Search results for "Performance."

Non-porous microparticulate supports in high-performance liquid chromatography (HPLC) of biopolymers — concepts, realization and prospects

1986

Profiling of endogenous peptides by multidimensional liquid chromatography: On-line automated sample cleanup for biomarker discovery in human urine.

2009

A simple and flexible system, employing a column switching technique, has been designed to allow the analysis of peptides and proteins smaller than 15 kDa by molecular weight in filtered urine samples by performing a direct on-column injection utilising simultaneous sample clean-up and trace enrichment. The positively charged peptides and small proteins in the sample are attracted to the inner, negatively charged pore structure of the RAM-SCX column while the larger proteins and uncharged or negatively charged compounds are excluded. After preconditioning with the biological sample, large amounts of sample can be injected. Several important and adjustable parameters for the proper use of a …

Gel permeation Chromatography in coiled columns

1973

Whereas in gas chromatography the use of coiled columns is the usual procedure, in liquid chromatography the use of straight columns is favoured. Bent columns give an additional contribution to peak spreading which is of greater importance in liquid chromatography than in gas chromatography owing to smaller diffusion coefficients. The low linear velocities of the mobile phase used in gel permeation chromatography enable conditions to be found where the additional contribution of bending to peak spreading is small. In the separation of oligomers, columns of 2-mm tube diameter and 20-cm coil diameter were used. With total lengths of 10 and 20 m, theoretical plate counts of ca. 70,000 and 150,…

Comparison of liquid chromatography using triple quadrupole and quadrupole ion trap mass analyzers to determine pesticide residues in oranges.

2005

Liquid chromatography-triple quadrupole/mass spectrometry (LC-TQ/MS) and liquid chromatography-quadrupole ion trap/mass spectrometry (LC-QIT/MS) for determining bupirimate, hexaflumuron, tebufenpyrad, buprofezin, pyriproxyfen, and fluvalinate in fruits have been compared. The differences in the mass spectra obtained by triple and ion trap quadrupoles are discussed, showing how both of them provide interesting features. The evaluation of the two instruments was carried out by ethyl acetate extraction of oranges spiked with the studied pesticides at LOQ and 10 times the LOQ. Results obtained by LC-TQ/MS correlated well with those obtained by LC-QIT/MS. Recoveries were 70-94% by LC-TQ/MS and 7…

Comments on the use of alumina in HPLC

1984

Anwendungsmöglichkeiten der HPLC bei der Trennung, Isolierung, Identifizierung und quantitativen Bestimmung von Substanzen aus komplexen Stoffgemisch…

1982

Es wird die Anwendung der Hochdruckflussigchromatographie (HPLC) in Bezug auf die Identifizierung und quantitative Bestimmung von Carbonsauren in Aluminatlaugen aus dem Bayerprozes beschrieben. Die Vorgehensweise besteht in folgenden Teilschritten: Optimierung von HPLC Phasensystemen zur Trennung von synthetischen Gemischen von Carbonsauren, Aufarbeitung der Aluminatlauge, semi-praparative Isolierung von Substanzen, Identifizierung auf flussigchromatographischem Wege und durch Massenspektrometrie, quantitative Bestimmung durch Peakhohenauswertung mit Hilfe externer Standards.

Analysis of pharmaceutical preparations containing local anesthetics by micellar liquid chromatography and spectrophotometric detection

1999

An HPLC procedure for the determination of six local anesthetics, bupivacaine, lidocaine, mepivacaine, procaine, propanocaine and tetracaine, in pharmaceutical silane ODS-2 C18 analytical column and spectrophotometric detection at 230 nm were used. The chromatographic tographic behaviour of local anesthetics with different micellar eluents of sodium dodecyl sulphate (SDS) is described. Selection of the adequate composition of the micellar mobile phase (SDS and 1-propanol concentrations) for the analysis of pharmaceuticals was studied. Adequate retention was achieved with an eluent containing 0.15 M SDS +10% 1-propanol at pH 3. Application of the proposed method to the analysis of eight phar…

Packing technology, column bed structure and chromatographic performance of 1-2-μm non-porous silicas in high-performance liquid chromatography

1989

This work is aimed at further elucidating the aggregation behaviour of micron- and submicron-size non-porous silicas and the column performance of 1–2-μm C18 silicas in reversed-phase high-performance liquid chromatography of low-molecular weight compounds. It is demonstrated that highly ordered, dense, porous aggregates of such silica beads were obtained by gravity settling and centrifugation. The slurry techniques applied at constant flow-rate and a pressure up to 50 MPa provided less-ordered aggregates, but generated an acceptable performance of columns when 1–2-μm C18 silica beads were employed. To operate columns of 53 mm × 4.6 mm I.D., the maximum flow-rate needs to be ca. 2.5 ml/min …

High-performance liquid chromatographic determination of furfural compounds in infant formulas

2002

Furfural contents in adapted and follow-up infant formulas were measured by RP-HPLC. The evolution of furfural compound contents during storage (a year at 20 and 37 °C) was studied. 2-Furylmethylketone and 5-methyl-2-furaldehyde were not detectable in analysed samples. The differences in the furfural compounds at point zero between both infant formulas has to be ascribed to the differences in protein and iron contents. An increase in free 5-hydroxymethyl-2-furfuraldehyde (HMF), 2-furaldehyde (F) and HMF+F contents was observed in all samples, although the differences were not statistically significant. The storage temperature affected the total HMF content and the storage time affected the …

Emerging approaches to estimate retention factors in high performance liquid chromatography.

2004

The retention factor is one of the most universally used parameters in chromatography. The errors associated with the conventional ways to determine the retention factor of compounds in liquid chromatography are studied and compared with those corresponding to new approaches. The later avoid the use of extra-column time and hold-up time values, which have proven to be tedious and ambiguous. Simulations and real data, used to examine the accuracy of four different approaches (two classic and two new), suggest that the new approaches could be considered more satisfactory than the classic ones.