Secondary Standards Research Articles

Awareness level of school students in age group of 14-18 years about HIV & AIDS in a rural area of Jammu (J&K)

HIV infection is known to have established in India since year 1986 and three decades are over since then. A lot of activities have been since then going on by the government of India sponsored NACP under the aegis of NACO. The endemicity of this infection in populations is known to be inversely proportional to the level of awareness about HIV/AIDS. As per the data available, there are variations in level of awareness about the HIV/AIDS and it’s prevention among the general populations as well as the at risk populations. So it is always prudent to assess the level of awareness among the general population. For this reason survey of awareness level among the high school students can give a reliable indication as they represent the level of awareness of their families. Hence a study was conducted among the adolescent students in age group of 14-19 years ie. Class 9-12 years. Study Design: Cross sectional study. Study Subjects: adolescent students in age group of 14-19 years ie. Class 9-12 years. Study Period: Dec 2015 Materials and Methods: The study was conducted in village Maralian of Block RS Pura (rural field practice area of Department of Community medicine, GMC Jammu). The schools chosen were High and Higher secondary standards where the students of age group >14 years could be contacted. Study Instrument: A pre tested schedule containing (47) questions related to Knowledge, attitudes and practices of adolescents about modes of transmission and prevention of HIV infection, attitudes and beliefs about it and their related practices was used to interview. It was seen that the students in age group of 14-18 years were much aware about the HIV/AIDS, it’s causes, routes of transmission, risk factors, preventive measures and facilities for diagnosis and drugs. Students of this age group can be taken as proxy to the families they belong to and hence the general population of the area under study. But still, a large proportion is having wrong concepts or no ideas a

Electron spin relaxation of P1 centers in synthetic diamonds with potential as B1 standards for DNP enhanced NMR

The microwave magnetic field, B1, in the non-resonant structures typically used for DNP-enhanced NMR is relatively small, so calibration via continuous wave (CW) power saturation requires a sample with longer spin lattice relaxation times than the samples used as CW standards in X-band cavities. HPHT diamonds have strong, easily observed EPR signals from P1 centers (nitrogen defects), and are indefinitely stable. This makes HPHT diamonds attractive as secondary standards for calibration of electron B1 field strength in a variety of experimental arrangements. The concentrations of P1 centers is also typically in the 30–200 ppm range, or equivalently 10–60 mM, and therefore the EPR relaxation observed is relevant to DNP enhanced NMR employing free radical polarizing agents at similar concentrations. Pulsed and CW saturation relaxation measurements T1 and T2 are compared at X-band. Under CW conditions the relevant T1T2 product of time constants in our samples at room temperature is found to be dominated by electron–electron spin diffusion, and the product is large enough that saturation will be possible with the B1 of typical DNP systems. The similarity of T1 and T2 values obtained by pulse measurements at X-band and Q-band suggests that the X-band results can be extrapolated to the higher EPR frequencies used for DNP experiments. The electron spin dynamics observed here in HPHT diamond samples identify them as useful model systems to better delineate the interplay of electron spin relaxation, magic angle spinning, and inhomogeneous microwave irradiation as they affect DNP enhancement.

Anaerobic wastewater treatment and reuse enabled by thermophilic bioprocessing integrated with a bioelectrochemical/ultrafiltration module

The current study aimed to develop an anaerobic wastewater treatment and reuse module enabled by thermophilic bioprocessing, a microbial fuel cell (MFC) and ultrafiltration (UF) treatment. A previously unexplored consortium based on Thermoanaerobacterium thermosaccharolyticum and Arcobacter sp. was used to remove ~73% of chemical oxygen demand (COD) from wastewater under anaerobic conditions (CODi = 200 mg/L). The subsequent MFC and UF treatment removed the COD remnants to meet the secondary treatment standards and reuse criteria. The energy efficiency of polyethersulfone UF membranes was improved by modifying their surfaces with coatings based on self-polymerized dopamine, mixtures of dopamine and poly(2-dimethylamino) ethyl methacrylate methyl, and dopamine analog norepinephrine. The resulting hydrophilic, anti-fouling layers were found to reduce interactions between rejected species and the membrane surface. Finally, this study presents a comparative treatment performance and energy efficiency of the wastewater treatment and reuse modules arranged in six different configurations.

Absolute radiometric calibration of a VUV spectrometer in the wavelength range 46–300 nm

Vacuum ultraviolet (VUV) radiation corresponds to photon energies exceeding 6.2 eV and provides access to atomic and molecular resonant transitions in various plasmas. Determining population densities of electronic levels directly connected to the ground state requires an absolute intensity calibration of the VUV spectrometer. For this purpose, synchrotron radiation from electron storage rings is the typical primary standard source associated with transport effort and operating costs. Alternatively, a complex procedure using several secondary standards and discharges directly at the setup in use can be applied. In this work, an absolute intensity calibration avoiding synchrotron radiation to cover the wavelength range 46–300 nm accessible with two detectors—a photomultiplier tube and a channel electron multiplier—is presented. A combination of different standard sources—two deuterium arc lamps, branching-ratios of a nitrogen plasma and a high current hollow cathode—is applied for the relative calibration. The absolute calibration is based on simultaneous measurements of atomic lines in a low pressure helium discharge with the VUV spectrometer and an absolutely calibrated optical emission spectrometer. Special focus is laid on the uncertainties of the relative and absolute calibration depending on the wavelength range. The applicability of the intensity calibration is demonstrated at a hydrogen plasma in the wavelength range 80–300 nm. Using the emissivity of the Lyman series, population densities of the first six excited atomic states are calculated considering opacity effects. The excellent agreement with results from the Balmer series by optical emission spectroscopy manifests the high validity of the performed absolute intensity calibration.

A method for assessing the uncertainty of a secondary dynamic pressure standard using shock tube

Pressures are often measured in fast transient regimes, even if the transducers are not calibrated in dynamic regimes. If the solutions proposed for primary calibration of the dynamic response of pressure sensors must be fully recognised, secondary methods are also needed to disseminate the standard to final users. A method for assessing measurement uncertainty, carried out by comparison with a reference transducer, traceable to primary standard, is proposed here. A typical application is gas pressure measurement. This paper follows and supplements the work done on the Mach number method in 2018. For this work the reference transducer is calibrated by the ‘collective standard method’ currently used in the ‘Laboratoire de Métrologie Dynamique’( LNE/ENSAM). This primary standard uses steps of pressure as inputs for dynamic pressure calibration that are generated by shock tubes (STs) and fast-opening devices (FODs). The uncertainty on dynamic sensitivity is evaluated from the quasi-static to the low, medium and high-frequency range (up to 10 kHz) using bandwidth comparisons. To calibrate a secondary standard transducer in gas, the method also requires one or two step generators: an ST for high-frequency range calibration and a FOD for the low-frequency range. Concerning the main results of this paper, the transducer to be calibrated and the reference transducer are placed symmetrically on the endplate of an ST. The amplitude of the pressure step generated by the tube is used to excite the transducers. Finally, the uncertainty on the sensitivity in dynamic conditions is determined by comparison with a model expected to be exhaustive. The results are provided as an uncertainty budget assigned frequency by frequency. The question asked in this work concerns the measurand used in secondary calibration: can a pressure step generated by a non-ideal ST be used in the process of calibration by comparison, i.e. for a secondary dynamic calibration? A method is proposed. Since the secondary method is derived directly from the primary one, this paper recaps the primary dynamic calibration method in gas and the budget of the associated uncertainty. Then the paper presents a secondary method and options to overcome the principal default identified in the ST frequency range, namelythe non-uniform pressure fields existing in the tube.

DEVELOPMENT OF 222RN IN AIR SECONDARY STANDARD IN THE SLOVAK REPUBLIC.

Slovak Institute of Metrology received in 2016 funding for realisation of a set up of a radon chamber with AlphaGUARD as a secondary standard of 222Rn in air as one part of the project. This secondary standard will serve to provide the traceability for laboratories that deal with 222Rn measurements in environmental samples. This project is a response to the European Union legislation and provides metrological support for the development and implementation of the national radon action plan, which the member states of the European Union are committed to fulfil in accordance with Council Directive 2013/59/Euratom. During development of the radon chamber, the determination of its basic technical parameters, such as the exact determination of the container volume and the area of the inner walls of the radon chamber, many tightness tests of the chamber, the definition of homogeneous radon atmosphere parameters and bilateral comparisons, were realised.

A strontium optical lattice clock with 1 × 10−17 uncertainty and measurement of its absolute frequency

We present a measurement of the absolute frequency of the 5 s2 1S0 to 5s5p 3P0 transition in 87Sr which is a secondary representation of the SI second. We describe the optical lattice clock apparatus used for the measurement, and we focus in detail on how its systematic frequency shifts are evaluated with a total fractional uncertainty of 1 × 10−17. Traceability to the International System of Units is provided via comparison to International Atomic Time (TAI). Gathering data over 5- and 15-day periods, with the lattice clock operating on average 74% of the time, we measure the frequency of the transition to be 429 228 004 229 873.1 (5) Hz, which corresponds to a fractional uncertainty of 1 × 10−15. We describe in detail how this uncertainty arises from the intermediate steps linking the optical frequency standard, through our local time scale UTC(NPL), to an ensemble of primary and secondary frequency standards which steer TAI. The calculated absolute frequency of the transition is in good agreement with recent measurements carried out in other laboratories around the world.

RADIOCARBON IN DISSOLVED ORGANIC CARBON BY UV OXIDATION: PROCEDURES AND BLANK CHARACTERIZATION AT NOSAMS

ABSTRACTThis study describes a procedural blank assessment of the ultraviolet photochemical oxidation (UV oxidation) method that is used to measure carbon isotopes of dissolved organic carbon (DOC) at the National Ocean Sciences Accelerator Mass Spectrometry Facility (NOSAMS). A retrospective compilation of Fm and δ13C results for secondary standards (OX-II, glycine) between 2009 and 2018 indicated that a revised blank correction was required to bring results in line with accepted values. The application of a best-fit mass-balance correction yielded a procedural blank of 22.0 ± 6.0 µg C with Fm of 0.30 ± 0.20 and δ13C of –32.0 ± 3.0‰ for this period, which was notably higher and more variable than previously reported. Changes to the procedure, specifically elimination of higher organic carbon reagents and improved sample and reactor handling, reduced the blank to 11.0 ± 2.75 µg C, with Fm of 0.14 ± 0.10 and δ13C of –31.0 ± 5.5‰. A thorough determination of the entire sample processing blank is required to ensure accurate isotopic compositions of seawater DOC using the UV oxidation method. Additional efforts are needed to further reduce the procedural blank so that smaller DOC samples can be analyzed, and to increase sample throughput.

Heavy Metal Analysis of Three Urban Rivers in Enugu, Nigeria

The multiple industrial, domestic, agricultural, medical, and technological applications of heavy metals have led to their wide distribution in the environment, raising concerns over their potential effects on human health and the environment. This work focused on the determination of manganese, chromium, zinc, cadmium, arsenic, mercury, iron and lead concentrations in Abakpa, Iva Valley, and Transekulu Rivers which are close to residential areas in Enugu, Nigeria. The analysis were carried out using atomic absorption spectrometer (AAS). All the heavy metals tested in the three studied locations exceeded the different drinking water limits except zinc which was below secondary drinking water standard of 5.0 mg/l. The levels of mercury and zinc were significantly higher in Abakpa River (0.57 ± 0.112 and 0.881 ± 0.0015 mgl-1 respectively). Iva valley showed higher levels of manganese, chromium, iron and arsenic compared to other rivers studied. The presence in these metals in the water sources are a great risk to humans and the environment.

Can we identify allergic rhinitis from administrative data: A validation study

Important insights on, for example, prevalence, disease progression, and treatment of allergic rhinitis can be obtained from large-scale database studies if researchers are able to identify allergic individuals. We aimed to assess the validity of 13 different algorithms based on Danish nationwide prescription and/or hospital data to identify adults with allergic rhinitis. Our primary gold standard of allergic rhinitis was a positive serum specific IgE (≥0.35) and self-reported nasal symptoms retrieved from two general health examination studies conducted in Danish adults (18-69 years) during 2006 to 2008 (n = 3416) and 2012 to 2015 (n = 7237). The secondary gold standard of allergic rhinitis was self-reported physician diagnosis. We calculated sensitivity, specificity, positive predictive value (PPV), negative predictive value, and corresponding 95% confidence intervals (95% CI) for each register-based algorithm in the two time periods. Sensitivity (≤0.40) was low for all algorithms irrespective of definition of allergic rhinitis (gold standard) or time period. The highest PPVs were obtained for algorithms requiring both antihistamines and intranasal corticosteroids; yielding a PPV of 0.69 (0.62-0.75) and a corresponding sensitivity of 0.10 (0.09-0.12) for the primary gold standard of allergic rhinitis in 2012 to 2015. Algorithms based on both antihistamines and intranasal corticosteroids yielded the highest PPVs. However, the PPVs were still moderate and came at the expense of low sensitivity when applying the strict primary gold standard (sIgE and nasal symptom).

Addressing the burden of cervical cancer through IAEA global brachytherapy initiatives

PurposeBrachytherapy (BT) is an essential component of definitive therapy for locally advanced cervical cancer. Despite the advantages of the dose distribution with BT in cervical cancer, there is paucity of specific skills required for good-quality BT applications. Furthermore, replacing BT with other modern external beam techniques as a boost can lead to suboptimal results in cervix cancer. Methods and MaterialsReview of available IAEA resources, research and cooperation programs available from the IAEA was completed. These opportunities can be used to address challenges in Brachytherapy.The International Atomic Energy Agency (IAEA) provides support for BT through various means that includes education and training, both long term, short term and continuing medical education of professionals, providing expert visits to support implementation, development of curricula for professionals, e-learning through the human health campus, contouring workshops, 2D to 3D BT training, and virtual tumor boards. In addition, the IAEA provides support for implementing quality assurance in radiotherapy to its member states and provides guidelines for comprehensive audits in radiation therapy (QUATRO), and produces safety standards and training in radiation safety. In addition, mapping BT resources, making the case for investment and support for setting up BT services and radiotherapy centers are also available. The IAEA Dosimetry Laboratory provides calibration services to Secondary Standards Dosimetry Laboratories for well chambers used to confirm the reference air kerma rate of Co60 and Ir192 high-dose-rate BT sources, as well as for Cs137 low-dose-rate sources.Furthermore, the IAEA supports research and development in radiotherapy (and BT) through coordinated research activities that include controlled randomized clinical trials, Patterns of Care studies among others. Partnerships with professional organizations and funding bodies, as well as through the United Nations Joint Global Programme on Cervical Cancer Prevention and Control support radiotherapy activities, including BT in countries worldwide. ConclusionThe IAEA supports brachytherapy implementation, training and research and provides resources to professionals in the area.

A Method of Transferring the Unit of Power of High-Intensity Laser Radiation

A method is proposed for transferring the unit of mean power of laser radiation by means of measuring high-intensity power (kilowatts), with the possibility of constant monitoring of the transfer process. A measuring optical power divider for laser radiation has been developed, structurally built in the form of a wedge and permitting, according to the relatively small power of the radiation reflected from the lighted surface of the forward face of the wedge, to determine the radiant power of the beam incident upon the measuring instrument to be calibrated. The proposed method is based on applying the developed divisor in the reference installation and provides for the implementation of three modes of operation of the installation: the mode for determination of the coefficient of equivalence; the mode for determination of the division ratio of the optical splitter; the mode of transfer of the power unit by measurement facilities; and determination of the control parameter of the optical splitter. The transfer process is monitored by measuring the radiant power reflected from the back edge of the wedge, and determining the control parameter. The conditions in which it is advisable to use the proposed mode of determining the division ratio of the optical splitter are given. A special feature of the method under study is the possibility of timely monitoring of the division ratio of the optical splitter, making it possible to estimate in real time the reliability of the process of calibration of measurement instruments. A formula was derived for the metrological traceability of the power measurement results to GET 28-2016. The basic error component errors of the determination of the radiant power arriving at input of the measurement facilities being calibrated are considered. The results of the experimental studies of this method make it possible to confirm that at 10.6 μm wavelength, the total measurement error of the power, expressed as the SD, does not exceed 2.0%. The method can be used in the corresponding secondary standards of the power unit that obtain a unit from the State Special Standard for Mean Power, GET 28-2016.

A COMPARATIVE STUDY ON THE PERFORMANCE OF STUDENTS OF PRIVATE SCHOOLS, GOVERNMENT SCHOOLS SITUATED IN URBAN & RURAL AREAS OF HARYANA IN THE SECONDARY EXAMINATIONS CONDUCTED BY THE BOARD OF SCHOOL EDUCATION HARYANA IN 2020.

The capability or calibre cannot be judged based on Results, as it depends on the student to student & also the examination is testing of knowledge of a student, for the whole year in two or three hours. In July 2020 the exam result of the secondary standard was declared by the Board of School Education Haryana, Bhiwani and there is a discussion about topper & the schools in which these toppers were studying & strategy of these toppers regarding exam preparation, their interviews & photos were published in the Newspapers, why not? It must be but in this spark light, there is some darkness behind this. Everyone is congratulating these students, as they are studied from the Private Schools of the Urban City areas of the Haryana, a few are from the most educated families, whose parents their selves are teachers or professors. Through this, we are ignoring a bitter truth of the poor students of the Government Schools, who despite lack of all the big & small facilities, as compare of these Private schools’ performed equal to these toppers. KEYWORDS: Testing of knowledge, Education in Private Schools, Toppers and Calibre.

ARTEMIS, THE 14C AMS FACILITY OF THE LMC14 NATIONAL LABORATORY: A STATUS REPORT ON QUALITY CONTROL AND MICROSAMPLE PROCEDURES

ABSTRACTQuality control procedures have been developed at the Laboratoire de Mesure du Carbone 14 (LMC14) national laboratory throughout the years of operation. Routine procedures are applied to sample preparation depending on their composition and their size. The tuning of the ARTEMIS AMS facility, hosted by the LMC14 laboratory, uses an accurate procedure. A batch of unknown samples is measured with accompanying samples (primary and secondary standards and blanks), which give a powerful set of data to control the quality of each measurement. A homemade database has been created to store the sample information and study the evolution of the accompanying samples. The LMC14 laboratory participated in the Sixth International Radiocarbon Intercomparison, SIRI. The results are presented here, with statistical tests to assess the quality of the preparations and measurements done at the LMC14 national laboratory. To obtain a reliable radiocarbon (14C) age by AMS, 1 mg of sample is required in routine analysis. Recently, the LMC14 developed a new procedure dedicated to microsamples, allowing the size of samples to be reduced and contributing to opening 14C dating to materials that were previously unreachable. This new procedure has been successfully tested on valuable Cultural Heritage samples: lead white mural paintings.

Quantitative assessment of terminal ileum motility on MR enterography in Crohn disease: a feasibility study in children.

Investigate the relationship between quantified terminal ileal (TI) motility and histopathological activity grading, Crohn Disease MRI Index (CDMI) and faecal calprotectin. Retrospective review of children with Crohn disease or unclassified inflammatory bowel disease, who underwent MR enterography. Dynamic imaging for 25 patients (median age 12, range 5 to 16) was analysed with a validated motility algorithm. The TI motility score was derived. The primary reference standard was TI Endoscopic biopsy Assessment of Inflammatory Activity (eAIS) within 40days of the MR enterography. Secondary reference standards: (1) the Crohn Disease MRI Index (CDMI) and (2) faecal calprotectin levels. MR enterography median motility score was 0.17a.u. (IQR 0.12 to 0.25; range 0.05 to 0.55), and median CDMI was 3 (IQR 0 to 5.5). Forty-three percent of patients had active disease (eAIS > 0) with a median eAIS score of 0 (IQR 0 to 2; range 0 to 5). The correlation between eAIS and motility was r = - 0.58 (p = 0.004, N = 23). Between CDMI and motility, r = - 0.42 (p = 0.037, N = 25). Motility score was lower in active disease (median 0.12 vs 0.21, p = 0.020) while CDMI was higher (median 5 vs 1, p = 0.04). In a subset of 12 patients with faecal calprotectin within 3months of MR enterography, correlation with motility was r = - 0.27 (p = 0.4). Quantified terminal ileum motility decreases with increasing histopathological abnormality in children with Crohn disease, reproducing findings in adults. TI motility showed a negative correlation with an MRI activity score but not with faecal calprotectin levels. • It is feasible to perform MRI quantified bowel motility assessment in children using free-breathing techniques. • Bowel motility in children with Crohn disease decreases as the extent of intestinal inflammation increases. • Quantified intestinal motility may be a candidate biomarker for treatment efficacy in children with Crohn disease.

Identification and quantification of contributions to karst groundwater using a triple stable isotope labeling and mass balance model

Although karst groundwater systems provide critical ecosystem services in many regions worldwide, anthropogenic contamination has seriously degraded groundwater quality. Properly elucidating geochemical processes, quantifying contributions of natural and anthropogenic end members, and then protecting karst aquifer systems remain challenging from scientific and engineering aspects. To identify the hydrochemical processes and quantifying contributions of end members (especially, contamination end members), 49 samples were collected from cave waters (CW), artesian springs (AS), and gravity springs (GS) in a karst watershed in Guiyang, China. With increased anthropogenic contamination, the CW, AS, and GS characterized by a Ca–Mg–SO42--HCO3- composition often had pH and SO42− concentrations exceeding USEPA secondary drinking water standards. That is attributed to the influence of water-rock interaction, rainfall, and anthropogenic sources (mainly, sewage and fertilizers), in agreement with the compositions of δ34SSO4, δ18OSO4, and 87Sr/86Sr as well as the results of principal component analysis and correlation coefficients. Based on an end-member mixing model, contributions of rainfall and anthropogenic sources were 47% and 33% of GS, 52% and 41% of CW, and 58% and 35% of AS, respectively. It suggests that the karst groundwater quality is predominantly controlled by rainfall and anthropogenic sources (especially, land use). Results may be applied to properly evaluate the impacts of natural and anthropogenic sources on karst aquifers, coupled with actions to efficiently control potential contamination end members.

Direct comparisons of European primary and secondary frequency standards via satellite techniques

We carried out a 26-day comparison of five simultaneously operated optical clocks and six atomic fountain clocks located at INRIM, LNE-SYRTE, NPL and PTB by using two satellite-based frequency comparison techniques: broadband Two-Way Satellite Time and Frequency Transfer (TWSTFT) and Global Positioning System Precise Point Positioning (GPS PPP). With an enhanced statistical analysis procedure taking into account correlations and gaps in the measurement data, combined overall uncertainties in the range of 1.8 × 10−16 to 3.5 × 10−16 for the optical clock comparisons were found. The comparison of the fountain clocks yields results with a maximum relative frequency difference of 6.9 × 10−16, and combined overall uncertainties in the range of 4.8 × 10−16 to 7.7 × 10−16.

Research on the irradiance calibration of a VUV dual-grating spectrometer based on synchrotron radiation

A high accuracy instrument calibration is the guarantee of obtaining high precision atmospheric inversion data from a wavelength-dispersive space remote sensing instrument in the orbit. To improve the relative calibration uncertainty of a dual-grating spectrometer in the vacuum-ultraviolet (VUV) band, conventional secondary standard light sources, such as deuterium lamps, used in laboratory calibrating stations are not suited to meet high precision. In this paper we present the calibration of the space instrument based on the Metrology Light Source (MLS) of the Physikalisch-Technische Bundesanstalt (PTB) operated as a primary synchrotron radiation (SR) source with calculable spectral radiant intensity to overcome the limit imposed by secondary transfer standards. For taking into account the difference between the highly linearly polarized SR source and the un-polarized solar radiation, which will be observed by the dual-grating spectrometer in orbit, the calibration was performed at two orientations of the instrument, which are perpendicular to each other with respect to the incident SR. The factors contributing to the uncertainty budget were analyzed. It could be shown that a total relative uncertainty of 2.52% can be achieved, which has greatly improved the calibrating accuracy compared with that obtainable with the conventional standard light source calibrating stations in the VUV spectral range.

Persistent Challenges of Interassay Variability in Transplant Viral Load Testing.

While quantification of viruses that cause important infections in transplant recipients has been the standard of care for years, important challenges related to standardization remain. The issues are wide ranging, and until they are adequately addressed, the full impact of viral load testing regarding clinical management decisions will not be realized. This review focuses on a broad array of problems, including the lack of available FDA-approved/cleared tests, limited uptake of international standards, accurate quantification of secondary standards, specific assay characteristics, and commutability. Though some of these topics are nuanced, taken together they greatly influence the clinical utility of testing. For example, it has not been possible to define thresholds that predict the risk of developing disease and determine significant changes in serial viral load values for a given patient. Moreover, the utility of international guidelines may be limited due to the lack of a standardized assay. By summarizing the issues, the hope is that commercial companies, regulatory agencies, and professional societies can come together to advance the field and solve these problems.

Purity estimation of seized stimulant-type new psychoactive substances without reference standards by nitrogen chemiluminescence detection combined with GC-APCI-QTOFMS

Purity assessment of seized material containing new psychoactive substances (NPS) is complicated without appropriate primary reference standards. Here we present a method for fast quantitative estimation of stimulant-type NPS with use of secondary reference standards, based on gas chromatography nitrogen chemiluminescence detection coupled with atmospheric pressure chemical ionization quadrupole time-of-flight mass spectrometry (GC-NCD-APCI-QTOFMS). Quantification was based on the detector’s N-equimolar response to nitrogen and using two external nitrogen-containing calibrators, MDMA for prim- and sec-amines and α-PVP for tert-amines. Sample preparation involved dissolving the seized powdery material in an organic solvent mixture followed by acylation with N-methyl-bis-trifluoroacetamide (MBTFA). The method’s between-day accuracy and precision over a five-day period was measured for twenty-eight stimulants: the grand mean equimolarity was 91.9% (CV 5.5%), as compared with primary reference standards. The GC-NCD-APCI-QTOFMS method was applied to the purity estimation of forty-two seized powder samples previously found to contain stimulant-type NPS by appropriate methods. The quantitative results were compared to those obtained by an established method relying on liquid chromatography chemiluminescence detection (LC-CLND), the latter using caffeine as an external calibrator. The mean difference of purity values between the methods was 8.1% (range 0.4–26.7%). The presented method might find use as a tool for instant purity assessment in forensic laboratories.