In a Tris-hydrochloric acid media of pH 5.48, rhodamine B reacted with aztreonam to form red binary ion association complexes, and the fading phenomenon occurred.Two obvious negative absorption peaks appeared on the spectral curve in the visible area.The maximum negative absorption peak was located at 512 nm, and the another negative absorption peak was located at 574 nm.At two wavelengths, the mass concentration of aztreonam in the range of 0 to 10.9 mg·L-1 showed a good linear relationship with the absorbance of the association complexes, and Lambert-Beer's law was obeyed.Their linear equation and the correlation coefficient were A512=-0.00016-0.03447 ρ, r=0.9998 and A574=0.00042-0.02006 ρ, r=0.9999, respectively.Their apparent molar absorptivity (κ) were 1.51×104 L·mol-1·cm-1 and 8.70 ×103 L·mol-1·cm-1, respectively.When the double wavelength superposition negative absorption spectrometry was used to determine the concentrations of aztreonam, and its linear equation was A512+574=0.00027-0.05453 ρ, the correlation coefficient r=0.9999.Its apparent molar absorptivity (κ) can be achieved 2.38×104 L·mol-1·cm-1.The method was applied to determine the content of aztreonam in commercially available aztreonam medicine with the satisfactory results.%在pH 5.48的Tris-盐酸介质中, 玫瑰精B与氨曲南反应生成红色二元离子缔合物, 出现褪色现象, 光谱曲线上出现2个明显的负吸收峰, 最大负吸收峰位于512 nm, 另一负吸收峰位于574 nm, 在此两波长处, 氨曲南在0～10.9 mg·L-1范围内与缔合物的吸光度呈线性关系, 并服从朗伯-比尔定律, 它们的线性方程和相关系数分别为A (512) =-0.00016-0.03447 ρ、r=0.9998和A574=0.00042-0.02006 ρ、r=0.9999, 表观摩尔吸光系数 (κ) 分别为1.51×104 L/ (mol·cm) 和8.70×103 L/ (mol·cm), 当用双波长叠加负吸收法测定时, 线性方程方程为A512+574=0.00027-0.05453ρ, 相关系数r=0.9999, 表观摩尔吸光系数κ可达2.38×104 L/ (mol·cm) .该法用于市售氨曲南药物中氨曲南含量的测定, 结果满意.
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