Elżbieta Przyk

Permeation passive sampling as a tool for the evaluation of indoor air quality

Time-weighted average concentrations of selected volatile organic air pollutants were determined in eight apartments in the city of Gdansk (Poland) using permeation passive sampling. The samplers were recalibrated prior to use by controlled exposure to standard gaseous mixtures of the analytes. Small but statistically significant differences were found between the calibration constants determined initially and after one year of field use of the samplers for some of the analytes. The results obtained by the passive sampling technique were compared to those obtained by dynamic sampling using active charcoal-filled tubes, and dynamic sampling using Tenax-TA tubes. Overall, the results obtained by the three techniques were similar. Maximum allowable concentrations of the analytes were not exceeded in any of the apartments examined. The results of total volatile organic compounds determination indicated that some VOCs were unaccounted for in the experiment. The effect of outside air infiltration on indoor air quality was evaluated by comparing analyte concentrations in indoor air and in outdoor air in the very vicinity of the apartment. This effect was found to be minimal.

Use of porous glass and silica gel as support media of a surface compound for generation of analytes in gaseous standard mixtures. New method for the determination of the amount of analyte generated.

The paper presents a new method for the determination of a volatile component of a gaseous standard mixture obtained by thermal decomposition of a suitable surface compound. The amount of the analyte generated (under given conditions of thermal decomposition) per unit of mass of the chemically modified material has been determined exclusively on the basis of measuring generation time. Therefore, the total error of the determination of the amount of a standard compound depends solely on the respective errors of weighing the material and measuring its decomposition time (both being direct measurements). This new method permits obtaining a few measuring points on the basis of a single sample of the material with chemically modified surface.

Changes in concentration levels of selected VOCs in newly erected and remodelled buildings in Gdansk

Volatile organic compounds such as benzene, toluene, butyl acetate, ethylbenzene, m-xylene, styrene and m-dichlorobenzene were measured in three newly erected and remodelled dwellings. The present study also attempted to examine the time dependence of concentrations of selected VOCs in each investigated dwelling. This was accomplished by at least triplicate measurements of the IAQ. To collect a series of air samples the active and passive methods were used. In both cases activated charcoal was applied as a sorption medium. The samples were recovered by solvent extraction, and analysed by capillary column gas chromatography, employing a flame ionisation detector. The experimental results showed that MAC values for analysed VOCs were exceeded (even a few orders of magnitude) for the measurements made before inhabiting of the occupants, in every investigated dwelling. The concentrations of the investigated VOCs decreased significantly with time, which should be expected, although in some cases the levels of selected VOCs remained still high. Our experience indicates that parallel application of two different indoor air sampling techniques to determine analytes of interest, though more laborious and time consuming, can lead to significant conclusions concerning indoor air quality in monitored spaces.

Calibration in Metrological Approach

Abstract This paper considers the present‐day approach to the calibration process. Various definitions and terminology applied to measurements in analytical chemistry are not always consistent and straightforward. The terms referring to calibration, such as types of calibration, calibrants, validation, uncertainty of reference materials, and calibration process, are here explained and discussed. The establishing of traceability through the calibration process is also considered. This work has been financially supported by the Polish State Committee on Scientific Research (KBN) and UE grants (VI‐RM and QUA‐NAS).

Applicability of Silicone Membrane Passive Samplers for Monitoring of Indoor Air Quality

ABSTRACT A series of experiments were conducted to investigate the permeability of membranes made of silicone foil with respect to selected volatile organic compounds such as butanol, benzene, toluene, butyl acetate, ethylbenzene, m- xylene, styrene, m- dichlorobenzene. On the basis of model experiments the calibration constants k for 18 passive samplers were determined (with respect to each compound present in the gaseous standard mixture). The obtained calibration constants found are characterised by good precision (except for butanol, relative standard deviation are not greater than 9%). The comparison of the calibration constants for the samplers with silicone membrane of 50 μm thick with those obtained for samplers with polyethylene membrane of 15.5 μm shows that silicone membrane samplers will give higher enrichment factors for the compounds studied.

Generation of gaseous mixtures of ethene on the basis of thermal decomposition of compound bonded to silica gel surface – Single and multipoint calibration of a thermal decomposition‐gas chromatography system

The paper presents a new method of determination of a volatile component (ethene) of gaseous standard mixtures obtained by thermal decomposition of a suitable surface compound. This method is based on a simple mathematical relationsphip (function of a single variable). The amount of the analyte generated (under given, chosen conditions of thermal decomposition) per unit of mass of the source material has been determined exclusively on the basis of measuring the standard generation time.V

Preparation of Gaseous Standard Mixtures: Methods for Controlling the Amount of Components Generated in the Process of Thermal Decomposition of Immobilized Compounds

Gaseous standard mixtures play an important role in characterizing and checking the applicability of new analytical procedures. In this case gaseous standard mixtures can be treated as a special kind of reference material (validation process requires the use of so-called matrix reference materials). The selection of a method of generation of gaseous standard mixtures with the desired characteristics depends on the nature of the analyte and diluent gas, as well as on the required concentration of analytes in the mixture. Recently, dynamic methods of generation of gaseous standard mixtures are becoming more and more common. These include the method based on thermal decomposition of immobilized compounds. The generation of the measured component takes place as a result of heating of a sample of solid support with chemically modified surface. During a chemical reaction initiated by sufficiently high temperature, the immobilized compound undergoes decomposition or rearrangement accompanied by the release of a specific volatile compound. Various amounts of the analyte per unit time can be obtained by adjusting the conditions of the thermal decomposition process. This article describes the possibility of varying the amount of a measured component through the adjustment of conditions of drying the solid support or of the process of chemical modification of its surface. The principle of this technique is exemplified by the generation of a mixture containing ethene as the analyte. Porous glass was used as a solid support. The proposed technique was used for the generation of gaseous standard mixtures for the calibration of a thermal desorber-gas chromatograph-flame ionization detector (TD-GC-FID) system.

Automated analyser for monitoring trace amounts of volatile chloro-organic compounds in recirculated industrial water

An automated analyser of volatile chloro-organic compounds in water was constructed and tested using standard mixtures of dichloromethane and dichloroethane. It was based on continuous, countercurrent gas stripping of the liquid sample followed by periodic trapping of the analytes on two traps alternately connected to the bubbler outlet, and thermal desorption. When one trap performed adsorption, the other underwent desorption and cooling. Analytes were detected by an ECD detector. Integration, calibration, calculations and overall operating cycle control was performed by a microcomputer. The instrument guarantees a 0.02 ppm Cl (w/w) detection limit, a 0—2 ppm detection range and 2 months of autonomous operation. Results are reported every 13 min.