Enhanced resolution of Mentha piperita volatile fraction using a novel medium-polarity ionic liquid gas chromatography stationary phase.

The evaluation of a novel medium-polarity ionic-liquid-based gas chromatography column, SLB-IL60, towards the analysis of a complex essential oil, namely, a peppermint essential oil sample, is reported. The SLB-IL60 30 m column was subjected to bleeding measurements, by means of conventional gas chromatography with mass spectrometry. The SLB-IL60 column was then evaluated in the analysis of pure standard compounds, chosen as typical constituents of peppermint essential oil. Resolution and peak symmetry (expressed as tailing factors at 10% of peak height) were measured and the results were compared to those obtained on the most widely used columns in such an application, namely a medium-polarity [100% poly(ethyleneglycol)] stationary phase, and an apolar 5% diphenyl/95% dimethyl siloxane. The final part of the evaluation was dedicated to the gas chromatography with mass spectrometry analysis of a peppermint essential oil sample and again the data were compared to those obtained on the 100% poly(ethyleneglycol) and the 5% diphenyl/95% dimethyl siloxane phase. Linear retention indices were determined for all the identified components on the ionic liquid capillary.

Performance evaluation of a versatile multidimensional chromatographic preparative system based on three-dimensional gas chromatography and liquid chromatography-two-dimensional gas chromatography for the collection of volatile constituents.

The present research deals with the multi-collection of the most important sesquiterpene alcohols belonging to sandalwood essential oil, as reported by the international regulations: (Z)-α-santalol, (Z)-α-trans bergamotol, (Z)-ß-santalol, epi-(Z)-ß-santalol, α-bisabolol, (Z)-lanceol, and (Z)-nuciferol. A versatile multidimensional preparative system, based on the hyphenation of liquid and gas chromatography techniques, was operated in the LC-GC-GC-prep or GC-GC-GC-prep configuration, depending on the concentration to be collected from the sample, without any hardware or software modification. The system was equipped with a silica LC column in combination with polyethylene glycol-poly(5% diphenyl/95% dimethylsiloxane)-medium polarity ionic liquid or ß-cyclodextrin based GC stationary phases. The GC-GC-GC-prep configuration was exploited for the collection of four components, by using a conventional split/splitless injector, while the LC-GC-GC-prep approach was applied for three low abundant components (<5%), in order to increase the quantity collected within a single run, by the LC injection of a high sample amount. All target compounds, whose determination is hampered by the unavailability of commercial standards, were collected at milligram levels and with a high degree of purity (>87%).

Characterisation of lipid fraction of marine macroalgae by means of chromatography techniques coupled to mass spectrometry.

In this work the characterisation of the lipid fraction of several species of marine macro algae gathered along the eastern coast of Sicily is reported. Two species of green marine algae (Chloropyceae), two species of red marine algae (Rhodophyceae) and four species of brown marine algae (Pheophyceae) were evaluated in terms of fatty acids, triacylglycerols, pigments and phospholipids profile. Advanced analytical techniques were employed to fully characterise the lipid profile of these Mediterranean seaweeds, such as GC-MS coupled to a novel mass spectra database supported by the simultaneous use of linear retention index (LRI) for the identification of fatty acid profile; LC-MS was employed for the identification of triacylglycerols (TAGs), carotenoids and phospholipids; the determination of accurate mass was carried out on carotenoids and phospholipids. Quantitative data are reported on fatty acids and triacylglycerols as relative percentage of total fraction.

Profiling and quantifying polar lipids in milk by hydrophilic interaction liquid chromatography coupled with evaporative light-scattering and mass spectrometry detection.

In this work, a high-performance liquid chromatography with evaporative light scattering detection method has been developed and applied for quantification of the polar content of the lipid fraction in milk samples of different origin. From a chromatographic stand-point, a 4.6-mm I.D. hydrophilic interaction liquid chromatography column was employed to attain a baseline separation of major phospholipid classes contained in the various milk samples tested. Quantitative analysis was performed by the external calibration method using reference material solutions in the 5-100 mg/L concentration range. Analytical recoveries ranging from 57 to 100%, and repeatability data lower than 8.04% were obtained on a skimmed cow's milk sample. The crude cow milk was the most abundant (0.04%) in phospholipids and donkey milk was the poorest (0.004%). Quantitative differences were determined in the phospholipid content of the milk samples tested. Finally, characterization of phospholipid profile and fatty acid composition of the different samples was carried out by an ion trap-time of flight mass spectrometer and gas chromatography coupled to flame ionization and mass spectrometry detection. A thorough screening of the polar lipid composition of milk samples of different origin is here outlined, for the first time.

Increasing the isolated quantities and purities of volatile compounds by using a triple Deans-switch multidimensional preparative gas chromatographic system with an apolar-wax-ionic liquid stationary-phase combination.

A novel preparative-scale triple gas chromatographic system, equipped with three Deans-switch devices, is herein described. The isolation of volatile compounds was achieved by using a lab-made collection system. Considerations are made on the possibility to inject high volumes of neat sample, maintaining, at the same time, high resolution levels. The degree of recovery of a series of compounds, characterized by a differing volatility, is also reported. In this respect, different collection conditions were evaluated, namely, the presence (or not) of packing material as well as CO(2) cooling, in various combinations. Finally, the interconnected features, that is time requirements and the isolation of "acceptable" analyte quantities (e.g., milligram level for NMR characterization), are related to parameters such as analyte concentration, injected volume, collection conditions, and number of GC runs. The results herein reported will demonstrate the need for a high-resolution GC step, prior to analyte collection, in the prep-GC analysis of complex samples.

Use of ionic liquids as stationary phases in hyphenated gas chromatography techniques.

In the past decades a consistent number of ionic liquids have been specifically synthesized and evaluated as stationary phase in gas chromatography. Ionic liquid, also defined as "molten salts", are a class of organic non-molecular solvents liquid at room temperature (RTILs) that satisfy most of the requirements of a GC stationary phase, among which a high viscosity, the possibility to tune the selectivity (by changing the cation-anion combination) and a high thermal stability. The choice of the proper stationary phase plays a key role in the improvement/optimization of a GC method, and although the use of IL as stationary phases is still not well-established, the general interest in their applications has greatly increased, thanks to their particular properties. The present contribution provides an overview on recent evaluations and applications of IL stationary phases, focusing in particular on the use of these novel tools in hyphenated GC-based techniques.

Evaluation of a medium-polarity ionic liquid stationary phase in the analysis of flavor and fragrance compounds.

The present research is focused on the evaluation, in terms of efficiency and polarity, of a recently introduced gas chromatography (GC) column, coated with a 1,12-di(tripropylphosphonium) dodecane bis(trifluoromethansulfonyl) amide ionic-liquid stationary phase (SLB-IL59) and its application to the analysis of a complex essential oil. The ionic liquid column demonstrated very good efficiency, in terms of plate number, and a polarity close to that of the 100% poly(ethyleneglycol) stationary phase. In this preliminary evaluation, the SLB-IL59 30 m column was subjected to bleeding measurements, by means of conventional gas chromatography/mass spectrometry (GC/MS) and, in addition, of comprehensive 2D GC. The SLB-IL59 column (30 m × 0.20 µm d(f), 0.25 mm i.d.) was then evaluated in the analysis of typical essential oil constituents, in the form of pure standard compounds. Resolution toward several analytes was measured and the results were compared to those obtained with both apolar [silphenylene polymer, equivalent to poly(5% diphenyl/95% dimethylsiloxane)] and medium-polarity [100% poly(ethyleneglycol)] stationary phases, namely, the most common columns employed in the analysis of essential oils; peak symmetry, for different essential oil constituents, was also measured and expressed through tailing factors (at 10% of peak height). The final part of the investigation was devoted to the GC/MS analysis of lemon essential oil, with GC-flame ionization detection (FID) used for quantification. Linear retention indices of all the identified compounds were determined, and the data obtained were compared to those attained on the apolar and "wax" columns. The results obtained in the present investigation reveal the great potential of this novel stationary phase, as a medium-polarity alternative, in the analysis of essential oils.

Application of a multidimensional gas chromatography system with simultaneous mass spectrometric and flame ionization detection to the analysis of sandalwood oil.

The production and trade of Indian sandalwood oil is strictly regulated, due to the impoverishment of the plantations; for such a reason, Australian sandalwood oil has been evaluated as a possible substitute of the Indian type. International directives report, for both the genuine essential oils, specific ranges for the sesquiterpene alcohols (santalols). In the present investigation, a multidimensional gas chromatographic system (MDGC), equipped with simultaneous flame ionization and mass spectrometric detection (FID/MS), has been successfully applied to the analysis of a series of sandalwood oils of different origin. A detailed description of the system utilized is reported. Three santalol isomers, (Z)-α-trans-bergamotol, (E,E)-farnesol, (Z)-nuciferol, epi-α-bisabolol and (Z)-lanceol have been quantified. LoD (MS) and LoQ (FID) values were determined for (E,E)-farnesol, used as representative of the oxygenated sesquiterpenic group, showing levels equal to 0.002% and 0.003%, respectively. A great advantage of the instrumental configuration herein discussed, is represented by the fact that identification and quantitation of target analytes are carried out in one step, without the need to perform two separate analyses.

Sicilian lemon oil: Composition of volatile and oxygen heterocyclic fractions and enantiomeric distribution of volatile components.

A total of 92 samples of Sicilian lemon oils (Citrus limon (L.) Burm. f.) produced from September 2008 to June 2009, industrially cold-pressed by different extraction techniques (Brown Oil Extractor and Food Machinery Corporation), were analyzed by GC-flame ionization detector (FID) and GC/MS-LRI to investigate the volatile fraction; by RP-HPLC/PDA to determine the non-volatile components and by enantio-GC-FID to determine the enantiomeric ratios of 12 volatile components. This study provides a detailed investigation on the composition of Sicilian lemon essential oils industrially produced during a productive season, with the aim to recognize quality parameters for the characterization of this product. The results obtained are discussed to evaluate seasonal variation, influence of the extraction techniques, and are compared with those obtained for samples produced during different seasons.

Evaluation of tea tree oil quality and ascaridole: a deep study by means of chiral and multi heart-cuts multidimensional gas chromatography system coupled to mass spectrometry detection.

The natural-like assessment of essential oils is a demanding task due to the growing trend toward adulterations. Usually chiral chromatography was used for this purpose due to the capability of assessing stereospecificity which is directly related to the enzymatic pathways of each plant species. On the other hand, the quality of an essential oil involves also the evaluation of its oxidative state, mainly connected with the age and storage conditions. In fact, some modifications in the chemical profile of the oil can occur if not properly preserved. Alterations of the components due to oxidative reactions lead to the formation of peroxides, endoperoxides and epoxides, such as ascaridole and 1,2,4-trihydroxymenthane, usually present in very low amount, formed by the oxidation of terpinen-4-ol and α-terpinene, respectively. Therefore, in the present research, the quality of Australian Tea Tree oil (Melaleuca alternifolia (Maiden & Betche) Cheel, Myrtaceae) was investigated by means of a multi heart-cut multidimensional gas chromatographic system coupled to a mass spectrometer detector and by conventional enantio-GC. The MDGC system allowed the complete separation of the compounds of interest transferred from the first column to a second dimension based on a different separation mechanism. The MS detector at the end of the second column provided the identification of the peaks with high similarity values because of their high purities after the multidimensional separation. Method validation was carried out, in order to use this procedure for routine application, monitoring the repeatability of 1D retention times and 2D peak areas, LoD and LoQ. Finally, enantiomeric ratios for chiral compounds were established to support quality data obtained.

Evaluation of a rapid-scanning quadrupole mass spectrometer in an apolar × ionic-liquid comprehensive two-dimensional gas chromatography system.

Comprehensive two-dimensional gas chromatography (GC×GC) is a powerful technique which can enable a great increase in GC peak capacities. However, since secondary-column separations are very rapid, detectors with a fast acquisition rate are mandatory. Such a requirement has certainly limited the use of the quadrupole mass spectrometer in the GC×GC field. The present research is focused on the evaluation of a novel rapid-scanning quadrupole mass spectrometry (qMS) detector, characterized by a 20,000 amu/s scan speed and a 50 Hz scan frequency, using a 290 amu mass range (40-330 m/z). The performance of the MS system was assessed by analyzing mixtures of 24 allergens, as well as a perfume sample, through GC×GC/qMS. The MS parameters evaluated at different acquisition rates (50, 33, and 25 Hz), as well as in the (simultaneous) scan/selected ion monitoring (SIM) mode, were the number of data points per peak, mass spectrum quality, peak skewing, and sensitivity. Two GC×GC/qMS methods, using the 50 Hz acquisition rate and the scan/SIM mode, were validated. Both methods provided similar results in terms of repeatability, accuracy, and linearity, while a great increase in sensitivity was observed (ca. a factor of 10) under scan/SIM conditions. The validated method proved to be suitable for the analysis of perfume allergens, according to the requirements of Directive 2003/15/EC.

Multidimensional GC coupled to MS for the simultaneous determination of oxygenate compounds and BTEX in gasoline.

In the present work, carried out in relation to the European and American Directives on the quality of petrol and diesel fuels, the simultaneous determination of the oxygenate compounds and BTEX in gasoline was achieved through the use of a multidimensional GC (MDGC)/MS system, employing a Deans switch-based transfer system, with an innovative configuration; the latter enabled multiple heart-cut transfers with no hint of retention time shift, a phenomenon that can occur in MDGC, providing the possibility to achieve more then 20 different heart-cuts for the compounds of interest. In this study, 20 selected compounds were quantitatively transferred with 12 heart-cuts, from a first to a secondary column, in order to resolve primary column co-elutions. Analyte quantification and identification was achieved through a fast-scanning quadrupole mass analyzer, operated in full scan mode, in order to evaluate also the interfering compounds transferred together with the compounds of interest. The multidimensional method developed was subjected to validation. All attained data were in excellent correlation with results obtained through the UNI-EN 12177:2000, ASTM D 5580-02 and ASTM D 4815-04 MDGC methods, for the determination of benzene, BTEX and oxygenate compounds in gasoline, respectively.

Thorough evaluation of the validity of conventional enantio-gas chromatography in the analysis of volatile chiral compounds in mandarin essential oil: A comparative investigation with multidimensional gas chromatography.

The present research is focused on the determination of the enantiomeric distribution of chiral compounds, contained in mandarin essential oils, by means of conventional chiral gas chromatography with flame ionization detection (enantio-GC-FID); the results attained were compared with those derived from heart-cutting multidimensional GC-mass spectrometry (MDGC/MS), to evaluate the reliability of the monodimensional technique as a tool for quality control. The Deans-switch MDGC system was equipped with two GC ovens, which were connected via a heated transfer line, a flame ionization detector (FID1) in the first dimension and a quadrupole MS as second-dimension detector. The a priori knowledge of potential co-elutions concerning target compounds (an enantiomer and an interfering compound), when using enantio-GC-FID, could enable the use of corrected enantiomer excess values. Correction factors could be calculated through a preliminary GC-FID analysis (using an apolar column), considering the peak areas of the known interferences. The method used for the calculation of a so-called "coelution correction factor" is described, along with some examples.

Conventional and fast gas chromatography analysis of biodiesel blends using an ionic liquid stationary phase.

The present research is focused on the GC-FID determination of fatty acid methyl esters (FAMEs) in diesel blends, by means of an ionic liquid stationary phase, characterized by a dicationic 1,9-di(3-vinyl-imidazolium)nonane bis(trifluoromethyl)sulfonylimidate structure (SLB-IL100). The high polarity of the ionic liquid stationary phase allowed the separation of the FAMEs, from the less-retained hydrocarbons, thus avoiding the requirement of a hydrocarbon LC pre-separation. The results derived from the analyses of a soybean FAMEs B20 sample, carried out on an SLB-IL100 conventional column (30 m x 0.25 mm i.d. x 0.20 mm d(f)), were compared with those attained on a polyethylene glycol column, of equivalent dimensions. Conventional and fast GC methods, for the analysis of FAMEs in diesel blends, were developed on an SLB-IL100 30 m x 0.25 mm i.d. x 0.20 microm d(f) and on an SLB-IL100 12 m x 0.10 mm i.d. x 0.08 microm d(f) column, respectively. The optimized IL methods were subjected to validation: retention time and peak area intra-day precision (n=5) were good, with CV % values lower than 0.08% and 4.9%, respectively. With regards to the quantitation of FAMEs in biodiesel blends, a five points calibration curve was constructed, using C(17:0) as internal standard.

Evaluation of use of a dicationic liquid stationary phase in the fast and conventional gas chromatographic analysis of health-hazardous C18 cis/trans fatty acids.

The present research is focused on the evaluation of one 0.10 mm i.d. and two 0.25 mm i.d., ionic liquid (IL) stationary phase [1,9-di(3-vinyl-imidazolium) nonane bis(trifluoromethyl) sulfonyl imidate] columns, with lengths of 12 (the microbore capillary), 30 and 100 m, in the GC analysis of cis/trans fatty acid methyl esters (FAMEs). The selectivity of the IL columns toward a series of standard C(18:1), C(18:2), and C(18:3) geometric isomers (a group of 22 compounds was subjected to GC analysis) was compared to the performance of a widely used column in the cis/trans FAMEs analysis field, viz., a 100 m x 0.25 mm i.d. capillary with a 0.20 microm stationary phase film of bis-cyanopropyl polysiloxane (SP-2560). The selectivity provided by the IL phase was superior if compared to that of the other well-established capillary. An optimized IL method, using the longer column, was subjected to validation: retention time and peak area intraday precision (n = 5) were good, with RSD values lower than 0.07% and 6.6%, respectively; LODs (considering a S/N of 3) for C(18:1Delta)(9tr) and C(18:2Delta)(9tr,12tr) were 0.15 (7.3 ppm) and 0.18 ng (9.1 ppm) on-column, respectively, while LOQs (considering a S/N of 10) were 0.49 (24.3 ppm) and 0.60 ng (30.2 ppm), respectively; the method was found to be linear, for both trans FAMEs, in the 10-2000 ppm range. For the evaluation of accuracy, a hydrogenated margarine, spiked with known amounts of C(18:3Delta)(9c,12c,15c), was subjected to analysis using C(13:0) as an internal standard.

Acquisition of deeper knowledge on the human plasma fatty acid profile exploiting comprehensive 2-D GC.

The present research is focused on the use of comprehensive 2-D GC (GC x GC) for the elucidation of the human plasma fatty acid (FA) profile. The enhanced sensitivity, increased separation power and the formation of group-type patterns provided by GC x GC enabled the identification and quantification of a high number of both well known and unexpected FAs, for a total of 65 components. Peak assignment was, in most cases, supported by using pure standard compounds. The results attained demonstrated the usefulness of the multidimensional GC method in this fundamental field of research.

Offline LC-GC x GC in combination with rapid-scanning quadrupole mass spectrometry.

The present research is focused on the offline combination of normal-phase LC to double-oven GC x GC-quadrupole MS. Initially, a diesel sample was subjected to automated LC x GC in order to define the elution windows of four fractions, viz., saturated hydrocarbons, monocyclic aromatics, dicyclic aromatics, tri- + tetracyclic aromatics; each fraction was collected exploiting the LC system in a further analysis and subjected to large-volume-injection-GC x GC analysis using an apolar-polar column combination. The GC x GC operational conditions were tuned in relation to the specific separation requirements of each heart-cut. The main benefits of what can be defined as offline LC-GC x GC were: (i) the high first-dimension LC selectivity; (ii) the injection of high sample amounts in the GC x GC system, enabling the detection and quantification of a series of low-amount diesel constituents; (iii) improved GC x GC operational conditions for each heart-cut with respect to direct GC x GC.

Analysis of native carotenoid composition in orange juice using C30 columns in tandem.

In the present contribution, a novel analytical approach based on using serial coupled conventional LC columns is proposed to the study of the native carotenoid composition of orange juice. The great difficulties that are found when analyzing complex carotenoid samples, due to the high natural variability of these compounds as well as to the presence of carotenoid esters are well documented. To overcome some of these limitations, we have developed a methodology including the study of both the saponified and the intact sample by means of two different LC-DAD/APCI-MS methods. The increase in the resolution and separation power obtained when using two serial coupled C(30) columns is demonstrated, and significant increases in peak capacity have been achieved. By using this new methodology, 44 different carotenoids have been tentatively identified. Among them, several violaxanthin diesters have been directly identified in orange juice for the first time. The main carotenoids in orange juice were violaxanthin, lutein, luteoxanthin, 9-cis-antheraxanthin, and beta-cryptoxanthin. Some of them were found in both their free and esterified forms. To the best of our knowledge, this is the first application of serial couplings of C(30) columns for the identification of the native carotenoid composition of natural matrices.