ISSN:0935-6304    

DOI:10.1002/jhrc.1240150902

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1992

数据来源: WILEY

摘要:

AbstractA surface modification has been developed which yields fused silica capillaries with switchable electroosmotic flow (anodal/cathodal). The capillary surface is a composite material consisting of unreacted silanol groups, a layer of positively charged quaternary ammonium functions, and a hydrophilic layer of long polyether chains. Because of the presence of positively and negatively charged groups, the net charge of the capillary surface can be varied from positive to negative by changing the pH of the running electrolyte, thus enabling manipulation of the magnitude and direction of the electroosmotic flow. The long polyether chains were effective in shielding biomacromolecules from the charged inner surface of the capillary, thus minimizing electrostatic interaction of the solutes with both unreacted silanols and the quaternary ammonium groups which had been introduced. As a consequence, high separation efficiencies were achieved with proteins, nucleotides, and a series of acidic oligosaccharides.

ISSN:0935-6304    

DOI:10.1002/jhrc.1240150903

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1992

数据来源: WILEY

摘要:

AbstractMethods of alkylation of α‐, β‐ and γ‐cyclodextrins have been optimized with regard to the parameters of reaction, degree of alkylation and yields. The analysis of the reaction mixtures and of the isolated single species has been performed by high temperature GC and HPLC. The phase systems of the preferably applied HPLC have been carefully adjusted by variation of both the stationary and mobile phases to the very different hydrophobicities of the various alkylated CD species which have been synthesized. Several partially or fully alkylated CD species were isolated from preparative scale HPLC separations in hig

ISSN:0935-6304    

DOI:10.1002/jhrc.1240150904

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1992

数据来源: WILEY

摘要:

AbstractA commercially available high temperature GC system has been investigated to determine its suitability for the automated analysis of sucrose fatty acid esters. In comparison with conventional GC, the high temperature variety broadens the scope of the technique to encompass high molecular weight carbohydrate derivatives while maintaining high separation efficiency. Despite the broad range of polarities, simultaneous quantification of educts and sucrose fatty acid ester fractions is possible in one run, after derivatization. Chromatographic requirements, sample preparation, structure verification by direct chemical ionization mass spectrometry, and advantages and limitations of the high temperature GC‐analysis are discusse

ISSN:0935-6304    

DOI:10.1002/jhrc.1240150905

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1992

数据来源: WILEY

摘要:

AbstractThe characteristics of the new chiral stationary phase heptakis(2,3‐di‐O‐methyl‐6‐O‐tert‐butyldimethylsilyl)‐β‐cyclodextrin are outlined and compared with permethyl‐ and pere

ISSN:0935-6304    

DOI:10.1002/jhrc.1240150906

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1992

数据来源: WILEY

摘要:

AbstractThe mobile phase of a fraction eluted from a first LC column is removed by an on‐line evaporator in order to reconcentrate the solute material or to exchange the eluent before performing a subsequent LC separation. Evaporation essentially occurs by concurrent evaporation,i.e.the solvent evaporates at a rate equal to the flow rate of the incoming eluent, and is driven by the overflow principle,i.e.vapors leave the tube as a result of the expansion resulting from evaporation.The liquid is introduced into a small tube (e.g., 4 cm × 1.3 mm i.d.) which is packed,e.g., with a coarse silica gel. The outlet of the evaporator is connected to vacuum in order to enable evaporation at reduced temperature and to increase retention of the volatile components. With normal phase eluents, evaporation rates may approach 1 ml/min;n‐dodecane was the most volatilen‐alkane fully retained by the evap

ISSN:0935-6304    

DOI:10.1002/jhrc.1240150907

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1992

数据来源: WILEY

摘要:

AbstractSolid‐phase extraction, capillary GC, and mass selective detection have been used to determine 3‐carboxy‐4‐methyl‐5‐propyl‐2‐furanpropionic acid (furanpropionic acid) and hippuric acid in the plasma of patients with chronic renal failure. The concentrations of furanpropionic acid and hippuric acid were found to be highly elevated and reached levels of 4.56 ± 2.37 mg/dl (10 to 20‐fold higher than normal) and 12.90 ± 14.06 mg/dl (40 to 60‐fold), respectively. Treatment by hemodialysis and hemofiltration effectively eliminated hippuric acid (on average by 66 and 56%, respectively) but had little effect on furanpropionic acid. Intermittent peritoneal dialysis gave the best long‐term results. Both components were maintained at a lower level than by hemodial

ISSN:0935-6304    

DOI:10.1002/jhrc.1240150908

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1992

数据来源: WILEY

摘要:

AbstractA small amount of mercuric non‐porous resin placed in the liner of the injection splitter of a gas chromatograph retains mercaptans but allows other organic sulfur and non‐sulfur compounds to be chromatographed normally: mercaptans in the gaseous state are retained by the mercuric resin. The method works well at 200°C but an increasing number of impurity peaks are observed as the temperature is increased to 2

ISSN:0935-6304    

DOI:10.1002/jhrc.1240150909

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1992

数据来源: WILEY

摘要:

AbstractVegetable oil methyl esters are increasingly being used as substitutes for petroleum‐based diesel fuels. Because the presence of triglycerides and partial glycerides in the fuel as a result of incomplete transesterification of vegetable oils can lead to serious engine problems, continuous quality control of the product is essential. A rapid gas chromatographic method has been developed for the quantitative determination of mono‐, di‐, and triglycerides in vegetable oil methyl esters.Prior to analysis, mono‐, and diglycerides were silylated withN,O‐bis(trimethylsilyl)trifluoroacetamide; tridecanoin was used as internal standard. Calibration was performed by analysis of standard solutions containing mono‐, di‐, and triolein: the calibration plots for mono‐ and diglycerides showed good linearity, whereas for triglycerides no linearity was observed for triolein concentrations below 0.05 mg/ml. When a non‐linear multi level calibration was employed for the quantitation of triglycerides, the method gave excellent quantitative results for mono‐, di‐, and triglycerides in vegeta

ISSN:0935-6304    

DOI:10.1002/jhrc.1240150910

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1992

数据来源: WILEY

摘要:

AbstractRecently introduced fused silica, primarily of the high temperature type, no longer allows the formation of a reliable press‐fit seal. Attempts to tighten the connection with various kinds of glue proved unsatisfactory. Manufacturers of fused silica tubing are urged to devote more attention to the proble

ISSN:0935-6304    

DOI:10.1002/jhrc.1240150911

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1992

数据来源: WILEY