EPA Method for a Spectrometer Calibration

Mass spectrometry is an analytic tool that breaks down complex mixtures into molecules to detect and identify minuscule amounts of a chemical compound. Some chemical compounds can cause significant harm in small amounts, and detection is important to characterize the source of pollution and how contaminants can accumulate in the different mediums, soil, groundwater or biota.

Mass Spectrometry Analysis

• Mass spectrometry is an instrument that measures the mass (i.e., weight) of ions that have been converted from molecules through an electric charge. A complex chemical mixture is ionized, and the mass spectrometry measures the ratio between the molecular mass of each ion to the charge of that ion. Once the ratio has been determined, it is cross-referenced to predetermined calibrated measurements that are estimates of the chemical's exact mass, to accurately identify the contaminant. Presentation is made along a spectrum like a graph. The spectrum shows the relative contribution of each compound to the whole mixture, enabling the detection of small amounts of pollutants, like PCBs, that otherwise could not be detected in complex mixtures.

Mass Spectrometry Library

• The National Institute of Standards and Technology has developed a searchable database that contains the spectrum cross-reference for each chemical examined by experienced mass spectrometry professionals, the chemical structure, the spectral display and comparisons of chemicals examined, chemical names and registry numbers for chemicals examined. This library is used in spectrometry analysis after compounds have been ionized and ratios identified. The spectrum displayed is cross-referenced with the library; compounds at minuscule amounts can then be identified.

Benefits of Mass Spectrometry

• Mass spectrometry offers great benefits for pollution control. Contaminants can cause significant harm at very small amounts. Contaminants, like PCBs, can accumulate in fish tissues and then people who eat fish, causing liver damage and endocrine problems. By detecting minute amounts in the environment and biota, standards can be set for safe levels with the understanding of cumulative risks. Fishing advisories and, more importantly, cleanup activities are more accurate.