‌Detection Methods for Benzaldehyde‌
Detection methods for benzaldehyde primarily include instrumental analytical techniques such as ‌gas chromatography (GC)‌, ‌high-performance liquid chromatography (HPLC)‌, ‌ultraviolet-visible spectrophotometry (UV-Vis)‌, along with chemical identification methods like the ‌silver mirror test‌ and ‌Fehling's reagent test‌.

‌Instrumental Analysis Methods‌

1. ‌Gas Chromatography (GC)‌

   • Based on the National Standard (GB 28320—2012), benzaldehyde content is quantified using a capillary column with a hydrogen flame ionization detector (FID) and area normalization method.
   • Typical operating conditions:
     • Oven temperature: 140°C
     • Carrier gas (N₂) flow rate: ~30 mL/min
     • Injection volume: 0.2 μL
   • Suitable for separating and quantifying gaseous or volatile liquid samples, offering high sensitivity and reproducibility.

2. ‌High-Performance Liquid Chromatography (HPLC)‌

   • Employs a gradient elution system with phosphoric acid–water and phosphoric acid–acetonitrile as the mobile phase.
   • Detection wavelength: 220–257 nm.
   • Ideal for detecting benzaldehyde in liquid samples (e.g., pharmaceutical formulations), providing excellent separation and specificity.

3. ‌UV-Vis Spectrophotometry‌

   • Quantifies benzaldehyde concentration by measuring absorbance at specific wavelengths and using a standard calibration curve.
   • Advantages: Simple operation and low cost.

‌Chemical Identification Methods‌

1. ‌Silver Mirror Test‌

   • Benzaldehyde reacts with Tollens' reagent (ammoniacal silver nitrate) upon heating to form a silver mirror, distinguishing it from non-aldehydic compounds (e.g., acetophenone).

2. ‌Fehling's Reagent Test‌

   • Benzaldehyde does ‌not‌ produce a brick-red precipitate when heated with Fehling's reagent (newly prepared cupric hydroxide suspension), differentiating it from stronger reducing aldehydes like formaldehyde.

3. ‌Iodoform Test‌

   • Acetaldehyde forms a yellow iodoform precipitate with alkaline iodine solution, while benzaldehyde shows no such reaction. Used to distinguish aldehydes in mixed samples.

‌Note‌: Source: Web content.