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