Gamma spectrum analysis including NAA with SAMPO for windows

SAMPO for Windows is a high performance gamma spectrum analysis program. All the measurement, analysis and NAA phases can be done either under full interactive user control or user defined tasks can be used for automated measurement and analysis sequences including control of MCAs and sample changers. High resolution gamma-ray spectroscopy together with the possibility to resolve complex multiplets with high accuracy makesSAMPO very suitable for INAA. On the other hand, the possibility to automate analysis sequences allows its use effectively also in all routine NAA measurements.NAA inSAMPO is accomplished using comparative methods. Spectra of standards, flux monitors, controls and actual samples are analyzed normally to obtain the peak areas which are optionally corrected for decay. In the comparison the flux monitor results are used to correct for variations in the effective neutron flux. An optional irradiation position correction can also be applied. The controls are used to alarm for possible deviations in the results.The sophisticated spectrum analysis methods used together with the comparative NAA and monitors give accurate results limited by the systematic effects only. The Windows environment provides ease of use and further processing power is available through the interface to expert system identification of nuclides.     

Determination of heavy metals in sewage-based fertilizer using short-lived isotopes

A fully instrumental method for the neutron activation analysis of heavy metals in sewage sludges has been developed, based on short-lived isotopes, and restricting the total experiment time to 1 hour per sample. The irradiation scheme consists of a cyclic and conventional part, the period of the cyclic irradiation being optimised for the determination of lead, using^207mPb (T=0.8 s). Gamma ray spectra from Ge(Li) detectors are stored on magnetic tape and analysed using the SAMPO programme. An IDENTIFY subroutine enables absolute determinations to be made eliminating the need for standards. Sensitivities and detection limits for 21 heavy metals have been determined and the results for several sludges are presented.     

NADA: A versatile PC based program for neutron activation data analysis

We have developed a PC based program for neutron activation data analysis using the FORTRAN and C languages. The routines are based on creating files associated with conventional ORTEC hardware and output software. The main features of the program include radionuclide identification, and the use of semi-automatic integration or the peak fitting SAMPO routine. Other developments are hard and soft copy records for detailed sample identification and particular irradiation, decay and counting procedures. Flux variations, high deadtime corrections, counting geometries, spectral and nuclear interferences, as well as uranium fission interferences are also automatically accounted for. The data output includes concentration values in %, ppm, g or ppb units with associated errors, while detection limits for each individual sample are indicated. Further data output can easily be generated which can be imported to most spreadsheet programs for various statistical uses. A future implementation to the program will include batch-file processing and automated self-absorption calculations for geological samples.     

Isotope abundance analysis methods and software for improved sample identification with supersonic gas chromatography/mass spectrometry

We present newly developed isotope abundance analysis (IAA) methods and software which are used to derive elemental formula information from experimental mass spectral data of molecular ion isotopomeric abundances. The software, using a novel method, can also be used to automatically confirm or reject NIST library search results, thereby significantly improving the confidence level in sample identifications. In the case of IAA confirmation of the NIST library results, sample identification is unambiguous, since the confirmation is achieved by two independent sets of data and analytical methods. In the case of a rejection, such as when the molecule is not included in the library's databases, the IAA software independently provides a list of elemental formulae with declining order of matching to the isotopomeric experimental data, in a similar way to accurate mass measurements with costly instruments. IAA is ideally applicable to gas chromatography/mass spectrometry (GC/MS) (and liquid chromatography/electron ionization mass spectrometry (LC/EI-MS)) with a supersonic molecular beam (SMB) since it requires a trustworthy and highly abundant true molecular ion that is unique to the SMB-MS systems, plus the absence of self chemical ionization and vacuum background noise, again unique features of GC/SMB-MS. The various features of the IAA methods and software are described, their performance is demonstrated with the analysis of experimental GC-SMB-MS data and the IAA concept is compared with accurate mass alternatives. The combination of IAA and GC/SMB-MS is believed to be superior to accurate mass GC/MS in view of the general availability of trustworthy molecular ions for an extended range of compounds.     

Gamma spectrometric monitoring of environmental radioactivity using a mobile equipment

Using gamma-spectrometry systems on mobile units with accurate position information is a convenient means for surveying large areas for radioactive fallout or finding hot spots due to misplaced sources or releases from nuclear installations. Traditionally, large (tens of litres) high efficiency NaI(T1) detectors have been used for the purpose. HPGe detectors, however, offer certain advantages which can often compensate for their lower efficiency. This kind of remote sensing, regardless of detector type, requires specialized software. In order to provide accurate position information, the integration times must be kept as short as possible. This is especially true for fast air-borne measurements where counting periods below one second are desirable. We have constructed a special version of SAMPO software which controls data acquisition and runs real-time gamma-spectrum analysis including peak determination, nuclide identification, activity calculations, and reporting. The measurement/analysis cycle can be reduced down to 0.5 seconds on a standard Pentium-based PC. The analysis results are combined with accurate co-ordinates from a differential GPS system on a color coded map. The system is also able to give alarms based on different criteria. We have already measured and analyzed more than 500 000 spectra in field applications using jets, helicopters, cars, and also on-foot.     

Neutron activation analysis without multielement standards

To carry out neutron activation analysis without using multielement standards requires knowledge of (i) the absolute photopeak efficiency as a function of energy of the gamma-ray detector, (ii) nuclear data for each reaction used, and (iii) neutron flux parameters for the irradiation position. The present paper discusses each of these topics and shows an example of the determination of flux parameters and improved nuclear data.     

Computerunterstützte Identifizierung von Isotopenmustern in niederaufgelösten Massenspektren

The identification of isotopic patterns in low resolution mass spectra with the aid of a computer program is described. Those masses in the mass spectra which coincide with the isotopic patterns are printed out. As additional information, a criterion is given indicating the quality of correlation between the measured and calculated isotopic pattern. The program is written as a subroutine in FORTRAN IV and can be executed by small computers too.     

Critical evaluation of screening techniques for emerging environmental contaminants based on accurate mass measurements with time‐of‐flight mass spectrometry

Emerging contaminants from wastewater effluent samples were analysed, using posttarget and nontarget analysis techniques. The samples were analysed with an ultra performance liquid chromatograph‐time‐of‐flight mass spectrometer (UPLC‐TOF‐MS), and the resulting data were processed with commercial deconvolution software. The method works well for posttarget analysis with prior information about the retention times of the compounds of interest. With positive polarity, 63 of 66 compounds and with negative polarity, 18 of 20 compounds were correctly identified in a spiked sample, while two compounds of a total of 88 fell out of the mass range. Furthermore, a four‐stage process for identification was developed for the posttarget analysis lacking the retention time data. In the process, the number of candidate compounds was reduced by using the accurate mass of selected compounds in two steps (stages 1 and 2), structure–property relationships (stage 3) and isotope patterns of the analytes (stage 4). The process developed was validated by analysing wastewater samples spiked with 88 compounds. This procedure can be used to gain a preliminary indication of the presence of certain analytes in the samples. Nontarget analysis was tested by applying a theoretical mass spectra library for a wastewater sample spiked with six pharmaceuticals. The results showed a high number of false identifications. In addition, manual processing of the data was considered laborious and ineffective. Finally, the posttarget analysis was applied to a real wastewater sample. The analysis revealed the presence of six compounds that were afterwards confirmed with standard compounds as being correct. Three psycholeptics (nordiazepam, oxazepam and temazepam) could be tentatively identified, using the identification process developed. Posttarget analysis with UPLC‐TOF‐MS proved to be a promising method for analysing wastewater samples, while we concluded that the software for nontarget analysis will need improvement before it can be used in environmental analytical work with LC‐TOF‐MS systems. Copyright © 2012 John Wiley & Sons, Ltd.     

Positive confirmation of identity of doping agents using gas chromatography-mass spectrometry with Fourier transform infrared spectrometry

During the past two decades, the use of retention times in gas chromatography has been augmented by mass spectrometric data. By providing both the retention indices and spectrometric data, this technique has greatly improved gas chromatographic identification analysis. However, although gas chromatography-mass spectrometry has become pre-eminent, several drawbacks still remain. The mass spectral library often gives erroneous identifications when concentrations near the detection limit are analysed, when gas chromatographically interfering substances are present, or when structural isomers or compounds exhibiting identical retention behaviour are analysed. Linked with gas chromatography-mass spectrometry, Fourier transform infrared spectroscopy can be a powerful complementary technique in peak identification analysis. Some spectral data to illustrate this point are presented.     

Toxicological screening of urine for drugs by liquid chromatography/time-of-flight mass spectrometry with automated target library search based on elemental formulas

The present study describes a novel approach for utilizing liquid chromatography/time-of-flight mass spectrometry (LC/TOFMS) in qualitative screening analysis. An LC/TOFMS method was developed for screening toxicologically relevant substances in urine samples. After solid phase extraction and LC separation, the method included full spectrum acquisition followed by automatic internal calibration, searching against a target library, and reporting positive identifications. The target library, containing 433 toxicologically relevant substances in the mass range of 105-734 Da, was created simply by entering the elemental formulas of substances into the instrument software for the calculation of their respective monoisotopic masses. In addition to parent drugs, the library contained selected urinary drug metabolites, based on their structures available in the literature. Identification was based on the exact masses of the compounds. The LC/TOFMS method provided 5-10 ppm mass accuracy for a majority of identified compounds in authentic urine samples. Compared with established thin-layer and gas chromatographic methods, the LC/TOFMS method produced similar findings in urine with the additional advantage of metabolite identification without actual reference substances.     

Database driven analysis for nuclide quantification by gamma spectra

For a set of a priori given radionuclides, extracted from a general nuclide data library, the authors use median estimates of the gamma-peak areas and estimates of their errors to produce a list of possible radionuclides matching gamma-ray line(s) and some measure of the reliability of this assignment.

An a priori determined list of nuclides is obtained by searching for a match with the energy information of the database. This procedure is performed in an interactive graphic mode by markers that superimpose the energy information provided by a general gamma-ray data library on the spectral data. This library of experimental data includes approximately 17,000 gamma-energy lines related to 756 known gamma emitter radionuclides listed by ICRP.     

Precise determination of macro contents of nitrogen in titanium carbonitride by instrumental photon activation analysis

SYNTH, a Windows^TM based software package developed for generating synthetic gamma-ray spectra, has been updated and extended to include the ability to generate gamma-ray spectra resulting from neutron activation. Along with a new gamma-ray library (based on the NNDC PCNuDat compilation), and the best available neutron cross-sections, it is now possible to simply, and quickly predict the interference effects of different bulk and trace element compositions by generating a synthetic gamma-ray spectrum that will be representative of a specific set of input parameters. The parameters include, but are not limited to: elemental composition (bulk, and trace) of the sample; irradiation, decay, and count times; thermal, and resonance neutron flux; sample to detector distance; detector specifications; and electronics configuration. Using existing data reduction codes, it is then possible to generate Minimum Detectable Activities (MDA's) for other trace elements that you may wish to detect in this type of matrix.     

Selection of short-lived isotopes for activation analysis with respect to sensitivity

During the last decade the use of short-lived isotopes in activation analysis has exploded, owing to the application of high resolution gamma-ray spectrometry. Complex spectra can in fact be resolved without the need for chemical separations. The application of cyclic activation-counting enables the use of isotopes with half-lives below 10 seconds. These short-lived isotopes can be produced by different activation processes. As neutron sources one can distinguish reactors, generators for 14 MeV or high energy machines such as cyclotrons and isotopic neutron sources. High energy photons can be produced by interaction of an energetic electron beam with a target, giving rise to an intense bremsstrahlung spectrum with maximum energy from 10 up to 70 MeV. While these photons induce several types of threshold reactions, lower energetic photons are used for resonance activation producing metastable isomers. More and more also charged particles (p, d,³He, α) are being used as projectiles to produce radioactive isotopes that can be measured in activation analysis. In the present paper a concise compilation is made of the nuclear reactions, applicable in activation analysis of minor or trace constituents using gamma emitting isotopes with half-lived smaller than 1 hour. Activations of all naturally occurring elements, except the noble gases, with Z values ranging from 9 to 92 have been considered. The reactions resulting in the most sensitive gammaspectroscopic determinations have been selected and are tabulated per element, together with the appropriate cross section and the resonance integral if significant for neutron reactions, the cross section at the giant resonance energy for the photon and at the maximum of the excitation function for the charged particle reactions and the threshold energy for all threshold reactions. For each isotope produced the half-life and the major gamma-ray energy is given. Finally calculated or experimental sensitivities have been compiled from a number of references, as the emission rate per second of the most intense gamma-ray, at the end of a 1 minute irradiation under well-defined circumstances for 1 microgram of the element. When cyclic activation has been applied it is indicated. These data are provided for more than 200 nuclear reactions. It appears that the majority of the 70 elements constacred can in some way be determined with a high sensitivity after such a short irradiation. Only for the elements Tm and Tb no reaction yielding a short-lived isotope with a reasonable sensitivity could be found. Both elements can however very sensitively be determined after a longer neutron irradiation. For a number of elements activation analysis by means of the middle-long-lived isotopes (2 hours to 3 days) is the most sensitive even after a 1 minute irradiation and immediate count (Mn, Ga, As, Sr, Ru, La, Eu, Ho, Lu, Os and Au). But for all other elements the highest gamma emission rate results from isotopes with half-lives shorter than 1 hour. Extremely high counting rates are obtained after thermal reactor neutron activation for Na, Sc, V, Co, Se, Rh, Ag, In, Eu, Dy, Er and Hf. For a number of elements the selectivity of the analysis can however largely be enhanced by irradiation under Cd-cover. High σ₀ ratios exist in fact for activation of medium and high Z elements such as Nb, Rb, Rh, Sn, Sb, Ba, Ce, Lu, Ta, Os, Hg and U. For some elements activation with reactor fission neutrons or 14 MeV neutrons provides an interesting sensitivity for a threshold reaction or the production of an isomer (F, Si, P, Cl, Ca, Cr, Se, Y, Ba, Ce, Pr, Bi, Pb). Cyclic activation and counting of very short-lived isotopes has been applied advantageously in the ng to μg range for a number of elements. Also cyclic activation with a 14 MeV generator has recently been studied. Low energy photon activation analysis allows selective production of metastable isomers of Se, Br, Ag, Er, Hf, Ir and Au, while high energetic photon production analysis yields high specific activities for elements such as K, Cr, Se, Br, Mo, Pr, Nd, Ho and allows interesting determinations of Mg, Cl, Si, Cr, Fe, Zr and Pb. Also charged particle activation can be used with surprisingly high sensitivity for some medium and high Z elements (Cr, Y, Se, Br, Zr, Mo, La, Ta, V). The intensity of the irradiation is in these cases mostly only limited by the properties of the sample itself, such as heat transfer and matrix activity. Examples of the compilation will be discussed and applications shown.     

A computer program for activation analysis

A computer program for calculating activation analysis results is described. The program comprises two gamma spectrum analysis programs, STOAV and SAMPO and one program for calculating elemental concentrations, KVANT. STOAV is based on a simple summation of channels and SAMPO is based on fitting of mathematical functions. The programs are tested by analyzing the IAEA G-1 test spectra. In the determination of peak location SAMPO is somewhat better than STOAV and in the determination of peak area SAMPO is more than twice as accurate as STOAV. On the other hand, SAMPO is three times as expensive to use with a Cyber 170 computer as STOAV.     

SAMPO 90 High resolution interactive gamma-spectrum analysis including automation with macros

SAMPO 90 is a high performance gamma-spectrum analysis program for personal computers. It uses color graphics to display calibrations, spectra, fitting results as multiplet components, and analysis results. All the analysis phases can be done either under full interactive user control or macros and programmable function keys can be used for completely automated measurement and analysis sequences including the control of MCAs and sample changers. Accurate peak area determination of even the most complex multiplets, of up to 32 components, is accomplished using linear, non-linear and mixed mode fitting. Nuclide identification is done using associated lines techniques allowing interference correction for fully overlapping peaks. Peaked Background Subtraction can be performed and Minimum Detectable Activities calculated. The analysis reports and program parameters are fully customizable.     

Interrogation of MS/MS search data with an pI Filter algorithm to increase protein identification success

In high-throughput proteomics, the bottom-up approach has become a widely used method for the identification of proteins that is based on tryptic peptide MS/MS analysis. Separation methodologies that use IEF of tryptic peptides have recently been introduced and provide an extra dimension of peptide separation. In addition to its great fractionation capability, tryptic peptide prefractionation by IEF can also increase the protein identification success. The pI information of the peptide gained can be successfully used in a post-database search filtering step. We introduce a filtering algorithm that is based on the comparison of the experimental and theoretical pI's to validate peptide identifications by MS/MS data search engines.     

A new microcomputer program for processing data in neutron activation analysis

A new utility program for processing data in neutron activation analysis (NAA) has been developed for use on MS-DOS microcomputers. Peak areas are read from ASCII data files of gamma-ray spectra which have been processed by a Gaussian peak fitting program, GAMANAL-PC. Elemental concentrations are then calculated by this new program, QUACANAL, via a semi-absolute algorithm that uses pre-determined activation constants. User-defined ASCII library files are employed to specify the elements of interest required for analysis, and (n, p) and (n, ) interferences are taken into account. The program has been written in turbo PASCAL, is menu driven and contains options for processing data from cyclic NAA. An interactive philosophy has been used in designing the program.Sabbatical address for 1991/1992.     

De novo analysis of electron impact mass spectra using fragmentation trees

The automated fragmentation analysis of high resolution EI mass spectra based on a fragmentation tree algorithm is introduced. Fragmentation trees are constructed from EI spectra by automated signal extraction and evaluation. These trees explain relevant fragmentation reactions and assign molecular formulas to fragments. The method enables the identification of the molecular ion and the molecular formula of a metabolite if the molecular ion is present in the spectrum. These identifications are independent of existing library knowledge and, thus, support assignment and structural elucidation of unknown compounds. The method works even if the molecular ion is of very low abundance or hidden under contaminants with higher masses. We apply the algorithm to a selection of 50 derivatized and underivatized metabolites and demonstrate that in 78% of cases the molecular ion can be correctly assigned. The automatically constructed fragmentation trees correspond very well to published mechanisms and allow the assignment of specific relevant fragments and fragmentation pathways even in the most complex EI-spectra in our dataset. This method will be very helpful in the automated analysis of metabolites that are not included in common libraries and it thus has the potential to support the explorative character of metabolomics studies.     

The effects of fast neutron,gamma-ray and combined radiations on the thermal decomposition of ammonium perchlorate powder-aluminum particle mixtures

The thermal decomposition kinetics of irradiated and unirradiated ammonium perchlorate and ammonium perchlorate powder-aluminum particle mixtures has been studied by determining decomposition gas pressurevs. heating time with samples at a controlled temperature Qualitatively the radiation induced changes are similar to those obtained in previous studies on ‘pure’ ammonium perchlorate. The induction period is shortened and the acceleratory and decay period rate constants are increased. The data have been analyzed using Avrami-Erofeev kinetics. The results for pure unirradiated material are in accord with published results. The activation energies for the induction, acceleratory and decay periods for pure pellets were found to be 133.5±6.7, 131.8±6.7 and 127.2±6.7 kJ·mol, respectively. Samples were exposed to either a single gamma-ray irradiation, fission neutron irradiation followed by a gamma-ray irradiation, or to a proton irradiation. When compared on an equal energy deposited basis, the fast neutron induced changes are appreciably larger than the gamma-ray changes. However, the proton induced changes are comparable or slightly more than the gamma-ray effects. Some, or all, of the fast neutron effects can be attributable to the concentrated radiation damage ‘spikes’ along the path of lattice atom recoils. It is likely that these become thermal decomposition sites when the crystals are heated. Protons create fewer spikes than fast neutrons. Overall, the results indicate that any ammonium perchlorate-aluminum propellant mixtures that may be exposed to radiation environments, such as used in this study, should be subjected to a thorough radiation effects analysis if reliable performance is required. In celebration of the 60^th birthday of Dr. Andrew K. Galwey     

Analysis of gamma-ray spectra by using fast Fourier transform (author's transl)]

In order to simplify the mass data processing in a response matrix method for gamma-ray spectral analysis, a method using a Fast Fourier Transform devised. The validity of the method was confirmed by a computer simulation for spectra of a NaI detector. The method uses the fact that spectral data can be represented by Fourier series with reduced number of terms. The estimation of intensities of gamma-ray components is performed by a matrix operation using the compressed data of an observation spectrum and standard spectra in Fourier coefficients. The identification of gamma-ray energies is also easy. Several features in the method and a general problem to be solved in a response matrix method are described.