Hardware Overview

GC-MS could not have been developed without the advent of the computerized data system. Conversely, the computerized data system makes it possible to exploit all the synergistic powers of the hyphenated method. It is revealing to return to early published forays into the method and read the concerns of the practitioners regarding the sheer volume of data that was available and recorded. In retrospect, the first data systems were primitive beasts. Processing speeds were very slow, and they were matched by the speed of the analogue-to-digital conversions. Data storage initially used magnetic tapes, similar to those still available today but with lower capacities. The early high-capacity data storage devices were removable platter drives. Generically, they were known as Winchester drives. The term Winchester comes from an early type of disk drive developed by IBM in 1973 that stored 30 MB and had a 30 ms access time. It was called a Winchester in honour of the 0.30-calibre rifle of the same name. For the mainframe data systems that controlled mass spectrometers, the platters (encased in cassettes with diameters of about 40 cm and thicknesses of about 5 cm) had a capacity of 10 MB. In GC-MS each platter filled up quickly; the full disk was removed from the drive, and an empty platter inserted. Winchester hard disk drives were not available for personal computers (PCs) until 1980. The PCs of today are more powerful than the mainframes used in the early days of GC-MS. Commercial systems are controlled by PCs, which is one reason that they have dropped in price. Storage capacities of 20 GBs on a single platter are available today.

Data records have a much longer life than does the original sample itself. There are rules that govern how long a sample or sample extract can be stored, at what temperature, and in what form. Outside of that time limit, that sample cannot be used for analysis. These rules exist as a result of concerns about sample degradation. In general, analysts do not worry about data degradation, although the long-term stability of magnetic-based recording media has been a topic of discussion. The relevant lifetime of data records depends on the availability of a software system that can access and manipulate the data. Analogies with commonplace computer software can be drawn readily, as each new iteration of software makes obsolete some fraction of the installed software base and its associated data. The problem is exacerbated by a competitive marketplace and manufacturers that disappear or are eager to make older systems obsolete.

Data processing and manipulation routines are manufacturer-specific and sometimes proprietary. The computer for a mass spectrometer may remain in the laboratory past the time when the mass spectrometer itself is removed so that the system can be used as required to read and process old data files. Clearly this is neither a desirable nor an efficient approach to data archival management. Manufacturers of commercial mass spectrometers have become much more cognizant of this fact over the past few years, and analytical data interchange efforts have been undertaken. The issue of backwards data compatibility is significant, and should be considered as part of the yearly performance assessment of an analytical laboratory using chromatography-mass spectrometry. Hardware capabilities are not the only issue. The preferences and habits of individual analysts also affect the manner in which data are presented and interpreted. Individuals are shuttled into and out of laboratories regularly, and a record of individual proclivities needs to be maintained and understood, especially in systems as complex as chromatography-mass spectrometry. The proper time to determine whether archived data can be located, read, processed and re-evaluated is not in the midst of crisis or urgency. If the data are worth saving, it is worth going through an exercise to test one's ability to retrieve those data. If the exercise shows that retrieval and reuse is not feasible, the data should not be saved. Previously the criterion for saving the data was the amount of storage capacity that was available, as GC-MS files were 'large', and it was considered impossible to physically save all of the data that could be recorded. The files are still indeed 'large', but storage capacities have increased by a factor of 1000 over the past 20 years, while the files have increased in size by only a factor or 2-3 (the laboratory time frame has not changed in its perception, and the resolution of the recorded data has increased only slightly). Storage capacity is no longer a relevant issue. Meaningful retrieval has become the determinant factor.

Solar Panel Basics

Solar Panel Basics

Global warming is a huge problem which will significantly affect every country in the world. Many people all over the world are trying to do whatever they can to help combat the effects of global warming. One of the ways that people can fight global warming is to reduce their dependence on non-renewable energy sources like oil and petroleum based products.

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