Instrument fittings

Monitoring of the environment to check exposure levels. Consider the installation of permanent instruments fitted with alarms. 

Spectrum 11.1, which was recorded on a 600 MHz instrument fitted with a cryoprobe, shows an example of a 15N HMBC. The compound in question is of the type shown in Structure 11.2. 

All equipment has limitations, for example, the amount of a substance it can detect or the accuracy with which it can make a measurement. If you attempt to make the equipment perform beyond its capabilities, it does not matter how carefully the equipment is operated, it will not be possible to get meaningful results. In terms of a particular instrument, fitness for purpose is interpreted as having appropriate performance capability to do the work required. This applies to all equipment, large or small. For example, a stirrer needs to perform the intended task satisfactorily while remaining essentially inert. There is a formal process for assessing the suitability of equipment to perform a given task - this is called Equipment Qualification or Equipment Validation. This is dealt with in Section 5.6.3. 

Compared to flame excitation, random fluctuations in the intensity of emitted radiation from samples excited by arc and spark discharges are considerable. For this reason instantaneous measurements are not sufficiently reliable for analytical purposes and it is necessary to measure integrated intensities over periods of up to several minutes. Modern instruments will be computer controlled and fitted with VDUs. Computer-based data handling will enable qualitative analysis by sequential examination of the spectrum for elemental lines. Peak integration may be used for quantitative analysis and peak overlay routines for comparisons with standard spectra, detection of interferences and their correction (Figure 8.4). Alternatively an instrument fitted with a poly-chromator and which has a number of fixed channels (ca. 30) enables simultaneous measurements to be made. Such instruments are called direct reading spectrometers. 

R. S. Bordoli, K. Howes, R. G. Vickers, R. H. Bateman, and D. J. Harvey. Matrix-Assisted Laser Desorption Mass Spectrometry on a Magnetic Sector Instrument Fitted with an Array Detector. Rapid Commun. Mass Spectrom., 8(1994) 585-589. 

To a limited extent, the type of results reported here could be obtained with a TEM instrument fitted with a STEM adapter, especially if a field-emission gun is used (10). We will refer here, however, only to the use of dedicated STEM instruments such as the HB5 or HB501 made by VG Microscopes Ltd. having a cold field emission gun. Most of the instruments of this type are specialized for microanalysis using EDS or ELS and some have been applied very effectively for compositional analysis and associated studies on catalyst particles, as reported elsewhere in this volume. 

Inexpensive, rugged fiber optics, equipped with every type of probes, make all these instruments amenable to processing measurements in real time. Recently, several manufacturers have been introducing wireless units that are smaller, more rugged, and faster than conventional spectrometers. Many process instruments from a decade ago were simply lab instruments fitted with explosion-proof enclosures and placed in factories. They are now being built specifically for the process environment. 

Naven T, Harvey D, Brown J, Critchley G (1997) Fragmentation of complex carbohydrates following ionization by matrix-assisted laser desorption with an instrument fitted with time-lag focusing. Rapid Commun Mass Spectrom 11 1681-1686... 

Figure 2-15 Schematic of FT -Raman instrumentation fitted with a bifurcated fiber optic interface. (Reproduced with permission from Ref. 26.)...

In addition, since many compounds have characteristic UV absorption profiles, multiwavelength analysis helped their identification. Because the instrument used was not capable of peak spectra acquisition, these authors had to perform multiple runs of the same sample at different wavelengths and draw absorbance profiles from the comparison of the peak heights in the individual electropherograms. More modem instrumentation fitted with diode array or fast-scanning UV detectors would facilitate analyses of this type. 

Infra-red Spectrophotometers can be single- or double-beam instruments, or both facilities may be available. In the double-beam mode, the beam of radiation passes through both the sample and a reference path (or reference cell). The use of a reference cell enables compensation to be made for unwanted absorption, e.g. from solvents. Alternatively, an instrument fitted with computing facilities can record and remember the solvent spectrum and then subtract it from a subsequent spectrum obtained with the same cell. 

We can see fipom this equation that absorbance is therefore proportional to the concentration level of absorbing species for given instrumental conditions. When however, the concentration and absorbance levels increase, the imperfections of the absorption process causes a deviation IVom the straight calibration line towards lower values. In order to obtain a precise measure of the concentration for a specimen situated in the non-linear response region, it is necessary to dilute it until an absorbance measurement in the linear domain is recorded. With state-of-the-art instruments fitted with micro-computers, a precise calibration can easily be established in a range of slight curvature. 

The in-situ electron microscopy studies presented here were performed either in a JEM 120 instrument fitted with an AGI gas reaction cell or a modified JEOL 200CX TEM/STEM microscope equipped with a custom designed environmental cell which accommodates a heating stage. With this latter instrument it is possible to obtain detailed information concerning the chemical state of the specimen under reaction conditions via in-situ electron diffraction analysis. 

UV-visible spectra were obtained using a Cary 118C spectrophotometer. Insertion probe mass spectra were obtained with a Dupont 21-49IB mass spectrometer, the FAB spectra with a VG MM-ZAB instrument, and the FD spectra with a JEOL DX-300 mass spectrometer. High pressure liquid chromatography measurements were made with a Waters instrument fitted with dual channel (405 and 546 nm) optical detection and using C18 analytical and semipreparative columns. 

The heat of adsorption of water vapor onto the surface of both polymorphs of the drug was measured under different RH conditions using an isothermal heat conduction microcalorimeter (Thermal Activity Monitor, TAM, Thermometric AB, Sweden). The integral heats of adsorption were measured using a TAM instrument fitted with a Thermometric RH perfusion ampoule (accessory Model 2255) adapted with Kalrez O-rings. The RH above the solid samples was controlled as originally described by Bakri (1993)... 

Apparatus Barber-Colman Model 10 or an E.I.R. instrument fitted with argon ionization detector. 

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