Choline Determination
Contents
1. Application Note Number 324 Choline Determination I Introduction Choline concentrations in complex matrices can be measured directly and quickly using the YSI 2700 SELECT Biochemistry Analyzer YSI s unique enzyme technology provides for specific choline measurement Measurements are virtually unaffected by color turbidity density pH or the presence of reducing substances When a sample is injected into the sample chamber the choline diffuses into the membrane containing choline oxidase The choline is immediately oxidized to hydrogen peroxide and betaine The hydrogen peroxide is detected amperometrically at the platinum electrode surface The current flow at the electrode is directly proportional to the hydrogen peroxide concentration and hence to choline concentration Il Materials and Setup A YSI2700 SELECT Biochemistry Analyzer equipped with a 2771 Choline Membrane and 2357 Buffer B Choline standards 175 mg L 450 mg L Place the 175 mg L solution in Cal Station 1 C Connect the 2700 SELECT to a suitable power source D Perform the instrument and membrane check described in the User s Manual Section 3 Volumetric glassware Class A recommended F The following instrument setup is recommended Ill Method A Total choline concentration should not exceed 450 mg L as determined on Part D below otherwise the sample will require further dilution Use volumetric glassware for all dilutions D2. ilute with either water or 2357 buffer B Calibrate the 2700 SELECT with a 175 mg L Calibration Standard C Check the linearity of the membrane at least once a day by injection of a choline linearity check solution 450 mg L Refer to the User s Manual Section 3 for specifications D Assay the sample by aspiration into the 2700 SELECT The linear range of the system is 0 to 450 mg L choline If the value reported exceeds this further dilution is required E Calibrate frequently as described in the User s Manual Section 6 IV Calculations To calculate choline multiply the reported value by the appropriate dilution factor Example 5 0 grams of pet food and 100 mL of water were mixed in a blender for 5 minutes The supernatant was analyzed for choline The value reported was 77 0 mg L choline Choline 77 0mg L x 0 100 L 5000 mg 0 0015 g choline g pet food 0 15 w w Sample size Sample Station CalMethod Black Probe Parameters 25 uL 2 One Station Chemistry Choline Unit mg L ppm Calibrator 175 mg L End Point 30 Sec CalStation 1 White Probe Parameters Single Channel 2700 N A Dual channel 2700 None Autocal Parameters Sample Error ON Temperature 1 C Time 15 Min Sample 2 Sam Cal Shift 2 Example Infant formula was aspirated into the 2700 SELECT no dilution The choline content was as follows Sample mg L Choline Infant Formula A 232 Infant Formula B 138 Medical Nutritional For
3. mula A 398 Medical Nutritional Formula B 386 V Ordering Information YSI No 2700 Biochemistry Analyzer 2771 Choline Membrane Kit 2772 Choline Standard Solution 175 mg L 2773 Choline Standard Solution 450 mg L 2357 Buffer Kit 2363 Potassium Ferrocyanide Test Solution 2392 NaCl Solution for membrane installation Note Software version 2 45 or higher is required to run the choline chemistry If you do not have a compatible software version please contact YSI Customer Service YS I incorporated 1725 Brannum Lane PO Box 279 Yellow Springs Ohio 45387 USA 937 767 7241 800 765 4974 A27324B October 00
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