Sampling, rapid

The statistics of the detected photon bursts from a dilute sample of cliromophores can be used to count, and to some degree characterize, individual molecules passing tlirough the illumination and detection volume. This can be achieved either by flowing the sample rapidly through a narrow fluid stream that intersects the focused excitation beam or by allowing individual cliromophores to diffuse into and out of the beam. If the sample is sufficiently dilute that... 

There is the microtoming optical analysis test. In this procedure thin slices (under 30 tixri) of the plastics are cut from the product at any level and microscopically examined under polarized light transmitted through the sample. Rapid quality and failure analysis examination occurs by this technique. This technique has been used for many years in biological studies and by metallurgists to determine flaws, physical and mechanical properties. Examination can be related to stress patterns, mechanical properties, etc. 

Small samples rapidly heated in sealed tubes to around 100°C exploded. 

For discovery PK samples, rapid method development is required. For HPLC/MS/MS assays, method development can be achieved within 2 hr if no unusual problems are encountered. Xu et al.101 described a process for rapid method development as part of the discovery PK paradigm. As shown in Figure 7.4, the systematic process is based on using protein precipitation as the sample clean-up step and generic HPLC conditions for the HPLC/MS/MS assay. 

Jemal M., Xia Y., and Whigan D.B., 1998. The use of high-flow high performance liquid chromatography coupled with positive and negative ion electrospray tandem mass spectrometry for quantitative bioanalysis via direct injection of the plasma/serum samples. Rapid Commun Mass Spectrom 12 1389. 

Cristoni S, Bernardi LR, Gerthoux P, Gonella E, MocareUi P. 2004. Surface-activated chemical ionization ion trap mass spectrometry in the analysis of amphetamines in diluted urine samples. Rapid Commun Mass Spectrom 18 1847. 

Korfmacher, W. A. Veals, J. Dunn-Meynell, K. Zhang, X. Tucker, G. et al. Demonstration of the capabilities of a parallel high performance liquid chromatography tandem mass spectrometry system for use in the analysis of drug discovery plasma samples. Rapid Commun Mass Spectrom 1999, 13, 1991-1998. 

Shou, W. Z. Naidong, W. Postcolumn infusion study of the dosing vehicle effect in the liquid chromatography/tandem mass spectrometric analysis of discovery pharmacokinetic samples. Rapid Commun Mass Spectrom 2003, 17, 589-597. 

DC Gale, RD Smith. Small-volume and low-flow-rate electrospray ionization-mass spectrometry of aqueous samples. Rapid Commun Mass Spectrom 7 1017-1021, 1993. 

Cool the sample rapidly to about 40°C below Tm. [For linear polyethylene), this temperature would be 95°C.]... 

Fig. 3. Magic angle spinning and its effect on anisotropic interactions. The dashed vector, denoting one particular dipolar interaction, or some other measure of molecular orientation, is shown on the right in terms of the geometry of sample spinning. By rotating the sample rapidly about an appropriate axis, the anisotropy or broadening experienced by the nucleus can be reduced to zero.

Methods for Determining Biomarkers of Exposure and Effect. Section 2.6.1 reported on biomarkers used to identify or quantify exposure to diazinon. Some methods for the detection of the parent compound in biological samples were described above. The parent chemical is quickly metabolized so the determination of metabolites can also serve as biomarkers of exposure. The most specific biomarkers will be those metabolites related to 2-isopropyl-6-methyl-4-hydroxypyrimidine. A method for this compound and 2-(r-hydroxy-l -methyl)-ethyl-6-methyl-4-hydroxypyrimidine in dog urine has been described by Lawrence and Iverson (1975) with reported sensitivities in the sub-ppm range. Other metabolites most commonly detected are 0,0-diethylphosphate and 0,0-diethylphosphorothioate, although these compounds are not specific for diazinon as they also arise from other diethylphosphates and phosphorothioates (Drevenkar et al. 1993 Kudzin et al. 1991 Mount 1984 Reid and Watts 1981 Vasilic et al. 1993). Another less specific marker of exposure is erythrocyte acetyl cholinesterase, an enzyme inhibited by insecticidal organophosphorus compounds (see Chapter 2). Methods for the diazinon-specific hydroxypyrimidines should be updated and validated for human samples. Rapid, simple, and specific methods should be sought to make assays readily available to the clinician. Studies that relate the exposure concentration of diazinon to the concentrations of these specific biomarkers in blood or urine would provide a basis for the interpretation of such biomarker data. 

Add 3 drops of bromocresol green indicator (Table 11-4) and titrate one sample rapidly to a green color to find the approximate end point. 

The counting of tritium in water is a special problem about which much has been written. Current methods for assay of tritium in water have a range of 0.1 -5000 TU, where a tritium unit (TU) has the value of 7.2 dpm/L. The most desirable feature of a tritium measuring system is that it be capable of measuring a large number of samples rapidly, simply, and cheaply as possible with an uncertainty of +10% or better. It is generally more important to assay 100 samples with an uncertainty of +10% than to assay 10 samples with an uncertainty of +3%. 

The remote nature ofthe interaction between microwaves and the sample means that when the power is switched off the sample rapidly cools. Consequently, it is possible to use the microwave applicator in a more flexible fashion than a normal heating furnace. This becomes an important consideration in the economics of ceramics processing, since the ability to use the furnace flexibly for several processes combined with the shorter reaction times can lead to a more economic use of plant than the conventional thermal processing. 

Since the metathetical reaction between the fluoride and tungstate will also proceed in the solid state (although at a much slower rate), it is desirable to have the reaction mixture attain the liquid state in as short a time as possible. If a furnace capable of attaining 1300-1400°C. in a few hours is not available, the following procedure may be employed. The furnace (such as the Harper furnace model, HOU 6610 M 30) is preheated to 1300°C., the furnace chamber opened, the sample rapidly placed inside, the furnace chamber closed, and the temperature raised to 1400°C. 

Vetter W, Alder L, Palavinskas R (1999) Mass Spectrometric Characterization of Ql, a C9H3CI7N2 Contaminant in Environmental Samples. Rapid Commun Mass Spectrom 13 2118... 

Wang, G., Hsieh, Y., Cui, X., Cheng, K. C., and Korfmacher, W. A. (2006). Ultra-performance liquid chromatography/tandem mass spectrometric determination of testosterone and its metabolites in in vitro samples. Rapid Commun. Mass Spectrom. 20 2215-2221. 

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