Sample preparation cycle time

In studies performed in our lab, we use a fully automated purification device developed by Lunkenheimer et. al. which ensures a complete removal of these unwanted trace impurities [18]. The aqueous stock solution undergoes numerous of purification cycles consisting of a) compression of the surface layer, b) its removal with the aid of a capillary, c) dilation to an increased surface and d) formation of a new adsorption layer. At the end of each cycle the surface tension cr is measured. The solution is referred to as surface chemically pure grade if ae remains constant in between subsequent cycles. Quite frequently more than 300 cycles and a total time of several days are required to achieve the desired state. The sample preparation is time consuming and tedious but mandatory for the investigation of equilibrium properties of adsorption layers of soluble surfactants at the air-liquid interface. 

Today, structure evolution can be tracked in-situ with a cycle time of less than a second. Moreover, if a polymer part is scanned by the X-ray beam of a microbeam setup, the variation of structure and orientation can be documented with a spatial resolution of 1 pm. For the application of X-rays no special sample preparation is required, and as the beam may travel through air for at least several centimeters, manufacturing or ageing machinery can be integrated in the beamline with ease. 

Cycle time consists of several individual components. One is the separation time of a sample. Another component is instrument overhead time that may be subdivided into conditioning, sample preparation, and post-separation phases. The final component is system overhead time that covers delays caused outside the LC modules (Figure 3.9). These times do not necessarily have to follow the fixed order shown in the figure. In particular, the position of the instrument conditioning may vary and the tasks do not have to be arranged linearly. Cycle times in early chromatographic systems... 

In our laboratories, a cycle time of 90 sec can be achieved with a dilution factor of 1 25 for a given sample concentration, allowing the purity and identity control of two and a half 384-well microtiter plates per day. The online dilution eliminated an external step in the workflow and reduced the risks of decomposition of samples in the solvent mixture (weakly acidic aqueous solvent) required for analysis. Mao et al.23 described an example in which parallel sample preparation reduced steps in the workflow. They described a 2-min cycle time for the analysis of nefazodone and its metabolites for pharmacokinetic studies. The cycle time included complete solid phase extraction of neat samples, chromatographic separation, and LC/MS/MS analysis. The method was fully validated and proved rugged for high-throughput analysis of more than 5000 human plasma samples. Many papers published about this topic describe different methods of sample preparation. Hyotylainen24 has written a recent review. 

Such columns are excellent filters and require more sample preparation to ensure the removal of all solids. To benefit from the full power of LC optimization, the detectors must be optimized as well. Data rates and duty times must match the narrower peaks in very fast (and well resolving) separations. Careful consideration and optimization of all instrument components and software can produce significant cycle time improvements of fast LC separations and further increase throughput. An important aspect of cycle time improvement is parallelization of components of individual analyses. 

Because the instability of the N-oxide metabolite, which was subjected to decomposition during sample preparation (solvent evaporation during offline SPE), online SPE LC/MS became the method of choice for the application. Hsieh et al. (2004) built a system with two TFC cartridges and one analytical column, and another system with two TFC cartridges and two analytical columns for GLP quantitative bioanalysis of drug candidates. A Turbo C18 (50 x 1.0 mm, 5 /.mi, Cohesive Technologies), an Xterra MS C18 (30 x 2.0 mm, 2.5 /mi), and a guard column were used. Protein precipitation preceded injection. The cycle times for the two systems were 0.8 and 0.4 min. 

Since the HPLC-MS cycle time (the chromatographic run time plus the autosampler injection time) is usually governed by the chromatographic system, focus has been given to sample preparation and chromatographic techniques. 

SCIEX API 365 equipped with a TurboIonSpray interface operated in positive ion mode. The calibration range 0.124-497 ng/mL was readily validated with a negligible carry-over effect from this system. The method offered a total cycle time of 8 min and completely eliminated the manual sample preparation. ... 

Refinement approaches lead to a decreased cycle time via the faster and more efficient analysis of samples. Automation is an obvious and desirable goal to speed up the analysis, optimize the measurement, and coordinate diverse tasks. A tremendous emphasis is placed on aspects of analysis such as sample preparation and data processing and data management. Once considered to be peripheral to the actual analysis, these activities have become important elements of high throughput analysis. 

A list of the 64 analytes and their method performance is shown in Table 6.6. The increased number of analytes is possible because of improvements to the collision region of the MS/MS system that provide increased sensitivity and reduced memory effects. In addition, robotic systems for sample handling and on-line solid-phase extraction (SPE) of plasma samples were integrated with the LC/MS/MS system (Figure 6.22). An isocratic reversed-phase HPLC method provided a cycle time of 4.5 min per sample. The on-line sample preparation and short analysis resulted in an increased sample throughput that required less time from the scientist. The... 

Minimal sample preparation (dilution in HPLC mobile phase) is necessary. A standard reversed-phase HPLC method is used for all the samples associated with a drug candidate to reduce time-consuming method development/method refinement procedures. Standard reversed-phase methods typically involve a 20-30 min cycle time and provide information on a wide range of compounds. The incorporation of a standard method strategy allows the use of autosampling procedures and standard system software for data analysis. 

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