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issues_with_ion_measurement [22/05/2018 09:35] pieter |
issues_with_ion_measurement [22/05/2018 09:35] (current) pieter |
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Adding ionic strength adjuster (ISA) to samples and standards ensure that they have a similar ionic strength. This is important because the ionic strength of a solution affects the relationship between activity and concentration (i.e. the measured value). By bringing the ionic strength of all samples and standards to a similar level, the effect of variable ionic strengths on the activity (and therefore the concentration) is minimized, thus reducing measurement error. Many electrode slope issues and measurement instabilities are solved when using ISA. | Adding ionic strength adjuster (ISA) to samples and standards ensure that they have a similar ionic strength. This is important because the ionic strength of a solution affects the relationship between activity and concentration (i.e. the measured value). By bringing the ionic strength of all samples and standards to a similar level, the effect of variable ionic strengths on the activity (and therefore the concentration) is minimized, thus reducing measurement error. Many electrode slope issues and measurement instabilities are solved when using ISA. | ||
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+ | =====Temperature===== | ||
+ | There is no temperature compensation foreseen for the ion selective measurements although these are sensitive to temperature changes. A difference of 1°C can cause an error of 2%. It is advised to maintain all solutions, standards and samples, at __the same temperature__ during calibrations and measurements. Repeat the calibrations when the temperature has changed to ensure minimal measurement errors. | ||
=====Interferences===== | =====Interferences===== | ||
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* In many instances interfering ions can be eliminated using chemicals. | * In many instances interfering ions can be eliminated using chemicals. | ||
* You can use incremental techniques, e.g. Known Addition. | * You can use incremental techniques, e.g. Known Addition. | ||
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- | =====Temperature===== | ||
- | There is no temperature compensation foreseen for the ion selective measurements although these are sensitive to temperature changes. A difference of 1°C can cause an error of 2%. It is advised to maintain all solutions, standards and samples, at __the same temperature__ during calibrations and measurements. Repeat the calibrations when the temperature has changed to ensure minimal measurement errors. | ||
====== Report a measurement problem ====== | ====== Report a measurement problem ====== |