Site inspection and material testing are crucial to the success of construction projects. This is ensured by passing the resources used at the construction site, such as concrete, soil, and structural steel, through a series of qualitative and quantitative assessments. This article provides an overview of the application of mass spectrometry (MS) for the sample analysis of materials used at construction sites and how it helps identify issues related to the quality of the construction material, highlights future risks, classifies a building site, and consequently assists with engineering decisions.
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Why is MS a Powerful Analytical Tool?
MS is an analytical technique that measures the mass-to-charge (m/z) ratio of one or more molecules in a sample. This analytical technique helps to calculate the exact molecular weight of the sample components. Samples injected into the mass spectrometer were ionized, fragmented, and detected based on their signal intensities and molecular masses.
While mass spectrometry provides information only on the m/z ratio, its combination with other analytical tools such as liquid/gas chromatography or matrix-assisted laser desorption/ionization (MALDI) coupled with a time-of-flight detector (MALDI-TOF) not only provides more detailed information on the composition of the sample but also aids in the separation of the components.
MS - Instrumentation and Working Principle
An MS instrument is composed of three components: an ionization source, a mass analyzer, and an ion detection system. The sample molecules are initially converted into gas-phase ions to enable their movement and manipulation by external magnetic and electric fields.
This process generates positively or negatively charged ions, which are later sorted and separated based on their m/z ratios using a mass analyzer. Based on operational requirements, such as resolution of separation and speed of operation, there are a number of commercially available mass analyzers.
The separated ions are measured by the ion detection system and sent to the data system, where the information on the m/z ratios of the sample components and their relative abundance are stored. Thus, a mass spectrum consists of a graph with the m/z ratios of the ions plotted against their intensities.
Types of MS for Testing Site Sample
Gas Chromatography (GC)–MS: GC-MS is an analytical technique used to identify and separate complex chemical mixtures. Compounds analyzed using GC-MS should be sufficiently volatile and thermally stable. The samples should be then tested in organic solutions. Hence, materials are initially solvent-extracted by subjecting the samples to various 'wet chemical' techniques before GC-MS analysis.
Liquid Chromatography (LC)-MS: LC-MS is a modern analytical technique used to identify, detect, and separate target analytes. LC-MS is a highly selective, sensitive, and accurate method used to detect analytes in soil samples, even in small quantities, such as pesticides and herbicides.
Inductively Coupled Plasma (ICP)-MS: This analytical technique is used to identify nonmetals and metals, even in trace amounts. The plasma used in ICP-MS generates ions that are analyzed by mass spectrometry. This analytical technique is widely used in environmental monitoring.
Application of Mass Spectrometry in Site Sample Testing
Owing to its complex instrumentation, mass spectroscopy is not used directly at construction sites. However, this analytical technique is a promising tool for assessing environmental quality and identifying contaminants that affect the safety of a building site. This spectroscopy technique helps in the detection of various substances, a few of which are listed below.
Heavy Metals: Construction sites may contain heavy metal contaminants such as arsenic, mercury, and lead. These metals have a severe impact on the environment, such as water resources, leading to their bioaccumulation in fish tissues. ICP-MS facilitates both qualitative and quantitative analyses of heavy metals in samples from construction sites at concentrations as low as 1 ppm (one part per quadrillion). Here, argon gas is converted to its plasma state and used to ionize the sample material.
Volatile Organic Compounds (VOCs): Materials used in paints and architectural coatings contain VOCs such as dichloromethane, acetone, methyl acetate, dimethyl carbonate, tertiary butyl acetate, chlorobenzotrifluoride (4-CBTF), and propylene carbonate, which severely impact the environment. GC-MS) is a commonly used analytical technique for estimating the VOCs present in such materials. Additionally, headspace or thermal desorption GC-MS is used to test VOCs in paints and coatings.
Pesticides and Herbicides: Construction sites adjacent to agricultural fields may contain agricultural waste materials, including pesticides and herbicides. The presence of these materials in soil may promote biomagnification. Therefore, if a construction site is adjacent to agricultural land, testing for pesticides and herbicide residues is imperative. In this regard, previous reports have mentioned GC-MS and LC-MS as the gold-standard analytical techniques for quick, easy, rugged, effective, and safe quantitative and qualitative analyses of pesticides and herbicides.
Petroleum Hydrocarbons: Petroleum hydrocarbons affect soil health. The presence of hydrocarbon contaminants in soil leads to delays in construction projects. Sites near mining areas may cause oil spills or fuel leakage, thereby increasing the hydrocarbon residue in the soil. MS is a simple and powerful method for analyzing hydrocarbon compounds and provides information regarding complex petroleum fractions. Although the all-glass heated inlet system (AGHIS) is the conventional method for introducing samples into MS, it was later replaced by GC.
Recent Studies
An article published in Science of The Total Environment analyzed raw influent, effluent, and reference water samples from three wastewater treatment plants (WWTPs) in Australia to evaluate the levels of plastic. Sample analysis using pyrolysis coupled with GC-MS revealed that the total plastic content in the WWTPs was between 840 and 3116 μg/L. Thus, this study proposed GC-MS as a promising tool to investigate the mass concentrations of plastic particles larger than 1 μm in wastewater.
Wood is a commonly used material at any construction site, and its quality mainly constitutes the success of a construction project. An article published in the Journal of Wood Science reported the analysis of two tree species, Phoebe zhennan and Phoebe bournei, for wood quality. Here, solid-phase microextraction (SPME) was used for sample preparation, and GC-MS was used to analyze volatile compounds. The overall findings revealed the presence of 40 volatiles in Phoebe zhennan and 34 substances in Phoebe bournei.
Conclusion
Overall, MS and its integration with other analytical techniques, such as LC-MS and GC-MS, helps in the identification, qualification, and separation of components and contaminants in a sample. Using such robust techniques to analyze samples at construction sites ensures the success of construction projects.
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References and Further Reading
Brinco, J., Guedes, P., da Silva, M. G., Mateus, E. P., Ribeiro, A. B. (2023). Analysis of pesticide residues in soil: A review and comparison of methodologies. Microchemical Journal, 109465. https://doi.org/10.1016/j.microc.2023.109465
What is Mass Spectrometry? Accessed on November 28, 2023 at https://www.broadinstitute.org/technology-areas/what-mass-spectrometry
Environmental Mass Spectrometry: The Intersection Between Science and Sustainability. Accessed on November 28, 2023 at https://www.azooptics.com/Article.aspx?ArticleID=2444
Okoffo, E. D., Rauert, C., Thomas, K. V. (2023). Mass quantification of microplastic at wastewater treatment plants by pyrolysis-gas chromatography–mass spectrometry. Science of The Total Environment, 856, 159251. https://doi.org/10.1016/j.scitotenv.2022.159251
Chen, Z., Xue, X., Cheng, R., Wu, H., Gao, H., Gao, Z. (2023). Geographical origin classification of Phoebe zhennan and Phoebe bournei by solid phase microextraction and gas chromatography-mass spectrometry. Journal of Wood Science, 69(1), 1-10. https://doi.org/10.1186/s10086-023-02095-0
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