A microchip gas chromatography column assembly with a 3D metal printing micro column oven and a flexible stainless-steel column.

In this work, a microchip gas chromatography (GC) column assembly utilizing a three-dimensional (3D) printed micro oven and a flexible stainless steel capillary column was developed. The assembly's performance and separation capabilities were characterized. The key components include a 3D printed aluminum plate (7.50 × 7.50 × 0.16 cm) with a 3-meter-long circular spiral channel, serving as the oven, and the column coiled on the channel with an inner diameter of 320 µm and a stationary phase of OV-1. A heating ceramic plate was affixed on the opposite side of the plate. The assembly weighed 40.3 g. The design allows for easy disassembly, or stacking of heating devices and columns, enabling flexibility in adjusting column length. When using n-C13 as the test analyte at 140 °C, a retention factor (k) was 8.5, and 7797 plates (2599 plates/m) were obtained. The assembly, employing resistance heating, demonstrated effective separation performance for samples containing alkanes, aromatics, alcohols and ketones, with good reproducibility. The reduction in theoretical plates compared to oven heating was only 2.95 %. In the boiling point range of C6 to C18, rapid temperature programming (120 °C/min) was achieved with a power consumption of 119.512 W. The assembly was successfully employed to separate benzene series compounds, gasoline and volatile organic compounds (VOCs), demonstrating excellent separation performance. This innovative design addresses the challenges of the complexity and low repeatability of the fabrication process and the high cost associated with microchip columns. Furthermore, its versatility makes it suitable for outdoor analysis applications.

Chemical Composition and Cytotoxic Activity of the Essential Oil and Oleoresins of In Vitro Micropropagated Ansellia africana Lindl: A Vulnerable Medicinal Orchid of Africa.

Orchids are rich treasure troves of various important phytomolecules. Among the various medicinal orchids, Ansellia africana stands out prominently in the preparing of various herbal medicines due to its high therapeutic importance. The nodal explants of A. africana were sampled from asymbiotically germinated seedlings on basal Murashige and Skoog (MS) medium and were micropropagated in MS medium supplemented with 3% sucrose and 10 µM meta topolin (mT) + 5 µM naphthalene acetic acid (NAA) +15 µM indole butyric acid (IBA) + 30 µM phloroglucinol (PG). In the present study, the essential oil was extracted by hydrodistillation and the oleoresins by the solvent extraction method from the micropropagated A. africana. The essential oil and the oleoresins were analysed by Gas Chromatography (GC) and GC/MS (Mass spectrometry). A total of 84 compounds were identified. The most predominant components among them were linoleic acid (18.42%), l-ascorbyl 2,6-dipalmitate (11.50%), linolenic acid (10.98%) and p-cresol (9.99%) in the essential oil; and eicosane (26.34%), n-butyl acetate (21.13%), heptadecane (16.48%) and 2-pentanone, 4-hydroxy-4-methyl (11.13%) were detected in the acetone extract; heptadecane (9.40%), heneicosane (9.45%), eicosane (6.40%), n-butyl acetate (14.34%) and styrene (22.20%) were identified and quantified in the ethyl acetate extract. The cytotoxic activity of essential oil and oleoresins of micropropagated A. africana was evaluated by MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium Bromide) assay on Vero cells compared to the standard drug doxorubicin chloride. The present research contains primary information about the therapeutic utility of the essential oil and oleoresins of A. africana with a promising future research potential of qualitative and quantitative improvement through synchronised use of biotechnological techniques.

Leaf Surface Wax Chemicals in Trichosanthes anguina (Cucurbitaceae) Cultivars Mediating Short-Range Attraction and Oviposition in Diaphania indica.

Larval Diaphania indica (Saunders) (Lepidoptera: Crambidae) cause complete defoliation of Trichosanthes anguina L. and reduce crop yield in India. Females lay eggs on the leaf surface, and therefore leaf surface waxes are potentially involved in host selection. Alkanes and free fatty acids are the major constituents of leaf surface waxes, so a study was conducted to determine whether these wax constituents from three T. anguina cultivars (MNSR-1, Baruipur Long, and Polo No.1) could act as short-range attractants and oviposition stimulants in D. indica females. Twenty n-alkanes from n-C14 to n-C36 and 13 free fatty acids from C12:0 to C21:0 were detected in the leaf surface waxes of these cultivars. Heptadecane and stearic acid were predominant among n-alkanes and free fatty acids, respectively, in these cultivars. Females showed attraction towards one leaf equivalent surface wax of each of these cultivars against solvent controls (petroleum ether) in Y-tube olfactometer bioassays. A synthetic blend of heptadecane, eicosane, hexacosane, and stearic acid, a synthetic blend of hexacosane and stearic acid, and a synthetic blend of pentadecane and stearic acid comparable to amounts present in one leaf equivalent surface wax of MNSR-1, Baruipur Long, and Polo No.1, respectively, were short-range attractants and oviposition stimulants in D. indica. Female egg laying responses were similar to each of these blends, providing information that could be used to developing baited traps in integrated pest management (IPM) programs.

Characterizing the Volatile and Sensory Profiles, and Sugar Content of Beeswax, Beebread, Bee Pollen, and Honey.

Bee products are a well-known remedy against numerous diseases. However, from the consumers' perspective, it is essential to define factors that can affect their sensory acceptance. This investigation aimed to evaluate the volatile and sensory profiles, and sugar composition of beeswax, beebread, pollen, and honey. According to the HS-SPME/GC-MS results, 20 volatiles were identified in beeswax and honey, then 32 in beebread, and 33 in pollen. Alkanes were found to dominate in beeswax, beebread, and pollen, while aldehydes and monoterpenes in honey. In the case of sugars, a higher content of fructose was determined in beebread, bee pollen, and honey, whereas the highest content of glucose was assayed in beeswax. In the QDA, the highest aroma intensity characterized as honey-like and sweet was found in honey, while the acid aroma was typical of beebread. Other odor descriptors, including waxy, pungent, and plant-based aromas were noted only in beeswax, honey, and pollen, respectively.

Ionic liquid stationary phase coating optimization for semi-packed microfabricated columns.

This work highlights the effect of the stationary phase coating process on the separation efficiency of gas chromatography microcolumns. The stationary phase coating quality was characterized by three different bis(trifluoromethylsulfonyl)imide (NTf2) anion based ionic liquids. The ionic liquids containing NTf2 anion are used for gas chromatography due to their high temperature stability. In this work, the chemical and physical approaches of column deactivation as well as the temperature treatment were evaluated by separating a mixture of 20 organic components and saturated alkanes. The results show that higher oven temperature treatment provides higher efficiency while losing a bit of peak symmetry. The thermal treated 1-butylpyridinum bis(trifluoromethylsulfonyl) imide [BPY][NTf2] stationary phase at 240°C demonstrated as high as 8300 plates per meter for naphthalene. This was a 5-fold increase in separation efficiency in comparison to those of the columns treated at 200°C. Albeit being within acceptable ranges, the peak tailing degraded from 1.17 to 1.46 for naphthalene when the processing temperature for coating increased. Both chemical and physical deactivation process increased separation efficiencies and peak resolution.

Biological Activity of Agaricinic Acid Nanoparticles against Human Hepatoma HepG2 Cells.

A stable preparation of agaricinic acid nanoparticles was obtained. The mean hydrodynamic size of nanoparticles according to photon correlation spectroscopy was 200 nm and zeta potential was -57 mV. Cytotoxic activity of agaricinic acid nanoparticles against human HepG2 hepatoma cells was evaluated. Nanoparticles with a low concentration of agaricinic acid stimulated and with high concentration - suppressed metabolic activity and viability of hepatoma cells. The EC50 for the stimulating effect was 32.8 µg/ml, and the IC50=602.1 mg/ml. The preparation of agaricinic acid nanoparticles can be used in medicine as a potential antitumor agent.

Fusicoccane-derived diterpenoids with bridgehead double-bond-containing tricyclo[9.2.1.03,7]tetradecane ring systems from Alternaria brassicicola.

Fusicoccane-derived diterpenoids bearing a unique bridgehead double-bond-containing tricyclo[9.2.1.03,7]tetradecane (5-9-5 ring system) core skeleton represent a rarely reported class of rearranged terpenoids, which traced back to fusicoccanes with a classical dicyclopenta[a,d]cyclooctane (5-8-5 ring system) core skeleton via a crucial Wagner-Meerwein rearrangement reaction. In this research, alterbrassicenes B-D (1-3), three new rearranged fusicoccane diterpenoids bearing a rare bridgehead double-bond-containing tricyclo[9.2.1.03,7]tetradecane core skeleton, together with two known congeners, brassicicenes O and K (4 and 5), were isolated from the modified cultures of fungus Alternaria brassicicola. Their structures were elucidated by comprehensive analyses of the NMR and HRESIMS data, and the absolute configurations of 1 and 4 were further confirmed via a combination of 13C NMR and ECD calculations and single-crystal X-ray diffraction analysis (Cu Kα). Interestingly, alterbrassicene B (1) represented the second case of bridgehead C-10-C-11 double-bond-containing natural products with a bicyclo[6.2.1]undecane core skeleton, and also featured an undescribed oxygen bridge between C-6 and C-14 to construct an unprecedentedly caged tetracyclic system. Alterbrassicenes B-D showed moderate cytotoxic activity against certain human tumor cell lines with IC50 values in the range of 15.87-36.85 µM.

Preliminary Study on the Differences in Hydrocarbons Between Phosphine-Susceptible and -Resistant Strains of Rhyzopertha dominica (Fabricius) and Tribolium castaneum (Herbst) Using Direct Immersion Solid-Phase Microextraction Coupled with GC-MS.

Phosphine resistance is a worldwide issue threatening the grain industry. The cuticles of insects are covered with a layer of lipids, which protect insect bodies from the harmful effects of pesticides. The main components of the cuticular lipids are hydrocarbon compounds. In this research, phosphine-resistant and -susceptible strains of two main stored-grain insects, T. castaneum and R. dominica, were tested to determine the possible role of their cuticular hydrocarbons in phosphine resistance. Direct immersion solid-phase microextraction followed by gas chromatography-mass spectrometry (GC-MS) was applied to extract and analyze the cuticular hydrocarbons. The results showed significant differences between the resistant and susceptible strains regarding the cuticular hydrocarbons that were investigated. The resistant insects of both species contained higher amounts than the susceptible insects for the majority of the hydrocarbons, sixteen from cuticular extraction and nineteen from the homogenized body extraction for T. castaneum and eighteen from cuticular extraction and twenty-one from the homogenized body extraction for R. dominica. 3-methylnonacosane and 2-methylheptacosane had the highest significant difference between the susceptible and resistant strains of T. castaneum from the cuticle and the homogenized body, respectively. Unknown5 from the cuticle and 3-methylhentriacontane from the homogenized body recorded the highest significant differences in R. dominica. The higher hydrocarbon content is a key factor in eliminating phosphine from entering resistant insect bodies, acting as a barrier between insects and the surrounding phosphine environment.

Knowing Me, Knowing You: Anal Gland Secretion of European Badgers (Meles meles) Codes for Individuality, Sex and Social Group Membership.

European badgers, Meles meles, are group-living in the UK, and demarcate their ranges with shared latrines. As carnivores, badgers possess paired anal glands, but olfactory information on the content of badger anal gland secretion (AGS) is largely uninvestigated. Here, we examined the volatile organic compounds (VOCs) of AGS samples from 57 free-living badgers using solid-phase microextraction (SPME) and gas chromatography-mass spectrometry. AGS was rich in alkanes (C7-C15, 14.3% of identified compounds), aldehydes (C5-C14, 9.7%), phenols (C6-C15, 9.5%), alcohols (C5-C10, 7.3%), aromatic hydrocarbons (C6-C13, 6.8%), ketones (C6-C13, 6.3%) and carboxylic acids (C3-C12, 5.6%) and contained a variety of esters, sulfurous and nitrogenous compounds, and ethers. The number of VOCs per profile ranged from 20 to 111 (mean = 65.4; ± 22.7 SD), but no compound was unique for any of the biological categories. After normalization of the raw data using Probabilistic Quotient Normalization, we produced a resemblance matrix by calculating the Euclidian distances between all sample pairs. PERMANOVA revealed that AGS composition differs between social groups, and concentration and complexity in terms of number of measurable VOCs varies between seasons and years. AGS VOC profiles encode individual identity, sex and vary with female reproductive state, indicating an important function in intraspecific communication. Because AGS is excreted together with fecal deposits, we conclude that chemical complexity of AGS enables particularly latrine-using species, such as badgers, to advertise more complex individual-specific information than in feces alone.

Triptycene-based stationary phases for gas chromatographic separations of positional isomers.

This work presents the investigation of two triptycene-based materials (TP-3OB and TP-3Im) as the stationary phases for gas chromatographic (GC) separations. The TP-3OB and TP-3Im capillary columns fabricated by static coating exhibited column efficiency of 3000-3500 plates/m for n-dodecane at 120 °C. Also, their McReynolds constants and Abraham system constants were determined to characterize their polarity and molecular interactions with analytes. On the basis of the unique 3D TP architecture, the TP-3OB and TP-3Im stationary phases exhibited complementary high-resolution performance for analytes of a wide ranging polarity, including alkylbenzenes, alkylnaphthalenes, halobenzenes, phenols and anilines, respectively. Moreover, the TP-based columns exhibited good repeatability and reproducibility on the retention times of analytes with the relative standard deviation (RSD) values in the range of 0.01-0.14% for run-to-run, 0.11-0.47% for day-to-day and 0.68-4.7% for column-to-column, respectively. Additionally, their applications for the determination of isomer impurities in the commercial reagents of o-dichlorobenzene, p-/m-diethylbenzene, o-toluidine and 2,3-/3,5-xylidine proved their good potential for practical analysis. This work demonstrates the promising future of the triptycene-based stationary phases for chromatographic separations.

Retention time prediction in thermally modulated comprehensive two-dimensional gas chromatography: Correcting second dimension retention time modeling error.

Thermodynamic retention modeling to a thermally modulated comprehensive two-dimensional gas chromatography (GC × GC) system run under constant flow is performed. Significant errors in modeled second dimension retention time (tr,2) were observed, in line with past work on thermally modulated GC × GC modeling. A comprehensive study of tr,2 modeling error for alkane separations across a wide range of heating ramp rates and carrier gas flow rates was performed. Modeling errors were found to be systematic and a function of analyte elution temperature and mobile phase velocity. A model to account for these systematic errors was generated, and associated coefficients were determined which reduced average tr,2 retention time error in 144 hydrocarbon separations by an order of magnitude resulting in significant improvement in prediction accuracy. The model was used to correct the separation of 139 Grob mix analyte separations, providing an average tr,2 modeling error of 0.030 ± 0.022 s. The model successfully predicted the separation of n-alkanes on a longer second dimension column configuration.

Desiccation Resistance and Micro-Climate Adaptation: Cuticular Hydrocarbon Signatures of Different Argentine Ant Supercolonies Across California.

Cuticular hydrocarbons (CHCs), the dominant fraction of the insects' epicuticle and the primary barrier to desiccation, form the basis for a wide range of chemical signaling systems. In eusocial insects, CHCs are key mediators of nestmate recognition, and colony identity appears to be maintained through a uniform CHC profile. In the unicolonial Argentine ant Linepithema humile, an unparalleled invasive expansion has led to vast supercolonies whose nestmates can still recognize each other across thousands of miles. CHC profiles are expected to display considerable variation as they adapt to fundamentally differing environmental conditions across the Argentine ant's expanded range, yet this variation would largely conflict with the vastly extended nestmate recognition based on CHC uniformity. To shed light on these seemingly contradictory selective pressures, we attempt to decipher which CHC classes enable adaptation to such a wide array of environmental conditions and contrast them with the overall CHC profile uniformity postulated to maintain nestmate recognition. n-Alkanes and n-alkenes showed the largest adaptability to environmental conditions most closely associated with desiccation, pointing at their function for water-proofing. Trimethyl alkanes, on the other hand, were reduced in environments associated with higher desiccation stress. However, CHC patterns correlated with environmental conditions were largely overriden when taking overall CHC variation across the expanded range of L. humile into account, resulting in conserved colony-specific CHC signatures. This delivers intriguing insights into the hierarchy of CHC functionality integrating both adaptation to a wide array of different climatic conditions and the maintenance of a universally accepted chemical profile.

Analysis of Cuticular Lipids of the Pharaoh Ant (Monomorium pharaonis) and Their Selective Adsorption on Insecticidal Zeolite Powders.

The pharaoh ant is a notorious and hard to eradicate pest, which poses a threat in hospitals, spreading pathogens and contaminating sterile equipment. When applied on ants, zeolites adsorb part of their epicuticular wax layer. The ants are then vulnerable to desiccation, since this layer regulates water exchange. We analyzed the chemical composition of this wax layer using GC-MS (Gas Chromatography-Mass Spectrometry). A hexane wash of M. pharaonis foragers resulted in the identification of 53 components, four of which were not previously defined in Monomorium species. Selective adsorption of specific compounds on zeolites assisted in the identification of compounds which could not be separated on the GC column and allowed for the identification of three additional compounds. Zeolites show different affinities for the wax compounds depending on pore structure and chemical composition. Selective adsorption of alkanes on zeolites is also investigated in the fields of refinery processes and catalysis. Pore mouth and key lock adsorption mechanisms and selectivity according to molecular weight and branching, investigated in these fields, are also involved in adsorption processes of epicuticular waxes. The insecticidal activity of a zeolite is related to adsorption selectivity rather than capacity. One of the best adsorbing zeolites showed limited insecticidal activity and can be considered as a non-lethal alternative for epicuticular wax sampling.

Removal of tridecane dicarboxylic acid in water by nanoscale Fe0/Cu0 bimetallic composites.

In this study, nanoscale zerovalent Fe0/Cu0 bimetallic composites were synthesized by liquid-phase reduction of Fe(II)/Cu(II) and applied for decomposition of tridecane dicarboxylic acid (DC13). The removal performance of Fe0/Cu0 bimetallic composites for DC13 in terms of Fe/Cu ratios, addition amount, reaction time and initial pH were studied. The as-prepared nanoscale composites were characterized by a transmission electron micrographs (TEM), scanning electron microscopy (SEM), X-ray diffraction (XRD), BET surface area, fourier transform infrared spectroscopy (FT-IR) and inductively coupled plasma-atomic emission spectrometry (ICP). Finally, the degradation mechanisms of DC13 utilizing the Fe0/Cu0 nanocomposites were investigated by using mass spectrumetry (MS). The results indicated that the Fe0/Cu0 bimetallic composites exerted a remarkable removal capacity for DC13 through the multiple reactions, e.g., coagulation, adsorption and •OH reduction in the Fe0/Cu0 system. XPS indicated that the Fe0/Cu0 reduction reaction of hydroxyl radicals (•OH) system played a significant role in degradation of DC13 and the LC-MS result suggested that DC13 was degraded into inorganic small molecules by •OH radicals generated from the corrosion of Fe0. The experimental results indicated that the nanoscale Fe0/Cu0 could be used as a potential material to remove DC13 because of its remarkable degradability.

Promoting the treatment of crude oil alkane pollution through the study of enzyme activity.

Microbes appear to play a key role in bioremediation of petroleum hydrocarbons pollution and little attention has been paid to the enzyme activity in the process of alkane bioremediation. Oil field bacterium identified as Pseudomonas synxantha LSH-7' was chosen as the tested strain. Periodically collected samples were analyzed by GC-FID (Gas Chromatography- Flame Ionization Detector) and RT-qPCR (Quantitative-Real-Time-PCR). GC-FID results showed this bacterial strain has great degradation ability on crude oil n-alkanes and RT-qPCR data indicated the differences between the three genes expression including AlkB-, Cytochromes P450-, and almA- related when grown on different-chain alkanes. Meanwhile, enzyme activity like alkane hydroxylase, alcohol dehydrogenase, dehydrogenase, protease, phosphatase, catalase and lipase were measured. Extracellular alkane hydroxylase was induced in a higher degree than intracellular in the early incubation time, alcohol dehydrogenase increased/decreased along with alkane hydroxylase, and the pH of the medium obviously decreased. Other enzymes were also described including dehydrogenase activity that reached a highest point that was slower than alcohol dehydrogenase, protease activity started multiplying after a period of culture while biomass was immediately increased, catalase activity dramatically enhanced in the presence of alkanes, phosphatase activity was closely linked to pH approximately but lipase activity was found to be moderate.

Preparation, characterization and application of polymethacrylate-based monolithic columns for fast and efficient separation of alkanes, alcohols, alkylbenzenes and isomeric mixtures by gas chromatography.

Application of monolithic columns in gas chromatography is still considered very limited. In this work, several polymethacrylate-based monolithic capillary columns were fabricated, characterized and used in gas chromatography. The five monomers used were: methyl methacrylate, (MMA), hexyl methacrylate (HMA), glycidyl methacrylate (GMA), 2-butoxyethyl methacrylate (BEMA) and isobornyl methacrylate (IBMA), while ethylene dimethacrylate was the crosslinker. The monoliths were synthesized in 30 cm length capillaries possessing inner diameters (i.d.) of 0.25 mm. The prepared monolithic columns were applied for separation of 3 series of homologous alkanes, alcohols and alkylbenzenes, as well as some isomeric mixtures. Van Deemter plots were used to optimize and compare the columns performance. The smaller methacrylates (MMA and GMA) exhibited higher porosity and permeability with low column backpressure values and poorer efficiency than the larger methacrylate monomers (HMA and BEMA). The columns prepared from IBMA monomer showed the highest pressure and the least separation efficiency. The fastest full separation of alkanes was achieved on HMA-co-EDMA column in about 3.0 min with resolution better than 2.73, while the fastest full separation of alcohols and alkylbenzenes was carried out using BEMA-co-EDMA column in less than 0.8 and 1.75 min with chromatographic resolution better than 1.27 and 1.85, respectively. Again, BEMA-co-EDMA column gave the best performance with the fastest and complete separation of all studied isomeric mixtures. For all tested series of solutes, the better separation efficiency was reached with tridecane, which gave 25,200 plates/m on the HMA-co-EDMA column. Another application was carried out using HMA-co-EDMA column for determination of myrcene and limonene, two monoterpenic isomers, in some fruit peels. Under the optimum GC conditions, a rapid separation of myrcene and limonene was achieved in less than 1.0 min with chromatographic resolution of 2.56. The highest contents of myrcene (0.131 mg/g) and limonene (1.225 mg/g) were measured in the hexane extracts of grapefruit and Egyptian orange, respectively. Finally, a comparison between the prepared columns and a commercial capillary column was performed. Based on the measured run time and HETP values, HMA-co-EDMA and BEMA-co-EDMA monolithic columns exhibited faster separation and higher efficiency for n-alkanes and alkylbenzenes than the TR-5 open tubular column, although they are 100 times shorter.

A highly ordered chiral inorganic mesoporous material used as stationary phase for high-resolution gas chromatographic separations.

A highly ordered chiral mesoporous silica-coated capillary column has been used for high-resolution gas chromatographic separations. The column has excellent selectivity, not only for the separation of isomers, polycyclic aromatic hydrocarbons, linear alkanes, long chain alkanes, Grob's test mixture and aromatic hydrocarbons, but also for the resolution of different classes of chiral compounds. Additionally, the column exhibits high column efficiency, excellent temperature resistance, and analysis times are short. This is the first report of a highly ordered chiral inorganic mesoporous silica used in separation science.

Bioactive compounds in Pinang Yaki (Areca vestiaria) fruit as potential source of antifertility agent.

Fruits of Pinang Yaki (Areca vestiaria) are used by the people around Bogani Nani Wartabone as contraseption for men. Extracts from the fruit contain tannin, triterpenoid, flavonoid and saponin which are potential as bioactive compounds. This research aimed at exploring the fractions or bioactive compounds contained in the fruit. The extract was prepared by fractionation using hexane. The fractions were separated and analysed by gas chromatography mass spectrometry (GC-MS) technique. The fractions revealed the presence of five compounds. These compounds were identified by interpretation of mass spectra and comparing their retention time and covate indexes with those from literature. The five compounds are pentadecane, methyl-dodecanate, methyl-tetradecanoate, hexadecanoic acid and methyl-octadecanate.

Extending the upper temperature range of gas chromatography with all-silicon microchip columns using a heater/clamp assembly.

Miniaturization of gas chromatography (GC) instrumentation is of interest because it addresses current and future issues relating to compactness, portability and field application. While incremental advancements continue to be reported in GC with columns fabricated in microchips (referred to in this paper as "microchip columns"), the current performance is far from acceptable. This lower performance compared to conventional GC is due to factors such as pooling of the stationary phase in corners of non-cylindrical channels, adsorption of sensitive compounds on incompletely deactivated surfaces, shorter column lengths and less than optimum interfacing to injector and detector. In this work, a GC system utilizing microchip columns was developed that solves the latter challenge, i.e., microchip interfacing to injector and detector. A microchip compression clamp was constructed to heat the microchip (i.e., primary heater), and seal the injector and detector fused silica interface tubing to the inlet and outlet ports of the microchip channels with minimum extra-column dead volume. This clamp allowed occasional operation up to 375°C and routine operation up to 300°C. The compression clamp was constructed of a low expansion alloy, Kovar™, to minimize leaking due to thermal expansion mismatch at the interface during repeated thermal cycling, and it was tested over several months for more than one hundred injections without forming leaks. A 5.9m long microcolumn with rectangular cross section of 158µm×80µm, which approximately matches a 100µm i.d. cylindrical fused silica column, was fabricated in a silicon wafer using deep reactive ion etching (DRIE) and high temperature fusion bonding; finally, the channel was coated statically with a 1% vinyl, 5% phenyl, 94% methylpolysiloxane stationary phase. High temperature separations of C10-C40 n-alkanes and a commercial diesel sample were demonstrated using the system under both temperature programmed GC (TPGC) and thermal gradient GC (TGGC) conditions. TGGC analysis of a complex essential oil sample was also demonstrated. Addition of a secondary heater and polyimide insulation proved to be helpful in achieving the desired elution temperature without having to raise the primary heater temperature above 300°C for high boiling point compounds.

Ionic Liquid-Liquid Chromatography: A New General Purpose Separation Methodology.

Ionic liquids can form biphasic solvent systems with many organic solvents and water, and these solvent systems can be used in liquid-liquid separations and countercurrent chromatography. The wide range of ionic liquids that can by synthesised, with specifically tailored properties, represents a new philosophy for the separation of organic, inorganic and bio-based materials. A customised countercurrent chromatograph has been designed and constructed specifically to allow the more viscous character of ionic liquid-based solvent systems to be used in a wide variety of separations (including transition metal salts, arenes, alkenes, alkanes, bio-oils and sugars).