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Current analytical methodology for iodopropynyl butylcarbamate (IPBC) analysis focuses on the use of liquid chromatography and mass spectrometer (LC-MS), but the high instrumentation and operator investment required has resulted in the need for a cost effective alternative methodology. Past publications investigating gas chromatography with electron capture detector (GC-ECD) for IPBC quantitation proved largely unsuccessful, likely due to the preservatives limited thermal stability. The use of pulsed injection techniques commonly used for trace analysis of thermally labile pharmaceutical compounds was successfully adapted for IPBC analysis and utilizes the selectivity of GC-ECD analysis. System optimization and sample preparation improvements resulted in substantial performance and reproducibility gains. Cosmetic formulations preserved with IPBC (50-100ppm) were solvated in toluene/isopropyl alcohol and quantified over the 0.3-1.3μg/ml calibration range. The methodology was robust (relative standard deviation 4%), accurate (98% recovery), and sensitive (limit of detection 0.25ng/ml) for use in routine testing of cosmetic formulation preservation.

The retention behavior in capillary supercritical fluid chromatography (SFC) of a range of ferrocene derivatives is demonstrated. Prediction of retention times and hence elution order of the ferrocene derivatives based on a knowledge of solute molar volume, solute solubility parameter and the physical parameters of the chromatography column system is shown to be feasible using this procedure.

Supercritical fluid extraction of cobalt ions was evaluated in terms of the ability of the process to extract, solvate, transport and to collect the metal species. The aim of the study was to ensure that a mass balance could be obtained for the metal before and after extraction with supercritical carbon dioxide (CO2). The stability of the ligand and resulting metal complex were assessed as was the synergistic effect of the presence of water in the extraction. Two widely used β-diketones, namely, acetylacetone (AcAc) and hexafluoroacetylacetone (HFAcAc) were chosen to extract spiked cobalt from the surface of stainless steel and >90% of the metal was extracted and collected using the HFAcAc ligand with supercritical CO2.

The solubility of 49 metal-containing compounds and 15 “free” ligands in supercritical fluid carbon dioxide is reviewed. Solubilities were found to range over eight orders of magnitude, with the highest value of solubility being 56 g l−1. Metals complexed with fluorine substituted ligands were found to be the most soluble, and metals complexed with phenyl-substituted ligands the least soluble. A general trend for increasing solubility with increasing oxidation state is observed and this is correlated with the increased number of coordinating ligands protecting the metal center from interaction with the supercritical fluid and also due to the increased number of solvation interactions with the increased number of ligand groups.

Real world samples which contain high concentrations of water and/or extractable material frequently cause intermittent or irreversible plugging of the flow control device during off-line supercritical fluid extraction (SFE). A supercritical fluid (SF) flow control/collection device has been developed which can simultaneously maintain the extraction flow-rate of the SF (±0.1 ml/min) and quantitatively (>90%) collect analytes as volatile as n-octane directly into an organic solvent. With this device, the extract is partially depressurized through a heated capillary restrictor and into a pressurized collection solvent, so that both temperature and pressure are used to maintain the solubility of the extract in the SF. The pressurized mixture is finally depressurized to atmospheric conditions using a backpressure regulator, so the extract can be recovered in the collection vial. Depending on the sample matrix, a restrictor heater temperature of 200 °C and a backpressure regulator with a heated (>5 wt% water in sample) or unheated (

A coupled supercritical fluid extraction-gas chromatography (SFE-GC) method has been developed for the quantitative extraction and analysis of gasoline and diesel range organics from real world environmental samples. Petroleum-contaminated samples containing gasoline- to diesel- and motor oil-range hydrocarbons (total hydrocarbon content typically ranging from 2 to 26 mgg) could be quantitatively extracted by a 15-min SFE-GC extraction using 400 atm (1 atm = 101 325 Pa), 60°C CO2. The SFE-GC hydrocarbon recoveries from real-world samples were comparable to those obtained by sonicating the samples in methylene chloride for 14 h, except for the gasoline recovery which was higher by SFE-GC analysis due to the more efficient collection of the more volatile analytes. Reproducibilities for replicate SFE-GC extractions and analyses were typically

Of 21 potential drying agents investigated, five (anhydrous and monohydrated magnesium sulfate, molecular sieves 3A and 5A and Hydromatrix) were able successfully to prevent restrictor plugging by water during off-line supercritical fluid extraction (e.g., 400 atm CO2 at 60°C) by retaining the majority of the water (but generally not the analytes of interest) in the extraction cell. Increasing the extraction temperature (e.g., to 150°C) or adding a polar modifier [10% (v/v) methanol] to the CO2 extraction fluid greatly reduced the amount of water the drying agents retained. However, when 10% (v/v) toluene was used for the extraction, the drying agents were able to retain the majority of the water (ca. 80% w/w). Polar and non-polar pollutants were quantitatively extracted from the wet drying agents (i.e., water present), but nearly all of the drying agents selectively retained at least one of the polar analytes if used dry (i.e., no water present), thus demonstrating the need for a spike recovery study to determine the potential for analyte loss. The successful drying agents eliminated restrictor plugging when used with moderately wet [ca. 20% (w/w) water at a 1:1 reagent-to-sample ratio] and very wet [ca. 90% (w/w) water at 4:1 reagent-to-sample ratio] samples without the need to heat the restrictor or the collection solvent.

Fused-silica restrictors used for off-line supercritical fluid extraction (SFE) frequently break when extractions are performed with polar supercritica

The development of quantitative supercritical fluid extraction (SFE) methods for the recovery of organic pollutants from environmental samples requires three steps: quantitative partitioning of the analytes from the sample into the extraction fluid, quantitative removal from the extraction vessel, and quantitative collection of the extracted analytes. While spike recovery studies are an excellent method to develop the final two steps, they are often not valid for determining extraction efficiencies from complex real-world samples such as soils and sediments, exchaust particulates, and sludges. SFE conditions that yield quantitative recoveries of spiked analytes may recover < 10% of the same analytes from real-world samples, because spiked pollutants are not exposed to the same active sites as the native pollutants. Because of the heterogeneous nature of environmental samples, the partitioning step may be controlled by analyte solubility in the extraction fluid, kinetic limitations, and/or the ability of the extraction fluid to interrupt matrix-analyte interactions. While the interactions that control SFE rates from heterogenous environmental samples are not well understood, a generalized scheme for developing quantitative SFE methods is proposed based on interactive considerations of the collection efficiencies after SFE, fluid flow parameters in the extraction cell, analyte solubility, extraction kinetics, and analyte-matrix-extraction fluid interactions. The proposed development scheme includes increasing SFE extraction rates by the use of more polar fluids than CO2 such as CHClF2, the addition of organic modifiers to CO 2, and the use of high temperature extractions with pure CO2. Validation of quantitative extractions based on multiple extraction methods (SFE followed by liquid solvent extractions) is also described.

Smith, R.M. and Burford, M.D., 1993. Comparison of flavanoids in feverfew varieties and related species by principal components analysis. Chemometrics and Intelligent Laboratory Systems, 18: 285–291. The fingerprint patterns of the high-performance liquid chromatographic separations of the flavanoids from 106 feverfew [Tanacetum parthenium (L.) Schultz Bip.], tansy (Tanacetum vulgare L.) and German chamomile (Matricaria chamomilla L.) plants and four commercial feverfew products were correlated by principal components analysis. It was possible to distinguish the three medicinal herb species by using the first, second and third principal components and to demonstrate that the commercial products contained feverfew.

Supercritical carbon dioxide was used to extract the sesquiterpene lactone parthenolide, which is reported to be the active component of the medicinal herb feverfew ( Tanacetum parthenium ), from dried plant material for gas-liquid chromatographic analysis. The extracts also contained significant amounts of camphor and chrysanthenol acetate. The pressure and densities required for quantitative extraction and the methods of sample collection were studied. The addition of methanol or acetonitrile as modifiers in the carbon dioxide gave higher yields of parthenolide bu the extractions were less selective and considerable amounts of co-extractives were obtained. By employing a trapping column made of cellulose or silica the purity of the extracts could be improved and a practical method for the rapid isolation of parthenolide is described.

Real-world environmental samples which contain high concentrations of water and/or extractable matrix components frequently cause intermittent or irreversible plugging of capillary flow restrictors during off-line supercritical fluid extraction. Heating the entire restrictor at 50°C produces a constant extraction flow-rate (± 0.03 ml/min) for such samples, but poor collection efficiencies (30–65% recovery for polycyclic aromatic hydrocarbons) were obtained because the supercritical fluid could not be depressurized directly into the collection solvent. While the collection efficiency was improved (80–90%) by nebulizing an organic solvent with the restrictor effluent, a simpler method was to heat all but the last 3 cm of the restrictor and to depressurize the extract directly in the collection solvent. Depending on the sample matrix, restrictor heater temperatures ranging from 50 to 200°C were required to avoid restrictor plugging. With proper heating, constant extraction flow-rates (± 0.07 ml/min) and high collection efficiencies (90–100%) for polycyclic aromatic hydrocarbons and n -alkanes as volatile as n -octane were achieved.

α-Cellulose has been used as a model plant matrix to investigate the conditions required to optimize the supercritical fluid extraction of typical plant constituents, limonene, caryophyllene, carvone, eugenol and santonin, using carbon dioxide as the extraction medium. The conditions required for the successful recovery of the analytes were monitored by gas-liquid chromatography. Timed recovery studies enabled differences in the rates of extraction to be determined to ensure that sufficiently long extraction runs were used. Subcritical and supercritical extractions over the ranges −10 to 80°C and 50–250 bar were examined and 250 bar and 40°C were chosen as the optimum conditions. The effects of the addition of modifiers to the supercritical fluid were also examined. The work also demonstrated that increased selectivity for polar analytes such as lactones could be obtained by trapping the extract on a silica column coupled with selective elution.

Supercritical fluid extraction (SFE) collection efficiences of 66 compounds with a wide range of volatility and polarity were examined. Good collection efficiencies required efficient partitioning of the analyte into the collection solvent after depressurization, and factors including collection solvent polarity and temperature were found to be more important than collection solvent volume and height. Heating the collection solvent with a heat gun to avoid plugging of the outlet restrictor resulted in 20−50% losses of the more volatile analytes, while > 90% trapping of all test analytes could be attained by controlling the solvent temperature at 5°C. Extraction cell geometry (“long, narrow” versus “short, broad” vessel) at constant internal volume and the orientation of the extraction cell were found to have negligible effects on the extraction rates of polycyclic aromatic hydrocarbons (PAHs) from railroad bed soil and flavor and fragrance compounds from lemon peels. The supercritical fluid flow-rate also had little effect on the extraction rate of native PAHs provided that it was sufficient to sweep the cell dead volume every ca. 3 min.

A method is described for the rapid separation of cells from their suspending medium with only 1 5 th to 1 30 th the amount of contamination from the medium as with conventional centrifuging. The principle is to interlayer between the cells and the medium upon centrifuging an immiscible liquid whose density lies between that of the cells and medium. Quantitative measurement of the amount of contamination of the cells by the medium which does occur is achieved by adding a nonpermeable radioactively labeled substance to the suspension prior to centrifugation.