Quartz cuvette

Kinetic measurements were performed employii UV-vis spectroscopy (Perkin Elmer "K2, X5 or 12 spectrophotometer) using quartz cuvettes of 1 cm pathlength at 25 0.1 C. Second-order rate constants of the reaction of methyl vinyl ketone (4.8) with cyclopentadiene (4.6) were determined from the pseudo-first-order rate constants obtained by followirg the absorption of 4.6 at 253-260 nm in the presence of an excess of 4.8. Typical concentrations were [4.8] = 18 mM and [4.6] = 0.1 mM. In order to ensure rapid dissolution of 4.6, this compound was added from a stock solution of 5.0 )j1 in 2.00 g of 1-propanol. In order to prevent evaporation of the extremely volatile 4.6, the cuvettes were filled almost completely and sealed carefully. The water used for the experiments with MeReOj was degassed by purging with argon for 0.5 hours prior to the measurements. All rate constants were reproducible to within 3%. 

It seems that deep-seated cleavage of the dioxin nucleus must accompany dechlorination in methanol. When pure dibenzo-p-dioxin (II) was irradiated in cyclohexane solution in a quartz cuvette, it darkened in color, and a precipitate of intractable dark brown material was collected and was insoluble in the common solvents except for methanol. 

Figure 5 shows the dependence of the total emission intensity on the excitation intensity and its spectral width obtained from DCM-encapsulated dendrimers. A nitrogen laser (wavelength of 337 run, pulse duration of 4 ns, and repetition rate of 10 Hz) was used as the excitation source. A cylindrical lens focused the excitation beam onto a stripe 200 pm wide on a quartz cuvette... 

Pectolytic activity was also studied in batch reactors, following the reaction progress in thermostated quartz cuvettes. The reaction medium (3 cm ) was prepared with 1.5 g/L pectin in the standard buffer and 0.063 mg of enzyme. The absorbance of the reaction mixture against the substrate blank was continuously recorded at the spectrophotometer (Perkin Elmer Lambda 2, USA). Typical reaction time was 15 minutes, but initial reaction rates were estimated considering only the absorbances recorded during the first 200 seconds, range of totally linear response. 

We have extended the seed-mediated technique for the synthesis of bimetallic nanoparticles, having core-shell type structure appending photoreduction of metal ions. It has been proved that the deposition of a less noble metal (M) as shell on a preformed nobler nanoparticle core (M ) seems to be very effective by UV activation. Using this seed-mediated method we were able to synthesize Aucore Agsheii particles. First for the preparation of gold seeds (S), TX-lOO (10 M) and HAuC (5.0 x 10 %) were taken in a quartz cuvette so that the final concentration of Au(III) ion remained 5.0 x 10 M. Then the... 

Fluorescence spectra were recorded using an SLM 4800 spectrofluorimeter (Bioritech, Chamarande, France) fitted with a thermostat-controlled (30°C) front-surface accessory. The incidence angle of the excitation radiation was 60°. Coagulation kinetics were performed in a quartz cuvette 1 cm x 1cm. All spectra were corrected for instrumental distortions in excitation using a rhodamine cell in the reference channel. 

Polymer films were made from solution (f)) and spread on quartz windows. To remove oxygen the films were kept for 2 hours at 10 5 Torr and then sealed off in cylindrical quartz cuvettes. 

In order to determine the effect of air on fluorescence loss, free films of polymer 1 (15 ym thick) were placed in a quartz cuvette, which was evacuated prior to excitation in the fluorescence spectrophotometer. Although the initial loss constant was not determined accurately, both constants (entry 4) were substantially smaller in vacuo relative to air. Fluorescence loss from correspondingly thick films in air is provided in entry 5. 

Material required For total protein extract and enzyme activities extraction buffer 50 mM potassium phosphate, pH 7.0,1 mM EDTA, 1% of PVP (100 mg/mL), for CAT, GR, and SOD and with 10 mM ascorbato for APX activity. Bio-Rad protein assay, centrifuge, spectrophotomer and quartz cuvette. 

Andreae [712] used four different detectors in his investigations the electron capture detector (for the methylarsines), the quartz cuvette atomic absorption detector (for arsenic and antimony species), the graphite furnace atomic... 

The graphite furnace system was originally developed by Andreae [712] when he found that the quartz cuvette gave only very poor sensitivity for germanium. This was attributed to the formation of GeO, a very stable diatomic species, at the relatively low temperatures of the quartz cuvette. At the higher temperatures available with the graphite furnace (2600 °C for the determination of Ge), a sensitivity could be obtained for germanium comparable to that of the other hydride elements. 

Provide plausible reasons why interference fringes are not observed for the typical 1.0 cm quartz cuvette used in the ultraviolet region. 

Zero the UV spectrophotometer with the blank at 220 nm. Measure all solutions (calibration standards, unknowns, and control) as follows using quartz cuvettes. Measure the absorbances at... 

Quantum clusters are highly photostable when compared with organic fluorophores. A study was conducted to check the photostability of clusters in comparison to organic fluorophores and semiconductor quantum dots [12]. Photostability of a gold cluster capped with dihydrolipoic acid (AuNC DHLA) was compared with polymer coated CdSe/ZnS semiconductor quantum dots and two different organic fluorophores namely fluorescein and rhodamine 6G (Fig. 5). For the study, 20 pi of fluorescent AuNC DHLA was dissolved in sodium borate buffer of pH 9. The sample was loaded into a quartz cuvette and was exposed to blue-light (480 nm)... 

Registration of ROS was carried out by electron paramagnetic resonance (EPR) technique using spin trap l-hydroxy-2,2,6,6-tetramethyl-piperidine-4-OH (2 x 10 3 M). EPR spectra in the samples were registered at room temperature in quartz cuvette with the volume of 200 pi (Burlaka et al., 1994). 

The solubility was determined spectrophotometrically on a Shimadzu UV160A using the reference quartz cuvette filled with pure vegetable oil under testing and the sample cuvette filled with the solution of C60 or C70 in a given vegetable oil. 

The NIR monitoring was done off-line using a Eoss NIRSystems Model 6500 analyzer in transmission mode and a quartz cuvette with 0.5-mm path length. The spectra had 10-nm wavelength resolution with data... 

Isothermal DSC measurements were made with a Perkin Elmer DSC-2C apparatus, modified for UV irradiation (Figure 1). The aluminum sample holder enclosure cover contains two windows, one for the sample and one for the reference compartment. The windows consist of cylindrical quartz cuvettes which have been evacuated in order to prevent moisture condensation. The windows were mounted by using a thermally cured epoxy adhesive. 

Table 4.6.17 Assay mixture for assessment of 6-phosphofructokinase activity. Pipette these solutions into 1-ml quartz cuvettes. Instructions for the preparation of these solutions are given in section 4.6.20.3...

B 7. A solution of purified DNA gave in the spectrophotometric assay an A16a of 0.35 when measured in a 1-cm quartz cuvette. What is the concentration of the DNA in /xg/mL ... 

Example 2 A solution of the nucleotide base uracil, in a 1-cm cuvette, has an absorbance at Amax(260 nm) of 0.65. Pure solvent in a matched quartz cuvette has an absorbance of 0.07. What is the molar concentration of the uracil solution Assume the molar absorption coefficient, e, is 8.2 X 103... 

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