Driscoll methods

Figure 4.10 — Flow-through sensor for aluminium speciation coupled to an FI manifold for implementation of the Driscoll method. SV switching valve IV...

The so-called Driscoll methods are all based around ion-exchange separation of the monomeric inorganic aluminium from the monomeric organic aluminium. The column packing is Amberlite IR-120 cation exchange resin [159]. In essence, the Driscoll method directly measures three operationally defined fractions ... 

Some authors claim that detection limits (DLs) of 5 mgL are easily obtainable [167] using the batch PCV detection method. However, it has been reported that daily DLs range between 5 and 10 mg L and that personnel who are highly acquainted with the method were needed to achieve DLs down to <10 mg L [168]. This poses a problem when the non-labile or monomeric organic fraction of aluminium to be measured is very small. Errors for Alni can become high, and, because the Driscoll method is a subtraction method, the uncertainty of the calculated Ali fraction (Alim—Alni) can become unacceptable. To increase the precision, sample throughput and practicality of the Driscoll method, several flow injection analysis (FIA) systems have been designed both for the PCV method [169,170] and for detection with a fluorimetric determination of the 8-hydroxyquinoline-5-sulfonic acid (8-HQS) aluminium complex in a micellar medium (cetyltri-methylammonium bromide, CTAB) [168,171]. 

One important concern about the Driscoll method is which species are actually retained by the column that is, the true chemical nature of the Alim fraction, considered the most toxic. Some authors have shown that the retention characteristics observed are sample flow dependent [172], and that each column needs to be individually characterized for aluminium retention. 

The main problem with using this type of technique for the determination of the toxic aluminium species in water is that it groups together the monomeric hydroxyaluminium, fluoroaluminium and low molecular weight (LMW) polymeric species in the same fraction (> 85% of these species exchange under 30 min [174]). Moreover, the operational definitions do not match adequately those of the more popular Driscoll methods (Table 10.1). 

The major point of these HPLC methods is that they separate the aluminium fluoride species from the other inorganic monomeric aluminium species (classic Driscoll methods do not). 

One interlaboratory method comparison exercise for aluminium speciation has been organized within the framework of the BCR project on A1 speciation [184]. Results obtained using a standard Driscoll/PCV method for the determination of the labile monomeric aluminium fraction were tested and compared to three other aluminium speciation procedures. Each of the three participant laboratories carried out both the standard Driscoll method, used as... 

Driscoll, J. L. and Martin, H. F. Detection of brominism by an automated chloride method. Clin. 

Even with the Kelen Tudos refinement there are statistical limitations inherent in the linearization method. The independent variable in any form of the linear equation is not really independent, while the dependent variable does not have a constant variance [O Driscoll and Reilly, 1987]. The most statistically sound method of analyzing composition data is the nonlinear method, which involves plotting the instantaneous copolymer composition versus comonomer feed composition for various feeds and then determining which theoretical plot best fits the data by trial-and-error selection of r and values. The pros and cons of the two methods have been discussed in detail, along with approaches for the best choice of feed compositions to maximize the accuracy of the r and r% values [Bataille and Bourassa, 1989 Habibi et al., 2003 Hautus et al., 1984 Kelen and Tudos, 1990 Leicht and Fuhrmann, 1983 Monett et al., 2002 Tudos and Kelen, 1981]. 

O Driscoll, K.F., Techniques of enzyme entrapment in gels, Methods EnzymoL, 44, 169-183, 1976. 

H.S. Horowitz, W.S. Driscoll, R.J. Meyers, S.B. Heifetz, A. Kingman, A new method for assessing the prevalence of dental fluorosis—the tooth surface index of fluorosis, J. Am. Dent. Assoc. 109 (1984) 37-41. 

The composition of the copolymer was determined by either NMR analysis at 90 MHz according to the equations derived by Mochel (21) or by infrared. (22) The agreement of these methods was 2% when applied to copolymer taken to 100% conversion. The reactivity ratios were calculated according to the Mayo-Lewis Plot (13,15), the Fineman-Ross Method (14), or by the Kelen-Tudos equation.(16,17,18) The statistical variations recently noted by 0 Driscoll (23), were also considered. 

Shreider, Yu. A. (ed.) The Monte Carlo Method, London, Pergamon, 1966 Bruns, W., Motoc, I., O Driscoll, K. F. Monte Carlo Applications in Polymer Science, ch. 1, Lecture Notes in Chemistry, vol. 25, Berlin, Springer, 1982... 

Driscoll et al. (155) summarized the relationship between N export and N deposition that is indicated by input-output budget data from a large number of watersheds in the United States and Canada these data are augmented in Figure 17b with results from recently published reports. Driscoll et al. (155) stressed that the data illustrated in Figure 17b were collected by using widely differing methods and various time scales (from 1 year to... 

Schultz-Ellison, G., Charland, C., Driscoll, J., and Thayer, W., A rapid method for immune complex detection PEG insolubilization combined with laser nephelometry. /. Immunol. Methods 31, 31-40 (1979). 

The thorough treatment of the experimental data does allow one to obtain reliable values of the reactivity ratios. The results of such a treatment are presented in Table 6.3 for some concrete system let us form a notion about an accuracy of the reactivity ratios estimations. The detailed analysis of such a significant problem in the case of the well-studied copolymerization of styrene with methyl methacrylate is reported in Ref. [227]. Important results on the comparison of the precision of rj, r2 estimates by means of different methods are presented by O Driscoll et al. [228]. Such a comparison of six well-known linear least-squares procedures [215-218,222,223] with the statistically correct non-linear least-squares method leads to the conclusion that some of them [216, 217, 222] can provide rather precise rls r2 estimates when the experiment is properly planned. 

Szwarc and Zimm described the consequences of transfer in the sense of eqn. (41) by means of differential equations [29], and O Driscoll simulated the system corresponding to the above scheme by the Monte Carlo method [30], Both kinds of approach produced polydispersity coefficient (PJPn) vs. time plots which were practically identical at longer times. 

The most generally useful methods and the only statistically correct procedures for calculating reactivity ratios from binary copolymerization data involve nonlinear least squares analysis of the data or application of the error in variables (EVM) method. Effective use of either procedure requires more iterations than can be performed by manual calculations. An cfHcicnl computer program for nonlinear least squares estimates of reactivity ratios has been published by Tidwell and Mortimer [13]. The EVM procedure has been reported by O Driscoll and Reilly [14]. 

Assay techniques For Rubisco and other carboxylases, while some spec-trophotometric methods exists (e.g., Gerard and Driscoll, 1996), the sensitivity necessary for measurements in the field makes radiochemical methods based on... 

T. A. Driscoll and B. Fornberg, Block pseudospectral methods for Maxwell s equations II. Two-dimensional, discontinuous-coefficient case, SIAMJ. Sci. Comput., vol. 21, pp. 1146-1167, 1999.doi 10.1137/S106482759833320X... 

Similar in principle to the aforesaid rotating sector method is a method known as spatially intermittent polymerization (O Driscoll and Mahabadi, 1976). It... 

From the data available, there is no consensus as to the precise experimental conditions to be used. This is especially true where the analytical separation is concerned. The resin in the column has to be conditioned with a solution of NaCl having the same ionic strength and pH as the water samples to be analysed and this is one of the main drawbacks of the method because the solution of NaCl has to be passed through the column until the pH of the effluent does not change by more than 0.2 pH units. A full Driscoll/PCV speciation procedure including all the modifications has been published elsewhere [168]. 

Driscoll/Ferron vs. Driscoll/PCV Air gave good and Al, , and A1 gave satisfactory agreement. PCV method generally better... 

Driscoll/PCV VJ. three alternative methods Air and Al m gave good agreement. Care has to be taken as one method (HPLC) did not include A1 fluoride species in the Al m fraction... 

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