Buying a spectrometer

The following companies supply FTIR spectrometers. Inclusion in or omission from this list does not, of course, imply any endorsement or criticism of a particular product. 

Bio-Rad, Bomem, Bruker, Laser-Precision (Analect), Mattson, Midac, Nicolet, Perkin-Elmer, Shimadzu. 

A prospective purchaser of a low-cost, worktop FTIR has a bewildering variety of makes and models to choose from. The following are some recommendations which may be useful in deciding which spectrometer is most suitable. 

Performance. Modern FTIR spectrometers, even the least expensive types, generally offer a level of performance that is more than adequate for simple sampling techniques— such as KBr discs or mulls—and will normally give excellent results with more sophisticated accessories such as ATR or diffuse reflectance. Only the most demanding accessories (microscopes or photoacoustic devices) or technically difficult experiments (step-scanning or high-speed and time-resolved work) require more expensive machines. The prospective customer who requires FTIR for raw material confirmation and occasional forensic analysis can be confident that whatever machine is chosen should be up to the job. 

However, there are differences between products and suppliers, and these differences can be grouped into three categories  

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You seldom have much choice about this software. When you buy a spectrometer you will get some software from the manufacturer. The big manufacturers are Bruker, Varian and JEOL. Their software is called Topspin, VNMRJ and Delta respectively. These pieces of software are quite complex as they have to perform all the spectrometer control as well as processing and some simulation. That said, all manufacturers have improved their software to make it more user-friendly in recent times and it is not the challenging beast that it used to be. 

To some of us it can unexpectedly happen that we are faced with the task of having to buy a mass spectrometer, eventually for ourselves or on behalf of someone else. References to certain commercial instruments made in this chapter were in no way intended to preclude such a 100,000-600,000 decision. The below guide may be useful in selecting an instrument that meets your requirements best ... 

Due to the high sensitivity it is favorably to couple a nanoHPLC to an ESI-source. As mass spectrometers are concentration dependent detectors, the sensitivity of an instrumental setup is mostly determined by the peptide concentration of the eluate but not by the peptide amount. Thus a nanocolumn with a flow rate of 300 nL/min provides an about thousand times higher sensitivity than a microbore column with a flow rate of 300 (xL/min. As an alternative to buying a nanoHPLC system it is also possible to use a relatively inexpensive flow splitter after the pump and before the injection valve and the column. Thereby the flow rate can be reduced to use a capillary column (flow rate 4 (xL/min) on an analytical HPLC system or a nanocolumn on a capillary HPLC system. Instead of a flow-splitter it is preferred to couple a nanoHPLC to an ESI-source. Thereby, the flow rate is split according to the column backpressure, i.e., mostly the column volumes if the same packing materials are used. However, these low-cost setups are less reliable than a nanoHPLC and the reproducibility is worse. 

We now consider some practical aspects of buying a commercial spectrometer or components. Much of this is common sense as you would invoke when purchasing a house or an automobile. 

This section points out the existence, apparently not well known in NMR circles, of a middle ground between developing a computer interface from scratch and buying a data system already interfaced to the spectrometer. We have assembled such an interface using CAMAC modules which are extensively used in particle physics experiments and we give a brief description here as an example of what is possible (Fukushima and Swenson, 1980). 

The process of buying a mass spectrometer consists of a number of consecutive steps (1) define the objectives in both broad and specific terms (2) determine which instrument and data system would be ideal/adequate to attain the objectives (use the literature and contact experts) (3) establish the maximum budget available (4) contact several MS manufacturers and ask for detailed proposals, including prices, performance values (general as well as with respect to the stated objectives), warranties, delivery, and other pertinent information, including contact information for other users of similar instruments and (5) arrange for appropriate demonstration in the manufacturer s applications laboratories. 

What Should You Look for When Buying a Mass Spectrometer ... 

It is unwise to buy a mass spectrometer before testing it All mass spectrometer manufacturers welcome potential buyers to try products before they buy them. It is imperative when testing a device to supply appropriate samples, standard solutes, and matrix extracts doped with analytes because results among standard solutions and matrix extracts may differ significantly. It is essential to create conditions as close as possible to those where the equipment will be used. Sample preparation is not the manufacturer s task. Sales representatives are not always equipped for or knowledgeable about sample preparation. 

The problems associated with the study of solids and the means to overcome them having been outlined, it is of value to the prospective user of n.m.r.in catalysis to be aware of the compromises which should be considered before embarking on the purchase of equipment. Although the general trend is towards buying n.m.r. spectrometers already equipped for solid-state studies, it is feasible to modify conventional liquid-state spectrometers.35 Some additional hardware is required and a good knowledge of electronics. Details of the spectrometer itself have been described.1,36 -40 A few comments are merited on each of the essential features required to be able to perform the majority of the studies described in this review. 

This process of setting a window to limit the range of frequencies admitted to the receiving system is called narrowbanding and can be accomplished in several ways. For fixed frequency operation, it is easy to construct a narrow-band amplifier with a window centered at the desired carrier frequency. This is frequently done, even in commercial spectrometers, and is sufficient if either no other nuclei need to be examined at that field intensity or if no frequency dependent parameters need to be measured. On the other hand, a variable frequency operation can be implemented in several ways. The first is to make (or buy) as many fixed frequency units as needed. This is a simple solution if there is no need for a continuous frequency range and if only a few discrete frequencies are adequate for one s needs. Another is to make the spectrometer tunable, but to keep it a narrow band device. This means that each transmitter and receiver section has to be made tunable, and it is a fairly complicated operation. (The third way is to make it tunable but by a technique known as heterodyning discussed a bit later.)... 

In purchasing a pulse NMR spectrometer and magnet, all of these general considerations as well as those discussed in V.B.4. about dealing with manufacturers are applicable. It is wise to buy as flexible an instrument as one can afford. The field of pulse NMR spectroscopy is changing rapidly and it would be tragic to be limited by some needless instrumental characteristics. In addition, it seems to be a fact of life that we never can think of all of the uses of device capabilities until we actually use them. A serious alternative to purchasing a complete spectrometer is to construct one out of commercial components and the reader is referred to section V.C. for further discussions. 

When you buy or use a pigment, you use it for its color. This obvious statement is difficult to control in practice as everyone looks at color with his own eyes. Fortunately, the spectrometers give CIELAB values which are accepted by everyone. This system is valid for comparison only if a pigment is analyzed in the same matrix or resin. 

Most practitioners use carbon microneedle emitters, and a few others use silicon emitters. Silicon emitters can be manufactured more rapidly, but carbon emitters are more rugged and can be heated to much higher temperatures (for flash cleaning). Other types of emitters (bare wire, metal microneedles, metal tip, razor blade, or volcano) are only sparingly used. Users either make their own emitters (with commercial or home-built devices) or else purchase them (from mass spectrometer manufacturers or independent vendors). The choice of making or buying emitters usually comes down to cost and time. 

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