Electrochemical Flow Cell with Sample Loop for Automated Analysis
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Solution Overview
Problem
Existing electrochemical flow cell systems for analyzing electrochemically active substances face limitations in controlling oxidation/reduction conditions, are prone to fouling, and lack automation for sequential analysis of multiple samples, especially when integrated with mass spectrometry or NMR spectrometry.
Innovation Solution
An apparatus with an electrochemical flow cell integrated into the sample aspiration path of an automatic sampling device, decoupled from the structure elucidation spectrometer, allowing for two operating modes to control electrochemical conversion conditions independently and enable automated sequential analysis of multiple samples.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Extent of automation
If an electrochemical flow cell is integrated into the LC flow path for online analysis, then automated sequential analysis is possible, but the oxidation/reduction conditions are governed by LC separation conditions which limits control over flow rate, mobile phase composition and pH
Solution Approach 1:
The system is divided into two independent modules: an LC system for sample separation and an EC system for electrochemical conversion. The EC flow cell is connected via a sample loop and injection valve, allowing independent optimization of LC separation conditions and EC conversion conditions (flow rate, mobile phase composition, pH) without mutual interference.
Solution Approach 2:
A sample loop and injection valve are introduced as intermediary components between the LC system and EC system. The LC eluate is transferred to the sample loop, then injected into the EC flow cell. This intermediary mechanism enables automated sequential analysis while decoupling the control of LC and EC parameters.
2Reliability
If a coulometric electrochemical flow cell is used to minimize fouling, then high solvent concentrations (50% or more) are required, but this adversely affects the separation performance of HPLC
Solution Approach 1:
The system separates the HPLC separation module from the EC conversion module. The HPLC operates with optimal mobile phase composition for separation, while the EC module receives the eluate through a sample loop. This segmentation allows the EC flow cell to use high solvent concentrations for fouling resistance without affecting HPLC separation performance.
Solution Approach 2:
The sample loop acts as an intermediary that decouples the mobile phase requirements of HPLC and EC. The HPLC mobile phase is transferred to the sample loop, then injected into the EC flow cell where different solvent concentrations can be used without interfering with HPLC separation.
3Stress or pressure
If high pressure electrochemical cells are used to withstand UHPLC pressures of more than 1500 bar, then the system can handle UHPLC flows, but such cells are not yet available
Solution Approach 1:
A sample loop and injection valve are introduced as intermediary components between the UHPLC system and the EC flow cell. The UHPLC eluate is transferred to the sample loop under high pressure, then the injection valve switches to inject the sample into the EC flow cell which operates at atmospheric or low pressure. This intermediary mechanism allows UHPLC operation without requiring high-pressure resistant EC cells.
4Adaptability or versatility
If follow-up reactions are performed by adding reactants using an infusion pump and mixing coil, then chemical reactions can be studied, but this configuration is not suitable for automated screening with a large variety of different reactants
Solution Approach 1:
The system uses a sample loop and injection valve configuration that can accommodate multiple reactants by simply changing the injection sequence and timing. The EC flow cell remains the same, but different reactant combinations can be studied by programmatically controlling the injection valve and pump sequences, enabling automated high-throughput screening with diverse reactants.
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 allows for uncompromised selection of electrochemical and separation conditions, reduces fouling, supports high-pressure operations, and enables automated analysis of multiple samples without user intervention, improving the efficiency and reliability of redox behavior screening.
Implementation Method 1
an electrochemical flow cell (20) integrated into the sample aspiration path of an automatic sampling device... in which a potential is applied to produce a flow of electrochemically treated (oxidized or reduced) sample
Data Source
Figure 1a~1b
Figure 1c~1d
Figure 1e~1f
AI summary
The invention provides an apparatus for sequentially analyzing a plurality of samples containing electrochemically active substances, said apparatus comprising: a sample conduit (10); an electrochemical flow cell (20); a source of carrier fluid (30); a structure elucidation spectrometer (40) (MS or NMR); a conduit (60) and an in-line sample reservoir (50) (e.g. a sample loop), wherein the apparatus is arranged to operate in: a) a first operating modus wherein the sample conduit (10) is connected to the conduit (60) via the electrochemical flow cell (20) and the in-line sample reservoir (50), and the source of carrier fluid (30) is connected to the spectrometer (40) by-passing the in-line sample reservoir, and b) a second operating modus wherein the sample conduit (10) is connected to the conduit (60) by-passing the in-line sample reservoir, and the source of carrier fluid is connected to the structure elucidation spectrometer (40) via the in-line sample reservoir (50).