UV spectrophotometric technique

Visible and UV spectrophotometric techniques are most convenient for studying the polymer and various oxidation states of plutonium. The spectra of the plutonium states and the procedure for resolution of the concentrations were previously described (9 ). Changes in the relative concentrations of the oxidation states and of the polymer generally are determined from corresponding changes in the spectra and a comparison of the changes to standard spectra of the various states. These techniques have been used exclusively for studying the photochemistry of aqueous plutonium. 

Tewari SN, Sharma IC. 1978. Study of the distribution of chlorinated organic pesticides in different autopsy materials of human poisoning cases using TLC and UV spectrophotometric techniques. Chemical Era 215-218. 

Leakage of the polyelectrolyte carriers to the feed and strip solutions was tested using UV spectrophotometric techniques [26, 96]. The wavelengths used were 275 nm for PVSH, 260 nm for PVP, and 248 nm for BPEI. The reference was deionized water. The concentrations of the carrier in the feed and strip solutions were close to or under the detection level (2-3 ppm) of the technique in all measured solutions. 

Abuiijeie, M.A. el-Din, M.S. Mahmoud, LI. Determination of theobromine, theophylhne and caffeine in various food products using derivative UV-spectrophotometric techniques and high-performance liquid chromatography. J.Liq.Chromatogr., 1992, 15, 101-125 [ethyl paraben (IS)]... 

Determination of Hydrophobe Incorporation. A quantitative UV spectrophotometric technique was developed for the determination of the incorporation of hydrophobic monomer into a water-soluble polymer. The technique was based on UV spectroscopic detection of hydrophobic monomers containing phenyl groups. The placement of the phenyl groups into... 

The official methods for determination of vinblastine sulfate are UV spectrophotometric techniques(6,8). 

A fully automated instrumental procedure has been developed for analyzing residual corrosion inhibitors in production waters in the field. The method uses ultraviolet (UV) and fluorescence spectrophotometric techniques to characterize different types of corrosion inhibitors. Laboratory evaluations showed that fluorescence is more suitable for field application because errors from high salinity, contamination, and matrix effect are minimized in fluorescence analysis. Comparison of the automated fluorescence technique with the classic extraction-dye transfer technique showed definite advantages of the former with respect to ease, speed, accuracy, and precision [1658],... 

JV/VIS spectrophotometry was the earliest technique to determine antioxidants [37-39]. UV/VIS has been used for the quantitative determination of BHT, stalite, etc. in rubbers [40]. Quantitative UV spectrophotometric... 

Although considered a basic technique, ultraviolet-visible (UV-vis) is perhaps the most widely used spectrophotometric technique for the quantitative analysis of pure chemical substances such as APIs in pharmaceutical analysis. For pharmaceutical dosage forms that do not present significant matrix interference, quantitative UV-vis measurements may also be made directly.114,115 It is estimated that UV-vis-based methods account for 10% of pharmacopoeia assays of drug substances and formulated products.116... 

Although a great variety of analytical techniques have been applied to the simultaneous determination of methylxanthines in various matrices, HPLC is the one most frequently used nowadays. Most of the methods are based on reversed-phase HPLC, using ACN, MeOH, or THF in acetate or phosphate buffer as mobile phase and UV spectrophotometric detection (256 -270). Some RP-HPLC methods were proposed in combination with solid-surface room-temperature phosphori-metric detection (271), mass spectrometry (272), or amperometric (273) detection. The separation can also be achieved by RP ion-pair or ion-interaction HPLC (274-277) or micellar HPLC (278). In contrast, in recent years few normal-phase HPLC methods (279) were reported (see Table 5). 

These are now probably the most widely used methods in kinetic and mechanistic studies, and include a wide range of spectral frequencies radio frequencies (NMR, ESR), IR and UV-vis. Appropriate instrumentation which is easily adapted for kinetics is readily available in most research laboratories it is usually easy to use, and the output easily interpreted. Spectrophotometric methods are also widely used for the determination of equilibrium constants [25]. However, before deciding upon a spectrophotometric technique, the following experimental aspects must be considered carefully. 

Atoms of certain metals will absorb and emit radiation of specific wavelengths when heated in a flame, in direct proportion to the number of atoms present. Atomic spectrophotometric techniques measure the absorption or emission of particular wavelengths of UV and visible light, to identify and quantify such metals. 

High performance liquid chromatography (HPLC) has been widely used for many years in industrial laboratories but its use in environmental laboratories has usually been restricted to analyses such as the determination of polyaromatic hydrocarbons and linear alkylbenzene sulphonates. Traditionally gas chromatography (GC) has been the first choice technique and HPLC only used when GC has proved unsuitable, due to thermal lability or other reasons. This reliance on GC is despite the fact it has been reported that 80-90% of the total organic carbon content in waters is non-volatile and not amenable to GC. Probably the reason for the lack of use of HPLC lies in the poor sensitivity of its most common detector (UV spectrophotometric) compared with GC detectors and the often demanding limits of detection required for environmental analysis, where sub-pg 1 limits of detection are the norm. 

Improved UV spectrophotometric detectors, together with automated (or on-line) sample enrichment and/or derivatisation and the development of low cost and highly sensitive detectors such as fluorescence and electrochemical (amperometric and coulometric) systems has meant that HPLC is becoming an increasingly attractive technique, particularly as the development of HPLC has been parallelled by an increasing use of chemicals such as pesticides that are designed to be short-lived in the environment this readiness to degrade often precludes the use of GC techniques as many of the pesticides nowadays are thermally liable. 

The spectrophotometric technique exploits the fact that when it binds to transferrin, AF+ replaces hydroxyl protons from two tyrosines, thus causing a change in the UV region of the spectrum (Fig. 10). Titration of the spectral change as a function of [AP+] at constant transferrin concentration allows the binding stoichiometry and stability constant to be measured. This approach has been used to study the interaction of a large number of metals [e.g., Nd +, Sm , Zn +, and Ga 61, 62,136)] with transferrin, including AP+ (33, 43, 136, 138) some of these metals would otherwise be spectroscopically silent. Such... 

The conventional spectrophotometric techniques (UV-visible, IR, NMR) are of limited use in structural determination of melanins. Consequently, an array of degradation techniques that yield easily identifiable, low molecular weight fragments has been developed. Many of these methods were developed in the 1950s and 1960s and are documented by Nicolaus (7). The degradation methods are classified as reductive, oxidative, pyrolytic, and photochemical, and recent findings are described below. 

The kinetics of Ca -transport, as studied by spectrophotometric techniques, show a fast and a slow phase the latter, lying in the range of seconds, can be identified with the translocation of Ca across the membrane ". Synchronous triggering of the ensemble of Ca -ATPase molecules within a oriented multilayer of membranes can be achieved by flash photolysis of caged ATP. The time-scale of the effective synchronization of the ensemble depends on the duration of the UV-light flash required to produce a sufficient quantity of ATP and is ultimately limited to the millisecond range due to the kinetics of the dark-reaction of the photolytic process. 

Le6n-Rodriguez, LMD and DA BasuH-Tobias (2005). Testing the possibility of using UV-vis spectrophotometric techniques to determine non-absorbing analytes by inclusion complex competition in cyclodextrins. Analytica Chimica Acta, 543(1-2), 282-290. 

Complexation of metal ions with the carboxyl resin Complexation of the carboxyl resin was carried out towards Fe(II), Fe(III), Co(II), Ni(II) and Cu(II) ions by a batch equilibration technique. A quantity (100 mg) of the resin was stirred in an aqueous metal salt solution (0.05 mol L , 50 mL) for 24 h. The complexed resins were collected by filtration and washed with distilled water to remove uncomplexed metal ions. The concentrations of the metal salt solutions were estimated by UV spectrophotometric methods. 

IR methods can be used to support a proposed intermediate in a reaction or to follow the incorporation of a distinctive functional group (e.g., CHO) onto a resin. IR is especially useful for surfaces such as pins or crowns where NMR techniques are not useful. High-quality IR spectra can be obtained from single beads. The UV spectrophotometric quantitative measurement of Fmoc release from derivatized amino groups is still a very common method for measuring loadings. Qualitative color tests are frequently used to follow reactions to assure completion. The Kaiser ninhy-drin test is the best known of these. An improved method for detection of secondary amines has been reported. ... 

The drawback of the spectrophotometric technique is that it is bound to ionization induced changes in UV spectra. It is difficult to guess whether a particular ionization will induce an change in UV spectra a priory. Practically, one combines this approach with an in silico tool like ACD pKa database, which predicts the number of ionizations and gives estimates of the pKa values. If the number of theoretical ionizations is lower than the number of ionizations obtained from the experimental data, one must reanalyze the sample using the potentiometric titration approach. 

It is necessary to choose a simple method to establish a proper and useful system to determine the quantity of active principle present in the fabric because of the need to modify or re-operate batches in order to apply similar amomits of microcapsules into the textile. For its simplicity and good accuracy, a spectrophotometric technique has been chosen using a Shimadzu UV-2401 model. 

The spectrophotometric technique is very useful for comparative purposes for a color classification system in a database and for the identification of individual organic or pearlescent (or interference) pigments or additives such as ultraviolet (UV)-absorbers batch-to-batch discrimination is also possible for analyzing the basecoats. MSP permits to measure absorption spectra in a given spectral range comprising typically 250-780 nm and to calculate... 

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