Riazanskaia S, Blackburn G, Harker M, Taylor D, Thomas C L P
The Centre for Instrumentation and Analytical Science at the School of Chemical Engineering and Analytical Science, The Faraday Tower, The University of Manchester, Sackville Street, Manchester, UKM60 1QD.
Analyst. 2008 Aug;133(8):1020-7. doi: 10.1039/b802515k. Epub 2008 May 20.
A thermally-desorbed polydimethylsilicone (PDMS) membrane approach with analysis by gas chromatography-mass spectrometry has been developed and characterised, to enable the VOC arising in, and on skin, from glandular secretions, exogenous materials, products of perfusion from blood, and microbiological metabolites to be sampled in a single procedure. In-vitro studies using a series of volatile fatty acid standards indicated that the recovery efficiency of the technique increased with decreasing volatility; for example, the recovery of hexanoic acid was 3.3 times greater than that for 2-methylpropanoic acid. The relative standard deviation of the methodology decreased with decreasing volatility; RSD = 19% for 2-methylpropanoic acid and RSD = 7% for hexanoic acid. Sampled-mass vs. response relationships were modelled satisfactorily using linear regression analysis with regression coefficients in the range 0.95 to 0.998. In-vivo reproducibility was assessed though the analysis of the responses of 1-dodecane, 3,7-dimethyloct-1-ene, 2-propenoic acid, 2-ethylhexyl ester, 2-ethylhexan-1-ol, butanoic, 2-ethylhexylester, and junipen (1,4-methanoazulene, decahydro-4,8,8-trimethyl-9-methylene-); six compounds selected at random retention times from a GC-MS chromatographic VOC profile of human skin containing several hundred resolved and partially resolved compounds. Five samples were obtained simultaneously from the forearm of a healthy male participant. The in-vivo sample masses were estimated to be in the range 50 pg to 100 ng per sample with observed RSD falling between 15% and 32%; in line with a Horwitz trend. Increasing the sample time from 5 min to 120 min generally resulted in an enrichment of the VOC recovered, and for many VOC substantial increases in sensitivity (x7) were observed over this time range as the PDMS sampling-patch approached equilibrium with the underlying skin. Nevertheless, more volatile components, 2,4,6-trimethylcarbazole for instance, were observed to be lost from the analysis with increasing sample time, in a manner analogous with breakthrough behaviour in adsorbent traps. Finally, a 10 day storage study at 4 degrees C suggested that micro-biological factors were significant in their effect on sample stability. Significant changes (up to x8) were observed in the masses of compounds recovered post storage. These studies confirmed that polydimethylsilicone membrane sampling patches of human skin provide rich and analytical useful data. It is important to note that care in experimental design is needed to avoid sampling artefacts being introduced through sampling selectivity, and/or, sample instability where samples are stored for longer than 24 h at 4 degrees C or higher.
已开发并表征了一种热脱附聚二甲基硅氧烷（PDMS）膜方法，并结合气相色谱 - 质谱分析，以便在单一程序中对皮肤内和皮肤表面由腺体分泌物、外源性物质、血液灌注产物以及微生物代谢产物产生的挥发性有机化合物（VOC）进行采样。使用一系列挥发性脂肪酸标准品进行的体外研究表明，该技术的回收率随挥发性降低而提高；例如，己酸的回收率比2 - 甲基丙酸高3.3倍。该方法的相对标准偏差随挥发性降低而减小；2 - 甲基丙酸的相对标准偏差为19%，己酸的相对标准偏差为7%。使用线性回归分析对采样质量与响应关系进行建模，回归系数范围为0.95至0.998，结果令人满意。通过分析1 - 十二烷、3,7 - 二甲基辛 - 1 - 烯、2 - 丙烯酸2 - 乙基己酯、2 - 乙基己醇、丁酸2 - 乙基己酯和刺柏烯（1,4 - 亚甲基薁，十氢 - 4,8,8 - 三甲基 - 9 - 亚甲基 -）的响应来评估体内重现性；这六种化合物是从包含数百种已分离和部分分离化合物的人体皮肤气相色谱 - 质谱VOC图谱中随机选择保留时间的。同时从一名健康男性参与者的前臂获取了五个样本。估计体内每个样本的质量范围为50 pg至100 ng，观察到的相对标准偏差在15%至32%之间；符合霍维茨趋势。将采样时间从5分钟增加到120分钟通常会使回收的VOC富集，并且在这个时间范围内，随着PDMS采样贴片与下层皮肤接近平衡，许多VOC的灵敏度大幅提高（高达7倍）。然而，观察到更易挥发的成分，例如2,4,6 - 三甲基咔唑，随着采样时间的增加会从分析中损失，其方式类似于吸附阱中的穿透行为。最后，在4℃下进行的10天储存研究表明，微生物因素对样品稳定性有显著影响。储存后回收的化合物质量出现了显著变化（高达8倍）。这些研究证实，人体皮肤的聚二甲基硅氧烷膜采样贴片可提供丰富且对分析有用的数据。需要注意的是，在实验设计中要小心，避免因采样选择性和/或样品在4℃或更高温度下储存超过24小时导致的样品不稳定性而引入采样假象。
