TISAB buffer

Frant and Ross [108] recommended sample adjustment using TISAB buffer ( Total Ionic Strength Adjustment Buffer ), obtained by dissolving 57ml glacial acetic acid, 58 g NaCl and 4g 1,2-cyclohexanediaminetetraacetic acid (CDTA), adjustment of the solution pH with sodium hydroxide to 5 to 5.5 and dilution to 1 litre, all to maintain a constant ionic strength and pH between 5 and 5.5 and to complex ions such as Al or Fe that interfere in the determination. A detailed... 

Total fluorine in fluoride supplements and dental products could be determined with minimal samples pre-treatment as for example by direct acid extraction or heating in TISAB buffer solution and subsequent determination of fluoride using fluoride ISE for the reason that entire fluorine, in these products, should be, by definition, available as free inorganic fluoride. 

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... 

Fluoride complexes are rendered available for measurement by the addition of a special buffer (TISAB buffer - Total Ionic Strength Adjustment Buffer). If stronger complexing substances such as boron compounds or organic substances are present in waste waters, it is advisable to carry out distillation according to method 1 before the actual measurement. 

For calibration purposes take 25-ml portions of TISAB buffer solution in the same way and to each of perhaps 5 receivers add calibration solutions... 

The possibility of application of the PEDOT-SSA film as reference membrane was confirmed during F-ISE calibration in TISAB buffer. Since TISAB is the solution with constant pH and ionic strength (from sodium chloride), the CP-based reference electrode was expected to be a perfect substitute for a conventional electrode. In fact, almost the same slopes equal to 57.5 or 58.5 mV/pF were obtained using the PEDOT-SSA film and a conventional Ag AgCl electrode as reference electrode. 

Another approach to matrix matching, which does not rely on knowing the exact composition of the sample s matrix, is to add a high concentration of inert electrolyte to all samples and standards. If the concentration of added electrolyte is sufficient, any difference between the sample s matrix and that of the standards becomes trivial, and the activity coefficient remains essentially constant. The solution of inert electrolyte added to the sample and standards is called a total ionic strength adjustment buffer (TISAB). 

Direct analysis with the fluoride lon-selective electrode requires addition of total ionic strength adjustor buffer solution (TISAB) to the standard and to unknown samples Some advantages of this addition are that it provides a constant background ion strength, ties up interfenng cations such as aluminum or iron, which form a complex with fluoride ions, and maintains the pH between 5 0 and 5 5 According to the manufacturer s claim, reproducibility of direct electrode measurement IS 2 0%, and the accuracy for fluonde ion measurement is 0 2% [27]... 

Total Ionic Strength Adjustment Buffer (TISAB). Dissolve 57 mL acetic acid, 58 g sodium chloride and 4g cyclohexane diaminotetra-acetic acid (CDTA) in 500 mL of de-ionised water contained in a large beaker. Stand the beaker inside a water bath fitted with a constant-level device, and place a rubber tube connected to the cold water tap inside the bath. Allow water to flow slowly into the bath and discharge through the constant level this will ensure that in the... 

Total ionic strength adjustment buffers TISABs) are used to equalize Ionic activity n different solutions. 

It is often more convenient to relate the potentiometer reading directly to concentration by adjusting the ionic strength and hence the activity of both the standards and samples to the same value with a large excess of an electrolyte solution which is inert as far as the electrode in use is concerned. Under these conditions the electrode potential is proportional to the concentration of the test ions. The use of such solutions, which are known as TISABs (total ionic strength adjustment buffers), also allows the control of pH and their composition has to be designed for each particular assay and the proportion of buffer to sample must be constant. 

To leam that the change of y with ionic strength is a major cause of error in electroanalytical measurements, and so it is advisable to buffer the ionic strength (preferably at a high value), e.g. with a total ionic strength adjustment buffer (TISAB). 

Often, the potentiometric determination of concentration requires a preferred pH range. If pH is also important, then the ionic strength adjuster can conveniently function additionally as a pH buffer. Such tablets are called total ionic strength adjustment buffers (or TISABs). ... 

The fluoride content of a sample of toothpaste is unknown. Accordingly, a sample of the toothpaste was digested in acid solution, filtered to remove the white gritlike solid and then buffered with a total ionic strength adjustment buffer (TISAB) to pH 6. A fluoride electrode is immersed in the clear solution and the emf recorded when the reading was steady. 

From the discussions above, we will be aware that the concentration ([F ]) determined will in fact be an activity, i.e. a(F ). It will also be apparent that adding an acid to digest the sample of toothpaste will introduce errors into the calculation since two electrolytes are involved, thereby increasing the ionic strength / (see SAQs 3.10 and 3.11). Since the preferred pH range of the fluoride electrode is 5-6, the ionic strength adjuster (TISAB) can also conveniently function as a pH buffer. 

The activity a and concentration c are related by a = (c/c ) x y (equation (3.12)), where y is the mean ionic activity coefficient, itself a function of the ionic strength /. Approximate values of y can be calculated for solution-phase analytes by using the Debye-Huckel relationships (equations (3.14) and (3.15)). The change of y with ionic strength can be a major cause of error in electroanalytical measurements, so it is advisable to buffer the ionic strength (preferably at a high value), e.g. with a total ionic strength adjustment buffer (TISAB). 

TISAB total ionic strength adjustment buffer... 

An acceptable method quite frequently used in practice depends on the cell whose EMF is being measured having a liquid junction with a constant potential value. Such a situation is attained in the determination of the activity of fluoride ions, by adding a constant amount of quite concentrated buffer, for example TISAB, to the studied solution this buffer also fulfills other functions in the analysis (see p. 146). Then the liquid junction potential is a function of the composition of the reference electrode electrolyte and of the buffer composition alone, and not of the concentrations of the other components of the studied solution. 

Fluoride release is most frequently determined using an ion-selective electrode. Because such electrodes are incapable of detecting complexed fluoride, a decomplexing agent is generally added to the mixture prior to analysis. This frees up fluoride from most complexes as the F ion, and the total quantity of fluoride released can then be determined by the ion-selective electrode. The usual complexing agent is TISAB (total ionic solubility acid buffer) [250]. 

There are many methods that allow the determination of the concentration q of an ionic species i in a sample. In the presence of an ionic strength adjuster (ISA) or a buffering solution that can fix the pH (TISAB, Total Ionic Strength Adjustment Buffer) all of these methods are based on application of equation (18.3). 

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. 

Because ISEs are susceptible to several interferences, samples and standards are diluted 1 1 with total ionic strength adjuster and buffer (TISAB). The TISAB consists of 1 M sodium chloride to adjust the ionic strength, acetic acid/acetate buffer to control pH, and a metal-complexing agent. The ISEs consist of an ion-selective membrane, an internal reference electrode, an external reference electrode, and a voltmeter. 

A total ionic strength adjustment buffer (TISAB) is used to control the ionic strength and the pH of samples and standards in ion-selective electrode measurements. 

TISAB (total ionic strength adjnstment buffer) A solution used to swamp the effect of electrolytes on direct potentiometric analyses. 

For diluted solutions, the Debye-Hiickel law - log yj = —0.5z a// — indicates that for a given value of /, y is constant. This is why the same quantity of an inert electrolyte, called support electrolyte is added to the range of standard and sample solutions , in order to have a large excess of indifferent ions, which stabilize the ionic strength at a constant value. This ISAB (ionic strength adjustment buffer) or TISAB (for total ISAB), limits variations in yj. Under these conditions, the measured potential difference depends on the concentration of the ions to be analysed and is given by equation 19.3, which results from equation 19.2 ... 

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 ... 

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