Single Reaction Chamber Research Articles

Profiling of BCLxL Protein Complexes in Non-Small Cell Lung Cancer Cells via Multiplexed Single-Molecule Pull-Down and Co-Immunoprecipitation.

We introduce multiplexed single-molecule pull-down and co-immunoprecipitation, named m-SMPC, an analysis tool for profiling multiple protein complexes within a single reaction chamber using single-molecule fluorescence imaging. We employed site-selective conjugation of biotin and fluorescent dye directly onto the monoclonal antibodies, which completed an independent sandwich immunoassay without the issue of host cross-reactivity. We applied this technique to profile endogenous B-cell lymphoma extra-large (BCLxL) complexes in non-small cell lung cancer (NSCLC) cells. Up to three distinct BCLxL complexes were successfully detected simultaneously within a single reaction chamber without fluorescence signal crosstalk. Notably, the NSCLC cell line EBC-1 exhibited high BCLxL-BAX and BCLxL-BAK levels, which closely paralleled a strong response to the BCLxL inhibitor A-1331852. This streamlined method offers the potential for quantitative biomarkers derived from protein complex profiling, paving the way for their application in protein complex-targeted therapies.

Microwave-induced combustion for further determination of potentially toxic elements in honey by ICP-MS.

Microwave-induced combustion (MIC) was proposed in this study for honey decomposition aiming for As, Cd, Hg, and Pb determination by inductively coupled plasma mass spectrometry (ICP-MS). Sample mass (up to 1.0g), absorbing solution (0.5 to 14.4mol L-1 HNO3, and H2O), heating program, and combustion aids were evaluated. The Eurachem guidelines were used for method validation. The proposed method enabled combustion of a high sample mass (0.8g of honey, with 0.4g of microcrystalline cellulose and 100 µL of 6mol L-1 NH4NO3) using 6mL of an absorbing solution consisting of 1mol L-1 HNO3, which resulted in low residual carbon in solution (< 25mg L-1). Honey samples from different geographical origins were analyzed. Results showed no significant difference in comparison to other two microwave decomposition methods, based on microwave-assisted wet digestion with single reaction chamber (MAWD-SRC) and microwave-assisted wet digestion (MAWD). Standard addition experiments resulted in recoveries higher than 98%. The limits of detection ranged from 1.10 (As) to 4.60ngg-1 (Pb). In addition to using only diluted reagents and resulting in digests virtually free of interferences, the proposed method was faster (< 30min) than most of those presented in the literature.

Comparative analysis of rare earth elements concentrations in domestic dogs and Apennine wolves of Central Italy: Influence of biological, nutritional, and lifestyle factors

Rare Earth Elements (REEs) are strategical elements playing a crucial role in the industry, especially in producing high-tech materials. Therefore, REEs are new contaminants of emerging concerns. However, due to the lack of exposure data on REE occurrence in environmental matrices, especially in European countries, it is still tricky to establish environmental background levels to assess the ecotoxicological risk related to REEs exposure. The present study aimed to evaluate the liver concentrations of REEs in domestic dogs (Canis lupus familiaris) and Apennine wolves (Canis lupus italicus) living in the Abruzzo region, Italy. Moreover, for the scope of the present study, the dog's group was divided according to their sex, age, lifestyle, and diet. Wolves were categorized concerning their sex and genetic characteristics. Liver samples from dogs and wolves were collected during diagnostic necropsies from carcasses, sample mineralization was performed by a microwave digestion system with a single reaction chamber, and simultaneous determination of the presence of REEs was performed by Inductively Coupled Plasma Mass Spectrometer (Q-ICP-MS) using standard mode for all rare earth elements except scandium (Sc) which was acquired in kinetic energy discrimination (KED) mode. Hepatic concentrations of REEs were statistically significantly higher in wolves compared to dogs. Moreover, significant differences in REEs concentrations arose also from the genetic type of wolf, since “pure wolves” had higher liver concentrations of REEs compared to wolf-dog hybrids. Female and adult dogs also showed elevated REEs compared to male and juvenile dogs, while no significant differences were demonstrated for dogs' diet and lifestyle. The results of the present study confirm the exposure of domestic and wild carnivores to REEs, showing also the ability of REEs to accumulate in carnivore livers, suggesting the potential role of this species as an alternative bioindicator.

Single reaction chamber microwave digestion coupled with ICP-MS for the determination of ultra-trace mercury in rocks.

In this study, a method for rock digestion using a single reaction chamber (SRC) microwave system was established. Nitric acid (HNO3) and hydrofluoric acid (HF) were used as digestion agents, and the determination of mercury (Hg) in rocks was performed by inductively coupled plasma mass spectrometry (ICP-MS). The optimal conditions for the SRC microwave system were achieved at 260 °C and 70 bar, with a mixture of 3 mL of 65-68 wt% HNO3 and 1 mL of 49 wt% HF when the sample weight is in the range of 0.025-0.05 g. The method quantitation limit (MQL) was determined to be 0.0016 mg kg-1. Measurement accuracy was evaluated using five Chinese nationally certified reference materials, demonstrating good consistency between measurement results and certified values. The method was applied to two rock samples, resulting in a recovery rate ranging from 105% to 109%. This method exhibits high sensitivity, stability, and low acid consumption. Importantly, it provides a reliable and efficient determination method for Hg in rocks, which is of great significance in geochemical analysis.

Self-actuated microfluidic chiplet for two-stage multiplex nucleic acid amplification assay.

Effective diagnosis of comorbidities and infectious diseases that present similar symptoms requires point-of-need assays capable of co-detecting and differentiating among multiple co-endemic pathogens to enable timely, precision medicine and effective control measures. We previously developed a two-stage isothermal amplification assay dubbed Penn-RAMP to address this need. Penn-RAMP's first stage comprises a recombinase polymerase amplification (RPA), which amplifies all targets of interest in a single reaction chamber for a short duration. The RPA amplicons are then aliquoted into multiple loop-mediated isothermal amplification (LAMP) reaction chambers, each customized with pre-dried primers to amplify a single target or a group of targets. To enable Penn-RAMP at the point of need, we describe here a self-actuated Penn-RAMP chiplet that accommodates the Penn-RAMP assay. Our chiplet employs temperature-controlled phase change valves and capillary valves to self-aliquot first-stage amplicons into multiple (five) second-stage reaction chambers and to seal these chambers. The functionality of our device is demonstrated by co-detecting plant pathogens. The analytical performance of our chiplet is comparable to that of the benchtop Penn-RAMP assay and surpasses that of standalone LAMP assays. Our self-actuated chiplet can be operated standalone with purified nucleic acids or as the downstream amplification module of a sample preparation cassette.

Fast and green microwave-assisted digestion with diluted nitric acid and hydrogen peroxide and subsequent determination of elemental composition in brown and white rice by ICP-MS and ICP-OES

For the elemental determination of rice, a microwave-assisted sample preparation method employing diluted HNO3 and H2O2 under high temperature and pressure was developed in a rapid and eco-friendly manner. The analysis was performed using inductively coupled plasma mass spectrometry (ICP-MS) and inductively coupled plasma optical emission spectrometry (ICP-OES). At 280 °C and 160 bar, the optimal condition for microwave-assisted wet digestion in a single reaction chamber was achieved with a mixture consisting of 3 mL of 0.1 mol L−1 HNO3 and 5 mL of 30% H2O2 (0.25 g rice sample). The optimized procedure yielded a low residual acidity (RA) of 0.017 mol L−1 and low residual carbon content (RCC) of 355 mg L−1. The limits of detection (LODs) were from 0.159 (Sb) to 9.863 (Fe) μg kg−1. Additionally, the developed method received a total score of 85 on the analytical Eco-Scale, indicating an excellent green analysis method. Furthermore, the method was validated by determining 19 elements (Al, As, Ba, Ca, Cd, Co, Cr, Cu, Fe, K, Mg, Mn, Ni, P, Pb, S, Sb, Se, and Zn) in brown and white rice cultivated in South Korea.

Determination of trace metals by ICP-OES in petroleum cokes using a novel microwave assisted digestion method

Trace metals must be strictly controlled in petroleum coke when it is used as anode, as the function of electrodes depends on their concentration, being detrimental in process operations affecting the purity of the final product.In this research, the determination of Si, Fe, V, Ni, Ca, Na, P, Al, Ti, Mg, K, Zn, Mo, Ba, and Co at trace level in green and calcined petroleum cokes using a new digestion method was performed. The method involved microwave-assisted digestion of the sample using a single-reaction chamber (SRC) followed by ICP-OES measurement. This method aimed for a low sample preparation time and a quantitative extraction of the analytes.After optimization of the digestion process it was found that the best condition to digest green and calcined cokes was mixing 9 g HNO3 and 3 g HCl, heating at a temperature of 260 °C for 55 min, and taking 0.5 g of sample, leading to a recovery higher than 98% for all the elements analyzed. In addition, the developed method allowed the determination of the elements in 1.5 h versus the standard method, which takes about 8 h. The validation of the developed methodology was carried out analyzing certified reference materials and using independent methods, such as, wavelength dispersive X-ray fluorescence spectrometry (WD-XRF).The developed methodology is faster, more accurate and more environmentally friendly than other available methodologies as it does not require the decomposition process involving high temperatures and waste generation is minimized. In addition, low limits of quantification and low uncertainties have been reached enabling this method to be used as a control method.

Non-Idealities in Lab-Scale Kinetic Testing: A Theoretical Study of a Modular Temkin Reactor

The Temkin reactor can be applied for industrial relevant catalyst testing with unmodified catalyst particles. It was assumed in the literature that this reactor behaves as a cascade of continuously stirred tank reactors (CSTR). However, this assumption was based only on outlet gas composition or inert residence time distribution measurements. The present work theoretically investigates the catalytic CO2 methanation as a test case on different catalyst geometries, a sphere, and a ring, inside a single Temkin reaction chamber under isothermal conditions. Axial gas-phase species profiles from detailed computational fluid dynamics (CFD) are compared with a CSTR and 1D plug-flow reactor (PFR) model using a sophisticated microkinetic model. In addition, a 1D chemical reactor network (CRN) model was developed, and model parameters were adjusted based on the CFD simulations. Whereas the ideal reactor models overpredict the axial product concentrations, the CRN model results agree well with the CFD simulations, especially under low to medium flow rates. This study shows that complex flow patterns greatly influence species fields inside the Temkin reactor. Although residence time measurements suggest CSTR-like behavior, the reactive flow cannot be described by either a CSTR or PFR model but with the developed CRN model.

Novel Determination of Trace Metals in Geological Materials Employed in Food Products by Microwave Decomposition and Inductively Coupled Plasma – Optical Emission Spectrometry (ICP-OES)

A new methodology for the determination of trace metals in geological materials employed in the food industry by single-reaction chamber (SRC) microwave digestion followed by inductively coupled plasma – optical emission spectrometry (ICP-OES) analysis was developed. The presence of toxic elements for human beings, such as As, Cd, Cr, Hg, Ni, and Pb, must be controlled in those materials that are in contact with food. Most regulations require the presence of these elements in these materials in low concentrations, mostly less than 1 mg kg−1, which requires analytical methodologies that can reach these quantification limits. In the optimization of the sample preparation by microwave digestion, different mixtures of acids were used, so that As, Cd, and Hg were decomposed in an inverse aqua regia solution, while extraction of solid sample with aqua regia and HF was needed to determine Cr, Ni, and Pb. The determination of the analytes present in these solutions was carried out by ICP-OES, optimizing the conditions to obtain the best signal-to-noise ratio for each analyte. The study was undertaken using certified reference materials, two samples of clay, and a sample of sepiolite. Quantification limits of 1 mg kg−1 were achieved, which meet the legal requirements. The analyzed samples of clays and sepiolite contained values of Cd and Hg that met the requirements although the results for As, Cr, Ni, and Pb were above the limits required for the food industry.

Microwave-assisted digestion method using diluted nitric acid and hydrogen peroxide for the determination of major and minor elements in milk samples by ICP-OES and ICP-MS

A novel method for microwave-assisted digestion of milk samples using diluted HNO3and H2O2 with a single reaction chamber was developed for elemental analysis by ICP-based techniques. The optimal conditions for digestion were 0.25 g of sample mass, 6 mL of 0.1 molL−1HNO3and 2 mL of 30% H2O2 at 250 ℃ and 160 bar. The optimized procedure resulted in low residual carbon content and residual acidity of 260 mgL−1 and 0.06 mol L−1, respectively. The limits of detection ranged from 0.286ոg g−1(Ca) to 82.990ոg g−1(Fe). In addition, the proposed method was considered an excellent green analysis method with a final score of 87 based on the analytical Eco-Scale. Finally, the method was validated and applied to the determination of Al, As, Ba, Ca, Cd, Co, Cr, Cu, Fe, Mg, Mn, Ni, Pb, Sb, Se, and Zn in milk samples from South Korea.

Microfluidic Biosensor for Rapid Nucleic Acid Quantitation Based on Hyperspectral Interferometric Amplicon-Complex Analysis.

Nucleic acid detection plays a vital role in both biomedical research and clinical medicine. The temperature circulation changes of the widely used polymerase chain reaction technique are time-consuming and technically challenging for system development. Recombinase polymerase amplification (RPA) is an isothermal method for rapid nucleic acid detection. However, current RPA amplicon detection methods are complicated and expensive and easily generate false positives, restricting the promotion of RPA techniques. In this work, a hyperspectral interferometric amplicon-complex quantitation method is presented, combined with asymmetric dipole complex strategy optical scattering analysis. GelRed dye was utilized to form amplicon-complex particles, and the Fourier domain spectrum computation contributed to complex scattering quantitation. With this method, a supporting microfluidic chip and automatic system were developed to achieve integrated, rapid, quantitative, and miniscule nucleic acid detection. The Plasmodium falciparumdhfr gene was utilized as an example for targeted nucleic acid quantitation and single nucleotide polymorphism detection. The total reaction time was decreased to merely 20 min, and the limit of detection was only 3.17 ng/μL. The minimum measurable concentration of target was 1.68 copies/μL, 31.67 times more sensitive than turbidity detection, and the single reaction chamber was only 9.33 μL. No scattering increase occurred for template-free control, and thus, false positives caused by primer dimers and nonspecific products could be avoided. The experimental results prove that the provided method and system can detect single-base mutations in the dhfr gene and is a reasonable technique for rapid, automatic, and low-cost nucleic acid detection.

Development of a Mushroom Powder Certified Reference Material for Element Analysis

A certified reference material (CRM) for the analysis of nutrient elements in an edible mushroom (Ganoderma lyceum) powder has been developed (KRISS CRM 108-10-011). The mass fractions of calcium (Ca), iron (Fe), and zinc (Zn) were measured by isotope dilution inductively coupled plasma mass spectrometry (ID ICP/MS). To dissolve the fungi cell wall of mushroom consisted of chitin fibers, sample preparation method by single reaction chamber type microwave-assisted acid digestion with acid mixtures was optimized. The mean measurement results obtained from 12 sample bottles were used to assign as the certified values for the CRM and the between-bottle homogeneities were evaluated from the relative standard deviations. The certified values were metrologically traceable to the definition of the kilogram in the International System of Units (SI). This CRM is expected to be used for validation of analytical methods or quality control of measurement results in analytical laboratories when they determine the mass fractions of elements in mushroom or other similar samples.

Development of an eco-friendly sample preparation protocol for metal determination in food samples: an oxygen pressurized single reaction chamber using diluted nitric acid.

Many efforts have been recently made to improve the digestion efficiency by using powerful equipment or by using an auxiliary reagent. In this work, an alternative method is reported, which explores a digestion system based on a single reaction chamber (SRC) technology pressurized with O2 for reducing the amount of acid, without impairing the digestion efficiency. Before digestion, the system was pressurized with compressed air (20 bar, 20% O2) while the temperature was evaluated from 180 up to 270 °C. The procedure was also carried out under O2 pressure (20 bar). For each temperature several acid concentrations were evaluated (0.1 to 3 mol L-1 HNO3), being possible to correlate the effectiveness of each acid concentration with temperature. The proposed method was applied to the simultaneous digestion of several organic matrices with variable content of fat, protein, and carbohydrate (whole milk powder, bovine liver, parsley, and linseed). The residual carbon content was lower than 4% (C lower than 200 mg L-1 in digests), showing the high digestion efficiency of the proposed approach. Up to 250 mg of all food matrices were digested using a sub-stoichiometric amount of HNO3 (1 mol L-1 solution), which was only achieved due to the use of O2 as an auxiliary reagent. Barium, Ca, Cu, Fe, K, Mg, Mn, Na, Sr, and Zn were determined by ICP-OES, and the accuracy was better than 95% for standard reference materials of corn bran, whole milk powder, and bovine liver. It is an important feature, being in agreement with green chemistry recommendations because very low amounts of reagents are required for sample digestion, as well as low amounts of residues are generated.

A novel strategy for medical foods digestion and subsequent elemental determination using inductively coupled plasma optical emission spectrometry

A sample preparation method using only H2O2 in the single reaction chamber system (SRC-H2O2) for medical foods (MFs) digestion and further elemental determination by inductively coupled plasma optical emission spectrometry (ICP OES) was proposed. Digestion of some refractory substances (RS), such as, histidine, linoleic acid, phenylalanine and tryptophan, was also investigated. For the method development important parameters, such as, maximum temperature and pressure of SRC system, volume of H2O2 and sample mass were evaluated. Digestion efficiency was evaluated based on the concentration of residual carbon (RC) of final digests. The optimized method conditions were 1 g of sample, 6 mL of 50% H2O2 and maximum temperature and pressure of 250 °C and 160 bar, respectively. The digests obtained using the optimized conditions presented concentration of RC lower than 720 mg L−1. The accuracy of SRC-H2O2 method was evaluated by analysis of reference material (RM) NIST 8435 (whole milk powder) and by comparison between results obtained using the proposed method and those obtained by digestion with concentrated HNO3 (SRC-HNO3). Significant differences were not observed comparing the results of SRC-H2O2 with reference values of RM and SRC-HNO3. Limits of detection obtained by the proposed method ranged from 0.01 to 88 μg g−1 for all elements determined by ICP OES. SRC-H2O2 method provided digests of individual constituents (sodium caseinate, corn syrup and sunflower oil) of MFs and RS with residual carbon content (RCC) lower than 10% (calculated based on molar and sample masses), except for linoleic acid (RCC of 17%). These same compounds were also digested using SRC-HNO3 method and the RCC values were significantly lower than than those found by SRC-H2O2, except for aromatic amino acids (tryptophan and phenylalanine). The final acidity of digests obtained using SRC-H2O2 was negligible that is convenient for elemental determination using ICP-based techniques and agrees with green analytical chemistry requirements.

Determination of inorganic contaminants in carbon nanotubes by plasma-based techniques: Overcoming the limitations of sample preparation

In this work, sample preparation of carbon nanotubes (CNTs) for further determination of inorganic contaminants was investigated using a microwave-assisted wet digestion single reaction chamber system (MAWD-SRC). Analytes (Al, As, Ca, Cd, Co, Cr, Fe, La, Mg, Mo, Ni, Pb and Zn) were determined in CNTs by inductively coupled plasma optical emission spectrometry (ICP-OES) and inductively coupled plasma mass spectrometry (ICP-MS, except for Al, Ca, Fe and Mg). Method parameters were evaluated, as the mass of CNT (25–300 mg), the temperature (220–270 °C) and the time (35-75 min) of irradiation program. The accuracy was evaluated by using a certified reference material (CRM) of CNT and also by comparison of the results with those obtained using neutron activation analysis (NAA) and high resolution continuum source graphite furnace atomic absorption spectrometry with direct solid sampling (DSS-HR-CS-GF AAS). Quantitative recoveries for all elements were obtained using 275 mg of CNTs, 6 mL of 14.4 mol L−1 HNO3 and 0.5 mL of 30% H2O2 with an irradiation program of 65 min (35 min at 270 °C). No statistical difference was observed between the results obtained after the decomposition of CNTs by MAWD-SRC with those obtained by NAA and DSS-HR-CS-GF AAS. No difference was also observed for the results using the proposed method and the values for the CRM of CNT. The use of MAWD-SRC showed good performance for CNTs digestion using relatively high sample mass (up to 275 mg), contributing to low limits of quantification (LOQs) and overcoming the current limitations of sample preparation. To the best knowledge of the authors, this work reports the highest sample mass feasible to be decomposed using wet digestion for CNTs among the methods proposed in literature.

Microwave-assisted digestion with a single reaction chamber for mineral fertilizer analysis by inductively coupled plasma optical emission spectrometry

ABSTRACTA systematic approach is proposed to evaluate microwave-assisted digestion in a single reaction chamber for the simultaneous determination of elements in the mineral fertilizer and raw material by inductively coupled plasma optical emission spectrometry. A reference material was digested using 12 acid mixtures containing nitric, hydrochloric, orthophosphoric, hydrofluoric or boric acid. Principal components analysis was applied for data treatment. Three digestion procedures based on diluted acids exhibited the most accurate results, with relative errors for reference values ranging from −15% to + 9%. Limits of quantification were in the range of 0.2 mg cadmium kg−1 up to 1000 mg aluminum kg−1.

Combined effects of oscillating hydrostatic pressure, perfusion and encapsulation in a novel bioreactor for enhancing extracellular matrix synthesis by bovine chondrocytes.

The influence of combined shear stress and oscillating hydrostatic pressure (OHP), two forms of physical forces experienced by articular cartilage (AC) in vivo, on chondrogenesis, is investigated in a unique bioreactor system. Our system introduces a single reaction chamber design that does not require transfer of constructs after seeding to a second chamber for applying the mechanical forces, and, as such, biochemical and mechanical stimuli can be applied in combination. The biochemical and mechanical properties of bovine articular chondrocytes encapsulated in agarose scaffolds cultured in our bioreactors for 21 days are compared to cells statically cultured in agarose scaffolds in addition to static micromass and pellet cultures. Our findings indicate that glycosaminoglycan and collagen secretions were enhanced by at least 1.6-fold with scaffold encapsulation, 5.9-fold when adding 0.02Pa of shear stress and 7.6-fold with simultaneous addition of 4MPa of OHP when compared to micromass samples. Furthermore, shear stress and OHP have chondroprotective effects as evidenced by lower mRNA expression of β1 integrin and collagen X to non-detectable levels and an absence of collagen I upregulation asobserved in micromass controls. These collective results are further supported by better mechanical properties as indicated by 1.6-19.8-fold increases in elastic moduli measured by atomic force microscopy.

Green microwave-assisted wet digestion method of carbohydrate-rich foods with hydrogen peroxide using single reaction chamber and further elemental determination using ICP-OES and ICP-MS

A sample preparation method using only H2O2 in the single reaction chamber system (SRC-UltraWave™) was proposed for carbohydrate-rich foods (CRFs) digestion and further elemental determination by inductively coupled plasma (ICP) based techniques. The greenness of the proposed method was evaluated based on the Analytical Eco-Scale. Additionally, the digestion efficiency, obtained under different conditions (temperature and volume of H2O2), was evaluated based on the concentration of residual carbon (RC). Determination of RC and major elements (Ca, Fe, Mg and Na) were carried out using inductively coupled plasma optical emission spectrometry (ICP-OES), while the minor and toxic elements (As, Ba, Cd, Co, Cu, Mn, Mo, Pb, Sr and Zn) were determined by inductively coupled plasma mass spectrometry (ICP-MS). Digests with lower RC were obtained using 8mL of 50% H2O2, 250°C and 199bar. Residual carbon lower than 250 and 400mgL−1 were obtained for honey and different flours (wheat, corn, cassava and potato), respectively. Maxima sample masses of 0.75g and 1.25g were efficiently digested (without insoluble residues) for different flours and honey, respectively. Reference materials (RMs) and certified reference material (CRM) with carbohydrate-rich matrices: corn bran (RM NIST 8433), cotton cellulose (RM IAEA V9) and rice flour (CRM NIST 1568a) were used to evaluate the accuracy of the proposed method. Additionally, accuracy was also evaluated by comparison between results obtained using proposed method and those obtained by microwave-assisted wet digestion (MAWD) with concentrated HNO3. Significant differences were not observed when comparing the results of the proposed method with reference values of RMs, CRM and MAWD. Limits of detection obtained by the proposed method were suitable for the quality control analysis of CRFs and ranging from 0.0001μgg−1 to 30μgg−1. As water and oxygen are the main products of H2O2 with CRFs, final digests are suitable for ICP-based techniques analysis due to its low acidity and consequent reduction of physical interferences on nebulization devices. Finally, according to the Analytical Eco-Scale, the proposed method was considered an excellent green analysis with final score of 85.

A new sample preparation method for crude or fuel oils by mineralization utilizing single reaction chamber microwave for broader multi-element analysis by ICP techniques

The objective of this study was to develop an effective and routine single sample preparation method to accurately and precisely analyze multiple elements (up to 57) in crude oils using both an inductively coupled plasma-optical emission spectrometer (ICP-OES) for high abundance elements and a triple quadrupole-inductively coupled plasma-mass spectrometer (QQQ-ICP-MS) (or ICP-MS) for low abundance trace and ultra-trace elements. A critical aspect of this study was to develop a single sample preparation method that could be effective in analyzing the largest number of quantifiable elements with instruments used in tandem to cover a wider and more practical combined dynamic range. Three sample preparation techniques were investigated and tested, including high pressure combustion with strong-acid digestion, high pressure and high temperature strong-acid digestion within Parr bombs, and high temperature and high pressure digestions in a Single Reaction Chamber (SRC) microwave. For the combustion method, no element showed recovery above 75%, thus this method was deemed unacceptable for accurate and precise analysis of crude oil. Average recoveries ranging from 94% to 106% for 19 analytes were achieved with high pressure and high temperature acid digestion within Parr bombs. A drawback of the method, however, was a rather small sample sizes (100mg) that could be achieved without venting, which places limitations on detection and quantitation limits of large numbers of low abundance analytes in natural crude oils. The best of the SRC microwave-assisted acid digestion tests, however, was also shown to be acceptable for 19 analytes using a certified organometallic standard, with average recoveries ranging from 93% to 113%. Because of rapid sample throughput and the larger sample sizes (1.2g sample size per digestion session) that can be accommodated with the single reaction chamber microwave digestion technique, better method detection and quantification limits and high precision on a range of low abundance elements could be achieved. We also then successfully tested the recovery of 53 elements with this SRC microwave method by adding a multi-element spike to Conostan base oil. This optimum SRC digestion method tested was then used to examine a NIST natural crude oil research material (NIST RM 8505) in an attempt to quantify up to 57 elements. The mean vanadium concentration (mass fraction) is reported as 390±0.4µg/g, the mean value of 5 replicate digestions by our method, which agrees well with the recommended value for the only element recommended for NIST 8505 of 390±10µg/g. The number of quantified analytes for the RM 8505 was further extended to a total of 52 elements with RSDs <5% for 38 elements, between 5% and 10% for 10 elements, and between 10% and 15.6% for 4 elements, all of which met our acceptability limits set at ≤20% RSD. Of the 57 elements analyzed in RM 8505, certain elements B, Nb, and W, although above method quantitation limits, were judged unacceptable because RSDs were ≥31.4%, whereas Ag and Tl were below method quantitation limits, and their RSDs were ≥44.2% and judged unacceptable. However, these elements have been quantified in other natural crude oils with higher abundances, which indicates that up to 57 elements can be potentially assessed in crude oils or refined oils with this method. The NIST RM 8505 crude oil reported here and others are being evaluated as potential natural crude oil standards to provide references values for more routine multi-element analysis.

High purity polyimide analysis by solid sampling graphite furnace atomic absorption spectrometry

In this work, Cr, Cu, Mn, Na and Ni were determined in high purity polyimides (99.5%) by solid sampling graphite furnace atomic absorption spectrometry (SS-GFAAS) using Zeeman effect background correction system with variable magnetic field, making possible the simultaneous measurement at high or low sensitivity. The following analytical parameters were evaluated: pyrolysis and atomization temperatures, feasibility of calibration with aqueous solution, linear calibration range, sample mass range and the use of chemical modifier. Calibration with aqueous standard solutions was feasible for all analytes. No under or overestimated results were observed and up to 10mg sample could be introduced on the platform for the determination of Cr, Cu, Mn, Na and Ni. The relative standard deviation ranged from 3 to 20%. The limits of detection (LODs) achieved using the high sensitivity mode were as low as 7.0, 2.5, 1.7, 17 and 0.12ngg−1 for Cr, Cu, Mn, Na and Ni, respectively. No addition of chemical modifier was necessary, except for Mn determination where Pd was required. The accuracy was evaluated by analyte spike and by comparison of the results with those obtained by inductively coupled plasma optical emission spectrometry and inductively coupled plasma mass spectrometry after microwave-assisted digestion in a single reaction chamber system and also by neutron activation analysis. No difference among the results obtained by SS-GFAAS and those obtained by alternative analytical methods using independent techniques. SS-GFAAS method showed some advantages, such as the determination of metallic contaminants in high purity polyimides with practically no sample preparation, very low LODs, calibration with aqueous standards and determination in a wide range of concentration.