RATIONALE Accurate measurement of trace compounds in blood samples is important in clinical diagnosis and life science. Ambient ionization mass spectrometry, however, suffers from the matrix effect when dealing with complex samples such as blood. Therefore, it is important to reduce the matrix effects in blood samples. METHODS A low-cost and disposable Teflon tube was used as a platform to precipitate the protein in blood. The analytes are extracted into organic solvent, and the precipitated protein can be adsorbed by the chromatography paper inserted. Therefore, the Teflon tube after precipitation can be directly subjected to paper spray ionization mass spectrometry, achieving one-step analysis of blood. RESULTS High sensitivity and satisfactory stability were achieved for pharmaceuticals, acids, and endogenic metabolites in blood. The absolute signal intensities of characteristic product ions of the tested analytes were 8-20 times higher after protein precipitation than those obtained using paper spray. Detection limits and quantitative performance were evaluated for three drugs: carbamazepine, metformin, and tioconazole. In addition, the limits of detection and quantitation were improved 9-14- and 8-12-fold, respectively. CONCLUSIONS Protein precipitation coupled to paper spray with a tube and then to mass spectrometry was successfully achieved and applied in the one-step analysis of trace compounds in blood samples. The experimental results showed that this method was sensitive, stable, convenient, and economic for the direct analysis of blood.

中文翻译：

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蛋白质沉淀结合到带有管的纸喷雾器上，用于血液的一步分析。

理由准确测量血样中的微量化合物对临床诊断和生命科学至关重要。但是，环境电离质谱法在处理复杂样本（例如血液）时会受到基质效应的影响。因此，重要的是减少血液样本中的基质效应。方法使用廉价的一次性特氟隆管作为平台，使蛋白质在血液中沉淀。分析物被萃取到有机溶剂中，沉淀的蛋白质可以通过插入的色谱纸吸收。因此，沉淀后的特氟隆管可以直接进行纸喷雾电离质谱分析，实现血液的一步分析。结果对血液中的药物，酸和内源性代谢物实现了高灵敏度和令人满意的稳定性。蛋白质沉淀后，被测试分析物的特征产物离子的绝对信号强度比使用纸喷雾获得的信号强度高8-20倍。评价了三种药物的检测限和定量性能：卡马西平，二甲双胍和噻康唑。此外，检测限和定量限分别提高了9-14倍和8-12倍。结论成功地实现了蛋白质沉淀，然后再用试管进行纸喷雾再进行质谱分析，并将其用于血液样品中痕量化合物的一步分析。实验结果表明，该方法灵敏，稳定，方便，经济。