Parallel sampling

ParaUebismus, m. parallelism, -itat, /. parallelism. -probe, /. parallel sample or test, -schsltung, /. (Elec.) connection in parallel. parallelsteng(e)lig, a. (Cryst.) parallel-columnar,... 

Each serie of measurements consisted of two parallel samples with counting during and after sampling, one with the screen diffusion battery and the second as the reference sample, so that the fractional free radon daughters could be calculated. The radon daughters are collected on a membrane filter (filter diameter 25 mm, pore diameter 1.2 ym) and the decays of Po-218 and Po-214 are counted by means of alpha spectrometry with a surface barrier detector (area 300 mn ). 

The issue is how LC/MS analysis—by nature a serial procedure—can meet the demands of parallelized sample generation and preparation. This can be achieved by speeding up the serial LC/MS, parallelizing parts of the analysis, or both. Several aspects of optimization should be considered ... 

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. 

As described above, the combination of EPR and Mossbauer spectroscopies, when applied to carefully prepared parallel samples, enables a detailed characterization of all the redox states of the clusters present in the enzyme. Once the characteristic spectroscopic properties of each cluster are identified, the determination of their midpoint redox potentials is an easy task. Plots of relative amounts of each species (or some characteristic intensive property) as a function of the potential can be fitted to Nernst equations. In the case of the D. gigas hydrogenase it was determined that those midpoint redox potentials (at pFi 7.0) were —70 mV for the [3Fe-4S] [3Fe-4S]° and —290 and —340mV for each of the [4Fe-4S]> [4Fe-4S] transitions. 

Figure 3.2 Correct and incorrect increment delimitation in process sampling. Generic illustration (e.g. of a conveyor belt). The three examples to the left are all delineated correctly with parallel sampling implement boundaries, while the remaining three cannot deliver a correct (nonbiased) transverse cut of the l-D stream. Repeated sampling results in unbalanced transverse proportions of the flux of matter, the effect of which is IDE and IME.

The tests with Daphnia magna were performed in 50 mL beakers. They were filled with 20 mL test solution and five animals (aged 6-24 hours) were added to each solution. For each dilution of the extract 2x5 daphnids were applied in parallel samples. The daphnids were incubated without feeding. After 96 hours the number of immobilized specimens was determined visually. 

A sampling system designed to reduce artifact problems was employed by Liang and co-workers (1997) in an experimental chamber study of the gas-particle partitioning of several PAHs (and //-alkanes) on three types of model aerosols and ambient urban particulate matter. The system consisted of a dual glass fiber filter system as described by Hart and Pankow (1994), followed by two parallel sampling trains for trapping... 

Denuders have been used in several different ways. One is to extract the walls of the denuder and measure the adsorbed gas directly by ion chromatography. Denuders have also been used as difference denuders. For example, in nitric acid measurements, the combination of gas-phase HNO-, and particle nitrate has been measured using a nylon filter or Teflon-nylon filter combination in one sampling train. In a parallel sampling train, particulate nitrate alone is measured by first passing the airstream through a denuder to re-... 

We do not need to know the set of normalization constants w to implement serial sampling [Eq. (25)] since each plays only the role of a normalization constant for a sampling distribution, which the MC framework does not require. Nor do we need these constants in implementing parallel sampling [Eq. (26)] since in this case they feature (through their product) only in the one overall normalization constant for the sampling distribution. But Eq. (28) is different. Writing it out more explicitly,... 

The time required per analysis—in the 10-30 min range—is approximately the same as for static HS-GC but does not allow parallel sample preparation of multiple samples, since the trapped analytes have to be injected directly into the GC.96... 

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