Chemical spot testing

Chemical analysis of surfaces within crevices often reveals high concentrations of chloride. Chemical spot tests can indicate acidic pH. 

Some cracks were clustered into small areas along one side of the tube, but close examination revealed numerous cracks scattered over the tube surface. Chemical spot tests revealed the presence of sulfur-containing compounds on the external surface. 

Ackland MR and Reeder JE. 1984. A rapid chemical spot test for the detection of lactic acid as an indicator of microbial spoilage in preserved foods. J Appl Bacteriol 56 415—419. 

In forensic laboratories, chemical spot tests based on color reactions, have been replaced over the years by modem, more accurate instrumental methods. However, analytical techniques based on color formation are stiU commonly employed in field tests for explosives. Being inexpensive, simple, easy-to-operate and often quite sensitive (see above), they are most suitable for use outside the laboratory as presumptive field tests for the presence of explosives. 

Consideration must be given to the quantity of sample needed for the minimum detection ]imits of the instrumental technique used. A number of techniques have been ranked in order of increasing amounts of material needed as follows mass spectroscopy (1 - 10 yg), chemical spot tests (1 - 100 yg), infrared and ultraviolet spectroscopy (10 - 200 yg), melting point (0.1 -1 mg), elemental analysis (0.5 - 5 mg), boiling point (1 - 10 mg), functional group analysis (1 - 20 mg), and nuclear magnetic resonance spectroscopy (1-25 mg). 

This laboratory has examined the many techniques which are available. These range from the classic organic analytical methods of the 19th century through chemical spot tests, solution spectrophotometry, infrared, and other optical spectroscopic techniques through mass spectrometry. Thin-layer chromatography is, by itself, a separation technique which allows identification of the separated components by some appropriate technique. In many cases the patterns obtained may be sufiicient for identification, and in the hands of such workers as... 

Field Identification. Supplemental chemistry verification by x-ray fluoresence spectroscopy or chemical spot test (e.g., for moly in 316 stainless steel) may be required. 

Chemical Spot Testing identifies metals by the color changes that occur when the surface is contacted with a... 

Chemical spot tests utilize a decision tree to identify the alloy through a series of chemical applications. Many of them are straightforward, and with some experience can be quite reliable, but other tests fall into ambiguous gray zones, generating questionable results. 

Figure 6-16. The electrographic test is the commonest chemical spot test.

For some applications chemical spot testing may be preferred over more sophisticated methods. An example where chemical spot testing proved useful was in a chemical process that was originally designed and built completely out of Monel 400. Over the years, much of the piping and process equipment was replaced with stainless steel and all the equipment had been painted. 

It would have taken roughly three weeks to complete the identification with an x-ray fluorescence analyzer, but with the use of a simple chemical spot test the job was completed in significantly less time. 

Chemical spot tests often are used to determine which pieces of debris contain explosive residues. This then is followed either by a microscopic examination of the crystals for a positive identification or to use HPLC for identification. 

Chapter 5 discusses the reasons and techniques for identifying plastics in collections. In addition to establishing the age and technological history of a plastic, identification indicates the factors and pathways by which degradation is likely to occur and thus helps the conservator to develop a treatment strategy. Simple tests enable identification of the polymer type while instrumental techniques are necessary if the various components are to be characterized. This chapter describes simple and non-destructive tests, simple and destructive tests, chemical spot tests and instrumental analytical techniques which are applied to plastics in collections today. 

This chapter describes simple and non-destructive tests, simple and destructive tests, chemical spot tests and instrumental analytical techniques which are applied to plastics in collections today. 

ANFO is typically yellowish spheres that dissolve slowly in water. Suspected ANFO is treated with a volatile solvent such as chloroform and the filtrate concentrated by slow evaporation for analysis by gas chromatography (GC) to identify the fuel oil component. The solid residue is dried and tested for ammonium nitrate by either chemical spot tests or instrumental methods. If weighed prior to solvent extraction, reweighing of the residual ammonium nitrate will demonstrate that the oil concentration is in the proper range for ANFO-type explosives. 

A wide variety of analytical methods have been applied to the detection and identification of GSR. In common with other forensic analyses they can be divided into color (chemical) spot tests for initial screening and instrumental methods. The situation with GSR is complicated by the issues of contamination and by the fact that many of the chemical components seen in GSR may have other innocent or environmental sources. 

Baroni, T.J. Chemical Spot-Test Reactions - Boletes. Mycologia 70, 1064 (1978). 

Chemical analysis of the suspected involved product(s) represents a fundamental step in the assessment of relevance in occupational allergic contact dermatitis (OACD). Preliminary studies performed by the dermatologist may direct the laboratory work [59]. There are available simple qualitative chemical spot tests that can be performed with little equipment these tests include the dimethylglyoxime test for nickel [60], the... 

Home Test Kits (Chemical Spot Tests)... 

Like phenol resins, epoxy resins can be identified rapidly with the help of a number of relatively simple, yet reliable chemical spot tests, but they serve mostiy only for establishing the class of polymer. More subtle analytical techniques are required to characteri.se technical epoxy resin formulation, especially in the presence of additives, fillers or perhaps even of spurious materials. The decisive breakthrough in the systematic characterisation of epoxy resins came with the introduction of thermal degradation procedures into polymer analysis. The polymer composition can be established beyond doubt from the separated and identified products of thermal degradation. The problems of separation and detection of these products have been solved to practice by GLC - and... 

Velapoldi, R. A., and S. A. Wicks. "The Use of Chemical Spot Test Kits for the Presumptive Identification of Narcotics and Drugs of Abuse." Journal of Forensic Science,... 

O Neal, C. L., et al. "Validation of Twelve Chemical Spot Tests for the Detection of Drugs of Abuse." Forensic Science International, 109 2000,189-201. 

In the 2006 Proposal, EPA noted that it would look to ASTM International s E1828, Standard Practice for Evaluating the Performance Characteristics of Qualitative Chemical Spot Test Kits for Lead in Paint, or equivalent for a validation method for test kits. With the input of stakeholders, EPA is adapting this ASTM Standard for use in the laboratory validation program. The testing protocol will consist of an evaluation of the performance of the test kits, using the manufacturer s instructions, on various substrates, such as wood, steel, drywall, and plaster, with various lead compounds, such as lead carbonate and lead chromate, at various lead concentrations above and below regulatory threshold for lead-based paint. 

Two general types of field measurements for detecting lead in paint, PXRF and chemical spot tests are available. Although it is desirable to have a... 

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