Cordero Chiara, Rubiolo Patrizia, Sgorbini Barbara, Galli Mario, Bicchi Carlo
Dipartimento di Scienza e Tecnologia del Farmaco, Università degli Studi di Torino, via P. Giuria 9, I-10125 Torino, Italy.
J Chromatogr A. 2006 Nov 3;1132(1-2):268-79. doi: 10.1016/j.chroma.2006.07.067. Epub 2006 Aug 21.
The study evaluates the influence of selectivity tuning of the stationary phase of the second dimension on the orthogonality of a comprehensive two-dimensional gas chromatography (GC x GC) system. Two different sets of columns, providing independent and semi-independent separation mechanisms were used. The first consisted of a first dimension separating analytes on a volatility basis (i.e. a non-polar polydimethylsiloxane (OV1) column) combined with a second dimension separating by polarity, using columns coated with 100% polyethylene glycol (CW20M), CW20M/OV1 mixtures in ratios of 25-75%, and polydimethylsiloxane, 7% phenyl, 7% cyanopropyl (OV1701). The second set consisted of a first dimension separating analytes on a polarity basis (100% CW20M column) combined with a second dimension separating by volatility, consisting of columns coated with 100% OV1, OV1/CW20M mixtures in ratios of 25-75%, and 100% OV1701. Medium-complexity mixtures of natural origin (i.e. peppermint essential oil and a standard mixture of suspected allergens) consisting of components in a relatively limited range of molecular weights (MW) and volatilities, but belonging to different classes of compounds in a wide range of polarity (mono- and sesquiterpenoids, hydrocarbons and oxygenated compounds) were analysed with the above sets of columns. Different approaches were used to evaluate peak spreading on the GC x GC separation plane and degree of orthogonality of the column sets, namely: (1) a Factor Analysis (FA) approach, estimating the correlation coefficients and spreading angles of the sample components in the two-dimensional chromatographic plane; (2) an Informational Theory (IT) approach, based on determining a group of parameters including: informational entropy, % synentropy and similarity (H); and (3) an approach based on estimating the amount of separation space used, i.e. a practical parameter that directly refers to the experimental separation plane of the GC x GC chromatogram. Results showed that peak spreading in the chromatographic plane, when CW20M and OV1 are combined in different ratios, can be predicted from retention mechanisms, and that the degree of orthogonality measured with different approaches, is consistent with the divergent nature, in terms of polarity of the stationary phases combined in the GC x GC system.
该研究评估了二维气相色谱（GC×GC）系统中第二维度固定相的选择性调谐对其正交性的影响。使用了两组不同的色谱柱，它们提供独立和半独立的分离机制。第一组由第一维度基于挥发性分离分析物（即非极性聚二甲基硅氧烷（OV1）柱）与第二维度基于极性分离组成，使用涂覆有100%聚乙二醇（CW20M）、比例为25 - 75%的CW20M/OV1混合物以及7%苯基、7%氰丙基聚二甲基硅氧烷（OV1701）的色谱柱。第二组由第一维度基于极性分离分析物（100% CW20M柱）与第二维度基于挥发性分离组成，由涂覆有100% OV1、比例为25 - 75%的OV1/CW20M混合物以及100% OV1701的色谱柱组成。分析了天然来源的中等复杂度混合物（即薄荷精油和可疑过敏原标准混合物），其由分子量（MW）和挥发性相对有限范围内的成分组成，但属于极性范围广泛的不同类化合物（单萜和倍半萜、烃类和含氧化合物）。使用上述色谱柱组采用不同方法评估了GC×GC分离平面上的峰展宽和色谱柱组的正交度，即：（1）因子分析（FA）方法，估计二维色谱平面中样品成分的相关系数和展宽角；（2）信息理论（IT）方法，基于确定一组参数，包括：信息熵、%同步熵和相似度（H）；以及（3）基于估计所用分离空间量的方法，即一个直接涉及GC×GC色谱图实验分离平面的实际参数。结果表明，当CW20M和OV1以不同比例组合时，色谱平面中的峰展宽可根据保留机制进行预测，并且用不同方法测量的正交度与GC×GC系统中组合的固定相在极性方面的不同性质一致。
