Comparison of size-resolved PM elements measured using aluminum foil and Teflon impaction substrates: Implications for ultrafine particle source apportionment and future sampling networks in California.

Measurement networks for ultrafine particulate matter (PM0.1) have been limited by the high costs for equipment, supplies, and labor associated with the need to collect PM0.1 samples on multiple substrates for full chemical analysis. Here we explore whether a single cascade impactor loaded with aluminum foil substrates is sufficient for PM0.1 source apportionment calculations in order to reduce those costs. An extraction method previously designed to measure elements on Teflon substrates was modified to accommodate features of aluminum foil substrates. Regression analysis between co-located aluminum foil and Teflon substrates in the particle diameter range 0.1-1.8 µm showed good agreement (R > 0.7) for 18 elements. Regression in the diameter range 0.1-0.18 µm (quasi-ultrafine particulate matter) was used to characterize the uncertainty introduced by the aluminum foil extraction method for the elements Li, K, V, Br, Rb, Mo, Cd, Sn, Sb, and Ba. This uncertainty was used to generate 30 simulated aluminum foil PM0.1 datasets at each of three sites, followed by source apportionment analysis using Positive Matrix Factorization (PMF). At two of the three sites, the PM0.1 source contributions calculated using aluminum foil substrates alone were almost identical to the PMF results from combined aluminum foil and Teflon substrates. The PM0.1 source contributions calculated using aluminum foil substrates at the third site were closer to the results from a previous Chemical Mass Balance (CMB) study than to the PMF results from the combined aluminum foil and Teflon substrates, possibly because the CMB study also relied exclusively on samples collected using aluminum foil substrates. The success of the PM0.1 source apportionment approach using aluminum foil substrates in a single cascade impactor provides a viable method for reducing costs in PM0.1 sampling networks by 40-47%. Similar results may be achievable at locations outside of California.

Study of the temperature effect on the surface area of model organic molecules, the dispersive surface energy and the surface properties of solids by inverse gas chromatography.

This paper demonstrated the non-validity of Schultz et al. method by proving that the surface areas of n-alkanes and polar molecules strongly depend of the temperature. Consequently, the results of surface properties obtained by this method are inaccurate. Inverse gas chromatography (IGC) at infinite dilution and the dynamic contact angle (DCA) technique were used on the polytetrafluoroethylene (PTFE) fibers. DCA measurements led to the determination of the surface energy γs(T) of PTFE fibers as a function of the temperature T (Relation 6). The variations of the surface areas of n-alkanes and polar molecules versus the temperature were determined by studying the same PTFE fibers by IGC at infinite dilution. We proved that the product of the surface area a(T, Cn) (in Å2) of an alkane by the dispersive component of the surface energyγsd(T)of the solid is constant at any temperature: [Formula: see text] , where b(Cn) is a constant only depending on the carbon atom number n of n-alkane Cn. An analytical relation of the surface area of n-alkanes as a function of the temperature was obtained (equation 18). Our results highlighted the failure of Dorris-Gray method that was largely used to determine γsd of solids. This method considered the surface area a-CH2- of methylene group equal to 6 Å2 and constant for any used temperature. The obtained results proved the non-validity of Dorris-Gray method and gave the expression of a-CH2- as a function of the temperature T (Equation 20) proved the non-validity of Dorris-Gray method. The calculations of the thermal expansion coefficients of the surface area a and radius R represented by the respective derivatives da/dT and dR/dT, showed their important variations as a function of the temperature. The general expression of the surface area aX(T) of polar molecules was given as a function of the temperature (Expression 48). The large effect of the temperature on surface areas and radii of molecules was highlighted, except for toluene. The surface area of toluene was proved to remain constant whatever the temperature. Our results showed, in general, non-linear variations of the radius rX(T) of polar molecules adsorbed on PTFE fibers. However, except for chloroform, dichloromethane and diethyl ether where their thermal expansion coefficient depends on the temperature, the linearity of rX(T) was verified in the temperature interval [293 K, 353 K].

Analysis of polyhalogenated carbazoles in sediment using liquid chromatography-tandem mass spectrometry.

The purpose of this study was to develop a novel and sensitive method for the analysis of carbazole and polyhalogenated carbazoles (PHCs) in sediment using ultra performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS). Briefly, 5.0 g of freeze-dried sediment samples were extracted with dichloromethane using pressurized liquid extraction (PLE). The extract was purified with Florisil solid phase extraction cartridge, filtered through 0.22 µm polytetrafluoroethylene filter using a glass syringe, followed by LC-MS/MS analysis. Besides parameters for LC-MS/MS analysis, sample preparation procedures (including solvents for PLE, sorbents for cleanup, and filters for sample filtration) were optimized. The limits of detection and limits of quantification of target compounds were in the ranges of 3.0 × 10-3 to 0.22 ng g-1 dry weight (d.w.) and 1.0 × 10-2 to 0.75 ng g-1 d.w., respectively. The recoveries of target compounds in the spiked sediments at 2.0 ng g-1 d.w. and 10 ng g-1 d.w. were 64.8-91.8% and 70.9-124.7%, respectively, with relative standard deviations being less than 13.2%. Except that 36-BCZ had positive matrix effects of 63.3%, the sediment matrices generally displayed low or medium negative matrix effects on the other target compounds during LC-MS/MS analysis. The developed method was applied in the analysis of carbazoles and PHCs in sediment samples from Jiulong River, Fujian, China and all the target compounds were detected in the samples.

Actividad de la anfotericina B y la anidulafungina, solas y combinadas, frente a biopelículas de Candida tropicalis formadas sobre Teflon(R) y titanio / Activity of amphotericin B and anidulafungin, alone and combined, against Candida tropicalis biofilms developed on Teflon(R) and titanium

Antecedentes. Las estrategias terapéuticas actuales poseen una limitada eficacia para erradicar biopelículas de Candida formadas en la superficie de los dispositivos biomédicos. Pocos estudios han evaluado la eficacia de los antifúngicos sobre biopelículas de Candida tropicalis. Objetivos. Evaluar la actividad de la anfotericina B (AMB) y la anidulafungina (AND), solas y combinadas, sobre biopelículas de C. tropicalis desarrolladas en superficies de politetrafluoroetileno (teflón - PTFE) y titanio mediante ensayos de letalidad-tiempo. Métodos. Los ensayos se realizaron en un CDC Biofilm Reactor sobre biopelículas de 24h de maduración formadas en discos de PTFE y titanio. Las concentraciones ensayadas fueron 40mg/l para AMB y 8mg/l para AND, tanto para su uso por separado como combinadas. Tras 24, 48 y 72h de exposición a los antifúngicos se determinaron las ufc/cm2 mediante agitación vorticial y cultivo cuantificado previa sonicación. Resultados. AMB redujo las células viables adheridas a PTFE y titanio en más de un 99%, y AND lo hizo en un 89,3% en PTFE y 96,8% en titanio. La combinación AMB+AND fue menos activa que la AMB sola tanto en PTFE (descenso en ufc/cm2 de 3,09 Log10vs. 1,08 en la combinación) como en titanio (4,51 vs. 1,53 en la combinación), siendo la interacción indiferente en ambas superficies. Conclusiones. AMB es más activa que AND sobre biopelículas de C. tropicalis. La eficacia sobre las biopelículas es mayor en el titanio. La combinación AMB+AND es menos eficaz que AMB sola en ambas superficies (AU)

Background. Current therapeutic strategies have a limited efficacy against Candida biofilms that form on the surfaces of biomedical devices. Few studies have evaluated the activity of antifungal agents against Candida tropicalis biofilms. Objectives. To evaluate the activity of amphotericin B (AMB) and anidulafungin (AND), alone and in combination, against C. tropicalis biofilms developed on polytetrafluoroethylene (teflon -PTFE) and titanium surfaces using time-kill assays. Methods. Assays were performed using the CDC Biofilm Reactor equipped with PTFE and titanium disks with C. tropicalis biofilms after 24h of maturation. The concentrations assayed were 40mg/l for AMB and 8mg/l for AND, both alone and combined. After 24, 48 and 72h of exposure to the antifungals, the cfu/cm2 was determined by a vortexing-sonication procedure. Results. AMB reduced biofilm viable cells attached to PTFE and titanium by ≥99% and AND by 89.3% on PTFE and 96.8% on titanium. The AMB+AND combination was less active than AMB alone, both on PTFE (decrease of cfu/cm2 3.09 Log10vs. 1.08 when combined) and titanium (4.51 vs. 1.53 when combined), being the interaction irrelevant on both surfaces. Conclusions. AMB is more active than AND against C. tropicalis biofilms. Yeast killing rates are higher on titanium than on PTFE surfaces. The combination of AMB plus AND is less effective than AMB alone on both surfaces (AU)

Comprehensive mechanical characterization of PLA fabric combined with PCL to form a composite structure vascular graft.

Vascular grafts made by tissue engineering processes are prone to buckling and twisting, which can impede blood flow and lead to collapse of the vessel. These vascular conduits may suffer not only from insufficient tensile strength, but also from vulnerabilities related to compression, torsion, and pulsatile pressurization. Aiming to develop a tissue engineering-inspired blood conduit, composite vascular graft (cVG) prototypes were created by combining a flexible polylactic acid (PLA) knitted fabric with a soft polycaprolactone (PCL) matrix. The graft is to be populated in-situ with cellular migration and proliferation into the device. Comprehensive characterizations probed the relationship between structure and mechanical properties of the different cVG prototypes. The composite grafts exhibited major improvements in mechanical characteristics compared to single-material devices, with particular improvement in compression and torsional resistance. A commercial expanded polytetrafluoroethylene (ePTFE) vascular graft was used as a control against the proposed composite vascular grafts. CVG devices showed high tensile strength, high bursting strength, and improved suture retention. Compression, elastic recovery, and compliance were similar to those for the ePTFE graft.

On some physical and dynamical properties of microplastic particles in marine environment.

Simplified physical models and geometrical considerations reveal general physical and dynamical properties of microplastic particles (0.5-5mm) of different density, shape and size in marine environment. Windage of extremely light foamed particles, surface area and fouling rate of slightly positively buoyant microplastic spheres, films and fibres and settling velocities of negatively buoyant particles are analysed. For the Baltic Sea dimensions and under the considered idealised external conditions, (i) only one day is required for a foamed polystyrene particle to cross the sea (ca. 250km); (ii) polyethylene fibres should spend about 6-8months in the euphotic zone before sinking due to bio-fouling, whilst spherical particles can be retained on the surface up to 10-15years; (iii) for heavy microplastic particles, the time of settling through the water column in the central Gotland basin (ca. 250m) is less than 18h. Proper physical setting of the problem of microplastics transport and developing of physically-based parameterisations are seen as applications.

Improved recovery of Listeria monocytogenes from stainless steel and polytetrafluoroethylene surfaces using air/water ablation.

AIMS: To develop a gentle ablation technique to recover Listeria monocytogenes biofilms from stainless steel (SS) and polytetrafluoroethylene (PTFE) surfaces by using compressed air and water injection. METHODS AND RESULTS: Biofilms were grown for 4, 24 and 48 h or 7 days and a compressed air and water flow at 2, 3 and 4 bars was applied for cell removal. Collected cells were quantified for total/dead by staining with SYTO 9/PI double staining and cultivable populations were determined by plating onto brain heart infusion (BHI) agar, while coupon surfaces also were stained with DAPI to quantify in situ the remaining cells. The recovery efficiency was compared to that of conventional swabbing. Results showed that the air/water ablation is able to collect up to 98·6% of cells from SS surfaces while swabbing only recovered 11·2% of biofilm. Moreover, air/water ablation recovered 99·9% of cells from PTFE surfaces. CONCLUSIONS: The high recovery rate achieved by this technique, along with the fact that cells were able to retain membrane integrity and cultivability, indicate that this device is suitable for the gentle recovery of viable L. monocytogenes biofilm cells. SIGNIFICANCE AND IMPACT OF THE STUDY: This work presents a highly efficient technique to remove, collect and quantify L. monocytogenes from surfaces commonly used in the food industry, which can thus serve as an important aid in verifying cleaning and sanitation as well as in reducing the likelihood of cross-contamination events.

Emission of perfluoroalkyl carboxylic acids (PFCA) from heated surfaces made of polytetrafluoroethylene (PTFE) applied in food contact materials and consumer products.

Polytetrafluoroethylene (PTFE) has been widely discussed as a source of perfluorooctanoic acid (PFOA), which has been used in the production of fluoropolymers. PTFE may also contain unintended perfluoroalkyl carboxylic acids (PFCAs) caused by thermolysis of PTFE, which has been observed at temperatures above 300°C. Common PTFE coated food contact materials and consumer goods are operated at temperatures above 200°C. However, knowledge on possible emissions of PFCAs is limited. Therefore, it was the aim of this study to investigate and evaluate the emission of PFCAs from PTFE coated products with both, normal use and overheating scenarios. Four pans, claimed to be PFOA free, and nine consumer products were investigated. At normal use conditions (<230°C), emissions from PTFE surfaces were trapped for 1h. Overheating scenarios (>260°C) recorded emissions during a 30min heating of empty pans on a stove. Emissions were analyzed by LC-ESI-MS. Results indicate the emission of PFCAs, whereas no perfluorinated sulfonic acids were traced. At normal use conditions total emissions of PFCAs accounted for 4.75ng per hour. Overheated pans, however, released far higher amounts with up to 12190ng PFCAs per hour at 370°C. Dominating contributors where PFBA and PFOA at normal use and PFBA and PFPeA during overheating. Temperature seems to be the main factor controlling the emission of PFCAs. A worst case estimation of human exposure revealed that emissions of PFCAs from heated PTFE surfaces would be far below the TDI of 1500ng PFOA per kg body weight.

Note: deep ultraviolet Raman spectrograph with the laser excitation line down to 177.3 nm and its application.

Deep UV Raman spectrograph with the laser excitation line down to 177.3 nm was developed in this laboratory. An ellipsoidal mirror and a dispersed-subtractive triple monochromator were used to collect and disperse Raman light, respectively. The triple monochromator was arranged in a triangular configuration with only six mirrors used. 177.3 nm laser excited Raman spectrum with cut-off wavenumber down to 200 cm(-1) and spectral resolution of 8.0 cm(-1) can be obtained under the condition of high purity N2 purging. With the C-C σ bond in Teflon selectively excited by the 177.3 nm laser, resonance Raman spectrum of Teflon with good quality was recorded on the home-built instrument and the σ-σ(*) transition of C-C bond was studied. The result demonstrates that deep UV Raman spectrograph is powerful for studying the systems with electronic transition located in the deep UV region.

Analysis of thickness of a hydrophobic fluoropolymer film based on electrowetting.

The electrowetting of water drops on a dielectric fluoropolymer film was studied experimentally. The dependence of the contact angles of the water drops on the applied voltage has been well explained in the low-voltage limit by using the classical Young-Lippmann theory. With this theory, the thicknesses of films coated on glass substrates by using a spin-coater were obtained indirectly by fitting the contact angle data and were confirmed by using X-ray reflectometry. The two sets of results showed a good agreement. In addition, we confirmed that the contact angle saturation at high voltage were consistent with Peykov's model.

Properties and water sorption characteristics of spaghetti prepared using various dies.

Spaghetti was prepared using dies made of different materials. The surface was observed using digital and optical microscopes, and was rougher for the spaghettis prepared using the Teflon, polypropylene, polycarbonate, aluminum, and bronze dies in this order. The extrusion velocity when passing through the die was faster, the bulk density was higher, and the rupture strength was greater for the spaghetti having the smoother surface. The die material did not affect the gelatinization temperature. The water sorption curves in boiling water containing 0.5% (w/v) sodium chloride were also observed. The curves were expressed by an equation of the hyperbolic type except for the early stage of sorption in order to estimate the equilibrium amount of water sorbed based on the bone-dry sample. The momentarily-sorbed amount of water, which is a hypothetical quantity to characterize the initial water intake, was estimated by fitting the experimental points within 60 s. The amount was higher for the spaghetti having the rougher surface.

Surface analysis using a new plasma assisted desorption/ionisation source for mass spectrometry in ambient air.

The authors report on a modified micro-plasma assisted desorption/ionisation (PADI) device which creates plasma through the breakdown of ambient air rather than utilising an independent noble gas flow. This new micro-PADI device is used as an ion source for ambient mass spectrometry to analyse species released from the surfaces of polytetrafluoroethylene, and generic ibuprofen and paracetamol tablets through remote activation of the surface by the plasma. The mass spectra from these surfaces compare favourably to those produced by a PADI device constructed using an earlier design and confirm that the new ion source is an effective device which can be used to achieve ambient mass spectrometry with improved spatial resolution.

Retrospective exposure assessment of perfluorooctanoic acid serum concentrations at a fluoropolymer manufacturing plant.

Perfluorooctanoic acid (PFOA) is a suspect human carcinogen, causes neonatal loss, liver enlargement, and a variety of tumors in rodents, and has been associated with increased cholesterol levels in humans. Mortality analyses of worker cohorts have not been conclusive or consistent. As part of a series of epidemiologic studies of workers in a West Virginia plant that manufactures fluoropolymers, estimates of serum PFOA for the worker cohort were developed for the period of 1950-2004. An existing database of 2125 worker biomarker measurements of serum PFOA was used to model retrospective exposures. Historical PFOA serum levels for eight job category/job group combinations were modeled using linear mixed models to account for repeated measures, along with exposure determinants such as cumulative years worked in potentially exposed jobs, the amount of C8 used or emitted by the plant over time, as well as a four-knot restricted cubic spline function to reflect the influence of process changes over calendar time on exposure. The modeled biomarker levels matched well with measured levels, including those collected independently as part of a community study of PFOA levels (Spearman correlations of 0.8 for internal data comparisons and 0.6 for external data comparisons). These annualized PFOA serum estimates will be used in a series of morbidity and mortality studies of this worker cohort.

Potable water recovery from As, U, and F contaminated ground waters by direct contact membrane distillation process.

In this study, the feasibility of the direct contact membrane distillation (DCMD) process to recover arsenic, uranium and fluoride contaminated saline ground waters was investigated. Two types of membranes (polypropylene, PP; and polytetrafluoroethylene, PTFE) were tested to compare the permeate production rates and contaminant removal efficiencies. Several experiments were conducted to study the effect of salts, arsenic, fluoride and uranium concentrations (synthetic brackish water with salts: 1000-10,000 ppm; arsenic and uranium: 10-400 ppb; fluoride: 1-30 ppm) on the desalination efficiency. The effect of process variables such as feed flow rate, feed temperature and pore size was studied. The experimental results proved that the DCMD process is able to achieve over 99% rejection of the salts, arsenic, fluoride and uranium contaminants and produced a high quality permeate suitable for many beneficial uses. The ability to utilize the low grade heat sources makes the DCMD process a viable option to recover potable water from a variety of impaired ground waters.

An optimized method for the determination of perfluorooctanoic acid, perfluorooctane sulfonate and other perfluorochemicals in different matrices using liquid chromatography/ion-trap mass spectrometry.

Perfluorochemicals (PFC's) are widely spread in the environment and have been detected in blood of wildlife and humans world-wide. Recently, various toxic effects of PFC's in laboratory rats have been demonstrated, resulting in increased government concerns regarding the presence of PFC's in the environment and the implications they have on human health. In the last decade, various analytical methods have been developed for the analysis of PFC's in different matrices whereby the majority of methods have utilised liquid chromatography coupled with mass spectrometry (LC-MS). Here we describe an optimized method for the quantitation of PFC's, including perfluorooctanoic acid (PFOA) and perfluorooctane sulfonate (PFOS), in food packaging, polytetrafluoroethylene (PTFE) sealant tape and drinking water. The method involved PFC's extraction via off-line SPE followed by separation using reversed-phase liquid chromatography on a Phenyl-Hexyl column coupled with ion-trap (IT) mass spectrometric detection. The optimized approach minimized ion-suppression effects commonly seen with conventional elution buffers, improving detection limits down to 25 pg/mL and allowed effective quantitation down to 50 pg/mL for PFOA and PFOS. The optimized LC-MS method detected PFOA and other PFC's in microwave popcorn packaging and PFOA in PTFE sealant tape in the low µg/kg. In all samples, PFOS was not detected.

Detection of low-level PTFE contamination: An application of solid-state NMR to structure elucidation in the pharmaceutical industry.

We report a novel use of solid-state ¹9F nuclear magnetic resonance to detect and quantify polytetrafluoroethylene contamination from laboratory equipment, which due to low quantity (up to 1% w/w) and insolubility remained undetected by standard analytical techniques. Solid-state ¹9F NMR is shown to be highly sensitive to such fluoropolymers (detection limit 0.02% w/w), and is demonstrated as a useful analytical tool for structure elucidation of unknown solid materials.

A method of identification of abnormal glow curves in individual monitoring using CaSO4:Dy teflon TLD and hot gas reader.

In the present study, a method of identifying abnormal glow curves to electronically screen the glow curves of TL readout is presented. The method is based on the fact that the shape of an abnormal glow curve differs from the shape of a normal one. A few criteria for defining the normal shape of glow curves are arrived at by analysing the glow curves of dosemeters exposed to various doses in laboratory conditions and read at different elapsed time post irradiation. About 300 glow curves of dosemeters used for monthly monitoring were analysed as per these criteria and the effectiveness of the method is observed for total counts as low as 150 µSv equivalent.

Raman sensitivity enhancement for aqueous absorbing sample using Teflon-AF 2400 liquid core optical fibre cell.

The compatibility Teflon-AF 2400 liquid core optical fibre with resonance Raman spectroscopy (RRS-LCOF) was used to detect aqueous biomolecules. The maximum sensitivity enhancement factor for concentrations greater than the detection limit in a conventional cell was 10, and detection limit reduction of about 1000-fold have been achieved for the measurement of aqueous absorbing sample using Teflon-AF 2400 fibre Raman cell compared to the conventional cell. We were able to collect spectra of 2.5 x 10(-9) and 2.5 x 10(-10) M aqueous beta-carotene using 16.2 mW of laser power and 10s integration time. This volume of a 2.5 x 10(-10) M aqueous solution corresponds to only 1.5 fmol or 830 fg of beta-carotene. The results of this preliminary study indicate that RRS-LCOF has potential in bioanalytical and biomedical applications.

Prospective histologic evaluation of intra-abdominal prosthetics four months after implantation in a rabbit model.

BACKGROUND: Placement of an intraperitoneal prosthetic is required for laparoscopic ventral hernia repair. The biocompatibility of these prosthetics determines the host's inflammatory response, scar plate formation, tissue ingrowth, and subsequent mesh performance, including prosthetic compliance and prevention of hernia recurrence. We evaluated the host response to intraperitoneal placement of several prosthetics currently used in clinical practice. METHODS: A 4-cm x 4-cm piece of mesh was implanted on intact peritoneum in New Zealand white rabbits. The mesh types included expanded polytetrafluoroethylene (ePTFE) (DualMesh), ePTFE and polypropylene (Composix, heavyweight polypropylene), polypropylene and oxidized regenerated cellulose (Proceed, midweight polypropylene), and polypropylene (Marlex, heavyweight polypropylene). At four months, standard hematoxylin and eosin and Milligan's trichrome stains of the mesh-tissue interaction were analyzed by three observers blinded to the mesh types. Each specimen was evaluated for scar plate formation, inflammatory response, and tissue ingrowth. Each of these three categories was graded on a standard scale of 1-4 (1 = normal tissue and 4 = severe inflammatory response). The scores were analyzed using Wilcoxon rank sum test with p < 0.05 as significant. RESULTS: Ten samples of each mesh type were evaluated. There was no difference in tissue incorporation between the groups. The mean scar plate formation was greater in the heavyweight polypropylene meshes than for DualMesh (p = 0.04). With Proceed, the reduction in scar plate formation compared with that for Composix and Marlex approached statistical significance (p = 0.07). The mean number of inflammatory cells was greater around the ePTFE when compared with the midweight polypropylene (p = 0.02) but equal to the other meshes. CONCLUSIONS: The four prosthetic materials evaluated in this study demonstrate comparable host biocompatibility as evidenced by the tissue ingrowth. Scar plate formation around DualMesh was significantly less than that around Composix and Marlex. Interestingly, more inflammatory cells were noted surrounding the DualMesh which was equal to that of the heavyweight meshes. Proceed, a midweight polypropylene mesh, has the potential for improved patient tolerance compared to heavyweight polypropylene meshes based on its favorable histologic findings.

Characterisation of the internal and external surfaces of four types of Foley catheter using SEM and profilometry.

Unfortunately the use of Foley catheters for long-term catheterisation is frequently associated with complications such as infection and encrustation. This study investigated whether a link could exist between the surface properties of the catheters and the problems that can develop. The internal and external surfaces of four different types of urinary catheter were examined. Three latex devices coated with either PTFE or hydrogel or surface treated with silicone were investigated. In addition, an all-silicone device was examined. The surfaces of the all-silicone catheters were relatively smooth and featureless. In contrast, the external surfaces of each of the latex devices were 'paved' in nature. The internal surfaces of latex based devices produced by different manufacturers showed distinct differences with evidence of inorganic inclusions on the internal surfaces of two of the catheter types. These findings may be significant in the context of catheter infection and encrustation.