Sigma-Aldrich Neutral Red (C.I. 50040) I

Quality Level

200

Form

solid

Composition

dye content, ≥75% spectrophotometric assay

Loss

≤18% loss on drying, 110°C

Ph

3.1 (20 °C, 10 g/L in H₂O)

Solubility

50 g/L

Bulk Density

350‑500 kg/m³

Amax

452-455 nm (buffer pH 8.0)
514-519 nm (buffer pH 6.8)

Λmax

540-543 nm at 50% in ethanol

Storage Temp.

2-30°C

Related Categories

Indicators

Application

• Smartphone-based sensing and in vivo and in vitro imaging of Mn(VII) based on nitrogen-doped red fluorescent carbon dots.: Li et al. present a novel smartphone-based sensor system utilizing nitrogen-doped red fluorescent carbon dots for detecting Mn(VII) ions. The study leverages the red fluorescence properties of these carbon dots for in vivo and in vitro imaging, enhancing detection accuracy and application in environmental monitoring and biological imaging (Li et al., 2024).


• A "2-in-1" Bioanalytical System Based on Nanocomposite Conductive Polymers for Early Detection of Surface Water Pollution.: Kharkova et al. develop a bioanalytical system integrating nanocomposite conductive polymers to detect surface water pollution. Neutral red is used as an indicator for the electrochemical detection of pollutants, demonstrating the system′s potential for early and accurate environmental monitoring (Kharkova et al., 2024).


• Programable sewage-cleaning technology: Regenerating chitosan biofilms with anti-bacterial capacity via self-purification of water pollutants.: Wu et al. explore a programmable sewage-cleaning technology that regenerates chitosan biofilms with antibacterial properties. Neutral red plays a critical role in evaluating the biofilms′ effectiveness in self-purification processes, offering insights into sustainable wastewater management (Wu et al., 2024).


• Characteristics and adsorption behavior of typical microplastics in long-term accelerated weathering simulation.: Yu et al. examine the characteristics and adsorption behavior of microplastics under long-term weathering. Neutral red staining is employed to study the surface interactions and degradation patterns of microplastics, providing valuable data for environmental impact assessments (Yu et al., 2024).

Analysis Note

Dye content (spectrophotometrically): ≥ 75 %
Identity (UV/VIS-Spectrum): passes test
Transition range: pH 6.8 - pH 8.0 Violet red - orange yellow
Absorption maximum λ_max.(ethanol 50 %): 540 - 543 nm
Absorption maximum λ 1 (buffer pH 6.8): 514 - 519 nm
Absorption maximum λ 2 (buffer pH 8.0): 452 - 455 nm
Spec. Absorptivity A 1%/1cm (λ_max; 0.005 g/l; ethanol 50 %): 1180 - 1610
Spec. Absorptivity A 1%/1cm (λ1_max; 0.015 g/l; buffer pH 6.8; calc. on dried substances): 425 - 575
Spec. Absorptivity A 1%/1cm (λ2_max; 0.015 g/l; buffer pH 8.0; calc. on dried substances): 395 - 535
TLC-Test: passes test
Loss on drying (110 °C): ≤ 18 %
Suitability for microbiology: passes test

Storage Class

11 - Combustible Solids

Wgk_Germany

WGK 3

Flash_Point_F

Not applicable

Flash_Point_C

Not applicable