How close the results are to some standard, true, or known value. A highly accurate measuring device will provide measurements very close to the standard, true, or known value. Term can apply to both the measurement and the measuring instrument. See also “Bias.”
Adverse effects that result from exposure(s) to a substance within a short time (usually less than 24 hours). The adverse effects should occur within 14 days of the administration of the substance. A subgroup under the Toxicity methods category in NEMI.
The name assigned to a substance, chemical constituent, or feature that is subject to an analytical procedure. For example, in an immunoassay, the analyte may be a hormone or enzyme. Or, in fish community sampling, the analyte may be fish weight measurement.
A unique tracking number for each analyte in the database. For organic chemicals, the code is equivalent to the CAS (Chemical Abstracts Society) Registry Number (RN). For anions, the code is derived from the CAS RN for common salts. For method-defined analytes (analytes that are not chemically distinct, such as "oil and grease" and "chemical oxygen demand"), the codes were taken from EPA's Environmental Monitoring Method Index codes. For some biological analytes, Integrated Taxonomic Information System (IT IS) Taxonomic Serial Numbers (TSN) are used.
The name assigned to a substance or feature that describes it in terms of its molecular composition, taxonomic nomenclature or other characteristic.
The quantity of sample worked up for analysis. Example units are:
(mL), the quantity of sample worked up for analysis, measured in milliliters.
(g), the quantity of sample converted into grams, with the assumed density of 1 for water-based samples.
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, such as by dilution, adjusting sample size, or concentration of extracts.
A procedure to determine the value of a quantity, in other words, to take a measurement. The entity being measured is called the analyte. See also "Bioassay", "Immunoassay", and "Toxicity Assay."
The systematic or persistent distortion of a measured value from its true value (this can occur during sampling design, the sampling process, or laboratory analysis). See also “Accuracy.”
In NEMI, the value "N/A" indicates bias data are not available or could not be found for the method.
A procedure for determining the concentration or biological activity of a substance (e.g. vitamin, hormone, antibiotic) by measuring its effect on an organism or tissue compared to a standard preparation (IUPAC, 2012). Also called biological assay.
Classification for a method in NEMI that involves an experiment on organisms.
Classification for a method in NEMI that involves an experiment on organisms with a toxic substance of biological origin. A subgroup under the Toxicity methods category.
This is a sample container, often filled with distilled water, that travels unopened to the site with the empty sample containers and returns unopened to the laboratory with the samples. This is done to confirm that no contamination has been picked up during the “trip” to and from the sample location. If contamination is found in the trip blank, it means that the samples also may have been contaminated from a source outside the sample area. The trip blank should be non-detect (ND). If it isn’t, your sample results may not be accurate, and a new test should be run (Alaska DEC, 2009). Also called “trip blank.”
A selected sample whose composition is unknown except to the person submitting it; used to test the validity of the measurement process (McGraw-Hill, 2003). Also called “blind sample.”
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").
The quantity of sample that is left over after analysis. Example units are:
(g), the sum of the analytical sample and all chemicals used to treat the analytical sample measured in grams.
A division for a record (or method) within NEMI. For example, a record may be assigned to the Physical, Chemical, Biological, Toxicity Assay, or Statistical categories. A record is further classified by its subcategory. See also “subcategory.” Also called “Method Category.”
Classification for a method or protocol in NEMI dealing with chemistry (e.g., analysis of a substance by test method , good laboratory practices, or guidelines for a sample strategy or how to prepare a sample that will later undergo chemical analysis).
The published literature citation of the method, or volume from which the method comes. Ordering information is also included (if available).
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 paparticular method is given in the DL Notes fields. Reporting units are the units of measurement in the particular method.
The detection level type defines the Detection Level (DL) field. There are many names for DL types, but they fit into one of three main definitions: DL can be (1) the point where a substance will be detected, but not quantitated (e.g., Method Detection Limit; MDL); (2) 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), (3) the lowest level in the calibration range.
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.
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.
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).
Interferences are any items which can lead to erroneously high or low results in the analysis of a sample.
Toxicity assays are designed to work in freshwater, saltwater, or both.
The maximum amount of time a sample may be held after it was collected and before it is analyzed.
The categories of media are Water, Air, Soil/Sediment, Animal Tissue, and Other. The last category (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).
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.).
A brief, descriptive name given to quickly convey fundamentals of a method. This is not the same as the method's "official" name. This name is useful when a method's “official” name is long or not very descriptive. The name typically includes the analyte (e.g., "nitrate") or a class of analytes (eg "nutrients"), the media (e.g., "in water"), and the instrument used in the analysis (e.g., "using colorimetry").
The name, address, and Internet web site of the organization that published the method.
A secondary group division that a NEMI method is assigned to under a method category. This typically refers to the class of analytes that are measured by the method. Subcategories include, but are not limited to, Microbiological, Acute Toxicity, Sampling/Preparation, Statistical Data Analysis, Radiochemical, and Organic. E.g., "organics" is a subcategory of the "chemical" category.”
This field of information is designed to convey the application of the method. The following options are available:
- Sample analysis
- Sample collection
- Statistical technique
- Sample processing/preparation
- Toxicity test procedure
The contaminant was not detected above the method detection limit (MDL).
The title of a method given by the organization or author that published or provides it.
An expression of the reproducibility of measurements. Analytical precision is the measurement of the variability associated with two or more replicate analyses.
"N/A" indicates precision data are not available or could not be found for the method.
A general description or listing of key quality control elements that are in the method (e.g., matrix spikes, reagent blanks).
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.).
A general description of sample handling requirements prior to instrumental analysis (e.g., any preservation requirements, sample container requirements, etc.).
The methods or procedures necessary to prepare a sample for instrumental analysis (e.g., extraction, digestion, filtration, concentration, etc.).
Analyte or analyte classes of interest (e.g., manganese, PAHs) and applicability of methods to different matrices (e.g., water, ground water, TCLP sludges)
The concentration of analyte(s) in sample used to determine precision and accuracy.