Full-scan Method Research Articles

B-150 Chromatographic Separation and Quantitation of Human Insulin and Lispro Analog in Serum Using Liquid Chromatography High-Resolution Mass Spectrometry

Abstract Background Factitious hypoglycemia, a deliberate attempt to induce low blood glucose levels occurring secondary to the surreptitious administration of exogenous insulin, can be difficult to diagnose due to a variety of factors including the increased use of synthetic insulin analogs in clinical practice. Traditional insulin immunoassays demonstrate variable cross-reactivity with commonly prescribed insulin analogues and their metabolites, making it difficult to measure specific analogs. The development of liquid chromatography high resolution accurate mass (LC-HRAM)-mass spectrometry (MS) assays has largely circumvented the limitations of traditional immunoassays for detection and quantitation of insulin analogs. Analytical challenges remain, however, specifically in differentiating lispro, an isomeric human insulin analog formed by the transposition of proline and lysine near the C-terminal end of the B chain, from human insulin in patient samples due to the equivalent mass-to-charge ratios of their precursor ions. Methods Immunoaffinity purification of insulin from calibrators and quality control material prepared by spiking insulin-depleted serum with pharmaceutical insulin preparations, as well as patient samples, was performed using tips coupled with anti-insulin monoclonal antibody. An automated liquid handler was programmed to perform aspiration and dispense cycles. Eluate from the purification protocol was submitted for analysis using a TLX-2 multiplex LC system paired with a Thermo Scientific Q Exactive Plus mass spectrometer. Various HPLC column chemistries were evaluated, a column passivation procedure was established, and column heater temperature was optimized to identify a combination of parameters yielding the best chromatographic separation of human insulin and lispro. Additionally, parallel reaction monitoring (PRM) targeted tandem mass spectrometry (MS/MS) analysis was utilized in combination with the full scan data to increase specificity through the monitoring of fragment ions produced from human insulin and each insulin analog. Results We found that a 1000 Å Diphenyl, 2.7 µm, 2.1 x 100 mm analytical column in a column heater maintained at a temperature of 80°C allowed for human insulin and lispro to be differentiated as two chromatographically separated extracted ion chromatographic peaks (XICs) and quantified down to 2.5 mcIU/mL with near-baseline separation. Before use, the column required passivation with a high protein buffer (0.05% bovine serum albumin in 20% acetonitrile [ACN] + 0.2% acetic acid) followed by increasingly organic buffers (20% ACN + 0.2% acetic acid and 50% ACN + 0.2% acetic acid). MS/MS was used to confirm the presence of analogs detected. Conclusions The LC-HRAM-MS method described here, coupled with optimized column chemistry, column passivation, and proper column temperature control allows for chromatographic separation of human insulin and lispro. Incorporating a PRM scan into the mass spectrometry full scan method provides confirmation of the insulin detected in the XICs. The results obtained from preliminary studies suggest this method is appropriate for use to facilitate the clinical investigation of suspected factitious hypoglycemia with the ability to differentiate isomeric compounds, such as human insulin and lispro.

Unraveling the potential of segment scan mass spectral acquisition for chemical isotope labeling LC-MS-based metabolome analysis: Performance assessment across different types of biological samples

BackgroundChemical isotope labeling (CIL) LC-MS is a powerful tool for metabolome analysis with high metabolomic coverage and quantification accuracy. In CIL LC-MS, the overall metabolite detection efficiency using Orbitrap MS can be further improved by employing a segment scan method where the full m/z range is divided into multiple segments for spectral acquisition with a significant increase in the in-spectrum dynamic range. Considering the metabolic complexity in different types of biological samples (e.g., feces, urine, serum/plasma, cell/tissue extracts, saliva, etc.), we report the development and evaluation of the segment scan method for metabolome analysis of different sample types. ResultsIt was found that sample complexity significantly influenced the performance of the segment scan method. In metabolically complex samples such as feces and urine, the method yielded a substantial increase (up to 94 %) in detected peak pairs or metabolites, compared to conventional full scan. Conversely, less complex samples like saliva exhibited more modest gains (approximately 25 %). Based on the observations, a 120-m/z segment scan method was determined as a routine approach for CIL LC-Orbitrap-MS-based metabolomics with good compatibility with different types of biological samples. For this method, a further investigation on relative quantification accuracy was done. The peak area ratios of 12C-/13-labeled metabolites were slightly reduced with 72%–84 % of peak pairs falling within the ±25 % range of the anticipated peak ratio of 1.0 among different samples, as opposed to 81%–90 % in the full scan, which was attributed to the inclusion of more low-abundance peak pairs within the narrow MS segments. However, the overall peak ratio measurement precision was not significantly affected by the segment scan. Significance and noveltyThe segment scan method was found to be useful for CIL LC-Orbitrap-MS-based metabolome analysis of different types of samples with significant improvement in metabolite detectability (25–94 % increase), compared to the conventional full scan method.

Fault Coverage Testing on the ISCAS’89 S1423 Sequential Circuit using Scan Based Design and Synopsis Tetramax

We tested the ISCAS'89 S1423 series with a scan design method, both non-scan, full-scan, and partial-scan, but for the partial-scan, the method we propose uses a structured random approach. The purpose of this study is to determine the evaluation and performance with the best computational time with the proposed method to produce high fault coverage results. Testing the ISCAS'89 S1423 circuit in the form of verilog was carried out using tetramax synopsis, the partial-scan test requires a strategy in determining the flip flop to be used as a scannable flip flop, the test results using the full scan method produce 100% test coverage and fault coverage, but this method provides gate overhead loss of 24.06% and slower chip performance. To reduce the gate overhead loss, a partial-scan method will be applied with the approach of choosing from 74 DFF which will be used as scannable flip flops, the test with the best results we did through the 37 DFF approach with the highest input obtained test coverage of 98.17% and fault coverage 96.76% with 171.11 CPU Time with gate overhead reduced by 12.03%. The next approach with the best results with the approach of 50 DFF highest output plus DFF which is not self-loop obtained test coverage of 99.24% and fault coverage of 98.47% with gate overhead successfully reduced by 16.26% with CPU Time 43.39.

Quantitative evaluation of the composition of synthetic cannabinoid receptor agonists (SCRA) in infused papers and herbal materials seized in Brazilian prisons

This study describes the identification and quantification of synthetic cannabinoid receptor agonists (SCRA) in infused paper and herbal material samples, seized in prisons located in São Paulo state, Brazil. The selected samples (23 infused paper and 3 herbal material samples) were previously analyzed by the São Paulo State Police, in a qualitative analysis by gas chromatography–mass spectrometry (GC–MS) using full-scan and library search for identification. Afterward, these samples were analyzed by liquid chromatography-tandem mass spectrometry in a triple quadrupole (LC-MS/MS) system operating in MRM mode for determination of the majority and the possible minority SCRA present in the samples. For the LC-MS/MS analysis the samples were extracted with methanol and diluted in a proportion of 1:1000 and 1:10,000. All substances identified by GC-MS were also identified by LC-MS/MS, but not the opposite, showing GC-MS full-scan method employed were unable to detect those SCRA presented in lower concentration levels. The presence of a single SCRA in the samples was observed in 11 samples (27.5%), while in 29 samples (72.5%) two or more SCRA were identified. The SCRA most frequently detected in the samples were MDMB-4en-PINACA and ADB-BUTINACA, present in 72% and 70% of the samples, respectively. The concentration of SCRA shown great variability, ranging from 0.2 μg/infused paper to 3000 μg/infused paper. In cases with more than one SCRA detected, the minority compounds did not exceed the concentration of 50 μg/infused paper. Comparing two different samples of a single seizure it was possible to identify the same substances but in different concentration levels, or different compositions (mixtures). The highest concentration of SCRA present in the infused papers was for the cases involving MDMB-4en-PINACA as the major compound, reaching until 3000 μg/infused paper, but this SCRA was also found as minority in other cases, with concentrations as low as 0.9 μg/infused paper. Among all samples, 4F-MDMB-BUTICA was detected in only one case, at a concentration of 125 μg/infused paper. For the three samples of plant material, ADB-BUTINACA appears as the major compound, with the presence of other minor SCRA ranging from 0.2 to 5 μg/mg. These results shows that the studied samples did not present homogeneity in the composition and concentration levels, even when comparing a single case, but it seems that some SCRA are commonly found together. The presence of different SCRA in the same sample may contribute to the increase in the toxicity of these compounds, which reinforces the need to obtain quantitative and qualitative data from the seized samples.

High sensitivity and high-confidence compound identification with a flexible BoxCar acquisition method

Liquid chromatography-mass spectrometry (LC-MS) is in wide use for compound identification and quantification in complex matrices. While advances in mass spectrometry and the incorporation of new acquisition methods have resulted in greatly improved detection, there is an ongoing need to expand the limits of highly sensitive and confident identification of low abundance species in complex samples. The data acquisition method known as “BoxCar” was originally designed to achieve in-depth proteome profiling on an Orbitrap mass analyzer by decomposing ions into segments with narrow m/z windows. Using this method, selected segments are packaged in C-trap and all ions are then sent to Orbitrap for detection. In this study, we developed a flexible BoxCar acquisition method by placing more segments in the low m/z range for small molecule profiling. This new MS1 acquisition method was successfully integrated with iterative data dependent MS/MS acquisition by generating an inclusion list of ions detected in the flexible BoxCar to trigger the fragmentation of parent ions. The developed acquisition method was applied to the analysis of cell culture media, which plays a key role in antibody production. This challenging goal is of critical importance, as none of the currently available methods provide a comprehensive understanding of how individual components, metabolites, and impurities associated with the cell culture process might influence recombinant antibody production. Even when present at relatively low abundance, some components or impurities in the cell culture medium could have a profound impact on the quality and titer of the antibodies produced. The complex soy hydrolysate cell culture medium used in antibody generation has not been fully characterized. Using the developed flexible BoxCar acquisition method, we achieved 90 % higher sensitivity in experiments designed to detect spiked chemical substances at low abundance at the MS1 level compared to the full scan method. Iterative data-dependent acquisition (DDA) based on the targeted inclusion list generated much higher quality MS2 spectra and facilitated confident identification of low-abundance compounds. Our method achieved a 50 % increase in MS2 coverage of compounds present at low concentrations compared to conventional DDA methods. The results of our study demonstrate that this data acquisition workflow can be easily operated on Orbitrap mass spectrometers and used as a highly effective approach to improve sensitivity and high-confidence small molecule profiling in soy hydrolysate-based cell culture medium and thus provides significant support for therapeutic monoclonal antibody production.

Studying the Complexity of Biomass Derived Biofuels

Biofuel produced from biomass pyrolysis is a good example of a highly complex mixture. Detailed understanding of its composition is a prerequisite for optimizing transformation processes and further upgrading conditions. The major challenge in understanding the composition of biofuel derived from biomass is the wide range of compounds with high diversity in polarity and abundance that can be present. In this work, a comprehensive analysis using mass spectrometry is reported. Different operation conditions are studied by utilizing multiple ionization methods (positive mode atmospheric pressure photo ionization (APPI), atmospheric pressure chemical ionization (APCI) and electrospray ionization (ESI) and negative mode ESI) and applying different resolving power set-ups (120 k, 240 k, 480 k and 960 k) and scan techniques (full scan and spectral stitching method) to study the complexity of a pyrolysis biofuel. Using a mass resolution of 960 k and the spectral stitching scan technique gives a total of 21,703 assigned compositions for one ionization technique alone. The number of total compositions is significantly expanded by the combination of different ionization methods.

Cooperation-Assisted Spectrum Handover Mechanism in Vehicular Ad Hoc Networks

This paper proposes a cooperation-assisted spectrum handover (CASH) scheme in vehicular ad hoc networks (VANETs). In CASH, each vehicle uses cognitive radio technology to collect the surrounding spectrum information, computes the stability of the spectrum, exchanges neighbor information by vehicle-to-vehicle collaboration technology, and then executes a partial prescan mechanism to reduce the handover delay. The proposed method can improve the spectrum utilization, shorten the delay time of the spectrum handover, and reduce the total number of handovers. Finally, the simulation results show that the proposed method outperforms other existing schemes. In spectrum utilization, CASH is about 20% better than that of the traditional full scan method. In average scan time, the time of CASH is about 5 times less than the time of the traditional full scan method. In total number of handovers, CASH improves the performance of the full scan scheme by 33%.

Analysis of hydroxylated phenylalkylamine stimulants in urine by GC-APPI-HRMS.

A gas chromatography-atmospheric pressure photoionization-high-resolution mass spectrometry (GC-APPI-HRMS) method was developed for the determination of eight phenylalkylamine stimulants in urine samples. Spiked urine samples were hydrolyzed, processed by solid-phase extraction, and derivatized before analysis. Two derivatization reactions were studied: the formation of trimethylsilyl (TMS) derivatives with N-methyl-N-trimethylsilyl trifluoroacetamide (MSTFA) and trimethylsilyl/trifluoroacetyl (TMS/TFA) derivatives with MSTFA and N-methyl-bis (trifluoroacetamide) (MBTFA) as derivatization reagents. Gas chromatography of both derivatives was performed with a 100% dimethylsiloxane column and a good separation of all isomeric compounds was achieved. To maximize the signal of the protonated molecule [M+H]+, the APPI most critical parameters were optimized. Three solvents were tested as dopant agents, with acetone yielding the lower in-source collision-induced dissociation (CID) fragmentation. The acquisition was performed in full scan and product ion scan (parallel reaction monitoring, PRM) using a quadrupole-Orbitrap mass analyzer (35,000 FWHM at m/z 200) in positive ion detection mode. At the optimal working conditions, the full scan method was evaluated for the fulfillment of identification requirements in doping analysis. Selectivity, limits of detection, matrix effect, and precision were estimated to validate the method for confirmation purposes and its applicability was tested by the analysis of spiked samples as well as by the analysis of samples obtained after the administration of some of the compounds to healthy volunteers. Results were compared with those obtained by GC-electron ionization-MS, demonstrating that the GC-APPI-HRMS method improved selectivity and sensibility, achieving lower limits of detection and satisfactory reproducibility.

Identification of critical links in a large-scale road network considering the traffic flow betweenness index.

The traditional full-scan method is commonly used for identifying critical links in road networks. This method simulates each link to be closed iteratively and measures its impact on the efficiency of the whole network. It can accurately identify critical links. However, in this method, traffic assignments are conducted under all scenarios of link disruption, making this process prohibitively time-consuming for large-scale road networks. This paper proposes an approach considering the traffic flow betweenness index (TFBI) to identify critical links, which can significantly reduce the computational burden compared with the traditional full-scan method. The TFBI consists of two parts: traffic flow betweenness and endpoint origin–destination (OD) demand (rerouted travel demand). There is a weight coefficient between these two parts. Traffic flow betweenness is established by considering the shortest travel-time path betweenness, link traffic flow and total OD demand. The proposed approach consists of the following main steps. First, a sample road network is selected to calibrate the weight coefficient between traffic flow betweenness and endpoint OD demand in the TFBI using the network robustness index. This index calculates changes in the whole-system travel time due to each link’s closure under the traditional full-scan method. Then, candidate critical links are pre-selected according to the TFBI value of each link. Finally, a given number of real critical links are identified from the candidate critical links using the traditional full-scan method. The applicability and computational efficiency of the TFBI-based approach are demonstrated for the road network in Changchun, China.

Determining pesticide residues in wheat flour by ultrahigh-performance liquid chromatography/quadrupole time-of-flight mass spectrometry with QuEChERS extraction

ABSTRACTPesticides are used to increase crop yields and preserve quality by protecting crops against pests; however, their overuse can adversely affect human health and the environment. Herein, we report the development of a multi-pesticide screening method using optimized QuEChERS coupled with liquid chromatography/quadrupole time-of-flight (QTOF) mass spectrometry for the analysis of 13 pesticides in wheat flour. Mass accuracies with errors of less than 2.4 ppm were obtained for all analysed pesticides, and the method provided satisfactory recovery and linearity. Repeatabilities of 0.3–12.7% and reproducibilities of 2.5–15.2% were observed in full-scan TOF mode. The performance of the developed full-scan TOF method was compared to that obtained in high-resolution multiple reaction monitoring (MRM-HR) mode. The limits of quantification for the full-scan TOF and MRM-HR modes ranged from 2 to 10, and 3 to 9 μg kg−1, respectively. The two quantification methods exhibited high sensitivities (limit of detections: 1–3 μg kg−1 in full-scan TOF, and 1–3 μg kg−1 for MRM-HR mode). No pesticide residues were detected when the developed method was applied to 22 real wheat flour samples.

Interobserver Variability in Mitotic Count for Meningioma Grading: How Can We Reduce It?

To evaluate the interobserver variability in determining the number of mitoses in 10 high-power field (HPF) and thus the tumor grade, and to investigate how to reduce grade discordance between the observers and the most useful method to identify the patients who would receive an additional treatment. Two hundred and seventy cases with meningioma were re-evaluated by three experienced pathologists and five senior residents. They determined the number of mitotic figures in 10 HPF in each slide. Re-evaluation of the cases, which were found of different grades from the reference observers was requested by full scan method. Statistical analysis was performed by using SPSS V23.0. A moderate agreement was found between the observers and the reference observer. After the evaluation of mitotic activity with the full scan method, the mean numbers of mitoses found by the observers in 10 HPF were increased. In the first evaluation, 4?6 cases were defined as Grade II by the observers. Whereas, 23?27 cases were defined as Grade II after the full scan method. If there are less than 16 mitotic figures throughout the slide, it is more difficult to find the 10 HPF including 4 or more mitosis. Interobserver variability in mitotic figure counting can be reduced by full scan method, and examining the hematoxylin and eosin stained slides by the full scan method helps us to determine the true histologic grade of meningiomas in most cases, who would receive an additional treatment.

Volatile Hydrocarbon Analysis in Blood by Headspace Solid-Phase Microextraction: The Interpretation of VHC Patterns in Fire-Related Incidents.

A headspace solid-phase microextraction (HS-SPME) technique was used to quantitate the concentration of volatile hydrocarbons from the blood of cadavers by cryogenic gas chromatography-mass spectroscopy. A total of 24 compounds including aromatic and aliphatic volatile hydrocarbons were analyzed by this method. The analytes in the headspace of 0.1 g of blood mixed with 1.0 mL of distilled water plus 1 µL of an internal standard solution were adsorbed onto a 100-µm polydimethylsiloxane fiber at 0°C for 15 min, and measured using a GC-MS full scan method. The limit of quantitation for the analytes ranged from 6.8 to 10 ng per 1 g of blood. This method was applied to actual autopsy cases to quantitate the level of volatile hydrocarbons (VHCs) in the blood of cadavers who died in fire-related incidents. The patterns of the VHCs revealed the presence or absence of accelerants. Petroleum-based fuels such as gasoline and kerosene were differentiated. The detection of C8-C13 aliphatic hydrocarbons indicated the presence of kerosene; the detection of C3 alkylbenzenes in the absence of C8-C13 aliphatic hydrocarbons was indicative of gasoline; and elevated levels of styrene or benzene in the absence of C3/C4 alkylbenzenes and aliphatic hydrocarbons indicated a normal construction fire. This sensitive HS-SPME method could help aid the investigation of fire-related deaths by providing a simple pattern to use for the interpretation of VHCs in human blood.

Metasystem approach to increase the load factor FMS

The work is devoted to increasing the efficiency of using flexible manufacture systems (FMS) by increasing the load factor. Unlike the well-known multi-agent approach to production management, we are investigating the addition of a metasystem level allowing flexible combination of the decentralized control method with centralization. The metasystem approach allows to reduce management to flexible switching of functioning technologies on the basis of the replacement rule, while describing FMS as a metasystem consisting of classification of the system analyst J. Klir from structured data systems. Production events are simulated in virtual space with the help of a multi-agent approach. At the same time, the number of requests from the waiting queue is chosen such that it becomes possible to optimize the loading of the FMS in the simplest case by the full-scan method, if the queue is not available, then the initiative of choice is provided to communications of agents-technologies and agents-equipments. Experimental studies were carried out on the FMS model including six pieces of equipment divided into three groups with a stream of six applications, each of which has a technological route of six operations each‥ The experimental results showed the consistency of the developed approach by increasing the load factor of the FMS.

Research on the Relationship between Projection Number and Image Noise Level in FBP Reconstruction

The number of projection affects the reconstruction quality in computed tomography system. Larger projection number will lead to better reconstruction quality. On the other hand, less projection number can reduce the radiation dose, save time and keep the patients comfortable. The optimal number of projection compromises both the mathematical accuracy and practical requirement. The purpose of this paper is to find the relationship between the projection number and the noise properties of reconstructed cross-section. It can provide references for researchers on CT application. A micro-CT system is utilized to validate the relationship between projection number and reconstruction quality in fan beam geometry. Full-scan and short-scan method are applied to reconstruct the specimen. Compared with full-scan method, short-scan can reduce radiation dose with the same step angle, and it can achieve better results with the same projection number when the sample data is sufficient.

Simultaneous analysis of endosulfan, chlorpyrifos, and their metabolites in natural soil and water samples using gas chromatography-tandem mass spectrometry

Analysis of endosulfan, chlorpyrifos, and their nonpolar metabolites in extracts from environmental aqueous and soil samples was performed using a gas chromatography-tandem mass spectrometry (GC-MS/MS) technique. Full-scan GC-MS analysis showed poor sensitivity for some of the metabolites (endodiol and endosulfan ether). A multisegment MS/MS method was developed and MS/MS parameter isolation time, excitation time, excitation voltage, and maximum excitation energy were optimized for chosen precursor ions to enhance selectivity and sensitivity of the analysis. The use of MS/MS with optimized parameters quantified analytes with significantly higher accuracy, and detection limits were lowered to ~1/6th compared with the full-scan method. Co-eluting compounds, chlorpyrifos and chlorpyrifos oxon, were also analyzed successfully in the MS/MS mode by choosing exclusive precursor ions. Analysis of soil and water phase samples from contaminated soil slurry bioreactors showed that the MS/MS method could provide more reliable estimates of these pesticide and metabolites (especially those present in low concentrations) by annulling interferences from soil organic matter.

Analysis of acylcarnitine profiles in umbilical cord blood and during the early neonatal period by electrospray ionization tandem mass spectrometry

Acylcarnitine profiling by electrospray ionization tandem mass spectrometry (ESI-MS/MS) is a potent tool for the diagnosis and screening of fatty acid oxidation and organic acid disorders. Few studies have analyzed free carnitine and acylcarnitines in dried blood spots (DBS) of umbilical cord blood (CB) and the postnatal changes in the concentrations of these analytes. We have investigated these metabolites in healthy exclusively breastfed neonates and examined possible effects of birth weight and gestational age. DBS of CB were collected from 162 adequate for gestational age neonates. Paired DBS of heel-prick blood were collected 4-8 days after birth from 106 of these neonates, the majority exclusively breastfed. Methanol extracts of DBS with deuterium-labeled internal standards were derivatized before analysis by ESI-MS/MS. Most of the analytes were measured using a full-scan method. The levels of the major long-chain acylcarnitines, palmitoylcarnitine, stearoylcarnitine, and oleoylcarnitine, increased by 27, 12, and 109%, respectively, in the first week of life. Free carnitine and acetylcarnitine had a modest increase: 8 and 11%, respectively. Propionylcarnitine presented a different behavior, decreasing 9% during the period. The correlations between birth weight or gestational age and the concentrations of the analytes in DBS were weak (r ≤ 0.20) or nonsignificant. Adaptation to breast milk as the sole source of nutrients can explain the increase of these metabolites along the early neonatal period. Acylcarnitine profiling in CB should have a role in the early detection of metabolic disorders in high-risk neonates.

Evaluation of World Anti-Doping Agency criteria for anabolic agent analysis by using comprehensive two-dimensional gas chromatography–mass spectrometry

This work presents the validation study of the comprehensive two-dimensional gas chromatography (GC x GC)-time-of-flight mass spectrometry method performance in the analysis of the key World Anti-Doping Agency (WADA) anabolic agents in doping control. The relative abundance ratio, retention time, identification and other method performance criteria have been tested in the GC x GC format to confirm that they comply with those set by WADA. Furthermore, tens of other components were identified with an average similarity of >920 (on the 0-999 scale), including 10 other endogenous sterols, and full mass spectra of 5,000+ compounds were retained. The testosterone/epitestosterone ratio was obtained from the same run. A new dimension in doping analysis has been implemented by addressing separation improvement. Instead of increasing the method sensitivity, which is accompanied by making the detector increasingly "blind" to the matrix (as represented by selected ion monitoring mode, high-resolution mass spectrometry (MS) and tandem MS), the method capabilities have been improved by adding a new "separation" dimension while retaining full mass spectral scan information. Apart from the requirement for the mass spectral domain that a minimum of three diagnostic ions with relative abundance of 5% or higher in the MS spectra, all other WADA criteria are satisfied by GC x GC operation. The minimum of three diagnostic ions arises from the need to add some degree of specificity to the acquired mass spectrometry data; however, under the proposed full MS scan method, the high MS similarity to the reference compounds offers more than the required three diagnostic ions for an unambiguous identification. This should be viewed as an extension of the present criteria to a full-scan MS method.

Improved “General Unknown” Drug Screening Using GCxGCqMS

Drug screening in the clinical setting is very often started or even solely performed with a limited selection of enzyme immunoassays in urine samples. As a general rule positive results must be confirmed by more specific and sensitive methods like GC/MS or LC/MS(-MS). GC/MS full scan mode giving the highest level of specificity often faces the problem of co-elution which esp. at high concentrations cannot be circumvented even with modern deconvolution software in many cases. However, broad, undirected “general unknown” screening for drugs of abuse not covered by the EIA/GC/MS-SIM combinations is of increasing importance. In the present study we therefore investigated if the common drawbacks encountered in a standard GC/MS full-scan method could be improved by increased chromatographic resolution by means of comprehensive GCxqGCMS in full-scan mode [1]. To perform comprehensive GCxGC measurements a two stage loop modulator (ZOEX cooperation USA) was used. By use of a modulation frequency of 6 seconds together with the selected GC parameters results in 3 modulated peaks per compound. The results out of the comprehensive GCxGCqMS were compared with the one dimensional data set.

A Nonscan Design-for-Testability Method for Register-Transfer-Level Circuits to Guarantee Linear-Depth Time Expansion Models

This paper presents a nonscan design-for-testability (DFT) method for register-transfer-level (RTL) circuits. We first introduce the notation to analyze the test generation complexity, as well as two classes of sequential circuits, namely: 1) the combinationally testable class and 2) the acyclically testable class. Then, we introduce a new class of linear-depth time-bounded circuits as one of the acyclically testable classes. The linear-depth time-bounded testability guarantees that the number of time frames required for any testable fault is bounded by a linear function of the number of flip-flops in the circuit during the test generation process. As one of the linear-depth time-bounded classes, we introduce a new class of RTL circuits, called the cycle-unrollable RTL circuits, which is shown to be linear depth time bounded. We propose a DFT method to make RTL circuits cycle unrollable and a test generation method for cycle-unrollable RTL circuits. Experimental results show that we can drastically reduce hardware overhead and test application time compared to the full-scan method and the method proposed by Ohtake Moreover, our proposed method can achieve 100% fault efficiency for gate-level single stuck-at faults in practical test generation time and allow at-speed testing.

Development and comparison of methods using MS scan and selective ion monitoring modes for a wide range of airborne VOCs

Adsorbent sampling with analysis by thermal desorption, gas chromatography and mass spectrometry (TD/GC/MS) offers many advantages for volatile organic compounds (VOCs) and thus is increasingly used in many applications. For environmental samples and other complex mixtures, the MS detector typically is operated in the scan mode to aid identification of co-eluting compounds. However, scan mode does not achieve the optimal sensitivity, thus compounds occurring at low concentrations may not be detected. This paper develops and evaluates the application of a more sensitive TD/GC/MS method using selective ion monitoring (SIM) that is applicable to VOC mixtures found in ambient and indoor air. Based on toxicity and prevalence, 94 VOCs (including terpenes, aromatic, halogenated and aliphatic compounds) were selected as target compounds. Two analytical methods were developed: a conventional full scan method for ions from 29 to 270 m/z; and a SIM method using 16 time windows and different ions selected for the compounds in each window. Both methods used the same Tenax GR adsorbent sampling tubes, TD and GC parameters, and target and qualifier ions. Laboratory tests determined calibrations, method detection limits (MDLs), precisions, recoveries and storage stability. Field tests compared scan and SIM mode analyses for duplicate samples of indoor air in 51 houses and outdoor air at 41 sites. Statistical analyses included the development of error/precision models. The laboratory tests showed that most compounds demonstrated excellent precision (<10% for concentrations exceeding approximately 0.5 microg m(-3)), good linearity, near identical calibrations for scan and SIM modes, a wide dynamic range (up to 1500 microg m(-3)), and negligible storage losses after 1 month (7 compounds showed moderate losses). SIM mode MDLs ranged from 0.004 to 0.27 microg m(-3), representing a modest (1.1 to 22-fold) improvement compared to scan mode. However, in field tests the SIM method detected significantly more compounds (e.g., styrene and chloroform). Error models fit most compounds and allow quantification of errors at selected percentiles. Overall, while the new SIM method is somewhat time-consuming to develop, it offers greater sensitivity and maintains the high selectivity of traditional scan methods.