Tracer spike

Compared to perfect operation, the space time is smaller and the tracer spike will occur before T for perfect operation. 

Adding a tracer spike to a batch reactor produces a step increase in the tracer concentration in the reactor and the concentration remains constant thereafter. No tracer is discharged from the reactor and no tracer is generated in the reactor. 

Hot spring pools are usually well stirred by thermal convection and rising gas bubbles, so they can be modeled as ideal batch reactors and the volume of water in the pool can be determined using a tracer spike. 

Tracer spike addition to a mixed flow reactor... 

Adding a tracer spike to an ideal mixed flow reactor produces a step increase in the tracer concentration just as in the batch reactor case, but in this case the tracer s concentration declines over time as the reactor s effluent carries it away. If the amount of solution in the reactor remains constant and no more tracer is added by the feed solution or by generation in the reactor, the continuity equation simplifies to make the rate of accumulation equal to the rate of loss by the effluent flow. 

This case is very similar to the previously discussed case for the injection of a tracer spike. The time needed for the first spiked slug to reach the reactor s discharge is found by rearranging Eq. (4.13). 

Conventional applications of IDMS in quantitative elemental analysis usually involve the use of a single isotopically enriched tracer/spike. This is different in metabolic studies. The use of two or more tracers of the same element in parallel permits the use of more refined study designs and methodologies, as discussed later. When two isotopic labels X and Y are used in parallel [9], the tracer to tracee ratio for label Y in the sample can be calculated using... 

The measurement of potential Hg methylation and MeHg demethylation is significantly more complex than the measurement of HgT and MeHg concentrations in ambient samples. Methodological considerations include the maintenance of redox and temperature condition of samples during measurement, an understanding of the time course of both processes, and an understanding of the impact of spike level on the methylation and demethylation rate constants. Measurement of methylation and demethylation also requires the use of a tracer, and the abiUty to measure that trace analytically. 

For precise measurement of isotopic composition by mass spectrometry, it is also common to use either a natural, known isotopic ratio to correct for instrumental mass fractionation (e g., internal normalization) or to add a tracer for this purpose. For example for natural uranium samples, one can use the natural U/ U of 137.88 to correct for fractionation. Alternatively, one can use an added double spike of ratio -unity... 

Isotope dilution measurements using a and/or spike tracer can be performed separately, or combined with the isotopic composition run. Spike tracers can be measured on an ion counting channel, or alternatively, it may be preferable to concentrate the tracer (provided the spike corrections are small) and measure it on a... 

When a 350 ml seawater sample was spiked with 54Mn and taken through the chelation, extraction, and back-extraction procedures, the observed recovery of the radio-tracer was 100.6%. Estimates of detection limits for manganese based on sets of both shipboard and shore laboratory separations are of the order of 0.1 nmol/1. The accuracy of the technique is demonstrated by data from the ICES fifth-round intercalibration exercise for trace metals in seawater [449 ]. 

Once geological samples are dissolved, a mixed Ca- Ca tracer is added to the sample ( Ca/ Ca 1). The isotopic abundances in the mixed sample-tracer solution are illustrated in Figure 1. When the mixed solution has roughly equal amounts of the isotopes Ca, Ca, and Ca, then a near-optimal situation is achieved with regard to the corrections for the presence of the tracer (cf Johnson and Beard 1999 for a detailed analysis of spike-sample ratios). The... 

Using the three measured ratios, Ca/ Ca, Ca/ " Ca and Ca/ " Ca, three unknowns can be solved for the tracer/sample ratio, the mass discrimination, and the sample Ca/ Ca ratio (see also Johnson and Beard 1999 Heuser et al. 2002). Solution of the equations is done iteratively. It is assumed that the isotopic composition of the Ca- Ca tracer is known perfectly, based on a separate measurement of the pure spike solution. Initially it is also assumed that the sample calcium has a normal Ca isotopic composition (equivalent to the isotope ratios listed in Table 1). The Ca/ Ca ratio of the tracer is determined based on the results of the mass spectrometry on the tracer-sample mixture, by calculating the effect of removing the sample Ca. This yields a Ca/ Ca ratio for the tracer, which is in general different from that previously determined for the tracer. This difference is attributed to mass discrimination in the spectrometer ion source and is used to calculate a first approximation to the parameter p which describes the instrumental mass discrimination (see below). The first-approximation p is used to correct the measured isotope ratios for mass discrimination, and then a first-approximation tracer/sample ratio and a first-approximation sample CeJ Ca... 

Bones spiked with tracer dry ashed, Th coprecipitated with Fe-hydrox1de, cleaned up by complexatlon and solvent extracted and electrodeposited. 

For application in the isotope dilution technique and for tracer experiments using isotope enriched spikes, Merck (Darmstadt, Germany) have launched the production of new sets of isotopically enriched materials, such as 53Cr or mCd enriched spike calibration solutions, which were characterized by the Institute for Reference Materials and Measurements (IRMM, Geel, Belgium).52... 

In these types of isotopic analysis, the same compound as that to be measured is used (element or molecule) where one of the atoms in it has been replaced by a radioisotope to allow radioactivity measurements. A small, precisely known quantity of the labelled compound, called the tracer, is added to the sample and, after homogenisation, an aliquot of the spiked sample is isolated by a fractionation technique such as recrystallisation or chromatography. The specific activity of the tracer is measured before and after fractionation. 

Fig. 33.1. Competitive immunoassays for the determination of atrazine in spiked orange juice samples, based on dry-assisted affinity immobilization of the anti-atrazine antibodies (0.5 pg) on ProtA(2%)-GEB. The biosensors were incubated with 0.02 pg of atrazine-HRP tracer. In all cases, n — 3.

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