Determination of Trace VOCs in AIR using an Automated Thermal Desorption-GC System
Manuela Bergna, DANI Instruments, Italy
Samples containing pollutants at low concentration (ppb, ppt range) normally require additional sample concentration before analysis.
The preconcentration step is conventionally carried out by passing the air sample through sorbent tubes that retain and concentrate the pollutants. The retained components are recovered through the application of heat and a flow of inert gas and directly transferred to a gas chromatograph.Compared to liquid extraction, thermal desorption offers extremely higher sensitivity, complete transfer of the component to the analytical system, sample tube reusing, absence of solvent and no sample preparation. A DANI STD1000 thermal desorber was coupled to a gas chromatograph DANI GC1000 configured with a capillary column for the trace analysis of VOCs in air.STD1000 is a two-stage thermal desorber with refocusing on Peltier cooled packed trap. An instant heating of the trap provides rapid transferring of components, directly to the analytical column in a completely automated way without affecting the excellent resolution and peak shape of the narrow bore capillary columns.
Selecting the proper sorbents and analytical conditions, the system can be configured for the determinations of selected VOCs.
Applications will be presented obtained from the analysis of air samples in environmental monitoring and control of pollution, as well as practice of industrial or occupational hygiene.
New Headspace and Liquid Autosamplers to fit any GC
Mark Wardle, SMI, UK
Modern, and not so modern, gas chromatographs can be expected to have a useable life well in excess of 10 years. We all remember the ubiquitous Pye 104’s some of which are still in operation even today!
Unfortunately the autosamplers which are often sold with them, as mechanical instruments generally have a life expectancy of around half that of the GC. Replacements can be expensive from the instrument manufacturer, always assuming that one is still available.
A new range of samplers is now available which are designed to operate on any GC with a top loading injector including the complete Agilent range, along with Shimadzu, Dani, Varian etc.
The samplers include a new static headspace unit with a 6 position orbital heater/shaker, heated syringe mechanism and 40 position sample tray, and a liquid sample injector for 10 or 110 samples.
Based on the same technology, the manufacturer has also recently introduced an HPLC autosampler version and an NMR tube cleaner which attracted significant interest at its recent Pittcon launch.
Die Injektion - eine Schwachstelle bei der GC-Analytik
Bernd Pfeffer, SGE (Deutschland) GmbH
Die GC-Analytik ist heutzutage eine sehr robuste und ausgereifte Technik, aber die Injektion kann immer wieder Probleme verursachen. Um diese weitestgehend zu vermeiden, ist die richtige Kombination von Liner, Septum, Spritze und Injektionstechnik sehr wichtig - dies soll im Detail besprochen werden.
Nano-, Micro- und Kapillar-HPLC
Felix Friedli, MSP Friedli & Co
Die heute gängigen LC/MS Interfaces (ESI, APCI, APPI) sind problemlos mit den für konventionelle Säulendurchmesser (2.1 - 4.6mm ID) üblichen Flussraten von 300_l-1200_l/min zu betreiben. Bei dem am häufigsten verwendeten ESI-Interface ist das Signal konzentrationsabhängig . Deshalb kann die Empfindlichkeit einer Methode durch Verwendung kleinerer Flüsse proportional zur Verringerung der Flussrate gesteigert werden.
Für diese Anwendungen bietet Agilent Technologies ab Juli 2002 ein komplettes 2D-Nano-HPLC-System bestehend aus LC/MS-Hardware, integrierter Systemsoftware, sowie einer kompletten Auswahl geeigneter Trappingsäulen und RP-Trennsäulen an. Das komplette 2D-Nano-LC/MS-System basiert auf der Agilent LC/MSD Ion Trap und ist speziell optimiert für Anwendungen aus dem Proteomics-Bereich.
Systeme für die Micro- and Nano- HPLC: Prinzipien und Realisierung
Dr. Jürgen Maier-Rosenkranz, Grom Analytik + HPLC GmbH |