Ng Cm-3 Research Articles

Chemical Emissions from Cured and Uncured 3D-Printed Ventilator Patient Circuit Medical Parts.

Medical shortages during the COVID-19 pandemic saw numerous efforts to 3D print personal protective equipment and treatment supplies. There is, however, little research on the potential biocompatibility of 3D-printed parts using typical polymeric resins as pertaining to volatile organic compounds (VOCs), which have specific relevance for respiratory circuit equipment. Here, we measured VOCs emitted from freshly printed stereolithography (SLA) replacement medical parts using proton transfer reaction mass spectrometry and infrared differential absorption spectroscopy, and particulates using a scanning mobility particle sizer. We observed emission factors for individual VOCs ranging from ∼0.001 to ∼10 ng cm–3 min–1. Emissions were heavily dependent on postprint curing and mildly dependent on the type of SLA resin. Curing reduced the emission of all observed chemicals, and no compounds exceeded the recommended dose of 360 μg/d. VOC emissions steadily decreased for all parts over time, with an average e-folding time scale (time to decrease to 1/e of the starting value) of 2.6 ± 0.9 h.

Analytical application of the reaction system disulphonated hydroquinone-hydrogen peroxide for the kinetic spectrophotometric determination of iron traces in acidic media

A simple, rapid, sensitive and selective kinetic spectrophotometric method for determination of Fe(III) traces was elaborated in this paper. It is based on the catalytic effect of Fe(III) ions on oxidation of potassium salt of disulphonated hydroquinone (K2S2Hy) by hydrogen peroxide in acidic media, at a constant ionic strength. At the working temperature of 20?C and the wavelength of 450.0 nm, optimal conditions for determination of iron were found so that iron (III) can be determined by the proposed method in the concentration range of 1.87 to 18.7 ng cm-3. Corresponding RSD values were determined to be in the range 4.22 to 10.33 %. The limit of detection (LOD) calculated in two ways was found to be 1.07 ng cm-3 i.e. 1.11 ng cm-3 Fe(III). In order to assess the selectivity of the method effects of different ions on the reaction rate were also determined. It was found that presence of oxalates and citrates in the w/w ratio to Fe(III) 1:1 under selected experimental conditions interferes with determination of iron. Then the method was applied for determination of Fe(III) traces in white radish juice. The results agreed well with those obtained by atomic absorption spectrometry.

Distribution of Mercury Concentrations in Tree Rings and Surface Soils Adjacent to a Phosphate Fertilizer Plant in Southern Korea.

This study aimed to determine mercury concentrations in tree rings and surface soils at distances of 4, 26 and 40km from a fertilizer plant located in Yeosu City, Korea. Mercury concentrations in all tree rings were low prior to the establishment of the plant in 1977 and became elevated thereafter. The highest average mercury concentration in the tree rings was 11.96ngg-1 at the Yeosu site located nearest to the plant, with the lowest average mercury concentration of 4.45ngg-1 at the Suncheon site furthest away from the plant. In addition, the highest mercury content in the surface soil was 108.51ng cm-3 at the Yeosu site, whereas the lowest mercury content in the surface soil was 31.47ng cm-3 at the Suncheon site. The mercury levels decreased gradually with increasing distance from the plant.

A novel carbon paste electrode based on nitrogen-doped hydrothermal carbon for electrochemical determination of carbendazim

In this work, a new carbon paste electrode, prepared from nitrogen- -doped hydrothermal carbon (CHTCN) was applied for the electrochemical detection and determination of carbendazim fungicide. CHTCN samples with the nominal nitrogen content 0.05?0.5 wt. % in glucose precursor were prepared by simple, low-cost synthesis with the accompanying carbonization to 1273 K. The presence of nitrogen in CHTCN samples was confirmed by elemental analysis. Characterization of CHTCN as material for carbon paste electrode was achieved by cyclic voltammetry measurement of the Fe(CN)6 3-/4- redox couple. The results showed that best electrochemical response was obtained from the sample with a nominal nitrogen concentration of 0.1 wt. % and with tricresyl phosphate as a binder. During the development of a differential pulse stripping voltammetric method for carbendazim determination applying new electrode, the following experimental parameters were studied: the sort and amount of binding liquid, the effect of pH, accumulation potential and accumulation time. Under optimal conditions, the electrode offered linearity in the wide concentration range from 25 to 490 ng cm-3 and an estimated detection limit of 1.21 ng cm-3. Moreover, the electrode showed good stability, high selectivity and satisfactory anti-interference ability. Finally, the developed method was successfully applied for the determination of carbendazim traces in spiked tap and river water samples.

Optimization of inductively coupled plasma mass spectrometer parameter’s to measuring arsenic and selenium

In the last decades an increased interest has been evolved about arsenic and selenium. The aim is to understand the environmental, agricultural and biological role of the these elements. In case of arsenic the mayor reasons are the relatively high concentration of arsenic in marine biota (mg kg-1) and the arsenic contaminated drinking waterbases of some Asian countries besides Hungary. The toxicity of higher level selenium content is also known, nevertheless selenium is essential for some biological functions. Considering its esssentiality, in our country the insufficient selenium intake rate couse lack of selenium. Measuring the concentrations of these elements are cruital but not satisfactory information, but the speciation, that is the form of an element presented in a sample is also required. In both cases the most suitable method to determine concentration is the inductively coupled plasma mass spectrimetry. My objective was to optimase the changeable parameters of the ICP-MS for reaching the lowest (the best) detection limit. For this porpuse I have investigated the effect of parameter change on nett signal intensity and relative signal intensity. With the optimased parameter settings the limit of detection for arsenic and selenium were determined, which are 0,032 ng cm-3 for arsenic, and 0,097 ng cm-3 forselenium.

Kinetic spectrophotometric determination of Bi(III) based on its catalytic effect on the oxidation of phenylfluorone by hydrogen peroxide

A new reaction was suggested and a new kinetic method was elaborated for determination of Bi(III) in solution, based on its catalytic effect on the oxidation of phenyl-fluorone (PF) by hydrogen peroxide in ammonia buffer. By application of spectrophotometric technique, a limit of quantification (LQ) of 128 ng cm-3 was reached, and the limit of detection (LD) of 37 ng cm-3 was obtained, where LQ was defined as the ratio signal: noise = 10:1 and LD was defined as signal 3:1 against the blank. The RSD value was found to be in the range 2.8-4.8 % for the investigated concentration range of Bi(III). The influence of some ions upon the reaction rate was tested. The method was confirmed by determining Bi(III) in a stomach ulcer drug ('Bicit HP', Hemofarm A.D.). The obtained results were compared to those obtained by AAS and good agreement of results was obtained.

Rapid Spectrophotometric Determination of Trace Amounts of Nitrate‐Nitrogen Using Dapsone and α‐Naphthol

A simple, rapid and sensitive spectrophotometric method has been developed for the trace determination of nitrite using Dapsone and α‐Naphthol. The proposed method is based on the diazotization of Dapsone followed by coupling with α‐Naphthol in sodium hydroxide medium to give an intense pink coloured azo dye. The dye shows absorption maximum at 540 nm. The molar absorptivity and Sandell’s sensitivity being 5.749 × 104 l mol-1 cm-1 and 0.24 ng cm-3 respectively. Tolerance limit for interfering ions and complexing agents were reported. Other analytical parameters and applications of the method for analysis of tap water, lake water, and industrial effluents have been investigated.

Determination of Manganese in Some Medicinal Plants and Their Infusions by a Catalytic Spectrophotometric Method

The catalytic effect of manganese (II) on the oxidation of the azo dye 3-Methyl-6-(2-hydroxyethoxy)-2-[2-methoxy-4-N (N, N diethylamino) phenylazo] benzothiazolium methylsulphate, with potassium periodate in the presence of 1,10-phenanthroline in weakly acidic media was studied. The reaction was followed spectrophotometrically by measuring the decrease in the absorbance of the dye at 560 nm. Under the optimum conditions (4 x 10(-5) mol dm(-3) azo dye, 4 x 10(-4) mol dm(-3) potassium periodate, 1 x 10(-4) mol dm(-3) 1,10-phenanthroline, 0.1 mol dm(-3) buffer--pH 3.0, 70 degrees C, 8 min) manganese (II) in the range 0.1-5 ng cm(-3) could be determined by the fixed-time method with a detection limit of 0.035 ng cm(-3). The developed method is highly sensitive, selective, and simple. The method was applied successfully to the determination of total manganese in some medicinal plants and to analyse their infusions for trace amounts of total manganese and free manganese (II) ions without separation.

Kinetic determination of morin nanoamounts

kinetic-spectrophotometric method is proposed for the determination of morin. The method is based on the inhibition effect of morin on the oxidation of C6H5COON aby hydrogen peroxide in the presence of the complex Fe(II)-AA(ascorbic acid),which acts as a catalyst. The concentration range for the determination of morin is one of the lowest achieved so far (a linear calibration graph was obtained for morin from 2.255?22.55 ng cm-3). The limit of detection of the method is 0.28 ng cm-3. The relative error ranges between 1.42 to 5.10% for the given concentration interval. Kinetic equations are proposed for the investigated process. The effects of certain foreign ions upon the reaction rate were determined in order to assess the selectivity of the method. The major advantages of this kinetic-spectrophotometric assay are its sensitivity, selectivity, reproducibility, speed and simplicity.

Preliminary Investigations of High-Frequency Atmospheric-Pressure Plasma Jet for Atomic Emission Spectrometry

The 27.12- and 13.56-MHz plasma-jet discharges are generated in argon at atmospheric pressure. The plasma originates inside the nozzle of the bored metal power electrode and outflows against the counter-electrode. The discharge has a column shape with the diameter about 0.7-1.5 mm and the length 5-30 mm. The 27.12 MHz/100 W and 13.56 MHz/1 500 W generators are operated at a power of 100 and 200 W, respectively. Stable discharges are obtained within the range from 0.3 to 0.9 dm3 min-1 Ar. The 27.12 MHz/100 W discharge is capable of accepting dry aerosol while the wet aerosol extinguishes this plasma. On the contrary, wet aerosol can be introduced into the 13.56 MHz/200 W plasma. The vibrational temperature of 3 000 K has been determined based on the intensity of the molecular band of the N2 2nd positive system (365-383 nm) in the 27.12 MHz discharge. Intensity vs concentration dependences have been measured with Li 670.784, Na 588.995, Na 589.592, K 766.491 and Rb 780.023 nm lines. Limits of detection in the 27.12 MHz/100 W discharge coupled to an ultrasonic nebulizer with desolvation are 0.1 Li, 30 Na, 10 K and 3 ng cm-3 Rb. Limits of detection in the 13.56 MHz/200 W discharge connected to a pneumatic concentric Meinhard nebulizer is 8 ng cm-3 Li.

Hydroxypropyl-beta-cyclodextrin enhanced fluorimetric method for the determination of melatonin and 5-methoxytryptamine.

The effects of native cyclodextrins (alpha, beta or gamma), hydroxypropyl-beta-cyclodextrin, beta-cyclodextrin solubilized in urea, soluble starch and glucose in water solution on the fluorescence behaviour of melatonin (N-acetyl-5-methoxytryptamine) (M) and 5-methoxytryptamine [5-methoxy-3-(2-aminoethyl)indole] (5M) were determined. In addition, the effect of methanol and propanol with and without beta-cyclodextrin or hydroxypropyl-beta-cyclodextrin was assessed. From the fluorescence changes with pH, the values of the pKa for the ground (9.9 +/- 0.2) and the excited state (7.7 +/- 0.2) for 5M were determined. From the fluorescence changes with beta-cyclodextrin or hydroxypropyl-beta-cyclodextrin, the association constants of M, 5MH [5-methoxy-3-(2-ammoniumethyl)indole] and 5M with the two hosts were determined. The values with beta-cyclodextrin were KAssoc5MH = (1.4 +/- 0.4) x 10(2) mol-1 dm3, KAssoc5M = (1.6 +/- 0.1) x 10(2) mol-1 dm3 and KAssocM = (1.1 +/- 0.2) x 10(2) mol-1 dm3, and with hydroxypropyl-beta-cyclodextrin KAssoc5MH = (1.1 +/- 0.3) x 10(2) mol-1 dm3, KAssoc5M = (2.5 +/- 0.1) x 10(2) mol-1 dm3 and KAssocM = (1.51 +/- 0.07) x 10(2) mol-1 dm3. The ratios of the fluorescence quantum yields for the bound and free substrate (phi b/phi f) were in the range 1.15-1.48. The detection limits under the optimum conditions were 0.381 +/- 0.001 ng cm-3 for the complex 5MH-hydroxypropyl-beta-cyclodextrin in water and 0.290 +/- 0.001 ng cm-3 for the complex M-hydroxypropyl-beta-cyclodextrin in water with 5% of methanol. The recovery of melatonin from pharmaceutical preparations was 98-103% with an RSD of 2%. The recovery from rat pineals was also good. The method is direct, simple and accurate.

Flow-Injection Determination of Copper(II) Based on Its Catalytic Effect on the Oxidative Coupling of 3-Methyl-2-benzothiazolinone Hydrazone with N-Ethyl-N-(2-hydroxy-3-sulfopropyl)-3,5-dimethoxyaniline in a Micellar Medium

A highly sensitive flow-injection spectrophotometric method has been developed for the determination of copper(II). It is based on the catalytic effect of copper(II) on the oxidative coupling reaction of 3-methyl-2-benzothiazolinone hydrazone with N-ethyl-N-(2-hydroxy-3-sulfopropyl)-3,5-dimethoxyaniline to form a red compound (λmax=525 nm) in the presence of hydrogen peroxide and pyridine as an activator. A higher sensitivity and sampling rate were achieved by adding ben-zyldimethyltetradecylammonium chloride (Zephiramine) as a surfactant to this reaction system. The calibration graph for copper(II) was linear over the range 0.005 - 0.75 ng cm-3 at a rate of 40 samples h-1. The relative standard deviations for ten determinations of 0.5 and 0.05 ng cm-3 were 0.21 and 2.0%, respectively. The proposed method was successfully applied to the determination of copper in pepperbush.

Simultaneous determination of dimethylarsinic acid and monomethylarsonic acid after derivatization with thioglycol methylate by gas chromatography/mass spectrometry.

A gas chromatography/mass spectrometry (GC/MS) method has been developed to determine two methylated arsenic species in human urine samples. The yield of derivatization for dimethylarsinic acid (DMA) and monomethylarsonic acid (MMA) using thioglycol methylate (TGM) was measured. The detection limit for the derivatized DMA and MMA using the GC/MS method are 0.95 and 0.8 ng cm-3, respectively. This simple and rapid method has good precision and accuracy. Fragmentation routes of derivatized MMA and DMA are suggested on accurate mass measurements.

Nephelometric determination of micro amounts of nucleic acids with protamine sulfate.

Nucleic acids can form large particle complexes with protamine sulfate by electrostatic forces, which results in strong light scattering. Based on this, a nephelometric method is described for sensitive and convenient determination of nucleic acids with protamine sulfate by using a common spectrofluorimeter. Maximum light scattering is produced in the range of pH 2.2-4.4 with the same excitation and emission wavelengths at 365 nm. Under optimal conditions, the calibration curves are linear in the range 0.05-60.0 micrograms cm-3 for nucleic acids. The corresponding detection limits are 12.5 ng cm-3 for calf thymus DNA, 9.0 ng cm-3 for fish sperm DNA, and 18.0 ng cm-3 for yeast RNA, respectively. Six synthetic samples are determined with satisfactory results. The relative standard deviation of five replicate measurements is 3.2% for 2.0 micrograms cm-3 calf thymus DNA.

Speciation of trace amounts of aluminium in environmental samples by cation-exchange FPLC - ETAAS

Cation-exchange fast protein liquid chromatography - electrothermal atomic absorption spectrometry (FPLC - ETAAS) was applied for the speciation of trace amounts of aluminium. An aqueous 8 mol dm -3 NH4NO3 linear gradient elution in 10 min- utes enabled separation of positively charged monomeric aluminium species in aqueous solution. Separated aluminium species were collected in 0.5 cm3 fractions and aluminium determined off line after fourfold dilution by ETAAS. The ability of NH 4NO3 to completely decompose at low temperature in the graphite tube during the ashing step enabled quantitative and reproducible determination of aluminium. After applying Chelex-100 resin in a cleaning procedure of the eluent, the eluent blank was very low (< 1.0 ng cm-3 Al). When 1 cm3 of sample was injected on the column resin, the limit of detection (3 s) for the separated aluminium species determined by ETAAS was found to be 3 ng cm-3. Good repeatability of measurement of separated aluminium species (relative standard deviation ∠5%) was obtained under the recommended analytical conditions. The influence of some inor- ganic and organic complexing ligands at pH values of 4.0 and 6.0 on the speciation of aluminium was also investigated. The method developed was successfully applied for the speciation of aluminium in soil extracts and natural water samples at ng cm -3 levels.

Cathodic Stripping Voltammetry of Tellurium(IV) at a Rotating Silver Disk Electrode.

A simple and reproducible method is described for the determination of traces of tellurium(IV) based on differential pulse cathodic stripping voltammetry without the addition of any other metal ions to an acidic medium. Tellurium(IV) ions in a 0.18 mol dm-3 hydrochloric acid-0.20 mol dm-3 nitric acid solution (4 cm3) were electrodeposited on a rotating silver disk electrode (2000 rpm) as silver telluride at -0.45 V vs. Ag/AgCl for 30 min. A cathodic stripping voltammogram was then recorded in an another solution (2 mol dm-3 sodium hydroxide) at a scan rate of 50 mV s_1 to -1.5 V vs. Ag/AgCl. Only a single well-defined peak could be seen at -1.16 V vs. Ag/AgCl. The calibration curve was linear up to at least 300 ng cm-3 of tellurium(IV) (2.4×10-6 mol dm-3) and passed through the origin with an RSD of 6.8% for 50 ng cm-3 (n=5). The detection limit (3σ) was 0.62 ng cm-3. The possible interferences were evaluated.

Speciation of Aluminium in Environmental Water Samples Employing Microcolumn Chelating Ion-Exchange Chromatography - ETAAS

A microcolumn chelating ion-exchange chromatography-electrothermal atomic absorption spectrometry procedure (ETAAS) was developed for aluminium speciation at the nanogram per millilitre level in water samples from the environment. Chelex-100 resin (100-200 mesh, H+ form) was filled into a micro column and connected to a peristaltic pump. Before analysis, the resin column was equilibrated to the pH of the particular sample analyzed. Sample was then pumped through the column at a flow rate of 0.5 cm3 min−1. Labile aluminium monomeric species were retained by the resin column and, after elution with 5 cm3 of HCl (1 mol dm−3), determined by ETAAS. At pH higher than 5.0, prewashing with 0.025 mol dm−3 HCl was applied prior to elution with 1 mol dm−3 HCl, to remove Al(OH)3 adsorbed on the column resin. The distribution of aluminium species over a pH range from 3.0 to 8.0 in synthetic standard solutions was closely matched by the 8-hydroxyquinoline spectrophotometric method and reported calculated data. Good reproducibility of measurement (± 1.5%) was obtained (10 ng cm−3 of Al, pH 4.0). LOD (3[sgrave]) for separated aluminium species (50 cm3 of sample) was found to be 0.3 ng cm3. The influence of some inorganic and organic complexing ligands as well as the effect of high salinity, nonionic surfactants and an excess of alkaline-earth ions on aluminium speciation was investigated. The technique was successfully employed in determination of aluminium species in various water samples from the environment.

Application of a novel fluorescence probe in the determination of nucleic acids.

A novel fluorimetric method has been developed for rapid determination of DNA and RNA with hypocrellin A (HA) as a fluorescence probe, based on the fluorescence enhancement of HA in the presence of DNA or RNA. Maximum fluorescence is produced in the pH range 3.4-4.0, with maximum excitation and emission wavelengths at 470 and 600 nm, respectively. Under optimal conditions, the calibration graphs are linear over the range 0-200.0 ng cm-3 for calf thymus DNA and 13.0-200.0 ng cm-3 for yeast RNA, respectively. The corresponding detection limits are 5.0 ng cm-3 for calf thymus DNA and 13.0 ng cm-3 for yeast RNA. The relative standard deviation of six replicate measurements is 4.5% for 100 ng cm-3 calf thymus DNA. DNA could be determined in the presence of 20% m/m yeast RNA. The mechanism for the binding of HA to DNA is also studied.

Dissolution amounts of nickel, chromium and iron from SUS 304, 316 and 444 stainless steels in sodium chloride solutions

The release of nickel and chromium from stainless steels by sweat, is often responsible for allergic contact dermatitis. The amounts of metal released from stainless steels were in trace amounts, because corrosion resistance was excellent. However, measurement of dissolution amounts is difficult, and if these amounts are not known, the improvement and development of stainless steels with excellent resistance to NaCl solution is difficult. In this work, trace dissolution amounts from the main components of stainless steels which can cause an allergy were investigated. SUS 304, 316 and 444 stainless steels were used in this test. The test solutions used were 0.9 (isotonic sodium chloride solution), 1, 3, 5 and 10 wt% NaCl solutions. Nickel,chromium and iron ions in the test solutions were rapidly determined by stripping voltammetry. The detection limits of Ni(II), Cr(VI) and Fe(III) ions in 1 wt% NaCl solution were 1.0, 0.1 and 0.5 ng cm-3, respectively, with standard deviations of five tests at 5 ng cm-3 Ni(II), Cr(VI) and Fe(III) ions, of 6.4%, 1.8% and 2.2%, respectively. Generally, the amounts of the metals dissolved increased in direct proportion to the immersion, in the range 30–60 days for nickel, 30–90 days for chromium and 30–120 days for iron. The dissolution amounts of nickel from SUS 304 and 316 stainless steels increased rapidly over 60 days, while that of chromium increased rapidly over 90 days, in isotonic sodium chloride solution. The ratio of the three dissolved metal ions was not consistent with the composition of the specimens. The ratio of dissolved nickel in SUS 304 and 316 stainless steels was larger than that in the specimen, and dissolved preferentially. The dissolution ratio of chromium and iron in SUS 444 stainless steel approximately agreed with the composition of the specimen.

Vitreous laser absorption following fluorescein angiography in diabetic patients.

Sodium fluorescein staining of the vitreous following fluorescein angiography may interact with laser photocoagulation. We evaluated the laser absorption by fluorescein in the vitreous when photocoagulation is performed following fluorescein angiography in 15 eyes of nine diabetic patients. Axial fluorescein concentration in the vitreous was measured by a scanning vitreal fluorophotometer. The amount of light absorbed by the fluorescein within the vitreous was calculated according to the Lambert-Beer law. The mean fluorescein concentration ranged from 2.93 ng cm-3 to 105.16 ng cm-3 at 1 h after injection of fluorescein and from 8.03 to 188.56 ng cm-3 after 4 h. Maximum laser absorption at 488 nm ranged from 6.79% (after 1 h) to 14.53% (after 4 h); at 514.5 nm it ranged from 0.96% to 2.14%; at 532 nm it ranged from 0.03% to 0.07%. At lambda > 550 nm, laser absorption was found to be negligible. In order to optimize the effect of photocoagulation, especially during long photocoagulation sessions, argon blue laser (488 nm) should be avoided following fluorescein angiography. Argon green laser (514.5 nm) should be used within 1 h after fluorescein injection. Frequency-doubled Nd:YAG laser (532 nm), krypton laser (647 nm) or semiconductor diode laser (810 nm) may be used at any time.