Sample Incubation

In the original proposal [58], three pumps with intermittent stop /go actions were used, and the feasibility of replacing the reactor Rc2 by a mixing chamber was discussed. Further, use of a single commutator to implement the innovation was demonstrated [60]. Another possibility is to exploit discretely operated pumps and valves [61]. With multicommutation facilities, implementation of the zone splitting strategy is easily accomplished [62]. 

This strategy is more easily implemented in a sequential injection system [63]. To this end, only one bi-directional pump is required (Fig. 7.6, lower). The sample is aspirated towards the holding coil Rq and, after flow reversal, directed towards the diluting coil Rc2 and then to waste. After the tsp pre-defined time interval, when most of the sample zone has gone to waste, the flow is reversed and the selected sample portion is again aspirated towards the holding coil Rq. The total aspirated volume should be lower than the inner volume of Rq in order to avoid aspiration of air. Sequential aspirations of the other solutions involved and further sample handling are accomplished as in an ordinary sequential injection system. 

Zone splitting is a simple and efficient strategy for attaining high (and variable) degrees of sample dilution, as demonstrated by applications listed in Table 7.2. 

The sample residence time in the flow manifold, often associated with the expression sample incubation time, is an important parameter in flow-based analytical procedures involving relatively slow chemical reactions and/or physicochemical processes, e.g., dialysis, gas diffusion or liquid—liquid extraction. This parameter may become a limiting factor in the system design, especially if sensitivity is critical. Moreover, the susceptibility to biased results is less pronounced when the chemical reactions and /or the involved physico-chemical processes tend towards completion. Fig. 1.4 refers to a hypothetical situation where biased results are obtained when chemical equilibrium is not reached. 

Regarding unsegmented flow analysis, zone stopping and zone trapping are efficient strategies for increasing the mean sample residence time. 

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Figure C 1.5.6. Single Ag nanoparticles imaged with evanescent-wave excitation. (A) Unfiltered photograph showing scattered laser light (514.5 nm) from Ag particles immobilized on a polylysine-coated surface. (B) Bandpass filtered (540-580 nm) photograph taken from a blank Ag colloid sample incubated witli 1 mM NaCl and...

Blood Acidification of sample incubation with chloramine-T in sealed vial Headspace GC/ECD 100 pg/L No data Odoul et al. 1994... 

Sample incubated with glucuronidase and sulfatase at pFl 5 and 37 C, FIjSCh added and steam distilled (total phenol) and analyzed FlPLC-electrochemical detector 2 ng/ injection 95-107% Schaltenbrand and Coburn 1985... 

Homogenization with HjO, glutathione, EDTA, citrate buffer, papain and takadiastase (for high starch samples) incubation over night filtration... 

An on line dialysis flow system coupled to ICP-MS (VG Plasma Quad PQII, Thermo Elemental, Winsford, Chaeshire, UK) has been employed to determine trace elements in serum samples by IDMS. Isotope dilution was performed on samples incubated with enriched 65Cu, 66Zn, 77Se and 206Pb for 24 h at 36 °C prior to dialysis to quantify total element concentrations.60... 

A summary of our most recent studies on biologically mediated decay is shown in Figure 5. In situ H202 decay was determined by using the natural logarithm of the nighttime areal concentration plotted versus time. The decay rate constant was taken as the slope of the line. Decay rate constants calculated using in situ values were similar to water samples incubated in bottles kept in the dark in the laboratory. The decay rate constants seemed to correlate with bacteria numbers. 

NOTE Read samples within 10 min, as samples continue to develop color. Samples incubated longer than 60 min should be discarded. 

Plasma was separated from heparinized blood samples, ahquoted and stored at — 80°C. All samples were then analyzed simultaneously with identical hatches of antibodies and other reagents. ELISAs for the detection of sICAM-1, sE-selectin and IL-12 were performed with ELI-Pairs (Diaclone, France distributed by Holzel, Germany). 96-well Maxisorp plates (Nunc) were coated overnight with capture antibodies at 4°C. After 1 h sample incubation, detection was performed with biotinylated anti-ICAM-1, anti-sE-selectin or anti IL-12 detection antibodies followed by streptavidin-horse raddish peroxidase and a TMB color reaction. Light absorption was detected with a Spectra ELISA reader at 450 nm. 

It must be noted that for concentrations in the high pM or in the nM range, only few loadings would be necessary, thereby shortening the assay time. For assays requiring numerous steps as in the present interleukin IB tests, the time-to-result can indeed be easily decreased from 20 min in the present example to 15 min with 30 sample loadings and even —3.5 min for single sample incubations. 

Figure 9.4. Treatment of picloram desorption data as a simple first-order reversible process for sample incubated 100 days in Kawkawlin soil. Plotted line is computed from model. [From McCall and Agin (1985), with permission.]...

Add 50 jxL of MNNG stock solution to 1.95 mL of the cell suspension, and 50 jxL of Buffer 1 only to a control sample. Incubate all the samples at 37°C, with shaking, for different times. 

As shown in Figure 7.3 (see color section), the morphologies observed in a sample incubated with acridine orange and ethidium bromide allow the identification of four levels of cell viability, as described below ... 

After cooling to room temperature, add 5 yu.L of 100 mM iodoacetamide to each sample. Incubate for 15 min. 

In Chapter 4, data are presented which demonstrate that desorption of inorganics from clay mineral surfaces exhibits hysteresis. Similarly, in the case of desorption of organics, hysteresis appears to play a major role. For example, the data in Figure 8.20 show that the adsorption isotherm of 2.4.5-T is not similar to its adsorption isotherm and this difference increases as the soil sample incubation period increases. The data in Figure 8.21 also show that the kinetics of atrazine adsorption differs greatly from that of atrazine desorption. There are many potential causes for this difference, including particle diffusion effects and chemical thermodynamic effects. 

Figure 9.31 Chromatograms obtained from various samples incubated with (upper diagram) or without (lower diagram) Hip-His-Leu (HHL). (A) Standard mixture of 2.7 nmol His-Leu, 2.7 nmol hippuric acid, and 100 nmol Hip-His-Leu. (B) A 50 /xL aliquot of serum or (C) whole blood was incubated with or without 5 mM Hip-His-Leu. After 30 minutes, 0.7S mL of 3% m-phosphoric acid was added and centrifuged. (D) Lung or (E) kidney was homogenized in S volumes of chilled Tris-HCl buffer containing 0.5% Nonidet-P40, and centrifuged. The supernatant was incubated with or without 5 mAf Hip-His-Leu. In the case of lung, the supernatant was diluted 20 times with the buffer prior to incubation with Hip-His-Leu. Peaks 1, His-Leu 2, hippuric acid 3, Hip-His-Leu. (From Horiuchi et al., 1982.)...

Confirmed test— A further test for the cohform group proceeding from the presumptive test where evolution of gases within 24 to 48 + 3 hours in the presence of a brilliant green lactose bile broth from samples incubated at 35 + 0.5°C indicates a positive test. 

Precipitation of the cleavage products was accomplished by resuspending the dried samples in 50 pi 0.1% TFA. 450 pi of cold acetone was then added and the samples incubated at -20° C for 3 hours then centrifuged and the supernatant removed The pellets were redissolved in 0.1% TFA/acetonitrile and lyophilized prior to dissolution in sample buffer. 

Figure 3. Effect of DFP Concentration on CMV Protease Activity. In order to confine DIP incorporation to the active site of the protease, 200 mM samples of CMV protease were incubated for 2 hours with the indicated concentrations of DFP. A desMet-protease species with 2 DIP groups incorporated (28,233) is apparent in samples incubated with 1.26, 1.63 and 2.07 mM DFP. But even in the sample incubated with 2.07 mM DFP, the diphosphorylated species represents considerably less than 5% of the inactivated desMet-protease. A liberal estimate of the residual unmodified protease present in the samples incubated with 1.63 and 2.07 mM DFP is also less than 2%. DIP-full length protease is present in all DIT inactivated samples, but diphosphorylated full length protease is not detectable even at 2.07 mM DFP. The relative activities of the control and inactivated samples are presented in Figure 4. 

A protease species with 2 DIP groups incorporated is also apparent in samples incubated with 1.26, 1.63 and 2.07 mM DI, although even in the sample incubated with 2.07 mM DFP, the diphosphorylated components represent less than 5% of the inactivated protease. Based on Figure 3, the... 

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