Heat treatment of wood is used to improve its durability and simensional stability [1], but it might affect the emission of volatile organic compounds (VOCs) [2], and consequently indoor air quality. Indoor air quality has become a public health issue of increasing concern during the last decades [3], since frequently air pollutants belonging to VOCs are more concentrated indoors than outdoors [4]. Proton transfer reaction time-of-flight mass spectrometry (PTR-ToF-MS) is a rapid, high sensitivity and non-invasive method employed for the detection and quantification of VOCs [5]. The purpose of this study was to use the PTR-ToF-MS to compare the effect on VOCs emission from Norway spruce (Picea abies Karst) and larch (Larix decidua xx ) treated with THERMOVACUUM technology at two different temperatures 220 and 165 C with the same species treated with Thermowood system at 220 C. Moreover not treated samples were analysed as reference. Thin slice of Wood samples were collected after removing the external layer of wood and 0.3 g of each samples were put in a vials. The samples occupied the first 3 cm of the vials in order to have the same conditions for all the samples. The headspace of the samples was analysed by direct injection on the PTR-ToF-MS 8000 (Ionicon Analytik GmbH, Innsbruck, Austria) in its standard configuration. The drift tube was conditioned at 600 V, with a pressure of 2.25 mB and a temperature of 110 ºC. Samples has been analyzed automatically by a Gerstel autosampler connected to PTR-ToF-MS inlet. PTR-ToF-MS analysis allowed the identification of more than 400 mass peaks. In the following only the peaks with an average concentration higher than 0.5 ppbv (parts per billion by volume) were considered. ANOVA and post-hoc Tukey test were performed at 0.01 confidence level in order to evaluate the differences between treatments. Mass peaks tentatively identified as important VOCs, such as formaldehyde, methanol, acetaldehyde, acetone, acetic acid and monoterpenes had a higher concentration in the head-space of Thermowood samples as compared with samples treated with the thermo-vacuum technology. In order to graphically visualize the ANOVA nd Tukey results, principal components analysis (PCA) was performed using the significant mass peaks (Figure 1). As displayed in the figure, PC 1 and 2 explain together 75% of the total variance. PC 1 llowed for a good separation of the samples from superheated steam treated timber, and for the separation of the samples from wood treated under thermo-vacuum technology against not treated samples. On the other hand, PC 2 allowed for the separation of Thermowood samples from both types of wood. These results indicate a higher VOCs emission from Thermowood respect to thermovacuum process. In addition, wood treated with the thermo-vacuum technology seems to have a VOC emission close to not treated samples, and therefore much lower than that emitted by Thermowood samples. PTR-ToF-MS allows the rapid and non-invasive measurement of VOCs emission also in this context providing valuable information on the effect of wood treatment. Being an online technique the possible application to the real time monitoring of the treatment process is envisaged.
Rapid assessment by PTR-ToF-MS of the effect on volatile compound emission of different heat treatments on larch and spruce
Santoni I;Cuccui I;Allegretti;
2014
Abstract
Heat treatment of wood is used to improve its durability and simensional stability [1], but it might affect the emission of volatile organic compounds (VOCs) [2], and consequently indoor air quality. Indoor air quality has become a public health issue of increasing concern during the last decades [3], since frequently air pollutants belonging to VOCs are more concentrated indoors than outdoors [4]. Proton transfer reaction time-of-flight mass spectrometry (PTR-ToF-MS) is a rapid, high sensitivity and non-invasive method employed for the detection and quantification of VOCs [5]. The purpose of this study was to use the PTR-ToF-MS to compare the effect on VOCs emission from Norway spruce (Picea abies Karst) and larch (Larix decidua xx ) treated with THERMOVACUUM technology at two different temperatures 220 and 165 C with the same species treated with Thermowood system at 220 C. Moreover not treated samples were analysed as reference. Thin slice of Wood samples were collected after removing the external layer of wood and 0.3 g of each samples were put in a vials. The samples occupied the first 3 cm of the vials in order to have the same conditions for all the samples. The headspace of the samples was analysed by direct injection on the PTR-ToF-MS 8000 (Ionicon Analytik GmbH, Innsbruck, Austria) in its standard configuration. The drift tube was conditioned at 600 V, with a pressure of 2.25 mB and a temperature of 110 ºC. Samples has been analyzed automatically by a Gerstel autosampler connected to PTR-ToF-MS inlet. PTR-ToF-MS analysis allowed the identification of more than 400 mass peaks. In the following only the peaks with an average concentration higher than 0.5 ppbv (parts per billion by volume) were considered. ANOVA and post-hoc Tukey test were performed at 0.01 confidence level in order to evaluate the differences between treatments. Mass peaks tentatively identified as important VOCs, such as formaldehyde, methanol, acetaldehyde, acetone, acetic acid and monoterpenes had a higher concentration in the head-space of Thermowood samples as compared with samples treated with the thermo-vacuum technology. In order to graphically visualize the ANOVA nd Tukey results, principal components analysis (PCA) was performed using the significant mass peaks (Figure 1). As displayed in the figure, PC 1 and 2 explain together 75% of the total variance. PC 1 llowed for a good separation of the samples from superheated steam treated timber, and for the separation of the samples from wood treated under thermo-vacuum technology against not treated samples. On the other hand, PC 2 allowed for the separation of Thermowood samples from both types of wood. These results indicate a higher VOCs emission from Thermowood respect to thermovacuum process. In addition, wood treated with the thermo-vacuum technology seems to have a VOC emission close to not treated samples, and therefore much lower than that emitted by Thermowood samples. PTR-ToF-MS allows the rapid and non-invasive measurement of VOCs emission also in this context providing valuable information on the effect of wood treatment. Being an online technique the possible application to the real time monitoring of the treatment process is envisaged.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
