Blank Values Research Articles

Determination of plutonium isotope ratios in individual uranium–plutonium mixed particles with inductively coupled plasma mass spectrometry

An analytical technique was developed by a combination of single particle dissolution, chemical separation of uranium, plutonium and americium with extraction chromatography using UTEVA resins and measurement with inductively coupled plasma mass spectrometry. This method was applied to plutonium isotope ratio analysis of individual U–Pu particles with U/Pu ratios ranging from 1 to 70. Consequently, 240Pu/239Pu, 241Pu/239Pu and 242Pu/239Pu isotope ratios were successfully determined, while it was impossible to determine 238Pu/239Pu ratios due to the high process blank values on m/z 238.

Monitoring of phthalates in foodstuffs using gas purge microsyringe extraction coupled with GC–MS

Phthalate esters (PAEs) are commonly used as nonreactive plasticisers in vinyl plastics to increase the flexibility of plastic polymers. Numerous studies have indicated that the PAEs as a class of endocrine-disrupting chemicals. In addition, the studies have also shown that a major source of human exposure to phthalates is the diet. To date, the largest problem in PAEs analysis is the high blank value because PAEs are widely used in various applications and products. To overcome this shortcoming, gas purge microsyringe extraction (GP-MSE) was applied, which established a new and low-blank-value analytical method for PAE analysis to analyse PAEs in foodstuffs. In this study, GP-MSE was used as a clean-up method, and the overall recoveries ranged from 85.7 to 102.6%, and the RSD was less than 10%. More importantly, this method can overcome the problem of the high blank value in PAE analysis. This method was applied for measuring PAEs in 78 foodstuffs. The results showed that a wide variety of PAE concentrations were found in the different groups, and the content of PAEs (varies from 658 to 1610ngg−1 fresh weight) is greatest in seafood. The concentrations were in the following order: DEHP>DBP>DEP≈DMP>BBP≈DNOP. Finally, the daily intake of PAEs was estimated for adults based on the levels of PAEs in foodstuffs. The total EDIdiet values of 3.2 and 12.9μgkg−1 bw d−1 were calculated for DEHP based on the mean and highest concentrations in foodstuffs, respectively.

Method validation and quality assurance of an ICP-MS protocol for the evaluation of trace and major elements in ambient aerosol samples and application to an air quality surveillance network

This study presents the results of a quality assurance evaluation program applied to the method routinely used for the evaluation of a large elemental profile in aerosol samples from the air quality surveillance network of Extremadura, Spain, where low pollution levels are usually encountered. A critical evaluation of the most relevant analytical steps is presented, including long-term blank values evaluation, limits of detection, certified reference material recoveries, method uncertainty and results of comparison studies for gravimetric and trace element analysis. Results obtained at the air quality network of Extremadura for the gravimetric and multielemental analysis are presented for the 2008 campaign.

Reconstruction of MODIS land-surface temperature in a flat terrain and fragmented landscape

Moderate Resolution Imaging Spectroradiometer (MODIS) land-surface temperature (LST) products provide important and reliable time-series data for the examination of global climate change, water cycling, and ecological evolution. In particular, in recently developed remote-sensing evapotranspiration models, such as the Surface Energy Balance Algorithm for Land and the Surface Energy Balance System, LST is a critical parameter that can directly influence the accuracy and integrity of final results. However, clouds and other atmospheric disturbances, which cover a large area throughout most of the year, are read as blank values by these programs, creating a problem. To solve this, a number of algorithms have been proposed to reconstruct LST data, but few can be used to evaluate flat and relatively fragmented landscape regions, such as the Yellow River Delta in China. Here, we conducted an analysis where we considered the LST of a flat area to be mainly influenced by land cover and other environmental elements (e.g. soil moisture). We used maps such as land cover, normalized difference vegetation index, and MODIS band 7 as additional data in the reconstruction model. All of the LST pixels we used were randomly divided into two parts: one part was used to train the model, and the other part was used to validate the calculated results. Three different methods have been developed to reconstruct LST data – linear regression, regression tree (RT) analysis, and artificial neural networks. In comparing these methods, we found that the RT method is able to estimate the LST of MODIS pixels with the greatest accuracy, and that it is both convenient and useful for reconstructing the LST map in flat and fragmented regions.

The removal of Triton X-100 by dialysis is feasible!

Triton X-100 has been widely used in many analytical and preparative protocols for a long time. Nevertheless, mass spectrometry, chromatographic separation, and spectrophotometric readout may be considerably hampered by this detergent due to signal suppression, complex formation, and high blank values, respectively. Additionally, Triton X-100 is not safe to remove prior to analytics. Here, microdialysis is introduced as a parallelizable, high-throughput method to clean samples from Triton X-100 with high efficacy and precision. To achieve this, we exploit the potential to considerably increase the critical micellar concentration of Triton X-100 by alteration of matrix properties. To that end, addition of several chaotropic compounds and organic solvents has been shown to increase the critical micellar concentration as well as the removal rate of the detergent. For application, matrix additives can be selected for analyte stability requirements out of a variety of compounds. Conveniently, all these additives are removable subsequently using the same microdialysis tool for downstream analytics requirements. Applicability and protocols are shown with proteomic sample preparation of purified proteins and complex protein mixtures prior to matrix-assisted laser desorption ionization (MALDI) mass spectrometry.

Single-cell multiple gene expression analysis based on single-molecule-detection microarray assay for multi-DNA determination

We report a novel ultra-sensitive and high-selective single-molecule-detection microarray assay (SMA) for multiple DNA determination. In the SMA, a capture DNA (DNAc) microarray consisting of 10 subarrays with 9 spots for each subarray is fabricated on a silanized glass coverslip as the substrate. On the subarrays, the spot-to-spot spacing is 500 μm and each spot has a diameter of ∼300 μm. The sequence of the DNAcs on the 9 spots of a subarray is different, to determine 8 types of target DNAs (DNAts). Thus, 8 types of DNAts are captured to their complementary DNAcs at 8 spots of a subarray, respectively, and then labeled with quantum dots (QDs) attached to 8 types of detection DNAs (DNAds) with different sequences. The ninth spot is used to detect the blank value. In order to determine the same 8 types of DNAts in 10 samples, the 10 DNAc-modified subarrays on the microarray are identical. Fluorescence single-molecule images of the QD-labeled DNAts on each spot of the subarray are acquired using a home-made single-molecule microarray reader. The amounts of the DNAts are quantified by counting the bright dots from the QDs. For a microarray, 8 types of DNAts in 10 samples can be quantified in parallel. The limit of detection of the SMA for DNA determination is as low as 1.3×10(-16) mol L(-1). The SMA for multi-DNA determination can also be applied in single-cell multiple gene expression analysis through quantification of complementary DNAs (cDNAs) corresponding to multiple messenger RNAs (mRNAs) in single cells. To do so, total RNA in single cells is extracted and reversely transcribed into their cDNAs. Three types of cDNAs corresponding to beta-2-microglobulin, glyceraldehyde-3-phosphate dehydrogenase and ribosomal protein, large, P2 mRNAs in single human breast cancer cells and 5 random synthetic DNAts are simultaneously quantified to examine the SMA and SMA-based single-cell multiple gene expression analysis.

Development and application of a shipboard method for spectrophotometric determination of trace dissolved manganese in estuarine and coastal waters

A shipboard method for the determination of trace dissolved manganese in estuarine and coastal waters was developed using a technique of reverse flow injection analysis, which adopted a 1-m liquid waveguide capillary cell and spectrophotometric detection of manganese derivation with 1-(2-pyridylazo)-2-naphthol (PAN). The design of dual-sample-carrier speeded up the sample throughput and eliminated the Schlieren effect. The salinity of estuarine and coastal waters caused a huge increase in the blank absorption value at the maximum absorption wavelength; therefore, a less sensitive detection wavelength was selected to achieve a low blank value while the method sensitivity was not significantly decreased. Method parameters were optimized. The salinity effect from estuarine and coastal waters was carefully investigated, and interference from iron was evaluated. The proposed method had high sensitivity with a detection limit of 3.0nmolL−1 and a wide linear range of 10–1500nmolL−1 for dissolved manganese in seawater (S=35). The analytical results of five water samples with different salinities obtained using the proposed method showed good agreement with those using a reference ICP-MS method. The sample throughput of the proposed method was 120h−1, which was capable of obtaining high spatial and temporal resolution data in shipboard analysis. The proposed method had the advantages of convenient application in estuarine and coastal waters with different salinities, low detection limit, as well as high sample throughput. The proposed method was successfully applied to a 24h on-line analysis and a shipboard underway analysis of dissolved manganese in the Jiulongjiang Estuary.

An integrated approach for the chemical characterization and oxidative potential assessment of indoor PM2.5

An integrated approach has been developed for the multi-component analysis of indoor PM2.5 collected onto the same quartz fiber filter (QFF) by using an innovative combination of techniques such as inductively coupled sector field plasma mass spectrometry (ICP-SF-MS) with vapor-phase microwave-assisted aqua regia or sonication-assisted water extraction, ion chromatography, thermal–optical transmittance as well as high performance liquid chromatography and enzyme-linked 5,5′-dithio-bis(2-nitrobenzoic acid) assay for the determination of elemental composition, major inorganic ions, elemental/organic carbon (EC/OC) as well as oxidative potential (OP) through ascorbate (AA) and reduced glutathione (GSH) depletion, respectively. The low mass of PM2.5 collectable indoors, the elemental blank values of the QFFs and the sample volume/acidity requirements of the ICP-SF-MS represented a challenge for elemental determination. Finally, this approach was successfully applied for determination of 15 elements (Al, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Rb, Sr, Mo, Cd, Sn and Pb) at the ngm−3 level in more than two-thirds of indoor PM2.5 (n=25) collected in mechanically ventilated offices within the European Union project OFFICAIR at increased sampling flow rates (0.6m3h−1–2.3m3h−1) and sampling time (cca. 100h) in the acidic/aqueous extracts. The concentration of Cl−, NO3−, SO42−, Na+, NH4+, K+, Ca2+, Mg2+, OC and EC was at the μgm−3 level in the aqueous extracts. This new approach aiming at the comprehensive characterization of low mass indoor PM2.5 samples allowed assessment of OPAA and OPGSH in all samples. The PM2.5 critical sample mass to achieve elemental determination was approximately 400μg.

Precise determination of dissolved platinum in seawater of the Japan Sea, Sea of Okhotsk and western North Pacific Ocean

Platinum is among the least abundant elements in the earth's crust and is now widely used in various products such as catalytic converters in automobiles and anticancer drugs. Consequently, the concentration of Pt in urban aquatic environments is increasing. However, little is known about the distributions and geochemical cycles of Pt in the ocean owing to its low concentrations in seawater (<0.2pmol/L). In this study, we report an improved analytical method for determining sub-picomolar levels of Pt in seawater, and reveal the distributions of Pt in the Japan Sea, Sea of Okhotsk, and western North Pacific Ocean.For determining sub-picomolar levels of Pt in seawater, we used isotope-dilution ICP-MS (Inductively Coupled Plasma Mass Spectrometry) after column preconcentration with an anion exchange resin. This method facilitated highly accurate analysis of Pt in seawater using small sample volumes (~1L). The detection limit and procedural blank value for this method were 0.015 and approximately 0.01pmol/L, respectively. We obtained conservative vertical distributions, with nearly constant Pt concentrations between 0.19 and 0.25pmol/L in the Japan Sea, Sea of Okhotsk, and western North Pacific Ocean. Judging from the constant dissolved Pt profiles, little anthropogenic influence of Pt is apparent in the open oceans at the present time.

Polychlorinated biphenyls, polychlorinated dibenzo-p-dioxins and dibenzofurans, and polycyclic aromatic hydrocarbons around a thermal desorption plant in China.

This study was launched to establish comprehensive environmental monitoring on the levels and patterns of polychlorinated biphenyls (PCBs), polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs), and polycyclic aromatic hydrocarbons (PAHs) both in soil and ambient air around a thermal desorption plant in China. All 209 congeners of PCBs, 136 congeners of PCDD/Fs (P = 4 to 8) and 16 EPA priority PAHs were analyzed. The concentration of PCBs ranged from 20.0 to 536 ng g(-1) (or 0.077-5.27 pg WHO-TEQ g(-1)) in soil and from 972 to 991 ng Nm(-3) (or 0.245-0.374 pg WHO-TEQ Nm(-3)) in air samples, much higher than the levels in cities. A single soil sampling point could have been affected by some transfer of PCBs from the untreated soil by the fingerprint characteristics and the statistical analysis. Establishing blank values prior to the start-up of new plant is a safe and sure method to establish subsequent impacts on the environment. During the treatment of hazardous waste, strict control of all waste materials and all emissions is required.

Poly(oligoethylene glycol methacrylate) dip-coating: turning cellulose paper into a protein-repellent platform for biosensors.

The passivation of nonspecific protein adsorption to paper is a major barrier to the use of paper as a platform for microfluidic bioassays. Herein we describe a simple, scalable protocol based on adsorption and cross-linking of poly(oligoethylene glycol methacrylate) (POEGMA) derivatives that reduces nonspecific adsorption of a range of proteins to filter paper by at least 1 order of magnitude without significantly changing the fiber morphology or paper macroporosity. A lateral-flow test strip coated with POEGMA facilitates effective protein transport while also confining the colorimetric reporting signal for easier detection, giving improved performance relative to bovine serum albumin (BSA)-blocked paper. Enzyme-linked immunosorbent assays based on POEGMA-coated paper also achieve lower blank values, higher sensitivities, and lower detection limits relative to ones based on paper blocked with BSA or skim milk. We anticipate that POEGMA-coated paper can function as a platform for the design of portable, disposable, and low-cost paper-based biosensors.

Microwave-induced combustion of crude oil for further rare earth elements determination by USN–ICP-MS

A procedure for light and heavy crude oils digestion by microwave-induced combustion (MIC) is proposed for the first time for further rare earth elements (REE) determination by inductively coupled plasma mass spectrometry (ICP-MS) equipped with an ultrasonic nebulizer (USN). Samples of crude oil (API density of 10.8–23.5, up to 250mg) were inserted in polycarbonate capsules and combusted using 20bar of oxygen and 50μL of 6molL−1 ammonium nitrate as igniter. Nitric acid solutions (1–14.4molL−1) were evaluated for analyte absorption and a reflux step was applied after combustion (5min of microwave irradiation at 1400W) in order to achieve better analyte recoveries. Accuracy was evaluated using a spiked sample and also by comparison of results obtained by microwave-assisted digestion combined to ultraviolet radiation (MW–UV) and by neutron activation analysis (NAA). Using 3molL−1 HNO3, quantitative recoveries (better than 97%) were obtained for all analytes. Blank values were always negligible. Agreement was higher than 96% for La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu and Y by comparison of results with those obtained by MW–UV and by NAA (only for La, Ce, Nd, Sm, and Yb). Residual carbon content in digests using MIC was always below 1%. As an advantage over conventional procedures for crude oil digestion, using MIC, it was possible to use diluted acid as absorbing solution, obtaining better limits of detection and avoiding interferences in REE determination by USN–ICP-MS.

Laboratory intercomparison of marine particulate digestions including Piranha: a novel chemical method for dissolution of polyethersulfone filters

The US GEOTRACES program will generate marine particulate trace metal data over spatial scales and depth resolutions never before sampled. In preparation for these analyses, we conducted a four laboratory intercomparison exercise to determine our degree of intercalibration and to examine how several total digestion procedures perform on marine particles collected on polyethersulfone (PES, Pall Supor) filters. In addition, we present a new chemical method for complete dissolution of PES filters using a combination of sulfuric acid and hydrogen peroxide called Piranha reagent that can be conducted using minimal specialized equipment. Intralaboratory subsampling variability across 142 mm particulate matter filters, for subsamples representing approximately 10 L filtered seawater, was measured at an element‐dependent 1% to 9% (RSD: 1δ/x-, %), whereas interlaboratory variability accounted for an additional 5% to 42% variability. Lab‐ and element‐specific trends in recoveries are discussed, though all digestion methods tested appear to completely solubilize particulate material. We recommend rigorous determination of digest‐acid and/or filter process blanks, as some particulate elements (namely Pb and Zn) have natural abundances that approach blank values.

Study on Carbon and Sulfur Detection by Using Infrared Absorption Method

This paper focuses on discussing the principle of detecting carbon and sulphur by using infrared absorption method, characteristics of high-frequency heating, system blank value, and method for detecting trace carbon and sulphur.

Applied Technology with Methods for Measuring Sulfur Blank Values by Using Infrared Absorption Method

Currently, there are three major methods for infrared carbon-sulfur analyzer to measure blank values. This paper discusses the advantages and disadvantages of the three methods by using the measured test data from specific tests, and finally makes a conclusion that, the Cycle Measurement of Sulfur Blank Value (CMSBV) created by JIANHUAN WEI is the most effective method. Entering this sulfur blank value into analyser, the automatic deduction of blank values will be performed. As a result, the impact of the blank value on sulfur measurement can be eliminated. Key words: Sulfur blank value, direct measurement method, indirect measurement method, The Cycle Measurement of Sulfur Blank Value (CMSBV)

Biomonitoring of infant exposure to phenolic endocrine disruptors using urine expressed from disposable gel diapers.

Infant exposure to endocrine disruptors (EDs) may cause adverse health effects because of their fast growth and development during this life stage. However, collecting urine from infants for exposure assessment using biological monitoring is not an easy task. For this purpose, we evaluated the feasibility of using urine expressed from disposable gel absorbent diapers (GADs) as a matrix for biomonitoring selected phenolic EDs. GADs urine was expressed with the assistance of CaCl(2) and was collected using a device fabricated in our laboratory. The analytes were extracted and concentrated using a liquid-liquid method and their hydroxyl groups were modified by dansyl chloride to enhance their chromatography and detection. Finally, the analytes were measured by high-performance liquid chromatography (HPLC) coupled with electrospray ionization (ESI) tandem mass spectrometry (MS/MS). The target chemicals were bisphenol A, triclosan, 17 α-ethynylestradiol, the natural hormone estrone, and 17 β-estradiol. The ratio of the CaCl(2) to the urine-wetted gel absorbent, variation of the inter-urination volume, and analyte deposition bias in the diaper were assessed. Analyte blank values in the diapers, the sample storage stabilities, and recoveries of the analytes were also evaluated. The results showed that 70-80 % of the urine could be expressed from the diaper with the assistance of CaCl(2) and 70.5-124 % of the spiked analytes can be recovered in the expressed urine. The limits of detections (LODs) were 0.02-0.27 ng/mL, well within the range for detection in human populations. Our pilot data suggest that infants are widely exposed to the selected EDs.

Fluorescence detection for phosphate monitoring using reverse injection analysis

We present a novel design for a compact flow-through fluorescence detector for flow analyses applications and prove its functionality in the experiment. The detector operates by detecting the diffusely emitted fluorescence in a glass capillary, which is a measure for the concentration of the analyte to be detected. The fluorescence is excited via an axially coupled fibre providing LED light and is collected by a photodiode. As model analyte we used dissolved reactive phosphate. The determination of the phosphate concentration is based on the reaction of molybdate to phosphomolybdate, which quenches the fluorescence of Rhodamine 6G. The experiments rely on a reversed flow injection analysis system especially designed for decoupling the analytical setup from environmental pressure for in situ applications. By combining the optics part and the fluidic setup a measuring range of 0–40µgL−1 PO4–P with detection limits of 0.22µgL−1 PO4–P (7nmolL−1) for water and of 0.45µgL−1 PO4–P (14.5nmolL−1) for seawater have been obtained. Our novel system has a sampling frequency of up to 300 samples per hour and achieves a repeatability between 0.6% (RSD) for the blank value signal (n=15) and 4.6% (RSD) for a phosphate concentration of 20.8µgL−1 PO4–P (n=15).

Determination of Chromium(III), Chromium(VI), and Chromium(III) acetylacetonate in water by ion-exchange disk extraction/metal furnace atomic absorption spectrometry

A new method for the separate determination of Chromium(III) (Cr(III)), Chromium(VI) (Cr(VI)), and Cr(III) acetylacetonate (Cr(acac)3) in water was developed using a cation-exchange extraction disk (CED) and an anion-exchange extraction disk (AED) combined with metal furnace atomic absorption spectrometry (MFAAS). A 100-mL water sample was adjusted to pH5.6 and passed through the CED placed on the AED. Cr(acac)3 and Cr(III) were adsorbed on the CED, and Cr(VI) was adsorbed on the AED. The adsorbed Cr(acac)3 was eluted with 50mL of carbon tetrachloride, followed by the elution of Cr(III) with 50mL of 3molL−1 nitric acid. Cr(VI) was eluted with 50mL of 3molL−1 nitric acid. The chemical species of Cr eluted from the CED with carbon tetrachloride was identified as Cr(acac)3 using infrared spectroscopy. The eluate of Cr(acac)3 was diluted to 100mL with carbon tetrachloride, and those of Cr(III) and Cr(VI) were diluted to 100mL with deionized water. All of the solutions were subsequently analyzed by MFAAS. The calibration curve for the Cr(acac)3 aqueous solutions exhibited good linearity in the range of 0.1 to 1ng. The detection limit of Cr, which corresponded to three times the standard deviation (n=10) of the blank values, was 20pg. The recovery test for Cr(III), Cr(VI), and Cr(acac)3 exhibited desirable results (96.0%–107%) when 5μg of each species (50μgL−1) was added to 100mL water samples (i.e., tap water, rainwater, and bottled drinking water). In a humic acid solution, Cr(acac)3 was quantitatively recovered (103%), but Cr(III) and Cr(VI) exhibited poor recoveries (i.e., 84.8% and 78.4%, respectively).

Determination of trace elements in raw material for polyurethane production using direct sampling graphite furnace atomic absorption spectrometry

The concentration of Fe, Mg, Mn and Na at ultra-trace levels was determined in polymeric diphenylmethane dianiline, a raw material for polyurethane production, by direct sampling graphite furnace atomic absorption spectrometry (DS-GFAAS). A Zeeman-effect background correction system operated in 2-field or 3-field dynamic modes was used. Calibration was carried out using aqueous reference solutions and a sample mass between 0.5 and 35 mg was used. The relative standard deviation was calculated after successive measurements (number of replicates was 14 to 23 throughout the range of sample mass) and was below 15%. Blank values obtained using DS-GFAAS were lower than those obtained with other evaluated procedures. The accuracy was evaluated by comparison of the results with those obtained by inductively coupled plasma optical emission spectrometry (ICP-OES) after microwave assisted digestion (MAD) in closed vessels and microwave-induced combustion (MIC). There were no statistical differences (confidence level 95%) between the results obtained for the analysis of all the analytes by DS-GFAAS and those obtained by ICP-OES after MAD and MIC. The limits of detection were considerably lower (0.06 to 0.27 ng g−1) in comparison with those obtained by ICP-OES after MAD (35 to 5443 ng g−1) and MIC (12 to 4890 ng g−1).

A Simple and Rapid Method for the Detection of Non-Ionic Surfactants

A spectrophotometric approach for the detection of non-ionic surfactant (Triton X-100) has been proposed in this paper. This method does not involve extraction of the ion-associate with harmful solvents, but employs adhesion of the ion-association of potassium/non-ionic surfactants complex and tetraphenylporphyrin tetrasulfonic acid obtained by vigorous shaking. The adhered ion-associate was dissolved with water and its absorbance was measured. The sensitivity for Triton X-100 was determined to be 0.146 (expressed as absorbance of 1 mg/L solution). The adhesion tendency of ion-associate was found to be dependent on the water contact angle, which in turn was influenced by a high adhesion of the ion-associate and by low blank values. In this respect, a tetrafluo-roethylene vessel was found to be the most suitable for the detection of non-ionic surfactants. This spectrophotometrical method is simply and rapidly performed by a procedure based on mechanical shaking and can be employed to detect non-ionic surfactants containing more than 7 polyethylene oxide units.