Infrared (IR) spectroscopy reveals characteristic peaks for amoxicillin’s functional groups. Expect strong absorption bands around 3300-3500 cm-1 (O-H and N-H stretching), 1760-1780 cm-1 (β-lactam carbonyl stretching), and 1600-1650 cm-1 (amide I and aromatic C=C stretching). Variations in peak intensities and positions can indicate differences in crystalline form or hydration.
Nuclear Magnetic Resonance (NMR) Spectroscopy
1H NMR provides detailed structural information. Key proton signals include those from the aromatic ring (δ 6.5-8.0 ppm), the methoxy group (δ 3.5-4.0 ppm), and the various protons on the amino and hydroxyl groups (δ 3.0-5.0 ppm). 13C NMR complements this, confirming the presence and connectivity of all carbon atoms within the molecule.
Ultraviolet (UV) Spectroscopy
UV spectroscopy is useful for quantification and purity assessment. Amoxicillin exhibits strong absorbance in the UV region, typically with a maximum absorbance (λmax) around 265 nm. This is due to the presence of the aromatic ring and conjugated double bonds. Analyzing the absorbance at this wavelength allows for concentration determination using a Beer-Lambert law plot.
Mass Spectrometry (MS)
MS provides the molecular weight and fragmentation pattern. Electrospray ionization (ESI) or atmospheric pressure chemical ionization (APCI) are suitable methods. The molecular ion peak will correspond to the molecular weight of amoxicillin, allowing confirmation of the analyte’s identity. Fragmentation ions can further support structural elucidation.
