/deionized water (1∶1, v/v). Upon immersion of the capillary into the sample droplet, the mass spectrometer was activated.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3675195&req=5

pone-0066292-g002: Flow rate examination.(A) The extracted ion chromatogram (EIC) at m/z 531, which corresponds to the doubly charged bradykinin ions, and (B) the corresponding mass spectrum obtained at the 0.2 min time point from panel A. The results were obtained using a capillary tapered to ∼7 µm (1 cm in length) as the C-API sampling tube and spray emitter. The capillary was filled with acetonitrile/deionized water (1∶1, v/v) prior to MS analysis. The C-API capillary was placed in front (∼1 mm) of a mass spectrometer and then immersed into a sample droplet containing 10 µM bradykinin prepared in acetonitrile/deionized water (1∶1, v/v). Upon immersion of the capillary into the sample droplet, the mass spectrometer was activated.
Mentions: This study focused on the development of automatic sampling MS analysis using the C-API setup. Faster sampling speeds are helpful for high-throughput analysis. In principle, a thinner capillary tube would provide a faster sampling speed. Thus, a capillary (150 µm o.d., 10 µm i.d., 1 cm in length) was tapered and used as the sampling tube and the C-API spray emitter. Bradykinin (10 µM) in acetonitrile/deionized water (1∶1, v/v) was initially used as the model sample. The tapered capillary filled with acetonitrile/deionized water (1∶1, v/v) was placed in front of a mass spectrometer (Fig. 1). After a 4 µL sample droplet was deposited on the aluminium plate on a XY stage, the plate was moved up to immerse the capillary inlet into the small droplet (Fig. 1). Simultaneously, the mass spectrometer acquired the MS signal. The sampling speed was estimated based on the time of doubly charged bradykinin ion signal observed in the extracted ion chromatogram (EIC) at m/z 531. Figure 2A shows the EIC at m/z 531, whereas Figure 2B shows the mass spectrum obtained at the 0.2 min time point when the peak at m/z 531 just appeared. The flow rate was estimated to be ∼4 nL min−1, whereas the linear velocity was estimated to be ∼5 cm min−1. The results indicate that the thin capillary tube provided a fast sampling speed. However, capillary tips that were thinner than used herein were too fragile to be held with tweezers in the current design. Thus, the smallest capillary tube with an original i.d. of 10 µm was used as the C-API sampling tube and spray emitter in this study.

Bottom Line: Furthermore, the well containing the rinsing solvent is alternately arranged between the sample wells.No carryover problems are observed during the analyses.The feasibility of using this setup for quantitative analysis is also demonstrated.

View Article: PubMed Central - PubMed

Affiliation: Department of Applied Chemistry, National Chiao Tung University, Hsinchu, Taiwan.

ABSTRACT
Contactless atmospheric pressure ionization (C-API) method has been recently developed for mass spectrometric analysis. A tapered capillary is used as both the sampling tube and spray emitter in C-API. No electric contact is required on the capillary tip during C-API mass spectrometric analysis. The simple design of the ionization method enables the automation of the C-API sampling system. In this study, we propose an automatic C-API sampling system consisting of a capillary (∼1 cm), an aluminium sample holder, and a movable XY stage for the mass spectrometric analysis of organics and biomolecules. The aluminium sample holder is controlled by the movable XY stage. The outlet of the C-API capillary is placed in front of the orifice of a mass spectrometer, whereas the sample well on the sample holder is moved underneath the capillary inlet. The sample droplet on the well can be readily infused into the C-API capillary through capillary action. When the sample solution reaches the capillary outlet, the sample spray is readily formed in the proximity of the mass spectrometer applied with a high electric field. The gas phase ions generated from the spray can be readily monitored by the mass spectrometer. We demonstrate that six samples can be analyzed in sequence within 3.5 min using this automatic C-API MS setup. Furthermore, the well containing the rinsing solvent is alternately arranged between the sample wells. Therefore, the C-API capillary could be readily flushed between runs. No carryover problems are observed during the analyses. The sample volume required for the C-API MS analysis is minimal, with less than 1 nL of the sample solution being sufficient for analysis. The feasibility of using this setup for quantitative analysis is also demonstrated.

Show MeSH
Related in: MedlinePlus