Sample throughput maximization

The laboratories maximize their sample throughput by reducing the number of samples that need reanalysis due to dilution. To reach this end, they routinely calibrate all of the instruments using the widest possible calibration range that spans the full linear dynamic range of the detector. 

Before laboratory QC checks are discussed, we need to revisit the concept of batch analysis introduced in Chapter 4.3. Laboratories process samples in a batch manner by assembling sets of samples that are prepared and analyzed together. Batch analysis enables laboratories to maximize sample throughput while performing a minimum of the required laboratory QC checks. 

It is evident that wet decomposition methods remain a fertile area for development. New digestion techniques need to be designed that address the limitations of the instrumentation and maximize its potential. Development trends for conventional and microwave instmments will focus on sample throughput, enhanced vessel performance specifications, the use of new materials, further refinement of in situ vessel control (direct temperature and pressure, incident and reflected microwave power), and computer-controlled sample digesters with automated capability. 

However, there is a limitation in terms of the maximal achievable sample throughput rate because of the planar nanochannel with a nanometer-scale cross-sectional area for separation. The maximum flow rate achievable with the planar nanochannel device was OTily 1 nL/h. To further increase the flow rate. Pan et al. buUt a massively parallel vertical nanoarray [ 26]. To decrease the gap size of photolithograph-icaUy patterned microchannels with a gap size of 1 pm, a thermal oxidation process was applied on Si with a volume expansion of about a factor of 2.3. By controlling the oxidation time, the gap size of the vertical nanochannels could be controlled down to below 100 nm and the... 

When the analyst is not so fortunate and no comparable published method is available, a completely new method may need to be developed. In either instance, the process of method optimization is necessary. Note that the analyst determines the definition of the term optimization. To begin the optimization process, criteria [i.e., minimal (value must be >A ), maximal (value must be <7), or bounded (between X and T)] are established for any or all of the following peak shape, peak height, peak separation, run time, and overall analysis time (and therefore sample throughput). For the last listed criterion, remember that in gradient separations the re-equilibration time must be considered as part of the analysis time since a subsequent injection cannot occur until after the system has reached equilibrium with the initial solvent... 

With the increasing demand to analyze more and more samples, manufacturers of autosamplers and sample introduction accessories are designing automated sampling systems to maximize sample throughput. This is being achieved in a variety of different ways by optimizing the sample delivery process to reduce the pre- and postmeasurement time. Some typical optimization procedures include the following ... 

Chromatography is typically at atmospheric pressure while source pressures in the mass spectrometer are in the range of 2 to 10 Torr for chemical and electron impact ionization, respectively. The interface must be capable of providing an adequate pressure drop between the two instruments and should also maximize the throughput of seuaple idiile maintaining a gas flow rate compatible with the source operating pressure. Further, the Interface should not introduce excessive dead volume at the column exit and should not degrade or modify the chemical constitution of the sample. 

In order to maximize throughput it is necessary to scan several samples simultaneously within the same imaging sequence. To this end a multi-compartment tubular holder, placed within a volume coil, was used which enabled up to 14 rat heads and 5 rabbit heads in parallel to be imaged (Fig. 1). The tubular holders were custom-made and were constructed from commonly available specimen tubes which were cut to size and glued together. The closed ends of the tubes are conical in shape which aids with the positioning of the sample as an ink spot on the snout of each fetus is aligned with the tip of the cone to control out-of-plane rotation. 

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