在10 mL比色管中，加入5.00×10^-4mol·L^-1三氯化铁溶液0.60 mL和适量的异烟肼样品溶液，微波加热2 min，冷却至室温后依次加入5.00×10^-3mol·L^-1碘化钾溶液1.00 mL、1.00×10^-4mol·L^-1十六烷基三甲基溴化铵溶液0.30 mL，用水稀释至10 mL，静置20 min后于荧光分光光度计上，在激发波长和发射波长均为275 nm处测量溶液的散射强度I，同时测量空白溶液的散射强度I₀，计算ΔI=I₀-I。异烟肼的质量浓度在0.050~0.25 mg·L^-1内与ΔI呈线性关系，检出限（3s/k）为0.015 mg·L^-1。方法应用于异烟肼片的分析，测定值与标示量相符，测定值的相对标准偏差（n=6）小于2.0%。

An appropriate amount of isoniazid sample solution and 0.60 mL of 5.00×10^-4mol·L^-1 ferric chloride solution were added into a 10 mL colorimetric tube. The tube was heating by microwave for 2 min, and cooled to room temperature. Then 1.00 mL of 5.00×10^-3mol·L^-1 potassium iodide solution was added and mixed well, 0.30 mL of 1.00×10^-4mol·L^-1 cetyltrimethylammonium bromide solution was added and mixed well. After the mixed solution was diluted to 10 mL with water, and allowed to stand for 20 min, the scattering intensity (I) of the solution was measured at both the excitation wavelength and the emission wavelength of 275 nm, using a fluorescence spectrophotometer. The scattering intensity (I₀) of the blank solution was measured, and ΔI=I₀-I was calculated. Linear relationship was found between ΔI and mass concentration of isoniazid in the range of 0.050-0.25 mg·L^-1, with detection limit (3s/k) of 0.015 mg·L^-1. The proposed method was applied to analysis of isoniazid tablets, giving measured values consistent with the labeled values, and RSDs (n=6) less than 2.0%.