Spectrophotometers computer-controlled

A modern spectrophotometer (UV/VIS, NIR, mid-IR) consists of a number of essential components source optical bench (mirror, filter, grating, Fourier transform, diode array, IRED, AOTF) sample holder detector (PDA, CCD) amplifier computer control. Important experimental parameters are the optical resolution (the minimum difference in wavelength that can be separated by the spectrometer) and the width of the light beam entering the spectrometer (the fixed entrance slit or fibre core). Modern echelle spectral analysers record simultaneously from UV to NIR. 

Optical and FTIR instrumentation. Absorption spectra were taken on three instruments. A Hewlett Packard 8450 UV/Vis Spectrophometer was used for the visible region of the spectrum. This instrument was computer control led and used to measure standard absorption spectra as well as absorption difference spectra. A Cary 14 Spectrophotometer was used for the near IR region, and an IBM IR/90 Series... 

Nanosecond Flash Photolysis Measurements.—A computer-controlled ns flash photolysis spectrometer has been described. " The system was employed in a study of the photochemistry of xanthene dyes in solution. A nitrogen laser was used to provide 2—3 mJ excitation pulses at 337.1 nm for a ns flash photolysis study of electron-transfer reactions of phenolate ions with aromatic carbonyl triplets. " A PDP II computer was used to control the transient digitizer employed for detection, and to subsequently process the data. A nanosecond transient absorption spectrophotometer has been constructed using a tunable dye laser in a pulse-probe conflguration with up to 100 ns probe delayA method for reconstructing the time-resolved transient absorption was discussed and results presented for anthracene in acetonitrile solution. The time-resolution of ns flash photolysis may be greatly increased by consideration of the integral under the transient absorption spectrum. Decay times comparable to or shorter than the excitation flash may be determined by this method. 

For reference, a spectrophotometer/colorimeter with direct concentration readout costs on the order of 2000 a digital Na/K flame photometer with an automatic sample-diluter, about 4000 a flexible, computer-controlled, single-channel analyzer under 25,000 a computer-based parallel-fast analyzer, about 50,000 and a multi-channel analyzer from about 80,000 to well over 200,000. 

Derivative spectrophotometry can be very useful additional tool which helps to solve some complicated analytical problems. Mathematical processing of spectra is very easy to use as modern spectrophotometers are computer controlled and their software are equipjped in derivatisation unit. A proper selection of mathematical p>arameters gives profits in improved selectivity, sometimes sensitivity and in simplification of analytical procedure. 

An increasing number of commercially available spectrophotometers are controlled by a computer and allow the user to extract spectral data in twoCricket Graph HI, Deltagraph and many more can be used to smooth spectra, perform subtractions and additions of whole spectra, normalizations and calculations of derivatives. 

Color labs are outfitted with laboratory size equipment that simulates the larger machines used for production internally and by their customers. Typical processing equipment found in the lab are small extruders, two-roll mills, ban-burry mills, and media mills. Small rotational, injection and blow molding machines are used to duplicate the customers process. Instruments and computers are required for testing physical properties and color. Most labs have a computer-controlled color measuring system and a light booth to evaluate color. The spectrophotometer with computer is initially used to assist in colorant formulation and later as a quality control (QC) tool to provide certification of the quahty of match to standard. The light booth provides a standardized set of conditions to visually observe color and appearance. 

Several different methods have been used to obtain derivative spectra. For modern computer-controlled digital spectrophotometers, the differentiation can be performed numerically using procedures such as derivative least-squares polynomial smoothing, which is discussed in Section. 5C-2. With older analog instruments, derivatives of spectral data could be obtained electronically with a suitable operational amplifier circuit (see... 

COMPUTER-CONTROLLED REPETITIVE OPERATION OF A STOPPED-FLOW SPECTROPHOTOMETER WITH A MAGNETIC VALVE IN PLACE OF THE STOPPING SYRINGE... 

The solvation of the ion thus depends on the donor properties of the solvent S, and the equilibrium (I) is shifted to right or left. The equilibrium was studied at different temperatures in different solvents by UV/visible spectroscopy. The apparatus consisted of a diode-array spectrophotometer (HP 8451) equipped with a computer-controlled Peltier effect thermostated sample holder. 

There have been many new developments in color measurement systems technology in recent years. A major breakthrough is in the area of portable color measurement techniques. Newly developed portable spectrophotometers (Figure 6-13h) now make it possible to measure and analyze data on the production floor. Some portable spectrophotometers are also capable of displaying an actual spectral reflectance curve. Bench-top spectrophotometers have been updated to allow more computer control of the lens, UV filter, and specular port. The ability to calibrate the UV component of the color spectrum is an important feature for measuring fluorescent colors accurately. Advances in windows-based software has improved the capabilities for statistical analysis of color measurements, color corrections, and color formulation. 

FIA star 5010 Modular, semi- or fully automatic operation. May be operated with process controller microprocessor. Can be set up in various combinations with 5017 sampler and superflow software which is designed to run on IBM PC/XT computer 60-180 samples h Dialysis for in-line sample preparation and in-line solvent extraction.Thermostat to speed up reactions. Spectrophotometer (400-700nm) or photometer can be connected to any flow through detector, e.g. UV/visible, inductively coupled plasma, atomic absorption spectrometer and ion-selective electrodes... 

Obtain an absorption spectrum of each of your standards, the unknown, and the control sample on a scanning UV-VIS spectrophotometer interfaced to a computer for data acquisition. Follow the instructions provided for your instrument and software. 

A spectrophotometer which allows spectroscopic and kinetic measurements to be made on a light irradiated sample has been developed by Ranalder et al. 5). The instrument is completely controlled by a small PDP-8/I computer. Great flexibility is introduced through software control. Several data collection routines have been written, and methods for determining molar absorption coefficients of metastable states have been discussed. 

The more the precision of the instrument, and the more the points for the time unit in the acquired profile, the better the result of the fitting of experimental data. For this reason instruments with a low measure error and connectable to a computer for the automatic and continous aquisition of data are very much prefered. The UV-Vis spectrophotometer is by far the most used instrument in chemical kinetics. It has a good sensitivity and a good control of the temperature. It is connected or easily connectable to a computer and is available nearly everywhere. The absorbance has a very low dependence on the temperature so that, in the used temperature range, its variation can be neglected during the VTK experiments. 

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