Mean Relative Standard Deviation Research Articles

Least-squares support vector machine and its application in the simultaneous quantitative spectrophotometric determination of pharmaceutical ternary mixture

This paper proposes the least-squares support vector machine (LS-SVM) as an intelligent method applied on absorption spectra for the simultaneous determination of paracetamol (PCT), caffeine (CAF) and ibuprofen (IB) in Novafen. The signal to noise ratio (S/N) increased. Also, In the LS - SVM model, Kernel parameter (σ2) and capacity factor (C) were optimized. Excellent prediction was shown using LS-SVM, with lower root mean square error (RMSE) and relative standard deviation (RSD). In addition, Regression coefficient (R2), correlation coefficient (r) and mean recovery (%) of this method obtained for PCT, CAF and IB. LS- SVM / spectrophotometry method is reliable for simultaneous quantitative analysis of components in commercial samples. The results obtained from analyzing the real sample by the proposed method compared to the high- performance liquid chromatography (HPLC) as a reference method. One-way analysis of variance (ANOVA) test at 95% confidence level used and results showed that there was no significant difference between suggested and reference methods.

Dissipation behaviour and dietary risk assessment of boscalid, triflumizole and its metabolite (FM-6-1) in open-field cucumber based on QuEChERS using HPLC-MS/MS technique.

To resist plant diseases, boscalid and triflumizole have been applied to cucumbers frequently. However, the residue and dietary risk assessment of these fungicides in cucumber should be given attention for food safety. An effective and highly sensitive method based on the liquid chromatography-tandem mass spectrometry technique for simultaneous multidetermination of boscalid, triflumizole and its metabolite (FM-6-1) in a cucumber ecosystem was established and validated. Field experiments were conducted in three different locations, where boscalid and triflumizole (35% suspension concentration) were applied at 253 g of active ingredient (a.i.) per hectare (the recommended high dosage) and 379.5 g a.i. ha-1 (1.5 times the recommended high dosage) in each location. The limits of quantification and the limits of detection of the proposed method ranged from 0.01 to 0.05 mg kg-1 and 3.9×10-5 to 7.5×10-4 mg L-1 respectively. The mean recoveries and relative standard deviations of these compounds were 80-105% and 1.0-6.1% respectively. The dissipation dynamics of compounds followed pseudo-first-order kinetic models remarkably, with a half-value period of 2.3-40.8 days. The residues of boscalid and triflumizole in cucumber at harvest were below 0.66 mg kg-1 and 0.07 mg kg-1 respectively. The results of the dietary risk assessments have shown a low dietary risk of compounds in cucumber with hazard ratios <1 and hazard index <1. These results from the experiments are the most important for putting a guide on reasonable usage of these fungicides under the open-field conditions in China. © 2018 Society of Chemical Industry.

Stochastic analysis of pull-in instability of geometrically nonlinear size-dependent FGM micro beams with random material properties

Analyzing effects of uncertainty in material properties and geometric parameters in the manufacturing of MEMS is crucial for designing accurate tools with suitable performance. Pull-in voltage as a nonlinear characteristic of MEMS is affected significantly by these uncertainties. This paper investigates the randomness of the pull-in voltage of functionally graded material (FGM) micro-beams due to randomness in constituent material properties by presenting a reliable model for capturing uncertainties and effective procedures for solving stochastic nonlinear equations. The clamped-clamped FGM micro-beams, whose material properties vary smoothly based on the power law distribution in thickness, are under the influence of electrostatic and intermolecular forces. The governing equations are derived based on Euler-Bernoulli beam theory and modified couple stress theory considering nonlinear von Karman strain. The differential quadrature method (DQM) is used to solve the set of nonlinear ordinary differential equations. Monte Carlo simulation (MCS) is used to obtain the second order statistics (mean value and standard deviation) of the pull-in voltage. First order perturbation technique (FOPT) is also presented to investigate the randomness of the pull-in voltage, and the results are compared with those of independent MCS. It is shown that FOPT is fast and can predict mean value as accurate as MCS. The effects of volume fraction, the material length scale parameter, geometric parameters and the Casimir on the mean value and relative standard deviation (RSD) of the pull-in voltage are studied. Also, the effect of individual constituent materials and volume fraction index are investigated while the relative standard deviation changes.

Spectrophotometric determination of trace-level bromate in drinking water after post-column reaction with pararosaniline based on multi-walled carbon nanotubes

ABSTRACTA simple and sensitive spectrophotometric method is described for low level determinationof bromate in drinking water. This method is based on the reduction of bromate ions into bromine in the presence of pararosaniline by sodium metabisulphite to form a highly stable pink-red complex measured at 540 nm. Maximum colour formation was obtained at about 45 min. Multi-walled carbon nanotubes, a solid phase extraction sorbent, has been described for the removal of cationic interferences of major elements and heavy metals from water samples prior to conducting the assay. Bear’s law is obeyed in the range of 5–80 µg.L−1 with limit of detection of 0.44 µg.L−1 and correlation coefficient of 0.998 (n = 5). The mean relative standard deviation (RSD%) of the results within-day precision and accuracy were ≤1.2% which confirmed the reproducibility of the assay technique. The optimum assay conditions and their applicability to the determination of water samples are described. The method was successfully applied for the determination of bromate in water samples with satisfactory results and recommended to be applied in all desalination plant samples.

Characterization of a multilayer ionization chamber prototype for fast verification of relative depth ionization curves and spread-out-Bragg-peaks in light ion beam therapy.

To dosimetrically characterize a multilayer ionization chamber (MLIC) prototype for quality assurance (QA) of pristine integral ionization curves (ICs) and spread-out-Bragg-peaks (SOBPs) for scanning light ion beams. QUBE (De.Tec.Tor., Torino, Italy) is a modular detector designed for QA in particle therapy (PT). Its main module is a MLIC detector, able to evaluate particle beam relative depth ionization distributions at different beam energies and modulations. The charge collecting electrodes are made of aluminum, for a nominal water equivalent thickness (WET) of ~75mm. The detector prototype was calibrated by acquiring the signals in the initial plateau region of a pristine BP and in terms of WET. Successively, it was characterized in terms of repeatability response, linearity, short-term stability and dose rate dependence. Beam-induced measurements of activation in terms of ambient dose equivalent rate were also performed. To increase the detector coarse native spatial resolution (~2.3mm), several consecutive acquisitions with a set of certified 0.175-mm-thick PMMA sheets (Goodfellow, Cambridge Limited, UK), placed in front of the QUBE mylar entrance window, were performed. The ICs/SOBPs were achieved as the result of the sum of the set of measurements, made up of a one-by-one PMMA layer acquisition. The newly obtained detector spatial resolution allowed the experimental measurements to be properly comparable against the reference curves acquired in water with the PTW Peakfinder. Furthermore, QUBE detector was modeled in the FLUKA Monte Carlo (MC) code following the technical design details and ICs/SOBPs were calculated. Measurements showed a high repeatability: mean relative standard deviation within ±0.5% for all channels and both particle types. Moreover, the detector response was linear with dose (R2 >0.998) and independent on the dose rate. The mean deviation over the channel-by-channel readout respect to the reference beam flux (100%) was equal to 0.7% (1.9%) for the 50% (20%) beam flux level. The short-term stability of the gain calibration was very satisfying for both particle types: the channel mean relative standard deviation was within ±1% for all the acquisitions performed at different times. The ICs obtained with the MLIC QUBE at improved resolution satisfactorily matched both the MC simulations and the reference curves acquired with Peakfinder. Deviations from the reference values in terms of BP position, peak width and distal fall-off were submillimetric for both particle types in the whole investigated energy range. For modulated SOBPs, a submillimetric deviation was found when comparing both experimental MLIC QUBE data against the reference values and MC calculations. The relative dose deviations for the experimental MLIC QUBE acquisitions, with respect to Peakfinder data, ranged from ~1% to ~3.5%. Maximum value of 14.1μSv/h was measured in contact with QUBE entrance window soon after a long irradiation with carbon ions. MLIC QUBE appears to be a promising detector for accurately measuring pristine ICs and SOBPs. A simple procedure to improve the intrinsic spatial resolution of the detector is proposed. Being the detector very accurate, precise, fast responding, and easy to handle, it is therefore well suited for daily checks in PT.

Kinetic models of Fischer-Tropsch synthesis reaction over granule-type Pt-promoted Co/Al2O3 catalyst

Kinetic models of CO hydrogenation to paraffinic hydrocarbons through Fischer-Tropsch synthesis (FTS) reaction were studied by using Langmuir-Hinshelwood Hougen-Watson (LHHW) model of 16 different reaction steps with a pseudo steady-state assumption (PSSA) on the prototype Pt-promoted Co/Al2O3 catalyst having a granule size of ∼1 mm of spherical γ-Al2O3 support (surface area of 149m2/g). The derived kinetic models from ten sets of experimental data by altering the reaction conditions such as temperatures, pressures, space velocities and H2/CO molar ratios were found to be well fitted with reasonable kinetic parameters and small errors of conversion of CO and hydrocarbon distributions in terms of mean absolute relative residual (MARR) and relative standard deviation error (RSDE). The derived reaction rates and CO activation energy of -86 kJ/mol well correspond to the our previously reported results using power-type catalysts. Based on the LHHW model with PSSA, the possible chemical intermediates on the granule ball-type Co-Pt/Al2O3 surfaces were precisely considered to explain the typical adsorption, initiation, propagation and termination steps of FTS reaction as well as to derive elementary reaction rates with their kinetic parameters and hydrocarbon distributions. The derived kinetic models were further used to verify temperature-profiles in a pilot-scale fixed-bed tubular FTS reactor with a packing depth of 100 cm catalyst, and it confirmed that the temperature gradients were less than 10 °C in a length of reactor by effectively removing the generated heat by an exothermic FTS reaction.

DWT-based adaptive decomposition method of electrostatic signal for dilute phase gas-solid two-phase flow measuring

The inner flush-mounted electrostatic sensors are widely used for measuring gas-solid two-phase flow in many industries. The measured signal contains induced charge signal (ICS) and transferred charge signal (TCS). According to the band characteristics of the ICS, an adaptive decomposition method based on discrete wavelet transform (DWT) is proposed to extract ICS from measured signals of the sensors. In the measurement of the cross-correlation particle velocity, the mean cross-correlation coefficient between the extracted ICS from upstream and downstream electrodes is 0.74, increased from the previous coefficient 0.48 between the overall measured signals collected from the electrodes. This significant increase shows that the ICS better serves the measurement with higher accuracy. Meanwhile, the mean relative standard deviation (RSD) of the solid velocity is reduced from 3.35% to 2.69% after decomposition, which brings better stability. In addition, the root-mean-square (RMS) of the extracted TCS shows a trend of linear increase as the solid mass flow rate and superficial air velocity rise, indicating that TCS can also serve as an effective method to predict the solid mass flow rate as an alternative to ICS.

Determination of Prasugrel Hydrochloride in Bulk and Pharmaceutical Formulation Using New Ion Selective Electrodes

The construction and performance characteristics of Prasugrel hydrochloride (PRS) selective electrodes were developed. Electrodes were based on the incorporation of PRS with pairing agents, Ammonium Molybdate (MOL) and Nessler reagent (NES). The electrodes displayed a Nernstian response with a mean calibration graphs slopes of 59.21, 27.57 mv.decade-1 for the two electrodes respectively, over linear concentration range 10-2 –10-5 mol L-1 of the drug, with detection limits 0.063, 0.090 µM and quantification limits 0.27, 0.192 µM for electrode 1 and 2 respectively. The safe pH range of the proposed electrodes was (1-4). The influence of possible interfering species such as inorganic cations and pharmacologically related compounds was studied. The electrodes showed a fast response of (20 ± 2 sec, 17 ± 2 sec) for a period of 11 days, 9 days for electrode 1 and 2 respectively without significant change in electrode parameters. The methods are precise as shown by mean recoveries range of (97.7-102.5 %) – (97.3-101 %) with a mean relative standard deviation less than 3.14 and 4.46% for electrode 1 and 2 respectively. The results were compared to those obtained by a reference method. The proposed electrodes were used for the determination of PRS in pure form and pharmaceutical formulation.

Determination of clopidogrel bisulphate using drug selective membranes

Newly developed ion selective electrode has been developed for determination of Clopidogrelbisulphate(CLP) in pure form and pharmaceutical preparations. The selective electrode was constructed from Clopidogrel with pairing agent Nesslerreagentin presence of di-n-butyl phthalate (DBP) as the plasticizing solvent mediator. The electrode displayed a Nernstian response with a mean calibration graphs slopeof 28.37 mv.decade−1, over linear concentration range 10−2-10−5M of the drug, with detection limits 0.063 μMand quantification limits 0.191 μM. The electrode was effective at pH range between 1–3. The influence of possible interfering species such as inorganic cations and pharmacologically related compounds was studied. The electrode showed a fast response of (18±2 sec) for a period of 11 days, without significant change in electrode parameters. The method is precise as shown by mean recoveries range of (97.9–102.9%)with a mean relative standard deviation less than 2.80. The results were compared to those obtained by a reference method. The proposed electrode was used for the determination of CLP in pure form and pharmaceutical formulation.

An oligosorbent-based aptamer affinity column for selective extraction of aflatoxin B2 prior to HPLC with fluorometric detection.

The article describes an aptamer affinity column for selective solid-phase extraction of aflatoxin B2 (AFB2). Amino-modified aptamer against AFB2 was immobilized on CNBr-activated Sepharose through a covalent bond. The effects of oligosorbents based on 3'- or 5'-amino-modified sequences with a C6 or a C7 spacer arm were evaluated by UV spectroscopy at 260nm. The extraction recovery was evaluated by HPLC with fluorometric detection. The extraction of AFB2 was optimized. Under the optimum conditions, the aptamer affinity column has a linear response to AFB2 in the range of 0.5-80ng, with a capacity of 84.6ng. Control supports without immobilized aptamers and a nonspecific oligosorbent immobilized with a negative control oligonucleotide were studied in order to demonstrate selectivity. The method was tested with spiked peanut sample (0.5-50μg·kg-1 AFB2) and gave average recoveries of 80.9% and a mean relative standard deviation of 1.9%. The limit of detection is 25pg·mL-1. This is much lower than the maximum residue limits suggested by the European Union. The columns can be re-used up to five times without any loss of performance. The oligosorbent was also applied to clean-up of AFB2 from peanut sample extracts before HPLC analysis. Results were further confirmed by ultra-fast liquid chromatography with tandem mass spectrometry. Conceivably, the method may also be applied to other samples, such as food, agricultural products, and traditional Chinese medicines. Graphical abstract Schematic illustration of the fabrication procedures of aptamer affinity column, AAC (a), its principle of aptamer bound to aflatoxin B2 (b) and the obtained AAC

Impact of intratumoral heterogeneity of breast cancer tissue on quantitative metabolomics using high-resolution magic angle spinning 1 H NMR spectroscopy.

High-resolution magic angle spinning (HR MAS) nuclear magnetic resonance (NMR) spectroscopy is increasingly being used to study metabolite levels in human breast cancer tissue, assessing, for instance, correlations with prognostic factors, survival outcome or therapeutic response. However, the impact of intratumoral heterogeneity on metabolite levels in breast tumor tissue has not been studied comprehensively. More specifically, when biopsy material is analyzed, it remains questionable whether one biopsy is representative of the entire tumor. Therefore, multi-core sampling (n = 6) of tumor tissue from three patients with breast cancer, followed by lipid (0.9- and 1.3-ppm signals) and metabolite quantification using HR MAS 1 H NMR, was performed, resulting in the quantification of 32 metabolites. The mean relative standard deviation across all metabolites for the six tumor cores sampled from each of the three tumors ranged from 0.48 to 0.74. This was considerably higher when compared with a morphologically more homogeneous tissue type, here represented by murine liver (0.16-0.20). Despite the seemingly high variability observed within the tumor tissue, a random forest classifier trained on the original sample set (training set) was, with one exception, able to correctly predict the tumor identity of an independent series of cores (test set) that were additionally sampled from the same three tumors and analyzed blindly. Moreover, significant differences between the tumors were identified using one-way analysis of variance (ANOVA), indicating that the intertumoral differences for many metabolites were larger than the intratumoral differences for these three tumors. That intertumoral differences, on average, were larger than intratumoral differences was further supported by the analysis of duplicate tissue cores from 15 additional breast tumors. In summary, despite the observed intratumoral variability, the results of the present study suggest that the analysis of one, or a few, replicates per tumor may be acceptable, and supports the feasibility of performing reliable analyses of patient tissue.

Fast extraction methodologies for the determination of toxic arsenic in meat

SummaryA nonchromatographic analytical procedure has been developed for the determination of arsenic in meat samples including the major toxic arsenic species arsenite, arsenate, monomethylarsonic acid (MMA) and dimetylarsinic acid (DMA). The method is based on the extraction of arsenic species in mild conditions, selective trivalent hydride formation and final determination by hydride generation atomic fluorescence spectroscopy (HG‐AFS). Different extractant agents and two different procedures, microwave‐assisted extraction (MAE) and ultrasound assisted extraction at room temperature, were evaluated for As species extraction. The method provided a limit of detection of 0.013 ng mL−1 and a mean relative standard deviation in actual samples of 0.3%. Data found for toxic As in meat samples varied from 0.42 ng g−1 in chicken muscle to 68 ng g−1 in pork liver. Percentage of toxic As respect to total As varied in the 9–46% range depending on the meat product.

Orientational effects in mixtures of organic carbonates with alkanes or 1-alkanols

Interactions and structure of organic carbonate + alkane, and 1-alkanol + organic carbonate mixtures have been investigated by means of a set of molar excess functions, enthalpies (HmE), volumes (VmE), isobaric heat capacities, (CpmE) or entropies; and considering internal pressure (Pint); liquid-liquid equilibria or permittivity data. In addition, the mentioned systems have been studied using the Flory model and the concentration-concentration structure factorSCC(0), formalism. The mixtures under consideration are characterized by dipolar interactions and by homocoordination (that is, by interactions between like molecules). In systems with a given solvent, dipolar interactions are weakened in the order: propylene carbonate (PC) > dimethyl carbonate (DMC) > diethyl carbonate (DEC). Comparison of mixtures containing DMC or DEC with those involving 2-propanone or 3-pentanone shows that dipolar interactions are not determined merely by values of the dipole moment, but they also depend on the size group. The enthalpies of the alkanol-carbonate interactions have been evaluated from calorimetric data. They are stronger in DMC solutions, and become weaker when the alcohol size increases in mixtures with a given carbonate. Application of the Flory model to 43 systems of the type 1-alkanol + carbonate provides a mean relative standard deviation for HmE equal to 0.107. Results reveal that orientational effects decrease in the order DEC > PC > DMC. Orientational effects are particularly relevant in methanol or ethanol + DEC mixtures. Interestingly, the mentioned effects are weaker in 1-alkanol + DMC mixtures than in DMC + alkane systems. A similar trend is observed in DEC solutions when the considered alcohol is longer than ethanol.

Directional Transverse Oscillation Vector Flow Estimation.

A method for estimating vector velocities using transverse oscillation (TO) combined with directional beamforming is presented. In directional TO (DTO), a normal focused field is emitted and the received signals are beamformed in the lateral direction transverse to the ultrasound beam to increase the amount of data for vector velocity estimation. The approach is self-calibrating as the lateral oscillation period is estimated from the directional signal through a Fourier transform to yield quantitative velocity results over a large range of depths. The approach was extensively simulated using Field IIpro and implemented on the experimental Synthetic Aperture Real-time Ultrasound System (SARUS) scanner in connection with a BK Medical 8820e convex array transducer. Velocity estimates for DTO are found for beam-to-flow angles of 60°, 75°, and 90°, and vessel depths from 24 to 156 mm. Using 16 emissions, the standard deviation (SD) for angle estimation at depths ranging from 24 to 104 mm is between 6.01° and 0.93° with a mean SD of 2.8°. The mean relative SD for the lateral velocity component is 9.2% and the mean relative bias -3.4% or four times lower than for traditional TO. The approach also works for deeper lying vessels with a slight increase in SD to 15.7%, but a maintained bias of -3.5% from 126 to 156 mm. Data for a pulsating flow have also been acquired for 15 cardiac cycles using a CompuFlow 1000 pump. The relative SD was here 7.4% for a femoral artery waveform.

Results of an interlaboratory comparison of analytical methods for quantification of anhydrosugars and biosugars in atmospheric aerosol

An interlaboratory comparison was performed to evaluate the analytical methods for quantification of anhydrosugars – levoglucosan, mannosan, galactosan – and biosugars – arabitol, glucose and mannitol – in atmospheric aerosol. The performance of 10 laboratories in Italy currently involved in such analyses was investigated on twenty-six PM (particulate matter) ambient filters, three synthetic PM filters and three aqueous standard solutions.An acceptable interlaboratory variability was found, determined as the mean relative standard deviation (RSD%) of the results from the participating laboratories, with the mean RSD% values ranging from 25% to 46% and decreasing with increasing sugar concentration. The investigated methods show good accuracy, evaluated as the percentage error (ε%) related to mean values, since method biases ranged within ±20% for most of the analytes measured in the different laboratories.The detailed investigation (ANOVA analysis at p < 0.05) of the contribution of each laboratory to the total variability and the measurement accuracy shows that comparable results are generated by the different methods, despite the great diversity in terms of extraction conditions, chromatographic separation - more recent LC (liquid chromatography) and EC (exchange chromatography) methods compared to more widespread GC (gas chromatography) - and detection systems, namely PAD (pulsed amperometric detection) or mass spectrometry.

Evaluation of different approaches for identifying optimal sites to predict mean hillslope soil moisture content

The identification of representative soil moisture sampling sites is important for the validation of remotely sensed mean soil moisture in a certain area and ground-based soil moisture measurements in catchment or hillslope hydrological studies. Numerous approaches have been developed to identify optimal sites for predicting mean soil moisture. Each method has certain advantages and disadvantages, but they have rarely been evaluated and compared. In our study, surface (0–20cm) soil moisture data from January 2013 to March 2016 (a total of 43 sampling days) were collected at 77 sampling sites on a mixed land-use (tea and bamboo) hillslope in the hilly area of Taihu Lake Basin, China. A total of 10 methods (temporal stability (TS) analyses based on 2 indices, K-means clustering based on 6 kinds of inputs and 2 random sampling strategies) were evaluated for determining optimal sampling sites for mean soil moisture estimation. They were TS analyses based on the smallest index of temporal stability (ITS, a combination of the mean relative difference and standard deviation of relative difference (SDRD)) and based on the smallest SDRD, K-means clustering based on soil properties and terrain indices (EFs), repeated soil moisture measurements (Theta), EFs plus one-time soil moisture data (EFsTheta), and the principal components derived from EFs (EFs-PCA), Theta (Theta-PCA), and EFsTheta (EFsTheta-PCA), and global and stratified random sampling strategies. Results showed that the TS based on the smallest ITS was better (RMSE=0.023m3m−3) than that based on the smallest SDRD (RMSE=0.034m3m−3). The K-means clustering based on EFsTheta (-PCA) was better (RMSE <0.020m3m−3) than these based on EFs (-PCA) and Theta (-PCA). The sampling design stratified by the land use was more efficient than the global random method. Forty and 60 sampling sites are needed for stratified sampling and global sampling respectively to make their performances comparable to the best K-means method (EFsTheta-PCA). Overall, TS required only one site, but its accuracy was limited. The best K-means method required <8 sites and yielded high accuracy, but extra soil and terrain information is necessary when using this method. The stratified sampling strategy can only be used if no pre-knowledge about soil moisture variation is available. This information will help in selecting the optimal methods for estimation the area mean soil moisture.

Fluoride Determination by Ion Chromatography in Fluorocarbon Coatings

A quantitative ion chromatographic analytical method for the determination of fluorine in fluorocarbon coatings is proposed. The extraction of the anions from the samples was performed using potassium hydroxide after centrifugation drying to dissolved at preference temperature. Using H column to remove large amounts of potassium ions in the solution。In paper describe the observed limits of detection and of quantitation in mg kg-1 and the mean relative standard deviation in percent This method is simple operation, less interference factors, fast analysis speed, the determination results accurate and reliable, with good repeatability and reproducibility.

DESENVOLVIMENTO DE AMOSTRADOR PASSIVO SENSÍVEL PARA MONITORAMENTO DE POLUIÇÃO ATMOSFÉRICA POR DIÓXIDO DE NITROGÊNIO

A passive sampler constructed with a new type of material and used for measurement of ambient nitrogen dioxide is presented. The sampler was constructed with parts of two 50 mL conical centrifuge tubes. The procedure is based on NO2 uptaken on cellulose filter impregnated with triethanolamine. After sampling, the analyte is solubilized and placed to react with Griess-Saltzman solution. The absorbance of the formed complex is determined at 540 nm. A mean relative standard deviation of 9,72% was obtained using samplers exposed in triplicate, and a determination coefficient (R-2) of 0,979 was achieved in parallel measurements using the samplers and a commercial NOx monitor. Advantages of the technique include ease of use, the ready availability of components, and excellent sensitivity.

CFC-11, CFC-12 and HCFC-22 ground-based remote sensing FTIR measurements at Réunion Island and comparisons with MIPAS/ENVISAT data

Abstract. Profiles of CFC-11 (CCl3F), CFC-12 (CCl2F2) and HCFC-22 (CHF2Cl) have been obtained from Fourier transform infrared (FTIR) solar absorption measurements above the Saint-Denis (St Denis) and Maïdo sites at Réunion Island (21° S, 55° E) with low vertical resolution. FTIR profile retrievals are performed by the well-established SFIT4 program and the detail retrieval strategies along with the systematic/random uncertainties of CFC-11, CFC-12 and HCFC-22 are discussed in this study. The FTIR data of all three species are sensitive to the whole troposphere and the lowermost stratosphere, with the peak sensitivity between 5 and 10 km. The ground-based FTIR data have been compared with the collocated Michelson Interferometer for Passive Atmospheric Sounding (MIPAS/ENVISAT) data and found to be in good agreement: the observed mean relative biases and standard deviations of the differences between the smoothed MIPAS and FTIR partial columns (6–30 km) are (−4.3 and 4.4 %), (−2.9 and 4.6 %) and (−0.7 and 4.8 %) for CFC-11, CFC-12 and HCFC-22, respectively, which are within the combined error budgets from both measurements. The season cycles of CFC-11, CFC-12 and HCFC-22 from FTIR measurements and MIPAS data show a similar variation: concentration is highest in February–April and lowest in August–October. The trends derived from the combined St Denis and Maïdo FTIR time series are −0.86 ± 0.12 and 2.84 ± 0.06 % year−1 for CFC-11 and HCFC-22, respectively, for the period 2004 to 2016, and −0.76 ± 0.05 % year−1 for CFC-12 for 2009 to 2016. These measurements are consistent with the trends observed by the National Oceanic and Atmospheric Administration (NOAA) Global Monitoring Division's (GMD) Halocarbons &amp;amp; other Atmospheric Trace Species Group (HATS) measurements at Samoa (14.2° S, 170.5° W) for CFC-11 (−0.87 ± 0.04 % year−1), but slightly weaker for HCFC-22 (3.46 ± 0.05 %) year−1 and stronger for CFC-12 (−0.60 ± 0.02 % year−1).

Time-stability of soil water content (SWC) in an Atlantic Forest - Latosol site

Time-stability of the soil water content (SWC) under influence of a native forest has great interest, however, it has been little scientifically explored in tropical and subtropical regions. This study aimed to monitor in a systematic way the SWC at soil depth to analyze its space-time variability and time-stability under conditions of an Atlantic Forest remnant, a native environment of southeastern Brazil. Time-stability was monitored at five soil depths (0.10m, 0.20m, 0.30m, 0.40m and 1.0m), analyzing the statistical dispersion measures (SDM). Based on SDM, we also aimed to infer about the time-stability locations that are most representative for the study site. The sampling effort for SWC comprised a monthly recording time step at 32 points in the site from June/2013 to January/2016. We observed a decrease in the variability of the following SDM with increase of soil depth: mean relative difference (δij), standard deviation and Temporal Stability Indicator (TSI). It was possible to infer that local topographic elements induced the time-stability. It was not possible to select only one location representative for SWC since the statistical criteria did not adequately converge for all soil depths at the same location. However, the point locations selected for each depth produced adequate statistics of validation. We were able to identify the relation between the points and the landscape representation indicators, which can help in the endeavor of identification of point locations which are more stable and the time-stability of SWC in a native forest site.