Reflection instrumentation

The data plot along a line of dope 0.5, reflecting instrumental mass fractionation of 7%famu. The proper correction for is indicated by the terrestrial plagioclase... 

Procedures. The light reflectance instrument was turned on 30 min prior to initiating reflectance observations. The sensitivity switch was set in the low position. The combination visible light emitter-reflectance detector was positioned vertically the active end of the detector faced upward. The sample cup was a glass cylindrical cuvette with optically flat bottom. A constant mass of 165 g (brass slug) was placed on top... 

T. Feam, Misuse of ridge regression in the calibration of near-infrared reflectance instruments, Appl. Statistics, 32, 73-79 (1983). 

The resolution of reflection instruments such as the one described here may be tested by imaging a specimen with a fine grating ruled on it. Figure 2.6 shows an image of a grating with a period of 0.8 pm at 2.0 GHz. At lower frequencies the pattern was not resolved at all (cf. Hoppe and Bereiter-Hahn 1985), but at 1.7 GHz, and above it can be seen quite well. The enormous amount of creative research that has gone into making acoustic microscopy with this kind of resolution routinely possible should not be underestimated (Jipson and Quate 1978). Chapter 3 considers the factors that determine and limit that resolution. 

Many diffuse-reflectance instruments are available. Some employ several interference filters to provide narrow bands of radiation. Others are equipped with grating monochromators. Ordinarily, calibration is often a stringent requirement as samples must be acquired of the material for analysis that contain the range of analyte concentrations likely to be encountered. It may be useful to grind solid samples to a reproducible particle size. Equations are developed and used for the analysis. Once method development has been completed and validated, solid samples can be analyzed in a few minutes. Accuracy and precision are reported to be of 1 to 2% relative. 

Fearn, T., Misuse of Ridge Regression in the Calibration of Near-Infrared Reflectance Instruments Appl. Statistics 1983, 32, 73-79. 

The technique of FT-IR internal ATR has been developed to the point that, today, ATR mirror lenses are available for an IR microscope. Furthermore, a newly developed, dedicated diamond internal reflection instrument, the lUuminatIR (Smith s Detection, Shelton, CT, USA) has now joined the ranks of microspectroscopy. This instrument incorporates a small, horizontally mounted diamond, on the surface of which is placed the material to be examined. In this way, the material is in optical contact with the diamond, and is held in place by a shaft pressing down from above. In this case, the radiation enters from beneath the instrument at an appropriate angle, and internally reflected rays are subsequently collected. The specimen is illuminated from beneath with a near-IR source that is detected and displayed on a video screen. With this optical arrangement, it is possible to locate a particular part of the material in the field of view and to interrogate it Such an arrangement is particularly user friendly, and indeed it is mostly used by... 

In most GC-TOF-MS instruments, an appropriate voltage pulse is applied to accelerate the ions in the direction orthogonal to their initial flight direction. In such oa-TOF-MS a nearly parallel ion beam ideally has no velocity spread, and the finite spatial spread is corrected with a linear or reflecting instrument geometry. Noise-free mass spectra are produced within a very short time (a few milliseconds). Only TOF-MS instruments have the capability required to detect peaks in GC GC since the half widths of the peaks eluting from the second column are of the order of 200 msec. Selecting the proper scan rate is essential since an increase in the acquisition speed... 

A common design feature of all commercial diffuse-reflectance instruments is the integrating sphere, which permits the collection of reflected light. Many of the... 

Structured for control, either of natural or organizational processes and ends, and thereby they both reflect instrumental rationality ... 

A linear TOF analyzer can not provide any MS/MS information but a reflection instrument can provide fragment ion spectra of metastable ions that fragment (either spontaneously or via laser photodissodation) while in flight between the final acceleration grid and the reflectron entrance (Weickhardt 1996). However, this post-source decay technique has never been used for quantitative trace analysis. 

Measuring Temperature. At first glance, it would appear that obtaining air temperatures would be relatively simple. After all, thermometers have been around since 1714 (Fahrenheit scale) and 1742 (Celsius scale). However, accurate temperature measurements require a white (high-reflectivity) instrument shelter with louvered sides for ventilation, placed where it will not receive direct sunlight. The standard height for the thermometer is 5 feet above the ground. 

Fio. 18. Diffuse/directional reflectance instrument with source... 

This review is limited to reflectometers based on specular conic mirrors and it includes several unanticipated results. To our knowledge, this chapter represents the first comprehensive review of such devices. Previous reviews of reflectance instrumentation contain only a limited discussion of conic mirror devices (6, 7). It has been prompted by new developments that expand the scope of conic mirrors used for reflectometry. During the past decade, inexpensive PC- and workstation-based raytracing programs have become available that allow one to easily model the performance of both conic mirror and integrating sphere reflectometers. In this review we... 

With the rise of NIR reflection instrumentation and chemometric data treatments for rapid, direct control measurements, the interest in NIR for industrial applications became greater again. Process control applications, either rapid laboratory measurements or real-time online analyses, benefited the most from the new technologies. Older applications, such as hydroxyl number, polymer properties, water measurement, and fuel analyses have been revisited. 

In a study published by Park et al. (36), 119 Af. longissimus thoracis muscles were measured with a NIR reflectance instrument (1100-2500 nm) and a Warner-Bratzler shear force instrument for tenderness. The data were split into a calibration set (80 samples) and a test set (39 samples). The test set gave SEP = 1.3 kg and... 

P. C. Williams, D. C. Sobering. Comparison of commercial near inliared transmittance and reflectance instruments for analysis of whole grains and seeds. J Near Infrared Spectroscopy, 1 25-32, 1993. 

The increasing demands of quality control in the dairy industry requires the development of instm-ments for rapid determination of quality-defining parameters. NIR reflectance instruments have the potential to provide these benefits. The main problem of NIRA is to And a representative sample set to calibrate the NIRA instrument. Sample preparation plays an important role. Particle size, homogeneity, temperature, and presentation of the sample have to be standardized. 

Several accessories are available for the higher end spectrophotometers, which enable performing different modalities of measurement on different types of samples, as for example, solid films, liquid solutions, powders, etc. Some of the modalities commonly available are transmittance, diffuse transmittance, diffuse and specular reflectance, and variable angle specular reflectance. Instruments... 

Near-infrared instruments of the UV-VIS-NIR type have become commercially available about 1955 with applications for agricultural commodities. Instruments designed specifically for measuring NIR energy reflected from solids have been commercially available as from 1971 [214] the development of these devices was pioneered by Norris [215]. The first successful uses of modem MRS were in the 1100-2500 nm region. NIR instrumentation is now extremely varied from UV-VIS-NIR to FTIR instm-ments, NIR reflectance instruments, PAS technology, on-line and portable analysers. 

Chapter 8 Product Ion Spectra from Reflection Instruments... 

Reflectance NIR cells allow rapid analysis of many different materials, but with some loss in precision over transmission measurement. Walling and Dabney have demonstrated the use of a conventional reflectance instrument to measure active agent content and functionality of an alcohol sulfate, as well as concentration of an additive (12). For a well-defined system, the determination of several parameters requires only a very few minutes. A reflectance NIR instrument is also suitable for quality control monitoring of surfactants and other components of powdered detergent formulations (13). NIR reflectance has even been demonstrated for detecting residues of an unspecified detergent on a stainless steel surface, with a detection limit in the 1 pg/cm range and reasonable hnearity down to about the 15 pg/cm level (14). The patent literature describes the use of NIR reflectance to determine the amount of water film left behind on a quartz tube after a surfactant solution has contacted the exterior of the tube. Within limits, the mass of the film is related to the surfactant concentration of the solution (15). 

---