Nonstandard Methods

A few nonstandard methods to determine the PZC have been proposed. These methods are not recommended as replacements for standard methods, but they may be useful in certain systems for which standard methods are not applicable. 

The PZC of titania was obtained in [687] as the pH at which the rate constant of reduction of methyl viologen in the presence of titania was independent of ionic strength. 

Adhesion of positively and negatively charged latex was used to estimate the IEP of stainless steel (original and heated in air for 2 hours at 1000°C) [688], Adhesion occurs when the signs of the charge of the studied surface and of the latex are opposite. The same method has been used for other metals [689], The nonzero electrical conductivity of metals excludes measurements of their IEP by means of standard methods. 

A different version of the adhesion method was used in [690]. An amidine-grafted polystyrene latex with IEP at pH 6 (electrophoresis) was used. lEPs of thin films of iridium and tungsten oxides (among other materials) were determined, and the results complied with standard methods. 

A chromatographic method to determine the Gq of materials with low surface area was proposed in [694], Gq was calculated from the diffuse front of a breakthrough curve. Measurements at pH = 7 are not possible in this method, since the solution is unbuffered and it is difficult to obtain a solution of well-defined pH. As is classical potentiometric titration, the charging curves usually require a correction for an acid or base associated with solid particles. 

---

Particular attention should be paid to nonstandard production technologies including nonstandard methods of sterilization, sterile filtration and aseptic processing, lyophilization, microencapsulation, and certain critical mixing and coating operations. With such processes pilot-scale manufacture may not be predictive of industrial scale manufacture, and data on three full-scale production batches may be required in the application. 

Albeverio, S., Fenstad, J., Hoegh-Krohn, R., and Lindstrom, T., Nonstandard Methods in Stochastic Analysis and Mathematical Physics". Academic Press, Orlando etc. (1986). 

Validation data should be generated for all products to demonstrate the adequacy of the manufacturing process. The process validation data may not always be available, however, where the manufacturing process uses a nonstandard method of manufacture. Data demonstrating the validity of that method should be submitted in the marketing authorization file. 

No method should be used without validation. The major part of the work of validation might have been done elsewhere at an earlier time, but even then, the analyst should be satisfied that the method as used in his or her laboratory is within the validation specifications. This will be discussed below. ISO/IEC 17025 encourages the use of methods published in international, regional, or national standards and implies that if these methods are used without deviation, then the validation requirements have been satisfied. What does need to be validated are nonstandard methods, methods designed and developed by individual laboratories, standard methods used outside their scope, and amplifications and modifications of standard methods. 

For nonstandard methods, the standard 17025 lists 11 items required for the procedure. Methods must be validated (see chapter 7) and measurement uncertainty estimated (see chapter 6). In subsection 5.4, reference is made to the control of data, particularly in relation to electronic or automated equipment. 

Method validation has received considerable attention in the literature and from industrial committees and regulatory agencies. The international standard ISO/ IEC [1] requires validation of nonstandard methods, laboratory designed/devel-oped methods, standard methods used outside their intended scope, and amplifications and modifications of standard methods to confirm that the methods are suitable for their intended use. The Guidance on the Interpretation of the EN 45000 Series of Standards and ISO/IEC Guide 25 includes a chapter on the validation of methods [2] with a list of nine validation parameters. The International Conference on Harmonization (ICH) of Technical Requirements for the... 

From 1975 onward, however, the EU has requested experimental validation studies for a manufacturing process to be included in the application dossier where a nonstandard method is being used or where it is critical for the product (Council Directive 75/319/EEC [36] as amended by 91/356/EEC [37]). This requirement is amplified in the Notice to Applicants [38]. 

Other nonstandard methods (including CE and ASV) commonly used for determining inorganic constituents in water are summarized in selected monographs.114-117... 

Standard analyses are described in ASTM and Bureau of Mines publications, but nonstandard methods must be acquired from publications dealing with the specific area of interest. For example, the plastic properties of coal, which are important considerations in many process designs, can be characterized by various techniques, each having its own advantages and disadvantages (Table 19.4). 

There is significant government, university, and industrial testing experience with nonstandard methods for determining fracture of ceramics and ceramic composites. For fiber-reinforced composites, this experience has been obtained predominantly at room temperature, although significant strides have been made in the past five years in elevated temperature testing. 

Nonstandardized methods should not be used as the sole methods within a paternity testing laboratory. In addition, a nonstandard method should only be used if it can be documented that the method is used in at least one other laboratory, thus making it possible to obtain a second opinion based on repeated testing. 

Reference [2749] reports results from [1472], and [2750] reports results from [951]. The IEP of alumina at pH 7.3 is reported in [2751] without any specific information about the source of material or about experimental conditions (probably from the literature). The IEP of titania at pH 5.6 is reported in [2752] without experimental conditions (probably from the literature). The IEP of mica at pH 3-3.5 is reported in [2753] without experimental conditions (probably from the literature). Reference [2754] reports charging curves of titania, obtained under unspecified experimental conditions, probably from previous paper. Reference [2755] reports lEPs from the literature and estimated from X-ray photoelectron spectroscopy. The PZCs reported in [2756] are probably from the literature (no experimental details are provided). lEPs from the literature ar e reported in [2757-2765,2767-2792,2794-2804,2842,2852,2894,2900,2905]. lEPs and PZCs from the literature are reported in [169,2805-2807]. The lEPs/PZCs reported in [2808] are also probably from the literature. Charging and electrokinetic curves from the literature are reported in [2809]. Electrokinetic curves from the literature are reported in [2810-2812]. PZCs from previous papers by the same authors are reported in [1165,2813-2821]. lEPs from previous papers by the same authors are reported in [111,2009,2822-2825]. Electrokinetic curves from previous papers by the same authors are reported in [2826,2827]. Reference [2828] reports PZC for an ill-defined material, and PZC from the literature. Reference [2829] reports calculated charging curves based on results from the literature. References [222, 1784,2830,2831] report surface charging data from the literature. Reference [2832] reports surface charging curves and PZCs from the literature. The PZCs in Table 1 of [947] are probably taken from the literature. References [2835,2836] probably report PZCs from the literature and [2838,2839] probably report lEPs from the literature. Reference [2840] reports PZCs from the literature that were confirmed by a nonstandard method. PZCs from the literature are also reported in [84,87,92, 114,118,188,723,780,945,968,1115,1162,1505,1533,1699,1766,1773,1975,1976,1996, 2035,2708,2766,2793,2841,2843-2845,2847-2851,2853-2893,2895-2899,2901-2904,2906-2917]. Reference [2846] reports a result of coagulation study from the literature. 

Only a CCC-based IEP is reported in [3005]. The pH of minimum stability is termed the IEP in [3006]. References [3007-3009] report PZCs derived from AFM results. A nonstandard method (second-harmonic generation) was used in [651], and the purity of the surface was problematic. The inflection point-based PZC obtained in the presence of acetate is reported in [3010]. The EMF method was used in [3011] and the ISFET method in [3012,3013]. 

The term IEP is used outside its usual meaning in [3028]. The methods used in [3029,3030] are not clearly described. Two nonstandard methods used in [3031] produced very different results for the same material. Nonstandard methods were also used in [649,3032-3038]. 

It should be noted that the authors combined different types of liver tumors in their analysis, a nonstandard method of analyzing mmor data leaving open the possibility that the increase in tumor response is actually not statistically significant. 

A number of laboratory methods to dry soils have been developed of late. In the following discussion, two standard methods (mechanical convection oven and microwave) will be presented along with one nonstandard method (freeze drying). 

The testing is not limited to plastics resin form only. Besides the resin itself, very often testing the fabricated part in its final form needs to be an essential part of the design validation step to ensure that end-use performance requirements are adequately realized. Such part tests will have to be application specific and often need to involve testing imder actual or simulated service conditions employing specialized and nonstandard methods/procedures. 

Belenkii BG, Gankina ES, Kasalainen GE, Tennikov MB (1996) Nonstandard methods based on SEC principles. In Potschka M, Dubin PL (Eds.) Strategies in Size Exclusion Chromatography. ACS, Washington, DC, p 274 Berek D (1996) Macromol.Symp. 110 33... 

ASTM G 32 provides a standardized method of conducting a cavitation test. Another nonstandard method is to construct a flow channel and mount the specimens in such a manner as to produce cavitation on the downstream side of the specimen. See Ref 16 for a detailed discussion about various cavitation tests. Table 7 provides information on G 32. 

---