Overview
The Andrade Indicator is a specialized pH indicator primarily used in microbiological applications, particularly for detecting carbohydrate fermentation in bacterial cultures. Developed in the early 20th century, it remains a staple in clinical and research laboratories worldwide. The indicator consists of acid fuchsin in a slightly alkaline solution, producing distinctive color changes that help researchers identify metabolic activity. Its stability and clear visual transition make it preferable to many alternative indicators for specific microbiological applications.
Physical and Chemical Properties
As a triphenylmethane dye derivative, Andrade Indicator exhibits unique optical properties. In solution form, it appears reddish-brown at neutral pH but undergoes distinct color changes across its transition range (pH 6.8-8.4). The compound demonstrates good stability when properly stored, though prolonged exposure to light or extreme temperatures may degrade its performance. Its water solubility allows for easy incorporation into liquid media, while the molecular structure ensures minimal interference with microbial growth processes.
Main Applications
The primary application of Andrade Indicator is in carbohydrate fermentation tests, where it helps identify bacterial species based on their metabolic byproducts. Clinical laboratories use it extensively in diagnostic media for enteric pathogens. Additional applications include pH monitoring in specialized culture media and as a component in certain differential agar formulations. Some industrial fermentation processes also employ modified versions of the indicator for process monitoring.
Safety and Storage
While not classified as highly hazardous, Andrade Indicator requires standard laboratory precautions. Powdered form may cause respiratory irritation, requiring dust control measures during preparation. For optimal shelf life, store the dry powder in airtight containers with desiccant at room temperature. Prepared solutions should be refrigerated and protected from light, with expiration typically within 3-6 months depending on concentration and storage conditions.
B2B Procurement Guide
When sourcing Andrade Indicator, verify the supplier's certification for microbiological-grade chemicals. Key specifications include purity (≥95%), heavy metal content (<10ppm), and microbiological purity (sterility where required). Bulk purchases (100g+) typically offer better value, but consider usage rates to avoid degradation of large stocks. Request batch-specific certificates of analysis and confirm compatibility with your specific application media formulations.
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