True Detection Limits Research Articles

Detection limit of computed tomography for hepatoblastoma pulmonary metastases: Based on total resection using indocyanine green fluorescence

BackgroundIntraoperative search for small pulmonary metastases of hepatoblastoma has been challenging; therefore, it has been difficult to determine the true detection limit of computed tomography (CT). This is the first report on the detection limit of CT for hepatoblastoma pulmonary metastases in patients who underwent resection of hepatoblastoma pulmonary metastases using indocyanine green fluorescence (ICGF). MethodsWe retrospectively reviewed the CT images of patients who underwent resection of hepatoblastoma pulmonary metastases using ICGF between January 2013 and November 2021 at a single children's hospital and compared them with pathological findings. ResultsOverall, 757 nodules were resected from 20 cases and 75 thoracotomies; 411 nodules were considered for the study and 286 were pathologically positive. The number of nodules classified by size in the pathological sections and the probability of CT detection were as follows: < 2 mm: CT-positive/pathology-positive, 43/144, 29.9 %; ≥ 2 and < 3 mm: 5/10, 50 %; ≥ 3 and < 4 mm: 20/27, 74.1 %; ≥ 4 and < 5 mm: 15/16, 93.8 %; ≥ 5 mm: 87/89, 97.8 %. Of 286 pathology-positive nodules, 59.4 % were CT-positive. With a cut-off value of 3 mm for tumor size, the proportion of CT-positive nodules was 92.4 %. Of 177 CT-positive nodules, 170 were pathologically positive. ConclusionsMore than 90 % of nodules > 3 mm were detectable on CT, whereas less than 30 % of pathologically positive nodules < 2 mm could be detected. In children with hepatoblastoma, a CT-positive pulmonary nodule, even if minute, is likely to be malignant and metastasis should be suspected.

Application of high-resolution 40.68 MHz radial-viewing inductively coupled plasma optical emission spectrometry in rhenium determination

The possibilities of 40.68 MHz radial-viewing inductively coupled plasma optical emission spectrometry equipped with a high-resolution spectrometer (spectral bandwidth = 5 pm) (HR-ICP-OES) were studied in the determination of rhenium in molybdenum and copper concentrates. By using equipment with a high spectral resolution, a hyperfine structure (HFS) of the most prominent lines of rhenium (i.e., Re II 197.248 nm, Re II 221.426 nm and Re II 227.525 nm) were registered. The HFS components, under high-resolution conditions, were used as separate prominent lines in order to circumvent spectral interferences in the presence of complex matrix containing Mo, Al, Ti, Fe, Mg, Ca and Cu. The Q-concept was applied for quantification of the spectral interferences and optimum line selection. Microwave acid digestion method was used as a sample dissolution procedure. The feasibility, accuracy and precision of the analytical results were experimentally demonstrated by certified reference materials from molybdenum and copper concentrates. Comparative data for true detection limits by using HR-ICP-OES 40.68 MHz ICP and Slurry sampling total reflection X-RAY fluorescence were presented in the determination of rhenium in CRM Molybdenum concentrate “CGL-202”.

Spectral interferences in the determination of rhenium in molybdenum and copper concentrates by inductively coupled plasma optical emission spectrometry (ICP-OES)

This paper deals with spectral interferences of complex matrix containing Mo, Al, Ti, Fe, Mg, Ca and Cu in the determination of rhenium in molybdenum and copper concentrates by inductively coupled plasma optical emission spectrometry (ICP-OES). By radial viewing 40.68MHz ICP equipped with a high resolution spectrometer (spectral bandwidth=5 pm) the hyperfine structure (HFS) of the most prominent lines of rhenium (Re II 197.248nm, Re II 221.426nm and Re II 227.525nm) was registered. The HFS components under high resolution conditions were used as separate prominent line in order to circumvent spectral interferences. The Q-concept was applied for quantification of spectral interferences.The quantitative databases for the type and the magnitude of the spectral interferences in the presence of above mentioned matrix constituents were obtained by using a radial viewing 40.68MHz ICP with high resolution and an axial viewing 27.12MHz ICP with middle resolution. The data for the both ICP-OES systems were collected chiefly with a view to spectrochemical analysis for comparing the magnitude of line and wing (background) spectral interference and the true detection limits with spectroscopic apparatus with different spectral resolution.The sample pretreatment methods by sintering with magnesium oxide and oxidizing agents as well as a microwave acid digestion were applied.The feasibility, accuracy and precision of the analytical results were experimentally demonstrated by certified reference materials.

True detection limits in an experimental linearly heteroscedastic system. Part 1

Using a lab-constructed laser-excited filter fluorimeter deliberately designed to exhibit linearly heteroscedastic, additive Gaussian noise, it has been shown that accurate estimates may be made of the true theoretical Currie decision levels ( Y C and X C ) and true Currie detection limits ( Y D and X D ) for the detection of rhodamine 6 G tetrafluoroborate in ethanol. The obtained experimental values, for 5% probability of false positives and 5% probability of false negatives, were Y C = 56.1 mV, Y D = 125. mV, X C = 0.132 μg /mL and X D = 0.294 μg /mL. For 5% probability of false positives and 1% probability of false negatives, the obtained detection limits were Y D = 158. mV and X D = 0.372 μg /mL. These decision levels and corresponding detection limits were shown to pass the ultimate test: they resulted in observed probabilities of false positives and false negatives that were statistically equivalent to the a priori specified values.

True detection limits in an experimental linearly heteroscedastic system.: Part 2

Despite much different processing of the experimental fluorescence detection data presented in Part 1, essentially the same estimates were obtained for the true theoretical Currie decision levels ( Y C and X C ) and true Currie detection limits ( Y D and X D ). The obtained experimental values, for 5% probability of false positives and 5% probability of false negatives, were Y C = 56.0 mV, Y D = 125. mV, X C = 0.132 μg/mL and X D = 0.293 μg/mL. For 5% probability of false positives and 1% probability of false negatives, the obtained detection limits were Y D = 158 . mV and X D = 0.371 μg/mL. Furthermore, by using bootstrapping methodology on the experimental data for the standards and the analytical blank, it was possible to validate previously published experimental domain expressions for the decision levels ( y C and x C ) and detection limits ( y D and x D ). This was demonstrated by testing the generated decision levels and detection limits for their performance in regard to false positives and false negatives. In every case, the obtained numbers of false negatives and false positives were as specified a priori.

Spectral interferences in the determination of traces of scandium, yttrium and rare earth elements in “pure” rare earth matrices by inductively coupled plasma atomic emission spectrometry: Part VII — Terbium, Dysprosium, Holmium and Thulium

This article is the seventh part of a series of papers discussing the spectral interferences of rare earth elements (REEs) in ICP-AES. Radial viewing 27.12 MHz inductively coupled plasma atomic emission spectrometry (ICP-AES) was used in the determination of scandium, yttrium and rare earth elements in Tb 2O 3, Dy 2O 3, Ho 2O 3 and Tm 2O 3 as “pure” rare earth matrices. The quantification of the interferences in terms of Q-values for line interference Q I( a) and wing background interference Q W(Δ λ a) were used in accordance with Boumans and Vrakking [Spectrochim. Acta Part B 43 (1988) 69]. The “best” analysis lines from point of view of spectral interferences were selected. The true detection limits by using the “best” analysis lines were calculated.

Sample Preparation for Evaluation of Detection Limits in X-ray Fluorescence Spectrometry

The influence of analyte mass concentration on determination of detection limits in X-ray fluorescence spectrometry has been investigated experimentally. Both the total reflection X-ray fluorescence (TXRF) and the conventional energy-dispersive X-ray fluorescence techniques have been used to derive the dependence of analyte mass concentration on the values of detection limits. Results obtained indicate that values of detection limits are optimum, or in other words, they are closer to the true detection limit of the technique, when analyte concentrations are in the range of 10 times of the detection limit.

Determination of arsenic, mercury, selenium, thallium, tin and bismuth in environmental materials by inductively coupled plasma emission spectrometry

This paper deals with spectral interference in radial—viewing Inductively Coupled Plasma Atomic Emission Spectrometry in the determination of As, Hg, Se, Tl, Sn and Bi in environmental materials. The spectral interferences, in the presence of Al, Ca, Mg, Fe and Ti as matrix constituents, around the prominent lines of analytes with wavelengths below 200 nm and up to 320 nm, were studied. The Q-concept was applied for quantification of spectral interferences in the presence of multi-component environmental matrix. These data were used for both quantitative line selection and calculation of the true detection limits by the “best” analysis lines. The detection limits obtained in the present paper varied from 0.3 to 0.9 μg g −1.

Continuous wave cavity ring-down spectroscopy applied to in situ detection of dinitrogen pentoxide (N2O5)

We describe an instrument using cavity ring-down spectroscopy (CRDS), an ultrasensitive detection method, to detect NO3 and N2O5 (via thermal dissociation to NO3 at 80 °C). We use continuous-wave (cw) cavity ring-down spectroscopy, allowing a highly reliable diode laser to act as the light source. This instrument uses all solid-state laser and optical components, and it is compact, portable, and power efficient. Advantages and disadvantages of cw CRDS compared to pulsed CRDS are discussed. Inlet losses and possible interferences were extensively investigated. We show field observations of N2O5 mixing ratios in ambient air. Dinitrogen pentoxide was measured because low ambient temperatures shift the equilibrium between NO3, NO2, and N2O5 strongly towards N2O5. Therefore, only N2O5 is assumed to be present in significant quantities in Fairbanks, AK, during winter. From these data, we identify times where the N2O5 mixing ratio must be zero (due to the absence of ozone indicating presence of NO) and use these time periods to measure the system’s operational detection limit. The 2σ detection limit for N2O5 is 2.4 parts per trillion by volume (pptv) in a 25 s average. Prediction of the N2O5 detection limit from estimates of ring-down signal noise indicates a detection limit of 1.6 pptv, in the same averaging period. The observed detection limit is about 50% larger than the predicted detection limit, indicating that other noise sources affect the true detection limit. A similar instrument using pulsed CRDS was described in the last year, and we compare our instrument to this instrument for detection of N2O5.

Determination of barium, chromium, cadmium, manganese, lead and zinc in atmospheric particulate matter by inductively coupled plasma atomic emission spectrometry (ICP-AES)

The present paper has shown that the Q concept, as proposed by P.W.J.M. Boumans, J.J.A.M. Vrakking, Spectrochim. Acta Part B 43 (1988) 69, can be used as a basic methodology in the determination of Ba, Cr, Cd, Mn, Pb and Zn in pairs of atmospheric particles by inductively coupled plasma atomic emission spectrometry (ICP-AES). The data base of Q values for line interference [ Q Ij (λ a )] and Q values for wing background interference [ Q WJ (Δλ a )] were obtained in our former work [N. Daskalova, Iv. Boevski, Spectral interferences in the determination of trace elements in environmental materials by inductively coupled plasma atomic emission spectrometry, Spectrochim. Acta Part B 54 (1999) 1099–1122]. The samples of atmospheric particles were collected by the Bergerhoff method. The ICP-AES determination was performed after sample digestion with aqua regia. Q values were used for the calculation of both the total interfering signal under the analysis lines and the true detection limits, depending on the matrix constituents in the different samples. Comparative data for the concentration of analytes were obtained by flame atomic absorption spectrometry (FAAS) and direct current arc atomic emission spectrographic method (dc arc-AES).

True detection limit of rare earth elements in atomic emission analysis with an arc two-jet plasmatron

The “true detection limit” CL,true was measured by a method proposed by Boumans et al. for 10 prominent lines of La, Ce, Pr, Nd and Sm, the most abundant rare earth elements (REEs) in geological samples. It is demonstrated how spectral interferences can increase of CL,true. The spectra were excited in an argon arc plasma jet with evaporation powders of five complex natural samples. The data show that there is a significant increase of CL,true in real samples containing large concentrations of such elements as Ti, Zr, Cr, Nb, Ta and REEs emitting complex spectra.

Application of inductively coupled plasma atomic emission spectrometry in analytical control of single crystals of potassium titanylphosphate: spectral interferences, line selection, detection limits and trace element determination

The present paper is a new application of inductively coupled plasma atomic emission spectrometry (ICP-AES) to the determination of Na, Cr, Mn, Fe, Co, Ni, Al, Mg, Rh, W, Pt, Ge, Rb, Zr, Nb, Ce, Nd, Eu, Tb, Er and Yb, present as dopants or impurities in single crystals of potassium titanylphosphate (KTP). The investigations cover: (a) spectral data for potassium, titanium and phosphorus as interferents for 400 pm wide windows centred (± 200 pm) around the prominent lines of the analytes; (b) a data base of Q-values for line interference ( Q I) and Q-values for wing (background) interference ( Q W) for two values of the excitation temperature—6200 K and 7200 K; and (c) detection limits for the dopants and impurities in the presence of 8 mg ml −1 KTP in solution, measured by using the “true detection limit” criterion as proposed by Boumans and Vrakking [Spectrochim. Acta, 42B (1987) 819; 43B (1988) 69]. The lines with the lowest values of true detection limits were selected for analyte determination. Using the ICP-AES method, data were obtained for the average dopant content in the single crystals of KTP, the dopant distribution along the growth axis of the crystals and the impurity content. The precision of the method is characterised by an RSD of 2–6%, the accuracy of the method was assessed by comparison with a flame AAS method. This article is an electronic publication in Spectrochimica Acta Electronica (SAE), the electronic section of Spectrochimica Acta, Part B (SAB). The hardcopy text is accompanied by a disc with data and text files. The data files comprise in particular the tabular material of this article in electronic form.

Definition of Lower Limits for Airborne Particle Analyses Based on Counts and Recommended Reporting Conventions

In all of the standard methods for counting asbestos fibres or structures on filters by microscopy, a lower limit is established, below which a count obtained using the method is considered to be practically indistinguishable from background. In the phase contrast microscopy (PCM) method most widely used in the U.S. (NIOSH, 1994), that lower limit is stated as the Limit of Detection and is quantitatively given at 7 fibres mm (roughly equivalent to 5.5 fibres/100 fields counted). In the most widely used (in the U.S.) transmission electron microscopy (TEM) method (the AHERA Method—EPA, 1987), the background level for asbestos structures is stated as 70 asbestos structures mm filter surface, which is the approximate equivalent of four structures counted/10 electron microscope grid openings. In some TEM methods promulgated by the American Society for Testing and Materials (ASTM), the limit of detection has been explicitly stated as the counting of four structures (ASTM, 1996). Relatively little attention has been paid to this issue in the analysis of environmental asbestos samples and it is generally not recognised that such arbitrary detection limits across the universes of sample media and laboratory cleanliness and technical proficiencies of field and laboratory personnel are likely to misstate the true detection limits. In fact, the detection limit for any analytical method will necessarily be a function of both the method itself and the application of that method to obtain sample blank levels. Further, when faced with arbitrary detection limit language, some analysts do not report actual results for samples for which the detection limits are not attained, but simply report that the results are less than the detection limit. In this paper both the recommended procedure to determine the detection limit, and the recommended reporting conventions are given.

Computer expert system for spectral line simulation and selection in inductively coupled plasma atomic emission spectrometry

This paper is an electronic publication in Spectrochimica Acta Electronica (SAE), the electronic section of Spectrochimica Acta, Part B (SAB). This hardcopy text, comprising the main body and an appendix, is accompanied by a disk with programs, data files and a brief manual. The main body discusses purpose, design principle and usage of the computer software for the inductively coupled plasma atomic emission spectrometry (ICP-AES) expert system. The appendix provides a brief instruction on the manipulation of the demonstration program and relevant information on accessing the diskette. The computer software of the expert system has been developed in C++ language to simulate spectra and to select analytical lines in ICP-AES. This expert system is based on a comprehensive model of non-LTE ICP-AES, which includes expertise in plasma discharges, analyte ionization and excitation, and spectral-line shapes. The system also provides several databases in which essential elemental and spectral data are stored. A logic reasoning engine is utilized for selection of the best analytical line with a main criterion of minimizing the true detection limit. The system is user-friendly with pop-up menus, an editor for database operation, and a graphic interface for the display of simulated spectra. The system can simulate spectra and predict spectral interferences with good accuracy.

Spectral interferences in the determination of traces of scandium, yttrium and rare earth elements in “pure” rare earth matrices by inductively coupled plasma atomic emission spectrometry Part III. Europium

This paper is the third part of a series of papers dealing with spectral interferences of rare earth elements (REEs) in inductively coupled plasma atomic emission spectrometry (ICP-AES). The present article shows: (a) the spectral data of europium interferent for 200 pm wide windows centred (±100 pm) about prominent lines of scandium, yttrium and REEs; (b) the database of Q values for line interference ( Q l ) and Q values for (wing) background interference ( Q w); (c) the detection limits measured by using the “true detection limit” criterion as proposed by P.W.J.M. Boumans and J.J.A.M. Vrakking (Spectrochim. Acta Part B, 42 (1987) 819; 43 (1988) 69). Different possibilities for improvement of the true detection limits are discussed: the use of equipment of high resolving power, the application of multicomponent analysis (MCA) techniques and preliminary separation of the matrix component combined with preconcentration of trace REEs. This article is an electronic publication in Spectrochimica Acta Electronica (SAE), the electronic section of Spectrochimica Acta Part B (SAB). The hard copy text is accompanied by a disk with data and text files. The data files comprise in particular the tabular material of this article in electronic form.

Precision-based optimization of multicomponent analysis in inductively coupled plasma mass spectrometry

To arrive at rapid, precise and automated survey analysis in inductively coupled plasma mass spectrometry (ICP-MS), the measurement and data reduction of full-range mass scans ( m z = 6−238 ) have been investigated. The way mass spectra are scanned has been optimized with respect to short- and long-term precision. Three internal standards are needed to correct for changes in mass bias. An expression for the precision or relative standard deviation (RSD) as a function of the measured mass intensity has been derived in terms of source flicker and ion shot noise. Our formerly introduced multicomponent analysis approach has been optimized with respect to the construction of the modelling matrix. An automated interpretation system with a data base of interferents has been incorporated in the software. The optimization procedures use criteria based on the RSD function. Detection limits for Hf in solutions for the pure component and for the magnetic material NdFeB characterize the final approach. By only using the information available in the full-range mass scan, the approach results in concentrations and true detection limits in the sample solution for all elements.

Peak purity assessment by matrix projection for spectral line selection and background correction in inductively coupled plasma optical emission spectrometry

This paper describes an improvement of the procedure, proposed previously (Spectrochim. Acta, Part B, 48 (1993) 1517), to provide information about multiplicative and spectral interferences at lines selected for the analysis of samples. The new version of the procedure only requires intensity scans across an analyte line when three solutions are aspirated: a standard solution, the sample solution and the sample spiked with the analyte standard solution. The third solution can be omitted if multiplicative interference is not of interest. Like the initial method, the present procedure does not require or assume information about the sample composition nor is the preparation of solutions of suspected interferents required. Figures of merit, namely the structured background factor, and the overall spectral interference have been devised and are used with the true detection limit at a line for line evaluation and selection. As the nonanalyte concomitant contribution to the measured spectrum is estimated, automatic background correction is possible. The proposed method not only allows selection of the spectral line, but can give a good estimate of the analyte concentration prior to a full quantitative analysis.

Quantitative line selection with the Kalman filter approach for inductively coupled plasma atomic emission spectrometry

With the Kalman filter approach, the true detection limit (i.e. the detection limit in the sample solution) only depends on the height of the total background signal, and is not determined by the uncertainties in interfering background signals. Based on the background equivalent interferent concentration, the true detection limit can be directly estimated in sample solutions containing various amounts of interferent. This eases the application of the true detection limit as quantitative criterion for line selection. Following this approach, quantitative line selection is demonstrated for Pb and Cd determinations in river sediments (Fe interferences).

Spectral interferences in the determination of traces of scandium, yttrium and rare earth elements in “pure” rare earth matrices by inductively coupled plasma atomic emission spectrometry—II: Praseodymium and samarium

This paper is the second part of a series of papers dealing with mutual spectral interferences of rare earth elements (REEs) in inductively coupled plasma atomic emission spectrometry (ICP-AES). The present article covers: (a) the spectral data of praseodymium and samarium interferents for 200 pm wide windows centred (± 100 pm) about prominent lines of scandium, yttrium and REEs; (b) the data base of Q values for line interference ( Q 1) and Q values for (wing) background interference ( Q w); and (c) the detection limits measured by using the “true detection limit” criterion as proposed by Boumans and vrakking [ Spectrochim. Acta 42B, 819 (1987); 43B, 69 (1988)]. The lines with the lowest values of true detection limits for praseodymium and samarium matrices were chosen for analysis. This article is an electronic publication in Spectrochimica Acta Electronica (SAE), the electronic section of Spectrochimica Acta Part B (SAB). The hardcopy text is accompanied by a disk with data and text files. The data files comprise in particular the tabular material of this article in electronic form.

Spectral interferences in the determination of traces of scandium, yttrium and rare earth elements in “pure” rare earth matrices by inductively coupled plasma atomic emission spectrometry-I. Cerium, neodymium and lanthanum matrices

The present paper deals with spectral interferences from cerium, neodymium and lanthanum on prominent lines of scandium, yttrium and rare earth elements (REE). The “true detection limit” criterion was used for rational wavelength line selection as proposed by boumans and vrakking [ Spectrochim. Acta 42B, 819 (1987); 43B, 69 (1988)]. Analysis lines selected for cerium and neodymium matrices suffered both wing and line interferences. In the case of a lanthanum matrix, it is possible to choose mostly analysis lines that are free of line interference and negligible wing interference. The high degree of spectral interferences with a cerium or neodymium matrix significantly worsens the true detection limits. This article is an electronic publication in Spearochimica Acta Electronica (SAE), the electronic section of Spectrochimica Acta Part B (SAB). The hardcopy text is accompanied by a disk with data and text files. The data files comprise in particular the tabular material of this article in electronic form.