Spectroscopy-11-01-2010

In a quantitative analysis by laser-induced breakdown spectroscopy (LIBS), the minimization of white noise is a very important problem. The LIBS measurement was carried out to derive an optimized measurement condition with minimum white noise at low pressure. The thinner the ambient gas becomes, the larger the size of the plasma sphere becomes. The growth of the plasma started at a gas pressure of 15.0 Torr, and the plasma was slightly distinguishable by the inner sphere and the outer sphere at a pressure of 900 mTorr. It was clearly distinguishable at a pressure of 600 mTorr, and the sphere size was about 20.0 mm at this pressure. The measurement of the plasma was taken at a 6.0-mm distance, in the direction of a plasma sphere, from a sample. This location belongs to the outer sphere region in the plasma. Four Nd and Cu mixed samples and five Sm and Cu mixed samples that had mutually different components were prepared in an arc melting furnace at 3000 ?C, starting with a homogeneously mixed powder form of..

Fluorescence spectroscopy is useful for the analysis of a broad range of organic compounds. A subset of fluorescence spectroscopy is lifetime fluorescence, within which a subsubset is frequency-domain lifetime fluorescence.

It is just over two years since USP <1058> on Analytical Instrument Qualification (AIQ) became effective. To coincide with the American Association of Pharmaceutical Scientists (AAPS) Meeting in New Orleans this month where a roundtable discussion on the subject will be held, here are my views.

ICP-MS is powerful technique capable of measuring very low levels in a wide variety of sample types, limited only by cleanliness and the presence of interences. This article will examine the types of interferences that are encountered and various ways of dealing with them using a quadrupole ICP-MS instrument: mathematical correction equations, matrix removal, and cell-based ICP-MS. The strengths and limitations of each method will be discussed.

Two disparate paths can lead to increased performance in mass spectrometric analysis. Improvements in fundamental parameters of instrument performance can be achieved through optimized interface design, improvements in ion source and analyzer efficiency, and enhanced detector performance. Increased performance also can be achieved through a better sampling protocol, or through better chromatographic performance. Alternatively, because we are clever chemists, we might choose to alter the chemical and physical characteristics of the sample itself, however collected, to achieve a more complete transport through the sample purification/selection/chromatographic process, and to achieve better ionization through enhanced sensitivity or selectivity. This second path involves a change in either the physical or chemical form of the sample. A change in the chemical form of the sample is sample derivatization, which is the focus of this column.

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The measurement of metals in used engine oils provides valuable information about the engine and the state of the lubricant, information that can be used to increase the efficiency of the equipment in which the engine resides and lower the cost of maintenance. Table I lists the metals that are typically of interest and their sources (1–4). The presence of wear metals is important because it can pinpoint a specific component for maintenance. For example, copper is an indication of bearing wear, while lead can come from bushings and chromium from piston rings and seals. Other elements such as calcium, magnesium, and zinc are added to the oil to produce a "soap" to protect engine components. So it is important to ascertain that these metals remain at an optimum concentration. Also, dirt can contaminate the oil, which would be evidenced by the presence of elements like silicon and sodium.

Click the title above to open the Spectroscopy November 2010 regular issue, Vol 25 No 11, in an interactive PDF format.