Cleaning Step Research Articles

Effectiveness of current disinfection procedures against biofilm on contaminated GI endoscopes

Attention to patient safety has increased recently due to outbreaks of nosocomial infections associated with GI endoscopy. The aim of this study was to evaluate current cleaning and disinfection procedures of endoscope channels with high bioburden and biofilm analysis, including the use of resistant mycobacteria associated with postsurgical infections in Brazil. Twenty-seven original endoscope channels were contaminated with organic soil containing 10(8) colony-forming units/mL of Pseudomonas aeruginosa, Staphylococcus aureus, or Mycobacterium abscessus subsp bolletii. Biofilms with the same microorganisms were developed on the inner surface of channels with the initial inoculum of 10(5) colony-forming units/mL. Channels were reprocessed following current protocol, and samples from cleaning and disinfection steps were analyzed by bioluminescence for adenosine triphosphate, cultures for viable microorganisms, and confocal microscopy. After contamination, adenosine triphosphate levels increased dramatically, and high bacterial growth was observed in all cultures. After cleaning, adenosine triphosphate levels decreased to values comparable to precontamination levels, and bacterial growth was demonstrated in 5 of 27 catheters, 2 with P aeruginosa and 3 with M abscessus. With regard to induced biofilm, a remarkable reduction occurred after cleaning, but significant microbial growth inhibition occurred only after disinfection. Nevertheless, viable microorganisms within the biofilm were still detected by confocal microscopy, more so with glutaraldehyde than with peracetic acid or O-phataladehyde. After the complete disinfection procedure, viable microorganisms could still be detected within the biofilm on endoscope channels. Prevention of biofilm development within endoscope channels should be a priority in disinfection procedures, particularly for ERCP and EUS.

Post CMP Cleaning: a Comparison of Contact and Non-Contact Physical Cleaning Methods

Chemical mechanical planarization (CMP) process steps are increasing in frequency and criticality. The introduction of new, sensitive dielectric materials as well as sensitivity to residual slurry and particle contamination make the post CMP clean an integral part of a good yielding CMP step. Brush Scrubbing is the traditional method of post CMP cleaning. With this contact cleaning method particles are removed by direct contact of a rotating brush with the wafer surface. These particles are then swept away by the cleaning solution. This method of cleaning has some well known challenges, among them cross contamination from wafer to wafer, brush marking and scratching as well as process feedback and control. An alternative physical cleaning method utilizes the cavitation created by the presence of Megasonic energy in the process fluid to provide a non-contact method of slurry residual and particulate removal from the planarized surface. The Megasonic apparatus used in these experiments has been successfully applied to other single wafer cleaning processes and is implemented in many large volume production applications. Most mass production post CMP cleaning processes consist of a series of cleaning and chemistry steps as well as a mix of physical cleaning approaches. The challenge in quantifying effect and comparing cleaning efficiency between contact and non-contact physical cleaning has been in the isolation of cleaning results attributed to a change in method. In this work we were able to provide conditions for a direct comparison of cleaning methods in a special post CMP scrubber. This tool is configured for brush or Megasonic processes in the same chamber with the identical wafer flow from the polisher. The CMP was done on thermal SiO2 using two varieties of conventional slurry and a common pad type. Fifty wafers were split processed, half with 150835 and half with D3586. A large delta in particle removal efficiency was observed based on slurry type alone. The brush parameters were based on a long term process of record. (Table 1) Several megasonic parameters were varied to better understand the process window. Analysis of cleaning results was performed using an SP2 with a threshold of 90nm. (Figure 1) Table 1, Experimental process recipe details Brush Recipe Step Time (sec) Chemical Wafer RPM Brush RPM 1 40 NH4OH 2% 20 80 2 40 DIW 20 80 3 20 DIW 60 No Brush 4 Dry 2000 Meg Recipe 1 Step Time (sec) Chemical Wafer RPM W/cm2 1 52 NH4OH 2% 60 2.5 2 48 DIW 60 2.5 3 Dry 2000 0 Meg Recipe 2 Step Time (sec) Chemical Wafer RPM W/cm2 1 52 NH4OH 2% 60 1.85 2 48 DIW 60 1.85 3 Dry 2000 0 Meg Recipe 3 Step Time (sec) Chemical Wafer RPM W/cm2 1 90 NH4OH 2% 60 1.85 2 10 DIW 60 1.85 3 Dry 2000 0 These direct comparison tests prove that the non-contact Megasonic method equals or exceeds the cleaning results achieved with the traditional brush cleaning under identical process flow and conditions. Figure 1: Post CMP clean particle counts 90nm threshold with D3586 slurry. Figure 1

Post Salicidation Clean: Removal of Unreacted Pt from High Pt Content NiPt Silicide

Introduction Silicides have been used in self-aligned processes for several generations of CMOS devices, with the aim of reducing the sheet resistance and providing stable Ohmic contacts with low contact resistance on gate, source and drain areas.1 To avoid bridging at the spacers and the isolation areas, after salicide formation, unreacted NiPt needs to be removed; simplified process flow is shown in Figure 1. Theoretically, strongly oxidizing wet clean chemistries should be able to remove Ni and/or Pt in the Ni Pt salicide. Xu et al.2 used a HF and HNO3 acid mix to remove unreacted NiPt (for 5% and 10% Pt content) at high etch rates with high selectivity to other materials exposed at the wafer surface. However, for higher Pt contents in Ni Pt salicide, the HF and HNO3 acid mix was unable to remove all the unreacted Pt (Figure 2). Other strongly oxidizing wet cleans like SPM (sulfuric peroxide mix) and aqua regia were used and found to be inconsistent; Ni Pt residues were found on the wafer surface intermittently. Therefore, we needed to find a stable high volume manufacturing (HVM) process for removing Ni high Pt residues. Approach The unreacted Ni high Pt residue was analyzed. Unlike previous generations of Ni-Pt, this residue was almost pure Pt. That meant that Ni was being preferentially dissolved from the Ni high Pt surface eventually resulting in a pure Pt layer. So to prevent the preferential dissolution of Ni in Ni high Pt binary alloys, wafer spin changes were used to add a physical component to the chemical dissolution. The intent was to use centrifugal force to remove the unreacted Ni Pt stringers from the wafer surface. Unfortunately, this approach did not work and pure Pt residues were still found on the wafer surface. Extending the duration of the current wet clean steps was found to increase the attack of the NiPt salicide while the unreacted Ni Pt residue was not eliminated. So a new wet clean chemistry was developed to completely removing all the unreacted Ni Pt consistently making the HVM ready process. Results Figure 3 shows the effect of using the new wet clean at the Ni Pt Strip 1 step. Complete removal of Ni high Pt residues was found. The experiment was found to be repeatable and verified on lots staggered in the production line by 2 weeks. Additional details and results will be provided in the complete presentation.

A multi-site clinical field study to evaluate the effectiveness of manual cleaning for flexible gastrointestinal endoscopes

An ATP bioluminesce assay (ATP Water Test), measuring organic bioburden including microbes, was used to monitor the cleanliness of flexible GI endoscopes after the manual cleaning step of the decontamination and disinfection process, in seven US hospitals.

A Medium-Scale 50 MWfuel Biomass Gasification Based Bio-SNG Plant: A Developed Gas Cleaning Process

Natural gas is becoming increasingly important as a primary energy source. A suitable replacement for fossil natural gas is bio-SNG, produced by biomass gasification, followed by methanation. A major challenge is efficient gas cleaning processes for removal of sulfur compounds and other impurities. The present study focuses on development of a gas cleaning step for a product gas produced in a 50 MWfuel gasification system. The developed gas cleaning washing process is basically a modification of the Rectisol process. Several different process configurations were evaluated using Aspen plus, including PC-SAFT for the thermodynamic modeling. The developed configuration takes advantage of only one methanol wash column, compared to two columns in a conventional Rectisol process. Results from modeling show the ability of the proposed configuration to remove impurities to a sufficiently low concentrations - almost zero concentration for H2S, CS2, HCl, NH3 and HCN, and approximately 0.01 mg/Nm3 for COS. These levels are acceptable for further upgrading of the gas in a methanation process. Simultaneously, up to 92% of the original CO2 is preserved in the final cleaned syngas stream. No process integration or economic consideration was performed within the scope of the present study, but will be investigated in future projects to improve the overall process.

Capillary origami of micro-machined micro-objects: Bi-layer conductive hinges

Recently, we demonstrated controllable 3D self-folding by means of capillary forces of silicon-nitride micro-objects made of rigid plates connected to each other by flexible hinges (Legrain et al., 2014). In this paper, we introduce platinum electrodes running from the substrate to the plates over these bendable hinges. The fabrication yield is as high as (77±2)% for hinges with a length less than 75μm. The yield reduces to (18±2)% when the length increases above 100μm. Most of the failures in conductivity are due to degradation of the platinum/chromium layer stack during the final plasma cleaning step. The bi-layer hinges survive the capillary folding process, even for extremely small bending radii of 5μm, nor does the bending have any impact on the conductivity. Stress in the different layers deforms the hinges, which does not affect the conductivity. Once assembled, the conductive hinges can withstand a current density of (1.6±0.4)×106A/cm2. This introduction of conductive electrodes to elastocapillary self-folded silicon-based micro-objects extends the range of their possible applications by allowing an electronic functionality of the folded parts.

Experimental investigation on tar produced from palm shells derived syngas using zeolite HZSM-5 catalyst

The efficiency of the gas cleaning step is one of the fundamental steps to the successful operation of biomass gasification technologies for power generation. In the present study, catalytic cracking is selected as the hot gas cleaning technology using zeolite HZSM-5 catalyst in order to reduce tar produced from palm shells gasification in the laboratory scale fixed bed reactor. The experimental conditions for average biomass particle size, nitrogen flow rate and percentage of zeolite HZSM-5 catalyst are in the range of 1.18–7.13 mm, 3–7 L/min, and 2–10 wt% respectively with constant air flow rate of 5 L/min to the inlet of the reactor. From the gas chromatographic analysis of the tar produced from the gasification process, it is found that the phenol in the tar is in the range of 5–8 vol% when the oxygen to nitrogen flow rate ratio is varied from 0.10 to 0.15. A decreasing trend in the phenol concentration is observed when oxygen to nitrogen ratio is increased. The overall oxygenated aromatic compounds in the tar content are comparable when operating with oxygen to nitrogen ratio of 0.12 and 0.15. The lowest concentration of phenol is achieved when 5 wt% of zeolite HZSM-5 catalyst is used with a reduction of 99% and 79% for oxygen to nitrogen ratio of 0.10 or 0.15 respectively when compared to the phenol concentration with the absence of the catalyst. Furthermore, higher percentage of the catalyst results in less chemical compounds found in tar. Tar content increased as lower concentration of oxygen content in gas mixture or larger palm shells particle size is used.

Analysis of microbial load on surgical instruments after clinical use and following manual and automated cleaning

We aimed to monitor the microbial load and identify the microorganisms recovered from surgical instruments after clinical use and following manual and automated cleaning. This experimental study was carried out in the Laboratory of Oral Microbiology and Anaerobes at the Federal University of Minas Gerais in Brazil. Microbial samples were taken from 125 surgical instruments used in 25 types of gastrointestinal surgeries. The average microbial load was 93.1 CFU/100 mL after clinical use and 41 CFU/100 mL and 8.24 CFU/100 mL on instruments following 2 sequential steps of manual cleaning, respectively, and 75 CFU/100 mL and 16.1 CFU/100 mL on instruments after automated cleaning. Surgical wound classification significantly affected the microbial load recovered on instruments. Coagulase-negative Staphylococcus, Escherichia coli, Pseudomonas spp, Stenotrophomonas maltophilia, and Acinetobacter baumannii complex were recovered. The average microbial load observed after the cleaning steps decreased, and the decrease in microbial load was more pronounced using the manual method compared with that observed using the automated method.

Characterization of copper precipitates on aluminum copper bond pads formed after plasma clean and de-ionized water exposure

Semiconductor bond pads made from aluminum and small percentages of copper is susceptible to galvanic corrosion. In galvanic corrosion, the cathode (copper precipitate) is usually protected by the aluminum oxide that covers the surface of aluminum which acts as the anode. However, when the aluminum oxide thickness is reduced by plasma cleaning, the precipitates can be exposed. When exposed precipitates come in contact with de-ionized water, galvanic corrosion takes place. Therefore, though plasma cleaning in general is supposed to improve semiconductor bond pad surface in preparation for package level interconnection, adding the plasma clean step just before a process with de-ionized water can cause bond pad corrosion through the galvanic reaction between the exposed precipitate (cathode) and the surrounding aluminum (anode). This paper aims to investigate the mechanism of corrosion and characterize corroded bond pads by using wire bond ball shear method.

Novel and rapid method for determination of organophosphorus pesticide residues in edible fungus using direct gas purge microsyringe extraction coupled on-line with gas chromatography–mass spectrometry

In this work a new analytical method for a rapid and simultaneous determination of 28 organophosphorus pesticides (OPPs) residues in edible fungus using gas purge microsyringe extraction (GP-MSE), coupled with on-line gas chromatography–mass spectrometry (GP-MSE-GC-MS) has been developed and optimized. GP-MSE, a novel gas flow liquid-phase microextraction technique, has been then fruitfully used as innovative and one-step extraction procedure, allowing a direct injection into the gas chromatograph coupled with a mass spectrometry detector (GC–MS) system without any further cleaning step. Once optimized, the GP-MSE-GC-MS analysis procedure showed reproducibility values, resolutions, linear responses, detection and quantification limits that allowed to consider this method suitable for the analysis of the 28 OPPs in real samples. Furthermore, OPP recoveries and the relative standard deviations (RSDs) ranged from 85.26% to 100.21%, and from 1.6% to 6.9%, respectively. This procedure was then used for the analysis of real samples and the obtained results were compared with those of ultrasonic extraction–solid phase extraction. Among the 28 OPPs, 14 of them were found in Lentinus edodes and Enoki mushrooms fungus samples, with a total concentrations of 112.7 and 210.7μgkg−1, respectively. This work demonstrated then that GP-MSE-GC-MS provided a highly efficient, solvent-saving, accurate and sensitive quantitative analysis method for a rapid determination of OPPs in edible fungus.

Tissue Microarray Technology for Molecular Applications: Investigation of Cross-Contamination between Tissue Samples Obtained from the Same Punching Device

Background: Tissue microarray (TMA) technology allows rapid visualization of molecular markers by immunohistochemistry and in situ hybridization. In addition, TMA instrumentation has the potential to assist in other applications: punches taken from donor blocks can be placed directly into tubes and used for nucleic acid analysis by PCR approaches. However, the question of possible cross-contamination between samples punched with the same device has frequently been raised but never addressed. Methods: Two experiments were performed. (1) A block from mycobacterium tuberculosis (TB) positivetissue and a second from an uninfected patient were aligned side-by-side in an automated tissue microarrayer. Four 0.6 mm punches were cored from each sample and placed inside their corresponding tube. Between coring of each donor block, a mechanical cleaning step was performed by insertion of the puncher into a paraffin block. This sequence of coring and cleaning was repeated three times, alternating between positive and negative blocks. A fragment from the 6110 insertion sequence specific for mycobacterium tuberculosis was analyzed; (2) Four 0.6 mm punches were cored from three KRAS mutated colorectal cancer blocks, alternating with three different wild-type tissues using the same TMA instrument (sequence of coring: G12D, WT, G12V, WT, G13D and WT). Mechanical cleaning of the device between each donor block was made. Mutation analysis by pyrosequencing was carried out. This sequence of coring was repeated manually without any cleaning step between blocks. Results/Discussion: In both analyses, all alternating samples showed the expected result (samples 1, 3 and 5: positive or mutated, samples 2, 4 and 6: negative or wild-type). Similar results were obtained without cleaning step. These findings suggest that no cross-contamination of tissue samples occurs when donor blocks are punched using the same device, however a cleaning step is nonetheless recommended. Our result supports the use of TMA technology as an accessory to PCR applications.

Comparison of sampling procedures and microbiological and non-microbiological parameters to evaluate cleaning and disinfection in broiler houses

Cleaning and disinfection of the broiler stable environment is an essential part of farm hygiene management. Adequate cleaning and disinfection is essential for prevention and control of animal diseases and zoonoses. The goal of this study was to shed light on the dynamics of microbiological and non-microbiological parameters during the successive steps of cleaning and disinfection and to select the most suitable sampling methods and parameters to evaluate cleaning and disinfection in broiler houses. The effectiveness of cleaning and disinfection protocols was measured in six broiler houses on two farms through visual inspection, adenosine triphosphate hygiene monitoring and microbiological analyses. Samples were taken at three time points: 1) before cleaning, 2) after cleaning, and 3) after disinfection. Before cleaning and after disinfection, air samples were taken in addition to agar contact plates and swab samples taken from various sampling points for enumeration of total aerobic flora,Enterococcus spp., andEscherichia coli and the detection ofE. coli andSalmonella. After cleaning, air samples, swab samples, and adenosine triphosphate swabs were taken and a visual score was also assigned for each sampling point. The mean total aerobic flora determined by swab samples decreased from 7.7 ± 1.4 to 5.7 ± 1.2 log CFU/625 cm2 after cleaning and to 4.2 ± 1.6 log CFU/625 cm2 after disinfection. Agar contact plates were used as the standard for evaluating cleaning and disinfection, but in this study they were found to be less suitable than swabs for enumeration. In addition to measuring total aerobic flora,Enterococcus spp. seemed to be a better hygiene indicator to evaluate cleaning and disinfection protocols thanE. coli. All stables wereSalmonella negative, but the detection of its indicator organismE. coli provided additional information for evaluating cleaning and disinfection protocols. Adenosine triphosphate analyses gave additional information about the hygiene level of the different sampling points.

High power density supercapacitors based on the carbon dioxide activated d-glucose derived carbon electrodes and 1-ethyl-3-methylimidazolium tetrafluoroborate ionic liquid

The electrochemical impedance spectroscopy, cyclic voltammetry, constant current charge/discharge and the constant power discharge methods have been applied to establish the electrochemical characteristics of the electrical double–layer capacitor (EDLC) consisting of the 1-ethyl-3-methylimidazolium tetrafluoroborate (EMImBF4) ionic liquid and microporous carbon electrodes. Microporous carbon material used for preparation of electrodes (GDAC – glucose derived activated carbon), has been synthesised from D-(+)-glucose by the hydrothermal carbonization method, including subsequent pyrolysis, carbon dioxide activation and surface cleaning step with hydrogen. The Brunauer-Emmett-Teller specific surface area (SBET = 1540 m2 g−1), specific surface area calculated using the non–local density functional theory in conjunction with stable adsorption integral equation using splines (SAIEUS) model SSAIEUS = 1820 m2 g−1, micropore surface area (Smicro = 1535 m2 g−1), total pore volume (Vtot = 0.695 cm3 g−1) and the pore size distribution were obtained from the N2 sorption data. The SBET, Smicro and Vtot values have been correlated with the electrochemical characteristics strongly dependent on the carbon activation conditions applied for EDLCs. Wide region of ideal polarizability (ΔV ≤ 3.2 V), very short charging/discharging time constant (2.7 s), and high specific series capacitance (158 F g−1) have been calculated for the optimized carbon material GDAC-10h (activation of GDAC with CO2 during 10 h) in EMImBF4 demonstrating that this system can be used for completing the EDLC with high energy- and power densities.

Pasarela en la Ronda de la Bahía de Santander

The footbridge arises from the need to connect the locations of Parbayón and Cacicedo, overcoming the longitudinal division of the landscape made by the dual carriageway and providing a striking visual reference point on the site. Its architecture, rooted by its massive abutments, rises in one clean and clear step through its twin projecting walls, and flies over the highway by means of its elegant balcony beam, returning again to the earth.This footbridge is formed by a 70.7m long balcony beam, fixed to both projecting walls at either end. The flying beam is constructed of a steel-concrete composite semi-circular section 1.45m thick. The abutments, the massive concrete pieces, are used as counterweights to anchor the structure to the terrain and gracefully achieve the geometrical and structural transition between the terrain and twin projecting walls.

Dry Phosphorus silicate glass etching and surface conditioning and cleaning for multi-crystalline silicon solar cell processing

As an alternative to the wet chemical etching method, dry chemical etching processes for Phosphorus silicate glass (PSG) layer removal using Trifuormethane /Sulfur Hexafuoride (CHF 3/SF6) gas mixture in commercial silicon-nitride plasma enhanced chemical vapour deposition (SiN-PECVD) system is applied. T e dependence of the solar cell performance on the etching temperature is investigated and optimized. It is found that the SiN-PECVD system temperature variation has a significant impact on the whole solar cell characteristics. A dry plasma cleaning treatment of the Si wafer surface after the PSG removal step is also investigated and developed. The cleaning step is used to remove the polymer f lm which is formed during the PSG etching using both oxygen and hydrogen gases.By applying an additional cleaning step, the polymer film is deposited on the silicon wafer surface after PSG etching is eliminated. T e effect of different plasma cleaning conditions on solar cell performance is investigated. Af er optimization of the plasma operating conditions, the performance of the solar cell is improved and the overall gain in efficiency of 0.6 % absolute is yielded compared to a cell without any further cleaning step. On the other hand, the best solar cell characteristics can reach values close to that achieved by the conventional wet chemical etching processes demonstrating the effectiveness of the additional O2/H2 post cleaning treatment

Determination of Resveratrol and Piceid Isomers in Bee Pollen by Liquid Chromatography Coupled to Electrospray Ionization-Mass Spectrometry

A new method has been developed to determine resveratrol and piceid isomers in bee pollen using liquid chromatography (LC) coupled to electrospray ionization-mass spectrometry (ESI-MS). An efficient extraction procedure has also been proposed (average analyte recoveries were between 89 and 96 %); this involved a cleaning step with hexane, a solid–liquid extraction using a mixture of ethanol and water (80:20, v/v), and a concentration step in a rotary evaporator. The separation of all the compounds was achieved using a C18 column (150 × 4.6 mm) and a mobile phase composed of 1 % (v/v) formic acid in water and acetonitrile at a flow rate of 0.8 mL/min. The method was fully validated in terms of selectivity, limits of detection (LOD) and quantification (LOQ), linearity, precision, and accuracy. The LOD and LOQ values ranged from 10 to 25 and 35 to 80 μg/kg, respectively. Finally, the proposed method was applied to analyze bee pollen samples from different origins.

Nickel Selective Etch for Contacts on Ge Based Devices

of high mobility channels materials like Ge. The introduction of Ge as channel material has already shown significant interests in term of device performance enhancement [1,2]. However, the use of Ge in CMOS integration has raised new challenges in terms of clean or wet etch steps since significant Ge loss occurs when it oxidizes in aqueous media.

Improvement of Silicon Solar Cell Substrates by Wet-Chemical Oxidation Studied by Surface Photovoltage Measurements

The deposition of thin and ultra-thin layers requires extremely clean, smooth and defect-free Silicon (Si) substrate surfaces as starting point. The preparation-induced surface micro-roughness and surface coverage of the substrates often affect the initial layer growth, the morphology or the adhesion of deposited layers. Si device fabrication includes multiple wet cleaning and etching steps involving different oxidizing and etching solutions, which modify the surface electronic properties according to fixed charges and defect states present on the surface. Depending on the details of the device structure, surface conditioning methods have to be carefully optimized to achieve the desired electronic interface properties.

Investigations on residual chemical contamination on machining aluminum components of turbo molecular pumps

In the recent Extreme Ultra Violet Lithography (EUVL) process developed in microelectronics, the presence of hydrocarbon molecules is critical for the performances of the optics. Hydrocarbons can cause carbon deposit on the mirrors surfaces which reduces the reflectivity of the mirrors (1 nm carbon deposit = 1% reflectivity loss). As the EUVL system cannot be baked in situ, the residual carbon contamination on each component integrated in the Extreme Ultra Violet (EUV) tool becomes critical. The study presented herein, deals with the problem of a possible carbon contamination source due to the EUVL pumping system. We report the study of a research method of the contamination sources of turbo molecular pumps (stator and rotor), suitable for the pump manufacturing environment. With the support of TD-GCMS/FID, a RGA characterization of the residual carbon contamination is made. A clear association between RGA spectrum features and characteristics of the cleaning process has been established. In particular, the final cleaning step in the pump manufacturing is a possible source of contamination. Therefore, the detergent concentration in the cleaning process was investigated. Correlations were made with XPS (X-ray photoemission spectrometry) characterizations of stator and rotor surfaces.

Traceability of mass in air to mass in vacuum: results on the correlation between the change in mass and the surface chemical state

For the study of the practical means of a dissemination of the redefined kilogram, measurements on 1 kg mass artefacts were carried out, combining high precision mass determination and element-specific surface chemical analysis by x-ray photoelectron spectroscopy (XPS). In a sequence various processes were applied to steel, rhodium and gold artefacts. We studied the transfer from mass in air to mass in vacuum, several steps of hydrogen low-pressure plasma cleaning, cyclic exposure to air and vacuum and the natural contamination in air with time. Values for the gain and loss of mass due to the processes applied are provided. Reversible and irreversible sorption effects could be separated by means of mass determination, XPS and quartz crystal micro-balance. Possible pathways for the traceability of mass in vacuum to mass in air are discussed.