102
8.2.1 Choline
This is a direct reading of Choline in solution at the enzyme sensor. The enzyme Choline Oxidase is immobilized in the
enzyme membrane.
Choline + 2O
2
Chol Oxidase
2H
2
O
2
+ Betaine
Color
Orange
Range
5–450 mg/L
Point
175 mg/L
Point
450 mg/L
Precision
(CV,n=10)
whichever is
greater
Linearity
±2%
(5 to Cal Point)
±5%
(Cal Point to Range
Max)
Life
7 days
Note: See Appendix B – Concentration
Unit Conversion if concentration unit
conversion is required.
• If sample dilution is required, use reagent water or 2357
Buffer.
• Although the YSI 2772 Choline calibrator solution is prepared
using choline bitartrate, the concentration is expressed as
mg/L of choline cation. If you prefer to express the sample as
a salt of choline, you must enter an “adjusted” calibration value
when configuring your instrument measurement parameters.
For example, to express results as a choline hydroxide value,
program the calibrator value as 204 mg/L when using the YSI
2772 Choline Standard calibrator solution. Your results will now
reflect the concentration of choline hydroxide in the sample.
Assumptions and calculations are as follows:
choline hydroxide FW = 121.2
free choline FW = 104.2
(121.1 ÷ 104.2) x 175 mg/L = 203.55 = 204 mg/L (rounded up)
Equivalent values for other choline salts may be calculated in
a similar manner.
Potential Interferences.
Tests with equimolar concentrations of various vitamins, and
other ingredients of nutritionals, showed little or no
interference. On a scale where Choline = 100%, those
substances that produced more than 0.5% response were
Riboflavin (1.1%), Pyridoxine (1.5%), Ascorbic Acid (0.8%),
and Thiamine (1.3%). Vanillin, an artificial flavor ingredient,
may produce interference levels exceeding 10% (mole/mole),
and should be tested separately for your individual
formulations if known to be present.
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