Environmental analytical chemistry standards

In response to the confusion that existed regarding numerous and conflicting data on detection limits, th lUPAC adopted a model for LOD calculations in thqa 1970s.This standard was reaffirmed by the AC Subcommittee on Environmental Analytical ChemistryS in the early 1980s. The lUPAC/ACS procedure is based on two method characteristics 1) the variation (standard deviation) of multiple blank measurements ands 2) the relationship between the response and the analyte > concentration (at concentrations near the LOD). If is3... 

Synthesis of Polychloroalkanes as Standards for Environmental Analytical Chemistry. .. 42... 

Standardization. Standardization in analytical chemistry, in which standards are used to relate the instrument signal to compound concentration, is the critical function for determining the relative concentrations of species In a wide variety of matrices. Environmental Standard Reference Materials (SRM s) have been developed for various polynuclear aromatic hydrocarbons (PAH s). Information on SRM s can be obtained from the Office of Standard Reference Materials, National Bureau of Standards, Gaithersburg, MD 20899. Summarized in Table VII, these SRM s range from "pure compounds" in aqueous and organic solvents to "natural" matrices such as shale oil and urban and diesel particulate materials. 

Analytical chemistry is a critical component of worker safety, re-entry, and other related studies intended to assess the risk to humans during and subsequent to pesticide applications. The analytical aspect takes on added significance when such studies are intended for submission to the U.S. Environmental Protection Agency and/or other regulatory authorities and are thus required to be conducted according to the Federal Insecticide, Fungicide and Rodenticide Act (FIFRA) Good Laboratory Practice (GLP) Standards, or their equivalent. This presentation will address test, control, and reference substance characterization, use-dilution (tank mix) verification, and specimen (exposure matrix sample) analyses from the perspective of GLP Standards requirements. 

The discipline of analytical chemistry is wide and catholic. It is often difficult for a food chemist to understand the purist concerns of a process control chemist in a pharmaceutical company. The former deals with a complex and variable matrix with many standard analytical methods prescribed by Codex Alimentarius, for which comparability is achieved by strict adherence to the method, and the concept of a true result is of passing interest. Pharmaceuticals, in contrast, have a well-defined matrix, the excipients, and a well-defined analyte (the active) at a concentration that is, in theory, already known. A 100-mg tablet of aspirin, for example, is likely to contain close to 100 mg aspirin, and the analytical methods can be set up on that premise. Some analytical methods are more stable than others, and thus the need to check calibrations is less pressing. Recovery is an issue for many analyses of environmental samples, as is speciation. Any analysis that must... 

Solid-phase extractions can reduce solvent consumption in analytical chemistry. For example, a standard procedure approved by the U.S. Environmental Protection Agency for the analysis of pesticides in wastewater requires 200 mL of dichloromethane for the liquid-liquid extraction of 1 L of water. The same analytes can be isolated by solid-phase extraction on C g-silica disks. The pesticides are recovered from the disks by supercritical fluid extraction with C02 that is finally vented into a small volume of hexane. This one kind of analysis can save 10s kg of CH2C12 per year.24... 

Radionuclide analysis methods are published in analytical chemistry and radiochemistry journals, and in methods manuals issued by nuclear facilities such as government laboratories. For example, the Environmental Measurements Laboratory Procedures manual, HASL-300 (Chieco 1997), is an excellent source. Standard methods for radionuclide analysis (see Section 6.7) are available, and should be used whenever appropriate. If conditions differ from those to which published methods have been applied, radionuclide recovery and decontamination must be tested and additional process steps may have to be inserted. 

Accuracy is a term describing deviation of an observ value (or the mean of observed value) from the "true" or, more realistically, the generally acceptable value. For example, the "true value" of a parameter (e.g., %Ni, %Fe, %S) of a well-defined sample is the mean value obtained by the work of several teams of experienced, competent analytical chemists. The National Institute of Standards and Technology, formerly National Bureau of Standards, make available to the analytical chemistry community a series of carefully prepared materials analyzed by several kinds of established methods, known as Standard Reference Materials, including metals, minerals, and environmental samples. 

C means certified values, A refers to assigned values (not certified), and I corresponds to data given for information. (Adapted from Gills TE (1999) NIST standard reference materials for measurement assurance - practices, issues and perspectives. In Fajgelj A and Parkany M (eds.) The Use of Matrix Reference Materials in Environmental Analytical Processes, Cambridge The Royal Society of Chemistry, pp. 57-64.)... 

As microwave sample preparation has evolved, standard microwave procedures have been developed and approved by numerous standard methods organizations. Table 1 summarizes the different methods approved for either microwave drying or microwave acid dissolution by the Association of Official Analytical Chemistry (AOAC), American Society for Testing and Materials (ASTM), the United States Environmental Protection Agency (US-EPA), Standard Method, and Erench and Chinese national methods. 

When available, standard methods of sampling and analysis should be used. The International Standard Organisation (ISO), the Comite Europeen de Normalisation (CEN) and various national bodies have published several methods for determination of airborne contaminants. Primary sources are the compendia of methods recommended by the regulatory bodies, i.e. the UK, HSE the US National Institute for Occupational Safety and Health (NIOSH) and the Occupational Safety and Health Administration (OSHA). The HSE has published Methods for the Determination of Hazardous Substances (MDHS) for over 70 specific substances (Health and Safety Executive 1981-95). OSHA and NIOSH have published manuals with more than 500 and 100 sampling and analytical methods respectively (National Institute for Occupational Safety and Health 1994 Occupational Safety and Health Administration 1985). Secondary sources are published literature references in, for example. Annals of Occupational Hygiene, the American Industrial Hygiene Association Journal, Applied Occupational and Environmental Hygiene, or Analytical Chemistry. 

This is a very exciting development for the environmental analytical community. In a recent study, a total of 18 elements, including a mixture of transition metals and hydride-forming elements were determined at low-ppb levels in a standard reference seawater sample in less than 10 min. The instrumental setup for this automated direct aspiration, matrix separation, analyte preconcentration, and hydride generation online chemistry system is shown in Figure 17.16. 

Founded in 1944, the National Sanitation Foundation (NSF) develops standards, conducts product testing, and provides certification services in areas related to public health and safety. Technical resources include the operation of physical and performance testing facilities and analytical chemistry and microbiology laboratories. NSF International operates as a not-for-profit nongovernmental organization. NSF develops national standards, provides learning opportunities, and provides third-party conformity assessment services. The foundation known and recognized for its scientific and technical expertise continues to focus on a variety of pertinent issues related to health and environmental sciences. 

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