Turn-around times

Atomic absorption spectroscopy of VPD solutions (VPD-AAS) and instrumental neutron activation analysis (INAA) offer similar detection limits for metallic impurities with silicon substrates. The main advantage of TXRF, compared to VPD-AAS, is its multielement capability AAS is a sequential technique that requires a specific lamp to detect each element. Furthermore, the problem of blank values is of little importance with TXRF because no handling of the analytical solution is involved. On the other hand, adequately sensitive detection of sodium is possible only by using VPD-AAS. INAA is basically a bulk analysis technique, while TXRF is sensitive only to the surface. In addition, TXRF is fast, with an typical analysis time of 1000 s turn-around times for INAA are on the order of weeks. Gallium arsenide surfaces can be analyzed neither by AAS nor by INAA. 

NAA cannot be used for some important elements, such as aluminum (in a Si or Si02 matrix) and boron. The radioactivity produced from silicon directly interferes with that ftom aluminum, while boron does not produce any radioisotope following neutron irradiation. (However, an in-beam neutron method known as neutron depth profiling C3J be used to obtain boron depth profiles in thin films. ) Another limitation of NAA is the long turn-around time necessary to complete the experiment. A typical survey measurement of all impurities in a sample may take 2-4 weeks. 

All of the types of repairs described can be accomplished using electron/X-ray curing and suitable electron-curable adhesive systems. The advantages ol using an electron accelerator are faster curing cycles, short turn-around time, and higher-temperature-resistant bonds, cured at ambient temperatures. 

Considerations of turn around time for the analysis, the statistical confidence level and the specificity required also play a part in the decision. Even a so called quick and dirty method can become quantitative to an acceptable extent once conditions are standardized. 

Turn around time and customer service analysis Cost per analysis computation Equipment utilization analysis... 

Returning to our discussion of benefits, we note that they fell into two principal areas the time-value of information and the improvement in laboratory productivity. As we saw, assessing the benefits from the time-value of information requires examination of the total process through which that information will be used. For example, using data such as the anticipated improvement in laboratory turn around time, the rate at which material Is produced and its value, and the current the financial losses attributable to scrap or rework, one can estimate the savings in dollars to be accrued (each hour of faulty production avoided through faster lab turnaround time yields as a gain to the firm, the revenue that otherwise would have been lost). 

Turn-around-time Usually longer, with Usually much shorter,... 

High-throughput laboratories have turned to assay automation, N-in-one (sample pooling) analysis strategies, and elaborate set-ups for parallel chromatography30 33 to increase capacity and decrease turn-around time. Despite the relatively fast speed of HPLC/MS, this step still creates a bottleneck in ADME work flow. Xu et al.32 reported a fast method for microsomal sample analysis that yields 231 data points per hour using a complex eight-column HPLC/MS set-up. 

Solid phase extraction (SPE) is fast and can work as a clean-up method when combined with capillary electrophoresis or used prior to HPLC/MS.34-37 Kerns et al.35 described an online alternating parallel SPE column with MS/MS detection and a turn-around time of 1.1 min. 

Because high ratios of SPMEs and POGs also mean rapid desorption of accumulated residues, samplers must be frozen at sub-zero temperatures and transport and storage times must be minimized. Mayer et al. (2000) analyzed SPMEs by GC within 20 s of sample removal in the matrix-SPME study. To enable rapid turn-around times for sample data, and to minimize transport and storage problems, Gorecki and Pawliszyn (1997) developed a field-portable SPME/fast GC system for sampling VOCs. However, at more remote sites the need for electrical power is problematic. 

The added steps will increase the overall turn-around time for these procedures, but the potential identification of previously undetectable substances is worth the extra hour or so. 

Tills book has been written with two principal objectives in mind. First, to prompt analysts to think about their problems, and second, to review objectively how to solve them. The author has drawn on his experience to open up the subject to readers. If his examples have a specific a pphcation for you, that is a welcome bonus. If they simply force you to review the possibilities of automation, the author will have made a contribution to ensuring a real and definable analytical service providing unbiased, quality data in a reahstic turn-around time. 

Cycle time is defined as the time between the test request and the availability of data to the submitter. During lead optimization, short turn-around times are critical as this might determine the number of optimization cycles (or number of MedChem decisions) per time unit. A good practice is a one week turn-around time for primary assays, two weeks for follow-up (secondary) assays and two or three weeks for hypothesis-based studies (tertiary assays). 

Fig. 21. Detrimental ion distributions (A) kinetic energy (B) spatial (C) time (D) turn-around time.

Associated with the level of detail in a model, the costs of development and use vary considerably among models. Some models, usually those attempting to provide extremely detailed results, may be developed over periods of ten years or more at a multi-million dollar cost. Other models, usually providing less detailed results, have been developed in a period of a few months at a cost of several thousand dollars. The cost of model use, in terms of computer time and expense, also varies considerably among models. Model runs may take a few hours in turn-around time and cost tens of dollars, or turn-around and analysis time may be several weeks and cost hundreds to thousands of dollars. As with development costs, the costs of model use generally vary with the level of detail. As with the level of detail, the less costly models are best used to identify major trends, which can (in terms of time and cost) then be examined in additional detail by the more expensive models. 

Since both methods yield comparable results, which method should a laboratory use for firearms discharge residue detection Three factors must be kept in mind cost, turn-around-time and personnel requirements. 

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