Centre for Analytical Science, Department of Chemistry, Loughborough University, Loughborough, Leicestershire, LE11 3TU, UK.
Analyst. 2012 Aug 21;137(16):3627-34. doi: 10.1039/c2an35432b. Epub 2012 Jul 4.
Evaluation of published methods reveals that existing methods for saliva sampling do not address the physical-chemical attributes of volatile organic compounds (VOCs). This study describes and presents evidence for adopting in situ sampling of salivary VOCs directly from the oral cavity using a polydimethylsiloxane (PDMS) based sampler. In vitro studies indicated that the vapour pressure of analytes was a factor in both the recovery of analytes and the precision of the recovery. The highest recoveries were observed for VOCs with the lowest vapour pressures, for example 5-nonanol (vapour pressure (P(v)) = 14 Pa) recoveries were approximately 20 times greater than those observed for octane (P(v) = 1726 Pa). Similarly, relative standard deviations reduced with vapour pressure, with the RSD for 5-nonanol responses observed to be 2.7% when compared to RSD = 26% for octane. Evaluation of VOCs recovered from 6 in vivo samples indicated that VOC concentrations in saliva may follow log-normal distributions; log-normal RSDs falling between 4.4% and 18.2% across the range of volatilities encountered. Increasing sampling time from 1 to 30 minutes indicated that the recovery of VOC into the sampler was affected by interaction between different physical-chemical properties and biogenic flux. A sampling time of 10 min was found to offer an acceptable compromise that enabled a representative sample to be acquired for the widest range of observed VOC behaviours with the sampler. The potential to 'tune' the sampling protocol for targeted analysis based on these factors was also noted. Comparison with passive drool saliva collection revealed up to 10(5) enhancement with reduced variability compared to drooled samples. This approach to in situ saliva sampling appears to have significant analytical utility for studying volatile signatures in humans.
评估已发表的方法表明，现有的唾液采样方法并不能解决挥发性有机化合物（VOCs）的物理化学性质。本研究描述并提出了一种采用基于聚二甲基硅氧烷（PDMS）的采样器直接从口腔中采集唾液 VOCs 的方法，并提供了相关证据。体外研究表明，分析物的蒸气压是影响分析物回收率和回收率精密度的因素。蒸气压最低的 VOCs 的回收率最高，例如，5-壬醇（蒸气压（P(v)）= 14 Pa）的回收率大约是辛烷（P(v) = 1726 Pa）的 20 倍。同样，相对标准偏差随蒸气压降低而降低，与辛烷相比，5-壬醇响应的 RSD 为 2.7%，而 RSD = 26%。对 6 个体内样本中回收的 VOCs 的评估表明，唾液中的 VOC 浓度可能遵循对数正态分布；在遇到的挥发性范围内，对数正态 RSD 介于 4.4%和 18.2%之间。从 1 分钟增加到 30 分钟的采样时间表明，VOC 进入采样器的回收率受到不同物理化学性质和生物通量之间相互作用的影响。发现采样时间为 10 分钟是一个可以接受的折衷方案，该方案可以在采样器上获得最广泛的观察到的 VOC 行为的代表性样本。还注意到，根据这些因素，可以对采样方案进行“调整”，以便进行有针对性的分析。与被动流涎唾液采集的比较表明，与流涎样本相比，该方法的增强倍数高达 10(5)，且变异性降低。这种原位唾液采样方法似乎在研究人类挥发性特征方面具有重要的分析应用价值。
