Active
Siemens Critical Care Analysers SOP
Version:
2.00
Author
:
D Harrison
Doc Manager
:
D Harrison
Authorised by
:
Kath Ash
ton
Signature
: .
Ver Date
:
03/08/09
Do not photocopy this document
Page
21
of 24
Last printed:
5 August 2009
( David Harrison )
DMS Ref
:
Document in Microsoft Internet Exp
lorer
Interferences
Benzalkonium Heparin has been shown to interfere with potassium sensor, increasing apparent levels by
>0.15 mmol. It is recommended that the sample be treated as
mixed venous when Benzalkonium Heparin is
used. Some pulmonary artery catheters may also contain the Benzalkonium ion, which interferes with
analysis.
Caution should be exercised when interpreting whole
-
blood potassium assays as haemolysis, which
may fal
sely elevate the potassium level, will not be apparent.
Chloride
Principle of analysis
The chloride sensor is a half
-
cell that forms a complete electrochemical cell when combined with the
external reference sensor. The chloride sensor contains a Silver/
Silver Chloride wire surrounded by an
electrolyte solution with a fixed concentration of chloride ions
A derivitized quarternary ammonium compound immobilised in a polymer matrix, forms the membrane that
separates the sample from the electrolyte solution.
The membrane acts as an ion exchanger that is highly
selective for chloride ions over other ions in the sample.
When sample comes into contact with the membrane the exchange of Cl
-
ions generates a potential, which is
measured by a voltmeter. This reflect
s the Cl
-
concentration when compared to the constant potential
generated by the reference electrode
Reference range
99
-
109 mmol/l (Plasma)
Whole blood slightly lower (Reference range
not established)
Reporting range
: 65
140 mmol/l (4
00 series analysers)
40
160 mmol/l (800 & 1200 series analysers)
Interfering substances
The following substances were found to interfere with the Chloride assay:
-
Substance
Concentration tested
Level of interference
Salicylic acid
50mg/dl
+9
.5 mmol/l
Salicylic acid
20mg/dl
+1.8 mmol/l
Ionised Calcium
Principle of analysis
The calcium sensor is a half
-
cell that forms a complete electrochemical cell when combined with the external
reference sensor. The Ca sensor contains a Silver/Silver C
hloride wire surrounded by an electrolyte
solution with a fixed concentration of calcium ions
An Ionophore immobilised in a PVC matrix forms the membrane that separates the sample from the
electrolyte solution. The ionophore is a compound that is highly s
elective for calcium ions over other ions.
When sample comes into contact with the membrane the exchange of Ca
++
ions generates a potential, which
is measured by a voltmeter. This reflects the Ca
++
concentration when compared to the constant potential
gene
rated by the reference electrode
Reference range
1.15
1.30 mmol/l (Plasma at pH 7.4)
Whole blood slightly lower (Reference range
not established)
