Hello! this entry is an addition to explain my previous entry on the DxC analyzer. Some of you may not understand how the analyzers in the lab use e principles to carry out the different kinds of tests. So, I have added in one example of test used by the DxC 800 Beckman Coulter analyzer used in the lab I'm attached to :)
Clinical Chem Lab technique
Name of test: Renal Function Test on DxC 800 analyzer
Principle of test: ISE (Ion Selective Electrode) Method
The DxC 800 analyzer can determine Sodium ion concentration by indirect potentiometry using two glass Sodium electrodes, whereby one of them will be used as a reference electrode. A reference electrode is the electrode with stable and well-known electrode potential. The outer layer of the glass electrode must be hydrated adequately. The sodium concentration is measured using a precise volume of sample that is mixed with a buffered solution. When the sample buffer mixture gets in contact with the electrode, sodium ions in the sample will undergo an ion exchange process with the sodium ions in the hydrated layer of the electrode. Thus, there will be a change in electrode potential which will be referenced with the reference electrode. From here, the concentration of Sodium can be measured.
Normal reference range of test results are:
0 day to 12 years old: 131-144mmol/L
> 12 years old: 135-145 mmol/L
Any results higher or lower than the normal reference ranges indicate abnormalities in patients.
This sodium measurements is used in the diagnosis and treatment of renal failure, hypernatraemia, hyponatraemia as well as other diseases involving electrolyte imbalance.
I hope this helps you guys to understand better! :)
Stella
0701059H
TG01
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8 comments:
Good. You have focused on 1 test to explain the principle.
What are other methods available to determine electrolytes? Why ISE is the preferred choice of methodology as compared to others?
"The glass electrode must be hydrated adequately"
What if, due to some unseen reason (eg. leakage) that the fluid used to hydrate the electrode runs out. Will it affect the results?
What will happen? Has it ever occur before?
Alvin
0703829B
Hi Ms Chew, so far I was only taught about the ISE method which the lab analyzers use to perform certain tests such as renal function tests.
ISE is the preferred choice because of its abilities to measure ions such as sodium, potassium and chloride using the electrode. Only ISE is able to measure the ions whereas the other methods are unlikely able to.And the other methods i'm referring to are enzymatic and Spectrophotometry methods.
Stella
0701059H
Hello Stella,
Can the analyzer determine other ion concentrations other than the sodium ion concentration?
If it is able to, can it detect 2 different ion concentrations simultaneously or must it be done on separate runnings?
Renee
TG02
0703634F
hi alvin!
it will affect the results because the ISE contain a membrane whereby when a sample is brought in contact with the membrane, a membrane potential develops. this membrane potential is compared to the constant potential of the reference electrode. therefore, the electrodes have to be hydrated at all times so the electrolytes can pass through the membrane.
hope i answer ur ques!
:)
stella
0701059H
Hi Renee!
the analyzer can determine other ion concentrations such as potassium and chloride.
and yes, it can detect 2 different ion concentrations simultaneously.
:)
stella
0701059H
Thanks alot Stella!
Renee
TG02
0703634F
There are other available methods to determine ions but they are more troublesome. The other method is flamephotometry. This method is more accurate and more sensitive. ISE is more preferred because it is more convenient in maintenance and incorporation into the analyzer as compare to the flamephotometry method.
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