Why is Congo red test paper used instead of the litmus paper?
Why is Congo red test paper used instead of the litmus paper?
Due to a color change from blue to red at pH 3.0–5.2, Congo red can be used as a pH indicator. Since this color change is an approximate inverse of that of litmus, it can be used with litmus paper in a simple parlor trick: add a drop or two of Congo red to both an acid solution and a base solution.
Is Congo Red basic or acidic?
Congo red is an acid-base indicator dye. In free solution the colour and absorption characteristics of Congo red depend not only on the pH but are also governed by the nature of the solvent environment.
How does congo red indicator work?
Congo red was formerly used to dye cotton but has been superseded by dyes more resistant to light and to washing. It is still used in histology to stain tissues for microscopic examination, and to serve as an acid-base indicator, since it turns red in the presence of alkalies and blue when exposed to acids.
How do you make a 0.1% Congo Red solution?
Add 50 mL of 100% ethanol. 1% potassium hydroxide solution: • Dissolve 1 g of potassium hydroxide in 50 ml of distilled/demineralized water. 0.2% solution of Congo Red powder dye: • Dilute 0.1 g of Congo Red powder dye in 50 ml of solution of sodium chloride and alcohol.
What does Congo red test for?
Congo red is still the standard stain used in most histopathology laboratories to identify amyloid material in tissues. The identification of Congophilic amyloid material is challenging because of multiple interfering factors.
Can you autoclave Congo red?
Dissolve, autoclave at 121°C for 15 min and pour 20 ml per plate.
What type of dye Congo red is?
Congo Red is an indicator dye that is blue-violet at pH 3.0 and red at pH 5.0. It contains a 3,3′-(biphenyl-4,4′-diyldidiazene-2,1-diyl)bis(4-aminonaphthalene-1-sulfonate).
What is Congo red dye?
Congo Red is the sodium salt of benzidinediazo-bis-1-naphthylamine-4-sulfonic acid; a diazo dye that is red in alkaline solution and blue in acid solution and used especially as an indicator and as a biological stain. NCI Thesaurus (NCIt) Congo Red is an indicator dye that is blue-violet at pH 3.0 and red at pH 5.0.
How does the Congo red dot paper test work?
The CRD Paper Test outperformed measured serum and urine markers (80·2% sensitivity, 89·2% specificity, 92·1% negative predictive value, 86·7% accuracy). The pre-test, positive and negative post-test probabilities were 27·7%, 74·0%, and 8·0%, respectively.
When to use Congo red as a pH indicator?
Congo red ( pH indicator) below pH 3.0. above pH 5.2. 3.0. ⇌. 5.2. Due to a color change from blue to red at pH 3.0–5.2, Congo red can be used as a pH indicator. Since this color change is an approximate inverse of that of litmus, it can be used with litmus paper in a simple parlor trick: add a drop or two of Congo red to both an acid solution
Can you use Congo red with litmus paper?
Since this color change is an approximate inverse of that of litmus, it can be used with litmus paper in a simple parlor trick: add a drop or two of Congo red to both an acid solution and a base solution. Dipping red litmus paper in the red solution will turn it blue, while dipping blue litmus paper in the blue solution will turn it red.
Is there a blood test for Congo red dye?
We observed that proteins in the urine of preeclamptic women bind Congo Red dye, a feature called urine congophilia. To that end, our group reported that urine congophilia carries diagnostic potential for PE. However, previous research was focused on laboratory-based techniques and validation of congophilia.