TISAB solution preparation

Pipette 25 mL of solution B into a 100 mL beaker mounted on a magnetic stirrer and add an equal volume of TISAB from a pipette. Stir the solution to ensure thorough mixing, stop the stirrer, insert the fluoride ion-calomel electrode system and measure the e.m.f. The electrode rapidly comes to equilibrium, and a stable e.m.f. reading is obtained immediately. Wash down the electrodes and then insert into a second beaker containing a solution prepared from 25 mL each of standard solution C and TISAB read the e.m.f. Carry out further determinations using the standards D and E. 

Preparation of the TISAB solution Mixture of 500 cm of distilled water 57.0 cm of glacial acetic acid, 58.0 g of sodium chloride, and 4.00 g 1,2-cyclohexanedinitrilo-tetraacetic acid (CDTA) (C6Hio[N(CH2C02H)2]2-H20) are mixed and intensively stirred. When a homogeneous solution is obtained, it is cooled to room temperature and the pH is adjusted between 5.0 and 5.5 with 5M NaOH. It is transferred to a 1 dm volumetric flask and filled up to the mark with distilled water. The ready-made TISAB solution is stored in a polyethylene bottle. 

The experimental protocol used to conduct measurements is based on the following principle a series of standard solutions is prepared by successive dilution of a stock solution and an excess but constant volume of buffer (ISAB or TISAB) is added at each step. Sample solutions are prepared in the same fashion. For each of the standards, the potential across the electrodes is measured and a semi-logarithmic calibration curve E — f(q) is obtained (Fig. 18.6). Using this curve and the potential difference obtained for each of the sample solutions, the concentration of species i can be obtained. 

Using an expanded scale pH meter, such as the Orion 801, pipet 10 ml of the stock solution into a small beaker and add 10 ml of Tisab (Orion No. 94-09-09). Determine the electrode potential using a fluoride electrode Orion 94-09. Comparison is made by bracketing with fluoride standards prepared similarly. 

In an earlier study, Larsen and Ravnholt [55] showed that the dissolution kinetics of differently sourced CaF2 and the calcium-fluoride-like material that is actually formed in saliva (as opposed to in water) varied markedly, depending on both the different solid preparations and on the fluid (water or saliva). Saliva inhibits CaF2 s precipitation and dissolution. This is illustrated in figure 3, which shows results of a salivary clearance study taken from a patent of Clarkson et al. [56], Aqueous solutions of calcium chloride and NaF were mixed at various times relative to the application of the resultant CaF2 -precipitating mixture to a group of individuals as a form of mouth rinse. Saliva samples were collected at least 1 h after the 1-min mouth rinse and were analysed for F after the addition of TISAB buffer, as described elsewhere [42], The effect of the age of the precipitated material was dramatic salivary F concentrations... 

Provided. TISAB (total ionic-strength adjustment buffer) solution, which is prepared with 57 mL glacial acetic acid, 58 g sodium chloride, and 4 g CDTA (cyclohexylenedinitrUotetraacetic acid) in about 500 mL water, adjusted to pH 5.0 to 5.5 with 5 M NaOH and diluted to a total volume of 1 L. A 1 1 dilution of all samples with this solution serves the following ... 

Analysis of unknown. After preparing the calibration curve, obtain an unknown fluoride sample. This may be a synthetic solution, in which case obtain the unknown in a 250-mL volumetric flask. Immediately dilute to volume with distilled deionized water and transfer to a polyethylene bottle. Add 10 mL of the unknown with a pipet to a small plastic beaker followed by 10 mL TISAB. Record the mV reading as above. Make at least three separate runs (separate additions and potential readings). Note The unknown... 

Procedure Calibrating standard solutions are prepared as shown in Table 6.3. The sample solution is diluted with TISAB 1 1. The diluted sample and the calibrating standards are introduced into the carefully washed measurement cell the ISE and the reference electrode are dipped into the solution and the cell voltage is calculated. The solution is stirred. When stable cell voltage is achieved, its value is taken and used for the preparation of the calibration curve or for the evaluation of the sample concentration. Often more or less automatic apparatus is employed in practice with automatic... 

Preparation of TISAB II The mixture of 4.5 g of cyclohexane 1,2 diamine N,N,N, N -tetraacetic acid (CDTA), 58 g sodium chloride, 57 cm glacial acetic acid, and 500 cm water are stirred while 120 cm of 5 M sodium hydroxide solution is added slowly. After complete dissolution, the pH is adjusted to the range of 5.0-5.5 with sodium hydroxide, and washed in 1 dm volumetric flask and filled up to the mark with deionized water. This solution can be stored for a longtime in plastic bottles. 

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