Enhanced sample throughput

Because of the pressing contemporary need to assess an ever-growing number of chemicals and complex environmental samples, the development and use of small-scale toxicity tests (also called micro-scale toxicity tests or microbiotests ) have increased because of their attractive features. Simply defined as a test involving the exposure of a unicellular or small multicellular organism to a liquid or solid sample in order to measure a specific effect , small-scale tests are generally simple to execute and characterized by traits which can include small sample volume requirements, rapid turnaround time to results, enhanced sample throughput and hence cost-effectiveness (Blaise et al., 1998a). 

For diagnostic detection of BChE adducts of common G- and V-type nerve agents, enhanced sample throughput was achieved by automated processes in 96-well plate format, extracting plasma by inunimomagnetic separation (Knaack et al., 2012). An alternative method, based on the principle of a sandwich enzyme-linked immunosorbent assay (ELISA), was presented by Wang et al. (2011) to determine OP adducts in complete BChE. 

Packed column SFC has also been applied to preparative-scale separations [42], In comparison to preparative LC, SFC offers reduced solvent consumption and easier product recovery [43]. Whatley [44] described the preparative-scale resolution of potassium channel blockers. Increased resolution in SFC improved peak symmetry and allowed higher sample throughput when compared to LC. The enhanced resolution obtained in SFC also increases the enantiomeric purity of the fractions collected. Currently, the major obstacle to widespread use of preparative SFC has been the cost and complexity of the instrumentation. 

In some cases, ultrasonic nebulization or preconcentration is used to enhance detection limits. As, Se, and Sb were measured in cloud water detection limits were 20, 100, and 20 pg/mL, respectively, using pneumatic nebulization and four to five times lower using ultrasonic nebulization [311]. In another study [312], activated charcoal from a 1-L sample volume was used to preconcentrate Pd and Pt in fresh waters. Detection limits were 0.3-0.8 ng/L. An automated online preconcentration system based on a cationic resin (AG50W-X8) was used to measure Cd, Pb, Ni, Cu, and Zn. A preconcentration factor of 30 was obtained even with a sample throughput of 20 samples per hour [313]. 

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. 

ICAT labelling kits are commercially available. In a modified procedure, two separate measurement steps are performed to enhance the sample throughput [84]. In the first step, LC-TOF-MS is applied for quantification and triggering of collection fractions containing up- or down-regulated peptides. In the second step, the fractions are identified via direct-infusion nano-ESI-Q-TOF-MS. 

Automated Procedures At least four commercial automated instruments exist which will concentrate headspace volatiles on adsorbents and thermally desorb them into a gas chromatograph. Times, temperatures, and gas flow rates are accurately controlled. Manual handling steps which can introduce variability are eliminated. Since these instruments are automated, sample throughput is enhanced they can be interfaced to high resolution gas chromatographs. 

Parallel analysis is one of the most effective ways to enhance laboratory productivity. A typical parallel analysis HPLC system consists of multiple pumps or a multi-channel pumping system, a multi-probe autosampler capable of four or eight simultaneous parallel injections from 96-well microplates, and a multiplexed UV detector and/or MS. This generic approach allows a 4 to 8 fold increase of sample throughput while maintaining the traditional performance and convenience of HPLC. This technology can potentially be extended to a 96-channel analysis system. 

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