Search

A simple method has been developed to determine antimony and lead in pewter alloy cups produced in Brazil, using fast sequential determination by high-resolution continuum source flame atomic absorption spectrometry. The samples were dissolved in HCl and H(2)O(2), employing a cold finger system in order to avoid analyte losses. The main resonance line of lead at 217.001 nm and a secondary line of antimony at 212.739 nm were used. The limits of detection for lead and antimony were 0.02 and 5.7 mg L(-1), respectively. The trueness of the method was established by recovery tests and comparing the results obtained by the proposed method with those obtained by inductively coupled plasma optical emission spectrometry. The results were compared using a student's t-test and there was no significant difference at a 95% confidence interval. With the developed methods, it was possible to determine accurately antimony and lead in pewter samples. The lead concentration found in the analysed samples was around 1 mg g(-1), which means that they are not lead free; however, the content was below the maximum allowed level of 5 mg g(-1). The antimony content, which was found to be between 40 and 46 mg g(-1), is actually of greater concern, as antimony is known to be potentially toxic already at very low concentrations, although there is no legislation yet for this element.

This paper presents the validation of a system for sample digestion using a digester block/ cold finger to determine the lead content in vegetables by electrothermal atomic absorption spectrometry (ETAAS). After mineralization, lead contents were determined by ETAAS using a calibration curve based on aqueous standards prepared in 2.60 M nitric acid solutions containing 5 μg ammonium phosphate as chemical modifier. A pyrolysis temperature of 900°C and atomization temperature of 2000°C were used. This method allowed the determination of lead with a characteristic mass of 35 pg; LOD and LOQ of 0.6 and 2 ng/g, respectively, were found. The precision was investigated in terms of reproducibility and repeatability. Reproducibility was estimated by analysis of nine different portions of a certified reference material (CRM) of spinach leaves, and the repeatability was determined through the analysis of nine aliquots of the same solution. The reproducibility and repeatability were found to be 4.27 and 2.94% RSD, respectively. The accuracy was confirmed by analysis of whole meal flour, spinach leaves, and orchard leaves CRMs, all furnished by the National Institute of Standards and Technology. Lead contents were measured using the newly developed technique in 11 different potato samples. The lead contents ranged from 12.80 to 69.27 ng/g, with an average value of 28.59 ng/g. These values were in agreement with data reported in the literature.

Inductively coupled plasma optical emission spectrometry was used to determine the elements present in Chinese cabbage (Beta vulgaris). The accuracy of the method was confirmed by analysis of a certified reference material of spinach leaves. The study involved 57 samples that were collected in 13 Brazilian cities. Average concentrations of elements found per gram of Chinese cabbage were as follows: 3.44 mg g−1 sodium, 5.09 mg g−1 potassium, 1.25 mg g−1 phosphorous, 0.85 mg g−1 calcium, 0.49 mg g−1 magnesium, 2.79 μg g−1 manganese, 9.50 μg g−1 iron, 0.74 μg g−1 copper, 14.28 μg g−1 zinc, and 6.44 μg g−1 strontium. Principal component analysis and hierarchical cluster analysis demonstrated that there is no systematic difference in the mineral composition between the cabbage samples that were analyzed.

The method allowed simultaneous characterization of PAHs, nitro-PAHs and quinones in atmospheric particulate matter. This method employs a miniaturized micro-extraction step that uses 500 μL of an acetonitrile-dichloromethane mix and instrumental analysis by means of a high-resolution GC-MS. The method was validated using the SRM1649b NIST standard reference material as well as deuterated internal standards. The results are in good agreement with the certified values and show recoveries between 75% and 145%. Limit of detection (LOD) values for PAHs were found to be between 0.5 pg (benzo[a]pyrene) to 2.1 pg (dibenzo[a,h]anthracene), for nitro-PAHs ranged between 3.2 pg (1-nitrobenzo[e]pyrene) and 22.2 pg (3-nitrophenanthrene), and for quinones ranged between 11.5 pg (1,4-naphthoquinone) and 458 pg (9,10-phenanthraquinone). The validated method was applied to real PM10 samples collected on quartz fiber filters. Concentrations in the PM10 samples ranged from 0.06 to 15 ng m(-3) for PAHs, from

In this paper, a method for the determination of mercury in phosphate fertilizers using slurry sampling and cold vapor atomic absorption spectrometry (CV QT AAS) is proposed. Because mercury (II) ions form strong complexes with phosphor compounds, the formation of metallic mercury vapor requires the presence of lanthanum chloride as a release agent. Thiourea increases the amount of mercury that is extracted from the solid sample to the liquid phase of the slurry. The method is established using two steps. First, the slurry is prepared using the sample, lanthanum chloride, hydrochloric acid solution and thiourea solution and is sonicated for 20 min. Afterward, mercury vapor is generated using an aliquot of the slurry in the presence of the hydrochloric acid solution and isoamylic alcohol with sodium tetrahydroborate solution as the reducing agent. The experimental conditions for slurry preparation were optimized using two-level full factorial design involving the factors: thiourea and lanthanum chloride concentrations and the duration of sonication. The method allows the determination of mercury by external calibration using aqueous standards with limits of detection and quantification of 2.4 and 8.2 μg kg−1, respectively, and precision, expressed as relative standard deviation, of 6.36 and 5.81% for two phosphate fertilizer samples with mercury concentrations of 0.24 and 0.57 mg kg−1, respectively. The accuracy was confirmed by the analysis of a certified reference material of phosphate fertilizer that was provided by the National Institute of Standards & Technology (NIST). The method was applied to determine mercury in six commercial samples of phosphate fertilizers. The mercury content varied from 33.97 to 209.28 μg kg−1. These samples were also analyzed employing inductively coupled plasma mass spectrometry (ICP-MS). The ICP-MS results were consistent with the results from our proposed method.

The homogeneity and stability of metals were tested in a candidate laboratory reference material of soy leaves. Inductively coupled plasma-optical emission spectrometry was used to quantify calcium, magnesium, manganese, iron, zinc, copper, and vanadium. A 6 kg amount of the material, which was dried, ground, and classified as mesh 60, was distributed among 100 bottles. The between-bottle homogeneity test was established by analyzing two subsamples from nine bottles. For the within-bottle test, five determinations of each element of a single bottle were performed. The stability test was performed at temperatures of –10, +27, and +40°C, and after storage times of 4, 12, 24, and 52 weeks. The obtained results indicated that the material was homogeneous and stable under the conditions studied.

In this paper, we proposed a procedure for the determination of iron(II) and total iron in wine samples employing molecular absorption spectrophotometry. The ligand used is 2-(5-bromo-2-pyridylazo)-5-(diethylamino)-phenol (Br-PADAP) and the chromogenic reaction in absence or presence of ascorbic acid (reducing agent) allows the determination of iron(II) or total iron, respectively. The optimization step was performed using a multivariate technique (Box Behnken design) involving the factors pH, acid ascorbic concentration and reaction time. The method allows the determination of iron(II) and iron(III) in wine samples, with limits of detection and quantification 0.22 and 0.72 microg L(-1), respectively. The precision expressed as relative standard deviation (R.S.D.) was 1.43 and 0.56% (both, n=11) for content of iron(II) in wine samples of 1.68 and 4.65 mg L(-1), and 1.66 and 0.87% (both, n=11) for content of total iron in wine samples of 1.72 and 5.48 mg L(-1). This method was applied for determination of iron(II) and total iron in six different wine samples. In these, the iron(II) content varied from 0.76 to 4.65 mg L(-1) and from 1.01 to 5.48 mg L(-1) for total iron. The results obtained in the determination of total iron by Br-PADAP method were compared with those that were performed after complete acid digestion in open system and determination of total iron employing FAAS. The method of regression linear was used for comparison of these results and demonstrated that there is no significant difference between the results obtained with these two procedures.

A fast and simple procedure is proposed for determination of manganese in corn flour samples employing slurry sampling and electrothermal atomic absorption spectrometry. To evaluate the particle size scanning electron microscopy was used. Slurries were prepared by weighing approximately 100 mg of sample, adding 0.014 mol L−1nitric acid, and a solution containing 1% Triton X-100. An ultrasonic bath was employed for slurry homogenization. Analytical variables including temperature program of the graphite furnace, nitric acid concentration, amount of sample and sonication times were studied. The pyrolysis and atomization temperatures established during the optimization step were 1200 and 2100 °C, respectively, using 10 μg Pd + 3 μg Mg as the chemical modifier. The limits of detection and quantification obtained were 0.006 and 0.020 μg g−1, respectively. A characteristic mass of 0.97 pg was obtained. The precision was evaluated for a sample containing 2.17 μg g−1 of manganese and 2.6% relative standard deviation was found (n = 10). The accuracy was assessed by the analysis of two certified reference materials: NIST SRM 1568a—Rice Flour and CRM 189—Wholemeal Flour. Some experiments demonstrated that the calibration can be performed employing the external calibration technique using aqueous standards. For comparison and validation of the procedure proposed, the samples were also analyzed after complete decomposition and determined by ETAAS and good precision was obtained (at 95% confidence level). In this way, no statistical difference was observed between the results obtained by both the procedures performed. The proposed procedure has been applied for manganese determination in six samples acquired in supermarkets of Salvador (Brazil) and values varied from 0.623 to 2.17 μg g−1.

Aluminium was used as a chemical modifier for the determination of lead in sugar cane spirit samples by electrothermal atomic absorption spectrometry (ET-AAS). Pyrolysis temperature, pyrolysis time and atomisation temperature were 800 °C, 20 s and 1800 °C, respectively. The aluminium mass was 3 µg. Lead was quantified with limits of detection and quantification of 0.14 and 0.47 µg L−1, respectively, and a characteristic mass of 24 pg. Analyte addition experiments demonstrated that external calibration can be performed with aqueous standards. The precision, expressed as relative standard deviation (RSD%), was 3.11% for a sample with a lead concentration of 3.00 µg L−1. There is currently no certified reference material for sugar cane spirits, so a standard reference material of orchard leaves was used to confirm accuracy. The proposed method was used to determine the lead content of five sugar cane spirit samples from Salvador City, Brazil. Their lead contents varied from 3.00 to 19.61 µg L−1. The samples were also analysed by inductively coupled plasma mass spectrometry (ICP-MS) after acid digestion in a closed system. No statistical difference was observed between the results obtained by both methods.