Here's one last example. Many laboratories routinely analyze water samples for a whole array of ionic
constituents. It is inherent within any type of measurement that a certain amount of uncertainty will be
introduced. All that can ever be done is to try to minimize the uncertainty -- you can never eliminate it.
Many questions come up in this type of work. For one, is the sample well characterized (i.e., did you
measure all the important anions and cations)? Second, if you are sure that the
system is well characterized, how can you check to see that your analytical
error is within reason? Finally, are organic solutes present in your sample?
One of the first checks that researchers perform on a sample is for ion balance.
This is basically just an accounting of all the positive (cationic) and negative
(anionic) charges in the system. In the actual system, the positive and negative
charges will always balance each other out. This is the principle of
electroneutrality. But in measured samples the introduction of analytical error
will make this hard to observe. Usually a charge discrepancy that less than 10%
of the ionic strength of the solution is considered good.
Here's the problem: One can't just calculate charge discrepancy by adding up all the total metal
concentrations and subtracting the total ligand concentrations. Remember the system described above
includes metal complexes of all types. Each complex contributes its unique charge to the system. So this
is another example where knowledge of chemical equilibrium would be useful. If you know the
concentration of each dissolved complex, you can calculate the charge discrepancy fairly easily.
Not only can the charge discrepancy function as a screening criteria for chemical samples, but it can help
flag when to include additional ions in a suite of analyses or to help identify the presence of organic ion in
waters.
Here's one last example. Many laboratories routinely analyze water samples
for a whole array of ionic constituents. It is inherent within any type of
measurement that a certain amount of uncertainty will be introduced. All
that can ever be done is to try to minimize the uncertainty -- you can never
eliminate it. Many questions come up in this type of work. For one, is the
sample well characterized (i.e., did you measure all the important anions
and cations)? Second, if you are sure that the system is well characterized, how can you check to see
that your analytical error is within reason? Finally, are organic solutes present in your sample?
One of the first checks that researchers perform on a sample is for ion balance. This is basically just an
accounting of all the positive (cationic) and negative (anionic) charges in the system. In the actual system,
the positive and negative charges will always balance each other out. This is the principle of
electroneutrality. But in measured samples the introduction of analytical error will make this hard to
observe. Usually a charge discrepancy that less than 10% of the ionic strength of the solution is
considered good.
Here's the problem: One can't just calculate charge discrepancy by adding up all the total metal
concentrations and subtracting the total ligand concentrations. Remember the system described above
includes metal complexes of all types. Each complex contributes its unique charge to the system. So this
is another example where knowledge of chemical equilibrium would be useful. If you know the
concentration of each dissolved complex, you can calculate the charge discrepancy fairly easily.
Not only can the charge discrepancy function as a screening criteria for chemical samples, but it can help
flag when to include additional ions in a suite of analyses or to help identify the presence of organic ion in
waters.
Here's one last example. Many laboratories routinely analyze water samples
for a whole array of ionic constituents. It is inherent within any type of
measurement that a certain amount of uncertainty will be introduced. All
that can ever be done is to try to minimize the uncertainty -- you can never
eliminate it. Many questions come up in this type of work. For one, is the
sample well characterized (i.e., did you measure all the important anions
and cations)? Second, if you are sure that the system is well characterized, how can you check to see
that your analytical error is within reason? Finally, are organic solutes present in your sample?
One of the first checks that researchers perform on a sample is for ion balance. This is basically just an
accounting of all the positive (cationic) and negative (anionic) charges in the system. In the actual system,
the positive and negative charges will always balance each other out. This is the principle of
electroneutrality. But in measured samples the introduction of analytical error will make this hard to
observe. Usually a charge discrepancy that less than 10% of the ionic strength of the solution is
considered good.
Here's the problem: One can't just calculate charge discrepancy by adding up all the total metal
concentrations and subtracting the total ligand concentrations. Remember the system described above
includes metal complexes of all types. Each complex contributes its unique charge to the system. So this
is another example where knowledge of chemical equilibrium would be useful. If you know the
concentration of each dissolved complex, you can calculate the charge discrepancy fairly easily.
Not only can the charge discrepancy function as a screening criteria for chemical samples, but it can help
flag when to include additional ions in a suite of analyses or to help identify the presence of organic ion in
waters.
Here's one last example. Many laboratories routinely analyze water samples
for a whole array of ionic constituents. It is inherent within any type of
measurement that a certain amount of uncertainty will be introduced. All
that can ever be done is to try to minimize the uncertainty -- you can never
eliminate it. Many questions come up in this type of work. For one, is the
sample well characterized (i.e., did you measure all the important anions
and cations)? Second, if you are sure that the system is well characterized, how can you check to see
that your analytical error is within reason? Finally, are organic solutes present in your sample?
One of the first checks that researchers perform on a sample is for ion balance. This is basically just an
accounting of all the positive (cationic) and negative (anionic) charges in the system. In the actual system,
the positive and negative charges will always balance each other out. This is the principle of
electroneutrality. But in measured samples the introduction of analytical error will make this hard to
observe. Usually a charge discrepancy that less than 10% of the ionic strength of the solution is
considered good.
Here's the problem: One can't just calculate charge discrepancy by adding up all the total metal
concentrations and subtracting the total ligand concentrations. Remember the system described above
includes metal complexes of all types. Each complex contributes its unique charge to the system. So this
is another example where knowledge of chemical equilibrium would be useful. If you know the
concentration of each dissolved complex, you can calculate the charge discrepancy fairly easily.
Not only can the charge discrepancy function as a screening criteria for chemical samples, but it can help
flag when to include additional ions in a suite of analyses or to help identify the presence of organic ion in
waters.
Here's one last example. Many laboratories routinely analyze water samples for a whole array of ionic
constituents. It is inherent within any type of measurement that a certain amount of uncertainty will be
introduced. All that can ever be done is to try to minimize the uncertainty -- you
can never eliminate it. Many questions come up in this type of work. For one, is
the sample well characterized (i.e., did you measure all the important anions and
cations)? Second, if you are sure that the system is well characterized, how can
you check to see that your analytical error is within reason? Finally, are organic
solutes present in your sample?
One of the first checks that researchers perform on a sample is for ion balance.
This is basically just an accounting of all the positive (cationic) and negative
(anionic) charges in the system. In the actual system, the positive and negative
charges will always balance each other out. This is the principle of electroneutrality. But in measured
samples the introduction of analytical error will make this hard to observe. Usually a charge discrepancy
that less than 10% of the ionic strength of the solution is considered good.
Here's the problem: One can't just calculate charge discrepancy by adding up all the total metal
concentrations and subtracting the total ligand concentrations. Remember the system described above
includes metal complexes of all types. Each complex contributes its unique charge to the system. So this
is another example where knowledge of chemical equilibrium would be useful. If you know the
concentration of each dissolved complex, you can calculate the charge discrepancy fairly easily.
Not only can the charge discrepancy function as a screening criteria for chemical samples, but it can help
flag when to include additional ions in a suite of analyses or to help identify the presence of organic ion in
waters.
Here's one last example. Many laboratories routinely analyze water samples for a whole array of ionic
constituents. It is inherent within any type of measurement that a certain amount of uncertainty will be
introduced. All that can ever be done is to try to minimize the uncertainty --
you can never eliminate it. Many questions come up in this type of work. For
one, is the sample well characterized (i.e., did you measure all the important
anions and cations)? Second, if you are sure that the system is well
characterized, how can you check to see that your analytical error is within
reason? Finally, are organic solutes present in your sample?
One of the first checks that researchers perform on a sample is for ion
balance. This is basically just an accounting of all the positive (cationic) and
negative (anionic) charges in the system. In the actual system, the positive
and negative charges will always balance each other out. This is the principle of
electroneutrality. But in measured samples the introduction of analytical error will make this hard to
observe. Usually a charge discrepancy that less than 10% of the ionic strength of the solution is
considered good.
Here's the problem: One can't just calculate charge discrepancy by adding up all the total metal
concentrations and subtracting the total ligand concentrations. Remember the system described above
includes metal complexes of all types. Each complex contributes its unique charge to the system. So this
is another example where knowledge of chemical equilibrium would be useful. If you know the
concentration of each dissolved complex, you can calculate the charge discrepancy fairly easily.
Not only can the charge discrepancy function as a screening criteria for chemical samples, but it can help
flag when to include additional ions in a suite of analyses or to help identify the presence of organic ion in
waters.
Analytical Insight
Here's one last example. Many laboratories routinely analyze water samples for a whole array of ionic constituents. It is inherent within any type of measurement that a certain amount of uncertainty will be introduced. All that can ever be done is to try to minimize the uncertainty -- you can never eliminate it. Many questions come up in this type of work. For one, is the sample well characterized (i.e., did you measure all the important anions and cations)? Second, if you are sure that the system is well characterized, how can you check to see that your analytical error is within reason? Finally, are organic solutes present in your sample?

One of the first checks that researchers perform on a sample is for ion balance. This is basically just an accounting of all the positive (cationic) and negative (anionic) charges in the system. In the actual system, the positive and negative charges will always balance each other out. This is the principle of electroneutrality. But in measured samples the introduction of analytical error will make this hard to observe. Usually a charge discrepancy that less than 10% of the ionic strength of the solution is considered good.

Here's the problem: One can't just calculate charge discrepancy by adding up all the total metal concentrations and subtracting the total ligand concentrations. Remember the system described above includes metal complexes of all types. Each complex contributes its unique charge to the system. So this is another example where knowledge of chemical equilibrium would be useful. If you know the concentration of each dissolved complex, you can calculate the charge discrepancy fairly easily.

Not only can the charge discrepancy function as a screening criteria for chemical samples, but it can help flag when to include additional ions in a suite of analyses or to help identify the presence of organic ion in waters.
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