106
8.2.5 L-Glutamate (L-Glutamic Acid)
This is a direct reading of L-glutamate in solution at the enzyme sensor. The enzyme L-Glutamate Oxidase is immobilized
in the YSI Glutamate Membrane.
L-Glu O
2
Glut Oxidase
H
2
O
2
+
α
-Ketoglu NH
3
System Buffer
YSI 2357
Calibrator Std
YSI 2755
Linearity Std
YSI 2756
Membrane
YSI 2754
Membrane
Color
Yellow
Detection
Range
15–1460 mg/L
Calibration
Point
731 mg/L
Linearity Check
Point
1462 mg/L
Sample Size
20
µ
L
End Point
30 sec
Precision
(CV,n=10)
2% or 8 mg/L,
whichever is
greater
Linearity
±
2%
(15 to Cal Point)
±
5%
(Cal Point to Range
Max)
Typical Working
Life
7 days
Note: See
Unit Conversion if concentration unit
conversion is required.
Special Considerations:
•
If sample dilution is required, use reagent water.
•
If you want to measure MSG (monosodium glutamate,
monohydrate) and express the results as mmol/L of
MSG, the calibration parameters listed above are all
appropriate. If you want to express results as a w/v
measurement, such as mg/L MSG, then correction for
the sodium and water components is necessary.
To express results as an MSG value, change the glutamate units
to a w/v expression, and enter one of the following: 936 mg/L,
0.936 g/L, or 0.094 %. Use YSI 2755 Calibrator Standard (5.00
mmol/L Glutamate) to calibrate the instrument. Sample results
will then reflect MSG concentration.
Potential Interferences
Tests with equimolar concentrations of other amino acids and
related substances showed little or no interference. On a scale
where Glutamate = 100%, those substances that produced more
than 0.5% response were L-Aspartate (0.7), L-Tyrosine (1.4), L-
Histidine (0.7), and L-Glutamine (1.1). Glutamate cannot be ruled
out as a contaminant in the Glutamine solution.
