Screen sample

Radioactivity in environmental waters can originate from both natural and artificial sources. The natural or background radioactivity usuaUy amounts to <100 mBq/L. The development of the nuclear power industry as weU as other industrial and medical uses of radioisotopes (qv) necessitates the deterrnination of gross alpha and beta activity of some water samples. These measurements are relatively inexpensive and are useful for screening samples. The gross alpha or beta activity of an acidified sample is deterrnined after an appropriate volume is evaporated to near dryness, transferred to a flat sample-mounting dish, and evaporated to dryness in an oven at 103—105°C. The amount of original sample taken depends on the amount of residue needed to provide measurable alpha or beta activity. 

The synthesis of small, focused arrays based on some of the hits may help define a series if the desired compounds are not available through substructure or similarity searching. The purpose of this type of array is not to optimize a hit but to help prioritize a series for further synthetic work. Inclusion of the original hit in the array is useful for confirmation of activity, particularly when supplies are limited or the screening sample was of low purity. 

In the new vision, assay cycle time is dramatically reduced and the criteria used to measure assay acceptability are matched to sample type. Early screening samples may be assayed using simple methods and minimum numbers of standards. Samples from early preclinical PK studies in rats and other species may require additional standards. Finally, for PK studies performed in the lead characterization phase, one might add quality control (QC) samples. One set of rules for non-GLP assays has been codified in a recent publication.16 These rules make it possible to match the assay cycle time with the in-life cycle time in order to minimize the total discovery cycle time. 

The chemical attributes of a lead series include knowing the chemical structure and purity of the hit(s). There are often cases where the activity of a screening sample cannot be confirmed when the compound is resynthesized and this can sometimes be traced to impurities in the original sample, and there are cases where the structure of the hit was not assigned correctly. In order to justify the resources required for lead optimization, it is important to know the structure of the lead. Synthetic tractability can... 

Cluster analysis Is used to determine the particle types that occur in an aerosol. These types are used to classify the particles in samples collected from various locations and sampling periods. The results of the sample classifications, together with meteorological data and bulk analytical data from methods such as instrunental neutron activation analysis (INAA). are used to study emission patterns and to screen samples for further study. The classification results are used in factor analysis to characterize spatial and temporal structure and to aid in source attribution. The classification results are also used in mass balance comparisons between ASEM and bulk chemical analyses. Such comparisons allow the combined use of the detailed characterizations of the individual-particle analyses and the trace-element capability of bulk analytical methods. 

The NMR screening samples can be prepared in an automated fashion with a programmable platform such as Tecan (by Tecan) and samples can be automatically loaded into the spectrometer by using a Sample Rail (by Bruker Biospin). This allows for maximum spectrometer time and the sample is always freshly prepared prior to data acquisition. 

Screening - [SAMPLING] (Vol 21) - [SEPARATION - SIZE SEPARATION] (Vol 21) -m paper recycling [RECYCLING - PAPER] (Vol 21)... 

Relatively narrow screening sampling is necessary for the first characterization of the heavy metal content of an area of soil. 

---