Electrospray Of Solutions Research Articles

Cyclic Ion Mobility of Isomeric New Psychoactive Substances Employing Characteristic Arrival Time Distribution Profiles and Adduct Separation.

Analysis of new psychoactive substances (NPS), which is essential for toxicological and forensic reasons, can be made complicated by the presence of isomers. Ion mobility has been used as a standalone technique or coupled to mass spectrometry to detect and identify NPS. However, isomer separation has so far chiefly relied on chromatography. Here we report on the determination of isomeric ratios using cyclic ion mobility-mass spectrometry without any chromatographic separation. Isomers were distinguished by mobility separation of lithium adducts. Alternatively, we used arrival time distribution (ATD) profiles that were characteristic of individual isomers and were acquired for protonated molecules or fragment ions. Both approaches provided comparable results. Calculations were used to determine the structures and collision cross sections of both protonated and lithiated isomers that accurately characterized their ion mobility properties. The applicability of ATD profiles to isomer differentiation was demonstrated using direct infusion and flow injection analysis with electrospray of solutions, as well as desorption electrospray of solid samples. Data processing was performed by applying multiple linear regression to the ATD profiles. Using the proposed ATD profile-based approach, the relationships between the determined and given content of isomers showed good linearity with coefficients of determination typically greater than 0.99. Flow injection analysis using an autosampler allowed us to rapidly determine isomeric ratios in a sample containing two isomeric pairs with a minor isomer of 10% (determined 9.3% of 3-MMC and 11.0% of 3-FMC in a mixture with buphedrone and 4-FMC). The proposed approach is not only useful for NPS, but also may be applicable to small isomeric molecules analyzed by ion mobility when complete separation of isomers is not achieved.

Disintegration of the Negative Ions of Monochloroacetic Acid in the Analysis of Its Aqueous Solution with the Use of Electrospray Ionization

The negative ion mass spectrum of an aqueous solution of completely neutralized monochloroacetic acid (MCAA) was measured by a mass-spectrometric method of electrolyte solution electrospray in a vacuum. It was found that the negative ions of the MCAA acid residue, which were formed on the dissociation of MCAA molecules in water, decomposed under the electrospray. The efficiency of disintegration depends on the isotope of chlorine in the MCAA molecule.

Failure of ESI Spectra to Represent Metal-Complex Solution Composition: A Study of Lanthanide–Carboxylate Complexes

Electrospray ionization-mass spectrometry (ESI-MS) shows great promise as a rapid method to identify metal-ligand complexes in solution. However, its application for quantitative determination of the distribution of species present in complicated equilibria is still in its infancy, and a direct correlation between ions observed in the gas phase and species expected in solution must be made with caution. The present work focuses on a seemingly simple system; the complexation of lanthanide cations with the acetate ligand. Using a high resolution quadrupole time-of-flight mass spectrometer, ions created by electrospray of solutions containing trivalent neodymium and acetate were identified. The gas phase distribution of species was compared to the solution phase speciation predicted using thermodynamic complexation constants. Apparent gas phase speciation diagrams were constructed as a function of solution conditions and fragmentation potential. Despite the expected variability of metal-ligand complexes as solution conditions change, the observed gas phase speciation was independent of the metal to ligand ratio but dependent on the operating conditions of the ESI-MS.

Characterisation of pharmaceutical materials produced by electrospraying

Electrospraying of solutions or suspensions provides a method for production of fine particles, in certain conditions even down to nanometer size. In the present study, electrospraying was used in drug particle production. The most important properties of the produced particles in a pharmaceutical sense are size distribution, degree of crystallinity and porosity. The size of the produced particles can easily be tailored by varying the concentration of the dissolved material, electric field strength or liquid flow rate. Most experiments on electrospraying are performed at atmospheric pressure. In the present study, the produced particles were dried under atmospheric or reduced pressure, the latter in order to improve the drying process. The effect of pressure reduction on the degree of crystallinity of the produced drug particles was studied by XRD and DSC. Also the porosity of the particles depends mainly on the drying conditions. The porosity and size of the produced particles was studied by SEM imaging.

Nanoelectrospray Ion Mobility Spectrometry Online with Inductively Coupled Plasma-Mass Spectrometry for Sizing Large Proteins, DNA, and Nanoparticles

Recently it has been demonstrated that nanoelectrospray (nES) in conjunction with macro-ion mobility spectrometry (macroIMS) and condensed particle detection can be used to size various types of nanoparticles, including large biomolecules (proteins, DNA, etc.), having electrophoretic mobility diameters ranging from 3 nm to well over 100 nm. The technique is extremely sensitive; however, it lacks specificity as a result of the detector used. To explore the possibility to overcome this limitation, we demonstrate the direct coupling of the nES-macroIMS system to an inductively coupled plasma mass spectrometer (ICPMS). Technical challenges involving the coupling of the air-based nES-macroIMS with the argon-based ICPMS are addressed and overcome. The resulting novel hyphenated technique is used to determine the elemental composition of nanoparticles resulting from the electrospraying of solutions containing inorganic salts and acids (CsI and dimethylarsinic acid). Even though the sensitivity of the used ICPMS does not allow for the simultaneous sizing of proteins and the determination of their metal, metalloid, or halogen content, we have shown that it is feasible to detect and accurately size proteins at femtomole levels by adding CsI to their solutions and detecting the resulting Cs adducts. This is also possible with DNA molecules. A linear relationship between protein amount and ICPMS response for (133)Cs(+) is observed, thus hinting at the possibility of further developing the technique for quantitative analysis of large biomolecules.

Features of electrospray of solutions with different physico-chemical parameters

Features of electrospray of solutions with different physico-chemical parameters