Background. Volatile acetone is a potential biomarker that is elevated in various disease states. Measuring acetone in exhaled breath is complicated by the fact that the molecule might be present as both monomers and dimers, but in inconsistent ratios. Ignoring the molecular form leads to incorrect measured concentrations. Our first goal was to evaluate the monomer-dimer ratio in ambient air, critically ill patients, and rats. Our second goal was to confirm the accuracy of the combined (monomer and dimer) analysis by comparison to a reference calibration system. Methods. Volatile acetone intensities from exhaled air of ten intubated, critically ill patients, and ten ventilated Sprague-Dawley rats were recorded using ion-mobility spectrometry. Acetone concentrations in ambient air in an intensive care unit and in a laboratory were determined over 24 hours. The calibration reference was pure acetone vaporized by a gas generator at concentrations from 5 to 45 ppb_v (parts per billion by volume). Results. Acetone concentrations in ambient laboratory air were only slightly greater (5.6 ppb_v; 95% CI 5.1–6.2) than in ambient air in an intensive care unit (5.1 ppb_v; 95% CI 4.4–5.5; ). Exhaled acetone concentrations were only slightly greater in rats (10.3 ppb_v; 95% CI 9.7–10.9) than in critically ill patients (9.5 ppb_v; 95% CI 7.9–11.1; ). Vaporization yielded acetone monomers (1.3–5.3 mV) and dimers (1.4–621 mV). Acetone concentrations (ppb_v) and corresponding acetone monomer and dimer intensities (mV) revealed a high coefficient of determination (R² = 0.96). The calibration curve for acetone concentration (ppb_v) and total acetone (monomers added to twice the dimers; mV) was described by the exponential growth 3-parameter model, with an R² = 0.98. Conclusion. The ratio of acetone monomer and dimer is inconsistent and varies in ambient air from place-to-place and across individual humans and rats. Monomers and dimers must therefore be considered when quantifying acetone. Combining the two accurately assesses total volatile acetone.

中文翻译：

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使用离子迁移谱法对挥发性丙酮低聚物进行定量

背景。挥发性丙酮是一种潜在的生物标志物，在各种疾病状态下都会升高。测量呼出气中的丙酮是复杂的，因为分子可能以单体和二聚体的形式存在，但比例不一致。忽略分子形式会导致不正确的测量浓度。我们的第一个目标是评估环境空气、重症患者和大鼠中的单体二聚体比例。我们的第二个目标是通过与参考校准系统进行比较来确认组合（单体和二聚体）分析的准确性。方法. 使用离子迁移光谱法记录了 10 只插管、危重病人和 10 只通气的 Sprague-Dawley 大鼠呼出空气中的挥发性丙酮强度。在 24 小时内测定重症监护室和实验室环境空气中的丙酮浓度。校准参考是由气体发生器蒸发的纯丙酮，浓度为 5 至 45 ppb _v（十亿分之一体积）。结果。实验室环境空气中的丙酮浓度（5.6 ppb _v；95% CI 5.1–6.2）仅略高于重症监护病房环境空气中的丙酮浓度（5.1 ppb _v；95% CI 4.4–5.5；）。大鼠呼出的丙酮浓度（10.3 ppb _v；95% CI 9.7–10.9）仅略高于危重患者（9.5 ppb _v；95% CI 7.9–11.1；）。蒸发产生丙酮单体 (1.3–5.3 mV) 和二聚体 (1.4–621 mV)。丙酮浓度 (ppb _v ) 和相应的丙酮单体和二聚体强度 (mV) 显示出较高的决定系数 ( R ²  = 0.96)。_{丙酮浓度 (ppb v} ) 和总丙酮（单体添加到二聚体的两倍；mV）的校准曲线由指数增长 3 参数模型描述， R ²  = 0.98。结论. 丙酮单体和二聚体的比例是不一致的，并且在环境空气中因地而异，并且因人和大鼠的个体而异。因此，在量化丙酮时必须考虑单体和二聚体。将两者结合可准确评估总挥发性丙酮。