Capillary Electrophoresis (CE) Systems

Capillary Electrophoresis (CE) encompasses a family of high-resolution separation platforms that use an electric field to separate biomolecules based on charge, size, or isoelectric point (pI).
CE technologies are foundational in biopharmaceutical analytics and are widely used across biologics, gene therapies, and nucleic acid products to characterize identity, purity, heterogeneity, and structural integrity of both drug substance and drug product.

Technology Overview

Capillary Electrophoresis (CE) is the overarching platform technology. It supports multiple separation modes (e.g., CGE, CE-SDS, cIEF, CZE), which can be implemented using two common instrument formats.

Separation Mode Example: Capillary Gel Electrophoresis (CGE)

Capillary Gel Electrophoresis (CGE) is a CE separation mode in which a polymer sieving matrix ("gel") is used to achieve size-based separation of biomolecules.

• For nucleic acids: CGE is commonly used for RNA and DNA integrity, sizing, and purity profiling.
• For proteins: Size-based CE separations are typically implemented as CE-SDS, a denaturing CGE variant in which proteins are denatured and coated with SDS to impart uniform negative charge-to-mass ratio, enabling separation primarily by molecular weight (similar to SDS-PAGE).

The polymer matrix used for CGE may be:

• Manually prepared and loaded into classical capillaries
• Pre-formulated inside disposable chips, cartridges, or capillary array systems used in automated platforms

Note: The underlying separation principle, migration through a polymer network under an electric field is the same across formats. The difference lies in implementation and operational model.

Instrument Implementation Formats

1. Classical Capillary Electrophoresis Systems

(e.g., SCIEX PA 800 Plus, Agilent 7100 CE)

Format:
Use replaceable fused-silica capillaries with user-prepared buffers and (where applicable) polymer matrices.

Flexibility:
Highly configurable separation chemistry and detection modes (e.g., UV, LIF, PDA).

Capabilities:
Support multiple CE separation modes on the same instrument, including:

• Capillary Gel Electrophoresis (CGE)
• CE-SDS (for proteins)
• Capillary Isoelectric Focusing (cIEF)
• Capillary Zone Electrophoresis (CZE)

Detection Options:

• UV/UV-Vis absorbance (single wavelength or scanning)
• Laser-Induced Fluorescence (LIF) - provides 10-1000× enhanced sensitivity
• Photodiode Array (PDA) - multi-wavelength detection

Use Case:
Commonly used for method development, advanced characterization, and, where validated, release assays (e.g., purity, charge variant, or heterogeneity methods).

2. Automated / Standardized CE Systems

(e.g., Agilent Bioanalyzer, TapeStation, Fragment Analyzer; Bio-Techne Maurice)

Format:
Use standardized, manufacturer-supplied consumables:

• Microfluidic chips (Bioanalyzer) - single-use chips with pre-filled gel matrix
• Tape cartridges (TapeStation) - multi-sample tape with pre-filled reagents
• Capillary arrays with reagent kits (Fragment Analyzer) - 48- or 96-capillary arrays with bottled reagents

Standardization:
Highly standardized workflows with minimal user intervention and reduced operator variability.

Capabilities:
Optimized for specific applications depending on platform and consumable chemistry:

• RNA integrity and size profiling (CGE-based)
• DNA fragment analysis (CGE-based)
• Protein purity and characterization (CE-SDS, icIEF - platform-dependent)

Use Case:
Commonly used for routine QC, high-throughput screening, and lot release where reproducibility, robustness, and speed are prioritized.

Platform-Specific Notes:

• Bioanalyzer/TapeStation/Fragment Analyzer: Primarily designed for nucleic acid applications (RNA/DNA integrity, sizing, quantitation)
• Bio-Techne Maurice: Protein-focused platform with whole-column imaging for icIEF and CE-SDS

Common CE Separation Modes

Common Platforms & Models

Automated Systems for Nucleic Acids (CGE-based):

• Agilent Bioanalyzer Systems (microfluidic chip-based)
• Agilent TapeStation Systems (tape cartridge-based)
• Agilent Fragment Analyzer Systems (48- or 96-capillary array; formerly Advanced Analytical)

Classical Multi-Mode Systems:

• SCIEX PA 800 Plus Pharmaceutical Analysis System (CGE, CE-SDS, cIEF, CZE)
• Agilent 7100 Capillary Electrophoresis System (CGE, CE-SDS, cIEF, CZE)

Protein-Focused Imaging Platforms:

• Bio-Techne Maurice (ProteinSimple brand; icIEF and CE-SDS with whole-column imaging)
• ProteinSimple iCE3 (dedicated icIEF platform with whole-column imaging)

Detection Methods in CE

Laser-Induced Fluorescence (LIF) Detection

LIF is a highly sensitive detection method that can be coupled with various CE separation modes (CGE, CZE, cIEF).

Key Points:

• LIF is NOT a separation mode; it is a detection technique
• Provides 10-1000× greater sensitivity compared to UV detection
• Requires fluorescently labeled analytes OR fluorescent intercalating dyes (for nucleic acids)

Common Applications:

• Glycan analysis (APTS or 2-AB labeled)
• Oligonucleotide purity (fluorescent label or intercalating dye)
• Labeled protein analysis
• RNA/DNA integrity (with intercalating dyes in automated systems)

Availability:

• Classical CE systems: Optional LIF detector module (e.g., SCIEX PA 800 Plus with LIF detector)
• Automated systems: Built-in fluorescence detection (e.g., Bioanalyzer uses intercalating dyes)