Filter photometer

Introduce DOP aerosol upstream of the filter through a test port and search for leaks downstream with an aerosol photometer. Filter testing shall be performed after operational air velocities have been verified and adjusted where necessary. 

Block diagram for a filter photometer with photo showing a typical hand-held instrument suitable for field work. Colorimeterrw is manufactured by Hach Company/photo courtesy of Hach Company. 

Instrument Designs for Infrared Absorption The simplest instrument for IR absorption spectroscopy is a filter photometer similar to that shown in Figure 10.24 for UV/Vis absorption. These instruments have the advantage of portability and typically are used as dedicated analyzers for gases such as ITCN and CO. 

Three special tristimulus light filters are available which, when combined with a specific light source and a filter photometer, can be used to obtain color data (20). Although this method provides added precision and accuracy, it is seldom worth the extra effort required (see Color). 

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. 

In a simple flame (emission) photometer an interference filter (Section 17.7) can be used. In more sophisticated flame emission spectrophotometers which require better isolation of the emitted frequency, a prism or a grating monochromator is employed. 

Potassium in potassium sulphate. Weigh out accurately about 0.20 g potassium sulphate and dissolve it in 1 L de-ionised water. Dilute 10.0 mL of this solution to 100 mL, and determine the potassium with the flame photometer using the potassium filter. 

In general, the apparatus for titrimetric analysis is simple in construction and operation. A typical analysis procedure would involve measurement of the amount of sample either by mass or volume, and then addition of the titrant from a burette or micro-syringe. Apart from visual indication, the course of a titration may be followed by electrochemical or photometric means in neither is the equipment required complex. A simple valve voltmeter or conductivity bridge will suffice on the one hand, and a simple spectrophotometer or filter photometer with minor modifications on the other. Varying degrees of automation may be incorporated. 

Flame photometer or spectrophotometer incorporating nebulizer and burner, filters, prism or grating monochromator, photocell or photomultiplier detection system. 

Spectral interferences may arise from the close proximity of other emission lines or bands to the analyte line or by overlap with it. They can often be eliminated or minimized by increasing the resolution of the instrumentation, e.g. changing from a filter photometer to a grating spectrophotometer. Alternatively, another analyte line can be selected for measurements. Correction for background emission is also important and is made by monitoring the emission from a blank solution at the wavelength of the analyte line or by averaging measurements made close to the line and on either side of it. 

Negative deviations occur if the radiation used is polychromatic, as in the case of filter-photometers, and if measurements are made where the value of s changes appreciably across the width of the band (Figure 9.3). However, measurements made at the maximum of a broad band show little or no deviation. 

The precision of absorption measurements depends upon the degree of sophistication of the instrumentation and on the chemical species involved, both of which can affect the apparent validity of the Beer-Lambert law. Where a single absorbing species exhibiting a broad flat maximum is to be determined, adequate results can often be achieved with a simple filter-photometer. In the visible region, this technique is known as colorimetry. The inherent disadvantage of colorimetric procedures using simple filter instruments with a broad bandpass lies in the invalidation of the Beer-Lambert law and the lack of compatibility between results from different... 

Filter-photometer or spectrophotometer incorporating prism or grating monochromator, phototube photomultiplier or diode array, glass, quartz or plastic cells. 

Fig. 1. Typical locations for CAM components, showing the photometer, 1 filter wheel, 2 monochromator, 3 shutter and aperture unit, 4 beam splitter, 5 accessories for polarized light such as a rotary analyzer and a compensator, 6 beam splitter for epi-excitation fluorescence, 7 objective lens, 8 stage, 9 substage condenser, 10 condenser aperture, 11 polarizer, 12 field aperture for photometry, 13 shutter, 14 primary illuminator, 15 arc lamp, 16 shutter, 17 monochromator, 18 filter wheel, 19 and ocular, 20.

Fig. 6. The Sofica LS photometer 1 - Hg Pump cooled by high pressure water, 2 - total reflection prism, 3 - achromatic condensing lens, 4 - wavelength filters, 5 - glass diffuser,...

A useful microfiltration apparatus, which prevents re-introduction of dust into filtered solution through contact with laboratory air, has been described by Levine et al. so and is shown in Fig. 12. The liquid is placed in the upper chamber and the lid closed. Filtration into the LS cell and recycling back into the upper chamber are carried out and repeated several times by manipulation of the stopcocks. Finally the filled cell is sealed and placed in the LS photometer. A rather similar device has been reported by Casassa and Berry32. ... 

Figure 2.13 Validity of the Beer-Lambert relationship for different monochromating systems. The absorbance of varying concentrations of cyanmethaemoglobin was measured at 540 nm using a spectrophotometer (A) and a simple photometer (B) with a glass filter.

Any of the monochromating systems described for absorptiometers may be used, although the cheaper models of flame photometer usually employ filter systems. In these cases interference from other elements at wave-... 

A novel 24-channel HPLC by Nanostream called Veloce was introduced at PITTCON 04. The column cassette contains 24 parallel microbore columns. The eluted samples are detected by a 24-channel UV filter photometer. The advantage of such a system is that it allows one to work with multiple samples simultaneously. Other interesting systems for parallel HPLC were those introduced by Eksigent, based on microfluidic flow control, and Sepiatec GmbH, which allows the processing of 75 multiple-well plates. 

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