Wickbold method

In the Wickbold method, solid samples are vaporised in an oxygen stream and fed into an oxyhydrogen flame, which bums in a cooled quartz tube. The combustion products are condensed here, or are captured in an absorption solution as gaseous materials. Although combustion in a Wickbold apparatus is a quick and effective method for destroying organic material of all types, incomplete destruction may occur [19]. In special digestion vessels, known as cold-plasma ashers (CPA),... 

One of the oldest methods in the literature for the measurement of organic fluorine compounds is the Wickbold method [125], where organic fluorine is converted to hydrogen fluoride via combustion. The Wickbold method is useful for determining the total organic fluorine content of a sample, but is nonspecihc and does not provide information on individual fluorinated molecules. In addition, for samples containing PFCs, the combustion may lead to incomplete decomposition and subsequent underestimation of the total fluorine content of the sample [125]. 

A more recent development is the Wickbold method (ASTM D-2785, IP 243). This is basically similar to the lamp method except that the sample is burned in an oxy-hydrogen burner to give much more rapid combustion. An alternative technique, which has the advantage of being nondestructive, is X-ray spectrography (ASTM D-2622). 

The first fluoride instrument design employed catch and hold valves which served to capture and concentrate the combustion products prior to detection. The results achieved with this oxygen combustion/ISE method were compared with the commonly used Wickbold method. It was shown that the results corroborated and, furthermore, the relative standard deviations were decreased with the oxygen combustion/ISE method (see Table 1). 

The oxidative combustion wifli ion-selective electrode method described here can be used to accurately determine fluorine in liquid hydrocarbons and liquefied petroleum gases at levels down to 0.5 ng/pl. Results obtained are in good agreement with those achieved with the Wickbold Oxy-Hydrogen Combustion method. The oxidative combustion with ion-selective electrode method is less time consuming, less hazardous, and more sensitive than the Wickbold method. The analysis is also applicable to a range of sample types not discussed here, including aqueous based systems and solids. 

Total chlorides can be determined by the Schoniger method, which is rapid and utilizes small samples, and by the Wickbold method, which can be utilized for polymers as solids or liquids which may be aspirated into the combustion chamber as solutions in a suitable solvent. The Paar bomb or Wickbold combustion techniques are particularly amenable to the analysis of urethanes. 

Wickbold Method (Barium Bismuth Iodide Method) for Nonionic Surfactants [66]... 

Poloxamers are used primarily in aqueous solution and may be quantified in the aqueous phase by the use of compleximetric methods. However, a major limitation is that these techniques are essentially only capable of quantifying alkylene oxide groups and are by no means selective for poloxamers. The basis of these methods is the formation of a complex between a metal ion and the oxygen atoms that form the ether linkages. Reaction of this complex with an anion leads to the formation of a salt that, after precipitation or extraction, may be used for quantitation. A method reported to be rapid, simple, and consistently reproducible [18] involves a two-phase titration, which eliminates interferences from anionic surfactants. The poloxamer is complexed with potassium ions in an alkaline aqueous solution and extracted into dichloromethane as an ion pair with the titrant, tet-rakis (4-fluorophenyl) borate. The end point is defined by a color change resulting from the complexation of the indicator, Victoria Blue B, with excess titrant. The Wickbold [19] method, widely used to determine nonionic surfactants, has been applied to poloxamer type surfactants 120]. Essentially the method involves the formation in the presence of barium ions of a complex be-... 

The solvent sublation procedure of Wickbold [18] is another method that has been used for the analysis of LAS present in seawater [19,20], The solvent sublation technique (gaseous stripping into organic solvent, often ethyl acetate) has also been used to isolate and concentrate nonionic surfactants, e.g. AEs and APEO in aqueous samples [21,22], The co-extracted interferences can be eliminated by cation/anion ion-exchange and alumina chromatography [23,24]. 

IP LLE methods are generally employed for the extraction of LASs from river waters and the solvent sublation method of Wickbold is still used for their extraction from seawater [85]. SPE methods making use of C18 and C8 phases are largely employed [85]. The amount of sorbent is optimized as a function of the degree of pollution and the average composition of river waters [85]. The performances of C18 disks and C18 cartridges are compared [85]. 

The lamp combustion method (ASTM D-1266, IP 107) and the Wickbold combustion method (IP 243) are used for the determination of sulfur in petroleum and as trace quantities of total sulfur in petroleum products and are related to various other methods (ASTM D-2384, ASTM D-2784, ASTM D-2785, ASTM D-4045)... 

Analytical methods are available in standard form for determining volatile sulfur content and certain specific corrosive sulfur compounds that are likely to be present. Volatile sulfur determination is made by a combustion procedure (ASTM D-126, IP 107) that uses a modification of the standard wick-fed lamp. Many laboratories use rapid combustion techniques with an oxy-hydrogen flame in a Wickbold or Martin-Floret burner (ASTM D-2784, IP 243). 

Flame Decomposition. Utilization of a petroleum sample as a fuel for combustion in a specially devised burner system, such as that described by Wickbold (6), can be an effective way to destroy large amounts of an organic matrix. The method is applicable to those elements which are either volatile or form volatile compounds and which can be trapped quantitatively in a suitable scrubber. This technique was used to prepare samples for cold vapor atomic absorption determination of mercury. Details are included in Chapter 12. 

Except neutron activation, methods which have been used to determine mercury in organic materials involve a matrix decomposition step prior to the actual measurement. Oxidative techniques involving various combinations of acids and salts have been widely used for matrix destruction (1, 2, 3, 4, 5), as have the Schoniger, Wickbold, and other bomb and tube combustion techniques (1, 6, 7, 8, 9,10). 

The Project investigated two methods for sample decomposition before mercury measurement. One involved acidic oxidation, and the other involved combustion in a Wickbold oxy-hydrogen burner (26). 

Table 12.III. Recovery of Mercury by Wickbold Combustion Method...

Wickbold Decomposition—Cold-Vapor Atomic Absorption Method. 

Scope. This method is applicable to the determination of mercury in petroleum and petroleum products (except leaded gasoline) which can be burned in a Wickbold apparatus. The method is capable of measuring the amount of mercury in a sample down to the 5-ng/g level. The upper limit of the method as presented is determined by the linearity of the mercury calibration curve (Figure 1.2). Three to four samples can be analyzed conveniently at one time, and the average analysis time is about 2 hr. 

Outline of Method. A sample is weighed into a beaker, dissolved in benzene 2-propanol, and burned in an oxy-hydrogen flame using a Wickbold combustion apparatus. The combustion products are collected in a 5% sulfuric-nitric acid mixture containing potassium permanganate. Prior to measurement, trapped mercuric salts are reduced to elemental mercury with tin (II) chloride. The mercury is then swept out of solution and measured by cold-vapor atomic absorption spectroscopy. 

Kotz etal. (1972, Decomposition of biological materials for the determination of extremely low contents of trace elements in limited amounts with nitric acid under pressure in a Teflon tube) Hartstein et al. (1973, Novel wet-digestion procedure for trace-metal analysis of coal by atomic absorption) Jackson etal. (1978), Automated digestion and extraction apparatus for use in the determination of trace metals in foodstuffs) Campos etal. (1990, Combustion and volatilization of solid samples for direct atomic absorption spectrometry using silica or nickel tube furnace atomizers) Erber et al. (1994, The Wickbold combustion method for the determination of mercury under statistical aspects) and Woit-tiez and Sloof (1994, Sampling and sample preparation). 

Erber D, Quigk L, Winter F, Roth J and Cam-mann K (1994) The Wickbold combustion method for the determination of mercury under statistical aspects. Eresenius J Anal Chem. 349 502-509. 

Erber, D., Roth, J., and Cammann, K. (1997) Quality assurance system for a decomposition method as demonstrated for the Wickbold combustion technique. Accred. Qual. Assur, 2, 332-7. 

To properly assess the role of surfactants in the environment, the nature and concentration of these compounds in effluents and surface waters must be known. This requires reliable product-specific analytical methods. Summarising descriptions were recently published by Wickbold [63] and Kunkel [64]. Analytical methods are necessary to verify environmental levels and to follow disappearance of parent compounds in biodegradation tests. The definition of the OECD report [60] reads as follows ... 

In the case of nonionic surfactants the course of biodegradation is followed by an analytical procedure (method of Wickbold) based on the formation of a precipitate with barium tetraiodobismuthate. In its present form the procedure refers specifically to water-soluble ethoxylates and propoxylates. This group comprises the bulk of nonionic surfactants presently in use. ... 

Noninstramental analysis of ether sulfates is complex because of the various types of organic material which must be distinguished. Puschmaim and Wickbold have described comprehensive procedures for quantitative determination of the components in alkyl ether sulfates by wet chemical methods (68,69). Nowadays, these tests are usually performed by HPLC. Cloud point determination, a measure of EO content, is described in Chapter 2 with characterization of nonionic surfactants. 

Wickbold, R., ABS in surface waters by the Longwell-Maniece method (in German), Tenside, Swfactants, Deterg., 1976,13, 32-34. 

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