Infrared method

Infrared Methods Commercial instrumentation for recording infrared radiation has been available for some years and has been explored by the electrical power industry in the UK for assessing corrosion in boiler tubes at power-station shut-down. An external heal source is played onto the outside of boiler tubes at the same time as cold water is circulated inside the tubes. Hot spots due to poor heat conductivity caused by excessive corrosion product indicated areas of high corrosion. 

Another difficulty with the infrared method is that of determining the band center with sufficient accuracy in the presence of the fine structure or band envelopes due to the overall rotation. Even when high resolution equipment is used so that the separate rotation lines are resolved, it is by no means always a simple problem to identify these lines with certainty so that the band center can be unambiguously determined. The final difficulty is one common to almost all methods and that is the effect of the shape of the potential barrier. The infrared method has the advantage that it is applicable to many molecules for which some of the other methods are not suitable. However, in some of these cases especially, barrier shapes are likely to be more complicated than the simple cosine form usually assumed, and, when this complication occurs, there is a corresponding uncertainty in the height of the potential barrier as determined from the infrared torsional frequencies. In especially favorable cases, it may be possible to observe so-called hot bands i.e., v = 1 to v = 2, 2 to 3, etc. This would add information about the shape of the barrier. 

Ideal localized adsorption, 5, 10 Infrared method, 373, 374 Initiators of polymerization, 148 Intramolecular London energies, 74, 78 Iodine molecule intramolecular London energy, 78... 

It can be readily seen from the above discussion that a simplistic version of the polarization modulation method for using Fourier Transform Infrared method would be to say that if one subtracted the message obtained from the vertical light from that obtained from the parallel light, the result will be information from the surface only. The relevant equation is shown below. 

Infrared Methods for Gaseous Measurements Theory and Practice, edited by Joda Wormhoudt... 

Madejova J, Komadel P. Baseline studies of the clay minerals society source clays infrared methods. Clays Clay Miner. 2001 49 410-432. 

When the reaction temperature of step one increases, the total oxidant concentration in the off-gas is >6 mg m-3, but this depends on capacity and hypochlorite concentration. Careful analysis with infrared methods demonstrated that this total oxidant concentration was derived from chlorine dioxide. Measurements of the concentrations between steps one and two showed that concentrations were higher than in the off-gas and that hypochlorous acid (HOC1) was also found, which was totally absent in the off-gas. 

There is a further problem regarding a value for the resonance parameter of NO. The infrared method (Section V.A) yields a rri]K value of 0.07154, cf 0.31 or 0.25 above. 

Method wastewater 5520F Infrared methods hydrocarbons. Not suitable for low-boiling fractions. May be used in conjunction with Method B, D, or E. 

Gravimetric or infrared methods are often preferred for high-molecular-weight samples. These methods can even be used as a check on gas chromatographic data if it is suspected that high-molecular-weight hydrocarbons are present but are not being detected. 

Infrared methods measure the absorbance of the C-H bond and most methods typically measure the absorbance at a single frequency (usually, 2930 cm Q that corresponds to the stretching of aliphatic methylene (CH2) groups. Some methods use multiple frequencies, including 2960 cm (CH3 groups) and 2900 to 3000 cm (aromatic C-H bonds). 

Therefore, for infrared spectroscopic methods, the total petroleum hydrocarbons comprise any chemicals extracted by a solvent that are not removed by silica gel and can be detected by infrared spectroscopy at a specified wavelength. The primary advantage of the infrared-based methods is that they are simple and rapid. Detection limits (e.g., for EPA 418.1) are approximately 1 mg/L in water and 10 mg/kg in soil. However, the infrared method(s) often suffer from poor accuracy and precision, especially for heterogeneous soil samples. Also, the infrared methods give no information on the type of fuel present in the sample, and there is little, often no information about the presence or absence of toxic molecules, and no specific information about potential risk associated with the contamination. 

The infrared method that has been used most frequently (EPA 418.1) is appropriate only for water samples. A separatory funnel liquid-liquid extraction technique is used to extiact hydrocarbons from the water. A method (EPA 5520D) using a Soxhlet extraction technique is suitable for sludge. This extiaction is frequently used to adapt the method (EPA 418.1) to soil samples. An infrared-based supercritical fluid extraction method for diesel range contamination (EPA 3560) is available. 

In summary, infrared methods are prone to interferences (positive bias) from nonpetroleum sources since many organic compounds have some type of alkyl group associated with them, whether petroleum-derived or not. 

For the iodate method, chlorine in concentrations below 1 mass % does not interfere. The isoprene rubber method can tolerate somewhat higher levels. Nitrogen when present above 0.1 mass % may interfere with the iodate method, the extent depending on the types of nitrogen compounds as well as the combustion conditions. It does not interfere in the infrared method. The alkali and alkaline earth metals, zinc, potassium, and lead do not interfere with either method. 

I.R. Last and K.A. Prebble, Suitabihty of near-infrared methods for the determination of moistnre in a freeze-dried injection prodnct containing different amonnts of the active ingredient, J. Pharm. Biomed. Anal., 11(11/12), 1071-1076 (1993). 

M. Blanco, J. Coello, H. Iturriaga, S. Maspoch and N. Pou, Development and validation of a near infrared method for the analytical control of a pharmaceutical preparation in three steps of the manufacturing process, Fresenins J. Anal. Chem., 368, 534-539 (2000). 

Many transition metal alkyls react with carbon monoxide to give acyl compounds. In all these cases the acyl derivatives can be detected at least by infrared methods and in most cases isolated. Molybdenum, manganese, rhenium, iron, cobalt, rhodium, nickel, palladium, and platinum alkyls, Grignard reagents, and boranes, all react with carbon monoxide, and one can explain the products from these on the basis of carbon monoxide inserting into the metal alkyl. 

DETERMINATION of EGDN in MIXTURES WITH NG by INFRARED METHOD. EGDN is often used in admixture with NG in expls, as the mixture possesses the generally desirable characteristic of having a lower freezing point than either NG or EGDN alone. 

It appears there would be several advantages in using the proposed infrared method analyses could be performed much faster using the IR method. An IR scan takes 45 seconds versus -16 minutes by the NI0SH GC method. The IR method is adapted to charcoal tubes sampled by current recommended techniques. The majority of laboratories have infrared spectrometers and the simplest of models will do utilization of the IR method would relieve pressure of the heavily used gas chromatographs. The... 

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