Nathalie Hayeck

Chemometric tools to highlight possible migration of compounds from packaging to sunflower oils.

Polyethylene terephthalate (PET) could be considered for the packaging of vegetable oils taking into account the impact of its oxygen permeability on the oxidation of the oil and the migration of volatile organic compounds (VOC) from the polymer matrix. After accelerated aging tests at 40 °C for 10, 20, and 30 days, the headspace of three sunflower oils packed in PET with high density polyethylene caps was carried out using solid phase microextraction. VOCs such as benzene hydrocarbons, ethylbenzene, xylene isomers and diethyl phthalate were identified in vegetable oils by gas chromatography coupled to mass spectrometry. Chemometric tools such as principal components analysis (PCA), independent components analysis (ICA), and a multiblocks analysis, common components and specific weight analysis (CCSWA) applied to analytical data were revealed to be very efficient to discriminate between samples according to oil oxidation products (hexanal, heptanal, 2-pentenal) and to the migration of packaging contaminants (xylene).

Validation of Direct Analysis Real Time source/Time-of-Flight Mass Spectrometry for organophosphate quantitation on wafer surface.

Microelectronic wafers are exposed to airborne molecular contamination (AMC) during the fabrication process of microelectronic components. The organophosphate compounds belonging to the dopant group are one of the most harmful groups. Once adsorbed on the wafer surface these compounds hardly desorb and could diffuse in the bulk of the wafer and invert the wafer from p-type to n-type. The presence of these compounds on wafer surface could have electrical effect on the microelectronic components. For these reasons, it is of importance to control the amount of these compounds on the surface of the wafer. As a result, a fast quantitative and qualitative analytical method, nondestructive for the wafers, is needed to be able to adjust the process and avoid the loss of an important quantity of processed wafers due to the contamination by organophosphate compounds. Here we developed and validated an analytical method for the determination of organic compounds adsorbed on the surface of microelectronic wafers using the Direct Analysis in Real Time-Time of Flight-Mass Spectrometry (DART-ToF-MS) system. Specifically, the developed methodology concerns the organophosphate group.

Development of an analytical methodology for obtaining quantitative mass concentrations from LAAP-ToF-MS measurements

Laser ablation aerosol particle-time of flight mass spectrometer (LAAP-ToF-MS) measures the size number of particles, and chemical composition of individual particles in real-time. LAAP-ToF-MS measurements of chemical composition are difficult to quantify, mostly because the instrument sensitivities to various chemical species in the multicomponent atmospheric aerosol particles are unknown. In this study, we investigate a field-based approach for quantitative measurements of ammonium, nitrate, sulfate, OC, and EC, in size-segregated atmospheric aerosols, by LAAP-ToF-MS using concurrent measurements from high-resolution time-of-flight aerosol mass spectrometer (HR-ToF-AMS), and multi-angle absorption photometer (MAAP). An optical particle counter (OPC) and a high-resolution nanoparticle sizer (scanning mobility particle sizer, or SMPS), were used to measure the particle size distributions of the particles in order to correct the number concentrations. The intercomparison reveals that the degree of agreement of the mass concentrations of each compound measured with LAAP-ToF-MS and HR-ToF-AMS/MAAP increases in the following order NH4+ < SO42- < NO3- < EC < OC < Cl- with r2 values in the range of 0.4-0.95 and linear regression slopes ranging between 0.62 and 1.2. The factors that affect the mass concentrations measured by LAAP-ToF-MS are also discussed in details. Yet, the matrix effect remains one of the strongest limiting factor to achieve an absolute quantification of the aerosol chemical composition. In the future we suggest the development of a methodology based on the calculation of the response factors generated by different types of particles, which could possibly resolve certain difficulties associated with the matrix effect.

In cleanroom, sub-ppb real-time monitoring of volatile organic compounds using proton-transfer reaction/time of flight/mass spectrometry

Refractory compounds such as Trimethylsilanol (TMS) and other organic compounds such as propylene glycol methyl ether acetate (PGMEA) used in the photolithography area of microelectronic cleanrooms have irreversible dramatic impact on optical lenses used on photolithography tools. There is a need for real-time, continuous measurements of organic contaminants in representative cleanroom environment especially in lithography zone. Such information is essential to properly evaluate the impact of organic contamination on optical lenses. In this study, a Proton-Transfer Reaction-Time-of-Flight Mass spectrometer (PTR-TOF-MS) was applied for real-time and continuous monitoring of fugitive organic contamination induced by the fabrication process. Three types of measurements were carried out using the PTR-TOF-MS in order to detect the volatile organic compounds (VOCs) next to the tools in the photolithography area and at the upstream and downstream of chemical filters used to purge the air in the cleanroom environment. A validation and verification of the results obtained with PTR-TOF-MS was performed by comparing these results with those obtained with an off-line technique that is Automated Thermal Desorber – Gas Chromatography – Mass Spectrometry (ATD-GC-MS) used as a reference analytical method. The emerged results from the PTR-TOF-MS analysis exhibited the temporal variation of the VOCs levels in the cleanroom environment during the fabrication process. While comparing the results emerging from the two techniques, a good agreement was found between the results obtained with PTR-TOF-MS and those obtained with ATD-GC-MS for the PGMEA, toluene and xylene. Regarding TMS, a significant difference was observed ascribed to the technical performance of both instruments.

Interfacial photochemistry at the ocean surface is a global source of organic vapors and aerosols

The surface of the oceans acts as a global sink and source for trace gases and aerosol particles. Recent studies suggest that photochemical reactions at this air/water interface produce organic vapors, enhancing particle formation in the atmosphere. However, current model calculations neglect this abiotic source of reactive compounds and account only for biological emissions. Here we show that interfacial photochemistry serves as a major abiotic source of volatile organic compounds (VOCs) on a global scale, capable to compete with emissions from marine biology. Our results indicate global emissions of 23.2–91.9 TgC yr–1 of organic vapors from the oceans into the marine atmosphere and a potential contribution to organic aerosol mass of more than 60% over the remote ocean. Moreover, we provide global distributions of VOC formation potentials, which can be used as simple tools for field studies to estimate photochemical VOC emissions depending on location and season.Volatile organic compounds are photochemically produced in the ocean surface microlayer, but estimates are missing. Here the authors combine experiments and observations to quantify photochemical emissions of volatile organic compounds and show that they are comparable to biological production.

Author Correction: Interfacial photochemistry at the ocean surface is a global source of organic vapors and aerosols

The authors became aware of a mistake in the data displayed in the original version of the paper. Specifically, for the calculation of the total emission estimates (i.e., from an average molecular weight and summed laboratory production values for all VOCs), the authors mistakenly added seasonal estimates to the annual estimates because both values are stored in the same variable of the code. Eventually, this additional sum resulted in a doubling of emission estimates.As a result of this, the following changes have been made to the originally published version of this Article:The fifth sentence of the abstract originally read “Our results indicate global emissions of 46.4–184 Tg C yr–1 of organic vapors from the oceans into the marine atmosphere and a potential contribution to organic aerosol mass of more than 60% over the remote ocean.” In the corrected version “46.4–184 Tg C yr–1” is replaced by “23.2–91.9 Tg C yr-1”The seventh sentence of the second paragraph of the Introduction originally read “We infer global emissions of 65.0–257 Tg yr–1 (46.4–184 Tg C yr–1) of organic vapors from the oceans into the marine atmosphere.” In the corrected version, “65.0–257 Tg yr–1 (46.4–184 Tg C yr–1)” is replaced by “32.5–129 Tg C yr−1 (23.2–91.9 Tg C yr-1)”.The last sentence of the first paragraph of the Results subheading “Marine isoprene emissions from interfacial photochemistry” originally read “In the same way, we infer total emissions of organic vapors from abiotic interfacial photochemistry in the range of 65.0–257 Tg yr–1 (46.4–184 Tg C yr–1), hence, contributing significantly to marine VOC emissions.” In the corrected version, “65.0–257 Tg yr–1 (46.4–184 Tg C yr–1)” is replaced by “32.5–129 Tg C yr−1 (23.2–91.9 Tg C yr−1)”.This has been corrected in both the PDF and the HTML versions of the Article. While the new estimates are lower than previously reported this error does not affect the original discussion or conclusions of the Article. The authors apologize for the confusion caused by this mistake.

Chemical Characteristics of Organic Aerosols in Shanghai: A Study by Ultrahigh‐Performance Liquid Chromatography Coupled With Orbitrap Mass Spectrometry

PM2.5 filter samples were collected in July and October 2014 and January and April 2015 in urban Shanghai, and analyzed using ultra-high-performance liquid chromatography (UHPLC) coupled to Orbitrap mass spectrometry (MS). The measured chromatogram-mass spectra were processed by a non-target screening approach to identify significant signals. In total, 810-1510 chemical formulas of organic compounds in the negative polarity (ESI-) and 860-1790 in the positive polarity (ESI+), respectively, were determined. The chemical characteristics of organic aerosols (OAs) in Shanghai varied among different months and between daytime and nighttime. In the January samples, organics were generally richer in terms of both number and abundance, whereas those in the July samples were far lower. More CHO- (compounds containing only carbon, hydrogen, and oxygen and detected in ESI-) and CHOS- (sulfur-containing organics) were found in the daytime samples, suggesting a photochemical source, whereas CHONS- (nitrogen- and sulfur-containing organics) were more abundant in the nighttime samples, due to nocturnal nitrate radical chemistry. A significant number of mono- and polycyclic aromatic compounds, and nitrogen- and sulfur-containing heterocyclic compounds were detected in all samples, indicating that biomass burning and fossil fuel combustion made important contributions to the OAs in urban Shanghai. Additionally, precursor-product pair analysis indicates that the epoxide pathway is an important formation route for organosulfates observed in Shanghai. Moreover, a similar analysis suggests that 35-57% of nitrogen-containing compounds detected in ESI+ could be formed through reactions between ammonia and carbonyls. Our study presents a comprehensive overview of OAs in urban Shanghai, which helps to understand their characteristics and sources.