| Capillary electrophoresis (CE), one of the most important separation techniques, has been greatly developed and improved in recent twenty years. The history, current situation and future trend of capillary electrophoresis is reviewed in this thesis. Capillary electrophoresis is becoming increasingly recognized as an important analytical separation technique due to its speed, efficiency, reproducibility, ultra-small sample volume and ease of clearing up the contaminants. Now it is widely applied in analytical chemistry, biological chemistry, environmental chemistry, and so on. In combination with electrochemical detection (ED), it offers high sensitivity and good selectivity for electroactive species. The present dissertation described the studies of capillary electrophoresis with electrochemical detection in the analyses of foods, traditional Chinese medicines and biological samples. The major content is described as follows:1. Determination of sinapic acid, quercetin and protocatechuic acid in allium cepa linn by capillary zone electrophoresis with electrochemical detectionSimultaneous determination of sinapic acid, quercetin and protocatechuic acid in Allium cepa Linn by capillary zone electrophoresis with electrochemical detection was reported. The parameters affecting separation and detection such as detection potential, separation voltage and running buffer acidity were evaluated. Under the optimum conditions, the analytes were baseline separated within 25 min in a borax buffer (pH = 9.0). Good linear relationship was established between peak current and concentration of analytes in the range of 2.0 ×10-7 1.0 ×10-4 g/mL for sinapic acid, 2.0 ×10-7 5.0 ×10-5 g/mL for quercetin, and 5.0 ×10-7 5.0 ×10-5 g/mL for protocatechuic acid. The detection limit (S/N = 3) is 1.5 ×10-7 g/mL, 1.6 ×10-5 g/mL, and 3.6 ×10-5 g/mL respectively for these three analytes. This method has been used for the determination of active ingredients in allium cepa linn with satisfactory results. 2. Determination of active ingredients in hawthorn and hawthorn piece by capillary electrophoresis with electrochemical detectionCapillary zone electrophoresis with electrochemical detection has been used for the separation and determination of (-)-epicatechin, rutin, hyperin, chlorogenic acid and quercetin. Effects of several important factors including running buffer acidity, separation voltage and working electrode potential, and so on, were evaluated to acquire the optimum conditions . The working electrode was a 300 um carbon disc electrode at a working potential of + 0.95 V ( vs. SCE ) . Under the optimum conditions , the analytes can be well separated within 16 min in a 75 cm length fused-silica capillary . The current response was linear over two orders of magnitude with detection limits ( S/N = 3 ) ranging from 6.00 × 10-8 g/ml to 3.75 × 10-7g/ml for all analytes . This method was successfully used in the analysis of hawthorn and hawthorn piece and the assay results were satisfactory .3. Determination of flavonoids in plumula nelumbini by micellar electrokinetic capillary electrophoresis with electrochemical detectionA simple and efficient method based on micellar electrokinetic capillary electrophoresis (MECC) with electrochemical detection, for the determination of catechin, rutin, hyperin and kaempferol in Plumula Nelumbini was described in this work. Under the optimum conditions, all analytes were well separated within 20 min at the separation voltage of 16 kV in a 60 mmol/L borate running buffer (pH 8.0) containing 20 mmol/L sodium dodecyl sulfate (SDS). The current response was linear over two orders of magnitude with detection limits (S/N = 3) ranging from 6.90 × 10-8 g/mL to 1.30 × 10-7 g/mL for all analytes. This work provides a useful method for the analysis of Plumula Nelumbini.4. Determination of active ingredients in persimmon leaf by capillary electrophoresis with electrochemical detectionCapillary zone electrophoresis with electrochemical detection has been used for the separation and determination of rutin, Vc, hyperin, syringic acid, salicylic acid and quercetin. Effects of several important factors including running buffer acidity, separation voltage and working electrode potential, and so on, were evaluated to acquire the optimum conditions . The working electrode was a 300 um carbon disc electrode at a working potential of + 0.9 V ( vs. SCE ) . Under the optimum conditions , the analytes can be well separated within 20 min in a 75 cm length fused-silica capillary . The current response was linear over three orders of magnitude except that of Vc. The lowest detection limits ( S/N = 3 ) reached 2.50 × 10-8 g/ml. This method was successfully used in the analysis of Persimmon Leaf and the assay results were satisfactory.5. Determination of active ingredients in saururus chinensis by capillary electrophoresis with electrochemical detectionCapillary zone electrophoresis with electrochemical detection has been used for the separation and determination of rutin , hyperin , quercetin , corilagin and gallic acid . Effects of several important factors including running buffer acidity , separation voltage and working potential , and so on , were evaluated to acquire the optimum conditions . The working electrode was a 300 um carbon disc electrode at a working potential of + 0.95 V ( vs. saturated calomel electrode ) . Under the optimum conditions , the analytes can be well separated within 20 min in a 75 cm length fused-silica capillary . The current response was linear over two orders of magnitude with detection limits ( S/N = 3 ) ranging from 3.05 × 10-8g/ml to 9.75 × 10-8g/ml for all analytes . This method was successfully used in the analysis of Saururus Chinensis and the assay results were satisfactory .6. Determination of active ingredients in mutouhui by capillary electrophoresis with electrochemical detectionCapillary zone electrophoresis with electrochemical detection has been used for the separation and determination of scopoletin, hyperin, cholorigic acid and quercetin. Effects of several important factors including running buffer acidity, separation voltage and working electrode potential, and so on, were evaluated to acquire the optimum conditions . The working electrode was a 300 um carbon disc electrode at a working potential of + 0.95 V ( vs. SCE ) . Under the optimum conditions , the analytes can be well separated within 20 min in a 75 cm length fused-silica capillary . The current response was linear over two orders of magnitude with detection limits ( S/N = 3 ) ranging from 2.70 × 10-8 g/ml to 1.30 × 10-7g/ml for all analytes . This method was successfully used in the analysis of Mutouhui and the assay results were satisfactory .7. Method development for fast determination of β-agonists in pig urine by small-size capillary electrophoresis with electrochemical detectionFast separation capability of a novel small-size capillary electrophoresis with electrochemical detection was demonstrated by determining clenbuterol hydrochloride, ractopamine and salbutamol in pig urine. Effects of several important factors including running buffer acidity, separation voltage and working electrode potential, and so on, were evaluated to acquire the optimum conditions. The working electrode was a carbon disc electrode at a working potential of + 0.95 V ( vs. Ag/AgCl). Under the optimum conditions , the analytes can be well separated within 7 min in a 14.5 cm length fused-silica capillary . The current response was linear over two orders of magnitude with detection limits ( S/N = 3 ) ranging from 1.20 × 10-7 g/ml to 2.06 × 10-7g/ml for these analytes . This method was successfully used in the analysis of pig urine and the assay results were satisfactory .
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