The growing use of fluorochemicals has elevated the need for nontargeted detection of unknown fluorinated compounds and transformation products. Elemental mass spectrometry (MS) coupled to chromatography offers a facile approach for such analyses by using fluorine as an elemental tag. However, efficient ionization of fluorine has been an ongoing challenge. Here, we demonstrate a novel atmospheric-pressure elemental ionization method where fluorinated compounds separated by gas chromatography (GC) are converted to Na₂F⁺ for nontargeted detection. The compounds are first introduced into a helium dielectric barrier discharge (DBD) for breakdown. The plasma products are subsequently ionized by interaction with a nanoelectrospray ionization (nano-ESI) plume of sodium-containing aqueous electrolytes. Our studies point to HF as the main plasma product contributing to Na₂F⁺ formation. Moreover, the results reveal that Na₂F⁺ is largely formed by the ion-neutral reaction between HF and Na₂A(NaA)_n⁺, gas-phase reagent ions produced by nano-ESI where A represents the anion of the electrolyte. Near-uniform fluorine response factors are obtained for a wide range of compounds, highlighting good efficiency of HF formation by DBD regardless of the chemical structure of the compounds. Detection limits of 3.5–19.4 pg of fluorine on-column are obtained using the reported GC–DBD–nano-ESI-MS. As an example of nontargeted screening, extractions from oil-and-water-repellent fabrics are analyzed via monitoring Na₂F⁺, resulting in detection of a fluorinated compound on a clothing item. Notably, facile switching of the ion source to atmospheric-pressure chemical ionization with the exact same chromatographic method allows identification of the detected compound at the flagged retention time.

中文翻译：

---

介电势垒放电与纳米电喷雾电离质谱耦合的元素氟检测，用于非目标分析氟化化合物。

含氟化合物的日益增长的使用增加了对非目标检测未知氟化化合物和转化产物的需求。元素色谱法（MS）与色谱法结合使用氟作为元素标记，为此类分析提供了一种简便的方法。然而，氟的有效电离一直是挑战。在这里，我们演示了一种新颖的常压元素电离方法，该方法将通过气相色谱（GC）分离的氟化化合物转化为Na ₂ F ⁺用于非目标检测。首先将这些化合物引入氦介电势垒放电（DBD）中进行击穿。随后，通过与含钠的水性电解质的纳米电喷雾电离（nano-ESI）羽流相互作用，使等离子体产物电离。我们的研究指出，HF是导致Na ₂ F ⁺形成的主要血浆产物。此外，结果表明，Na ₂ F ⁺在很大程度上是由HF和Na ₂ A（NaA）_n ⁺之间的离子中性反应形成的，由纳米ESI产生的气相反应离子，其中A代表电解质的阴离子。对于广泛的化合物，获得了几乎一致的氟响应因子，这突出了通过DBD形成HF的良好效率，而与化合物的化学结构无关。使用已报道的GC–DBD–nano-ESI-MS获得了柱上氟的检出限为3.5–19.4 pg。作为非针对性筛选的一个例子，通过监测Na ₂ F ⁺分析了拒油拒水织物的提取物，从而检测到了服装上的氟化化合物。值得注意的是，通过使用完全相同的色谱方法，将离子源轻松转换为大气压化学电离，可以在标记的保留时间识别检测到的化合物。