Colorimetry and photometry

Photometry is similar to infrared spectroscopy a method for measuring the light transmitting ability of a solution in order to determine the concentration of a light absorbing material present in the solution. Crude oil chemists generally use spectrometry in three ways  

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The motions that are analyzed by colorimetry and photometry are no longer of rotational or vibrational nature as was shown for all previous spectral analyses. The motions analyzed at the visible and ultraviolet spectral regions are specific for each atom or chemical group. In order to understand the nature of these motions, it is important to understand the structure of the atom. 

There are lots of models on the structure of the atom that can help us to understand the nature of matter. These models are simplified representations of real atoms. The models can be made by atomic physics to be more accurate but this makes the model more complicated. Today, it is possible to describe atoms very accurately by using quantum mechanics. However, the question that cannot be answered accurately is whether the true model has been found or not. 

Which of the models is the best depends on what it is used to describe. For example, there are applications in which it is sufficient to regard the atoms as small particles. 

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CIE — Acronym for Commission Internationale de l Eclairage . By general consent, in all countries the specification of standard (i.e., ideal) observers for use in colorimetry and photometry is the province of CIE. 

Colorimetry and photometry are the next spectral optical analysis methods. Both the methods measure absorbed light as was shown for infrared spectroscopy. However, for both these analyses, light with shorter wavelength is used. Colorimetry uses light with wavelength of only the visible spectral area and photometry uses the visible light, ultraviolet, and in some case, infrared area. A comparison of the different spectral areas is shown in Figure 2.47. 

DIN 5033, Part 9 Colorimetry reflectance standard for colorimetry and photometry , 1982. 

Carbon-13 n.m.r. and mass spectrometry have become essential methods in quantitative analysis of alkaloid mixtures extracted from plants, in addition to g.l.c. and photometry. Study of the mechanism of fragmentation of 3-substi-tuted tropanes is a useful tool for analysis of mixtures of tropane alkaloids. A comprehensive study on the n.m.r. spectroscopy of tropane alkaloids included most major representatives of this class. Other papers deal with the n.m.r. spectra of cocaine metabolites and derivatives. A radioimmunassay of atropine and benzoylecgonine in urine was published. Photometric determination of tropane derivatives in chloroform extracts was done via colorimetry of the bromocresol purple complex.Adsorption chromatography methods have been used with different resins. ... 

Introduction. Metal indicators are organic molecules which form specifically colored soluble complexes with metal ions in aqueous media. Here, the color of the complexes and of the free indicator must be different. These reactions can be used in two analytical procedures volumetry (complexometry) and colorimetry/ photometry. In both methods, the concentration of metal ions is determined, but with different techniques. 

Colorimetry/photometry exploits the fact that the color intensity of the complex correlates to the metal ion concentration, at least within a certain concentration range. Therefore, sufficient indicator is added to the sample that the indicator forms a colored complex with all ions of the metal of interest in solution. The color intensity of this complex is then either compared visually against the color of reference samples (colorimetry) or the color intensity is measured at a defined wavelength with an instrument and then compared with a calibration curve (photometry). 

Due to the different requirements of the two methods, the indicators for metal determination are often to be different in colorimetry/photometry and volume-try/complexometry (see Table 5.22). 

Color difference between free and complexed indicator less important (photometry), quite important (colorimetry) very important... 

Laboratory-based methods have been developed for field-measurement of the main water quality parameters, and their use can be standardized. They are generally based on the same principles as the equivalent laboratory based methods (e.g. oxidation, colorimetry, photometry) but use simplified procedures in order to overcome the constraints of working in the field. Currently there are numerous commercially available devices for online and on-site use, and these provide efficient tools for surveillance, operational and investigative monitoring in the frame of WFD. These techniques are suitable for such applications as incident detection in water treatment plants, detection of accidental pollution, and measurement of spatial and temporal variation in water... 

Ion chromatography has become an indispensable tool for the analytical chemist in the area of anion analysis. In many cases this method has superseded conventional wet chemical methods such as titration, photometry, gravimetry, turbidimetry, and colorimetry, all of which are labor-intensive, time-consuming, and occasionally susceptible to interferences. Publications by Darimont [1] and Schwedt [2] have shown, that ion chromatographic methods yield results comparable to conventional analytical methods, thus dissolving the scepticism with which this analytical method was initially met. In the field of cation analysis, ion chromatography is attractive because of its simultaneous detection and sensitivity. It provides a welcome complement to atomic spectroscopic methods such as AAS and ICP. 

Photometry and colorimetry are used by crude oil chemists to determine the content of different metals and heteroatomic compounds in crude oil and petrochemical products. Many references on photometry and colorimetry are given at the end of this chapter. Many authors have described the successful analysis of different metals in motor fuels by photometric and colorimetric methods. The composition of additives used during fuel production can be characterized by photometric and colorimetric methods because very many additives contain metals. It is not only fuels that can be characterized by photometry and colorimetry. Lubricants, which contain metals as an important component, can be successfully determined by these methods. These methods can quickly give qualitative information on heavy metals and heteroatomic compounds such as oxygen and sulfur in crude oil. More on this topic can be found in references 76 and 77 at the end of this chapter. 

The determination of common inorganic anions (fluoride, chloride, nitrite, bromide, nitrate, phosphate, and sulfate) and cations (sodium, potassium, magnesium, and calcium) was traditionally carried out using wet chemical methods such as gravimetry, titration, photometry, tmbi-dimetry, and colorimetry. 

Spears, G. R., High speed photometry and colorimetry of lamps luminaires, in Lighting Design Appl, 38-42 (1987). 

The colorimetry in the visible range and the photometry in the infrared and ultraviolet ranges constitute the techniques that are used. If there is no interference between components and the mixture absorbs in the infrared range, the total infrared analyzer will be rrsed (see Figure 4.3). 

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