Sample solution consumption

The nebulizer is mounted in the spray-chamber burner assembly, as shown for the nitrous oxide or air-acetylene burner system (Fig. 32). Air or nitrous oxide are fed to the mixing chamber through the nebulizer. The combustion gas is fed directly to the burner. A self-aspirating concentric nebulizer is often used, but other types, including the Babington and cross-flow types (Section 21.4.1) are also applied. Nebulizers may be made of glass, corrosion-resistant metals such as Pt-Ir. or plastics such as Ryton. Sample solution consumption usually amounts to ca. S miymin in the case of gas flows of 1 -5 L/min. 

The total consumption type of burner consists of three concentric tubes as shown in Fig. 21.5. The sample solution is carried by a fine capillary tube A directly into the flame. The fuel gas and the oxidant gas are carried along separate tubes so that they only mix at the tip of the burner. Since all the liquid sample which is aspirated by the capillary tube reaches the flame, it would appear that this type of burner should be more efficient that the pre-mix type of burner. However, the total consumption burner gives a flame of relatively short path length, and hence such burners are predominantly used for flame emission studies. This type of burner has the advantages that (1) it is simple to manufacture, (2) it allows a totally representative sample to reach the flame, and (3) it is free from explosion hazards arising from unbumt gas mixtures. Its disadvantages are that (1) the aspiration rate varies with different solvents, and (2) there is a tendency for incrustations to form at the tip of the burner which can lead to variations in the signal recorded. 

A = alkali solution consumption per gram of the whole sample,... 

The dominating working mode of polymer HPLC is the straight elution of small volume of sample solution along the column. There were attempts to introduce the differential and vacancy procedures in SEC. In both cases, the eluent was a diluted solution of the polymer while either a proper sample or a reference polymer [314] or even pure eluent [315] was injected. A broader application of these proposals was hindered by both the high eluent viscosity and the large sample consumption. Moreover, the dependences of log M vs. Vr (Equation 16.12) obtained by the conventional and the differential/vacancy methods are mutually shifted. The deviation between both dependences was attributed to the nonequilibrium situation in the vacancy polymer HPLC [316],... 

Procedure Pre-equilibrate the Substrate Solution, the Sodium Deoxycholate Solution, and about 50 mL of water to 40° in the water bath. Transfer 10 mL of the Substrate Solution to the thermostated titration vessel. Add 5 mL of the Sodium Deoxycholate Solution and 10 mL of deionized water. Blanket the cell with nitrogen and equilibrate for approximately 5 min. Using the Automatic Titrator filled with 0.1 N Sodium Hydroxide Solution, adjust the pH of the solution to 8.0 0.05. Monitor the consumption (if any) of sodium hydroxide for 5 min as a blank. Refill the Automatic Titrator. Add 0.1 mL of Sample Solution containing between 1 and 8 units of activity and start the Automatic Titrator. Record the sodium hydroxide consumption for at least 5 min. 

Because standard samples contain only a limited number of elements whose concentration lies in the range of this method, we would determine, for example, 9 trace elements in 15 attempts, 3 times each, involving a consumption of 150pi of sample solution (Table 3). The pairs Cu 324.7 nm/ Cr357.9n, Ni 314.5nm/Mn 279.5nm and Zn 213.9nm/Co 240.7nm were determined with the air/acetylene flame, and A1 309.3 nm/Mo 313.3 nm and Mg 285.2 nm were determined with the nitrous oxide/acetylene flame. 

The consumption of sample solution is very small, which is an advantage espedaUy when expensive reference substances are used. 

Both types have been investigated in detail (Olson et al., 1977 Greenfield et al., 1976, 1977 WInefordner and Latz, 1961 Schramel and Ovcar-Pavlu, 1979). In principle, using a pneumatic nebulizer, one should apply a peristaltic pump for the transport of the sample solution. Such a pump reduces the sample consumption significantly In comparison to a free sucking system (appr. 1 mUmin as against appr. 5 mU/min) and reduces the influence of viscosity and density of the sample solution to the droplet-size which will be produced by the system due to the amount of solution forced through the capillary. Therefore an important influence on the sensitivity (expressed as the slope of the calibration curve) can be nearly eliminated. 

An FIA system is especially useful in the analysis of solutions containing high levels of solids such as saturated salt solutions or dissolved fusion mixtures. The burner slot or nebulizer will not become blocked since the system is continuously and thoroughly rinsed with the carrier stream after each sample measurement. The FIA system requires less than 400 /zl of sample solution, which is much less than with continuous aspiration. Thus, FIA-FAAS is the preferred technique when only small sample amounts are available. Low sample consumption is also beneficial for routine analysis, since with fully automated sequential multi-element analysis more determinations can be performed with a given sample volume. 

Conduct a blank test in the same way using 100 ml of distilled water instead of the sample. Any consumption of sodium thiosulphate solution... 

The positive effects include a reduction in plate height (mainly via reduction in the A-term, multipath dispersion), reduction in chromatographic dilution and thus increased detection sensitivity, and reduction in volume flow rate and thus in solvent consumption. However, offsetting disadvantages include limitations on the volume of sample solution and the amount of analyte that can be injected without overloading the column, and the meticulous attention that is required to reduce the extra-column dead volume (injectors, detectors etc.) to avoid excessive band broadening. As noted above, these columns do not appear to have been used in vahdated quantitative methods. 

A rapid electrochemical microbioassay for vitamin B12 was reported in 1987 using Escherichia coli 215 and an oxygen electrode (Karube et al. 1987). The sample solution is injected into the microbial electrode system increased consumption of oxygen by the microorganisms leads to a decrease in current which is directly proportional to amount of vitamin B12. 

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