Axial dispersion in a liquid fluidized bed of particles akin to immobilized enzymes

The axial dispersion of a liquid fluidized bed of controlled pore silica (CPS) particles has been determined by the pulse tracer method. The CPS used was the same as for enzyme immobilization, having an average diameter of 0.436 mm and mean pore size of 37.5 nm. The fluidization liquid is α-amylase liquefied manioc starch, 30% w/v, 45°C pH=4.5. Nominal bed porosities tested were 0.7 and 0.8. The results show that the axial dispersion coefficient increases with greater superficial liquid velocities. Various available correlations tested disagree with each other to a large extent and are unable to represent collected experimental data.     

Use of Local Lagrange Interpolation for calculation of retention indices in linear temperature-programmed gas chromatrography

Summary The influence of the isothermal temperature, program rate, initial temperature and flow rate on retention indices was studied. The methods of Kováts, Van Den Dool and Local Lagrange Interpolation are compared. Ten experimental measurements were carried out on a capillary column coated with OV-101 stationary phase.     

以L-天冬氨酸为手性选择剂对手性药物的毛细管电泳拆分

以Ｌ－天冬氨酸为手性选择剂,建立了对１０种手性药物旋光异构体的毛细管电泳快速分离方法,优化了分离条件,并对分离机理作了初步探讨。     

寡糖—8—氨基芘—1,3,6—三磺酸衍生物的毛细管电泳—激光诱？…

利用自组装的毛细管电泳－激光诱导荧光装置,研究了多种寡糖－８－氨基芘－１,３,６－三磺酸（寡糖ＡＰＴＳ）衍生物的分离。考察了电泳介质、浓度及pＨ对寡糖－ＡＰＴＳ 衍生物分离的影响,在酸性和碱性条件下,分别实现了痕量寡糖标准品及葡聚糖水解产物的高效分离。     

Capillary electrochromatography of 1-phenyl-3-methyl-5-pyrazolone derivatives of some mono-and disaccharides

Summary A packing procedure was adopted for capillary electrochromatography (CEC) that produces capillary columns with high separation efficiencies. The columns were fully packed, 50 cm long, with UV detection being performed through the packed section 30 cm from the inlet end. The CEC experiments were run at ambient pressure, with no additional pressure applied to the ends of the column. The stationary phase (octadecyl silica (ODS), 5 μm) promoted a high velocity electroosmotic flow (EOF), enabling rapid and efficient separation of a hydrocarbon test mixture. Some 1-phenyl-3-methyl-5-pyrazolone (PMP) derivatives of mono- and disaccharides were baseline separated, using a 5 mM NaH₂PO₄ in 80% acetonitrile and 20% water (v/v) buffer solution. CEC shows promise for future applications in carbohydrate analysis. Presented at Balaton Symposium on High Performance Separation Methods, Siófok, Hungary, September 1–3, 1999     

Separation of amino acids in plant tissue extracts by capillary zone electrophoresis with indirect UV detection using aromatic carboxylates as background electrolytes

Summary Amino acids in extracts of plant tissue were separated and detected by capillary zone electrophoresis (CZE) with indirect UV detection. Various aromatic carboxylates such as salicylate, benzoate, phthalate and trimellitate were investigated as background electrolytes (BGEs). A BGE of benzoate gave the best resolution and detector response. Amino acids were separated at a highly alkaline pH to charge amino acids negatively. Separation was achieved by the co-electroosmotic flow (Co-EOF) by the addition of the cationic surfactant myristyltrimethyl-ammonium bromide (MTAB) to the electrolyte. The condtions affecting the separation of amino acids, including electrolyte pH, concentrations of both benzoate and MTAB, were investigated and optimised. Separation of a mixture of 17 amino acids at pH 11.20 with indirect UV detection at 225 nm was achieved with a BGE of 10 mM benzoate containing 1.0 mM MTAB at pH of 11.20. Detection limits ranged between 10 and 50 μM. The proposed method was demonstrated by the determination of amino acids in extracts of Eucalypt leaves with direct injection of samples.     

Determination of cobalamins using capillary electrophoresis inductively coupled plasma mass spectrometry

The determination of cobalamins using capillary electrophoresis inductively coupled plasma mass spectrometry (CE-ICP-MS) was investigated. Both capillary zone electrophoresis (CZE) and micellar electrokinetic chromatography (MEKC) modes of operation were studied. The optimal separation of four cobalamin species (cyanocobalamin, hydroxocobalamin, methylcobalamin, and 5′-deoxyadenosylcobalamin) and a potentially harmful corrinoid analogue (cobinamide dicyanide) was obtained using CZE at a pH of 2.5. Both 20 mM phosphate and 20 mM formate buffers were used with success, although the formate buffer provided improved resolution. The CZE-ICP-MS method was used to quantify cyanocobalamin in a vitamin supplement and the analytical results were in good agreement (±5%) with values obtained by ICP-MS for total Co levels. The solution detection limits for cobalamins using CZE-ICP-MS were approximately 50 ng/ml. MEKC was found to be useful for the screening of vitamin preparations because it provided a rapid means of distinguishing cyanocobalamin (the form most commonly used in vitamin preparations) from free cobalt. The separation of free cobalt and cyanocobalamin using MEKC was achieved in less than 10 min.     

Determination of barbituric acid and 2-thiobarbituric acid with end-column electrochemical detection by capillary electrophoresis

Capillary electrophoresis (CE) with end-column electrochemical detection (EC) of barbituric acid (BA) and 2-thiobarbituric acid (TA) has been described. Under optimum condition, BA and TA were separated satisfactorily, and a response of high sensitivity and stability was obtained at a detection potential of 1.25 V versus Ag/AgCl. Optimized end-column detection provides detection limit as low as 0.5 and 0.1 μM for BA and TA, respectively. The calibration graph was linear over three orders of magnitude. The relative standard deviations (n=10) of peak currents and migration times obtained for both BA and TA were 3.4, 3.7, and 1.7, 1.2%, respectively. The proposed method has been applied to analyze water sample with satisfactory results.     

Limonene concentration in lemon (Citrus volkameriana) peel oil as a function of ripeness

The dependence of the limonene content of lemon (Citrus volkameriana) peel oil on the degree of ripeness of the fruit has been studied by using steam distillation and cold pressing to extract the oils from lemon fruit peel at different stages of maturation (green, greenish-yellow, and yellow-orange peel coloration). Samples of essential oils were analyzed by high resolution GC and GC-MS, using tetradecane as internal standard for quantitation. Forty components were detected; thirty eight were positively identified by comparison of their mass spectra (El, 70 eV) and Kováts retention indexes (determined using a non-logarithmic scale on capillary columns coated with both polar (DB-Wax) and non-polar (DB-1) stationary phases) with those of standards and with data reported in the literature. The limonene concentration reached a maximum level of 79.4% when the fruit was in the intermediate maturation stage characterized by greenish-yellow coloration.