Ethylenediaminetetraacetic acid (EDTA) as an auxiliary tool in the electrospray ionization mass spectrometry analysis of native and derivatized B-cyclodextrins, maltoses and fructans contaminated with Ca and/or Mg

M. KANIZ FATEMA; SILVANA L. GIUDICESSI; ROSA ERRA-BALSELLS; HIROSHI NONAMI

Tsukuba, Japón

Congreso; 58th Annual Conference on Mass Spectrometry; 2010

Mass Spectrometry Society of Japan (MSSJ)

Herein we studied the effect of Ca (and Mg) and the disodium salt of ethylenediaminetetraacetic acid (EDTA), the well known chelating Ca (and Mg) reagent, on the volatilization/ionization of carbohydrates by using electrospray ionization mass spectrometry. As model compounds maltoses (maltose to maltoheptaose, M(1)-M(7)), β-cyclodextrins (β-cyclodextrin (Bcd), methyl-β-cyclodextrin (MBcd), heptakis(2,6-di-Omethyl)-β-cyclodextrin (DMBcd), heptakis(2,3,6-tri-O-methyl)-β-cyclodextrin (TMBcd) and 2-hydroxypropil-β-cyclodextrin (OHPBcd)) and fructans (sucrose (F(3)), 1-ketose, nystose (F(4)) and 1F-fructofuranosylnystose (F(5)) were used. The behavior of carbohydrates in the presence of Ca (and Mg) is not uniform, it depends if they are linear or cyclic; additionally for the former also depends on the length of the chain and its structure (maltoses; fructans), and for the latter on the degree and nature of the substitution. The addition of EDTA to the solution quenches the Ca effect on the carbohydrate ESI because of its chelating property. Additionally, as it does not affect the carbohydrate as itself the intensity of the signals [M+Na]+ and [M+2Na]2+are restored. The presence of Ca must be taking into account for qualitative and quantitative ESI-MS analysis of native extracted carbohydrates and carbohydrates in general. EDTA shown to be a quite convenient auxiliary reagent to take into account at the moment of conducting ESI-MS analysis of carbohydrates. The species [M+2Na]2+ is detected with similar or higher intensity than the ion [M+Na]+ in the ESI-MS analysis of M(7) and Bcd and similar results were obtained when substituted Bcd were studied. As the m/z region of [M+2Na]2+, [M+Ca]2+ and [M+Mg] 2+ signals overlaps, Ca and Mg adducts because the presence of these cations in the sample might add satellite signals and distortion to the natural [M+2Na]2+ patter, when a mixture of carbohydrate oligomers is analyzed as it is shown for Bcd derivatives DMBcd, MBcd and OHPBcd. To make the matter worst, these Bcd derivatives also showed satellite signals with the structure [M?H+Ca]+ and [M?H+Mg]+ in the [M+Na]+ and [M+K]+ m/z region (figure 1). The conducted experiments also showed that among the carbohydrates studied those with β-cyclodextrin-like structure are more sensitivity to the presence of Ca than low molecular weight maltoses (M(3)-M(6)). Thus, at β-cyclodextrin:CaCl2 molar ratio 100:1, the [M+Ca]2+ species was detected as a quite stable gas-ion species together with the species [M+Na]+ y [M+2Na]2+. Comparing maltoses and fructans with the same molecular weight, the former yielded [M+Ca]2+ signals more efficiently (or more stable as gas-ion). As a conclusion the behavior of carbohydrates in the presence of Ca (and Mg) is not uniform, it depends on the length of the carbohydrate chain and its structure. In the case of fructans, although the presence of Ca diminish the intensity of the [M+Na]+ signal, as the [M+Ca]2+ signal is not detected till fructan:CaCl2 molar ratio lower than 1:1, this fact can induce serious mistakes when quantification of these carbohydrates is attempted. The addition of EDTA to the solution quenches the Ca effect on the carbohydrate ESI because of its chelating property, it does not affect the carbohydrate as itself and the signals [M+Na]+ and [M+2Na]2+ are restored. As summary, the presence of Ca and Mg must be taking into account for qualitative and quantitative ESI-MS analysis of native extracted carbohydrates and carbohydrates in general. In this context EDTA is a quite convenient auxiliary reagent to take into account at the moment of conducting ESI- MS analysis of carbohydrates.