وگز پرسکور(VP – A)

Voges–Proskauer Reagent A (VP‑A) is an alcoholic solution of α‑naphthol used as the first reagent in the Voges–Proskauer test for detecting acetoin production by bacteria.

🏭⚗️ Production
VP‑A is prepared by dissolving α‑naphthol in absolute ethanol at a concentration typically near 5% (w/v). The solution is stored in a tightly sealed, light‑protected container to maintain reagent stability and reactivity.

🔬 Properties
This reagent appears as a clear, pale yellow to colorless liquid with strong aromatic odor from ethanol. Under reactive conditions, it enhances the color development of the VP test by acting as a color intensifier for the diacetyl–guanidine complex that forms when acetoin is oxidized.

🧪 Applications
VP‑A is used in the first step of the Voges–Proskauer test, where it is added to a bacterial culture grown in glucose‑phosphate (MR‑VP) broth. When followed by addition of VP‑B (strong base such as 40% KOH) and exposure to oxygen, it contributes to the formation of a pink‑red color in the presence of acetoin, indicating a positive result.

⚠️ Safety
VP‑A contains ethanol and should be handled with care. It is flammable and can cause eye or skin irritation. Use protective eyewear and gloves and store the reagent at cool temperature, away from ignition sources.