The concentration of target analyte in a mixture can be quantified by combining coulometric measurements with spray ionization mass spectrometry. A three‐electrode system screen printed on the polymer support acts both as the coulometry platform for electrochemical oxidation and the sample loading tip for spray ionization. After loading a droplet of the analyte solution onto the tip, two steps were taken to implement quantitation. First, the electrochemical oxidation potential was optimized with cyclic voltammetry followed by coulometric measurements to calculate the amount of oxidized analyte under a constant low voltage within a fixed period of time (5 s). Then, a high voltage (+4.5 kV) was applied to the tip to trigger spray ionization for measuring the oxidation yield from the native analyte ion and its oxidized product ion intensities by mass spectrometry. The analyte's native concentration is quantified by dividing the oxidized product's concentration (based on Coulomb's law) and the oxidation yield (estimated from mass spectrometry [MS] assuming that the parent and oxidation product have nearly the same ionization efficiencies). The workflow has an advantage in being free of any standard for constructing the quantitation curve. Several model compounds (tyrosine, dopamine, and angiotensin II) were selected for method validation. It was demonstrated that this strategy was feasible with an accuracy of ~15% for a wide coverage of different species including endogenous metabolites and peptides. As an example of its possible practical use, it was initially employed to make a bilirubin assay in urine.

中文翻译：

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电量分析法在喷雾电离质谱中的定量

混合物中目标分析物的浓度可以通过将库仑法测量值与喷雾电离质谱法结合起来进行定量。印在聚合物载体上的三电极系统丝网既用作电化学氧化的电量分析平台，又用作喷雾电离的样品加载尖端。将一滴分析物溶液装载到吸头上之后，需要执行两个步骤来进行定量。首先，先用循环伏安法优化电化学氧化电势，然后再进行电量分析法，以计算在固定时间段（5 s）内的恒定低压下的氧化分析物量。然后，高电压（+4。将5 kV）施加到尖端以触发喷雾电离，以通过质谱法测量天然分析物离子的氧化产率及其氧化产物离子强度。通过将氧化产物的浓度（基于库仑定律）和氧化产率（假设母体和氧化产物具有几乎相同的电离效率），将氧化产物的浓度（基于库仑定律）和氧化产率（根据质谱[MS]估算）相除，即可对分析物的自然浓度进行定量。该工作流程的优势在于无需任何用于构建定量曲线的标准。选择了几种模型化合物（酪氨酸，多巴胺和血管紧张素II）进行方法验证。事实证明，该策略对于包括内源性代谢物和肽在内的不同物种的广泛覆盖，准确性约为15％。