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
22
of 24
Last printed:
5 August 2009
( David Harrison )
DMS Ref
:
Document in Microsoft Internet Exp
lorer
Reporting range
: 0.20
5.00 mmol/l (400 series analysers)
0.25
5.00 mmol/l (800 & 120
0 series analysers)
Interfering substances
The following substances were found to interfere with the Calcium assay:
-
Substance
Concentration tested
Level of interference
Salicylic acid
50mg/dl
-
6%
Salicylic acid
30mg/dl
-
3%
APPENDIX D
METABOLITE
S
Principle of analysis
The glucose & lactate sensors are complete electrochemical cells that incorporate amperometric technology to
measure glucose or lactate concentration in samples. The sensors consist of 4 electrodes
The measuring electrode contains platinum and either glucose oxidase or lactate oxidase in a binder, while the
reference electrode is silver/silver chloride. Of the remaining two electrodes one is a platinum conductor that
ensures a constant applied potential, the 4
th
electrode is another measuring electrode without the enzyme. This
determines interfering substances in the sample, subtracting them from the total measurement. A microporous
cover membrane separates the electrodes from the sample.
A constant polarizing voltage is maintained during analysis.
The relevant reactions are shown below:
-
Glucose
Glucose oxidase acts on glucose in the sample to form hydrogen peroxide and gluconic acid.
GOX
C
6
H
12
O
6
+ H
2
O
C
6
H
12
O
7
+ H
2
O
2
W
here GOX is the glucose oxidase
The polarizing voltage causes oxidation of the hydrogen peroxide
H
2
O
2
2H
+
+
O
2
+ 2e
-
The loss of the electrons creates a current flow that is directly proportional to the level of glucose in the sample.
Lactate
Lactat
e oxidase acts on lactate in the sample to form hydrogen peroxide and pyruvic acid.
LOD
C
3
H
6
O
3
+ H
2
O + O
2
C
3
H
4
O
3
+ H
2
O
2
Where LOD is the Lactate oxidase
The polarizing voltage causes oxidation of the hydrogen peroxide
H
2
O
2
2H
+
+
O
2
+ 2e
-
The loss of the electrons creates a current flow that is directly proportional to the level of lactate in the sample.
