Fluorescein sodium salt | CAS 518-47-8

Fluorescein sodium salt is a widely used fluorescein-class dye that provides strong visible fluorescence for labeling, tracing, and fluorescence readouts in aqueous systems. As the sodium salt form, it is commonly employed to improve handling and water compatibility for fluorescence microscopy, plate-based assays, and conjugate preparation workflows. Its emission properties make it a practical choice for experiments that rely on sensitive detection in the green channel.

1. Fluorescence Labeling Reagents

Fluorescein sodium salt is frequently used as a fluorescent labeling dye in research workflows where investigators need to introduce a green-emitting tag onto proteins, peptides, polymers, or other biomolecule conjugates. In many laboratories, it serves as a starting fluorophore for preparing fluorescent conjugates for binding studies, reagent tracking, and assay development, particularly when the downstream conjugate will be read on common fluorescence imaging or plate-reader platforms. Researchers also use fluorescein-labeled materials to visualize transport and distribution in complex mixtures, including labeled macromolecules in solution or immobilized on surfaces.

2. Fluorescence Microscopy Tracing

Fluorescein sodium salt is used in fluorescence microscopy to trace labeled species and monitor relative localization in cell culture and materials imaging experiments. Imaging teams often incorporate fluorescein into staining or labeling strategies to follow diffusion, uptake-like behavior in experimental systems, or the spatial distribution of labeled probes within fixed samples or prepared microscopy specimens. Because fluorescein emission is well aligned with standard green fluorescence channels, it is commonly selected for multicolor experimental designs where a fluorescein-based signal is convenient to detect and quantify using routine microscope filter sets.

3. Plate-Based Fluorescence Assays

Fluorescein sodium salt is widely applied in fluorescence-based bioassay development and screening workflows that use dye fluorescence as a measurable readout. Assay developers use fluorescein either directly as a fluorescence standard or as a component in assay formats where fluorescent signal intensity is tracked over time in microplate readers. This includes experiments designed to monitor binding events, reagent stability, or process-related changes in labeled systems, leveraging fluorescein's strong emission for straightforward quantitative measurement.

4. Flow Cytometry Fluorescent Standards

Fluorescein sodium salt is also used to support flow cytometry workflows, particularly for creating fluorescence reference materials and calibrating instrument settings for green-channel measurements. Cytometry users commonly employ fluorescein-containing standards to verify detector alignment, establish gating baselines, and compare fluorescence responses across runs in method development and assay optimization studies. In conjugate evaluation workflows, fluorescein can be used as a convenient reference dye when assessing fluorescent labeling performance of candidate reagents prior to committing to more specialized fluorophores.