Sorbitan Monostearate, commercially known as Emulsifier Span-60 (S-60), has an HLB value of 4.70 and appears as a beige, solid block. It is odorless and non-toxic. It can be dispersed in hot water, dissolved in hot ethanol or benzene, and is slightly soluble in ether or petroleum ether. It exhibits strong emulsifying, dispersing, and wetting capabilities and demonstrates good compatibility with various types of surfactants. It belongs to the non-ionic surfactant category.Mechanism of Action

•Emulsification and Stabilization

•HLB Value Property: With an HLB value of 4.7, it is a low-HLB, non-ionic surfactant that preferentially forms Water-in-Oil (W/O) emulsions. It stabilizes against emulsion separation in detection systems by reducing oil-water interfacial tension.

•Solubilization and Dispersion: Enhances the dispersibility of lipid-soluble components (such as certain chemiluminescent substrates or organic solvents) in the aqueous phase, preventing precipitation.

•Wetting and Penetration Enhancement

•Improves the wettability of substrates like microplates and glass slides, reducing liquid spreading resistance and enhancing reagent flow uniformity.

•Can assist in the release of antibodies or antigens from samples (e.g., pre-treatment before cell lysis).

•Compatibility

•Exhibits good compatibility with cationic, anionic, and amphoteric surfactants. Its HLB value can be adjusted through blending with other surfactants to optimize system stability.

Application Scenarios

•Lateral Flow Immunoassays and ELISA

•Blocking Buffer / Diluent: Improves the uniform distribution of antibodies on the microplate surface, reducing edge effects.

•Emulsion-based Reagents: Used to stabilize reconstitution solutions containing lipid antigens or antibodies (e.g., coating of latex particles in certain viral detection assays).

•Chemiluminescence Detection

•Disperses lipid-soluble luminescent substrates (e.g., luminol derivatives), improving their solubility in the reaction solution and luminescence efficiency.

•Molecular Diagnostics

•Nucleic Acid Extraction: Assists in cell membrane lysis, promoting the release of DNA/RNA (concentration must be validated for its effect on nucleic acid integrity).

•LAMP/PCR Reactions: Eliminates bubble interference and stabilizes the reaction system.

•Microplate Pre-treatment

•Acts as a wetting agent to reduce liquid hang-up on walls, improving pipetting accuracy.

Conventional Concentration Range

•Emulsion Systems: 0.5% - 5% (requires adjustment based on the oil phase ratio).

•Blocking Buffer / Diluent: 0.1% - 1%.

•Nucleic Acid Extraction: 1% - 3% (requires experimental validation of its effect on the target nucleic acid).

Dissolution Method

•Solid Dissolution: First heat above 60°C (soluble in hot water or hot ethanol), stir until completely dissolved, then allow to cool slowly.

•Premixed Storage: It is recommended to prepare a high-concentration stock solution (e.g., 10% Span-60 solution) and dilute as needed before use.

Precautions

•Storage Conditions: Store sealed in a dry place, protected from light to avoid moisture absorption and caking.

•Slight stratification may occur during long-term storage; shake well before use.

•Experimental Condition Control

•Temperature Sensitivity: High temperatures (>80°C) may cause partial inactivation; temperature control during preparation is recommended.

•pH Compatibility: Stable within the pH range of 5-9; susceptible to hydrolysis and inactivation under strong acid/alkali conditions.

•Material Compatibility

•Plastic Containers: Long-term contact may cause swelling of polyethylene (PE) or polypropylene (PP) containers; short-term use or switching to glass/stainless steel containers is advised.

•Protein Interference: Excessive amounts may adsorb to antibodies or antigens; concentration should be optimized through preliminary experiments.

•Foam Control

•The low HLB value may cause foaming; this can be mitigated by adding small amounts of defoamers (e.g., silicone-based) or by operating at lower temperatures.