Determination of anti-oxidative histidine dipeptides in poultry by microchip capillary electrophoresis with contactless conductivity detection.

A home-made microchip electrophoresis (MCE) device was used to quantitate two biologically important histidine dipeptides, carnosine and anserine, using capacitively coupled contactless conductivity detection (C4D), at pH 2.7. The C4D detector exhibited a linear response to both carnosine and anserine in the range of 0-200µM for the individual dipeptides and in the range of 0-100µM for each dipeptide when both were present as a mixture. The limit of detections (LOD) for the dipeptides in the mixture were 0.10µM for carnosine and 0.16µM for anserine. Standard addition was used to detemine the accuracy of the method. For carnosine and anserine the recoveries were in the range of 96.7±4.9-106.0±7.5% and 95.3±4.5-105.0±5.1% in thigh muscle and 97.5±5.1-105.0±7.5% and 95.3±5.4-97.3±5.6% in breast muscle, respectively.

A novel, fast responding, low noise potentiometric sensor containing a carbon-based polymeric membrane for measuring surfactants in industrial and environmental applications.

A new high-sensitivity potentiometric sensor for anionic surfactants was fabricated using the dimethyldioctadecylammonium-tetraphenylborate (DDA-TPB) ion associate as an ionophore that was incorporated into a liquid PVC membrane. Carbon powder was used for immobilization of the ionophore in the membrane, thus significantly reducing its ohmic resistance and reducing its signal drift. The sensor exhibits a sub-Nernstian response for both dodecylbenzenesulfonate (DBS) and dodecyl sulfate (DS) in H2O (55.3 and 58.5mV/decade of activity, respectively) in a range between 3.2×10-7 and 4.6×10-3M for DS and 2.5×10-7 and 1.2×10-3M for DBS. The sensor also exhibited a sub-Nernstian response for DS and DBS in 10mM Na2SO4 (55.4 and 57.7mV/decade of activity, respectively) between 2.5×10-7 and 4.6×10-3M for DS and 1.5×10-7 and 8.8×10-4M for DBS. The detection limits for DS and DBS in H2O were 2.5×10-7 and 2.0×10-7 M and in 10mM Na2SO4 the detection limits were 2.5×10-7 and 1.2×10-7 M, respectively. The response time of the sensor was less than 5s for changes at higher concentration levels (above 1×10-4M) in both water and 10mM Na2SO4. At lower concentrations (below 1×10-5M) the response times were 8 and 6s in water and 10mM Na2SO4, respectively. The signal drift of the sensor was 1.2mV/hour. The new carbon-based sensor exhibited excellent selectivity performance for DS over almost all of the anions commonly present in commercial formulations and it was successfully employed as an end-point detector in potentiometric titrations of anionic surfactants in a pH range from 3 to 12. Three-component mixtures containing sodium alkanesulfonate (C10, C12 and C14) were successfully differentially titrated.