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In the first phase of our studies of the contaminants and their levels in curbside-collected poly(ethylene terephthalate) (PET) subjected to a recycling process, we analysed the washed and dried, shredded PET (flake). Of the semi-volatile contaminants found, 26 were below the US FDA threshold of 215 ppb and six were above. Additionally, it was found that surface levels of contaminants far exceeded average concentrations in the bulk of the flake, raising questions about the appropriateness of sampling procedures. In this second phase (again using dichloromethane Soxhlet extractions for the most part), we examined contaminant levels after the flake was subjected to vacuum extrusion, to complete the recycling process. Initially amorphous, extruded pellets were annealed to introduce crystallinity and allow grinding, in order to examine the effect of particle size. Much reduced concentrations of contaminants were found (all 300-425 μm and >425-700 μm), approximately 8 h were required for the unground annealed pellets.

The dihydrofolate reductase inhibitors (DHFRIs) are a group of antibiotic compounds with closely related chemical structures. A previous attempt to separate the eight compounds by CZE was successful, but only at low pH (2.1) and high buffer concentration (250 mM phosphate). As a result, baseline noise was high. Additionally, baseline resolution was not quite achieved and the separation took 25 minutes. However, the size-based separation indicated that reversed-phase HPLC might be a good alternative. A three-dimensional overlapping resolution mapping (ORsM) scheme utilised pH, flow rate and percentage organic modifier (for both methanol and acetonitrile). Clear generalised outcomes were observed under isocratic conditions. At higher pHs, where the analytes were largely unionised, retention was excessive. At higher percentages of MeOH or ACN, the more-difficult-to-separate components were poorly resolved. On the other hand, low pHs (2.5 in 50 mM phosphate) with low percentages of the organic modifiers (7% ACN or 11% MeOH) but high flow rates (2.3 mL min−1) yielded better than baseline resolution in 17 minutes. A partially optimised gradient run (at pH 6.5) again yielded far better than baseline resolution in 12 minutes, but required 4 minutes re-equilibration. Hence, the HPLC separations are superior to the CZE separation in all of runtime (40%), resolution and limit of detection (down by 6).

Part I of this study showed that washed and dried, shredded poly(ethylene terephthalate) (PET) (flake) obtained from curbside collection when Soxhlet extracted contained 26 semivolatile contaminants below the US FDA threshold of 215 ppb and six above this level. This paper reports the validation of the Soxhlet extraction technique by comparison with total dissolution with trifluoroacetic acid (TFA). The work was carried out for two of the three particle size ranges obtained by grinding the PET flake (300-425 and 425-700 microm) and for the unground flake. Further validation was undertaken by comparison of contaminant levels determined by total dissolution with TFA and sonication with dichloromethane (DCM) using flake ground to the 0-300 microm size range. The levels of contaminants increased with decreasing particle size range, but X-ray diffraction measurements of degrees of crystallinity were similar for each PET particle size range, thus showing that the differences in contaminant levels were not due to variable percentages of the amorphous material from the tops and bottoms of shredded bottles, relative to the amounts of crystalline PET from the mid-sections of the bottles. Hence, it was postulated that the variations in contaminant levels were due to selective grinding of the more highly contaminated surfaces, whilst the larger particles incorporated the less contaminated interior material. The grinding was also strongly selective with respect to the amorphous flake. Analysis of the segregated amorphous and crystalline flake phases indicated that many contaminants were similarly absorbed into both phases, whilst some were preferred by the amorphous PET and others were preferred by the crystalline PET.

A series of eighteen peptides have been modelled. Of the 380 low-energy viable conformers generated, 64 were selected, with 2–5 per peptide representing the range of structures and size. Using the results of previous investigations of this peptide group, it was possible to place an upper limit to the extent of hydration for each peptide. The modelled peptides were then hydrated in stepwise fashion. From the volumetric and dimensional data derived, in conjunction with published mobilities, the relationship between electrophoretic mobility (μ ep ) and the hydrodynamic radius (r) was used to objectively test the fit between the experimental (μ ep ) data and and the modelled size parameters over the range of hydration. Where the fit was tightest it was presumed that the fraction of the maximum reasonable hydration best represented the average degree of hydration of the set. Using ellipsoidal volumes, Connolly surfaces and excluded volumes the average degree of hydration was found to be in the mid range considered and corresponded to the mean of the bimodal distribution of hydration for the individual peptides according to charge-based calculations. For a peptide with two positive charges and a partial negative charge on the carboxy residue (pH=2.5), about 15 waters of hydration are indicated. With 3, 5 and 6 positive charges, the estimated waters are 28, 48 and 85, respectively. Van der Waals volumes were not helpful as the precise summation of the volumes associated with each bonded atom is a poor reflection of the effective volume of the migrating peptide. Conformational changes are examined as a function of the progressive hydration, and, as might be expected, the greatest changes occur in the early stages of hydration.

From the published electrophoretic data for a set of 58 peptides at pH 2.5 we have determined the excess hydration required to correct the deviations of the 31 higher-charged peptides from the Offord plot for the 27 singly-charged peptides. These values of the excess hydration were then used to test physical models by regression analysis. The dominant variable is the total excess positive charge, but the number of excess single positive charges and the number of pairs of positive charges – both at the end and internally – were significant determinants. The effect of acidic side chains was ambiguous throughout the analyses and this was presumed to arise from the ability of carboxy groups to be the sites of additional hydration or to diminish hydration via internal bonding with amino groups. A hydrophobicity index was included in he analysis, but surprisingly this too had little effect. In the last stage of the regressions, we also included coding for secondary structure within the peptides. This increased R2 for the plots of the excess hydration versus values calculated from the regression constants (Y) from 0.95 to 0.97. Some solvation relationships were particularly good at modelling the hydration of the smaller, lesser-charged peptides, whilst others excelled in the opposite direction. The final model appeared to deal equally well with both extremes, but is not sufficiently sensitive to allow for all of the variations between peptides. As a result, the excess hydration was modelled very well for many of the peptides (±1–2 waters over the range of excess hydration form 5–276), but poorly for a few (± 100–200%). It was not possible to find another set of peptides that could be independently analysed in a similar fashion and compared. However, the regression constants were applied to an alternative set. Although appearing to fall in a generally reasonable range, various tests of the resultant calculated values indicated that this application was not valid. The second set of peptides were much more hydrophilic and the number of amino acid residues with an extended secondary structure appeared to be a contributing factor.

In the previous paper on the Ag+-HPLC of conjugated linoleic acids (CLAs) on a silica-based stationary phase, we examined the relative retentions of the CLAs, their methyl esters (CLAMEs), and stearic acid. The retention of the CLAs far exceeds the sum of the retention of the CLAMEs and stearic acid. In this paper we isolate the interactions at the silica surface by determining the retentions of the same compounds on the NH4+ cation exchanger that is the precursor to the Ag+ column in the manufacturing process. On the NH4+ column, the CLAMEs are very weakly retained, but the sum of the retentions of the CLAMEs plus stearic acid is equal to that of the CLAs. It was determined that stearic acid is retained to the same degree on both the NH4+ and Ag+ stationary phases. By implication, the CLA carboxylic acid functionality does not interact with Ag+ and thus three-centre complexes of the Ag+ with the CLA π bonds and carboxyl group do not occur. (Independent supporting evidence is also presented.) A model for CLA retention on the Ag+ stationary phase that explains the synergy of retention is presented. It involves a random arrangement of collapsed Ag+ alkyl sulphonate bonded phase on the silica surface. The nature of retention on the NH4+ stationary phase is also discussed. Partial separation of the CLAs on the NH4+ stationary phase shows that π bond interactions with the silica surface also contribute to the separations of the CLAs, the CLAMEs, and other unsaturated analytes. As was found on the Ag+ column in the absence acetonitrile, normal phase elution occurs and log k′ versus log (% strong solvent) plots for all analytes are linear on the NH4+ column. (Where the specific displacement mechanism of unsaturates from the Ag+ by ACN was present, the log-linear plots were straight lines.)

During the development of a method for the direct analysis of the conjugated linoleic acids (CLAs) in their free fatty acid form, it was necessary to include a competing acid (acetic acid) in the hexane-based mobile phase in order to achieve resolution of the isomers in a reasonable time. Thus it was clear that the CLAs were retained by two mechanisms. In this study we examine the relative retentions of the CLAs, their methyl esters (CLAMEs, which is the form generally analyzed), and oleic and stearic acids. The primary aim was to investigate the nature of CLA retention in terms of the Ag + -π bond interactions (that might be approximated by the retention of the CLAMEs) and the -COOH-surface silanol hydrogen bonding that should be the same as stearic acid, if the retention mechanisms are independent. Allowing for some retention of the ester group in the CLAMEs on the silica, it may have been expected that the sum of the retention of the CLAMEs and stearic acid would slightly exceed that of the CLAs. On the contrary, it was found that the retention of the CLAs far exceeded the sum for the CLAMEs and stearic acid. Some synergy is suggested, rather than a third retention mechanism.

For the conjugated linoleic acids (CLAs), we present the effects upon retention of the progressive addition of acetonitrile (ACN) to hexane-based mobile phases that contain background concentrations of acetic acid (AA) of 1.5, 2.0, and 3.0% by volume. An analysis of the variation in resolution across the range of elution conditions leads to unambiguous conclusions about the optimum conditions for separation and quantitation. Lower AA concentrations (≤1.5%) combined with low to moderate amounts of ACN (0.005-0.03%) yield good and uniform resolution amongst the major group of cis,trans/trans,cis (c,t/t,c) isomers that are believed to contain the demonstrated, desirable biological effects. For this range of %ACN, these major isomers elute around 22 and 16 minutes, respectively, and in the latter case the isocratic analyses are completed in 24 minutes. Extrapolations of the two sections of the linear dependence of the log k' versus %ACN plots back to zero %ACN yield data points for each background %AA that are compared with the directly measured retention of the CLAs in the presence of only AA as the strong solvent. The upper linear sections clearly relate to total retention due to all adsorption mechanisms and the extrapolations agree with the direct measurements. The lower linear sections appear to relate to that component of retention due to interaction between the CLA π bonds and Ag + and the extrapolation thereof to the ability of AA to overcome this adsorption. These intercepts appear to reflect the diminishing general solvent strength for elution of the CLAs due to the Ag + -π bond adsorption as %AA decreases.

During the development of a method for the direct analysis of the conjugated linoleic acids (CLAs) in their free fatty acid form, we observed a two-stage variation in the retention of the CLAs as a function of solvent strength, both for acetonitrile (ACN) in the presence of acetic acid (AA, the competing acid) and vice versa. It was assumed that this two-stage retention would also apply in the absence of ACN. In this study we examine the patterns of retention of the CLAs and their methyl esters (CLAMEs). The two-stage retention pattern is found to apply only in the presence of the mixed strong solvents (AA and ACN). It is also found that the observed retention patterns do not fit those predicted by theories of LSC retention and elution. Rather, it is the presence or absence of ACN (in conjunction with the highly specific Ag + -π bond interactions) that determines the form of the retention variation in response to solvent strength. Equivalent behavior is observed for the CLAs and the CLAMEs. The specific displacement mechanism operative in the presence of ACN is replaced by a generalized solublization mechanism in AA modified mobile phases an order of magnitude more concentrated in the strong solvent.

A previous study has demonstrated that the average electrophoretic behaviour (mobilities, μep of eighteen peptides were well described by the inverse square law: μep ∝ l/r2 (wherer is the hydrodynamic radius). However, examination of the dependence of μep, upon the magnitude of the charge and its distribution led to the conclusion that deviations from the averaged behaviour arose from a charge-induced volumetric effect.

Two electrically neutral analytes previously observed to be separated from the neutral marker in capillary zone electrophoresis (CZE) experiments [sulphanilamide (SAA) and sulphaguanidine (SGW)] have been examined to determine the basis for separation. The degree of separation increases markedly with buffer concentration and improves with increasing field strength. On the basis of the apparent electrophoretic mobilities in conventional CZE, migration times in a zero EOF environment were calculated for SAA, SGW and six other sulphonamides that were known to be ionized. These six markers were used to test the legitimacy of our predictions and to correct for small discrepancies between the predicted and observed migration times. It was concluded that SAA and SGW have negligible electrophoretic mobilities and that they are retained in the electrical double layer close to the capillary wall. A mechanism for adsorption is proposed and the generality of the phenomenon is discussed.

Eighteen peptides have been modeled. From the volumetric data derived, and published mobilities, the relationship between electrophoretic mobility (μep) and the hydrodynamic radius(r) has been examined. Objective testing with respect to size has been achieved by the log-log version of generalized relationship. (1) From the gradient of the plot versus log r(2.02) there is good support for the inverse square law (μep α 1/r2). Equivalent calculations using molecular weight (Mr) and the number of amino acid residues (n) similarly lead to μep α 1/M r 2/3 and μep α 1/n2/3, respectively. However, the strength of the correlation is diminished as the precision of the representation of size is degraded. (2) An examination of the effect of size at fixed charge and a statistical analysis of the charge distribution on the peptides leads to the conclusion that deviations from the averaged behaviour arise from a charge-induced volumetric effect. Taken together, (1) and (2) indicate that whilst net charge and total size can describe average electrophoretic behaviour well, these parameters are inadequate to describe the specific mobilities of individual analytes. Objective analysis of alkylpyridine data indicates μep α 1/rx where x=2.6–2.8 (depending upon the nature of the r values utilized), but is certainly ≠1 as may have been presumed. A very small range of values may be responsible for this surprising result.

Silver-ion high-performance liquid chromatography was used to fractionate a mixture of conjugated linoleic acid (CLA) isomers (as the free fatty acids, CLAFFA) in commercial CLA mixtures and biological samples. Due to the unchanged retention mechanism, it was assumed that the elution order of the isomers remained the same as that of methyl esters separated on the same column. The most abundant isomers, cis/trans 10,12-18:2 and cis/trans 9,11-18:2, were separated better as free acids on a single column than in the methyl ester form. Quantification of the CLA standard was used as the reference profile to evaluate different methylation methods commonly used to prepare CLA methyl esters for quantitation. Acid- and vuigi base-catalyzed derivatization methods resulted in CLA intraisomerization and losses in total conjugated dienes content. Acid (HCl and BF3) methylations significantly elevated the level of trans,trans isomers and significantly reduced the cis/trans isomers. Base methylation, tetramethylguanidine/methanol, resulted in loss of trans,trans isomers, and a substantial loss of total underivatized conjugated dienes. Other catalysts such as the trimethylsilyldiazomethane produced additional peaks of unidentified artifacts. The analysis of CLAFFA appears to provide more accurate quantification of CLA isomers in commercial and biological samples.

The paper starts by looking at the competing paradigms in pursuing nanotechnology, namely the top–down approach originating from microelectronics, and the bottom–up approach inspired by biological sciences. This almost dogmatic dichotomy uncovers the challenges posed by interdisciplinary and transdisciplinary knowledge transfer. Several possible knowledge mechanisms are proposed using the analogy with the classical transfer phenomena theory, namely “diffusional”, “convective”, “turbulent”, “radiative” and “interphasic” transfer mechanisms. Furthermore, possible modes of knowledge production are outlined. These possible mechanisms for knowledge transfer and production are then analyzed in the context of micro-electro-mechanical systems and nanotechnology development. This analysis is extended to formulate a framework for facilitating knowledge transfer and production in nanotechnology.

Summary Fatty acids (FAs) and fatty acid residues are generally methylated and analyzed by GC. The reasons for this are partly historic and partly because of the sensitivity advantage of flame ionization detection over UV absorption by the carboxylic acid functionality in saturated FAs. However, for strongly absorbing unsaturated acids such as the conjugated linoleic acids (CLAs), the sensitivity advantage is greatly reduced. Hence there seems little reason to waste time and introduce errors associated with methylation. Remarkably, this appears not to have been recognized. In this paper we describe our method development for the analysis of underivatized CLAs by silver ion HPLC separation on the ChromSpher Lipids column. Using mobile phases previously optimized for the analysis of the methylated CLAs, retention is excessive and a competing acid is required. Various combinations of small concentrations of acetic acid (3.0 ‐ 2.5%) with acetonitrile (0.0 ‐ 0.025%), respectively, yield similar resolution and run times. As well as its role as a competing acid, acetic acid acts as a general strong solvent and thus can be used alone as a modifier (without acetonitrile). However, for slightly shorter run times a mobile phase of 2.5% acetic acid and 0.025% acetonitrile was chosen as the optimum mobile phase for analysis. The separation of the free CLAs is clearly superior to those previously published and obtained in this study for the methylated CLAs. The additional specific strong interactions of the underivatized CLAs seem certain to be due to hydrogen bonding between the CLA carboxylic acid functionality and the large number of residual silanols on the surface of the silica support of the stationary phase.

Five sulphonamides spanning a range of initial degrees of ionisation have been used as probes for the study of the mechanisms of electrophoretic mobility modification caused by increasing buffer concentrations (5–210 mM sodium phosphate) in capillary zone electrophoresis (CZE). Partition experiments at the CZE operational pH and a second pH where the analytes are uncharged permits independent determinations of the salt and temperature effects upon ionisation. At the CZE temperature, the underlying salt effects due to nonideal solute–solvent interactions are demonstrated. These are selective and indicate that the buffer concentration may be manipulated to facilitate resolution of analytes with differing degrees of ionisation. These selectivities are heightened by Joule heating. At elevated temperatures, the relative effects upon ionisation and viscosity were determined. These magnitudes were then combined and used in conjunction with the deviations in electrophoretic mobilities from the extrapolated behaviour of dilute buffers to estimate mean internal capillary temperatures.

Derivatisation of amine-containing analytes with 9-fluorenylmethyl chloroformate (FMOC) to form fluorescent adducts requires a large excess of FMOC. This excess hydrolyses to form FMOC-OH, which is also fluorescent. Solvent extraction has been investigated as a means of isolating the sulphamethazine (SMZ) adduct (FMOC-SMZ) from the hydrolysis product in order to perform rapid spectrophotometric or spectrofluorimetric assays. However, even under the most favourable pH conditions possible, FMOC-OH was not totally removed. Attempts to enhance the separation by reaction of FMOC-OH with 1-ethoxy-4-dichloro-S-triazinylnaphthalene (EDTN) or by acetylation were also unsuccessful. On the other hand, reaction of FMOC with mixed substrates, followed by two pentane extractions to remove the excess FMOC and direct injection into an HPLC provides the desired separations on a reversed phase column (RPLC) with methanol-modified, (pH 3.5) phosphate buffers. FMOC-SMZ is readily separated from FMOC-OH under all elution conditions, from the FMOC-amino acids (under gradient conditions or isocratically up to 75% methanol), and from other FMOC-sulphonamides and FMOC-dihydrofolate reductase inhibitors (isocratically up to 70% methanol). Hence conversion to the FMOC derivatives permits SMZ to be separated from all of the potential interferants tested by isocratic elution with 70% methanol in RPLC. Analysis for the amino acid derivatives of FMOC may be done without interference from SMZ in samples.

An examination of the derivation of the equation relating electrophoretic mobility (μep) to charge and the hydrodynamic radius (r) shows that the 1r dependence arises from an approximation. A more generalised approach yields a 1r2 dependence and includes the known 1√I dependence as well. Nine totally ionised sulphonamides have been used to test the proposed relationship between μep and r, and at each of four buffer concentrations utilised the correlations favour 1r2. For large molecules, μep has frequently been demonstrated to be proportional to aMr23, which can be equivalent to 1r2. However, it has been suggested that there may be a transition from 1r dependence for small molecules to a 1r2 dependence for large molecules. Hence we have used literature data for a series of twenty-two peptides varying in size between 3 and 39 amino acids long to test that theory and the generality of the 1r2 dependence. The calculations indicate a consistent dependence upon 1r2.

Of the twenty-two sulphonamides and three commonly used dihydrofolate reductase inhibitors investigated for reverse phase separation in previous studies, the recoveries of five representative drugs from the stationary phase have been examined. Sulphanilamide, sulfisomindine, sulphaquinoxaline, diaveridine and pyrimethamine were chosen. Peak areas off the analytical column were compared with those obtained by substitution with stainless steel tubing. After careful correction for flow rate differences where necessary, 100% recoveries were indicated. As a further check, Maloprim tablets were assayed for pyrimethamine and the analysed results were found to be (99.1 ± 2.9)%. Limits of detection (LOD) for aqueous standards varied from 0.67 (for sulphanilic acid) - 0.03 μg ml/−1 (diaveridine). The linear dynamic range extended from the LOD for each drug to

The effect of tertiary butyl ammonium phosphate as a competing base has been investigated in the reverse phase separation of twenty-two sulphonamides (SFA) and three commonly used dihydrofolate reductase inhibitors (DHFR). At the concentrations of t-butyl ammonium phosphate examined, the retention of the DHFR was dramatically reduced, but did not aid the separation. The effects on the SFA were inconsistent with the known pKa, l data and suggested either more complex mechanisms of interaction with the stationary phase or some doubt regarding the pKa, l values.

Twenty-two sulphonamides and the three commonly used dihydrofolate reductase inhibitors have been subjected to an investigation of retention behaviour on a silica based reversed phase. Effects of variation in the percentage of methanol and the pH have been determined isocratically and the methanol gradients developed have been modified by variations in the concentration of the phosphate buffer. Significant variations in retention behaviour were observed such that the majority of combinations of drugs could be screened for. No set of conditions studied gave rise to a total separation of all drugs, but around twenty drugs were commonly resolved.

Acetonitrile has been investigated as the organic modifier for the reverse phase separation of twenty-two sulphonamides and three commonly used dihydrofolate reductase inhibitors. Isocratic analyses indicate that 10% acetonitrile is approximately isoeluotropic with 16% methanol. This allows a comparison of selectivities. Relative to methanol, in gradient elution involving acetonitrile only, unfavourable changes in the relative retentions of some pairs of analyses outweighed the advantages of favourable selectivities. Insertion of acetonitrile into methanol gradients did not produce the improved separations expected. However, the imposition of a program of reduced flow upon an established methanol gradient demonstrated significantly increased efficiencies in the front half of the chromatogram. This permitted the resolution of the first thirteen compounds, including the difficult-to-separate pair of sulphathiazole and sulphapyridine.

For a course built around a year of Industry Based Learning (IBL), devising an honours stream within the same four‐year time span required part‐time study during IBL. In the case of students undertaking IBL internationally, this neccessitated the provision of units of study for distance learning. However, in some units appropriate learning resources were not in existence. The solution to this problem was to video‐tape a chemistry lecture unit live. This led to a second potential problem. Was the video‐taped lecture unit a suitable learning resource? Hence the unit was trialled on local students. After live lectures or independent video‐tape learning, students' results on an identical examination were internally standardised to their overall performance. These standardised results showed clear‐cut improvements when video‐taped lectures were utilised. Thus, for a (special) group of students studying chemistry at a distance, the generalised results of the trial suggest the telelecture mode of presentation to...

CZE was used as a method to separate eight dihydrofolate reductase inhibitors (DHFRI). Separation of the eight DHFRI was difficult to achieved and occurs only under very specific conditions. Baseline resolution occurred in 250 mM phosphate buffer of pH 2.1 at 13 kV. In an attempt to understand the mechanism of separation, pKa,1 values have been determined and the effective hydrodynamic radii estimated by modeling the molecules. The consequential plot of Z/r versus the measured electrophoretic mobility gave a good linear correlation, thus demonstrating the fundamental nature of the separation mechanism.

Twenty-two sulphonamides and three dihydrofolate reductase inhibitors (DHFR) were included in this study. At pH 7.5, eighteen drugs were resolved in 22 min. Above pH 7.5 the DHFR are not resolved and the pH range of 7-7.5 was found to be optimal. Around pH 7, where the degree of ionization of the SFA is highly variable, pKa and migration time are strongly correlated. Increasing phosphate buffer concentration from 25-100 mM generally improves resolution but increases analysis times. A good correlation between analyte mobility and the ratio of net charge to molecular weight indicates that this ratio may be used as a quick guide to the possibility of separation of related compounds. Our secondary objective was to compare the lead time and effectiveness of CZE with LC. It is clear that method development is much more rapid in CZE but with a sufficiently diverse group of compounds, CZE can be incapable of providing a full analysis without gradient control. Nonionized compounds are not separated at one extreme, and excessively mobile species may not emerge in a reasonable time, or, may migrate to the wrong electrode.

Activity-guided fractionation was used to determine the antibacterial component of an ethanolic extract of the leaves of an Australian native medicinal plant, Eremophila duttonii F. Muell. (Myoporaceae). The extract, previously shown to have activity against Gram positive bacteria, was shown to have activity against additional Gram positive bacteria, including Clostridium perfringens, C. sporogenes and Listeria monocytogenes. Thin layer chromatography (TLC) was used to separate the extract into seven coloured fractions in visible light, one of which was shown by bioautography to contain antibacterial activity. Recovery of the component from the TLC plate and testing for antibacterial activity using a plate-hole diffusion assay supported this result. The purity of the component was verified by high-performance liquid chromatography and a time-kill experiment indicated that the purified component showed identical bactericidal activity to the whole extract. TLC spray reagents indicated that the component was a sterol, terpene or sugar but not a flavonoid, while the pigmented nature suggested a carotenoid.

Conjugated linoleic acids (CLA) have been shown to decrease body fat content in pigs. It is possible that feeding pigs diets rich in CLA may increase carcass lipid CLA to levels that could provide health benefits when included as a part of a healthy diet. Therefore, the aim of the present study was to determine whether dietary CLA supplementation has any effect on the fatty acid composition of subcutaneous and intramuscular adipose tissue in pigs. Thirty-five female cross bred (Large White×Landrace) pigs (initial weight 57·2kg and initial P2 back fat 11·5mm) were used in the present study. Pigs were housed individually and randomly allocated to one of six dietary treatments (0·00, 1·25, 2·50, 5·00, 7·50 and 10·00g CLA55 (55g CLA isomers/100g total fatty acids; Natural Lipids Ltd, Hovdebygda, Norway)/kg) and fed their respective diets for 8 weeks. Twelve CLA isomers in the diet and in pig tissue lipids were separated by Ag+-HPLC. CLA was incorporated at fivefold higher levels in subcutaneous fat as compared with intramuscular fat and in a dose-dependant manner. Overall, the transfer efficiency of CLA was maximized at 5·00g CLA55/kg. However, there was clear selectivity in the uptake or incorporation ofcis,trans-9,11 isomer over thetrans,cis-10,12 isomer. In general, CLA supplementation produced significant changes in skeletal muscle and adipose tissue fatty acid composition, indicating that dietary CLA had a potent affect on lipid transport and metabolismin vivo. Significant increases in myristic, palmitic and palmitoleic acids and a reduction in arachidonic acid were observed, suggesting an alteration in activity of Δ5-, Δ6- and Δ9-desaturases in pig adipose tissue. In conclusion, feeding pigs diets supplemented with CLA increases carcass lipid CLA, but also results in changes in the fatty acid profile in pig fat that could potentially outweigh the benefits of CLA.

The aim was to determine which contaminants were present in washed and dried shredded poly(ethylene terephthalate) (PET, flake) obtained from curbside collection and whether the concentrations were above the US FDA threshold of 215 ppb. Thirty-two semi-volatile contaminants were extracted from the treated flake by Soxhlet extraction using dichloromethane as a PET swelling solvent and gas chromatography-mass spectrometry (GC-MS) was used for identification and quantification. Soxhlet extraction of flake ground to 0-300 pm was effectively completed in 24 h, whereas sonication reduced the extraction time to 3 h. In contrast, Soxhlet extractions of flake ground to a larger particle size range (300-425 pm) were completed in 4 h, possibly due to less aggregation in the extraction thimble. The levels of 26 contaminants were below 215 ppb, but six were not. Dodecanoic acid was present at about 1200 ppb, 2-butoxyethanol was approximately 1000 ppb, limonene, benzophenone and methyl salicylate were above 800 ppb, and 2-methyl-naphthalene near 215 ppb.

Thirty female Large White × Landrace pigs (average weight 57·2 (SD 1·9) kg) were allocated to one of six dietary treatments containing 0, 1·25, 2·5, 5·0, 7·5 or 10·0 g 55 % conjugated linoleic acids (CLA) isomers (CLA-55)/kg diet and fed for 8 weeks. Each pig was scanned at 0, 28 and 56 d and again at post slaughter using dual-energy X-ray absorptiometry (DXA) to determine the temporal pattern of body composition responses. Values determined by DXA were adjusted using regression equations generated from validation experiments between chemically and DXA-predicted values. Overall, there was a significant linear reduction in fat content with the increasing levels of CLA in the diet (P=0·007,P=0·011,P=0·008 at week 4, week 8 and for the carcass, respectively). The greatest improvement was recorded at the early stages of CLA supplementation and for the highest dose of CLA (week 4, −19·2 % compared with week 8, −13·7 %). In the first 4 weeks of feeding CLA, pigs receiving 10 g CLA-55/kg diet deposited 93 g less fat/d than pigs fed basal diets (P=0·002) compared with only 6 g less fat than control animals in the final 4 weeks. Lean content and lean deposition rate were maximised at 5 and 2·5 g CLA-55/kg diet for the first 4 weeks (P=0·016) and the final 4 weeks of treatment (P=0·17), respectively. DXA estimates of bone mineral content and bone mineral density were not affected by CLA supplementation throughout the experiment. These data demonstrate that dietary CLA decreases body fat in a dose-dependent manner and that the response is greatest over the initial 4 weeks of treatment.

A molecular modeling package has been used to systematically hydrate a series of previously built peptides. The volume data derived have been used with the log-log form of the inverse square law and published electrophoretic mobilities to test for the most likely states of hydration. Starting with the bare peptides and increasing hydration, however, the strength of correlation diminishes, indicating that the average electromigrating peptide is not extensively hydrated. The shapes of the peptides are predominantly oblate ellipsoidal, but generally do not deviate significantly from spherical and progressive hydration increases this trend. Thus, shape correction does not play a significant role in the calculations.

The molecular radii (r) of a series of peptides have been determined by molecular modeling. With these data, it is shown that electrophoretic mobility (mu(ep)) is proportional to 1/r2, and that the dependence presented in textbooks (mu(ep) infinity 1/r) is wrong. Use of the approximately equivalent, mass-based Offord equation is discussed, and other relevant considerations are presented.

The objective of this study was to examine the extension of supercritical fluid extraction (SFE) to the extraction of polar drugs. The ultimate aim was to extract veterinary residues from food animal products and thereby demonstrate the versatility of SFE. This technique is shown to have many facets that require careful thought and understanding if it is to be successfully used. Our initial studies indicate that polar drugs may be readily solubilized from relatively inert matrices such as sand, with high recoveries and very little discrimination between related compounds while using only moderate extraction conditions and times. SFE of the same drugs from spiked chicken liver and swine muscle is significantly more difficult and requires more drastic conditions. Close to complete recoveries are achieved for some drugs, while considerably less is found in the worst case. For sulphamerazine, sulphamethizole, sulphamethazine, sulphamethoxypyridazine, sulphamethoxazole, and the major metabolite N4-acetyl-sulphamethoxazole, the recoveries are 97, 66, 94, 79, 53, and 65%, respectively, from spiked liver and 95, 27, 86, 91, 96 and 70%, respectively, from spiked swine muscle. Incurred sulphamethazine is recovered from swine muscle in good general agreement with the reference values provided.

One constraint facing the pig industry is that ad libitum feeding can often result in high levels of body fat and technologies which can reduce the ratio of lean to fat deposition in the pig are continually being explored. Conjugated linoleic acids have been shown to decrease body fat content in pigs. Therefore, the aim of this study was to determine whether dietary conjugated linoleic acids supplementation has any effect on meat quality and carcass characteristics in finisher pigs. Sixty female crossbred (Large White × Landrace) pigs (average initial weight 56.6 ± 1.9 kg and average initial P2 backfat 11.4 ± 1.3 mm) were used in the present study. Pigs were individually housed and randomly allocated to 1 of 6 dietary treatments: 0, 0.125, 0.25, 0.50, 0.75 or 1.0% (w/w) of conjugated linoleic acids-55. The wheat-based diets were formulated to contain 14.3 MJ DE and 9.3 g available lysine per kg and were fed ad libitum for 8 weeks. Pigs were slaughtered and meat quality was determined on the longissimus thoracis using standard techniques. Dietary conjugated linoleic acids reduced subcutaneous back fat in a linear manner with effects being most pronounced in the middle back fat layer. There was also a linear (P

The effects of conjugated linoleic acid (CLA) on the levels of total serum leucocytes, granulocytes including neutrophils, basophils, and eosinophils, as well as on monocytes and leucocytes were measured in pigs selected from a clean (minimal disease) herd. Thirty pigs were fed different rates of dietary CLA (0, 1.25, 2.5, 5.0, 7.5, and 10.0 g CLA-55/kg diet) for 8 weeks. Blood samples were collected at the end of the study for assessment of haematological and humoral responses to CLA supplementation. No difference in total white blood cells including the neutrophil, monocyte, and lymphocyte counts was observed among different dietary groups. A dose-dependent reduction (P = 0.02) in eosinophil concentrations suggests that CLA exerts anti-inflammatory activities. A 2-fold increase in the level of basophils was recorded in pigs fed lower levels of CLA (1.25 and 2.5 g CLA/kg diet) but the levels decreased gradually (P = 0.05) and were below the detection limit at the highest rate (10 g/kg) of CLA supplementation. The level of IgG was reduced by over 50% in CLA-fed pigs (P < 0.001), although the response was quadratic in nature (P < 0.001). T-cell population analysis showed that CD4+ cells tended (P = 0.06) to be reduced linearly with increasing inclusion of CLA in the diet. Our results suggest that dietary CLA modulates haematological and humoral responses in a dose-dependent manner.