Sample-reagent mixing

Kinetic methods are usually associated with two types of reactions, namely slow reactions (those with half-lives of 10 s or longer) and fast reactions (those reaching half-completion in less than 10 s), which dictate both the sample-reagent mixing procedure and the instrumentation to be used. 

Table 5.1 summarizes a classification of the FI applications as a function of the D value. In some FI applications, the analyte is preconcentrated and D becomes lower than 1. Meanwhile, in other cases, larger values of D are produced, as a result of small sample volume injection or as a consequence of efficient on-line sample-reagent mixing, as described earlier. 

Add 50 pi of Ellman s reagent to each standard and sample tube. Mix well. 

Figure 5 Basic steps in a CL process (a) the sample and reagent(s) are introduced in the reaction cell and the final reagent is injected to initiate the CL emission, then light is monitored by the detector (b) curve showing CL intensity as a function of time after reagent mixing to initiate the reaction (the decay of the signal is due to the consumption of reagents and changes in the CL quantum efficiency with time) (c) a calibration function is established in relation to increasing analyte concentrations.

Figure 12.6 illustrates the outline of such an analysis. An automatic pipette extracts a preset volume of the liquid sample (or solution) from a cup presented to it on a turntable. The measured sample is mixed with the reagents in the appropriate proportions, and propelled through the instrument by the peristaltic proportioning pump. This pump operates by means of moving bars, attached to a chain drive, which sequentially compress the plastic sample and reagent tubes to drive the liquids forward through the instrument. The incorporation of a succession of air bubbles at... 

The pump provides constant flow and no compressible air segments are present in the system. As a result the residence time of the sample in the system is absolutely constant. As it moves towards the detector the sample is mixed with both carrier and reagent. The degree of dispersion (or dilution) of the sample can be controlled by varying a number of factors, such as sample volume, length and diameter of mixing coils and flow rates. 

Water To 100 mL sample, add 2 mL glycine solution and mix. In a separate flask, place 5 mL buffer reagent and /V,/V-diethyl-p-phenylenediamine indicator solution and mix. Add 200 mg EDTA, disodium salt, and then add glycine-treated sample and mix. UVA/IS spectrometry >0.1 mg/L No data APHA1998 (Method 4500-CL02-D)... 

Lei et al. reported a method for the indirect determination of trace amounts of procaine in human serum by atomic absorption spectrophotometry [54], The sample was mixed with HCIO4, heated at 85°C for 30 minutes, diluted to a known volume with water, and centrifuged. 1 mL of the supernatant solution was buffered with 0.1 M sodium acetate-acetic acid to pH 3.86, and mixed with 0.2 M Zn(SCN)j reagent to a final concentration of 0.1 M. After dilution to 50 mL with water, the solution was shaken for 1 minute with 10 mL of 1,2-dichloroethane, whereupon the zinc extracted into the organic phase was determined by air-acetylene flame atomic absorption spectrometry for the indirect determination of procaine. The detection limit was found to be 0.1 pg/g, with a recovery of 89-98% and a coefficient of variation (n = 10) equal to 3.2%. 

Add together 50 pi of either the liver or fibroblast sample (prepared as described above) and 100 pi reagent mix. Incubate and continue as with blood samples. 

Boil 100 pi of either sample (liver or fibroblast) for 2 min, put on ice, then add 200 pi of reagent mix. Continue as for the blood sample blanks. 

XIV. Treatment with Franchimont Reagent. Mix in a test tube ca O.lg of the sample with ca 5ml of glac AcOH and add 2 drops of dimethyl-a -naphthylamine. Add ca 0.2g of Zn dust and allow to stand for 2 mins. A brn-red color confirms the presence of DlNA(See also Chart B)... 

Generally, duplicate samples are mixed at the same time to speed up the process. The bottles containing the TCA reagent and distilled water are placed in plastic buckets containing ice, and a 50-ml Brinkmann dispensette is connected to each. 

When the FC analysis is carried out manually, there are limits to the number of samples that can be handled at once because of the need to time the reagent mixing and spectral readings. In the author s laboratory, single analysts can run 20 samples per day, divided into 2 sets. Since each sample is run in duplicate and 4 standards are included in each run, 50 individual results are generated in a day. 

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