Pneumatically-assisted electrospray emitter array for high flow LC-MS
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Solution Overview
Problem
Conventional electrospray ionization methods, such as nanospray, are limited by low flow rates, making them unsuitable for high-flow applications like LC-MS, where larger emitters with pneumatic assist are needed, but these setups suffer from reduced sensitivity due to incompatible droplet sizes and non-uniform sheath gas distribution, leading to decreased ion capture by the mass spectrometer.
Innovation Solution
The use of a plurality of electrospray assemblies with circumferentially surrounding sheath gas flow, allowing each assembly to handle a fraction of the total analyte-bearing liquid flow, with each emitter being smaller than conventional capillaries to produce smaller droplets that are efficiently desolvated and directed to the mass spectrometer, while the sheath gas ensures uniform emission and prevents coalescence.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If larger bore needles are employed for high flow rates, then flow rate capacity is improved, but droplet size increases and sensitivity decreases
Solution Approach 1:
The invention divides a single large-bore needle into multiple smaller-bore needles arranged in an array. Each needle handles a fraction of the total flow rate while producing small droplets. This segmentation allows the system to accommodate high total flow rates (improving productivity) while maintaining small droplet sizes (preserving sensitivity and manufacturing precision).
Solution Approach 2:
The invention introduces sheath gas as an intermediary substance that flows around the analyte-bearing liquid through the needle array. The sheath gas performs multiple functions: it focuses the electrospray plume, assists in desolvation of droplets, and directs ions toward the mass spectrometer inlet. This intermediary enables efficient ion capture despite the distributed nature of multiple needles.
2Productivity
If multiple emitters are used to increase flow rate capacity, then flow rate handling is improved, but ion capture efficiency decreases due to non-uniform sheath gas distribution
Solution Approach 1:
The invention configures sheath gas flow to locally surround each individual needle in the array rather than providing uniform flow across the entire array. This local quality approach ensures that each emitter receives adequate sheath gas for focused plume formation and efficient ion capture, maintaining reliability even as the number of emitters increases to handle higher flow rates.
Solution Approach 2:
The invention transitions from a single-point electrospray source to a distributed array of multiple needle emitters arranged in two or more dimensions. This dimensional change allows the system to increase total flow rate capacity while maintaining effective ion capture through the introduction of sheath gas that operates in the spatial dimension surrounding the needle array.
3Manufacturing precision
If nanospray ionization is used, then sensitivity is improved, but flow rate capacity is limited
Solution Approach 1:
The invention segments the total liquid flow into multiple separate streams, each passing through a small-bore needle capable of nanospray operation. By dividing the total flow rate among multiple needles (e.g., 100 μL/min total flow divided into ten 10 μL/min streams), the system maintains the sensitivity advantages of nanospray while achieving high overall flow rate capacity.
Solution Approach 2:
The invention combines multiple nanospray emitters into a single array configuration that functions as one integrated high-flow ion source. The individual nanospray signals from multiple needles are merged in space and time, allowing the system to achieve both the sensitivity of nanospray and the productivity of high flow rates.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach enhances sensitivity by maintaining high flow rates while ensuring that a larger proportion of ions are directed into the mass spectrometer, improving the instrument's sensitivity and reducing the need for larger vacuum systems and additional components.
Implementation Method 1
pneumatically-assisted electrospray emitter array
Implementation Method 2
a plurality of sheath gas conduits, each sheath gas conduit comprising an inlet configured to receive a sheath gas portion from the source of sheath gas; and an outlet configured to emit a sheath gas flow that circumferentially surrounds, in at least two dimensions, a portion of the charged droplets emitted from a respective one of the liquid conduit outlets
Implementation Method 3
at least one electrode for producing electrospray emission of charged droplets from an outlet of each of said liquid conduits under application of an electrical potential to the at least one electrode
Implementation Method 4
an ion transfer tube that is heated to help desolvate remaining droplets or ion/solvent clusters
Implementation Method 5
A strong electric field in the tube lens following the ion transfer tube also aids in breaking up solvent clusters
Data Source
Figure 1
Figure 2
Figure 3A~3B
AI summary
An electrospray ion source comprises a source of analyte-bearing liquid; a source of sheath gas; a plurality of liquid conduits, each configured so as to receive a portion of the analyte-bearing liquid; at least one electrode associated with the plurality of liquid conduits for producing electrospray emission of charged droplets from an outlet of each of the liquid conduits; a power supply electrically coupled to the at least one electrode for maintaining the at least one electrodes at an electrical potential; and either one or a plurality of sheath gas conduits, each sheath gas conduit comprising an inlet configured to receive sheath gas and an outlet configured to emit a sheath gas flow that circumferentially surrounds, in at least two dimensions, a portion of the emitted charged droplets.