Conventional and enantioselective gas chromatography with microfabricated planar columns for analysis of real-world samples of plant volatile fraction.

Within a project exploring the application of lab-on-chip GC to in-field analysis of the plant volatile fraction, this study evaluated the performance of a set of planar columns (also known as microchannels, MEMS columns, or microfabricated columns) of different dimensions installed in a conventional GC unit. Circular double-spiral-shaped-channel planar columns with different square/rectangular sections up to 2m long were applied to the analysis of both essential oils and headspace samples of a group of medicinal and aromatic plants (chamomile, peppermint, sage, rosemary, lavender and bergamot) and of standard mixtures of related compounds; the results were compared to those obtained with reference narrow-bore columns (l:5m, dc:0.1mm, df:0.1 µm). The above essential oils and headspaces were first analyzed quali-and quantitatively with planar columns statically coated with conventional stationary phases (5%-phenyl-polymethylsiloxane and auto-bondable nitroterephthalic-acid-modified polyethylene glycol), and then submitted to chiral recognition of their diagnostic markers, by enantioselective GC with a planar columns coated with a cyclodextrin derivative (30% 6(I-VII)-O-TBDMS-3(I-VII)-O-ethyl-2(I-VII)-O-ethyl-ß-cyclodextrin in PS-086). Column characteristics and analysis conditions were first optimized to obtain suitable retention and efficiency for the samples investigated. The planar columns tested showed performances close to the reference conventional narrow-bore columns, with theoretical plate numbers per meter (N/m) ranging from 6100 to 7200 for those coated with the conventional stationary phases, and above 5600 for those with the chiral selector.

Quantitative determination of some volatile suspected allergens in cosmetic creams spread on skin by direct contact sorptive tape extraction-gas chromatography-mass spectrometry.

This study describes a method based on direct contact sorptive tape extraction followed by on-line thermal desorption gas chromatography-mass spectrometry (DC-STE-GC-MS) to detect and quantify a group of suspected volatile allergens on the European Union (E.U.) list and a related compound on the skin (the stratum corneum) of volunteers treated with a cream of known composition fortified with the reference allergens. The following compounds were tested: citronellol, Z-citral (neral), geraniol, cinnamaldehyde, anisyl alcohol, cinnamyl alcohol, eugenol, methyleugenol, coumarin, isoeugenol, alpha-isomethylionone, 2-(4-tert-butylbenzyl)propionaldehyde (lilial), alpha-amylcinnamaldehyde, alpha-hexylcinnamaldehyde. Sorptive tape extraction (STE) is a sorption-based sampling technique in which a flexible polydimethylsiloxane (PDMS) tape is used to recover analytes by direct contact with the surface of a solid matrix or from the headspace in equilibrium with it. The reliability of the method was confirmed by: (i) allergen recoveries varying from 52.3% for lilial to 95.7% for neral, (ii) linearity in the range 10-150ppm, with regression coefficient R(2) always above 0.97, (iii) repeatability of each analyte, RSD% never exceeding 10%, (iv) intermediate precision, always below 15%, and (v) LOD and LOQ in the ppb range, therefore fully compatible with E.U. prescriptions (ppm). Other parameters such as substantivity analyte, approximate permeation through skin and influence of different nature of stratum corneum on recovery were also investigated. The method was also successfully applied to five commercially available creams declared to contain some of the allergens in question spread on the skin of the same volunteers.

Analysis of environmental endocrine disrupting chemicals using the E-screen method and stir bar sorptive extraction in wastewater treatment plant effluents.

Endocrine disrupting chemicals (EDCs) have become a major issue in the field of environmental science due to their ability to interfere with the endocrine system. Recent studies show that surface water is contaminated with EDCs, many released from wastewater treatment plants (WWTP). This pilot study used biological (E-screen assay) and chemical (stir bar sorptive extraction-GC-MS) analyses to quantify estrogenic activity in effluent water samples from a municipal WWTP and in water samples of the recipient river, upstream and downstream of the plant. The E-screen assay was performed on samples after solid phase extraction (SPE) to determine total estrogenic activity; the presence of estrogenic substances can be evaluated by measuring the 17-beta-estradiol equivalency quantity (EEQ). Untreated samples were also assayed with an acute toxicity test (Vibrio fischeri) to study the correlation between toxicity and estrogenic disruption activity. Mean EEQs were 4.7 ng/L (+/-2.7 ng/L) upstream and 4.4 ng/L (+/-3.7 ng/L) downstream of the plant, and 11.1 ng/L (+/-11.7 ng/L) in the effluent. In general the WWTP effluent had little impact on estrogenicity nor on the concentration of EDCs in the river water. The samples upstream and downstream of the plant were non-toxic or weakly toxic (0

High-speed gas chromatography with direct resistively-heated column (ultra fast module-GC)-separation measure (S) and other chromatographic parameters under different analysis conditions for samples of different complexities and volatilities.

The influence of GC speed on the separation capability of a chromatographic system is reported measuring a series of parameters including separation measure (S), peak capacity (n), peak width (w), analysis time, t(b) (determined on the last eluting compound) and separation measure/analysis time ratio (S/t(b)) determined by analyzing a bergamot essential oil sample and a standard mixture of pesticides. Conventional GC, fast GC (with 10 m (FGC10) and 5 m (FGC5) narrow-bore columns), and direct resistively-heated ultra fast module-GC (UFM-GC) were the GC speed approaches used. The influence of different heating rates with a constant flow for FGC5, FGC 10, and UFM-GC and with variable flows for UFM-GC on S, n, w, S/t(b), and t(b) was also studied. The results of this study show that: (a) separation capability of the chromatographic system (i.e. S and n) and analysis time depend on the GC approaches. Within each GC approach, S and n and analysis time depend on the heating rates, although to a different extent, and S and n decrease much less than the gain in analysis time, in particular when fast heating rates are applied; (b) in UFM-GC, the loss of separation capability with heating rate can also be partially compensated by the choice of an appropriate flow rate that, within each heating rate, may contribute to increase S while reducing t(b); (c) within a specific GC approach, the chromatographic system (column and stationary phase) and conditions (heating and flow rates) must be such to achieve a suitable S-value when two analytes must be separated with a given resolution in a minimum analysis time.

Fast supercritical fluid extraction and high-resolution gas chromatography with electron-capture and flame photometric detection for multiresidue screening of organochlorine and organophosphorus pesticides in Brazil's medicinal plants.

A description is given of a rapid and environmentally friendly method to determine organochlorine and organophosphorus pesticide multiresidues--malathion, methidathion, fenitrothion, fenthion, parathion-ethyl, parathion-methyl, lindane, hexachlorobenzene, chlorothalonil, tetradifon, alpha-endosulfan, beta-endosulfan and dieldrin-in Passiflora alata Dryander and pasiflora edulis Sims. f. flavicarpa Deg. leaves by supercritical fluid extraction and high-resolution gas chromatography with electron-capture and flame photometric detection (HRGC-ECD/FPD). The mild extraction conditions [pure CO2; 100 bar (1 bar = 10(5) Pa) and 40 degrees C (p = 0.62 g/ml); 5 min static+10 min dynamic extraction time; ODS trap and elution with 1 ml n-hexane at 2 ml/min] allow for direct analysis by HRGC-ECD/FPD with no prior cleaning procedure. The method provides. in accordance with the validation criteria of the European Pharmacopoeia, analytical results that are similar or even better than the official procedures, and is simpler, faster and cheaper. Mean recoveries of 69.8-107.1% were obtained, with 1.4-14.7% reproducibility (RSD). The method was applied to analyse commercial samples of Passiflora L. from Brazil. Twenty-three percent of the samples showed the presence of the organochlorine or organophosphorus pesticide residue investigated.

Conventional inner diameter short capillary columns: an approach to speeding up gas chromatographic analysis of medium complexity samples.

Short capillary columns (5 m) with 0.25 mm inner diameter (I.D.) are applied to the GC analysis of medium complexity samples (up to 30 components) with the aim of shortening analysis time. This approach is complementary to fast GC with narrow-bore columns and is based on compensating the lower efficiency of short columns with conventional I.D.'s (0.25-0.32 mm) by using a stationary phase selectivity suitable to separate the components of the sample under investigation, so that the required resolution power is achieved but, at the same time, the analysis time is shortened. The qualitative and quantitative effectiveness of this approach is demonstrated through the analysis of: essential oils with different compositions (chamomile and rosemary), low-volatility triterpenes in a plant extract (Maytenus aquifolium and M. ilicfolium), thermolabile pyrethrins in a Pyrethrum extract, and a mixture of pesticides applied to protect medicinal plant crops. In all examples, GC analysis was five to ten times faster than with conventional columns.

HPLC-UV and HPLC-positive-ESI-MS analysis of the diterpenoid fraction from caper spurge (Euphorbia lathyris) seed oil.

Caper spurge (Euphorbia lathyris L.) seed oil contains a series of diterpenoids known as Euphorbia factors, or L-factors, L1-L9. They are esters of several polyols (lathyrol, epoxylathyrol, hydroxylathyrol and ingenol) and account for about 3-5% of the oil. The percentage of ingenol-based L-factors is very low, less than 5% of the diterpenoid fraction, but some of them (factors L5 and L6) are responsible for the irritant and co-carcinogenic activities of the oil. This paper reports an HPLC-UV and HPLC-positive-ESI-MS analysis of the diterpenoid fraction of caper spurge seed oil before and after selective hydrolysis of ingenol-based L-factors. Separation of lathyrane polyols and esters, and ingenol and its esters was achieved using a chromatographic system consisting of a C18 stationary phase and acetonitrile: water as mobile phase. A new macrocyclic constituent, the deoxy Euphorbia factor L1, was identified in the oil.

Influence of fibre coating in headspace solid-phase microextraction-gas chromatographic analysis of aromatic and medicinal plants.

Solid-phase microextraction (SPME) is a solvent-free technique, which is well established in headspace analysis since it is sensitive, because of the concentration factor achieved by the fibres, and selective, because of different coating materials which can be used. The performance of eight commercially available SPME fibres was compared to evaluate the recoveries of some characteristic components with different polarities and structures present in the headspace of four aromatic and medicinal plants: rosemary (Rosmarinus officinalis L.), sage (Salvia officinalis L.), thyme (Thymus vulgaris L.) and valerian (Valeriana officinalis L.). The relative concentration capacity of each fibre on the same components of each plant was also determined by comparing their abundance with that obtained by classical static-headspace GC. The partition coefficient, K1, between the headspace gaseous phase and SPME polymeric coating, and the relative concentration factors, of some of the characteristic components of the plant investigated dissolved in dibutyl phtalate, were also determined, under rigorously standardised analysis conditions. The results showed that the most effective fibres were those consisting of two components, i.e., a liquid phase (polydimethylsiloxane) and a porous solid (carboxen or divinylbenzene, or both).

Cyclodextrin derivatives as chiral selectors for direct gas chromatographic separation of enantiomers in the essential oil, aroma and flavour fields.

This article reviews papers published over the period 1995-1998 dealing with the application of cyclodextrin derivatives (CDs) as chiral selector for direct enantiomer GC separation of volatile optically active components in the essential oil, extract, flavour and aroma fields. For each application, the racemate analysed, the CD employed as chiral selector and the matrix investigated are reported. The applications are grouped by analytical technique employed: capillary gas chromatography and capillary gas chromatography-mass spectrometry (GC and GC-MS); two-dimensional gas chromatography (GC x GC); capillary gas chromatography-isotope ratio-mass spectrometry (GC-IRMS); liquid chromatography-capillary gas chromatography (LC-GC).

Simultaneous determination of linuron and trifluralin residues in carrots and their pulp by liquid chromatography and gas chromatography.

A simple method is described for determining trifluralin and linuron in carrots and their pulp. Samples are extracted with hexane-ethyl ether (1 + 1), cleaned up with a disposable Florisil cartridge, and eluted first with hexane-ethyl ether (99 + 1) (for trifluralin), and then with hexane-ethyl ether (3 + 7) (for linuron). Trifluralin is then analyzed by electron capture gas chromatography (GC/ECD), and linuron by GC/ECD and liquid chromatography with ultraviolet detection (LC/UV). Recoveries were determined by spiking untreated carrot and carrot pulp homogenates with trifluralin and linuron at 0.04, 0.16, and 0.32 micrograms/g. Six determinations were performed at each level for both compounds. GC/ECD average recoveries were 87.1% for trifluralin and 93.6% for linuron in carrots and 89.9% for trifluralin and 94.2% for linuron in carrot pulp. LC/UV recoveries for linuron were 91.5% for carrots and 92.8% for carrot pulp.

Determination of pyrrolizidine alkaloids in Senecio inaequidens D.C. by capillary gas chromatography.

A study of the toxic pyrrolizidine alkaloids contained in Senecio inaequidens D.C., an infestant species of the Senecio genus, widespread in the North East of Italy, is reported. Five of these compounds, senecivernine, senecionine, integerrimine, retrorsine and an analogue of retrorsine, were identified by means of capillary gas chromatography and capillary gas chromatography-mass spectrometry.

Constituents of Essential Oil of Nepeta nepetella.

The essential oil of NEPETA NEPETELLA L. growing in the Aosta Valley (Valnontey), Italy, obtained by steam distillation of the leaves and the flowers, was investigated by capillary gas chromatography in combination with mass spectrometry. To facilitate identification, fractionation of the oil with straight phase HPLC was performed. Nepetalactone (76.5%) is the main component of the oil. The isomers epinepetalactone (0.6%) and neonepetalactone (0.4%) together with the dihydro (1.6%) and dehydro (traces) nepetalactone derivatives were also identified. These compounds are considered to be responsible for the feline attractant activity of NEPETA NEPETELLA L.

Constituents of the Essential Oil of Artemisia coerulescens.

By combination of liquid-solid chromatography, capillary GLC and mass spectrometry, the essential oil obtained by steam distillation from the leaves and flowers of ARTEMISIA COERULESCENS L., growing in Tuscany (Poggio di Monselvoli, Siena), was analysed, alpha-Thujone, beta-thujone and camphor accounted for about 69% of the oil which contained more than a hundred compounds, most of which were present only in traces; 36 components were identified.

Constituents of Essential Oil of Artemisia arborescens.

By combination of capillary GLC and mass spectrometry it was possible to analyze the composition of the essential oil obtained by steam distillation from leaves and flowers of ARTEMISIA ARBORESCENS L. growing in Sassari (Osilo) in Sardinia. This oil is coloured blue by the presence of relatively high amounts (11.32%) of chamazulene, a substance with anti-inflammatory properties. The oil, after separation in fractions on a silica gel column, was investigated by means of capillary GLC and capillary GLC-MS. Thujone, camphor and chamazulene account for about 75% of the oil. Almost a hundred minor components were found by capillary GLC and 44 were identified.