Abstract

An automated sequential injection analysis with spectrometric detection for the determination of trimethoprim and sulfamethoxazole in tablets is proposed. The concentration of sulfamethoxazole is determined by monitoring the absorbance at 540 nm due to the intensively colored complex formed by derivatization reaction of sulfamethoxazole with nitrite and N-(1-naphthyl)ethylenediamine in acidic media. With knowledge of the sulfamethoxazole concentration, the trimethoprim concentration can be calculated from the absorption of the sample solution at 264 nm, where both analytes absorb, and the additivity of individual absorbances according to Beer-Lambert law can be used. The developed method has a linear dynamic range of 0.03–5.0 mg dm⁻³ and a detection limit of 0.03 mg dm⁻³ for trimethoprim and a linear dynamic range of 0.1–10.0 mg dm⁻³ and a detection limit of 0.01 mg dm⁻³ for sulfamethoxazole. The sampling frequency of the method is 24 h⁻¹. The method was successfully applied on pharmaceutical dosage form of tablets, as the results of the determination are in a good agreement with the official pharmacopoeial method (HPLC). The developed sequential injection analysis is simpler, cheaper, and faster than already published methods and pharmacopoeial assay. So it appears to be suitable for quality control in the pharmaceutical industry.

Graphic abstract

中文翻译：

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序贯自动进样光度法测定片剂中的甲氧苄啶和磺胺甲恶唑

摘要

提出了一种采用光谱检测的自动顺序注射分析法测定片剂中甲氧苄啶和磺胺甲恶唑的方法。磺胺甲恶唑的浓度是通过监测540 nm处的吸光度来确定的，这是由于磺胺甲恶唑与亚硝酸盐和N-（1-萘基）乙二胺在酸性介质中衍生化反应而形成的强烈着色的络合物。了解了磺胺甲恶唑的浓度后，可以从样品溶液在264 nm处的吸收（其中两种分析物都吸收）来计算甲氧苄啶的浓度，并且可以使用根据比尔-兰伯特定律的各个吸收度的加和性。所开发的方法的线性动态范围为0.03–5.0 mg dm ^-3，检出限为0.03 mg dm ^-3对于甲氧苄啶，线性动态范围为0.1–10.0 mg dm ^-3，对磺胺甲恶唑的检出限为0.01 mg dm ^-3。该方法的采样频率为24 h ^-1。该方法已成功应用于片剂的药物剂型，因为测定结果与官方药典方法（HPLC）吻合良好。相较于已发表的方法和药典测定法，已开发的顺序注射分析法更简单，更便宜且更快捷。因此，它似乎适用于制药行业的质量控制。

图形摘要