Ring testing

By the brown ring test with iron(II) sulphate and cold concentrated sulphuric acid. 

Qualitative Analysis. Nitric acid may be detected by the classical brown-ring test, the copper-turnings test, the reduction of nitrate to ammonia by active metal or alloy, or the nitrogen precipitation test. Nitrous acid or nitrites interfere with most of these tests, but such interference may be eliminated by acidifying with sulfuric acid, adding ammonium sulfate crystals, and evaporating to alow volume. 

Knight and Allen. This is a copper reduction method for reducing sugars in white sugar up to 0.02%. It utilizes EDTA to determine excess unreacted copper. Tests undertaken in 1994 to extend the range of this method were unsuccesshil. In spite of poor performance in ring tests, it remains an official ICUMSA method. 

FIG. 14-73 Pressure-drop data for several sizes of paU rings test conditions same as described for Fig. 14-72. [Shaiiat and Kunesh, Ind. Eng. Cbem. Res., 34, 1273 (1.9.95).] Reproduced with permission. Copyright 1995 American Chemical Society. 

A ring test proved that surfactant-selective electrodes are suitable for quantitative determination of anionic surfactants including alkanesulfonates [21]. The precision of this method, however, does not yet correspond to the state-of-the-art of the two-phase titration. Therefore, further development is needed to enhance the reproducibility and competitiveness of surfactant-sensitive titration. 

Nyholm N, P Kristensen (1992) Screening methods for assessment of biodegradability of chemicals in seawater—results from a ring test. Ecotoxicol Environ Saf 23 161-172. 

Many experts in Europe have tested the methods of both standards with various pesticide-matrix combinations in their own laboratories. Consequently, the responsible working groups of CEN TC 275 concluded that these are the best methods available. Nevertheless, there is no complete validation of all possible pesticide-matrix combinations. However, for most multi-residue methods within the standards all those pesticides which had been successfully tested in method validation trials and/or proficiency tests are listed. Also, matrices which had been examined in ring tests are listed. 

This ring test had been conducted with specially selected polar pesticides, and therefore the results are not representative of all pesticides. However, irrespective of this, the study clearly showed that validation smdies must be conducted with standards in a matrix. In recovery determinations, conducted with standards in a solvent, the analyst cannot be sure that a bad recovery is not masked by matrix effects. 

The determination of LOD and/or LOQ is not officially required. In a ring test of more than 10 laboratories initiated in 1992 by the Society of German Chemists [Gesellschaft Deutscher Chemiker (GDCh)] it was shown that these characteristics differ between laboratories by about one order of magnitude, even if the same pesticides are determined in similar matrices with the same method and calculation of the LOD or LOQ is performed in an identical way. 

L. Alder, G. Kempe, and P. Baumann, Need of Matrix Matched Standards-Conclusion from a German Ring Test, Presented at 3rd European Pesticide Residue Workshop, York, UK, July 3-5, 2000. 

In tensile testing of rubber, elongation is the increase in the distance between bench marks on a dumbbell strip or the distance apart of the grips holding a ring test piece, on the application of a load to the test sample. It is expressed as a percentage of the original distance between the marks. 

C, shake flask/UV, ring test, Kishi Hashimoto 1989)... 

Kishi, H., Hashimoto, Y. (1989) Evaluation of the procedures for the measurements of water solubility and n-octanol/water partition coefficient of chemicals results of a ring test in Japan. Chemosphere 18(9/10), 1749-1759. 

Dave, G., B. Damgaard, M. Grande, J.E. Martelin, B. Rosander, and T. Viktor. 1987. Ring test of an embryo-larval toxicity test with zebrafish (Brachydanio rerio) using chromium and zinc as toxicants. Environ. Toxicol. Chem. 6 61-71. 

As shown in Figure 11, before extensive validation, the performance of the method is evaluated appropriately. Column durability tests, robustness testing for the chromatographic and sample preparation conditions, analytical method evaluation ring tests (AMERTs), method capability assessments, and pre-validation studies are applied to... 

Table 2 - Stress corrosion cracking properties of coated 7075-T6 A1 alloy from proving ring tests (stress = 40 ksi or 275 MPa).

Nitric oxide forms a brown ring in cold ferrous sulfate solution (brown ring test for nitrates). Tbe reaction involves the replacement of a water molecule by nitric oxide in bydrated ferrous ion ... 

Nitric oxide is analyzed with GC using a TCD or by mass spectrometer using helium as a diluent and carrier gas. The characteristic mass for NO ion is 30. Also, it can he identified hy the hrown ring test in cold FeS04 solution (see Reactions). In contact with air it oxidizes to NO2, which is then identified from color, odor, and chemical properties. 

Nitrous oxide can be analyzed by GC on a molecular sieve column using a thermal conductivity detector and helium as carrier gas. It may be identified by GC/MS from its mass spectra. The molecular ion is 44. Also, it can be oxidized to NO and identified by the brown-ring test, using FeS04 solution, (see Nitric Oxide.)... 

At present (2007), lOOC is carrying out some ring tests in order to verify the accordance of the two methods of elution. Separation on the basis of unsaturation can be improved by modifying the stationary phase by Ag-F ions, as the dimension of Ag+ ion is suitable to interfere with n bonds. Christie [10-12] adopted this technique to carry out structural analysis of TAGs. TAGs were hydrolyzed by Grignard reaction, then the stereoisomers 1,2 and 1,3-diacylglyreols were transformed into diasteroisomers by derivatization with a chiral compound, and were separated on normal-phase (NP)-HPLC. 

In 2007 lOOC organized a ring test involving about 20 laboratories in order to standardize the method. The results showed a mean RSD of abont 20%. In the following sections, analytical approaches will be discussed for different kinds of food. 

Bowmer, C.T. (1993). Method for the assessment of acute toxicity of contaminated sediment using the burrowing heart vachm Echinocardium cordatum. Test Guideline for OSPAR sediment reworker ring test. Report IMW R93/317. 

ASTM D2291 standard test method for fabrication of ring test specimens for glass-resin... 

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