LIBS

The diastereomeric salts are separated and the individual enantiomers of the amine lib erated by treatment with a base... 

To increase the radiation absorption and ionization efficiency of IR YAG-Nd laser (wave length - 1064 nm) used in for analysis of synthetic oxide single crystals Bi Ge O, Li MoO, LiB O, the samples were grounded and pills of 010 mm were pressed and analyzed by LIMS EMAL-2 (Uki aine) ... 

Different analytical techniques are used for detection of the elemental composition of the solid samples. The simplest is direct detection of emission from the plasma of the ablated material formed above a sample surface. This technique is generally referred to as LIBS or LIPS (laser induced breakdown/plasma spectroscopy). Strong continuous background radiation from the hot plasma plume does not enable detection of atomic and ionic lines of specific elements during the first few hundred nanoseconds of plasma evolution. One can achieve a reasonable signal-to-noise ra-... 

The intrinsic drawback of LIBS is a short duration (less than a few hundreds microseconds) and strongly non-stationary conditions of a laser plume. Much higher sensitivity has been realized by transport of the ablated material into secondary atomic reservoirs such as a microwave-induced plasma (MIP) or an inductively coupled plasma (ICP). Owing to the much longer residence time of ablated atoms and ions in a stationary MIP (typically several ms compared with at most a hundred microseconds in a laser plume) and because of additional excitation of the radiating upper levels in the low pressure plasma, the line intensities of atoms and ions are greatly enhanced. Because of these factors the DLs of LA-MIP have been improved by one to two orders of magnitude compared with LIBS. 

The analytical capabilities of LIBS and LA-MIP-OES were recently noticeably improved by use of an advanced detection scheme based on an Echelle spectrometer combined with a high-sensitivity ICCD (intensified charge-coupled device) detector. 

The potential of LA-based techniques for depth profiling of coated and multilayer samples have been exemplified in recent publications. The depth profiling of the zinc-coated steels by LIBS has been demonstrated [4.242]. An XeCl excimer laser with 28 ns pulse duration and variable pulse energy was used for ablation. The emission of the laser plume was monitored by use of a Czerny-Turner grating spectrometer with a CCD two-dimensional detector. The dependence of the intensities of the Zn and Fe lines on the number of laser shots applied to the same spot was measured and the depth profile of Zn coating was constructed by using the estimated ablation rate per laser shot. To obtain the true Zn-Fe profile the measured intensities of both analytes were normalized to the sum of the line intensities. The LIBS profile thus obtained correlated very well with the GD-OES profile of the same sample. Both profiles are shown in Fig. 4.40. The ablation rate of approximately 8 nm shot ... 

Two detection techniques were tested, LIBS for the Cu-Ag-Si samples and LA-TOF-MS for the TiN-TiAlN samples. 

The depth profiling of the Cu-Ag-Si samples was performed with the laser beam focused on to the sample surface to the spot of approximately 30-40 pm. To obtain the best depth resolution the laser fluence was maintained near the 1 J cm level, close to the threshold of the LIBS detection scheme. The intensity profiles of Cu and Ag emission lines are shown in Fig. 4.43. The individual layers of Cu and Ag were defi-... 

The "soft" ablation of the TiN-TiAlN samples by the low fluence laser beam was performed by use of LA-TOF-MS. Because of the greater sensitivity of this technique compared with direct LIBS the lower laser fluence of approximately 0.3-0.4 J cm was used. One of the depth profiles, obtained by use of femtosecond LA-TOF-MS, is shown in Fig. 4.44. Each 280-nm-thick layer was ablated by approximately 20-25 pulses, which result in an average ablation rate of 11-14 nm pulse . The ablation rate was low enough for resolution of all layers. 

Spray solutions I and Ila are only stable for a short period of time and, hence, should always be freshly made up [11], spray solution lib can be stored for several weeks in the refrigerator... 

The chromatograms are freed from mobile phase and then sprayed with spray solution I until the layer begins to be transparent, then dried in a stream of cold air for 10 min and finally sprayed again to the start of transparency this time with spray solution Ila or lib and dried in a stream of warm air. 

Note Note that the diazotization of primary aromatic amines can also be achieved by placing the chromatogram for 3 — 5 min in a twin-trough chamber containing nitrous fumes (fume cupboard ). The fumes are produced in the empty trough of the chamber by addition of 25% hydrochloric acid to a 20% sodium nitrite solution [2, 4], iV-(l-Naphthyl)ethylenediamine can be replaced in the reagent by a- or -naphthol [10, 14], but this reduces the sensitivity of detection [2]. Spray solutions Ila and lib can also be used as dipping solutions. 

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