|
Reagents for the Preparation of Native Samples for Amino Acid
Analysis by Lithium Ion-exchange
Here
you can download this materials in PDF format*
|
|
INTRODUCTION
Native amino acids are those found “free” in samples
such as serum, urine and other physiological fluids, plant
extracts, foods and beverages. Although preparation of these
samples for amino acid analysis is much simpler and less time-consuming
than protein hydrolysis, control of pH and normality, and
removal of soluble protein are critical factors which can
affect the chromatography.
The early-eluting amino acids — taurine, urea, aspartic
acid, threonine, serine, etc. — are particularly sensitive
to pH and normality. Accordingly the samples must be held
to a narrow pH range between 2.1 and 2.5, and the proper lithium
ion concentration to ensure reproducibility in the early part
of the chromatogram. The later-eluting compounds are more
tolerant of initial sample conditions, and their retention
times are not as likely to be affected.
|
 |
SERAPREP and URIPREP replace commonly-used protein precipitation
reagents such as acetonitrile, perchloric acid and picric acid,
and eliminate the need for dialysis, ultrafiltration, and repeated
centrifugation steps, followed by pH adjustment.
SAMPLE PREPARATION USING SERAPREP OR URIPREP
Use SERAPREP for preparing serum and other samples with a high
buffering capacity, e.g. sardine oil. Use URIPREP for preparing
urine and other samples with low buffering capacity, such as fruit
juices, musts and warts. The efficiency of protein precipitation
and the need for post-centrifugation pH adjustment of the sample
determine which reagent is best for your particular sample.
-
In a microcentrifuge tube thoroughly mix equal portions of sample
and SERAPREP or URIPREP.
-
Let stand for 5 minutes. Centrifuge the mixture at 13,000 rpm
for 5 minutes. Check the supernate pH to ensure that the range
is pH 2.3±0.2. Adjust the initial mixing ratio as necessary.
Filter the supernate with a syringe filter (0.2 or 0.45 µm).
The filtrate is ready to be injected into an auto-sampler vial
for amino acid analysis.
-
If further dilution is needed, use Li 220 to adjust the concentration
of analyte.
ORDERING INFORMATION
SERAPREP and URIPREP are trademarks of Pickering
Laboratories, Inc.
^ Back to top |
