LCGC Asia Pacific-12-01-2007

Multidimensional liquid chromatography (MDLC) techniques are essential for the separation of highly complex proteomic samples. Advantages of off-line MDLC techniques over on-line approaches include high flexibility in choice of column dimensions and mobile-phase compositions, and the ability to reanalyse sample fractions. Here we present a fully automated off-line two-dimensional chromatographic approach for the analysis of proteomic samples using an UltiMate 3000 system optimized for proteomics MDLC.

Combining an ultra fast LC system (e.g., Agilent 1200RRLC, Waters UPLC) with an accurate mass TOF mass spectrometer creates a powerful system for information-rich high-throughput analyses. However, for de novo formula generation and confirmation the residual mass accuracy tolerance of 3–5 ppm can still leave significant ambiguity in the proposed formula. Consequently, skilled manual inspection or further measurements deploying additional analytical techniques (NMR or MS–MS) are frequently required to arrive at a confident formula assignment.

Using ACQUITY UPLC technology with triple quadrupole MS detection enhances the selectivity, sensitivity and throughput in quantitative bioanalytical studies. Detection limits for these methods are being driven lower and lower as drugs become more potent.

The pyrolysis fragments are first refocused on the top of the GC column, then separated and finally detected by the MS. At the end of the GC run the SEC flow is resumed again and the entire process is repeated.

Calvados is an apple-brandy of Normandy (France). Mashed apples are fermented to obtain cider, which is then distilled to give the young spirit.

The process of investigating a suspicious fire includes many different types of analyses. An essential step in confirming the presence of a liquid accelerant is gas chromatography (GC); detection with a mass spectrometer (MS) provides an accurate confirmation of both the presence and identity of an accelerant. In arson analysis, the sample preparation for GC–MS analysis is typically performed by headspace or solvent extraction.

LCGC Asia Pacific
LC Troubleshooting

December 01, 2007

The various surface characteristics have different capacities and equilibration rates, which can affect the appearance of the chromatograms.

PLOT columns are often used in GC analyses when it is necessary or desirable to retain one class of solutes in favour of other solutes that have little or limited interactions with the surface of the stationary phase. With a PLOT column, chromatographers can even cause lower boiling point compounds to elute well after higher boiling point compounds, thus providing better qualitative and quantitative separations for the solutes of interest.

LCGC Asia Pacific
China Focus

December 01, 2007

Chromatography–Mass Spectrometry at Hong Kong Baptist University; Chromatography at the Department of Chemistry, Peking University; Separation Science at National Chi Nan University in Taiwan; Green Analytical Chemistry at National Tsing Hua University; Separation Sciences at Tsinghua University

LCGC Asia Pacific
Multidimensional Chromatography

December 01, 2007

Proteins can be separated according to their isoelectric points on an ion-exchange column using pH gradients in the first dimension and according to their hydrophobicity on an RP column in the second dimension.