Spectrophotometric analysis automated

An area worthy of study is the development of systems of increasing sample throughput beyond the single column operation. Scott has introduced a prototype multicolumn system based on the centrifugal analyzer principle (53). In this set-up a series of LC colimns is rotated on a disc, with sample delivery at the center of the disc and elution and spectrophotometric analysis on the outside. He has suggested using affinity columns for rapid serum protein analysis by this approach. Of course, other principles, such as segmented flow, could be envisioned in an automated LC system as well. Undoubtedly, we can expect to see the availability of such systems in the next few years. 

Timofeeva, L, I. Khubaibullin, M. Kamencev, A. Moskvin, and A. Bulatov. 2015. Automated procedute for determination of ammonia in concrete with headspace single-dtop micro-exttaction by stepwise injection spectrophotometric analysis. Talanta 133 34-37. 

The advantages of atomic absorption techniques as opposed to spectrophotometric analysis for the determination of metals are that the former are amenable to multielement analysis and can be automated. There is some evidence that ashing polymers in silica crucibles rather than platinum can lead to up to 10% losses of elements such as copper by adsorption within the silica matrix to produce a compound that is not extractible by subsequent acid leaching. This does not occur when ashing is carried out in platinum. If silica crucibles are used then a magnesium oxide ashing aid should be employed as is demonstrated in the method for determining down to 0.1 ppm of copper in polyolefins, (Method 72). 

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],... 

The transfer of an automated analysis from the laboratory to the plant will often require special precautions for instance, while turbidities in a process stream can cause a loss of selective absorptivity in a spectrophotometric measurement, in potentiometric methods fouling of the electrodes, potential leakage in metal containers or tubing and loss of signal in remote control may occur (see later). 

Vukjovic et al.199 recently proposed a simple, fast, sensitive, and low-cost procedure based on solid phase spectrophotometric (SPS) and multicomponent analysis by multiple linear regression (MA) to determine traces of heavy metals in pharmaceuticals. Other spectroscopic techniques employed for high-throughput pharmaceutical analysis include laser-induced breakdown spectroscopy (LIBS),200 201 fluorescence spectroscopy,202 204 diffusive reflectance spectroscopy,205 laser-based nephelometry,206 automated polarized light microscopy,207 and laser diffraction and image analysis.208... 

Flow injection analysis is based on the injection of a liquid sample into a continuously flowing liquid carrier stream, where it is usually made to react to give reaction products that may be detected. FIA offers the possibility in an on-line manifold of sample handling including separation, preconcentration, masking and color reaction, and even microwave dissolution, all of which can be readily automated. The most common advantages of FIA include reduced manpower cost of laboratory operations, increased sample throughput, improved precision of results, reduced sample volumes, and the elimination of many interferences. Fully automated flow injection analysers are based on spectrophotometric detection but are readily adapted as sample preparation units for atomic spectrometric techniques. Flow injection as a sample introduction technique has been discussed previously, whereas here its full potential is briefly surveyed. In addition to a few books on FIA [168,169], several critical reviews of FIA methods for FAAS, GF AAS, and ICP-AES methods have been published [170,171]. 

The concentration of lithium in serum, plasma, urine, or other body fluids has been determined by flame emission photometry, atomic absorption spectrometry, or electro-chemically using an ion-selective electrode. Serum analysis, the most useful specimen for lithium monitoring, is most commonly quantified by automated spectrophotometric assay. 

ISO/TR 11905-2). Another method oxidizes nitrogen forms into nitrates which can be then estimated (NF EN ISO 11905-1). Lastly, an ISO/CD 29441 method, under development, uses UV digestion, followed by flow injection analysis (FIA), continuous flow analysis (CFA) with spectrophotometric detection, and allows automation of the method. 

G. J. Moody, G. S. Sanghera, and J. D. R. Thomas, Modified Platinum Wire Glucose Oxidase Amperometric Electrode. Analyst, 111 (1986) 1235. M. A. Koupparis and P. I. Anagnostopoulou, Automated Flow Injection Spectrophotometric Determination of Zinc Using Zincon Applications to Analysis of Waters, Alloys and Insulin Formations. Analyst, 111 (1986) 1311. 

Decristoforo, G., Flow-Injection Analysis for Automated Determination of yS-Lactams Using Immobilized Enzyme Reactors with Thermistors or Ultraviolet Spectrophotometric Detection , in Methods in Enzymology Voi. 137, Colowick, S. P., Kaplan, N. O., Mosbach, K. (eds.) San Diego Academic Press, 1988, pp. 197-217. 

The peroxide method has proven to be the most useful for this purpose, owing to the high acidity of the medium in which the reaction is conducted. Interferences are observed only in the presence of V, Mo, or F, but these species are not normally present in U.S.P. grade titanium dioxide. In the spectrophotometric assay method, the absorption maximum at 410 nm is used to determine the titanium concentration after the oxide is dissolved [39]. The spectrophotometric endpoint of the peroxide method has been combined with flow injection analysis techniques to yield an automated procedure [40]. 

The substrate peptide NRCSQGSCWN is synthesized from Primm s.r.l. Italia using a Shimadzu PSSM8 automated peptide synthesizer. The purified peptide is eluted in a single peak by HPLC analysis and stored at —20° in the elution buffer (30% acetonitrile in 0.1% TEA). The peptide concentration is determined spectrophotometrically using an adsorption coefficient of 56(X) M cm at 278 nm. 

A wide range of spectrophotometric and fluorometric methods have been developed that are extremely sensitive and are easily adaptable for automated analysis. The usefulness of these methods can be reduced because of a nonspecific nature and interferences caused by soluble organic material. 

The analysis of phosphorus in waters has historically been based on the photometric measurement of 12-phosphomolybdate or the phosphomolybdenum blue species, which are produced when phosphomolybdate is reduced. The majority of manual and automated methods of phosphate determination are based on the spectrophotometric determination of phosphorus as phosphomolybdenum blue, i.e.. 

Other alternative spectrophotometric method of widespread use for sulfate monitoring is the dimethylsulphonazo(III) (DMSA(III)) approach. It has been automated in FIA [5] and SIA [6] and applied to the analysis of natural and residual waters. This method involves the reaction of sulfate with barium-dimethylsulphonazo(ni) complex, Ba-DMSA(111), displacing Ba from the complex and forming DMSA(III). 

Few applications based on flow analysis can be found for the automated and direct determination of gaseous sulfur dioxide [8,9] or hydrogen sulfide [10] in atmospheric samples. This is mainly due to the difficulty encountered in the online sampling of gases, which has been partially overcome with the use of chromatomembrane cells or tubular and planar permeation denuders and diffusion cells for the collection of the analyte from air into an absorbing solution and its introduction into the flow manifold, followed by conductivity, potentiometric, piezoelectric, or spectrophotometric detection. 

Besides specific radionuclide determinations, screening methods to determine radioactive elements levels are very useful tools prior to laborious and expensive analytical protocols allowing isotopic analysis. These screening tools could replace gross alpha and gross beta index providing information about total element concentration. In order to develop fully automated methodologies based on inexpensive instruments, and consequently affordable for any routine laboratory, spectrophotometric detection can be used for this purpose. 

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