National Environmental Methods Index (NEMI)

Fields of Information for methods in the NEMI database * = searchable field
General method information
Method identifier	The identification number assigned by the method publisher (e.g., EPA Method 1631 is known as "1631" in the NEMI database; ASTM Method D2036-98 is known as "D-2036-98", etc.).
Method official name	The title of the method that appears on the method from the organization that published it.
Method descriptive name	A brief descriptive name - useful when a method's official name is long or not very descriptive. Contains either the analyte name or a class of analytes, and the instrument used for analysis.
Method source*	The name, address, and Internet web site of the organization that published the method.
Citation	The published literature citation of the method, or volume from which the method comes. Ordering information is also included (if available).
Subcategory*	Subcategories of analytes for which a method may be listed (e.g., "organics" is a subcategory of the "chemical" category).
Media*	The four categories of media are Water, Air, Soil, and Other. The last catergory (Other) includes methods that are applicable to a unique medium (e.g., Steam), or to a variety of media (e.g., Water and Soil). Method summaries will specify applicable media and matrices (if available).
Brief Method Summary	Method summaries provide general information on methods. This includes: determinative technique employed (e.g., colorimetry) and some summarized procedural information (e.g., "sample is treated with barium chloride to precipitate out barium sulfate, which is determined via colorimetry of turbimetry").
Scope and application	Analyte or analyte classes of interest (e.g., manganese, PAHs) and applicability of methods to different matrices (e.g., water, ground water, TCLP sludges)
Instrumentation	Key or major instrumentation needed to perform an analysis with the specified method. This is a reference to the determinative technique used by the method (e.g., colorimetry, GC-MS).
Detection level type	The DL can be the point where a substance will be detected, but not quantitated (e.g., Method Detection Limit; MDL); the lowest concentration at which the analyte can be accuractely quantitated (e.g., Minimum Level; ML); the lowest level of an analyte that can be determined by an instrument ignoring the possibility of analyte loss/contamination through sample pretreatment procedures (e.g., Instrument Detection Limit; IDL), the lowest level in the calibration range of the method, or the target regulatory level. Many organization will have organization-specific variants on the general classes of DLs described above.
Applicable concentration range	Range of concentrations over which analytes can be measured with typical use of the method. The range can be extended to higher or lower concentrations by using appropriate sample preparative techniques, e.g., dilution, adjusting sample size, concentration of extracts, etc.
Interferences	Interferences are any items which can lead to erroneously high or low results in the analysis of a sample.
Precision descriptor notes	Description of how precision and accuracy data were determined.
Quality Control Requirements	A general description or listing of key quality control elements that are in the method (e.g., matrix spikes, reagent blanks).
Sample handling	A general description of sample handling requirements prior to instrumental analysis (e.g., any preservation requirements, sample container requirements, etc.).
Maximum holding time	The maximum amount of time a sample may be held after it was collected and before it is analyzed.
Sample preparation methods	The methods or procedures necessary to prepare a sample for instrumental analysis (e.g., extraction, digestion, filtration, concentration, etc.).
Relative Cost	Relative cost per procedure of a typical analytical measurement using the specified methods (i.e., the cost of analyzing a single sample). Additional considerations affect total project costs (e.g., labor and equipment/supplies for a typical sample preparation, QA/QC requirements to validate results reported, number of samples being analyzed, etc.).
Link to full method	This is a hyperlink to the home page of the organization where the full method may be obtained. Methods that are public domain, such as those from EPA, USGS, DOE, etc. may be downloaded directly from the NEMI web site.
Analyte-specific information
Analyte*	The name assigned to a substance or feature that describes it in terms of its molecular composition, taxonomic nomenclature or other characteristic.
Analyte code	A unique tracking number for each analyte in the database. For organic chemicals, the ID number is equivalent too to the CASRN. For anions, the ID number is derived from the CASRN for common salts. For method-defined analytes (analytes that are not chemically distinct, such as "oil and grease", and "chemical oxygen demand") ID numbers are taken from EPA's Environmental Monitoring Method Index codes.
Detection level (DL)*	The lowest "measurable" concentration for an analyte by the specified method. The DL for a specific analyte can be influenced by a number of factors, such as the sample matrix used in a DL study or the laboratory's experience with the method. Often a DL will be determined in reagent grade (very pure) water to demonstrate the optimal DL. In many cases, the reported DL will be generated by the method developer, which has considerable experience with the method. Therefore the reported DL may be much lower than that achievable by a laboratory using the method for the first time. Also, a reported DL may reflect single laboratory performance or the pooled performance of multiple laboratories (the latter providing a picture of overall method performance across the laboratory community). When comparing listed DLs it's important to take into consideration the kind of DLs in questions, and the variables (e.g., matrix) that can effect DLs. Available information on how DLs were determined for a particular method is given in the DL Notes fields. Reporting units are the units of measurement in the particular method.
Precision	An expression of the reproducibility of measurements. Analytical precision is the measurement of the variability associated with two or more replicate analyses.
Accuracy	The closeness to a "true" value. The true value is theoretical concentration of an analyte added to the sample (e.g., spiking level). Often, accuracy is expressed as percent recovery of a specified analyte in a specified matrix (e.g., reagent grade water) is used to describe accuracy in published methods.
False positive	The percent of samples analyzed that are reported to contain an analyte, when none of the samples in the set actually contain the analyte. Often, the percent of false positives is determined using blank samples, or samples in which the analyte is below the lowest limit of quantitation, or below the detection limit.
False negative	The percent of samples analyzed that are reported not to contain an analyte, when all of the samples in the set actually contain the analyte. Often, the percent of false negatives is determined using samples in which the analyte is above its specified regulatory contaminant level.
Spiking level	The concentration of analytes in sample used to determine precision and accuracy.
Endpoint	The conditions (physical, chemical or biological) which define when the analysis is completed and the result is obtained. The endpoint can be simply a step in sample preparation that puts the analyte in a state that can be easily detected and enumerated (biological organisms) or quantified (chemicals). In somewhat more complex cases, an endpoint may be the period of elapsed time for a biological analyte to reach a specific developmental stage, or for a chemical analyte to complete a reaction.