Flow-through spectrophotometer

Aquatec Modular, semi-or fully automatic operation. Microprocessor controlled. A dedicated instrument designed for water analysis, i.e. dedicated method cassettes for phosphate and chloride, 600-100 samples h Flow through spectrophotometer (400-700nm)... 

Ninhydrin assay. Our method to determine reactivity towards ninhydrin was a modification of a method described previously (Moore and Stein, 1954 Moore, 1968). Briefly, dried samples were dissolved in 0.10 ml 0.1 M acetic acid and mixed with an equal volume of ninhydrin reagent (Sigma). After 15 minutes in a boiling water bath, samples were diluted with 0.80 ml ethanol/water (1 1 by vol.) and measured for absorbance at 550 nm on a flow-through spectrophotometer (Vitatron). Standards containing 0-0.6 mM leucine in 0.1 M HAc were included. Values were therefore calculated as leucine-equivalents. 

Visible and UV spectrophotometers are by far the most frequently used type of detectors in FI systems. This is also true for FI separation systems. Provided the light source intensity is strong enough, a conventional batch spectrophotometer can easily be converted into a flow-through spectrophotometer by substituting the conventional cuvette with a flow-through cell. 

Gel permeation (size exclusion) hplc was performed on a Waters Protein PAK 300SW column, in a buffer containing lOOmM sodium phosphate (pH 7.0). 5pg of protein was injected. The flow was driven at 0.5 mg/ml by a Beckman HOB pump and controller, and the eluate monitored at 220nm using a Beckman 165 flow-through spectrophotometer. 

Most chemical reactions employed are based on those used in the manual methods. Modifications aim at accelerating reactions and reducing the sample volume in order to save time and chemicals. The analyte is converted into a light absorbing compound whose absorbance is measured with a flow-through spectrophotometer. 

Analyser systems are available commercially but may also be constructed from single components according to individual requirements. A typical system for the automated analysis of seawater constituents consists of a sampler, proportioning pump, the analytical manifold (a delay and reaction system), a flow-through spectrophotometer and a data acquisition system. Fig. 10-13 shows a 4-channel CFA system built and used in the Institute of Marine Research in Kiel (Germany). One example manifold (nitrate) including a flow-through-spectrophotometer is displayed in Fig.10-14. 

Two common detectors, which also are independent instruments, are Fourier transform infrared spectrophotometers (FT-IR) and mass spectrometers (MS). In GC-FT-IR, effluent from the column flows through an optical cell constructed... 

Procedure. Allow the whole of the sample solution (1 L) to flow through the resin column at a rate not exceeding 5 mL min . Wash the column with 250 mL of de-ionised water and reject the washings. Elute the copper(II) ions with 30 mL of 2M nitric acid, place the eluate in a small conical flask (lOOmL, preferably silica) and evaporate carefully to dryness on a hotplate (use a low temperature setting). Dissolve the residue in 1 mL of 0.1 M nitric acid introduced by pipette and then add 9 mL of acetone. Determine copper in the resulting solution using an atomic absorption spectrophotometer which has been calibrated using the standard copper(II) solutions. 

The instrumentation for sensors based on absorption measurements can be designed on the traditional spectrophotometers by using a flowthrough cell for automatic sampling with the sensors mounted inside the flow-through cell shown in Fig. 20a.3. For remote optical sensing using optical fibers, the chromophores can be immobilized in reflective... 

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... 

Depending on their sensing ability, flow-through sensors can be classified into single-parameter and multi-parameter according to whether they can sense one or more analytes on passage of each sample. Multideterminations usually rely on the use of an instrument e.g. a diode array spectrophotometer) for virtually simultaneous multidetection e.g. [20]). 

A photometric flow-through sensor for the determination of carbamate pesticides (carbofuran, propoxur and carbaryl) based on similar principles as regards the detector and sensor used (a diode array spectrophotometer and a flow-cell packed with C,g resin, respectively) was employed to monitor the formation of the products resulting from hydrolysis of the analytes and online coupling of the respective phenols with diazotized sulphanilic acid. This... 

Figure 4.8 — Manifold used for implementation of the flow-through sensor developed for the determination of carbamate compounds based on hydrolysis of the analytes and dye formation, q flow-rate R reactor SV switching valve DAS diode array spectrophotometer W waste. (Reproduced from [98] with permission of the American Chemical Society).

Click only once to adjust to zero when using the reagent blank, because spectrophotometers usually adjust themselves again after a second click. Newer spectrophotometers should adjust to zero automatically. Use only one clean 1-ml quartz cuvette with two opaque walls. If the spectrophotometer has a flow-through cell, make sure that it is cleaned regularly. For further details, see Critical Parameters and Troubleshooting. 

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