High-resolution Continuum Source Atomic Absorption Research Articles

Speciation of Chromium in Water Samples after Dispersive Liquid-Liquid Microextraction, and Detection by Means of High-Resolution Continuum Source Atomic Absorption Spectrometry

A newly analytical method has been developed to determine total chromium and speciation of this element in water samples through dispersive liquid-liquid microextraction combined with a high-resolution continuum source flame atomic absorption spectrometry. The most significant variables affecting complexation and extraction were optimized by using response surface methodology and univariate optimization. The best conditions for both the complexation and extraction elements in this study were: complexing agent ammonium pyrrolidine dithiocarbamate (APDC 6.0 mmol L-1); pH at 2.0 (CrVI) and at 7.0 (Cr total); NaCl (5% m/v); 1-undecanol (50 µL) and ethanol 300 (CrIV) and 275 µL (total Cr). Under optimal conditions, this method resulted in a 20-100 µg L-1 linear range for CrVI and total chromium, detection limits of 0.35 (CrVI) and 6.7 µg L-1 (total Cr), as well as enriching factor of 26 (CrVI) and 19 for total Cr. The method accuracy was carried out by using certified water reference material (NIST CRM 1643e), and the results achieved were in agreement with the certified value (t-test at a confidence interval of 95%). The method developed was applied in samples of mineral water, tap water (the recovery values ranged from 88 to 115%) and seawater.

Simultaneous determination of cobalt and nickel in vitamin B12 samples using high-resolution continuum source atomic absorption spectrometry

Nickel and cobalt were simultaneously assayed in vitamin B12 formulations by using atomic spectrometry. The proposed method is based on a compromise between the proximity of specific Ni and Co spectral lines and the relative abundances of the analytes in the samples. The analytes were found in concentrations ranging from 9.48 to 26.20µgL−1 (Ni) and from 156.90 to 279.25mgL−1 (Co) in the commercial samples of vitamin B12. The limits of detection and quantification were 1.21 and 3.64mgL−1 for Co and 0.39 and 1.19µgL−1 for Ni. Sample cleanup was not necessary for the determinations, and the interferences were discussed.

Direct solid analysis for the determination of Mn, Ni, Rb and Sr in powdered stimulant plants using high-resolution continuum source atomic absorption spectrometry followed by chemometric classification based on elemental composition, polyphenol content and antioxidant activity

In this work, a simple, fast and sensitive method for the determination of Mn, Ni, Rb and Sr in powdered samples of guarana (Paullinia cupana), catuaba (Anemopaegmaglaucum), ginseng (Panax ginseng), ginger (Zingiber officinalis), mate (Ilex paraguariensis) and coffee (Coffea arabica) was developed using direct solid sample analysis and high-resolution continuum source electrothermal atomic absorption spectrometry. The temperature program of the graphite furnace was optimized and the determination was carried out without the use of chemical modifiers. Calibration against a solid reference material was compared to calibration against aqueous standards and no significant differences were observed for Mn, Rb and Sr determination, whereas for Ni the difference in sensitivity was as high as 20%, indicating that calibration using a solid reference material should be adopted. Sixteen samples of stimulant plants from a local market were analyzed for trace elements, total phenolic compounds and antioxidant activity. Trace elemental content ranged from 0.08μgg−1(Ni) to 135μgg−1 (Mn), total phenolics ranged from 3.37±0.02 to 34.28±0.04mgGAEg−1, and antioxidant activity ranged from 1.15±0.65 to 10.32±0.21TEmmolg−1. In order to carry out chemometric classification of the plant species, PCA was employed using data from elemental and phenolics contents of the plants, as well as their antioxidant activities. The joint use of these parameters allowed successful distinction between species, showing that these data can be used to discriminate between different stimulant plants.

DETERMINATION OF PALLADIUM IN HYDROGENATION CATALYSTS BY HR-CS FAAS METHOD

Present paper deals with analytical control of hydrogenation supported catalysts (Pd/AC) composition using high-resolution continuum source atomic absorption spectrometry with flame atomization (HR-CS FAAS). Catalysts were prepared with expected 3 wt. % Pd content by the simple technique of deposition – reduction of palladium in a basic environment. Formaldehyde was applied as the reduction agent. The working conditions (gas flow and burner height) for determination of the catalytically active component in the prepared Pd/AC catalysts were found. Prior to the analysis by HR-CS FAAS method Pd/AC was subjected to microwave (MW) assisted digestion in the environment of strong oxidizing acids. Appropriate digestion time of 15 min and temperature of 200 °C had been also experimentally obtained.

High-Resolution Continuum Source Atomic Absorption Spectrometry with Microwave-Assisted Extraction for the Determination of Metals in Vegetable Sprouts

The goal of this study was to investigate the enrichment of garden cress (Lepidium sativum), mung beans (Vigna radiata), and soybeans (Glycine max) with minerals. Hydroponic nutrient solutions were enriched with Zn2+,Cr3+, Ca2+, Mg2+, and Se2+. Morphological assessment was based on monitoring changes that occurred as a function of the concentrations of elements in the medium. The growth of the plant, as a result of a stimulating or inhibitory effect of the identity and concentration of elements on the germination process, was characterized. Microbiological contamination was identified and catabolic profiles of two bacterial strains were performed. High-resolution continuum source atomic absorption spectrometry (HR-AAS) was used to determine Zn2+, Cr3+, Ca2+, Mg2+, and Se2+ in dried plant material after sample pretreatment using microwave-assisted extraction. The limits of detection were 0.010, 0.029, 0.013, 0.151, and 0.030 milligram per liter for Ca2+, Cr3+, Mg2+, Se2+, and Zn2+, respectively. Recoveries were higher than 98 percent and the relative standard deviation was less than 5 percent. The accuracy of the procedure was estimated by analyzing certified reference materials. The results showed that biofortification of garden cress by zinc holds the highest promise for the creation of designer foods. Garden cress was found to have the highest bioconcentration factor among the investigated plants; at 50 parts per million, plant growth was stimulated without contamination by microorganisms.

Multivariate optimization of ultrasound-assisted extraction for determination of Cu, Fe, Ni and Zn in vegetable oils by high-resolution continuum source atomic absorption spectrometry

An assisted liquid–liquid extraction of copper, iron, nickel and zinc from vegetable oil samples with subsequent determination by high-resolution continuum source flame atomic absorption spectrometry (HR-CS FAAS) was optimized by applying a full factorial design in two levels and the response surface methodology, Box–Behnken. The effects of the acid concentration and the amplitude, cycle and time of sonication on the extraction of the analytes, as well as their interactions, were assessed. In the selected condition (sonication amplitude=66%, sonication time=79s, sonication cycle=74%), using 0.5molL−1 HCl as the extractant, the limits of quantification were 0.14, 0.20, 0.21 and 0.04μgg−1 for Cu, Fe, Ni and Zn, respectively, with R.S.D. ranging from 1.4% to 3.6%. The proposed method was applied for the determination of the analytes in soybean, canola and sunflower oils.

Human biomonitoring of aluminium after a single, controlled manual metal arc inert gas welding process of an aluminium-containing worksheet in nonwelders.

Several existing field studies evaluate aluminium welding works but no thoroughly controlled exposure scenario for welding fume has been described yet. This study provides information about the uptake and elimination of aluminium from welding fumes under controlled conditions. In the Aachen Workplace Simulation Laboratory, we are able to generate welding fumes of a defined particle mass concentration. We exposed 12, until then occupationally unexposed participants with aluminium-containing welding fumes of a metal inert gas (MIG) welding process of a total dust mass concentration of 2.5 mg/m(3) for 6 h. Room air filter samples were collected, and the aluminium concentration in air derived. Urine and plasma samples were collected directly before and after the 6-h lasting exposure, as well as after 1 and 7 days. Human biomonitoring methods were used to determine the aluminium content of the samples with high-resolution continuum source atomic absorption spectrometry. Urinary aluminium concentrations showed significant changes after exposure compared to preexposure levels (mean t(1) (0 h) 13.5 µg/L; mean t(2) (6 h) 23.5 µg/L). Plasma results showed the same pattern but pre-post comparison did not reach significance. We were able to detect a significant increase of the internal aluminium burden of a single MIG aluminium welding process in urine, while plasma failed significance. Biphasic elimination kinetic can be observed. The German BAT of 60 µg/g creatinine was not exceeded, and urinary aluminium returned nearly to baseline concentrations after 7 days.

Solid-phase extraction with multiwalled carbon nanotubes prior to photochemical generation of cadmium coupled to high-resolution continuum source atomic absorption spectrometry

Multiwalled carbon nanotubes (MWCNTs) were used as sorbent for solid phase extraction (SPE) of cadmium ions from water samples. After extraction, volatile cadmium species were generated in the presence of propionic acid under ultraviolet radiation (photochemical generation, UV CVG) and determined by high-resolution continuum source atomic absorption spectrometry (HR-CS AAS) with quartz tube atomization (QTA). The experimental parameters including pH of the solutions, amount of MWCNTs, flow rate of sample, eluent concentration, maximum sample volume and coexisting ions, as well as main parameters of UV CVG HR-CS QTA AAS were investigated. The effective preconcentration of trace cadmium was achieved in pH 7 and the retained cadmium was efficiently eluted with 0.5 mol L−1 HNO3. The limit of detection was 25 μg L−1 and the achieved preconcentration factor was 8.8. The relative standard deviation (RSDs) was 15%. The accuracy of this method was validated by the analyses of NIST SRM 1643e (trace elements in water) and ERM-CA011b (hard drinking water) certified reference materials. The element contents measured in these reference materials were in satisfactory agreement with the certified values according to the t-test for a 95% confidence level. The presented method was successfully applied for the determination of cadmium in four different water samples (seawater, lake water, mine water and tap water).

A simple and fast method for assessment of the nitrogen–phosphorus–potassium rating of fertilizers using high-resolution continuum source atomic and molecular absorption spectrometry

The determination of N, P, and K in fertilizers by high-resolution continuum source flame atomic and molecular absorption spectrometry is proposed. Under optimized conditions, measurements of the diatomic molecules NO and PO at 215.360 and 247.620nm, respectively, and K using the wing of the alternative line at 404.722nm allowed calibration curves to be constructed in the ranges 500–5000mgL−1 N (r=0.9994), 100–2000mgL−1 P (r=0.9946), and 100–2500mgL−1 K (r=0.9995). Commercial fertilizers were analyzed by the proposed method and the concentrations of N, P, and K were found to be in agreement with those obtained by Kjeldahl, spectrophotometric, and flame atomic emission spectrometry methods, respectively, at a 95% confidence level (paired t-test). A phosphate rock certified reference material (CRM) was analyzed and the results for P and K were in agreement with the reference values. Recoveries from spiked CRM were in the ranges 97–105% (NO3−-N), 95–103% (NH4+-N), 93–103% (urea-N), 99–108% (P), and 99–102% (K). The relative standard deviations (n=12) for N, P, and K were 6, 4, and 2%, respectively.

DNA intercalating Ru(II) polypyridyl complexes as effective photosensitizers in photodynamic therapy.

Six substitutionally inert [Ru(II) (bipy)2 dppz](2+) derivatives (bipy=2,2'-bipyridine, dppz=dipyrido[3,2-a:2',3'-c]phenazine) bearing different functional groups on the dppz ligand [NH2 (1), OMe (2), OAc (3), OH (4), CH2 OH (5), CH2 Cl (6)] were synthesized and studied as potential photosensitizers (PSs) in photodynamic therapy (PDT). As also confirmed by DFT calculations, all complexes showed promising (1) O2 production quantum yields, well comparable with PSs available on the market. They can also efficiently intercalate into the DNA double helix, which is of high interest in view of DNA targeting. The cellular localization and uptake quantification of 1-6 were assessed by confocal microscopy and high-resolution continuum source atomic absorption spectrometry. Compound 1, and especially 2, showed very good uptake in cervical cancer cells (HeLa) with preferential nuclear accumulation. None of the compounds studied was found to be cytotoxic in the dark on both HeLa cells and, interestingly, on noncancerous MRC-5 cells (IC50 >100 μM). However, 1 and 2 showed very promising behavior with an increment of about 150 and 42 times, respectively, in their cytotoxicities upon light illumination at 420 nm in addition to a very good human plasma stability. As anticipated, the preferential nuclear accumulation of 1 and 2 and their very high DNA binding affinity resulted in very efficient DNA photocleavage, suggesting a DNA-based mode of phototoxic action.

Application of atomic absorption spectrometry with continuous light source to analyze selected metals important for human health in different parts of oranges

ABSTRACT The publication describes the application of high-resolution continuum source atomic absorption spectrometry (H-R CS AAS) to determine some physiologically essential and toxic elements occurring in citrus fruits of different origins. Before analysis, the samples were mineralized using a mixture of deionized water and 69% nitric acid 3:1 (v/v) in high pressure microwave digestion at 188°C during one hour. The obtained validation parameters for AAS such as high linearity (the correlation coefficient R > 0.997) and high precision expressed as relative standard deviation (%RSD) were satisfactory for quantification. Cadmium at concentration range from 0.29 to 0.43 mg/kg was determined in all tested samples, however the obtained values did not exceed Polish standards. The higher concentration of potassium comparing to sodium and calcium was noted in each investigated samples. The highest variation was observed for calcium, its concentration strongly depended on the country of origin.

Investigating effects of sample pretreatment on protein stability using size-exclusion chromatography and high-resolution continuum source atomic absorption spectrometry.

In this study, size-exclusion chromatography and high-resolution atomic absorption spectrometry methods have been developed and evaluated to test the stability of proteins during sample pretreatment. This especially includes different storage conditions but also adsorption before or even during the chromatographic process. For the development of the size exclusion method, a Biosep S3000 5 μm column was used for investigating a series of representative model proteins, namely bovine serum albumin, ovalbumin, monoclonal immunoglobulin G antibody, and myoglobin. Ambient temperature storage was found to be harmful to all model proteins, whereas short-term storage up to 14 days could be done in an ordinary refrigerator. Freezing the protein solutions was always complicated and had to be evaluated for each protein in the corresponding solvent. To keep the proteins in their native state a gentle freezing temperature should be chosen, hence liquid nitrogen should be avoided. Furthermore, a high-resolution continuum source atomic absorption spectrometry method was developed to observe the adsorption of proteins on container material and chromatographic columns. Adsorption to any container led to a sample loss and lowered the recovery rates. During the pretreatment and high-performance size-exclusion chromatography, adsorption caused sample losses of up to 33%.

Multi-element determination of calcium, potassium and magnesium in medicinal plant by high-resolution continuum source atomic absorption spectrometry

A simple and rugged method to determine Ca, K and Mg in a single aliquot of medicinal plants by high-resolution continuum source flame atomic absorption spectrometry is proposed. Secondary lines for Ca (239.856 nm) and K (404.414 nm), and the alternate line measured at wing of the secondary line for Mg at 202.588 nm allowed calibration within the 20 – 500 mg L-1 Ca and K, and 1.0 – 80 mg L-1 Mg. Twenty samples and three plant certified materials were analyzed. Results were in agreement at a 95% confidence level with reference values. Limits of detection were 2.4 mg L-1 Ca, 1.9 mg L-1 K and 0.3 mg L-1 Mg. The RSD (n=12) were ≤ 5.1% and recoveries were between 83 and 108% for all analytes.

Determination of fluorine in milk and water via molecular absorption of barium monofluoride by high-resolution continuum source atomic absorption spectrometer

This study describes the determination of fluorine evaluating the molecular absorption of barium monofluoride (BaF) at the rotational lines of 495.088 and 495.263nm simultaneously using a high-resolution continuum source electrothermal atomic absorption spectrometer. Upon pipetting of samples together with Ba as its nitrate, BaF was generated in the gas-phase of the atomizer. All experiments were performed using pyrolytically coated graphite tubes/platforms and applying 900°C for pyrolysis and 2200°C for vaporization. In the presence of 50μg of Ba, a perfect linearity up to 0.1μg of F was maintained. The limit of detection and characteristic mass of the method were 0.105ng and 0.055ng of F, respectively. The F concentration of a standard waste water sample was found in the uncertainty limits of its certified value as well as spike additions were quantitatively recovered. Finally, F concentrations in various water and milk samples sold in markets were determined.

Progress in the determination of metalloids and non-metals by means of high-resolution continuum source atomic or molecular absorption spectrometry. A critical review

This work examines the new possibilities introduced with the arrival of commercially available high-resolution continuum source atomic absorption spectrometers for the determination of metalloids (B, Si, Ge, As, Se, Sb and Te) and non-metals (P, S, F, Cl, Br, I and N-based species), such as the improved potential to detect and correct for spectral overlaps and the strategies available to correct for matrix effects. In particular, and considering the increasing number of papers reporting on the use of molecular absorption spectrometry using graphite furnaces and flames as vaporizers, the work discusses in detail the advantages and limitations derived from the monitoring of molecular spectra from a practical point of view, in an attempt to guide future users of the technique.

Detection of silver nanoparticles in parsley by solid sampling high-resolution–continuum source atomic absorption spectrometry

In this work, we present a fast and simple approach for detection of silver nanoparticles (AgNPs) in biological material (parsley) by solid sampling high-resolution-continuum source atomic absorption spectrometry (HR-CS AAS). A novel evaluation strategy was developed in order to distinguish AgNPs from ionic silver and for sizing of AgNPs. For this purpose, atomisation delay was introduced as significant indication of AgNPs, whereas atomisation rates allow distinction of 20-, 60-, and 80-nm AgNPs. Atomisation delays were found to be higher for samples containing silver ions than for samples containing silver nanoparticles. A maximum difference in atomisation delay normalised by the sample weight of 6.27 ± 0.96smg(-1) was obtained after optimisation of the furnace program of the AAS. For this purpose, a multivariate experimental design was used varying atomisation temperature, atomisation heating rate and pyrolysis temperature. Atomisation rates were calculated as the slope of the first inflection point of the absorbance signals and correlated with the size of the AgNPs in the biological sample. Hence, solid sampling HR-CS AAS was proved to be a promising tool for identifying and distinguishing silver nanoparticles from ionic silver directly in solid biological samples.

Multi-elemental analysis of ready-to-eat “baby leaf” vegetables using microwave digestion and high-resolution continuum source atomic absorption spectrometry

The mineral content (phosphorous (P), potassium (K), sodium (Na), calcium (Ca), magnesium (Mg), iron (Fe), manganese (Mn), zinc (Zn) and copper (Cu)) of eight ready-to-eat baby leaf vegetables was determined. The samples were subjected to microwave-assisted digestion and the minerals were quantified by High-Resolution Continuum Source Atomic Absorption Spectrometry (HR-CS-AAS) with flame and electrothermal atomisation. The methods were optimised and validated producing low LOQs, good repeatability and linearity, and recoveries, ranging from 91% to 110% for the minerals analysed. Phosphorous was determined by a standard colorimetric method. The accuracy of the method was checked by analysing a certified reference material; results were in agreement with the quantified value. The samples had a high content of potassium and calcium, but the principal mineral was iron. The mineral content was stable during storage and baby leaf vegetables could represent a good source of minerals in a balanced diet. A linear discriminant analysis was performed to compare the mineral profile obtained and showed, as expected, that the mineral content was similar between samples from the same family. The Linear Discriminant Analysis was able to discriminate different samples based on their mineral profile.

Determination of macro and trace elements in multivitamin dietary supplements by high-resolution continuum source graphite furnace atomic absorption spectrometry with slurry sampling

In this research, three different commercially available multivitamin dietary supplements were analyzed by high-resolution continuum source graphite furnace atomic absorption spectrometry (HR-CS GFAAS) with slurry sampling. The concentrations of Cr, Cu, Fe, Mn, and Se were determined and compared to the amounts stated by producers. The safety of multivitamin dietary supplements depends on various factors including the manufacturing process and the purity and origins of the raw ingredients. For this reason, this research determined concentrations of several toxic elements (As, Cd, and Pb). Microwave-assisted high pressure Teflon bomb digestion was used to determine total amounts of elements in samples. Samples were prepared as slurries at a concentration of 0.1% (m/v) for macro elements (Cr, Cu, Fe, Mn, and Se) and at a concentration of % (m/v) for trace elements (As, Cd, and Pb) in acidic media (3M HNO3). The influence of acid concentration, Triton X-100 addition, sonication time, and sonication power on absorbance was investigated. The accuracy of this method was validated by analyses of NRCC LUTS-1 (Lobster hepatopancreas), NRCC DORM-1 (Dogfish Muscle), NRCC DOLT-2 (Dogfish Liver), NBS SRM 1570 (Spinach Leaves) and NBS SRM 1573 (Tomato Leaves) certified reference materials. The measured elements contents in these reference materials (except NRCC DOLT-2) were in satisfactory agreement with the certified values according to the t-test for a 95% confidence level.

Molecule Formation Mechanisms of Strontium Mono Fluoride in High-Resolution Continuum Source Electrothermal Atomic Absorption Spectrometry

In this study, the molecule formation mechanisms of strontium mono fluoride used for the determination of fluorine in a high-resolution continuum source atomic absorption spectrophotometer was investigated. To distinguish between the gas-phase and the condensed-phase mechanisms, the analyte (F) and the molecule forming element (Sr) were injected on the solid sampling platform manually, as mixed or separately, and the absorbances/peak shapes were compared. There was no significant difference between the absorbances. In addition, the peak shapes and the appearance times were almost the same for the two cases. It was proposed that the main pathway for SrF formation is a gas-phase combination reaction between Sr and F. When Sr and F were mixed on the platform, it was expected that at first SrF2 would be formed in the condensed phase, and then at elevated temperatures it was partly decomposed while either losing one F atom to form SrF, or completely decomposed to its atoms in the gas phase.

Determination of Gold by High-Resolution Continuum Source Atomic Absorption Spectrometry with Chemical Vapor Generation

The analytical potential of chemical vapor generation and high-resolution continuum source atomic absorption spectrometry (CVG HR-CS AAS) with quartz tube atomization in determination of gold was evaluated. The volatile species of gold were formed by reaction with sodium tetrahydroborate(III) in the presence of hydrochloric acid. The influence of didodecyldimethylammonium bromide (DDAB) and sodium diethyldithiocarbamate (DDTC) on the absorbance was investigated. The concentration limit of detection was 2.6 ng mL-1 for Au. The precision of measurement at 20 ng mL-1 of Au was 10% of the relative standard deviation (RSD). The accuracy of this method was validated by analyses of NRCC PCT-1a (Copper-Nickel Sulfide Concentrate with Noble Metals), NIST SRM 2710 (Montana Soil) and NIST SRM 1643e (Trace Element in Water) certified reference materials. The measured Au contents in these three reference materials were in satisfactory agreement with the certified values. This method was also applied for gold determination in coal fly ash, sediment and nickel alloy.