Electrophoretic Determination of Symmetric and Asymmetric Dimethylarginine in Human Blood Plasma with Whole Capillary Sample Injection

Abstract

Asymmetric and symmetric dimethylarginines are toxic non-coded amino acids. They are formed by post-translational modifications and play multifunctional roles in some human diseases. Their determination in human blood plasma is performed using capillary electrophoresis with contactless conductivity detection. The separations are performed in a capillary covered with covalently bonded PAMAPTAC polymer, which generates anionic electroosmotic flow and the separation takes place in the counter-current regime. The background electrolyte is a 750 mM aqueous solution of acetic acid with pH 2.45. The plasma samples for analysis are treated by the addition of acetonitrile and injected into the capillary in a large volume, reaching 94.5% of the total volume of the capillary, and subsequently subjected to electrophoretic stacking. The attained LODs are 16 nm for ADMA and 22 nM for SDMA. The electrophoretic resolution of both isomers has a value of 5.3. The developed method is sufficiently sensitive for the determination of plasmatic levels of ADMA and SDMA. The determination does not require derivatization and the individual steps in the electrophoretic stacking are fully automated. The determined plasmatic levels for healthy individuals vary in the range 0.36–0.62 µM for ADMA and 0.32–0.70 µM for SDMA.

Monitoring of circulating amino acids in patients with pancreatic cancer and cancer cachexia using capillary electrophoresis and contactless conductivity detection

“…Achieved LODs range from 0.7 to 0.9 μM and LOQs 2.3–2.9 μM, calculated for untreated blood plasma. These LOD values are sufficient for accurate quantification of AAs in clinical trials, but can be reduced if necessary by introducing more extensive stacking of samples using increased sample injection [41].…”

Covalent anionic copolymer coatings with tunable electroosmotic flow for optimization of capillary electrophoretic separations

“…The anionic PAMAMPS coatings are a complement to cationic PAMAPTAC coatings [18], which were so far used in several applications in clinical analysis [11][12][13][14].…”

“…In this paper, variable EOF was evaluated in the separation of drugs in counter‐EOF regime by CE‐UV and CE‐MS. Additional examples of PAMAPTAC coatings may be found in the clinical analysis of metabolites in biological fluids using CE with contactless conductivity detection (C 4 D) [11–14].…”

“…Additional time to achieve better resolution may be beneficial for structurally close analytes such as various isomers with minor difference in their mobilities. As a recent example may serve the separation of cations in a gentle counter-EOF regime in poly(acrylamide-co-(3-acrylamidopropyl) trimethylammonium chloride) (PAMAPTAC) coated capillaries [11][12][13][14]. Another way of separation in the counter-EOF setup is to use a rapid EOF and separate slower ions migrating upstream.…”

“…This coating strategy allows for reversed (i.e., anodic) EOF with a mobility spanning the 0-40 × 10 −9 m 2 V −1 s −1 interval that exhibits low pH dependence in the 2-10 pH range. In this paper, variable EOF was evaluated in the separation of drugs in counter-EOF regime by CE-UV and CE-MS. Additional examples of PAMAPTAC coatings may be found in the clinical analysis of metabolites in biological fluids using CE with contactless conductivity detection (C 4 D) [11][12][13][14].…”