On‐Demand Ambient Ionization of Picoliter Samples Using Charge Pulses

Abstract

Relay electrospray ionization (rESI) from a capillary containing a sample solution (or from an array of such capillaries) is triggered by charge deposition onto the capillary. Suitable sources of primary ions, besides electrosprays, are plasma ion and piezoelectric discharge plasma sources. With no requirement for physical contact, high-throughput sample screening is enabled by rapidly addressing individual secondary (sample) capillaries. Sub-pL sample volumes can be loaded and sprayed. Polar analytes, including neurotransmitters, phosphopeptides, oligonucleotides, illicit drugs, and pharmaceutical compounds are successfully ionized by rESI with concentration sensitivities (0.1 ppb for acetylcholine) which are similar to nanoESI but absolute sensitivities are orders of magnitude better. Nonpolar analytes (steroids, alkynes) are ionized by rESI using an open-tube secondary capillary and injecting electrolytically generated metal cations from the primary electrospray.

Mass spectrometric snapshots for electrochemical reactions

“…The high voltage added in ESI might affect the low potential applied in the EC system. Li et al 30 have recently reported a new ionization method, in which a hand-triggered piezoelectric pistol was used to generate primary ion flow, and the ions could induce spray from the capillary tip end. This new ionization strategy has negligible influence on the EC system.…”

A cautionary note on the effects of laboratory air contaminants on ambient ionization mass spectrometry measurements

“…Li et al described a new technique called relay ESI, in which a PDD plasma was used as the primary ion source. This PDD plasma ionization method has been adapted here as an open‐air ionization technique.…”

Fast Quantitation of Target Analytes in Small Volumes of Complex Samples by Matrix‐Compatible Solid‐Phase Microextraction Devices

“…V 10 mL) can undoubtedly impact the precision and efficiencyo fb iological investigations in drug-development and point-of-care (POC) diagnosis. [1][2][3][4] Facilitated by the improved sensitivity and specificity provided by modern mass spectrometry (MS) instrumentation, the replacement of traditional complex laboratory procedures with integrated miniaturized methods has become ag rowing trend in POC diagnosis. [5] In recent years,advances in direct sample to mass spectrometry techniques,s uch as paper-spray ionization, probe electrospray ionization, and touch spray [2,[5][6][7] have allowed for the application of these methods towards the quantitative analysis of small volumes of biofluids.However, the sensitivity and precision typically achieved in the laboratory through adequate sample preparation prior to the MS quantification is traded off.T herefore,techniques capable of isolating and enriching target analytes from complex matrices with minimal processing time and adequate sample clean-up are highly desirable for applications that require direct introduction to MS. [1-3, 8, 9] As ac oncept, solid-phase microextraction (SPME) embraces solventless microextraction technologies with different geometrical configurations that efficiently integrate sampling and sample clean-up,while also allowing for enrichment of the molar fraction of ag iven analyte in as ingle step.…”

“…Certainly,the ability to perform rapid equilibration under static conditions can be beneficial for applications where agitation of the sample is not possible or cumbersome (e.g.a nalysis of tissue, [10] single cells, [17] and small samples [4] ). Ther apid rate of enrichment of analytes on the tip can be explained by radial diffusion (detailed discussion about radial diffusion and SPME devices is provided on the Supporting Information).…”