Visualization of zinc pyrithione particles deposited on the scalp from a shampoo by tape-strip sampling and scanning electron microscopy/energy dispersive X-ray spectroscopy measurement.

OBJECTIVE: Zinc pyrithione (ZnPT) is widely used as an anti-fungal active in commercial anti-dandruff (AD) shampoos. The AD efficacy of ZnPT is highly dependent on the deposition of ZnPT particles onto the scalp during the process of shampoo application and rinse-off. Since ZnPT materials with different particle sizes and morphologies have different deposition behaviours, the measurement of the actual ZnPT deposition is critical to understand the AD performance delivered by different ZnPT shampoos. The aim of this study is to develop a robust and reliable method for visualizing the particle size and morphology of ZnPT deposited on the scalp from AD shampoos. METHODS: Hair was washed with a commercially available AD shampoo containing ZnPT and zinc carbonate (ZnCO3 ). Tape strips were applied to collect the deposited particles from the scalp after AD shampoo application and rinse-off. The scalp tape strip samples were subjected to scanning electron microscopy/energy dispersive X-ray spectroscopy (SEM/EDX) measurement. The morphology of the ZnPT particles was visualized by SEM imaging and identification of ZnPT particles was confirmed by EDX analysis. RESULTS: For the commercial shampoo studied it was observed that two zinc-containing particulates with different morphologies and composition remained on the scalp after shampoo application and rinse-off. As indicated by the EDX spectra, the ZnPT particles deposited onto the scalp surface had polygonal crystal structures. ZnCO3 was also deposited onto the scalp surface. This material was mainly present as aggregated particulates. CONCLUSION: An ex vivo method that combines tape strip sampling and SEM/EDX has been developed for measuring and visualizing the particle size, morphology and composition of ZnPT deposited on the scalp from AD shampoos. This ex vivo measurement method provides higher imaging resolution and more chemical specificity than reflectance confocal microscopy (RCM). To the best of our knowledge, this is the first time that ZnPT particles were distinguishable from other zinc particles on the scalp. Moreover, the new method allows the microstructures of both ZnPT and other zinc particles on the scalp to be imaged.

Profiling of volatile organic compounds produced by clinical Aspergillus isolates using gas chromatography-mass spectrometry.

Volatile organic compounds (VOCs) in exhaled breath may identify the presence of invasive pulmonary aspergillosis. We aimed to detect VOC profiles emitted by in vitro cultured, clinical Aspergillus isolates using gas chromatography-mass spectrometry (GC-MS). Three clinical Aspergillus isolates and a reference strain were cultured while conidiation was prevented. Headspace samples were analyzed using a standardized method. Breath samples of patients from which the cultures were obtained were checked for the presence of the VOCs found in vitro. Each Aspergillus isolate produced a distinct VOC profile. These profiles could not be confirmed in exhaled breath in vivo.

Exhaled air molecular profiling in relation to inflammatory subtype and activity in COPD.

Eosinophilic inflammation in chronic obstructive pulmonary disease (COPD) is predictive for responses to inhaled steroids. We hypothesised that the inflammatory subtype in mild and moderate COPD can be assessed by exhaled breath metabolomics. Exhaled compounds were analysed using gas chromatography and mass spectrometry (GC-MS) and electronic nose (eNose) in 28 COPD patients (12/16 Global Initiative for Chronic Obstructive Lung Disease (GOLD) stage I/II, respectively). Differential cell counts, eosinophil cationic protein (ECP) and myeloperoxidase (MPO) were measured in induced sputum. Relationships between exhaled compounds, eNose breathprints and sputum inflammatory markers were analysed and receiver operating characteristic (ROC) curves were constructed. Exhaled compounds were highly associated with sputum cell counts (eight compounds with eosinophils, 17 with neutrophils; p < 0.01). Only one compound (alkylated benzene) overlapped between eosinophilic and neutrophilic profiles. GC-MS and eNose breathprints were associated with markers of inflammatory activity in GOLD stage I (ECP: 19 compounds, p < 0.01; eNose breathprint r = 0.84, p = 0.002) (MPO: four compounds, p < 0.01; eNose r = 0.72, p = 0.008). ROC analysis for eNose showed high sensitivity and specificity for inflammatory activity in mild COPD (ECP: area under the curve (AUC) 1.00; MPO: AUC 0.96) but not for moderate COPD. Exhaled molecular profiles are closely associated with the type of inflammatory cell and their activation status in mild and moderate COPD. This suggests that breath analysis may be used for assessment and monitoring of airway inflammation in COPD.

Phytosterol and phytostanol esters are effectively hydrolysed in the gut and do not affect fat digestion in ileostomy subjects.

BACKGROUND: Hydrolysis of phytosterol ester (PSTE) and phytostanol ester (PSTA) during fat digestion is not well characterised under controlled dietary conditions. AIMS: The main aims of this study were therefore to quantify the PSTE and PSTA hydrolysis after gut passage and to assess whether or not PSTE and PSTA induce fat malabsorption by measuring the fatty acid excretion following PSTE/PSTA consumption. METHODS: Ileostomy subjects (n = 7) were investigated in a randomised crossover study with one control and two intervention periods, when either 2.5 g of PSTE or PSTA corresponding to 1.5 g free sterol or stanol equivalents were added to a controlled diet. Ileostomy bags were collected and immediately frozen for analysis of nutrients, fatty acids and sterols. RESULTS: The study showed that 88.4 +/- 5.9% PSTE and 85.7 +/- 6.5% PSTA were hydrolysed following small bowel passage in the ileostomy subjects. The total excretion of fatty acids was similar in all three periods. CONCLUSIONS: A majority of the 2.5 g PSTE and PSTA was hydrolysed during small bowel passage,which did not affect fat absorption as indicated by similar excretions of fatty acids in all periods. Consumption of increasing amounts of esterified phytosterols and phytostanols from enriched food formats should thereby have no adverse effects in this regard.

Comprehensive multi-dimensional chromatographic studies on the separation of saturated hydrocarbon ring structures in petrochemical samples.

Characterization of complex petrochemical samples has been a classical subject of comprehensive two-dimensional (2D) gas chromatography (GC x GC). Macroscopic properties of these samples can be described accurately by separation of compounds in classes of identical molecular functionality. Ring structures in the carbon backbone of these compounds, which can be divided in saturated and unsaturated, are amongst the foremost functionalities affecting samples properties. Unfortunately, GC x GC tuned for separation of both saturated and unsaturated ring structures is likely to result in convoluted chromatograms when a distribution of both molecular properties is present in the sample. An independent liquid chromatographic (LC) separation preceding GC x GC could be used to resolve the mixture based on unsaturated rings, allowing saturated rings to be resolved separately in the GC x GC separation. This three-dimensional separation (abbreviated LC-GC x GC) was performed after rigorous evaluation of LC as part of a multidimensional separation using LC x GC. Group-type separation was achieved using this separation for components with either saturated or unsaturated rings. Results of this separation were used to compare information obtained by GC x GC with LC-GC x GC.

Automated determination of fatty acid methyl ester and cis/trans methyl ester composition of fats and oils.

The determination of the fatty acid composition (as methyl esters, FAMEs) of fats and oils and their cis/trans (CTME) distribution requires a simple, but manual and time-consuming sample preparation. The so-called BF3 method is often the preferred procedure. Because FAME/CTME analyses are encountered very frequently in the food industry, an automated, robot-based alternative is proposed which uses the sodium methylate procedure. After sample weighing and the (manual) addition of heptane (2 min), a XYZ robotic autosampler is used for all remaining work, which includes reagent addition, agitation, sample settling and the final injection into the gas chromatograph (10 min). The performance of the sodium methylate and BF3 methods are compared by analysing some 30 oil and fat samples. The novel procedure is much faster (less than 15 min versus ca. 1 h) and manual sample handling is drastically decreased. The experimental results obtained with the two methods frequently are the same, while small differences can be explained by (known) differences of the two methods in the conversion of minor oil/fat constituents, such as free fatty acids, wax esters and sterol esters. In case of FAME analyses, a hot injection is to be preferred over a cold injection. The RSDs of the peak areas were 1.5% for the major fatty acids to 11% for peaks that were just above the noise level. The detection limit were approximately 0.03%.

Evaluation of time-of-flight mass spectrometric detection for fast gas chromatography.

Separations below 1 s of a mixture of organic compounds ranging from C5 to C8 have been performed to investigate the performance of a time-of-flight mass spectrometer in fast gas chromatography. The gaseous samples were focussed on a cold trap, and then injected after thermal desorption to obtain the required narrow input band-widths. Also, to obtain a very fast separation, a short narrow bore column was used, operated at above-optimum inlet pressures. With this system, it was possible to identify ten compounds within 500 ms, showing peak-widths (2.354sigma) as narrow as 12 ms. The spectral acquisition rate used for these analyses was 500 Hz. The quality of the recorded spectra and the comparison with library spectra was very high. Deconvolution algorithms offer the possibility of identifying overlapping peaks. It is shown that the spectral scan speed of the time-of-flight mass spectrometer is high enough for very fast separations.

On-line coupling of equilibrium-sorptive enrichment to gas chromatography to determine low-molecular-mass pollutants in environmental water samples.

On-line combination of equilibrium sorptive enrichment and gas chromatography is used for the analysis of a group of pollutants varying widely in polarity and volatility in aqueous samples at trace levels. For the ESE process open-tubular traps were used. The newly developed hyphenated method shows a high sensitivity for all the compounds under study. The detection limits were typically between 0.1 and 1 microg/l. The sample volumes required for the compounds to reach equilibrium with the stationary phase are in the range of 20 ml for the aromatic hydrocarbons included in the study (benzene, toluene and p-xylene), to 200 ml for epichlorohydrin and dichlorohydrin. Within- and between-day precision of the absolute peak areas varied between 3 and 16%. The performance of the new method was tested by the analysis of different environmental water samples.

High-speed gas chromatography: an overview of various concepts.

An overview is given of existing methods to minimise the analysis time in gas chromatography (GC) being the subject of many publications in the scientific literature. Packed and (multi-) capillary columns are compared with respect to their deployment in fast GC. It is assumed that the contribution of the stationary phase to peak broadening can be neglected (low liquid phase loading and thin film columns, respectively). The treatment is based on the minimisation of the analysis time required on both column types for the resolution of a critical pair of solutes (resolution normalised conditions). Theoretical relationships are given, describing analysis time and the related pressure drop. The equations are expressed in reduced parameters, making a comparison of column types considerably simpler than with the conventional equations. Reduction of the characteristic diameter, being the inside column diameter for open tubular columns and the particle size for packed columns, is the best approach to increase the separation speed in gas chromatography. Extremely fast analysis is only possible when the required number of plates to separate a critical pair of solutes is relatively low. Reducing the analysis time by reduction of the characteristic diameter is accompanied by a proportionally higher required inlet pressure. Due to the high resistance of flow of packed columns this seriously limits the use of packed columns for fast GC. For fast GC hydrogen has to be used as carrier gas and in some situations vacuum-outlet operation of capillary columns allows a further minimisation of the analysis time. For fast GC the columns should be operated near the conditions for minimum plate height. Linear temperature programmed fast GC requires high column temperature programming rates. Reduction of the characteristic diameter affects the sample capacity of the "fast columns". This effect is very pronounced for narrow-bore columns and in principle non-existing in packed columns. Multi-capillary columns (a parallel configuration of some 900 narrow-bore capillaries) take an intermediate position.

Effects of high-shear granulation on granulate homogeneity.

This study considers the effects of particle size of the powder constituents, and of impeller speed on the homogeneity of drug distribution on granulations produced in high-speed mixers. When a micronized low-dose steroid hormone was granulated together with unmicronized lactose in a Vactron 75 high-shear granulator at 250 rpm, strong inhomogeneities of the drug distribution arose. The coarse particle size fractions of the granules were found to be superpotent up to 150% of the mean drug content, whereas the fine size fraction showed a corresponding subpotency of 50%. Both particle size and impeller speed attributed to this phenomenon. At an impeller speed of 75 rpm, a significantly better drug distribution was obtained. Results show that the inhomogeneities found are mainly a consequence of the balance between the impact pressure as exerted by the impeller on the one hand and the shear resistance of the nuclei on the other hand. At a speed of 250 rpm, the tensile strength of 3 x 10(3) N/m2 of the initially formed nuclei is too weak to resist an impact pressure of 30 x 10(3) N/m2. For that reason, particle rearrangement takes place, which results in inhomogeneity. Because an impeller speed of 75 rpm is equal to an impact pressure of 2.6 x 10(3) N/m2, significantly less demixing occurs. Similar results can be obtained when the particle size of all constituents is reduced, which increases the tensile strength of the nuclei.

Determination of phenylurea herbicides in water samples using online sorptive preconcentration and high-performance liquid chromatography with UV or electrospray mass spectrometric detection.

A recently developed method for the extraction of organic micropollutants from aqueous samples based on sorptive enrichment in columns packed with 100% polydimethylsiloxane (PDMS) particles was coupled on-line with HPLC analysis. The sorptive enrichment procedure originally developed for relatively nonpolar analytes was used to preconcentrate polar phenylurea herbicides from aqueous samples. PDMS extraction columns of 5, 10 and 25 cm were used to extract the herbicides from distilled, tap and river water samples. A model that allows prediction of retention and breakthrough volumes is presented. Despite the essentially apolar nature of the PDMS material, it is possible to concentrate sample volumes up to 10 ml on PDMS cartridges without losses of the most polar analyte under investigation, fenuron. For less polar analytes significantly larger sample volumes can be applied. Since standard UV detection does not provide adequate selectivity for river water samples, an electrospray (ES)-MS instrument was used to determine phenylurea herbicides in a water sample from the river Dommel. Methoxuron was present at a level of 80 ng/l. The detection limit of the current set-up, using 10 ml water samples and ES-MS detection is 10 ng/l in river water samples. Strategies for further improvement of the detection limits are identified.

Novel preconcentration technique for on-line coupling to high-speed narrow-bore capillary gas chromatography: sample enrichment by equilibrium (ab)sorption. I. Principles and theoretical aspects.

In recent years, there has been substantial progress in the field of high-speed narrow-bore capillary gas chromatography (GC) in general, and in the development of (trans)portable gas chromatographs for fast and accurate analysis in field applications in particular. Due to the limited (concentration) sensitivity of instrumentation for high-speed (portable) GC, environmental applications of this technique frequently require a preconcentration step. The equilibrium (ab)sorption technique described in this article was found to be very promising for on-line coupling to high-speed narrow-bore capillary GC and field portable GC instruments. Enrichment factors up to at least 100 can be obtained rapidly without the use of complicated instrumentation. The new preconcentration technique is shown to have clear advantages over enrichment based on conventional adsorption, i.e. thermal desorption techniques. It can be carried out at ambient trapping temperatures, gives uniform desorption profiles, reduces water effects, uses inert adsorption materials and does not require a (cryogenic) refocusing step. Moreover, the new preconcentration method allows the enrichment factors to be predicted from tabulated chromatographic data, thereby facilitating calibration.

Novel preconcentration technique for on-line coupling to high-speed narrow-bore capillary gas chromatography: sample enrichment by equilibrium (ab)sorption. II. Coupling to a portable micro gas chromatograph.

The technique of equilibrium (ab)sorption has been proven to be a powerful method for preconcentration of gaseous samples for high-speed narrow-bore capillary gas chromatography (GC) in general and field-portable GC instruments, often referred as micro GCs, in particular. Using a simple experimental set-up equipped with an open-tubular enrichment column it is possible to produce a homogeneously enriched sample plug, allowing reproducible injections of an enriched sample into the micro GC. Using a non-polar trapping column enrichment factors found for n-alkanes in the range of C7 to C10 ranged from 15 to 150 and agree well with calculated values. Using a highly retentive Thermocap column, the enrichment factor observed for heptane was above 500. As the use of this new preconcentration method requires only minimum modification of the micro GC, the chromatographic performance of the instrument was not compromised by direct coupling to the preconcentration device. Examples of on-line enrichment with portable micro GC analysis of VOCs from air are shown. These examples clearly demonstrate the potentials of the new method in field analysis.

Imino-proton resonances of yeast tRNAPhe studied by two-dimensional nuclear Overhauser enhancement spectroscopy.

Application of two-dimensional nuclear Overhauser enhancement (NOE) spectroscopy to yeast tRNAPhe in H2O solution demonstrates that all imino-proton resonances, related to the secondary structure, and nearly all imino proton resonances, originating from the tertiary structure, can be assigned efficiently by this method. The results corroborate the assignments of the imino-proton resonances of this tRNA as established previously by one-dimensional NOE experiments (only the assignment of base pairs G1 X C72 and C2 X G71 should be reversed). The advantages of two-dimensional NOE spectroscopy over one-dimensional NOE spectroscopy for the assignments of imino-proton resonances and the structure elucidation of tRNA are illustrated and discussed. Furthermore, the use of non-exchangeable proton resonances as probes of the molecular structure is explored.

Structure, kinetics and thermodynamics of DNA hairpin fragments in solution.

The hairpin-to-coil equilibrium of the hexadecadeoxynucleotide d(ATCCTATTTTTAGGAT) was extensively studied by means of NMR, T-jump and UV. The thermodynamic and kinetic parameters for this equilibrium were determined, yielding a consistent picture of the dynamical behavior of this hairpin structure, which is shown to be a clear example of a situation in which the linebroadening of the imino proton resonances is not determined by the lifetime of the double helix. A comparative study of the homologous hairpins in which the size of the loop was elongated from 4 to 7 thymidine residues shows a monotonous decrease in Tm for the hairpin-to-coil transitions. This finding is in contrast with the view that the stability of hairpins reaches a maximum with a loop size of 6-7 residues. The NMR results indicate that the accessibility of the thymine bases in the loop towards solvent molecules or complementary nucleotides greatly depends on the size of the loop.