Gradient techniques in flow injection analysis

Peak width and reagent dispersion in flow injection analysis

“…This situation is possibly covered better by the "one-tank" model but examination of their experimental results shows the rise time to occupy a significant proportion of the total peak time, at variance with the prediction of an infinitely fast rise time. This paper [6] also corrects an error in the equivalence condition made in the earlier paper [2], but perpetuates the hidden approximation in deriving the equation for the single-line mani fold.…”

“…It is proposed here that all methods encompassed by the terminology above be known as "peak width" methods and that these form a subset of all "time-based" methods in f.i.a. This latter set would also include methods based on "electronic dilu tion" [6], "gradient calibration" (both decreasing [6] and increasing [7] ), "stopped flow" [8], "gradient scanning" [9] and "zone sampling" [10] amongst others.…”

“…Two groups of workers have previously derived peak-width equations, several of which are inaccurate. Ruzicka and co-workers [2,6] assumed that the injected sample volume was instantly dis persed throughout the mixing chamber and then washed out. This is the tanks-in-series model for dispersion behaviour [11] with the number of tanks reduced to one and does not correspond to the situation, often adopted in practice, in which a real mixing chamber is introduced into the manifold and the sample slug flows into the tank.…”

“…It is also possible in practice for the in jected volume to be larger than the tank volume, a situation not covered by this version of the tanks-in-series model. Olsen et al [6] considered that, for a system without a real mixing chamber, the dispersion produced was equiva lent to wash out from a tank comprising the reactor volume plus half the injected volume. This situation is possibly covered better by the "one-tank" model but examination of their experimental results shows the rise time to occupy a significant proportion of the total peak time, at variance with the prediction of an infinitely fast rise time.…”

Construction and evaluation of an automated flow injection‐stopped flowanalyser for multipoint reaction rate spectrophotometric methods. Determinationof ammonia nitrogen, creatinine and phosphate

“…FI [6,7] and boron in plants [8], and to the simultaneous determinations of magnesium and calcium [9]. This technique, in combination with the merging zones principle [5] [5] and urea [11], ethanol in blood and spirits [12], glycerol and triglycerides [13], and the activity of the enzymes galactic dehydrogenase [10], alkaline phosphatase, lipase, acetylcholinesterase and chymothripsin in plasma and serum [14], have been determined. FI-SF in conjunction with catalytic reactions has been used in the determination of various ions, such as Co(II) [15], cyanide [16], Cu(II) in foodstuffs [17], and Cu(II) and Hg(II) simultaneously [18].…”