The presence of Liquid Crystal
Monomers in house dust and public
Authors: Filip Berner-Branzell, Elin Forsberg, Emma Overgaard, Isabel Häggblom. Course: Analytical science and forensics 15hp, KE104G
Supervisor: Maria Björnsdotter Date: 2020-05-29
Liquid crystal monomers (LCMs) are byproducts that can be expected in LCD screens and they have been found to be released into the environment due to breakage and usage of LCD-products. The presence of these substances in other pieces of technology is likely but unknown. They are a new type of potentially hazardous environmental pollutants that has yet to be fully researched. Some LCMs that have been studied show tendencies for the ability to bioaccumulate and have possible effects on different organs in living organisms. This study serves to research if LCMs can be found in dust in Swedish homes, screen repair-shops, phone-shops, or electric areas at a recycling station. For this purpose, dust samples were collected at the mentioned locations. Swipe samples from screens located in these environments were also collected. The samples were later analyzed with gas chromatography coupled with mass spectrometry. LCMs were found in 6 out of 10 dust samples and in 3 out of 11 swipe samples. The swipe samples in which LCMs were found were not from home environments. Some LCMs seemed to be more common and some LCMs were more common in the same types of environments.
Table of contents
1.1 Background 3
1.2 Aim 3
2 Materials and Methods 4
2.1 Sampling 4
2.1.1 Dust samples 4
2.1.2 Swipe samples 4
2.2 Sample handling 4
2.3 Chemicals and materials 5
2.4 Sample preparation 5 2.4.1 Dust samples 5 2.4.2 Swipe samples 5 2.5 Instrumental analysis 5 2.6 Quality control 6 3 Results 7 4 Discussion 8 6 Conclusions 10 7 References 11 Appendix 1 13 Appendix 2 14 Appendix 3 15 Appendix 4 16 Appendix 5 16 Appendix 6 18 Appendix 7 20 Appendix 8 23 Appendix 9 24
3 1 Introduction
Liquid crystals (LCs) were first documented in 1888 by an Austrian botanist/chemist named Friedrich Reinitzer while conducting experiments with the chemical cholesteryl benzoate extracted from carrots (Daucus Carota) (1). He found that the chemical had two clear melting points; the first at 145°C and the second at 179°C. At the first one it transformed from a solid-state to a generally cloudy liquid with a bluish hue. At the second melting point, the cloudiness disappeared and the liquid was transparent (2). Reinitzer found that the chemical at the first cloudy state at 145°C had an ability to reflect polarized light and structurally direct it (1). In collaboration with the German physicist, Otto Lehman the cloudy state at 145°C was further investigated in-depth and they found that the cloudiness occurred because of the elongated form of the molecule in this state and variable structural positioning. The term liquid crystals were eventually coined (1,2).
It was not until 1960 that the wavelength altering abilities of LCs started were being thoroughly researched and utilized for future display devices, ultimately resulting in Liquid Crystal Display (LCD)-technology (3). Liquid crystal monomers (LCMs) are byproducts that can be expected in LCD screens and they have been found to be released into the environment due to breakage and usage of LCD-products (4). Free LCMs have been detected in both residential dusts and in dust collected from industrial areas (5).
LCMs generally have a diphenyl backbone structure and where phenyl ring hydrogen atoms are replaced by various functional groups such as; cyano, chlorine, bromine, or fluorine. Some LCMs are considered to have an especially high environmental impact through accumulating in living organisms (bioaccumulation), often in organs such as the liver (6). Highly fluorinated substances generally form stable and slowly degradable substances. The more fluorine groups the more stable the substance (7). LCMs can potentially contain up to at least four fluorine groups (6).
Each LCD-screen contains a relatively small amount of LCMs (0.6 mg/cm2). There is limited knowledge about their environmental impact and very few studies have been made on prolonged exposure to the compounds (6). One of the few studies that have been conducted on the subject showed that even low doses of LCMs resulted in potential health effects in catfish (8). This was performed by mixing LCMs in the food of the fish for 40 days and measuring the levels of three major antioxidant-enzymes, which all showed significantly increased values (8).
In another study, Su et al. used computer simulations and found that out of 362 tested LCMs, 87 were found to have potential resistance towards degradation and should therefore, be considered an environmental hazard (5). Professor John Giesy, who was one of the authors of the study, proclaimed in a news article for SciTech daily that some LCMs were shown to exhibit characteristics linked to decreased function in organs such as thyroid and gallbladder (4).
LCMs are a new type of potentially hazardous environmental pollutants that has yet to be fully researched. The aim of this project was to determine if LCMs can be found in dust in Swedish homes, screen repair-shops, phone shops, or electric areas at a recycling station. The study was limited to a small number of locations.
4 2 Materials and Methods
Dust samples (n=10) were taken from ten different locations; five home environment locations, three screen-related commercial stores, one chemistry lab, and one recycling center. Swipe samples (n=11) were taken from seven of these locations. A total of 21 samples were collected. For a list of samples, see appendix 9.
2.1.1 Dust samples
Dust was collected by using a dust collection filter made of nylon, which was fastened to the nozzle of the vacuum cleaner with a rubber band. Dust was collected from a selected area. The collection bags were then removed from the vacuum cleaner, sealed and then put in marked polyethylene bags.
The five home environments were inside private apartments. The three samples from screen-related commercial stores were taken inside the stores. Out of these, one was a phone store in a shopping mall with open access to the rest of the mall. The other two were phone-repair shops. The dust samples were taken by vacuuming along the walls and underneath furniture. In the case of not having an adequate amount of dust, more dust was collected in other places where dust was visible. The sample from the recycling center was taken in an outside environment where old and broken electronics are thrown out. In this case the sample was collected by vacuuming in the containers where the electronics were thrown out, as well as around these containers and on some electronic devices.
2.1.2 Swipe samples
Swipe samples were collected by adding isopropanol to a Kleenex and the entire area of the selected screen was swiped. The Kleenex was then wrapped in aluminum foil that had been baked in an oven at 450 °C overnight and put in marked polyethylene bags.
The swipe samples were collected from three private apartments (home environment 3-5) where a resident LCD-screen was swiped. The rest of the swipe samples were collected at the electric area of the recycling center, phone-repair shops 1 and 2, and a phone shop where public LCD-screens were swiped. In the phone shop three swipe samples were collected, the swipe samples include a TV screen, a tablet and a smartphone. The samples were collected in the public area of the phone shop. In the screen-repair shops four samples were collected. At the first screen repair shop the single swipe sample was collected from a computer screen in the area where electronics are sold. In the second phone-repair shop three swipe samples were taken in their repair room. Two of the swipe samples were collected from the screens of two broken smartphones and the third sample was collected from a computer screen. In the recycling station one swipe sample was collected from a broken screen.
2.2 Sample handling
All samples were stored in sealed plastic zipper bags to prevent contamination. They were stored at room temperature and under normal conditions.
5 2.3 Chemicals and materials
The filters used for dust sampling was made of Nylon purchased from Allied Filter Fabrics PTY Ltd, Australia. 750 µL Nonsterile Micro-Centrifugal PVDF filters was from Thermo Scientific™. Hexane and isopropanol was from Fisher Scientific. Full names, abbreviations and information about the selected LCMs can be found in Table 1 and Appendix 6. Analytical standards for 3, 4, 5, 6, 10, 12, 13, 16, 18, 19, LCM-21, LCM-31 and LCM-33 were purchased from Tokyo Chemical Industry..
2.4 Sample preparation
2.4.1 Dust samples
All the equipment in contact with the samples were rinsed with hexane to minimize contamination. Samples were taken out of their concealment and spread out on a 500 µm sieve. Sieving was performed until enough amount of sieved dust could be collected. If the amount was not deemed adequate, some pressure by hand was put on the dust when sieving. Approximately 50-100 mg of sieved dust (<500 µm) were weighted in 15 mL pp-tubes and the weight was recorded, see table 4 in appendix 1. This procedure was repeated for all the ten dust samples and equipment used was rinsed with hexane between samples.
The dust samples were extracted with 3 mL of hexane by ultrasonication for 15 minutes followed by vortex for 20 seconds. The separation between the liquid phase and the solid dust was done by centrifugation for 10 minutes at 10 000 rpm. The supernatant was transferred to new pp-tubes that had been rinsed with hexane. The extraction was repeated and the supernatants were combined. 2.4.2 Swipe samples
The ten swipe samples, including the field blank, were placed in 50 mL pp-tubes. Extraction was done with 13 mL hexane by ultrasonication for 15 minutes followed by vortex for 20 seconds, making sure that the entire Kleenex was soaked in solvent. The separation between the liquid phase and the Kleenex was done by centrifugation for 10 minutes at 8 000 rpm. The supernatant was collected and transferred to new pp-tubes that had been rinsed with hexane. The extraction was repeated with 5 mL hexane and the supernatants were combined. The total volume om extract (after combining the supernatants) differed slightly between samples (Table 5 in appendix 2).
After both dust and swipe samples were extracted twice, the extracts were fully evaporated with a gentle stream of N2. The extracts were reconstituted in approximately 1 mL of hexane and then filtered through PVDF centrifuge filters. After centrifugation for 5 minutes at 3000 rpm, the extracts were transferred to GC vials and evaporated to 500 µL. The GC vials were closed and the extracts were injected onto the GC-MS.
2.5 Instrumental analysis
The analysis was performed using a gas chromatograph coupled with a high-resolution mass spectrometer (GC-HRMS, Q Exactive Trace 1310, Thermo Scientific) operating in full scan mode with a resolution of 60 000 fwhm at m/z 200. The injection was done by using a 1 µL splitless injection and separation was done on a DB5-MS column (30 m). The carrier gas used was helium, which had a flow rate of 2 µL/min. The temperature program used in the analysis started with an initial temperature of 70°C. The temperature was then raised to 205°C at a rate of 8°C/min. The
6 second increase in temperature was to 325°C at a rate of 4°C/min. This temperature was held for 8 minutes.
2.6 Quality control
Two field blanks were collected; one for the dust sampling and one for the swipe samples. The field blank for dust sampling was collected by applying a dust collection filter to the vacuum cleaner and then putting it in a sealed polyethylene bag. The field blank for swipe samples was collected by wetting a Kleenex with isopropanol and wrapping it in pre-burned aluminum foil. This was done at the phone-shop. A procedural blank was included during the sample preparation. Two quality control (QC) samples were included and treated in the same way as the samples in order to investigate the performance of the extraction method in terms of extraction recovery. One QC sample consisted of solvent (hexane) and the other contained dust from one of the sampling locations (sample 1: chemistry lab). These were both spiked with a known amount of LCMs (80 ng) and are hereby referred to as solvent spike and matrix spike, respectively.
Quantification was done by external calibration. Detailed information about how the external calibration was done can be found in Appendix 4. The instrumental limit of detection (LOD) was based on the lowest standard concentration with a signal to noise (S/N) ratio of at least three. The LOD was in the range 0.6 to 7.9 pg/µL. For LOD for respective LCMs, see Appendix 8.
7 3 Results
The recovery of the extraction method was found to be low, ranging from 3.2 to 11 % in the matrix spike and 4.5 to 13 % in the solvent spike, see table 1. The reported concentrations were not recovery corrected and could therefore be underestimating the actual concentrations in the samples. No LCMs were observed in the procedural blank nor in the field blanks. The LOD based on the lowest standard concentration with S/N of at least three and a sample amount of 50 mg was in the range 0.0060 to 0.079 ng/mg.
Table 1. Extraction recovery (%) of LCMs based on spiked QC samples (matrix and solvent).
Abbreviation Chemical name Formula Matrix
spike Solvent spike
LCM-3 1-methoxy-4-(4-propylcyclohexyl)cyclohexane C16H30O 11 13 LCM-4 1-(prop-1-enyl)-4-(4-propylcyclohexyl)cyclohexane C18H32 8.1 9.7 LCM-5 1-ethoxy-2,3-difluoro-4-(4-propylcyclohexyl)benzene C17H24F2O 7.7 8.1 LCM-6 4-methyl-4'-pentylbiphenyl C18H22 8.4 8.0 LCM-10 1-methyl-4-(4-(4-vinylcyclohexyl)cyclohexyl)benzene C21H30 3.2 4.5 LCM-12 4-[difluoro(3,4,5-trifluorophenoxy)methyl]-3,5-difluoro-4'-propylbipheny C22H15F7O 11 11 LCM-13 1-methyl-4-(4-(4-propylcyclohexyl)cyclohexyl)benzene C22H34 8.0 8.6 LCM-16 1-ethyl-4-(4-(4-propylcyclohexyl)phenyl)benzene C23H30 8.6 9.3 LCM-18 1-ethoxy-2,3-difluoro-4-(4-(4-propylcyclohexyl)cyclohexyl)benzene C23H34F2O 7.8 8.5 LCM-19 4''-ethyl-2'-fluoro-4- propyl-1,1':4',1''-terphenyl C23H23F 8.4 8.4 LCM-21 4-ethoxy-2,3-difluoro-4'-(4-propylcyclohexyl)biphenyl C23H28F2O 8.6 9.1 LCM-31 3,4-difluoro-4'-[4'-propyl-1,1'-bi(cyclohexyl)-4-yl]biphenyl C27H34F2 8.7 9.2 LCM-33 3,4-difluoro-4'-[4'-pentyl-1,1'-bi(cyclohexyl)-4-yl]biphenyl C29H38F2 11 10
8 LCMs were detected in six dust samples and in three swipe samples, see tables 2 and 3. For detailed information about the GC-MS detection of samples and controls, see appendix 7. The most common LCM found was LCM-12, which was found in four dust samples. The concentration of LCMs in dust samples was in the range 63 to 430 ng/g (Table 2). The absolute concentration in swipe samples was in the range 2.0 to 11 ng and are summarized in Table 3.
Table 2. Concentration of LCMs in dust samples.
Dust sample Compound Concentration (ng/g)
Home environment 1 LCM-4 430 Home environment 2 LCM-3 150 Home environment 4 LCM-3 230 Recycling center LCM-12 63 Phone-repair shop 1 LCM-12 82 Phone-repair shop 2 LCM-12 75
Table 3. Absolute concentration of LCMs in swipe samples.
Swipe sample Compound Absolute concentration (ng)
Phone-repair shop 2, computer
screen LCM-21 2.8
Recycling center, broken screen LCM-4 4.6
Phone shop, tablet screen LCM-10 2.0
The results of the GC analysis imply that the concentration of LCMs observed in dust from home environments was slightly higher than in dust from other sampling locations. However, a larger number of samples would be required to confirm this hypothesis. The reason for this could be that the home environments are smaller in size, which makes it more difficult for the LCMs to spread.
9 Some other factors that could affect the amount was that stores often have professional cleaning, which could mean that these environments have a higher standard when it comes to cleaning, and also might be cleaned more often.Another factor could be that the stores have a lot of activities and movement, which also applies for the recycling center. This could mean that the LCMs scatter and spread more easily. The sampling area at the recycling center was partly outside, which also gives the opportunity for LCMs to be dispersed away by, for example, wind. Notably, 2 out of 3 home environments where LCMs could be detected did not have any big screens (i.e. TV-screens). These environments also do not have an abundance of any other type of technology that could increase the amount of LCMs. The reason for this is unknown. LCMs might not only be present in LCD screens but can also be present in other pieces of technology (9). It can be assumed that LCMs can be spread by degradation or destruction of liquid crystal polymers (LCP) since LCMs are used in the production of LCPs (9). LCPs are used in many different kinds of items, most of them with a need for a strong and durable material (9). Some examples of these are protective gear (i.e. bulletproof vests, military helmets), aircraft interior, sporting gear with compression and much more (10, 11). The destruction and degradation of the material in these items can therefore be a cause for spreading of LCMs. Since LCMs might not only be present in LCD screen, the amount of LCMs found does not have to correlate with the amount of screens present in the environment. Five different LCMs could be found in the studied environments, these being LCM-3, LCM-4, LCM-10, LCM-12 and LCM 21. Out of these, the most commonly found LCM was LCM-12, which could be found in all phone-related stores and at the recycling center. A connection that can be seen is that all dust samples from phone-repair shops and the recycling center, which all have broken screens in their environment, all contained LCM-12. A special characteristic of LCM-12 is that it contains seven fluorine atoms, making it a highly stable composition. This might mean that the substance is persistent, and therefore be the reason that this particular LCM was the most common; or that it is a common LCM in these types of products as a result of its stability. For the molecular formula for all the LCM in this report, see table 1 and their CAS numbers can be found in appendix 3. In the home environments, the most frequently found LCM was LCM-3. The reason for this difficult to know at this point, but one reason could be that LCM-3 might be one of the most economical options to purchase for the manufacturing companies leading to this LCM being more commonly used in LCD-related home electronics.
In this study, only 13 different LCMs were examined. There are at least 362 different known LCMs. This means that other types of LCMs, that were not tested in this study, can be present in our samples and in the environments that were examined.
There is limited data available reporting LCMs in dust and thus selecting an appropriate amount of sample needed for extraction is difficult. The amount of dust extracted in this study was approximately 50-100 mg. However, a larger amount of sample may have yielded a higher detection frequency of LCMs. Furthermore, at some sampling locations, 50 mg of dust could not be collected. Thus, the detection frequency of LCMs should be considered tentative and the lack of detected LCMs in some samples should not be interpreted as the absence of LCMs in the dust at these locations.
The amount of dust collected by swipe sampling is not known and the concentration in the dust can therefore not be calculated. Thus, the results are only qualitative and the absolute concentration was reported; which should not be confused with (or compared to) the concentration in dust reported for the dust samples. In addition, the volume of extract differed significantly between samples. A possible reason for this was that different amounts of isopropanol was added to the Kleenex during swipe sampling. A standardization of the swipe sampling method should be considered to ensure quality in future research.
10 The performance of the extraction method in terms of recovery (%) was low. In addition, for both dust and swipe samples, the extraction volume differed slightly between samples. Since no internal standard was used, the loss of target analytes during extraction as well as differences in extraction efficiency between samples could not be compensated for. Therefore, the results should be considered tentative and comparison between samples should be done with caution. An optimization of the extraction method should be done in order to produce more quantitative data.
LCMs were detected in 6 of the 10 vacuumed samples and in 3 of the 11 swipe samples. All samples positive for LCMs contained a singular LCM-type, except for one swipe sample which contained three types of LCMs. The overall most common LCM found was LCM-12, but the most commonly found LCM in home environments was LCM-3. No LCMs were found in the other samples.
11 7 References
1. Jameco Electronics: Liquid crystals; the story behind the technology.
2. Cotterill, R. The Material World. 2nd edition. Cambridge: Cambridge University press, 2008.
3. Castellano, J. Harrison KJ.The Physics and Chemistry of Liquid Crystal Devices. New York: Springer, 1980.
4. Scitechdaily: Warning: potentially toxic chemicals in nearly half of household dust samples tested. https://scitechdaily.com/warning-potentially-toxic-chemicals-in-nearly-half-of-household-dust-samples-tested/ (Retrieved 2020-05-20.)
5. Su, H. Shi, S. Zhu, M. Crump, D. Letcher, RJ. Giesy, JP. Su, G. Persistent,
bioaccumulative, and toxic properties of liquid crystal monomers and their detection in indoor residential dust. Proceedings Of the National Academy of Science of the United State of America.Vol.116, nr.52 , 2019; 26450-26458. doi :10.1073/pnas.1915322116. 6. Li, J. Su, G. Letcher, RJ. Wanqing, X. Mengyun, Y. Zhang, Y. (April 2018). “Liquid
Crystal Monomers (LCMs): A New Generation of persistent Bioaccumulative and Toxic (PBT) Compounds”. Environ. Sci. Technol. 2018, 52, 5005-5006.
7. The Swedish Chemicals Agency; Highly fluorinated substances (PFOS, PFOA and others); 2019; https://www.kemi.se/en/chemical-substances-and-materials/highly-fluorinated-substances. (2020-05-16)
8. Ran, A. Yadong, L. Xiaojun, N. Honftao, Y. (October 2007). Responses of Antioxidant Enzymes in Catfish Exposed to Liquid Crystals from E-Waste. Int. J. Environ. Res. Public Health. Vol.5, nr.2, 2008: 99-103. doi:10.3390/ijerph5020099.
9. A.A collyer. Liquid crystal polymers: from structures to applications. Essex: Elsevier Science Publication LTD, 1992.
10. Dirk J. Broer, Cees M.W. Bastiaansen, Michael G. Debije, Albertus P.H.J Schenning. Functional Organic Materials Based on Polymerized Liquid‐Crystal Monomers: Supramolecular Hydrogen‐Bonded Systems. Angewandte international edition chemie.Vol. 29, nr. 51 , 2012: 7102-7109. doi: 10.1002/anie.201200883
11. Hübschmann, Hans-Joachim.Handbook of GC-MS: Fundamentals and Applications.Third edition. Weinheim: Wiley - VCH Verlag GmB
13 Appendix 1
Table 4. The mass of the dust samples after sieved with a 500 µm sieve.
Sample number Mass of the sieved dust (g)
1 0.103 2 0.051 3 0.049 4 0.042 5 0.056 6 0.074 7 0.053 8 0.102 9 0.076 10 0.083 QC matrix spike 0.095
14 Appendix 2
Table 5. The final volume of the swipe samples after two extractions
Sample number Volume (mL)
1s 9.5 2s 11.5 3s 7.5 4s 6.0 5s 11.5 6s 9.0 7s 9.0 8s 10.5 9s 5.0 10s 6.5 11s 11.5
15 Appendix 3
Table 6. LCMs in this project, their organic compounds, cas number and formula.
Name Organic compounds Cas number Formula
LCM-3 1-methoxy-4-(4-propylcyclohexyl)cyclohexane 97398-80-6 C16H30O LCM-4 1-(prop-1-enyl)-4-(4-propylcyclohexyl)cyclohexane 279246-65-0 C18H32 LCM-5 1-ethoxy-2,3-difluoro-4-(4-propylcyclohexyl)benzene 174350-05-1 C17H24F2O LCM-6 4-methyl-4'-pentylbiphenyl 64835-63-8 C18H22 LCM-10 1-methyl-4-(4-(4-vinylcyclohexyl)cyclohexyl)benzene 155041-85-3 C21H30 LCM-12 4-[difluoro(3,4,5-trifluorophenoxy)methyl]-3,5-difluoro-4'-propylbipheny 303186-20-1 C22H15F7O LCM-13 1-methyl-4-(4-(4-propylcyclohexyl)cyclohexyl)benzene 84656-75-7 C22H34 LCM-16 1-ethyl-4-(4-(4-propylcyclohexyl)phenyl)benzene 84540-37-4 C23H30 LCM-18 1-ethoxy-2,3-difluoro-4-(4-(4-propylcyclohexyl)cyclohexyl)benzene 123560-48-5 C23H34F2O LCM-19 4''-ethyl-2'-fluoro-4- propyl-1,1':4',1''-terphenyl 95759-44-7 C23H23F LCM-21 4-ethoxy-2,3-difluoro-4'-(4-propylcyclohexyl)biphenyl 189750-98-9 C23H28F2O LCM-31 3,4-difluoro-4'-[4'-propyl-1,1'-bi(cyclohexyl)-4-yl]biphenyl 119990-81-7 C27H34F2 LCM-33 3,4-difluoro-4'-[4'-pentyl-1,1'-bi(cyclohexyl)-4-yl]biphenyl 136609-96-6 C29H38F2
16 Appendix 4
A seven point standard calibration curve within a range of 1.6 to 320 pg/µL was used for quantification. To achieve the desired concentrations, set volumes of the standard mixture were added to each respective vial and filled until 500 µl with hexane, see table 8.
The preparation was done accordingly; before usage, the electronic pipette was rinsed ten times with toluene and ten times with hexane. Hexane was added in all seven vials and secondly the mixture of the standard was added.
In the first vial 480 µL hexane was pipetted with an automatic pipette in order to reach the desired concentration, 320 pg/µL. The following six vials were executed the same way with their respective calculated volume of hexane to achieve each desired concentration. When adding the mixture of standards, the given volume was pipetted with an electronic pipette to the vial containing hexane. In calibration points 1 - 3 the respective volume of standards was pipetted directly from the standard flask to the vials. When preparing calibration point 4 - 7 aliquots from point 3 calibration was taken, with their respective volume and pipetted into the vials containing hexane, see table 9.
Table 7. Calibration points 1-3.
Calibration point Concentration standard
(ng/mL) Standard (µL) Hexane (µL) Concentration (pg/µL)
1 8 20 480 320
2 8 10 490 160
3 8 5 495 80
Table 8. Calibration points 4-7.
Calibration point 3
Calibration point Standard (µL) Hexane (µL) Concentration (pg/µL)
4 100 400 16
5 50 450 8
6 20 480 3.2
7 10 490 1.6
17 Compound Name Area (AU) Concentration (pg/µL) 0.8 1.6 8 80 160 320 640 LCM-3 N.D. N.D. 558000 6860638 12847894 27111732 48682665 LCM-4 N.D. N.D. 250215 3255212 6061845 12709916 22864324 LCM-5 64569 155863 816518 11069201 20264887 43650957 76757986 LCM-6 1087850 2226674 10705301 122356377 245330233 511995621 913499961 LCM-10 18615 39395 196112 2611722 5305675 11676152 21342416 LCM-12 2206281 4544674 21558819 289634635 588593366 1271103421 2277250910 LCM-13 41834 91553 475935 6300378 12446328 27014125 50716395 LCM-16 177158 361884 1711328 21835032 45761773 100871159 197446978 LCM-18 20736 71679 367342 4847440 9983178 22425430 43300549 LCM-19 397520 868552 4331668 54058069 107307917 224463345 444135460 LCM-21 104030 238040 1234090 15520386 33417797 72938384 147109586 LCM-31 14193 44335 359225 5221624 10850333 23439096 52077530 LCM-33 N.D. N.D. 253908 4070994 8868120 18034726 41547895 N.D. Not detected
18 Appendix 6
Figure 1. The plotted concentration of LCM-3 as a
function of the area.
Figure 3. The plotted concentration of LCM-4 as a
function of the area.
Figure 5. The plotted concentration of LCM-5 as a
function of the area.
Figure 2. The plotted concentration of LCM-6 as a
function of the area.
Figure 4. The plotted concentration of LCM-10 as
a function of the area.
Figure 6. The plotted concentration of LCM-12 as
a function of the area.
Figure 7. The plotted concentration of LCM-13 as
19 Figure 8. The plotted concentration of LCM-16 as
a function of the area
Figure 10. The plotted concentration of LCM-18
as a function of the area
Figure 12. The plotted concentration of LCM-19
as a function of the area
Figure 9. The plotted concentration of LCM-21 as
a function of the area
Figure 11. The plotted concentration of LCM-31
as a function of the area
Figure 13. The plotted concentration of LCM-33
20 Appendix 7
Table 10. GC-results for dust samples. Compound Name Area (AU) Sample number 1 2 3 4 5 6 7 8 9 10 LCM-3 N.D N.D 1079740 N.D. 2037771 N.D. N.D. N.D. N.D. N.D. LCM-4 N.D 1749920 N.D. N.D. N.D. N.D. N.D. N.D. N.D. N.D. LCM-5 N.D. N.D. N.D. N.D. N.D. N.D. N.D. N.D. N.D. N.D. LCM-6 N.D. N.D. N.D. N.D. N.D. N.D. N.D. N.D. N.D. N.D. LCM-10 N.D. N.D. N.D. N.D. N.D. N.D. N.D. N.D. N.D. N.D. LCM-12 N.D. N.D. N.D. N.D. N.D. N.D. N.D. 465395 67894 135072 LCM-13 N.D. N.D. N.D. N.D. N.D. N.D. N.D. N.D. N.D. N.D. LCM-16 N.D. N.D. N.D. N.D. N.D. N.D. N.D. N.D. N.D. N.D. LCM-18 N.D. N.D. N.D. N.D. N.D. N.D. N.D. N.D. N.D. N.D. LCM-19 N.D. N.D. N.D. N.D. N.D. N.D. N.D. N.D. N.D. N.D. LCM-21 N.D. N.D. N.D. N.D. N.D. N.D. N.D. N.D. N.D. N.D. LCM-31 N.D. N.D. N.D. N.D. N.D. N.D. N.D. N.D. N.D. N.D. LCM-33 N.D. N.D. N.D. N.D. N.D. N.D. N.D. N.D. N.D. N.D. N.D. Not Detected
spiked swipe sample Field blank, QC matrix spiked Pure hexane, field blank dust sample
LCM-3 1568873 N.D. 1314474 N.D. LCM-4 545432 N.D. 450646 N.D. LCM-5 1552228 N.D. 1457768 N.D. LCM-6 23204619 N.D. 24109422 N.D. LCM-10 125376 N.D. 48499 N.D. LCM-12 58947176 N.D. 55783895 N.D. LCM-13 907242 N.D. 816634 N.D. LCM-16 3372369 N.D. 2991742 N.D. LCM-18 617535 N.D. 548672 N.D. LCM-19 8085920 N.D. 8174962 N.D. LCM-21 2301839 N.D. 2144336 N.D. LCM-31 784557 N.D. 729013 N.D. LCM-33 595078 N.D. 646047 N.D.
22 Table 12. Results of GC for swipe samples
Compound Name Area (AU) Sample number 1s 2s 3s 4s 5s 6s 7s 8s 9s 10s 11s LCM-3 N.D. N.D. N.D. N.D. N.D. N.D. N.D. N.D. N.D. N.D. N.D. LCM-4 N.D. N.D. N.D. 382933 N.D. N.D. N.D. N.D. N.D. N.D. N.D. LCM-5 N.D. N.D. N.D. N.D. N.D. N.D. N.D. N.D. N.D. N.D. N.D. LCM-6 N.D. N.D. N.D. N.D. N.D. N.D. N.D. N.D. N.D. N.D. N.D. LCM-10 N.D. N.D. N.D. 730138 17461 N.D. N.D. N.D. N.D. N.D. N.D. LCM-12 N.D. N.D. N.D. 4034668 N.D. N.D. N.D. N.D. N.D. N.D. N.D. LCM-13 N.D. N.D. N.D. N.D. N.D. N.D. N.D. N.D. N.D. N.D. N.D. LCM-16 N.D. N.D. N.D. N.D. N.D. N.D. N.D. N.D. N.D. N.D. N.D. LCM-18 N.D. N.D. N.D. N.D. N.D. N.D. N.D. N.D. N.D. N.D. N.D. LCM-19 N.D. N.D. N.D. N.D. N.D. N.D. N.D. N.D. N.D. N.D. N.D. LCM-21 10621 N.D. N.D. N.D. N.D. N.D. N.D. N.D. N.D. N.D. N.D. LCM-31 N.D. N.D. N.D. N.D. N.D. N.D. N.D. N.D. N.D. N.D. N.D. LCM-33 N.D. N.D. N.D. N.D. N.D. N.D. N.D. N.D. N.D. N.D. N.D.
23 Appendix 8
Table 13. Instrumental LOD for respective LCMs, defined as the lowest concentration with a signal to noise ratio higher than 3.
Compound LOD (pg/µL) LCM-3 7.9 LCM-4 7.7 LCM-5 0.8 LCM-6 0.8 LCM-10 0.8 LCM-12 3.0 LCM-13 0.7 LCM-16 1.0 LCM-18 0.6 LCM-19 0.9 LCM-21 1.0 LCM-31 0.6 LCM-33 7.3
24 Appendix 9
Table 14. List of samples.
Sample name Sample description
1 Chemistry lab 2 Home environment 1 3 Home environment 2 4 Home environment 3 5 Home environment 4 6 Home environment 5 7 Phone shop 8 Recycling center 9 Phone-repair shop 1 10 Phone-repair shop 2
QC solvent spiked Spiked pure hexane
Field blank swipe Taken in phone shop
QC matrix spiked Spiked dust from chemistry lab
Procedural blank Pure hexane
1s Phone-repair shop 2, computer screen
2s Home environment 5, TV screen
3s Phone shop, TV screen
4s Recycling center, broken screen
5s Phone shop, tablet
6s Home environment 3, TV screen
7s Home environment 4, TV screen
8s Phone-repair shop 1, broken smartphone screen in
9s Phone-repair shop 1, broken smartphone screen in
10s Phone-repair shop 1, computer screen in repair room