Reagent solutions concentration

Detection and result The chromatogram was dried in a stream of warm air for 10 min, immersed in the reagent solution for 3 s and then subjected to intense UV radiation (high pressure lamp, A = 365 nm) for up to 10 min. Terephthalic (hRf 0 - 5), pimelic (hRf 55), suberic (hRf 60), sebacic (hRf 65 — 70) and benzoic acids (hRf 70 — 75) together with sorbic, malic, adipic, citric, tartaric, lactic and fumaric acids only exhibited a reaction on silica gel layers at higher concentrations. 4-Hydroxybenzoic, salicylic and acetylsalicylic acids fluoresced light blue after irradiation. The detection limit per chromatogram zone was 0.5 pg for salicylic acid and more than 5 pg for benzoic acid. 

For expressing concentrations of reagents, the molar system is universally applicable, i.e. the number of moles of solute present in 1 L of solution. Concentrations may also be expressed in terms of normality if no ambiguity is likely to arise (see Appendix 17). 

Solutions of cerium(IV) sulphate may be prepared by dissolving cerium(IV) sulphate or the more soluble ammonium cerium(IV) sulphate in dilute (0.5-1.0M) sulphuric add. Ammonium cerium(IV) nitrate may be purchased of analytical grade, and a solution of this in 1M sulphuric add may be used for many of the purposes for which cerium(IV) solutions are employed, but in some cases the presence of nitrate ion is undesirable. The nitrate ion may be removed by evaporating the solid reagent which concentrated sulphuric add, or alternatively a solution of the nitrate may be predpitated with aqueous ammonia and the resulting cerium(IV) hydroxide filtered off and dissolved in sulphuric acid. 

Add 3 mL of reagent solution (dissolve 5g reagent in 12 g glacial acetic acid and dilute to 100 mL with water) for every 10 mg of magnesium present and then add concentrated ammonia solution until the pH is at least 9.3 (or no further precipitate forms). Heat at 60- 80 °C for 20 minutes, filter and wash the precipitate with hot water. Dry at 130-140 °C and weigh as Mg(C10H8ON)2 (Section 11.31). 

Lead (ca 100mg in 25 mL solution). Add 10 mL of freshly prepared reagent solution, dilute to 50 mL and add 12.5 mL of concentrated ammonia solution. 

When plotting the standard curve it is customary to assign a transmission of 100 per cent to the blank solution (reagent solution plus water) this represents zero concentration of the constituent. It may be mentioned that some coloured solutions have an appreciable temperature coefficient of transmission, and the temperature of the determination should not differ appreciably from that at which the calibration curve was prepared. 

Reagents. Dianthrimide reagent solution. Dissolve 150mg of 1,1 -dianthrimide in 1 L concentrated sulphuric acid (ca 96 per cent w/w). Keep in the dark and protected from moisture. 

Ammonia solution (concentrated, 0.880 , about 35 per cent NH3). Preferably the special atomic absorption spectroscopy reagent grade should be used. 

Note Tertiary amines and quaternary ammonium compounds yield stronger colors than primary amines [25]. The dipping solution can also be used as spray solution [44]. Other reagent compositions have also been reported in the literature (1, 3, 6, 12, 13, 15, 18, 21, 23, 41] In some cases the reagents have been made up in acetone [38, 39], methanol [14] or ethanol [37] and/or acidified with hydrochloric acid [3, 33, 37-40]. The concentrations of hexachloroplatinic(IV) acid have been in the range of 0.05 -0.4 those of potassium iodide between 0.5 and 24spray solution containing 2% potassium iodide and 0.23170 hexachloroplatinic(IV) acid hexahydrate in N-hydro-chloric acid is reported to yield the best coloration results with respect to detection sensitivity and color differentiation in the detection of morphine, codeine, quinine, methadone and cocaine [46]. Acidic reagent solutions have been recommended for benzodiazepines [10, 11]. Sulfones do not react [39]. 

Figure 1. Fiber optic system comprising a light source (1), optical filters (2, 3) for measurement of the concentration of a reagent solution. The fiber bundle (4), after passing the solution (16), is divided into three bundles (6-8) and light intensity is measured at three wavelengths in order to enable spectral correlation at different wavelengths.

Arsenic (V) causes large positive errors - arsenic (V) at a concentration of 10 pg/1 produces an absorbance of 0.07, but can be masked with tartaric acid (added in the reagent solution). When arsenic (V) was present at concentrations of 50 pg/1 it was masked with 0.1 ml of 1 x 10 4 M sodium thiosulfate added after the sulfuric acid. 

System B is the most widely used for CL detection after an HPLC separation. In this system, two pumps are required for delivering the reagent solutions in the following cases (1) the solutions for CL reaction are first combined and then mixed with an eluent (2) CL reaction conditions (e.g., pH, water and organic solvent contents, and salt concentration) need to be optimized before mixing with the CL reagent. 

Determination of the concentration of an analyte or reagent solution from its reaction with a standard or primary standard. 

Fig. 12.4 Effect of temperature of heating water bath on the apparent concentration of phosphorus. The 1.1 N H2S04 refers to the concentration of sulphuric acid in the ammonium molybdate reagent solution...

The concentration of the Grignard reagent solution is determined by titration. An oven-dried, 10-mL flask with septum is charged with 1 mg of phenanthroline and 3.0 mL of the reaction mixture. 2-Methylpropanol is added until the red-purple color is dissipated and a yellow endpoint is reached. The yield of Grignard reagent is 0.184 mol (70%). 

In addition techniques, the test substance concentration is determined from the difference in the ISE potentials obtained before and after a change in the sample solution concentration. The main advantage Ues in the fact that the whole measurement is carried out in the presence of the sample matrix, so that results with satisfactory accuracy and precision can be obtained even if a substantial portion of the test substance is complexed. Several addition techniques can be used, namely, single, double or multiple known addition methods, in which the sample concentration is increased by additions of a test substance standard solution single, double or multiple known subtraction methods, in which the sample concentration is decreased by additions of a standard solution of a substance that reacts stoichiometrically with the determinand and analyte addition and subtraction methods, in which the sample is added to a test substance solution or to a reagent solution. 

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