Quantitative Capillary Electrophoresis-Ion Spray Mass Spectrometry on a Benchtop Ion Trap for the Determination of Isoquinoline Alkaloids

Abstract

The quantitative determination of some isoquinoline alkaloid natural products is described using combined capillary electrophoresis-ion trap mass spectrometry (CE/MS). The benchtop ion trap is a previously described modified commercial Varian Saturn II system equipped with an in-house constructed atmospheric pressure ionzation (API) ion source which was operated in the ion spray CE/MS mode. All relevant operational parameters have been optimized for the CE/MS experiments described in this work. A coaxial sheath flow of solvent buffer was used to facilitate ion spray CE/MS operation. Analysis of synthetic mixtures containing nine related isoquinoline alkaloids provided full-scan mass spectra for these compounds with injected quantities as low as 370 attomole. The signal-to-noise ratio was better than 10/1 for theextracted ion current electropherograms of the parent ions for these compounds with injected quantities in the 370-510 attomole range. CE/MS analysis of methanol extracts from the natural bark of Pbellodendron wilsonii&s well as an herbal medication provided full-scan mass spectra for the identification of major and minor components in the mixture. Quantitative analyses were carried out using tetrahydroberberine as an internal standard. The standard curve ranged from injected levels of 0.6 to 16 pg (1.7 to 45 fmol) and had correlation coefficients of 0.998 and 0.999 for berberine and palmatine, respectively. These results suggest that the ion trap CE/MS system is sufficiently sensitive and reliable to provide acceptable quantitative analysis of synthetic and natural product mixtures.High-performance capillary electrophoresis (HPCE) is recognized as a powerful technique for the separation and analysis of samples composed of charged species which range from small ions to large proteins.1-3 The coupling of capillary electrophoresis with mass spectrometry (CE/MS) offers added capability by providing important information necessary for the identification and confirmation of components in complex mixtures. On-line CE/MS was first reported by Smith et al.4 and later by Lee et al.5 where capillary electrophoresis was coupled to a quadrupole mass spectrometer using an atmospheric pressure ionization electrospray and an ion spray interface, respectively. Since then, other types of mass

Analysis and validation of the phosphorylated metabolites of two anti‐human immunodeficiency virus nucleotides (stavudine and didanosine) by pressure‐assisted CE‐ESI‐MS/MS in cell extracts: Sensitivity enhancement by the use of perfluorinated acids and alcohols as coaxial sheath‐liquid make‐up constituents

“…As can be clearly seen in Fig. 6, acids with short chain acids (TFA, PFPA) induced a significant ion suppression likely due to the formation of ion-pairing between TFA and basic moiety of nucleotides [39]. The best sensitivity for all perfluorinated acids was obtained with TDFHA.…”

Optimization of CZE for analysis of phytochemical bioactive compounds

“…As the CE flow is not high enough to maintain stable ionization within the MS source, an extra flow of liquid must be added to the CE eluant to obtain gas phase ions of the solutes. It has been found that sheath liquid composition and sheath liquid flow rate had significant influence on MS response [181,183,184]. Buffer is a key for successful coupling CZE and MS.…”

Analysis of drugs, natural and bioactive compounds containing phenolic groups by capillary electrophoresis coupled to mass spectrometry

“…Nevertheless, all applications are listed in Table 1. The quantitative determination of some isoquinoline alkaloid natural products using CE-ion trap-MS was described by Henion et al [60]. Using an in-house constructed ion source (Fig.…”

“…Quantitative analysis was carried out using tetrahydroberberine as an internal standard. The standard curve ranged from injected levels of 0.6 to 16 pg (1.7 to 45 fmol) and had correlation coefficients of 0.998 [60] Isoquinoline alkaloids CZE Ion trap Sheath [61] Basic drugs in cough syrup CZE Quadrupole Sheath [62] Drugs and metabolites CZE Quadrupole Sheath [66] Methoxycatecholamines CZE Ion trap Sheath [67] Pharmaceutical drugs NACE Quadrupole Sheath [68] Methamphetamines CZE Quadrupole Sheath [69] Ibuprofen, codeine PF-MEKC Quadrupole Sheath [70] Flavonoids CZE Quadrupole Sheath [71] Polycarbonic acids CZE Quadrupole Sheath [72] Methoxy phenols CZE Quadrupole Sheath [73] Alkaloids CZE Ion trap Sheath [74] Anesthetics CZE Quadrupole Sheath [75] Phenolic compounds CZE Quadrupole Sheath [76] Morphine derivatives CZE Ion trap Sheath [77] Dichlorophenols CZE Quadrupole Sheath [78] Venlafaxine metabolites NACE Quadrupole Sheath [79] Glycoalkaloids NACE Ion trap Sheath [80] Drug residues in water CZE Quadrupole Sheath [81] Drug residues in water CZE Quadrupole Sheath [82] Codeine CZE Ion trap Sheath [83] Morphine CZE Ion trap Sheath [84] Dyes CZE Quadrupole Sheath [85] Tramadol CZE Quadrupole Sheath [86] Amphetamines, designer drugs CZE Quadrupole Sheath [87] Nitrocatechol-type glucuronides CZE Quadrupole Sheath [88] Chlorophenols CZE Ion trap Sheath [89] Amphetamine derivatives CZE Quadrupole Sheath [90] Coptisine, berberine, palmitine CZE Ion trap Sheath [91] Phenolic compounds CZE Quadrupole Sheath [92] Paracetamol CZE Ion trap Sheath [93] Ecstacy and derivatives CZE Quadrupole Sheath [94] Phenoxy acid herbicides CZE Ion trap Sheath [95] Terbutaline, ketamine CZE Quadrupole Sheath …”