GLOSSARY OF TERMS - LABORATORY QUALITY ASSURANCE (QA) AND
QUALITY CONTROL (QC) SYSTEM
QUALITY CONTROL (QC) SYSTEM
| 1. | Accreditation | Formal recognition of the competence of a body or an organization for a well-defined purpose. It is the procedure by which a laboratory is assessed to perform a specific range of test or measurements |
| 2. | Accuracy | The closeness of agreement between the "true" value and the measured value. The smaller the systematic error of the analysis is, the more accurate is the analytical procedure. It is assessed by means of reference samples and percent recoveries |
| 3. | Audit Sample | Prepared reference sample inserted into the sample processing procedure as close to the beginning as possible. |
| 4. | Background Sample | A sample taken from a location on or proximate to the site of interest and used to document baseline or historical information |
| 5. | Bias | Systematic error, consistent deviation of measured values from the true value. |
| 6. | Calibration | In chemical measurement, Calibration refers to the process by which the response of a measurement system is related to the concentration or the amount analyte of interest |
| 7. | Calibration Laboratory | Laboratory that performs calibration. |
| 8. | Calibration Method | Defined technical procedure for performing a calibration. |
| 9. | Calibration Standards | A series of known standard solutions used by the analyst for calibration of instrument (i.e. preparation of the analytical curve). |
| 10. | Certified Reference Material (CRM) | A certified reference material is a material or substance whose property or properties can be defined so exactly that it may be used for the calibration of measuring instruments, the check of results obtained from measuring, testing and analytical processes, and for the characterization of substance properties. |
| 11. | Chain of Custody (COC) | Documentation of the history of the sample. The components of chain of custody are sample seals; log book, record and sample analysis request sheet and the procedures used for estimation. |
| 12. | Confidence Interval | Set of possible values within which the true value will lie with a specified level of probability. |
| 13. | Confidence Limit | One of the boundary values defining the confidence interval |
| 14. | Contamination | Something inadvertently added to the sample during the sampling or analytical process. |
| 15. | Control | Type of sample against which the results of a procedure are judged. |
| 16. | Conventional true value | Value attributed to a particular quantity and accepted, sometimes by convention, as having an uncertainty appropriate for a given purpose |
| 17. | Data Quality Objectives (DQOs) | Statements on the level of uncertainty that a decision-maker is willing to accept in the results derived from environmental data. |
| 18. | Environmental sample | An environmental sample or field sample is a representative sample of any material (aqueous, no aqueous or multimedia) collected from any source for which determination of composition of contamination is requested or required. |
| 19. | Error | Difference between a measured value and the true value. |
| 20. | Good Laboratory Practice(GLP) | Good laboratory Practice(GLP) is concerned with the organizational process and the conditions under which laboratory studies are planned, monitored, recorded and reported |
| 21. | Gross error | Which makes it necessary to begin a new analysis (Ex. using a wrong reagent, taking a wrong pipette, measuring at a wrong wavelength. instrument breakdown, heavily contaminated glassware etc.). These errors should easily be recognized. |
| 22. | Instrumentation Detection Limit | The concentration equivalent to a signal due to the analyte which is equal to three times the standard deviation of a series of 7 replicate measurements of a reagent blank’s signal at the same wave length |
| 23. | Inter Laboratory Precision | (Reproducibility) Variation associated with two or more laboratories or organizations using the same measurement method. |
| 24. | Inter Laboratory Test | A series of measurements of one or more quantities performed independently by a number of laboratories on samples of a given material (other terms: Round robin test, Collaborative trial, Collaborative reference program, Collaborative analytical study, ring test). |
| 25. | Interference | Compounds whose presence obscures the measurement of the analyte of interest by the introduction of an unrelated analytical signal where the analyte is measured. |
| 26. | Internal Quality Control | Internal quality control encompasses all measures, which are planned, ordered and executed by a laboratory itself. |
| 27. | Intra-laboratory Precision | (Repeatability) Variation associated with a single laboratory or organization. |
| 28. | Limit of detection (LOD) | The LOD of an individual analytical procedure is the lowest analytical amount of an analyte in a sample, which can be detected but not necessarily quantified as an exact value. For many purposes, the LOD is arbitrarily taken to be 3sb or 3 x the standard deviation of the blank value or of background |
| 29. | Limit of determination | The lower level where measurements become arbitrarily meaningful and is defined arbitrarily as LOQ-10sb (10 x the standard deviation of the blank value or of background) At this concentration, the relative confidence in the measured value is 30% at the 95% confidence level. |
| 30. | Limit of Quantitation (LOQ) | The constituent concentration that produces a signal sufficiently greater than it can be detected within specified limits by good laboratories during routine operating conditions. Typically it is the concentration that produces a signal time 10s above the reagent water blank signal. |
| 31. | Matrix | The matrix of a material is the totality of all parts of a material and their chemical and physical properties including mutual influences. |
| 32. | Matrix /Spike Duplicate Analysis | In matrix/spike duplicate analysis, predetermined quantities of stock solutions of certain analytes are added to a sample matrix prior to sample extraction/digestion and analysis. Samples are split into duplicates, spiked and analyzed. Percent recoveries are calculated for each of the analytes detected. The relative percent difference between the samples is calculated and used to assess analytical precision. The concentration of the spike should be at the regulatory standard level or the estimated or actual method quantification limit. When the concentration of the analyte in the sample is greater than 0.1% no spike of the analyte is necessary. |
| 33. | Method Detection Limit (MDL) | The minimum concentration of a substance that can be measured and reported with 99 % confidence that the analyte concentration is greater than zero. The MDL is determined from analysis of a sample in given matrix containing analyte which has processed through the pre-operative procedure |
| 34. | Method Quantification Limit (MQL) | The Method Quantification Limit is the minimum concentration of a substance that can be measured and reported. |
| 35. | Optimum Concentration Range | A range defined by limits expressed in concentration, below which scale must be used and above which curve correction should be considered. This range varies with the sensitivity of the instrument and the operating conditions employed. |
| 36. | Outlier data | The data, which are suspected to be extremely low or high from the expected value or mean. |
| 37. | Precision | The closeness of agreement between the results obtained by applying the experimental procedure several times under prescribed conditions. (The smaller the random part of the experimental errors, which affect the results, the more precise is the procedure). Within run and between day precisions have to be considered. (See repeatability and reproducibility) |
| 38. | Proficiency Testing | Determination of the laboratory calibration or testing performance by means of inter-laboratory comparisons. |
| 39. | Protocol | Thorough written description of the detailed steps and procedures involved in the collection of samples. |
| 40. | Quality Assessment | Procedure for determining the quality of laboratory measurements by use of data from internal and external quality control measures. |
| 41. | Quality assurance | All those planned and systematic actions necessary to provide adequate confidence that a product or a service will satisfy given requirements for quality |
| 42. | Quality Assurance Programme Plan (QAPP) | An orderly assemblage of management policies, objectives, principles and general procedures by which an organization involved in environmental data generation activities outlines how to produce data of known quality. |
| 43. | Quality Assurance Project Plan (QAPP) | An orderly assemblage of detailed procedures designed to produce data of sufficient quality to meet the DQOs for a specific data collection activity. |
| 44. | Quality Characteristic | The characteristics and characteristic values (or expressions) of something (e.g. a method, a piece of equipment, a measurement result etc.) in relation to their suitability to fulfill set requirements. |
| 45. | Quality Control | Set of measures within a sample analysis methodology to assure that the process is in control. |
| 46. | Quality Control Charts | A Quality control chart is a sequential plot of some quality characteristic. It may be a day-by –day measurement of any interest of analyte (e.g. COD or BOD or Nitrate). The Chart consists of central line and two pairs of limit lines, the Upper and Lower Warning Limits (UWL, LWL )and Upper and Lower Control Limits (UCL., LCL) Example : Shewart’s Quality Control Chart |
| 47. | Quality Manual | A document stating the quality policy, quality system and quality practices of an organization. |
| 48. | Quality System | The organizational structure, responsibilities, procedures, processes and resources for implementing quality management. |
| 49. | Random Errors | Random errors are indicated by the scatter of the results of repeated measurements on the aliquot of same sample about the mean value. The sign and magnitude of the error of any particular result varies at random and cannot be known exactly. Random errors arise from uncontrolled variations in the conditions of the analytical system (factors like analyst, equipment, instrument, method, quality of glassware and chemicals, reagents etc.,) during different analysis. |
| 50. | Range | Spread of values calculated by subtracting the lowest value from the highest value |
| 51. | Reagent Blank | A reagent blank is an aliquot of analyte –free water or solvent analysed with the analytical batch. |
| 52. | Reference material | A material or substance one or more of whose property value are sufficiently homogeneous and well established to be used for the calibration of an apparatus, the assessment of a measurement method, or for assigning value to materials |
| 53. | Reference Standard | A standard, generally of the highest meteorological quality available at a given location, from which measurements made at that location, is derived. |
| 54. | Relative Standard Deviation (RSD) | Estimate of the average error in the measurement due to unassignable causes and usually expressed as a percentage of the average sample concentration. |
| 55. | Repeatability | The closeness of agreement between successive results obtained with the same method on identical test material under the same condition. (Same operator, same apparatus, same laboratory and short intervals of time) can also be interpretable as within – run precision. |
| 56. | Replicate Sample | A replicate sample is a sample prepared by dividing a sample into two or more separate aliquots. Duplicate sample is considered to be two replicates. |
| 57. | Reproducibility | The closeness of agreement between individual results obtained with the same method and on identical material but under different test conditions (different operator, different time’s etc.) Can also be interpreted as "Between-run precision". |
| 58. | Sample Holding Time | The storage time allowed between sample collection and sample analysis when the designated preservation and storage techniques are employed. |
| 59. | Sampling | Attempt to choose and extract a representative portion of a physical system from it’s surroundings. |
| 60. | Sensitivity | Sensitivity describes the ability of an experimental method to differentiate between related values (e.g. concentrations). It indicates to which degree value changes depending upon the signal of the measuring system and can be quantified using the slope of the calibration curve. |
| 61. | Standard Curve | A standard curve is a curve, which plots concentrations of known analyte standard versus the instrument response to the analyte. |
| 62. | Standard Deviation | Square root of the variance (statistical analysis). |
| 63. | Standard Methods | A standard method is an acknowledged analytical method according to an international or national standard or guidelines or to a given legal statue. |
| 64. | Standard Operating procedure (SOP) | Standard Operating procedure (SOP) means written procedure, which describes how those routine laboratory operations, are to be performed. |
| 65. | Stratified Random Sampling | Sampling technique in which estimates of strata means are combined to yield estimates of the population mean. |
| 66. | System Blank | (Instrument Blank): Measure of the instrument background or baseline response in the absence of a sample. |
| 67. | Systematic Error | Systematic errors are indicated by a unidirectional tendency of results, which could be greater or smaller than the true value. When systematic error is present, the result are said to be biased (bias = systematic error) Systematic errors in analytical results may occur when: method used is not specific for the analyte; due to presence of some interfering substances; improper performing of the analysis, instability of samples between sample collection and analysis. |
| 68. | Test | A technical operation that consists of the determination of one or more characteristics or performance of a given product, material equipment organism, physical phenomenon, process or service according to a specified procedure. |
| 69. | Test Method | Defined technical procedure for performing a test |
| 70. | Traceability | The property of a result of a measurement whereby it can be related to appropriate standards, generally international or national standards, through an unbroken chain of comparisons. |
| 71. | True value | Real amount or concentration of an analyte in a certain sample. It is an ideal value, which could be arrived at only if all causes of measurement error were eliminated. The amount or concentration given for an analyte in a certified reference material is a good substitute for the true value. |
| 72. | Trueness | The closeness of agreement between the average value obtained from a large series of test results and an accepted reference value |
| 73. | Uncertainty of measurement | Parameter, associated with the result of a measurement, that characterizes the dispersion of the values that could reasonably be attributed to the measurand |
| 74. | Validation | Validation is the total testing procedure if an analytical method is free of random and systematic error, not only within calibration but also and especially frees of interference when analyzing real samples. |
| 75. | Variance | Measure of the variability in a population / set of analytical data. It is the square root of the standard deviation |
Dr. Amar Nath Giri
EHSQ
("Many Species: One Planet ,One Future)
.