A microcomputer-based system for the processing of spark-source mass spectrometry photoplates

A data acquisition system and processing software for spark-source mass spectrometry (s.s.m.s.) with photographic detection is described. The distinctive feature of this system is that data integrity is maintained during the acquisition and real-time reduction. A microprocessor is used to decide whether or not to save the incoming plate blackening data on a digital tape. This results in the selective recording of spectral lines while relatively long fields with only background are neglected. The magnetic tape is then processed on a general-purpose computer. As the complete profile of each peak is recorded, significant improvements can be made for the blackening linearization, the traceback of interferences and the mass calibration. The off-line software makes it possible not only to obtain the elemental sample composition but also to control the instrumental parameters and the photoplate characteristics. This renders the system suitable for research purposes as well as for routine analysis.     

Computer analysis of amino acid chromatograms.

A procedure is described for the automatic off-line analysis of amino acid chromatograms of protein hydrolysates, using a small computer. The data requirements are basic, and, unlike previous programs, the present system allows the separation and identification of bands, as well as the quantitative determination of composition. With minor modification, the program could be extended for use with most types of chromatographic data. The validity of the application of the program to experimental data is discussed.     

Electronic data processing and automation in elastomer testing

A laboratory data processing system is introduced, based on a central process computer with numerous input-output stations and subordinated functioning microcomputers. The various data-acquiring possibilities are described by giving examples of testing methods in a rubber testing department, from the pure evaluation of off-line acquired experimental data to fully automated running of tests controlled by computer. The experiences gained from the system from the view of the user and the EDP-specialists are illustrated, which may be useful at the planning stage of similar laboratory applications.     

Artificial intelligence for the interpretation of combined spectral data : Design and development of a spectrum interpreter

The design of a knowledge-based system for the interpretation of combined spectral data for structure elucidation (EXSPEC) is described. Some basic design features are discussed and the functioning of the knowledge base, inference mechanism and user-interface is outlined. Attention is focussed on the development of a spectrum interpreter for infrared and mass spectral data. Interpretation of spectra for 120 liquid alcohols used for rule generation was successful. The system can be run on a Macintosh II or, more slowly, on a Macintosh Plus.     

A large computer system for on-line data acquistion and analysis of data from analytical instruments

Summary Experience with a unique large dual processor system designed to acquire and analyze data from about 140 instruments in a research installation will be described. The system has been in operation for nearly 4 years serving a variety of analytical instruments including gas chromatographs, liquid chromatographs, tensile testing machines, differential thermal analyzers, and other miscellaneous instruments. The system also serves a large community of scientific time-sharing users, a substantial portion of which reduce data and carry out scientific calculations on data acquired off-line on paper or magnetic tape. Unique features of the system are long distance transmission of analog data, retention of raw data for reanalysis, post processing of data into material balance, kinetic or statistical equations, interactive graphical display of the data acquired on-line and the ability to monitor instrument performance. Another unique features is the ability to develop new analysis programs in time-sharing without fear of jeopardizing the integrity of the data collection process.     

Discovery of mass spectral characteristics and automatic identification of wax esters from gas chromatography mass spectrometry data

The mass spectral characteristics of wax esters were systemically summarized and interpreted through data mining of their standard mass spectra taken from NIST standard mass spectral library. Combining with the rules of retention indices described in the previous study, an automatic system was subsequently developed to identify the structural information for wax esters from GC/MS data. After tested and illustrated by both simulated and real GC/MS data, the results indicate that this system could identify wax esters except the polyunsaturated ones and the mass spectral characteristics are useful and effective information for identification of wax esters.     

Quality assurance in operating a multielement ICP emission spectrometer

In the industrial laboratory environment, quality assurance in the operation of a multielement inductively coupled plasma emission spectrometer (ICPES) must often be entrusted to laboratory technicians with little or no technical background in spectrochemical analysis. Therefore, to be successful, a quality assurance program must be reduced to a simple, routine practice. Essential components of the quality assurance program described in this paper are (1) An atom-to-ion emission intensity ratio for multielement optimization and for reproducing optimum analysis conditions. (2) A concise, easily applied specification for sensitivity and for precision. (3) A regimen for monitoring of, and correcting for, calibration and background drift. (4) A set of comprehensive spectral interference calibrations maintained using the emission intensity ratio. (5) A high resolution spectrometer for minimizing spectral interferences. (6) A program of long term performance monitoring and maintenance/record keeping.Each of these components is described in detail. Adherence to this program enhances analytical reliability by helping to ensure that raw concentrations are generated consistently under optimum instrumental conditions, and that corrections for spectral interferences are applied accurately even though interference calibrations may be several months old.The importance of adequate resolution and the proper choice of positions for off-line background measurements is borne out by a detailed study of the determination of toxic trace elements in National Bureau of Standards fly ash samples. As, Be, Cd, Pb, Sb, and Se were determined accurately without isolation/preconcentration from the aluminosilicate matrix. Several determinations required corrections for residual spectral interferences amounting to 100–500% of the resultant concentration, underscoring the accuracy of the interference correction procedures.     

Development of an improved heated interface for coupling solid-phase microextraction to high-performance liquid chromatography

The aim of the study described in this report has been the development and the evaluation of a new improved interface to be operated under continuous heating, for on-line coupling solid-phase microextraction (SPME) to high-performance liquid chromatography (HPLC). Heating is desirable to increase desorption rate and decrease carryover. The results obtained have been compared with that obtained by off-line desorption and online desorption without heating. The SPME-HPLC interface described here has an inner volume of 60 microL, fixation for infinite points and a novel leak less sealing system. When the heating system was used, the area values were almost 10-fold higher than that obtained using the off-line mode. The obtained chromatograms showed an increasing of the area and height of chromatographic peaks and proved the excellent performance and reproducibility of the interface developed in this work.     

Quantitative Transfer of In-Gel Digest Products to Liquid Chromatography-Electrospray Mass Spectrometry Using On-Line Coupled Extraction

A system is described for the on-line extraction of a digested protein in a gel spot. The extract obtained was on-line transferred to a precolumn, used to desalinate and preconcentrate the sample. The precolumn was switched in-line with an LC-ESI-MS system to separate the digest products prior to detection. By using this approach sample losses were minimized and the sample was quantitatively transferred. The benefits of the system were shown for the in-gel tryptic digest of several model proteins. Using this system, the sensitivity was 13-fold increased compared to the off-line extraction of in-gel digest products leading to a higher sequence coverage and thus a better identification potential. Also, the within day repeatability was a factor 2.5 improvement using the on-line procedure compared to the off-line extraction procedure.     

The rational use of a dynamic on-line data processing system for high and low resolution mass spectrometry

Some of the factors determining the configuration of a mass spectrometry data processing system are discussed. A rationalisation is given for a laboratory situation dealing with a variety of mass spectrometric problems. The effective use of a dynamic on-line system in such an environment is demonstrated. Conversational procedures are described for the acquisition, reduction and interpretation of mass spectral data, using a CRT visual display terminal as a fast man-computer interactive communication medium.     

A computer system for structural identification of organic compounds from 13C NMR data

A computerised library search system for ¹³C NMR data is described. Given the spectral data of an unknown compound, the system will retrieve from the library those reference compounds exhibiting similar spectra. For comparison the spectral data are converted into a binary code, designed to reflect the underlying structure rather than exact values for chemical shifts. Thus, the ability of the system to retrieve compounds similar to the unknown (as opposed to identical) is greatly enhanced. A sophisticated search strategy adapting itself automatically to the problem at hand makes the system highly efficient.     

Quantitative study of single photon radionuclide computed tomography--delineation of body contours

Several methods to obtain the body contour which is necessary to reconstruct the quantitative images with single photon radionuclide computed tomography (SPRCT) are described in this paper. A multipurpose gamma camera system which is composed of 2 detectors, data processor and others were used to collect the data of SPRCT and body contour. An iterative reconstruction technique was implemented to reconstruct the image. Three methods for obtaining the body contour were tested. The first method utilizes X-ray CT data. The data which are obtained by GE CT/T are transferred to the data processor of SPRCT through the off-line magnetic tape and delineate the body contour. The second method uses a transmission source which was attached on the opposite side to detector. The third method uses gamma-rays which are generated by Compton scatter in the tissue of patient. The first and the second methods were able to use to obtain the body contour, but the contour obtained by third method was not accurate.     

Automated fatty acid analysis.

An automated system for the analysis of fatty acids is described. Samples dissolved in CS2 are automatically injected and separated by temperature programmed gas chromatography. Peak areas and retention times were measured by an electronic integrator, and recorded on punched paper tape. Peaks are identified and amounts calculated by an off-line computer program based on one or more internal standards. The system is designed for use with samples of at least 10 mug. Some of the problems adn limitations are discussed.     

Computer-aided interpretation of mass spectra

A system is described in which computer techniques are used to carry out major steps in the procedure for interpretation of high-resolution mass spectral data. These steps include identification and evaluation of the molecular ion, neutral fragments lost from the molecular ion, and characteristic ion series, followed by elucidation of specific structural details using a sub-routine for the particular compound class selected. The technique shows promise of not only increasing the interpreter's efficiency, but of providing more specific and detailed structural information from the spectral data.     

Off-line capillary electrophoresis/fully automated nanoelectrospray chip quadrupole time-of-flight mass spectrometry and tandem mass spectrometry for glycoconjugate analysis

Implementation and optimization of an off-line capillary electrophoresis (CE)/(−)nanoESIchip-quadrupole time-of-flight (QTOF) mass spectrometric (MS) and tandem MS system for compositional mapping and structural investigation of components in complex carbohydrate mixtures is described. The approach was developed for glycoscreening and applied to O-glycosylated peptides from urine of a patient suffering from α-N-acetylhexosaminidase deficiency, known as Schindler's disease. The fundamental issue of sensitivity, previously representing a serious drawback of the off-line CE/MS analysis, could be positively addressed by the off-line conjunction of CE with automated chip-based ESI-QTOF-MS to provide flexibility for CE/chip MS coupling and enhance structural elucidation of single components in heterogeneous mixtures. Copyright © 2004 John Wiley & Sons, Ltd.     

Strukturaufklärung organischer Verbindungen durch computerunterstützten Vergleich spektraler Daten

A system for computer-aided identification of organic compounds by means of spectroscopic data is described. The binary coded spectral data of the unknown compounds are compared with a reference file containing NMR., IR. and Mass Spectra. A highly flexible software automatically selects the appropriate search strategy and directs the updating of the collection, thereby ensuring continuous adaption to varying needs.     

Ein Automatisiertes Mess-System für die Ge(Li)-Gammaspektrometrie

An automated off-line Ge(Li)-spectrometer is described. Its special features are a sample changer with rotating disk store and pneumatic tube, a self-controlling source—detector distance and an autonomous control programmed by cable connections or by punched tape via a central control unit. The system is meant to do complex routine work in activity supervision and activation analysis.     

Preconcentration Systems Using Polyurethane Foam/Me-BDBD for Determination of Copper in Food Samples

A new reagent, 6-[2′-(6′-methyl-benzothiazolylazo)]-1,2-dihydroxy-3,5-benzenedisulfonic acid (Me-BDBD), was synthesised and used in on-line and off-line systems for copper preconcentration by solid-phase extraction. Spectrophotometry and Flame Atomic Absorption Spectrometry (FAAS) were the detection techniques. Polyurethane foam loaded with Me-BDBD packed in a minicolumn was used as sorbent in both systems. The spectral characteristics of Me-BDBD were investigated. The optimum pH values for maximum sorption of the metal are between 7.0 and 8.5. Copper was desorbed with 0.05 and 0.50 mol L⁻¹ hydrochloric acid solutions, for on-line and off-line systems, respectively. The effects of several foreign substances on the adsorption of copper are reported. The enrichment factors obtained were 7 (on-line) and 26 (off-line) for the systems. The proposed procedures allowed the determination of copper with detection limits of 3.4 and 1.4 μg L⁻¹ (0.85 and 0.35 μg per gram of sample) for on-line and off-line systems, respectively. The precision of the procedures was also calculated: 3.2 (on-line) and 1.9% (off-line). The validation of the procedures was carried out by analysis of certified reference material. The copper contents in corn and rice flour and black tea samples were determined by applying the proposed procedures.     

Evaluation of protocols for reproducible electrospray in-source collisionally induced dissociation on various liquid chromatography/mass spectrometry instruments and the development of spectral libraries

Mass spectral libraries provide a tool for identifying unknown compounds using both molecular weight and fragmentation information. Mass spectrometers with electrospray ionisation (ESI) and atmospheric chemical ionisation (ApCI) sources have the capability to produce data of this type using in-source collisionally induced dissociation (CID), and in-source CID libraries can be created. Due to the variation in electrospray source design from different instrument manufacturers, the production of reproducible in-source CID spectra that can be used in libraries for all instrument types is not a trivial task. To date, the evaluation of the production of in-source CID libraries has tended to focus on similar instruments from one manufacturer. The studies have also tended to focus on specific compound classes, with a limited molecular weight range.This report describes the findings from the investigation of protocols for the creation of mass spectral libraries using ESI in-source CID on six instruments from four different manufacturers. The overall goal was to create a spectral library for the identification of unknowns. The library could then be applied across all manufacturers' electrospray instruments.Two different experimental protocols were attempted. The first used a tuning compound to establish standard ESI source conditions, with fixed fragmentation potentials. The second involved the attenuation of the [M + H](+) ion to a known degree. A diverse range of compounds (pharmaceutical, photographic, pesticides) was tested to establish the reproducibility of the spectra on the six instruments. Both protocols produced spectra on the various instruments that in many cases were very similar. In other examples, the spectra differed not only in their relative ion abundances, but also in terms of the spectral content. Important observations regarding the effect of ion source design are also reported.The degree of spectral reproducibility was calculated off-line by comparing the five most abundant ions (20% for each ion that matches) from each spectrum on each instrument. This approach was adopted, as we do not possess a software package that met our requirements for spectral comparison. Match factors (% fit) were calculated by comparing each spectrum against the spectra recorded for the same compound and then for all other compounds, on each instrument. The % fit values derived by the off-line approach gave a clear view of the spectral reproducibility from instrument to instrument and also discriminated the spectra of the various compounds from each other. The applicability of this approach was tested using a blind trial in which several compounds were presented as unknowns, their in-source CID spectra recorded and the five-ion approach used for identification.