Liquid purification or separation – With means to add treating material – Chromatography
Reexamination Certificate
2000-10-26
2002-06-11
Therkorn, Ernest G. (Department: 1723)
Liquid purification or separation
With means to add treating material
Chromatography
C210S659000, C422S070000, C073S061560
Reexamination Certificate
active
06402946
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a device for feeding a chromatography flow coming from a flow source, in particular from a liquid chromatography (LC) separating unit or a peak sampling or trapping unit, in part to at least a first decision detector unit and/or at least a first destination detector unit and in part to at least a second destination detector unit, comprising a first capillary line coming from the flow source, a second capillary line leading to the first decision detector unit and/or to the first destination detector unit, and a third capillary line leading to the second destination detector unit, the first, second and third capillary line being connected with one another by means of a flow splitter splitting the flow coming from the first capillary line into two parts, a first part being fed into the second capillary line and the second part being fed into the third capillary line.
The invention further relates to an apparatus for carrying out coupled liquid chromatography (LC) and at least two spectrometry measurements, comprising a LC separating unit, at least a first decision detector unit and at least a first destination detector unit and at least a second destination detector unit, in which the device mentioned before is used.
An apparatus and a device of the kind mentioned before, which are generally known are used in liquid chromatography (LC), in particular in high performance liquid chromatography (HPLC). Liquid chromatography is a known method for separating components of trace elements within liquid substrates to be analyzed.
Further, it is well-known to combine LC with nuclear magnetic resonance (NMR) spectroscopy measurements. The LC is used to separate components of a sample, which are selected in a LC detector, and the selected components were measured afterwards using NMR as the first destination detector unit. The coupling of LC with NMR is nowadays a well-known and accepted technique in science and industry.
For the technique of LC-NMR, four automation modes are known, as they are “on-flow”, “stopped-flow”, “time-slicing” and “loop-sampling”.
In a pure on-line coupling, the NMR detector is directly coupled after the liquid chromatograph. In this on-line mode the separated peaks are fed from the LC continuously into the NMR detector to be spectrometrically examined on-line therein.
As an alternative to the on-line mode the stopped-flow technique is used, wherein the flow pump of the LC is stopped as long as a component is investigated inside the NMR detector.
The peak-sampling mode is a mode in which single separated peaks coming from the LC are selected and intermediately stored in a peak sampling unit for later successive investigation in the NMR detector.
The time-slicing mode is a clocked mode in which the LC peaks can be investigated in equally timed fractions to observe spectroscopic changes over a certain elution period.
Right from the beginning of commercializing the combined method of LC-NMR, the idea to hyphenate LC-NMR with additional sophisticated detection methods like mass spectroscopy (MS) as the second destination detector unit existed. Early attempts to combine LC-NMR with MS in 1996 have shown that the information obtained from such a combination was unsurpassed, in particular the selectivity of the peak selection of the LC peaks for further NMR investigation is increased substantially. As described by John P. Shockcor et al. in Anal.Chem. 1996, 68, 4431-4435, the advantage of combined LC-NMR-MS is that the structural information available from the complementary spectroscopic techniques provides rapid confirmation of the identity of the components of the sample.
Heretofore, in order to connect the LC-NMR system with the MS, in all cases just a flow splitter was hooked into the flow path, i.e. the flow splitter splits the flow coming from the first capillary line coming from the LC into two parts, the first part being fed into the second capillary line and the second part being fed into the third capillary line. The second capillary line leads to the LC detector as the first decision detector unit and/or the NMR detector as the first destination detector unit, while the third capillary line leads to the MS as the second destination detector unit. The split ratio between the first part of flow and the second part of flow varied from case to case between 50:1 and 20:1. The larger part of flow is used to feed the NMR detector, and the lower one for the more sensitive MS detector. In general, the users of the LC-NMR-MS system tried to adjust the timing for the MS such that the time a separated peak needed to reach the NMR was equal to or longer than the time to reach the MS.
Depending on the position of the splitter in the entire LC-NMR-MS system, it was possible to use the MS signal to trigger a stop of the chromatography for an NMR measurement, but not to use the MS signal to trigger the storage of the peak in a loop of the peak-sampling unit. All known systems, however, are restricted in the flexibility of their use. The known systems do not take into account that the time scales of the NMR measurements and the MS measurements are quite different. The NMR measurement runs on a time scale which is longer than the time scale of the MS measurements.
Whereas in the preceding description reference has been made to a coupled LC-NMR-MS system, the present invention is not restricted to such a combination, but can be used for other combinations of LC with at least two destination detectors, like for example infrared detectors or light-scattering detectors.
In the present description, a “decision detector” is to be understood as a detector, the signals of which are used for subsequent actions of the device or apparatus, while a “destination detector” is to be understood as a detector for detailed investigation and analysis of a sample peak.
It is therefore an object of the present invention to improve a device and an apparatus of the kind mentioned at the outset which allow a coupling of a flow source, in particular a LC separating unit with at least two detector units with a high degree of flexibility in using different modes of LC.
SUMMARY OF THE INVENTION
This object is achieved in terms of a device mentioned at the outset in that a first switchable valve means is provided which is connected to the third capillary line and to the second destination detector unit, which has at least two operating positions, wherein in at least a first group of at least one operating position the third capillary line is connected directly to the second destination detector unit, and wherein in at least one second group of at least one operating position the third capillary line is connected to at least one delay line.
By virtue of the first switchable valve means, the flexibility in use of the device according to the invention is advantageously increased. When the first valve means is in the at least one first operating position, the sample flow can quickly reach the second destination detector unit, for example a MS detector, so that the second destination detector unit signal can be used to trigger one of the LC modes which was not possible heretofore with the known systems. In other words, one of the dominant benefits of the present invention is that the second destination detector can advantageously be used as a decision detector for triggering subsequent actions of the device and/or apparatus. In particular, if the second detector unit comprises a MS detector, the high sensitivity of the MS signal can be used for triggering further action and choice of the LC mode, for example on-flow, stopped-flow or loop-sampling action, in particular for selecting peaks of interests from the sample flow. On the other hand, when the first valve means is in the at least one second operating position, this can be used for the sample flow to reach the second detector unit with a certain delay. This can be advantageously used in the on-flow mode in case that the delay is matched to the path from the splitter to the first detector unit, to
Hofmann Martin
Spraul Manfred
Bruker Analytik GmbH
Therkorn Ernest G.
Weingarten Schurgin, Gagnebin & Lebovici LLP
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