Terminologies Flashcards
- the difference between the measured value and the true value.
- if the measurement result is low, the sign is negative; if the measurement result is high, the sign is positive
Absolute error
the closeness of a measured value to the true or accepted value.
Accuracy
a measured fraction of the volume of a liquid sample.
Aliquot
the components of a sample that are determined.
Analytes
instrument for accurately determining mass
Analytical balance
tendency to skew estimates in the direction that favors the anticipated result. Also used to describe the effect of a systematic error on a set of measurements. Also a dc voltage that is applied to a circuit element.
Bias
contains the solvent and all of the reagents in an analysis. Whenever feasible, blanks may also contain added constituents to simulate the sample matrix.
Blank
the empirical determination of the relationship between a measured quantity and a known reference or standard value. used to establish analytical signal versus concentration relationships in a calibration or working curve.
Calibration
transfer of supernatant liquid and washings from a container to a filter without disturbing the precipitated solid in the container
- refers to the process of pouring a liquid gently so as to not disturb the solid in a bottom of container.
Decantation
drying agents
Desiccants
container that provides a dry atmosphere for the cooling and storage of samples, crucibles, and precipitates.
Desiccator
- the difference between a measured value and the “true” or “known” value.
- denotes the estimated uncertainty in a measurement or experiment.
Error
occasional error, neither random nor systematic, that results in the occurrence of a questionable outlier result.
Gross error
known quantity of a species with properties similar to an analyte that is introduced into solutions of the standard and the unknown; the ratio of the signal from the internal standard to the signal from the analyte serves as the basis for the analysis
Internal standard
a listing of hazards and safety precautions for a chemical sold in the US. it also gives first aid procedures and instructions for handling skills.
Material Safety Data Sheet (MSDS)
the collection of all the constituents in the sample.
Matrix
- the most widely used measure of central value.
- also called the arithmetic mean or the average, is obtained by dividing the sum of replicate measurements by the number of measurement in the set.
Mean
pipet calibrated to deliver any desired volume up to its maximum capacity; compare with volumetric pipet
- also known as mohr pipet
Measuring pipet
the middle result when replicate data are arranged in increasing or decreasing order. There are equal numbers of results that are larger and smaller than the median.
Median
the curved surface of a liquid at its interface with the atmosphere.
Meniscus
the standard deviation associated with a measurement method; a factor, with the sampling standard deviation, ss, in determining the overall standard deviation, so, of an analysis.
Method uncertainty
- result that differs significantly from others in the set.
- can have a significant effect on the mean of the set but has no effect on the median.
Outlier
apparent displacement of a liquid level or of a pointer as an observer changes position.
- occurs when an object is viewed from a position that is not at a right angle to the object.
Parallax
describes the reproducibility of measurements—in other words, the closeness of results that have been obtained in exactly the same way.
Precision
stands for parts per million
PPM
highly pure chemical compound that is used to prepare or determine the concentrations of standard solutions for titrimetric.
Primary standard Grade Chemicals
- causes data to be scattered more or less symmetrically around a mean value.
- affect measurement precision.
- resulting from the operation of small uncontrolled variables that are inevitable as measurement systems are extended to and beyond their limits.
Random (or indeterminate) error
it refers to the conform to the minimum standard set forth by the Reagent Chemical Committee of the American Chemical Society and are used whenever possible in an analytical work.
Reagent Grade Chemicals
- the absolute error divided by the true value.
- may be expressed in percent, parts per thousand, or parts per million, depending on the magnitude of the result.
- refers to the relative absolute error
- the error in a measurement divided by the true (or accepted) value for the measurement; often expressed as a percentage
Relative error
process of collecting a small portion of a material whose composition is representative of the bulk of the material from which it was taken.
Sampling
tendency for a reagent or an instrumental method to react with or respond similarly to only a few species
Selectivity
reagents that have been specially purified for a particular end use.
Special-purpose reagent chemicals
methods or reagents that respond or react with one and only one analyte.
Specificity
measure of how closely replicate data cluster around the mean; in a normal distribution, 67% of the data points can be expected to lie within one standard deviation of the mean
Standard deviation
substances sold by the National Institute of Standards and Technology (NIST) and certified to contain specified concentrations of one or more analytes.
Standard reference materials (SRMs) or Certified reference materials (CRM)
- causes the mean of a data set to differ from the accepted value.
- affect the accuracy of results.
- errors that have a known source; they affect measurements in one and only one way and can, in principle, be accounted for.
Systematic (or determinate) error
counterweight used on an analytical balance to compensate for the mass of a container; the act of zeroing a balance.
Tare
- synonym for volumetric pipet
Transfer pipet or transferring pipets
A type of error that arise from non-ideal chemical or physical behavior of analytical
systems.
Method errors
A type of error that result from the carelessness, inattention, or personal limitations
of the experimenter.
Personal errors
A type of error that are independent of the size of the sample being analyzed.
Constant errors
A type of error that decrease or increase in proportion to the size of the sample.
Proportional errors
This analysis reveals the identity of the elements and compounds in a sample.
Qualitative analysis
This analysis indicates the amount of each substance in a sample.
Quantitative analysis
a quantitative technique that measures how much a chemical substance absorbs light.
UV-Vis Spectrochemical Analysis
Component of interest in the sample
Analyte
Collection of all the components in the sample
Matrix
Set of written guidelines for the analysis of a sample specified by an agency
Protocol
Set of written instructions on how to apply a method to a particular sample
Procedure
Process of collecting a small amount of a material whose composition represents the bulk of the materials being sampled
Sampling
The portion of a solution subjected to analysis
Aliquot
A sample that contains all the components of the matrix except the analyte
Blank
An experimental measurement that is proportional to the analyte concentration
Signal
A mathematical technique for fitting an equation, such as that for a straight line, to experimental data
Linear Regression
Process of verifying that a procedure yields acceptable results
Validation
Chemicals that do not have established standards for purity levels or for products with <90% purity.
Technical
High purity chemicals for which no established specifications exist. Chemicals of this grade are often solutions or dilution of ACS Reagent materials. These reagents are suitable for commercial, industrial, and educational application.
Reagent
Chemicals manufactured under current Good Manufacturing Practices and which meet the requirements of the US Pharmacopeia.
USP
Chemicals of this grade meet the specifications of ACS. Analytical reagents are found in most laboratories and are used in a wide variety of analytical techniques for quality control, research and development.
ACS
Chemicals suitable for laboratory and general use. If the reagent also meets the requirements of the American Chemical Society Committee on Analytical Reagents, it will be denoted as an AR (ACS) reagent.
Analytical Reagent (AR)
Analytical reagent of exceptional purity that is specially manufactured for standardizing volumetric solutions and preparing reference standards. The National Institute of Standards and Technology (NIST) is an excellent source for primary standard.
Primary Standard
Chemicals that have been prepared for specific applications. This includes HPLC grade and spectrophotometry grade reagents.
Special Purpose
The difference between the measured value and the true value.
Absolute Error
The study of the composition of materials and the development of tools used to measure properties of substances.
Analytical Chemistry
A systematic error that causes measurements to deviate from the true value in a consistent direction.
Bias
A sample containing all components except the analyte, used to check for contamination or background interference.
Blank
The process of configuring an instrument to provide a result for a sample within an acceptable range.
Calibration
The process of separating mixtures by removing a liquid layer that is free of precipitate.
Decantation
A sealed container used to remove moisture from samples.
Desiccator
The range over which an instrument or method can accurately measure an analyte.
Dynamic Range
A calibration method where known standards are used to construct a calibration curve.
External Standard Method
Large, usually obvious errors typically resulting from human error or instrument failure.
Gross Error
A method of calibration where an internal standard is added to each sample and standard.
Internal Standard Method
The lowest quantity of a substance that can be distinguished from the absence of that substance.
Limit of Detection (LOD)
The smallest concentration of an analyte that can be reliably quantified.
Limit of Quantification (LOQ)
The range over which the response of an instrument is directly proportional to the concentration of analyte.
Linear Range
A statistical method to model the relationship between a dependent variable and one or more independent variables.
Linear Regression
The components of a sample other than the analyte.
Matrix
A pipette calibrated along its length for the measurement of varying volumes of liquid.
Measuring Pipette (Mohr Pipet)
A systematic procedure or technique for achieving a result.
Method
A precision instrument used to measure and transfer very small volumes of liquid.
Micropipette
A document that contains information on the potential hazards of a chemical product and how to work safely with it.
MSDS (Material Safety Data Sheet)
An observation that is significantly different from other data points in a dataset.
Outlier
An apparent shift in the position of an object when viewed from different angles, leading to measurement error.
Parallax
The degree to which repeated measurements under unchanged conditions show the same results.
Precision
High-purity reagents used to prepare primary standards for quantitative analysis.
Primary-Standard Grade Chemicals
A set of established methods for conducting an analysis or experiment.
Procedure
Error that arises from unpredictable variations in the measurement process.
Random Error
A detailed plan of a scientific or medical experiment, treatment, or procedure.
Protocol
Chemicals that meet certain purity standards suitable for analytical applications.
Reagent Grade Chemicals
The absolute error divided by the true value, often expressed as a percentage.
Relative Error
Multiple measurements or observations of the same sample or experiment.
Replicates
The ability of a method to distinguish the analyte from other components in the sample.
Selectivity
The capability of a method to detect small amounts or low concentrations of an analyte.
Sensitivity
A measurable indicator that corresponds to the presence or quantity of an analyte.
Signal
Chemicals designed for specific analytical applications requiring high purity.
Special Purpose Reagent Chemicals
The ability to measure the analyte specifically in the presence of other components.
Specificity
A measure of the amount of variation or dispersion in a set of values.
Standard Deviation
Certified materials with known properties used to calibrate instruments and validate methods.
Standard Reference Materials
Consistent, repeatable error associated with faulty equipment or experimental design.
Systematic Error
The weight of an empty container, subtracted from the gross weight to obtain the net weight of the contents.
Tare
Chemicals of lower purity than reagent grade, often used in industrial applications.
Technical Grade
The specific methods used to conduct a scientific procedure or experiment.
Techniques
Pipettes used to transfer precise volumes of liquid from one container to another.
Transferring Pipette
The process of confirming that a method or instrument produces accurate and reliable results.
Validation
