Multichannel parallel detector

Fig. 4. Schematic representation of a commercial parallel LC/MS system. Liquid flow is delivered to eight columns by a pump and a flowsplitter. Peaks are detected by a multichannel UV detector and a TOF mass spectrometer with a multiplexed electrospray source...

A schematic of a commercially available system that was conflgured in our laboratory for parallel analysis and purification is shown in Figure 11-9. This four-channel parallel LC/MS purification system consists of a binary HPLC system, an autosampler configured with four injection, a multichannel UV detector, a quadrupole mass spectrometer equipped with an MUX ion source which monitors four flow streams simultaneously, and four independently... 

Tang et al. introduced a multichannel electrochemical detector (MED) consisting of eight sets of electrodes inserted into a row of eight wells of a microtiter plate as depicted in Fig. 14.11.60 The device was successfully used to perform parallel amperometric immunoassays. 

The multichannel plate detector (MCP) is a porous glass plate in which each pore acts as a mini electron multiplier. The MCP is a set of parallel multipliers. 

By 1978 when the ACS symposium on multichannel detectors was convened [26], it was recognized that a multichannel spectrograph could provide large reductions in the time for collection of spectra. No one would use photographic plates anymore because of their low quantum efficiency (QE), the low accuracy and precision of the measurement, the tedious calibration, and especially the slow plate-development time. The time had come for introducing state-of-the-art TV cameras as well as other opto-electronic devices as spectrometric parallel detectors. 

The //PLC system described in this chapter is equipped with 24 parallel columns for liquid chromatography, each with its own sample introduction port and exit port for connection to detectors of choice (UV absorbance and/ or fluorescence). Flow from a binary solvent delivery system is divided evenly across 24 channels and results in 1/24 of the programmed pump flow rate through each column (i.e., total flow of 300 /zL/ min will produce a flow of 12.5 /zL/ min in each column). Samples are introduced to the columns by a multichannel autosampler configured to sample from either 96-or 384-well SBS standard plates. Figure 6.2 depicts a general view of the system. 

The instrument is composed of an interface to plug the disposable cartridge, a temperature controller, a multichannel pumping device and valves as well as a multiplexer electrochemical detector for sequential or parallel detection of the amperometric events occurring in each of the eight channels for some protocols, it can also serve to deliver different reagents such as the secondary antibody or the substrate and thus provide fully automatic assays. 

Multichannel HPLC—HPLC system designed to run parallel HPLC columns into a multi-flow cell UV or fluorescent detector. Designed for production laboratories to speed QA/QC monitoring (see Chapter 16). 

Source compensation Pulse-to-pulse intensity variations and intensity fluctuations in the spectrometric excitation source are often the dominant noise source affecting the performance of the detection system. However, since OIDs are parallel multichannel detectors, these intensityvariations do equally and simultaneously affect the entire spectral distribution as a whole. Thus, with the aid of a single-channel reference detector, monitoring a portion of the source s light flux, it is possible to accurately normalize for spectrum-to-spectrum variations and practically eliminate these and any other source flicker noise related effects. 

To acquire this information, the two displaced continuum beams are imaged with a cylindrical and a spherical lens onto different positions along the length of the entrance slit of a low dispersion spectrograph (Instruments SA, model UFS-200). The two resulting parallel dispersed spectra are fully separated from each other at the focal plane, where they are detected by the model 1254 SIT detector head of an EG + G Princeton Applied Research Corporation optical multichannel analyzer system. In conjunction with a model 1216 detector controller and model 1215 console, this detector is programmed with a two dimensional... 

It should also be noted at this point that a multichannel detector can have multiple detector elements along two axes, one parallel to the direction of wavelength dispersion, and one perpendicular. The latter is parallel to the entrance slit in most dispersive instruments. For example, a CCD may have 1024 pixels along the wavelength axis and 256 along the vertical axis, for a total of 262,144 independent elements. This second dimension of the detector may be used in a variety of applications involving Raman imaging, multiple detection tracks, or echelle spectrometers. 

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