A rapid in situ analytical method was developed for the detection of generated carcinogenic aromatic amines from banned azo dyes utilizing a photocatalytic reduction-based liquid microjunction surface sampling (LMJSS)–mass spectrometry (MS) system. We utilized photocatalytic reduction under UV irradiation with TiO₂ as catalyst to have rapid and mild reduction of azo dyes. The reaction conditions were optimized to have complete photocatalytic reduction within 2–5 min in pure methanol at room temperature. TiO₂ was immobilized in the inner wall of the capillaries in the LMJSS system to achieve in situ sampling–online rapid reduction–MS detection for aromatic amines originating from azo dyes in packaging surface. The yields of in-tube photocatalytic reduction were near 100% by delivering the azo dye extracts through the capillary at 1 μL/min under UV irradiation. With this design, in situ analysis was completed within 2 min via direct MS detection and 7 min via liquid chromatography (LC)–MS detection. The detection limits for five aromatic amines originating from four different azo dyes were in the range of 1–17 mg/kg with relative standard deviations (RSDs) < 8.5%. In the application of the new method, four carcinogenic aromatic amines were detected and identified in three commercial packaging materials, and the quantitation results were comparable with those obtained by the conventional chemical reduction–LC–MS method (relative recovery, 81–121%). Moreover, due to the spatial resolution of the present method with a flow probe, MS imaging was achieved demonstrating clear azo dye patterns of a lab-made sample.

Graphical abstract

中文翻译：

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基于光催化还原的液体微结表面采样-质谱法快速原位分析源自包装纸中偶氮染料的芳香胺

开发了一种快速原位分析方法，用于利用基于光催化还原的液体微结表面采样 (LMJSS)-质谱 (MS) 系统检测禁用的偶氮染料中产生的致癌芳香胺。我们利用 TiO ₂作为催化剂在紫外线照射下进行光催化还原，以快速温和地还原偶氮染料。优化反应条件，在室温下在纯甲醇中 2-5 分钟内完成光催化还原。将TiO ₂固定在LMJSS系统毛细管内壁，实现原位采样——在线快速还原——包装表面偶氮染料中芳香胺的质谱检测。通过在紫外线照射下以 1 μL/min 的速度通过毛细管输送偶氮染料提取物，管内光催化还原的产率接近 100%。通过这种设计，通过直接 MS 检测在 2 分钟内完成原位分析，通过液相色谱 (LC) – MS 检测在7 分钟内完成。来自四种不同偶氮染料的五种芳香胺的检测限在 1 – 17 mg/kg范围内，相对标准偏差 (RSD) < 8.5%。在新方法的应用中，对三种商品包装材料中的四种致癌芳香胺进行了检测和鉴定，定量结果与常规化学还原得到的定量结果相当– LC – MS 方法（相对回收率，81–121%）。此外，由于本方法的空间分辨率与流量探头，实现了 MS 成像，展示了实验室制造样品的清晰偶氮染料图案。

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