TY - JOUR
T1 - Detection of saccharides by reactive desorption electrospray ionization (DESI) using modified phenylboronic acids
AU - Zhang, Yun
AU - Chen, Hao
N1 - Funding Information:
Authors are very grateful for the insightful suggestions and comments from Prof. R. Graham Cooks at Purdue University and help from Caroline Krieger, Drs. Dina R. Justes and Feng Feng. This work was supported by Ohio University (SU1006172) and NSF (CHE-0911160).
PY - 2010/1/15
Y1 - 2010/1/15
N2 - We have reported previously a method for the detection of sugars via in-situ derivatization with phenylboronic acid PhB(OH)2 using reactive desorption electrospray ionization (DESI, Chen et al., Chem. Commun. (2006) 597-599). The present study describes an improved method that employs modified phenylboronic acids including 3-nitrophenylboronic acid and N-methyl-4-pyridineboronic acid iodide. In contrast to using PhB(OH)2, enhanced sensitivity of using 3-nitrophenylboronic acid was observed due to the stabilization of the resulting boronate ester anion by the electron-withdrawing nitro group and the limit of detections (LODs) for glucose in water using 3-nitrophenylbornic acid and phenylboronic acid were determined to be 0.11 mM and 0.40 mM, respectively. In the case of N-methyl-4-pyridineboronic acid iodide, the corresponding LOD is 6.9 μM and the higher sensitivity obtained is attributed to the efficient ionization of both the reactive DESI reagent and reaction product since the precursor acid with a quaternary ammonium group is pre-charged. In this case, additional important features are found: (i) unlike using phenylboronic acid or 3-nitrophenylbornic acid, the experiment, performed in the positive ion mode, is applicable to neutral and acidic saccharide solutions, facilitating the analysis of biological fluids without the need to adjust pH; (ii) simply by changing the spray solvent from water to acetonitrile, the method can be used for direct glucose analyses of both urine and serum samples via online desalting, due to the low solubility of salts of these biofluids in the sprayed organic solvent; (iii) in comparison with other sugar derivatizing reagents such as the Girard's reagent T, the N-methyl-4-pyridineboronic acid iodide shows higher reactivity in the reactive DESI; and (iv) the ions of saccharide DESI reaction products undergo extensive ring or glycosidic bond cleavage upon CID, a feature that might be useful in the structure elucidation of saccharides. In addition, a variant sample introduction protocol using pipette tips for saccharide solutions was also demonstrated in the reactive DESI experiments, allowing the analysis of multiple samples of a small volume (e.g., 200 nL) in a short period of time (e.g., five samples in 4 min). The method reported in this study with improved sensitivity and high selectivity along with online desalting and high throughput capability could find useful applications in saccharide analysis in complicated biological samples.
AB - We have reported previously a method for the detection of sugars via in-situ derivatization with phenylboronic acid PhB(OH)2 using reactive desorption electrospray ionization (DESI, Chen et al., Chem. Commun. (2006) 597-599). The present study describes an improved method that employs modified phenylboronic acids including 3-nitrophenylboronic acid and N-methyl-4-pyridineboronic acid iodide. In contrast to using PhB(OH)2, enhanced sensitivity of using 3-nitrophenylboronic acid was observed due to the stabilization of the resulting boronate ester anion by the electron-withdrawing nitro group and the limit of detections (LODs) for glucose in water using 3-nitrophenylbornic acid and phenylboronic acid were determined to be 0.11 mM and 0.40 mM, respectively. In the case of N-methyl-4-pyridineboronic acid iodide, the corresponding LOD is 6.9 μM and the higher sensitivity obtained is attributed to the efficient ionization of both the reactive DESI reagent and reaction product since the precursor acid with a quaternary ammonium group is pre-charged. In this case, additional important features are found: (i) unlike using phenylboronic acid or 3-nitrophenylbornic acid, the experiment, performed in the positive ion mode, is applicable to neutral and acidic saccharide solutions, facilitating the analysis of biological fluids without the need to adjust pH; (ii) simply by changing the spray solvent from water to acetonitrile, the method can be used for direct glucose analyses of both urine and serum samples via online desalting, due to the low solubility of salts of these biofluids in the sprayed organic solvent; (iii) in comparison with other sugar derivatizing reagents such as the Girard's reagent T, the N-methyl-4-pyridineboronic acid iodide shows higher reactivity in the reactive DESI; and (iv) the ions of saccharide DESI reaction products undergo extensive ring or glycosidic bond cleavage upon CID, a feature that might be useful in the structure elucidation of saccharides. In addition, a variant sample introduction protocol using pipette tips for saccharide solutions was also demonstrated in the reactive DESI experiments, allowing the analysis of multiple samples of a small volume (e.g., 200 nL) in a short period of time (e.g., five samples in 4 min). The method reported in this study with improved sensitivity and high selectivity along with online desalting and high throughput capability could find useful applications in saccharide analysis in complicated biological samples.
KW - Desorption electrospray ionization
KW - Ion/molecule reaction
KW - Mass spectrometry
KW - Online desalting
KW - Saccharide detection
UR - http://www.scopus.com/inward/record.url?scp=72249092537&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=72249092537&partnerID=8YFLogxK
U2 - 10.1016/j.ijms.2009.09.015
DO - 10.1016/j.ijms.2009.09.015
M3 - Article
AN - SCOPUS:72249092537
SN - 1387-3806
VL - 289
SP - 98
EP - 107
JO - International Journal of Mass Spectrometry
JF - International Journal of Mass Spectrometry
IS - 2-3
ER -