Spectrophotometers method

Results of research and actual casework were presented by Croft and Pye (2004a) and show the spectrophotometer method to provide a precise and rapid method for soil sample comparison. In a study assessing the... 

Before the use in experiments, E. coli strains were cultured in trypti-case soy broth for 18 hr at 37 °C. After this growth period, bacteria were collected by centrifugation, bacterial pellets were resuspended in saline, and bacterial suspensions were adjusted to a desired density by the Klett spectrophotometer. Methods for the cultivation, collection, and experimental use of tubercle bacilli have been described previously (9, 16). 

Thermodynamic and kinetic measurements of the O2 binding process for the heme proteins are essential to discuss their physiological and chemical properties. Representative parameters are depicted in Table 1. The oxygen equilibrium can be directly determined by a polarographic-spectrophotometic method with an O2 electrode. The P50 value, the O2 pressure when half of the heme protein s 02-binding sites are occupied, is quite often used for the... 

The table I includes some preparation conditions and some properties of ACF. Sample ACF-2 was oxidized with HNO3 to obtain sample ACF-2ox. The Cr(VI) and Cr(lll) solutions were prepared from K2Cr207 and Cr(N03)3 respectively. The retention of chromium was determined by spectrophotometer method [5]. 

ASTM E424 Standard Test Method for Solar Energy Transmittance and Reflectance (Terrestrial) of Sheet Materials. Used to determine solar energy transmittance and reflectance of materials in sheet form using one of two procedures. Method A, the referee method, is applicable for both transmittance and reflectance and uses a spectrophotometer. Methods is applicable only for measurement of transmittance and uses a pyranometer in an enclosure and the sun as the energy source. Both test methods have given essentially equivalent results for those materials studied by the task group who prepared the method. 

Turbidity measurements obtained by spectrophotometer methods represent a useful tool for investigating the early stage of nucleation. Specifically, for a scattering path length d, the relationship between turbidity t (Equation 10.10) and absorbance A of a suspension of particles is given by... 

Weigh accurately 10 mL of the seawater sample in an Erlenmeyer flask covered with a watch glass and quantitatively transfer into the titration vessel. Add 5 mL of buffer solution, 1 mL of EBT indicator and dilute with distilled water to 350 mL, When applying the conventional spectrophotometer method proceed as follows. Position the titration vessel in the cell compartment and cover it with the light-proof lid accommodating the stirring rod and the burette tip. Draw out the capillary end of the burette to a sufficient length so that the tip is always below the surface of the solution in the titration vessel. 

ASTM, Spectrophotometers, Methods for Evaluation (Proposed), Pro-ceedings... 

Kinetic experiments were performed on a Perkin Elmer 12, 15, or 12 spectrophotometer following methods described in Chapter 2. Values for k. , given in Tables 3.1 and 3.2 were calculated using equation A8, derived in Appendix 2.1 in Chapter 2. 

Atomization The most important difference between a spectrophotometer for atomic absorption and one for molecular absorption is the need to convert the analyte into a free atom. The process of converting an analyte in solid, liquid, or solution form to a free gaseous atom is called atomization. In most cases the sample containing the analyte undergoes some form of sample preparation that leaves the analyte in an organic or aqueous solution. For this reason, only the introduction of solution samples is considered in this text. Two general methods of atomization are used flame atomization and electrothermal atomization. A few elements are atomized using other methods. 

When the identity of the matrix interference is unknown, or when it is impossible to adjust the flame to eliminate the interference, then other means must be used to compensate for the background interference. Several methods have been developed to compensate for matrix interferences, and most atomic absorption spectrophotometers include one or more of these methods. 

Other methods of background correction have been developed, including Zee-man effect background correction and Smith-Iiieffje background correction, both of which are included in some commercially available atomic absorption spectrophotometers. Further details about these methods can be found in several of the suggested readings listed at the end of the chapter. 

The science of color measurement has been explored by various authors (127,128). AATCC evaluation procedure no. 6 describes a method for instmmental measurement of color of a textile fabric. AATCC evaluation procedure no. 7 may be used to determine the color difference between two fabrics of a similar shade. Instmmentation may be either a spectrophotometer for measuring reflectance versus wavelength, or a colorimeter for measuring tristimulus values under specified illumination. If a spectrophotometer is used, however, the instmment must be equipped with tristimulus integrators capable of producing data in terms of CIE X, Y, and Z tristimulus values. 

This is primarily engaged in analysis of boiler water treatment matters and involves on-site studies of various problems and the chemical examination of corrosion products, boiler scales, etc. It can also carry out certain types of metallurgical, fuel and inorganic analysis. Normal wet methods of analysis coupled with a visible ultraviolet and atomic absorption spectrophotometer are used for a wide range of analytical applications. Equipment in use by the engineering insurers providing these services can include an ion chromatograph, spectrometer equipment, atomic... 

The methods dependent upon measurement of an electrical property, and those based upon determination of the extent to which radiation is absorbed or upon assessment of the intensity of emitted radiation, all require the use of a suitable instrument, e.g. polarograph, spectrophotometer, etc., and in consequence such methods are referred to as instrumental methods . Instrumental methods are usually much faster than purely chemical procedures, they are normally applicable at concentrations far too small to be amenable to determination by classical methods, and they find wide application in industry. In most cases a microcomputer can be interfaced to the instrument so that absorption curves, polarograms, titration curves, etc., can be plotted automatically, and in fact, by the incorporation of appropriate servo-mechanisms, the whole analytical process may, in suitable cases, be completely automated. 

The comparison of more than two means is a situation that often arises in analytical chemistry. It may be useful, for example, to compare (a) the mean results obtained from different spectrophotometers all using the same analytical sample (b) the performance of a number of analysts using the same titration method. In the latter example assume that three analysts, using the same solutions, each perform four replicate titrations. In this case there are two possible sources of error (a) the random error associated with replicate measurements and (b) the variation that may arise between the individual analysts. These variations may be calculated and their effects estimated by a statistical method known as the Analysis of Variance (ANOVA), where the... 

The basic principle of most colorimetric measurements consists in comparing under well-defined conditions the colour produced by the substance in unknown amount with the same colour produced by a known amount of the material being determined. The quantitative comparison of these two solutions may, in general, be carried out by one or more of six methods. It is not essential to prepare a series of standards with the spectrophotometer the molar absorption coefficient can be calculated from one measurement of the absorbance or... 

Visual methods have been virtually displaced for most determinations by methods depending upon the use of photoelectric cells (filter photometers or absorptiometers, and spectrophotometers), thus leading to reduction of the experimental errors of colorimetric determinations. The so-called photoelectric colorimeter is a comparatively inexpensive instrument, and should be available in every laboratory. The use of spectrophotometers has enabled determinations to be extended into the ultraviolet region of the spectrum, whilst the use of chart recorders means that the analyst is not limited to working at a single fixed wavelength. 

Discussion. Small quantities of copper may be determined by the diethyldithio-carbamate method (Section 6.10) or by the neo-cuproin method (Section 6.11), an extraction being necessary in both cases. In another somewhat simpler procedure, the copper is complexed with biscyclohexanone oxalyldihydrazone and the resulting blue colour is measured by a suitable spectrophotometer within the range 570-600 nm (orange filter). The solution measured should contain not more than 100 /tg of copper. 

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