A simple homemade spectrophotometer

A simple portable spectrophotometer was constructed and used to perform analytical experiments. The developed model uses available tools and materials such as light emitting diode lamps, compact discs, plastic and cardboard boxes and a cell phone camera to build a design that illustrates the major components of spectrophotometers. The spectra of serial concentrations of KMnO₄ (50?600 μM) were recorded and the values of absorbance were extracted at λ_max to build the calibration curve. A linear relationship between the concentration and absorbance was obtained with the coefficient of determination 0.994. The model was also utilized to study the spectra of KMnO₄, phenolphthalein and bromothymol blue in comparison with a Shimadzu UV-1800 spectrophotometer as a reference instrument. In spite of the differences in the observed spectra, the recorded λ_max were almost identical to those measured by the developed model. The model was successfully used to determine the concentration of sodium alendronate through ligand-exchange complexation with ferric salicylate.     

A Zeeman-effect based scatter correction system for non-dispersive atomic fluorescence spectrometry

A Zeeman-effect based method of correcting for the scattering of source radiation in atomic fluorescence spectrometry (AFS) is described. The magnetic field is applied to the atomization cell in a direction transverse to the source and detected beams. Both polarized and field modulated Zeeman AFS are examined. Fluorescence signals corrected for scattering are derived from differences in the measured light intensities caused by changes in the incident light polarization and/or field intensity.Results are given for the determination of Cd in an Al matrix, and for Cd, Hg, and Zn in NBS fly ash, orchard leaves, and river sediment. The scatter corrected values obtained by this method are in agreement with certified values.     

Photometric titrations-XII A full-immersion spectrophotometer

A design for a photometric titration apparatus is described which includes facilities for variable path-length, zero suppression and scale expansion. The instrument may also be used as a simple spectrophotometer.     

A new method for the atomic-absorption determination of lead blended as lead alkyls in motor spirit

The total lead present as tetraethyl-lead (TEL) and tetramethyl-lead (TML) in motor spirit is determined by atomic-absorption spectrometry after decomposition by extraction with a mixture of mercaptoacetic acid and nitrous acid in the presence of hydrochloric acid.     

A continuum-source single-detector resonance-monochromator for atomic-absorption spectrometry

The detector, for atomic-absorption spectrometry, consists of a furnace into which a constant concentration of the element to be analysed is atomized. Resonance radiation is excited by the light from a xenon-arc lamp which traverses the burner flame. The resonance radiation passes through a tunable grating filter and is measured with a photomultiplier.     

Stark- and Zeeman-effect of resonance lines of Ba I

Laserspectroscopic investigations were performed on a collimated atomic beam of barium (natural isotope abundance). The metastable ground levels (³D_1,2,3 and ¹D₂) of the investigated lines were populated by a discharge burning in barium vapour directly in front of the oven hole. We could investigate 14 spectral lines between 580 and 690 nm. The tensor polarizabilities of the upper and the lower level as well as the differences in the scalar polarizabilities could be determined. Spectra in magnetic fields up to 0.03 Tesla showed no deviation from the pattern resulting from a simple Russell-Sounders coupling.     

A new type of pH-sensitive phospholipid

We describe the synthesis and characterization of a type of pH-sensitive pentaerythritol phospholipids, using a trialkoxybenzylidene acetal as the acid-labile moiety. This lipid was prepared by an eight-step synthesis via a latentiation strategy. Liposomes were prepared via the thin film extrusion method. The changes of liposomal sizes were measured by dynamic light scattering. Content release rates of the liposomes as a function of pH were monitored by using a calcein fluorescence dequenching assay. These results indicated that this new liposomal system was capable of releasing its contents under mildly acidic conditions. At last, in vitro cytotoxicity was assayed against three cell lines, suggesting this type of phospholipids was low toxic.     

A new type of corrin synthesis

Work towards a synthesis of vitamin B₁₂ has inspired a new type of corrin synthesis. The key step is a light-induced 1,16-hydrogen transfer leading to an antarafacial (π→σ)-cycloisomerization of a seco-corrinoid metal complex. The construction of the seco-corrinoid ligand system is achieved by coupling monocyclic ring precursors in their enamide or enamine form through the methods of sulfide-contraction via oxidative coupling and of iminoester-enamine condensation.     

A new type of biomechanical driver

Segregation of chromosomes and their distribution to opposite ends of the cell is mediated by a mitotic spindle comprised of microtubules (polymeric structures). The forces produced by depolymerizing microtubules, responsible for chromosome motility, were measured, and the mechanochemical mechanism of their development was demonstrated.     

A continuous-dilution calibration technique for flame atomic-absorption spectrophotometry

Calibration in atomic-absorption spectrometry is achieved by means of a concentrationgradient chamber using a single concentrated standard solution. Calibration is rapid and extends over the entire working concentration range of the analyte, irrespective of the shape of the conventionally obtained calibration curve. No curve-fitting approximations are involved. With well-designed apparatus, deviations are less than 1%.     

A new catalytic hetero-Heck type reaction

Unsaturated N-chloroamines have been found to cyclise under palladium-catalysis in good yield, the proposed mechanism includes an oxidative addition of the chloroamine to Pd(0), thus opening a new entry to the amides of the late transition metals.     

A new type of abnormal reimer-tiemann reaction

The treatment of l, 2, 3, 4, 4a, 9b-hexahydro-3, 8-dihydroxy-7-methoxy-9b-(2'-methoxyethyl)dibenzofuran with chloroform and aqueous potassium hydroxide under conventional Reimer-Tiemann reaction conditions resulted in the replacement of the 7-methoxyl group by a carbaldehyde one. A choice between alternative pathways for this novel displacement has been facilitated by examination of the behaviour of the corresponding 7-trideuteromethoxy compound. Dichlorocarbene attack at position 7 rather than at the unsubstituted position 9 is shown to be due to steric encumbrance at the latter site.     

A new type of calixarene: octahydroxypyridin

A new type of calixarene has been synthesised. Like resorcinol and a number of resorcinol derivatives, 2,6-dihydroxypyridine has been proven to form cyclic tetramers in moderate yields with a number of aliphatic and two aromatic aldehydes in acidic media. The problem of the formation of configurational isomers can be reduced by increasing the reaction temperature and time. With electron-rich aromatic aldehydes, 2,6-dihydroxypyridine unexpectedly yields deep-coloured acyclic quinoid systems. The octahydroxypyridine[4]arenes may have a high potential as receptors for molecular recognition and self organisation.