New algorithms for processing and peak detection in liquid chromatography/mass spectrometry data

Two new algorithms for automated processing of liquid chromatography/mass spectrometry (LC/MS) data are presented. These algorithms were developed from an analysis of the noise and artifact distribution in such data. The noise distribution was analyzed by preparing histograms of the signal intensity in LC/MS data. These histograms are well fit by a sum of two normal distributions in the log scale. One new algorithm, median filtering, provides increased performance compared to averaging adjacent scans in removing noise that is not normally distributed in the linear scale. Another new algorithm, vectorized peak detection, provides increased robustness with respect to variation in the noise and artifact distribution compared to methods based on determining an intensity threshold for the entire dataset. Vectorized peak detection also permits the incorporation of existing algorithms for peak detection in ion chromatograms and/or mass spectra. The application of these methods to LC/MS spectra of complex biological samples is described.     

Advanced data processing

Advanced FT-IR processing algorithms and their application are reviewed. A centralized system for processing such data is outlined.     

Radiation detection by using superheated droplets

The superheated emulsion, a radiation detector consisting of superheated droplets dispersed in a gel or a solid matrix, has been in use for some time now. It was initially designed to detect neutrons but also has been modified to detect energetic photons and heavy ions. It has been primarily used as a neutron dosimeter, but has also been used to obtain the energy spectrum for neutrons from Am–Be. The general features of the superheated emulsion detector along with newer analytic methods to obtain more precise results using it as an active device will be presented.     

Radiation processing of wastewater evaluated by toxicity assays

Biological assays have been applied to industrial effluents and sewage influents, from distinct sites, before and after being submitted to ionizing radiation treatment. The objective of this study was to evaluate the efficiency of radiation, mainly electron beam accelerator, for the acute toxicity removal. The selected sampling presented a very toxic level and the radiation process was efficient for toxicity removal for 87.7% of irradiated samples. The sewage influents required lower radiation doses to reduce toxicity when compared to raw industrial effluents.     

The processing of gas-chromatographic data

Summary Methods of data processing for gas chromatography other than the strip-chart recorder are reviewed. After an introductory discussion of the choice between measurement of peak height and peak area for quantitative analysis, the review deals briefly with the use of digital integrators, and more fully with current developments in the application of digital computers to GC.

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Zusammenfassung Es wird ein Überblick gegeben über die Methoden zur Datenverarbeitung in der Gas-Chromatographie (ausgenommen Bandschreiber). Nach einer einführenden Diskussion des Problems Peakshöhen- oder -flächenmessung bei der quantitativen Analyse wird kurz die Verwendung von Digitalintegration besprochen und so dann ausführlicher die neueren Entwicklungen bei der Anwendung von Digitalcomputern behandelt.

     

Using the tools of chromatography,mass spectrometry,and automated data processing in the detection of arson

The analysis of residual accelerants in fire debris is commonly carried out by a three-step procedure: sample preparation; separation and detection; and data interpretation. Each of these steps can be optimized individually but successful analysis requires that they are compatible with each other. The isolation of residual accelerant from fire debris requires that several methods are used to cover the range of fueis that are commonly used by arsonists. Since almost all incendiary fires are set with petroleum based fuels such as gasoline or heating oil, analysis is targeted toward hydrocarbons. Capillary column gas chromatography on apolar phases is now the overwhelmingly predominant method of separation. Data interpretation is commonly carried out by visual comparison of chromatograms. Fire debris analysis presents some unique challenges that are not often encountered in other fields. The analyte may be present at only trace levels and pyrolysis products from building materials or furnishings may dominate chromatographic patterns. Synthetic polymers may act as precursors to hydrocarbons that compete with substances typically found in petroleum based fuels. Exposure to heat and other environmental factors may also generate severe distortions in the chromatographic profiles of accelerants. Unfortunately, there is no simple solution to these problems. Methods are available to reduce some of the chemical noise introduced by interferences and thus enhance the recognizability of the target substances. Mass spectrometry, in combination with a modern data system, is the most effective approach to filter out unwanted substances. The interpretation of the analytical results is aided by scaling, side-by-side comparison, or stacking of chromatograms. An additional advantage of such computerized systems is the possibility of complete automation of the analysis. In this communication, we look at the interplay of chromatographic resolution, noise reduction by mass spectrometry, and automated data evaluation. Examples from model experiments and from simulated arson samples are presented.     

Capability of detection and three-way data

Due to the possibility of making analytical determinations in the presence of non-modelled interferents and to identify the analyte of interest, calibrations based on scores of PARAFAC decomposition of three-way data are becoming increasingly important in routine analysis.Furthermore, the IUPAC and EU (European Decision 2002/657/EC) have accepted the definition given by the ISO 11843 for the capability of detection as the minimum net quantity detectable with a pre-set probability of false positive and false negative. What is more, recently our research group has generalised this definition of capability of detection, CCβ, to multivariate calibrations. In practice, CCβ is a good measure of the quality of the calibration because in its definition it brings together analytical sensitivity with precision in analytical determinations.This paper studies the effect of the pre-treatment of the sample, the signal/noise ratio and the second-order advantage on CCβ when using second-order signals modelled by PARAFAC. All of them are experimental factors which influence the quality of the calibration. Analytical pre-treatment is habitual in the analysis of real samples. Specifically, we analyse the effect of the extraction phase and the clean-up of milk samples on the determination of chlortetracycline by HPLC-DAD. It is shown that it is more efficient to do the joint PARAFAC decomposition of the pure standards with the milk samples.Secondly, the effect of asymmetry on CCβ, according to the path of the noise of the signals, is studied. Specifically, in the determination of naphthalene by excitation-emission spectroscopy, EEM, it is the emission spectrum which limits the capability of detection. It is shown that by eliminating the spectra with the poorest signal/noise ratio in this path, the capability of detection can be substantially improved.Thirdly, the impact on CCβ when the second-order advantage is used, that is when PARAFAC calibration is used over samples with an unknown interference not modelled in the calibration step. This is important to apply a PARAFAC calibration to routine analysis in the IUPAC and European Decision framework. Specifically, in the determination of enrofloxacine in poultry feeding water through excitation-emission fluorescence CCβ is evaluated when the PARAFAC is built only with calibration samples or with the calibration samples plus the test samples with uncalibrated and unknown interferent.     

Radiation processing and functional properties of soybean (Glycine max)

Effect of radiation processing (10, 20 and 30 kGy) on soybean for better utilization was studied. Radiation processing reduced the cooking time of soybean and increased the oil absorption capacity of soy flour without affecting its proximate composition. Irradiation improved the functional properties like solubility, emulsification activity and foam stability of soybean protein isolate. The value addition effect of radiation processing has been discussed for the products (soy milk, tofu and tofu fortified patties) prepared from soybean.     

Radiation processing of natural polymers: The IAEA contribution

Radiation processing offers a clean and additive-free method for preparation of value-added novel materials based on renewable, non-toxic, and biodegradable natural polymers. Crosslinked natural polymers can be used as hydrogel wound dressings, face cleaning cosmetic masks, adsorbents of toxins, and non-bedsore mats; while low molecular weight products show antibiotic, antioxidant, and plant-growth promoting properties. Recognizing the potential benefits that radiation technology can offer for processing of natural polymers into useful products, the IAEA implemented a coordinated research project (CRP) on “Development of Radiation-processed products of Natural Polymers for application in Agriculture, Healthcare, Industry and Environment”. This CRP was launched at the end of 2007 with participation of 16 MS to help connecting radiation technology and end-users to derive enhanced benefits from these new value-added products of radiation-processed natural materials. In this paper the results of activities in participating MS related to this work will be presented.     

Signal and data processing for atomic absorption spectrophotometry

The state-of-the-art of signal and data processing techniques for atomic absorption spectrophotometry is described and discussed. Aspects of optical and atomizer design of greatest importance for providing the best signal to noise S/N ratio and minimum curvature are summarized. In background corrected systems, amplifier gain and time constants must be carefully matched, especially for transient signals. A method is given for calculating the sampling time of peak search systems. Methods of signal averaging are described and the importance of precision calculations is stressed. The correct sequence of readings for calibration is discussed. The causes of curvature are shown for simple and complex curves and methods of correction are compared. Other desirable functions are calculation of sensitivity and detection limit, error warnings and external data output facilities.     

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.     

Microprocessor-based data processing and quality control in hematology

Routine hematological determinations with Coulter Counter model S instruments benefit from electronic data processing, and appropriate quality control is essential. The system described here is based on an INTEL 8008 microprocessor provided with options for handling sample identification numbers, duplicate print-out of results on self-adhesive labels, and zero-level quality control functions which utilize both patient samples and quality-control samples. The arithmetical means of the results of ten patient samples are calculated in real time for four parameters in whole blood. The running mean values of two of these parameters (MCVand MCHC) are suitable for zero-level process control. together with signalling of extremes. Daily mean values of patiant samples and quality-control samples are also calculated to check the stability from day to day. The microprocessor-based system is adequate for these functions and is relatively simple and inexpensive.     

Noise in FT-IR spectral data processing

A series of exploratory works on resolution enhancement, precision in wavenumber, integrated band intensity measures, and noise level control were performed on FT-IR spectra using standard mathematical techniques of data processing. In this communication, the infrared (IR) absorption band corresponding to the ν₈ mode of dichloromethane, CH₂Cl₂, was studied in benzene solution.Fourier self-deconvolution of the CH₂Cl₂ ν₈ band was carried out using standard software supplied for the purpose. Second and fourth derivative spectra were obtained with the “Nicolet” software parameter “DR1”. Self-deconvolution in Fourier space and derivative techniques were used to decrease the band full-width at half-height (FWHH) and achieve an apparent band resolution enhancement.The total area under the self-deconvoluted band is not exactly the same as under the original band. Under optimum self-deconvolution conditions, the integrated area increases by 6.9 % as compared with the out-of-phane CH bending W(CH₂) original band. However, a linear relationship between the integrated area of the self-deconvoluted band and FWHH of the original Lorentzian component was observed.The applicability and potential advantages of the self-deconvolution and derivation methods in spectral data processing are strongly limited by the noise level or signal-to-noise ratio (SNR) of the original IR spectra.     

Enhancement of analyte detectability in isotachophoresis exploiting spectrophotometric diode‐array detection with chemometric data processing

The potentialities of capillary ITP combined with diode‐array detection (DAD) with subsequent chemometric data processing have been investigated in this work. A series of different migration configurations were created using model analytes, interferents and appropriate spacers. Special attention has been paid not only to constituents migrating in fully developed ITP zones but also to the spike mode of ITP migration. The purity assessment and identity confirmation of model analytes migrating in both modes were performed by means of multivariate curve resolution and target transformation factor analysis (TTFA). Their successful applications have revealed a smart way to increase in the analytical information obtained by ITP separation even in the instance of trace analysis.     

Automation of liquid scintillation data processing

A program was written in the Basic language to handle scintillation counting data by a time-sharing computer. Explanation is given for the use of the program to facilitate the most common types of calculations, as well as the automatic data handling between the spectrometer and the remote computer. The merits of the system are discussed and a sample of the operation and the output is given.     

Distributed data processing in NMR spectroscopy

The development and use of a communication system for the chemical laboratory is described. It provides local access to instruments, computers and personal work stations (PC) as well as connection to wide area networks via the X.25 standard protocol and respective gateways on the basis of the DFN services (Deutsches Forschungsnetz) dialog, remote job entry, file transfer and message handling (EAN X.400). The standardization of digital spectra is considered.     

Radiation processing of Nylon 6 by e-beam for improved properties and performance

Percent water absorption of Nylon 6 was reduced substantially when irradiated by e-beam radiation in presence of triallyl isocyanurate. Hardness, tensile strength, flexural strength, and impact resistance of Nylon 6 were also improved with the dose of e-beam radiation. Improvement of mechanical properties and reduction of water absorption were due to the cross-linking of polyamide molecules in the presence of high-energy radiation. Increase of cross-linking with increasing radiation dose was verified by the increase of gel content at higher doses.     

Recent progress on nanopore electrochemistry and advanced data processing

Nanopore-based technology offers nanoscale chemical environments with intriguing confinement effects, which isolates individual analytes from the bulk solution. This confined space combines mass transportation and electrochemical measurement, providing new insight into single entity sensing. In this mini-review, we highlight the exciting progress on nanopore electrochemistry. Starting with a concise summary of nanopore-based electrodes, we introduce the fabrication methods and characterizations of the various nanopore electrodes. Then, the special attention focuses on the application of nanopore electrochemistry in single nanoparticle analyzing and intracellular electrochemical sensing. The advanced data analysis tools and Machine Learning algorithms for rapid encoding single-molecule characteristic sets are also covered, which promotes the sensitivity of nanopore electrochemistry and opens a new possibility for revealing single-entity heterogeneity.     

A microprocessor-based instrument for correlation chromatography and data processing

A microprocessor-based instrument performing all actions necessary for correlation chromatography, a correlator, is described. This correlator is designed to make correlation chromatography as easily applicable as other types of chromatography. The instrument can also complete the data processing of the finished correlogram. Examples are the determination of the retention time, baseline drift corrections, the determination of the peak amplitudes and peak areas including the confidence levels. Design considerations and results are given. The systematic error defining the accuracy is typically 0.2%.     

Package for on-line data acquisition and processing with microcomputers

Professor Ducauze and his co-workers from the Institut National Agronomique Paris-Grignon interfaced their CBM 8032 microcomputer with several chromatographs and developed a software package for the data acquisition and processing of the chromatograms. A specific option of the package is the correction of peak positions for long term drift by a comparison with reference chromatograms stored on disk.