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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

Analysis of creatinine in urine samples.(A) Representative EIC of the ion at m/z 227 obtained from a series of diluted urine samples by acetonitrile/deionized water (1∶1, v/v). (B) Corresponding mass spectrum acquired from 1.3 min to 1.5 min in panel A. (C) Plot of the peak area at m/z 227 versus the volume ratio of urine to the acetonitrile/deionized water (1∶1, v/v) solvent. The results were obtained from three replicates using the same capillary as the sampling tube and C-API emitter.
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pone-0066292-g006: Analysis of creatinine in urine samples.(A) Representative EIC of the ion at m/z 227 obtained from a series of diluted urine samples by acetonitrile/deionized water (1∶1, v/v). (B) Corresponding mass spectrum acquired from 1.3 min to 1.5 min in panel A. (C) Plot of the peak area at m/z 227 versus the volume ratio of urine to the acetonitrile/deionized water (1∶1, v/v) solvent. The results were obtained from three replicates using the same capillary as the sampling tube and C-API emitter.

Mentions: Additionally, the possibility of using biological fluids such as urine as sample was examined to investigate the feasibility of using the C-API auto-sampling system in real-life applications. Creatinine is one of important urine metabolites. It was chosen as the target analyte in the study. Urine with different dilution factors such as 20−, 50−, 100−, and 300−fold were utilized as samples for analysis. The change in the intensity of the creatinine signal and the correlation of the analyte ion signal with the dilution factor were determined. Considering the ion peak of protonated creatinine at m/z 114 overlapped with an unknown background peak, the ion peak of the most abundant creatinine dimer ion at m/z 227 was alternatively chosen as the target peak. Figure 6A shows the representative EIC plot at m/z 227. The peak area at m/z 227 increased as the urine became less dilute. When the aluminium plate was moved to the well with rinse solvent, no creatinine ions were observed in the EIC plot after capillary flushing. No carryover problems were observed during the analysis of the complex biological samples. Figure 6B shows the corresponding mass spectrum acquired between 1.3 min and 1.5 min. The peak at m/z 227 is the base peak, whereas the protonated creatinine ion at m/z 114 and the creatinine sodium adduct ion at m/z 136 appeared in the same mass spectrum. Figure 6C shows the plot of the peak area at m/z 227 versus the volume ratio of the urine to the solvent [acetonitrile/deionized water (1∶1, v/v)]. Although the urine samples contained a complex matrix, the complex matrix in the urine did not affect the quantitative analysis much in different dilution factors. An acceptable linear regression curve was obtained based on using the creatinine dimer ion as the target analyte to construct a calibration curve versus different urine dilutions.


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)

Analysis of creatinine in urine samples.(A) Representative EIC of the ion at m/z 227 obtained from a series of diluted urine samples by acetonitrile/deionized water (1∶1, v/v). (B) Corresponding mass spectrum acquired from 1.3 min to 1.5 min in panel A. (C) Plot of the peak area at m/z 227 versus the volume ratio of urine to the acetonitrile/deionized water (1∶1, v/v) solvent. The results were obtained from three replicates using the same capillary as the sampling tube and C-API emitter.
© Copyright Policy
Related In: Results  -  Collection

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

pone-0066292-g006: Analysis of creatinine in urine samples.(A) Representative EIC of the ion at m/z 227 obtained from a series of diluted urine samples by acetonitrile/deionized water (1∶1, v/v). (B) Corresponding mass spectrum acquired from 1.3 min to 1.5 min in panel A. (C) Plot of the peak area at m/z 227 versus the volume ratio of urine to the acetonitrile/deionized water (1∶1, v/v) solvent. The results were obtained from three replicates using the same capillary as the sampling tube and C-API emitter.
Mentions: Additionally, the possibility of using biological fluids such as urine as sample was examined to investigate the feasibility of using the C-API auto-sampling system in real-life applications. Creatinine is one of important urine metabolites. It was chosen as the target analyte in the study. Urine with different dilution factors such as 20−, 50−, 100−, and 300−fold were utilized as samples for analysis. The change in the intensity of the creatinine signal and the correlation of the analyte ion signal with the dilution factor were determined. Considering the ion peak of protonated creatinine at m/z 114 overlapped with an unknown background peak, the ion peak of the most abundant creatinine dimer ion at m/z 227 was alternatively chosen as the target peak. Figure 6A shows the representative EIC plot at m/z 227. The peak area at m/z 227 increased as the urine became less dilute. When the aluminium plate was moved to the well with rinse solvent, no creatinine ions were observed in the EIC plot after capillary flushing. No carryover problems were observed during the analysis of the complex biological samples. Figure 6B shows the corresponding mass spectrum acquired between 1.3 min and 1.5 min. The peak at m/z 227 is the base peak, whereas the protonated creatinine ion at m/z 114 and the creatinine sodium adduct ion at m/z 136 appeared in the same mass spectrum. Figure 6C shows the plot of the peak area at m/z 227 versus the volume ratio of the urine to the solvent [acetonitrile/deionized water (1∶1, v/v)]. Although the urine samples contained a complex matrix, the complex matrix in the urine did not affect the quantitative analysis much in different dilution factors. An acceptable linear regression curve was obtained based on using the creatinine dimer ion as the target analyte to construct a calibration curve versus different urine dilutions.

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