Positive ionization mode

Compounds were optimized in positive ionization mode and in negative mode if necessary. Automaton can also perform automatic MS method development from solutions containing multiple compounds to increase throughput. When mixture solutions are used, Automaton injects a mixture once to determine all precursor ions and DP values and then injects once per compound to determine product ion and CE value. This approach allows automatic and unattended optimization of MS parameters for hundreds of compounds. The optimized parameters are stored in a compound database that permits fast and efficient retrieval of information about a specific compound and allows a compound to be used in multiple assays, eliminating the need to re-optimize the LC/MS/MS conditions. 

A Waters Micromass triple quadrupole mass spectrometer was used with an electrospray ionization interface in positive ionization mode desolvation gas (400), cone gas (70), collision gas (2.74 x 10 3 mbar), capillary (3.0 kV), cone (14 (kV), source temperature (105°C), and desolvation temperature (300°C). The detection and quantitation of amlodipine and nimodipine were performed... 

Sample preparation requires only dissolution of the sample to a suitable concentration in a mixture of water and organic solvent, commonly methanol, isopropanol, or acetonitrile. A trace of formic acid or acetic acid is often added to aid protonation of the analyte molecules in the positive ionization mode. In negative ionization mode ammonia solution or a volatile amine is added to aid deprotonation of the analyte molecules. 

Protonated and cationized species are the most commonly detected ions using the ES process if a positive ionization mode is selected. Protonation is a result of the addition of proton(s) to a neutral molecule for every proton added, a net charge of +1 will result. Similarly, canonization is due to the addition of cation(s) to a neutral molecule. Detection of cationized ions can be useful in the determination of molecular mass of unknown analytes.If ESI is operated under negative ion mode, deprotonated ions will usually be the most dominant ions. Eor either operation mode, solvent adducts of the protonated/deprotonated ions are frequently detected in ESI/MS mass spectra. 

Fig. 2.6 Titration assay of BSA and methyl orange (MO, MW 305 Da, Kj = 450 pM) by GPC spin column/ESI-MS methodology as a function of [MO]/[BSA] molar ratios in the positive ionization mode (A) and the negative ionization mode (B). The mass spectra in the top five panels are exploded...

Fig. 2.7 ESI mass spectra of ligands present in CPC spin column eluates have a linear response with increasing concentration ESI (positive ionization mode) mass spectral analysis of the eluate from the CPC spin column titration ofWY252 (MW 457 Da) with MM P-1 where the molar ratios of MM P-1/ WY252 are constant at 1 5 while their individual concentrations linearly increase. The volume injected for each sample was...

To establish a sensitive and specific liquid chromatography-mass spectrometry (time-of-flight) [LC-MS (TOF)] method for the determination of donepezil in human plasma after an oral administration of 5 mg donepezil hydrochloride tablet [29]. Alkalized plasma was extracted with isopropa-nol-n-hexane (3 97) and loratadine was used as internal standard (IS). Solutes were separated on a Cis column with a mobile phase of metha-nokacetate buffer (pH 4.0) (80 20). Detection was performed on a TOF mass spectrometry equipped with an electrospray ionization interface and operated in positive-ionization mode. Donepezil quantitation was realized by computing the peak area ratio (donepezil-loratadine) (donepezil m/z 380 [M + H]+ and loratadine m/z 383[M + H]+) and comparing them with calibration curve (r = 0.9998). The linear calibration curve was obtained in the concentration range of 0.1-15 jUg/1. The detection limit of donepezil was 0.1 /zg/1. The average recovery was more than 90%. The intra- and inter-run precision was measured to be below 15% of RSD... 

The mass spectrum of pantoprazole sodium is shown in Figure 9, and the mass fragments with their assignments are shown in Table 5. The molecular weight of pantoprazole sodium was determined by using a Finnigan AQA LC/MS system (Thermoquest) operating in positive ionization mode (probe 4.00 kV, cone 200 V). 

For the detection, a tandem mass spectrometer Quattro Micro API ESCI (Waters Corp., Milford, MA) with a triple quadrupole was employed. The instrument was operated in electrospray in the positive ionization mode (ESI+) with the following optimized parameters capillary voltage, 0.5 kV source block temperature, 130 °C nebulization and desolvation gas (nitrogen) heated at 400 °C and delivered at 800 L/h, and as cone gas at 50 L/h collision cell pressure, 3 x 1(F6 bar (argon). Data was recorded in the multiple reaction monitoring (MRM) mode by selection of the two most intense precursor-to-product ion transitions for each analyte, except for the ISs, for which only one transition was monitored. The most intense transition for each analyte was used for quantitative purposes. Table 2 shows MRM transitions, cone voltages and collision energies used for the analysis of the antidepressants included in the LC-MS/MS method. 

Since majority of illicit drugs are basic compounds, ESI in positive ionization mode is the most widely used source for these analysis, although negative ionization mode is also used in some cases. 

Waliszewski et al. (2007b) described a simple and rapid HPLC technique for vanillin determination in alcohol vanilla extract, and the method has been applied successfully for the determination of vanillin in some commercial extracts for routine analysis. de Jager et al. (2007) developed a LC-MS method for the determination of vanillin, coumarin and ethyl vanillin in vanilla products using LC-electrospray ionization in the positive ionization mode. The limits of detection for the method ranged from 0.051 to 0.073 pg/ml. 

The FAB, TSP, APCI and ESI mass spectra in the positive ionization mode display the protonated molecular ion, generally accompanied by other adducts of the molecular species and fragments resulting from the loss of one or several water molecules originating from the ring hydroxyl groups. [300-302] As an acidic function is always present in these compounds, they also yield intense ions in the negative ion mode. [303-305] The spectra... 

Table (11) gives an overview on the LC-MS methods described in the literature. The vast majority of studies has been performed with the thermospray interface in the positive ionization mode. Thermospray detection is not very sensitive [279], For procyanidins a detection limit of 1 ig has been reported [269], No data are available on the detection limits of procyanidins using other types of interfaces. So far, LC-MS has not yet been applied to the quantitative analysis of procyanidins. 

Kiehne et al. [282] who analyzed green tea using a thermospray interface in the positive ionization mode could distinguish fragments originating form upper (T) and lower (B) units of dimeric procyanidins. Cleavage of the interflavanoid bond resulted in a carbenium-ion (T-l) and a neutral fragment from the lower unit which could be protonated under the experimental conditions to form a pseudo molecular ion (B + H+). 

A comparison between APCI-LC/MS and PB-LC/MS was conducted for the determination of a priority group of herbicides in water, including phenylureas, triazines, and chlorophenoxy acids. The potential of both ionization techniques for the monitoring of environmental matrixes was demonstrated. However, APCI was approximately ten-fold more sensitive than PB, both in negative and positive ionization mode. ... 

Only one major compound (SF-X) was present in the estrogenically active fractions, and this was isolated using semipreparative HPLC. The principles of separation are the same as for qualitative HPLC (see Section 25.4.1.2), with the difference that higher amounts of material can be loaded onto the ODS-column (Alltech, Econosil, Cig lOp, 250x22mm). For the identification of SF-x, a combination of spectroscopic techniques was used. Electrospray ionization in the mass spectrometer (HPllOO LC/MSD, Hewlett-Packard) with positive ionization mode gave a pseudo-molecular ion with m/z=439. H-NMR, C-NMR, DEPT, HMQC, and COSY spectra were recorded on a Varian-300 (300MHz) spectrometer. Analysis of the COSY spectram showed the presence of a lavandulyl (5-methyl-2-isopropenyl-hex-4-enyl) side chain. From the HMQC spectrum and a DEPT experiment, it appeared that SF-x possesses a disubstituted flavanone skeleton. 

Mass spectra of desalted Photofrin, in the positive ionization modes, obtained by (A) FAB/MS, (B) UV-MALDI/MS, (C) IR-MALDI/MS, (D) ESI/MS (nozzle-skimmer voltage 100 V). (E) Mass spectrum of per-methyl ester of Photofrin, in the positive ionization mode, obtained by LD/... 

Hasses scanned 15-200 amu 1 scan each 30 seconds Positive ionization mode... 

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