Habitat use and nursery evaluation for the longnose stingray Hypanus guttatus (Bloch & Schneider, 1801) using vertebral microchemistry.

Here, we use vertebral microchemistry to investigate the habitat use patterns of the longnose stingray Hypanus guttatus in the northern and northeastern regions of Brazil, and to evaluate the existence of potential nurseries of the species. Samples were collected in Maranhão, Rio Grande do Norte and Pernambuco states between 2008 and 2019. Trace element concentrations of Ba:Ca, Mg:Ca, Mn:Ca and Sr:Ca in vertebrae were determined through laser ablation inductively coupled plasma mass spectrometry. We used one-step permutational ANOVAs to evaluate multi and single-element differences in element:Ca ratios among life stages and sexes across and within sites. Element signatures differed among all sites for both single and multi-element settings. However, there were few differences among life stages within sites, except for Mn:Ca between life stages for Maranhão state, and between sexes for Sr:Ca for both Pernambuco and Rio Grande do Norte, and Ba:Ca for Rio Grande do Norte. Furthermore, all multi and single-element analyses across locations were significant and highlight the strong differences by sites. We also performed a nonmetric multidimensional scaling analysis, which demonstrated the strong differences for samples from Rio Grande do Norte and the other two sites. By analysing the lifetime transects of each sample, we observed that there was little variation in all element:Ca ratios within sites. Therefore, we argue that the longnose stingray likely does not display extensive habitat use shifts and fulfils much of its life cycle within each area. Finally, we obtained no evidence of nurseries for any site and suggest this is likely a pattern across the species distribution. Future studies investigating habitat use with samples from larger specimens (disc width > 90 cm, >15 years) are needed to better understand the species habitat use patterns across all size ranges.

La2O3 Nanoparticles: Study of Uptake and Distribution in Pfaffia glomerata (Spreng.) Pedersen by LA-ICP-MS and µ-XRF.

The production and use of nanoparticles (NPs) in different fields increased in the last years. However, some NPs have toxicological properties, making these materials potential emerging pollutants. Therefore, it is important to investigate the uptake, transformation, translocation, and deposition of NPs in plants. In this work, laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) and micro X-ray fluorescence (µ-XRF) were used to investigate the uptake and translocation of La2O3 NPs to stem and leaves of Pfaffia glomerata (Spreng.) Pedersen after in vitro cultivation of plants in the presence of 400 mg L-1 of La2O3 NPs. By using LA-ICP-MS and µ-XRF, image of the spatial distribution of La in the leaves was obtained, where higher concentration of La was observed in the main veins. Differences in the signal profile of La in leaves of plants cultivated in the presence of bulk La2O3 (b-La2O3) and La2O3 NPs were observed. Sharp peaks of La indicated that NPs were transported to the stems and leaves of plants treated with La2O3 NPs. Both LA-ICP-MS and µ-XRF techniques have shown to be useful for detecting NPs in plants, but LA-ICP-MS is more sensitive than µ-XRF and allowed better detection and visualization of La distribution in the whole leaf.

Triphenyltin hydroxide induces changes in the oxidative stress parameters of fish.

Among all organotin compounds , triphenyltin hydroxide (TPhTH) is widely used as fungicide and moluscicide in Brazil. However, the effects of TPhTH on the biochemical parameters of non-target organisms, such as fish, are little known. The aim of the present study is to assess the possible toxic effects of different concentrations of waterborne TPhTH on silver catfish belonging to species Rhamdia quelen. The fish were exposed to two different concentrations of TPhTH (1.08 and 1.70 µg/L as Sn) for 15 days and then compared to the control group (triplicate, n = 3). The antioxidant profile (catalase (CAT) and the glutathione S-transferase (GST)) and the oxidative stress parameters (TBARS-thiobarbituric acid-reactive substances and protein carbonyl (PC)) were set after the exposure to TPhTH. The TBARS level and the PC content increased in several organs of the Rhamdia quelen (brain, liver, muscle and gills) under the two concentrations of TPhTH in comparison to the control group. The CAT activity in the liver and gills has enhanced in all tested TPhTH concentrations. The GST activity increased in the brain, liver and muscle tissues under all the TPhTH concentrations. The significant changes in the biomarkers indicated that the investigated pesticide could have harmful effect on fish, in the field. However, these biomarkers were measured after the fish received doses lower than the recommended for use in agriculture.

Effect of zinc supplementation on E-ADA activity, seric zinc, and cytokines levels of Trypanosoma evansi infected Wistar rats.

The aim of this study was to evaluate the effect of zinc supplementation on the ecto-adenosine deaminase activity (E-ADA), zinc seric levels and cytokines (TNF-α, IL-1, IL-6, and IL -10) on rats experimentally infected by Trypanosoma evansi. Four groups with 10 rats each were used as negative controls (groups A and B), while the animals from the groups C and D were infected intraperitoneally with 0.1 mL of cryopreserved blood containing 1.4 × 10(4) of trypanosomes. Animals of groups B and D received two doses of Zinc (Zn) at 5 mg kg(-1), subcutaneously, on the 2nd and 7th day post-infection (PI). Blood samples were collected on days 5 (n = 5) and 15 PI (n = 5). Zn supplementation was able to increase the rat's longevity and to reduce their parasitemia. It was observed that seric Zn levels were increased on infected animals under Zn supplementation. Animals that were infected and supplemented with Zn showed changes in E-ADA activity and in cytokine levels (P < 0.05). Zn supplementation of healthy animals (Group B), increased the E-ADA activity, as well as reduced the concentration of cytokines. Infected animals from groups C and D showed increased levels of cytokines. Finally, we observed that Zn supplementation led to a modulation on cytokine's level in rats infected by T. evansi, as well as in E-ADA activity.

Lactating and nonlactating rats differ to renal toxicity induced by mercuric chloride: the preventive effect of zinc chloride.

This study evaluated the effects of HgCl2 on renal parameters in nonlactating and lactating rats and their pups, as well as the preventive role of ZnCl2 . Rats received 27 mg kg(-1) ZnCl2 for five consecutive days and 5 mg kg(-1) HgCl2 for five subsequent days (s.c.). A decrease in δ-aminolevulinic acid dehydratase (δ-ALA-D) activity in the blood and an increase in urine protein content in renal weight as well as in blood and urine Hg levels were observed in lactating and nonlactating rats from Sal-Hg and Zn-Hg groups. ZnCl2 prevented partially the δ-ALA-D inhibition and the proteinuria in nonlactating rats. Renal Hg levels were increased in all HgCl2 groups, and the ZnCl2 exposure potentiated this effect in lactating rats. Nonlactating rats exposed to HgCl2 exhibited an increase in plasma urea and creatinine levels, δ-ALA-D activity inhibition and histopathological alterations (necrosis, atrophic tubules and collagen deposition) in the kidneys. ZnCl2 exposure prevented the biochemical alterations. Hg-exposed pups showed lower body and renal weight and an increase in the renal Hg levels. In conclusion, mercury-induced nephrotoxicity differs considerably between lactating and nonlactating rats. Moreover, prior exposure with ZnCl2 may provide protection to individuals who get exposed to mercury occupationally or accidentally.

Toxicity of triphenyltin hydroxide to fish.

Triphenyltin (TPhT) is used worldwide in pesticide formulas for agriculture. Toxic effects of this compound to aquatic life have been reported; however, the biochemical response of fish exposed to different concentrations of TPhT hydroxide (TPhTH) was investigated for the first time in this study. The lethal concentration (LC50) of TPhTH to silver catfish, Rhamdia quelen, was calculated from an acute-exposure experiment (96 h). In addition, acethylcholinesterase (AChE) activity in brain and muscle-as well as glucose, glycogen, lactate, total protein, ammonia, and free amino acids in liver and muscle-were evaluated in a chronic-exposure experiment (15-day exposure). Speciation analysis of tin (Sn) was performed in fish tissues at the end of both experiments using gas chromatography coupled to a pulsed-flame photometric detector (GC-PFPD). Concentrations of TPhT, diphenyltin, and monophenyltin (reported as Sn) were lower than limits of quantification (10σ criteria). Waterborne TPhTH concentration used through the experiment was also evaluated by GC-PFPD, and no degradation of this species was observed. The LC50 value for silver catfish juveniles was 9.73 µg L(-1) (as Sn). Decreased brain and muscle AChE activities were observed in fish exposed to TPhTH in relation to unexposed fish (control). Liver glycogen and lactate levels were significantly higher in fish kept at the highest waterborne TPhTH concentration compared with the control. Liver and muscle glucose levels of fish exposed to all TPhTH concentrations were significantly lower than those of control fish. Silver catfish exposed to all TPhTH concentrations showed lower total protein values and higher total free amino acids levels in liver and muscle compared with controls. Total ammonia levels in liver and muscle were significantly higher for the highest TPhTH concentration compared with controls. In conclusion, TPhTH caused metabolic alterations in silver catfish juveniles, and the analyzed parameters can also be used as bioindicators for TPhTH contamination.

Hematological indices and activity of NTPDase and cholinesterase enzymes in rats exposed to cadmium and treated with N-acetylcysteine.

The present study aimed to investigate the influence of N-acetylcysteine (NAC) on cadmium (Cd) poisoning by evaluating Cd concentration in tissues, hematological indices as well as the activity of NTPDase, acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) enzymes of rats exposed to Cd and co-treated with NAC. For this purpose, the rats received Cd (2 mg/kg) and NAC (150 mg/kg) by gavage every other day for 30 days. Animals were divided into four groups (n = 6-8): control/saline, NAC, Cd, and Cd/NAC. Cd exposure increased Cd concentration in plasma, spleen and thymus, and NAC co-treatment modulated this augment in both lymphoid organs. Cd exposure reduced red blood cell count, hemoglobin content and hematocrit value. Cd intoxication caused a decrease in total white blood cell count. NAC treatment per se caused an increase in lymphocyte and a decrease in neutrophil counts. On contrary, Cd exposure caused a decrease in lymphocyte and an increase in neutrophil and monocyte counts. NAC reversed or ameliorated the hematological impairments caused by Cd poisoning. There were no significant alterations in the NTPDase activity in lymphocytes of rats treated with Cd and/or NAC. Cd caused a decrease in the activities of lymphocyte AChE, whole blood AChE and serum BChE. However, NAC co-treatment was inefficient in counteracting the negative effect of Cd in the cholinesterase activities. The present investigation provides ex vivo evidence supporting the hypothesis that Cd induces immunotoxicity by interacting with the lymphoid organs, altering hematological parameters and inhibiting peripheral cholinesterase activity. Also, it highlights the possibility to use NAC as adjuvant against toxicological conditions.

Speciation and degradation of triphenyltin in typical paddy fields and its uptake into rice plants.

Triphenyltin (TPhT) is a biocide used worldwide in agriculture, especially in rice crop farming. The distribution and dissipation of TPhT in rice fields, as well as uptake of TPhT and other phenyltin compounds (monophenyltin, MPhT, and diphenyltin, DPhT) is still unknown at present. In this study, speciation analysis of phenyltin compounds was carried out in soil and water from a rice field where TPhT was applied during rice seeding according to legal application rates in Brazil. The results indicate the degradation of biocide and distribution of tin species into soil and water. To evaluate whether TPhT is taken up by plants, rice plants were exposed to three different TPhT application rates in a controlled mesocosm during 7 weeks. After this period, tin speciation was determined in soil, roots, leaves, and grains of rice. Degradation of TPhT was observed in soil, where DPhT and MPhT were detected. MPhT, DPhT, and TPhT were also detected in the roots of plants exposed to all TPhT application rates. Only TPhT was detected in leaves and at relatively low concentration, suggesting selective transport of TPhT in the xylem, in contrast to DPhT and MPhT. Concentration of phenyltin species in rice grains was lower than the limit of detection, suggesting that rice plants do not have the capability to take up TPhT from soil and transport it to the grains.

Delta-aminolevulinate dehydratase activity in red blood cells of rats infected with Trypanosoma evansi.

The aim of this study was to evaluate the activity of delta-aminolevulinate dehydratase (δ-ALA-D) in red blood cells of rats infected with Trypanosoma evansi and establish its association with haematocrit, serum levels of iron and zinc and lipid peroxidation. Thirty-six male rats (Wistar) were divided into 2 groups with 18 animals each. Group A was non-infected while Group B was intraperitoneally infected, receiving 7·5×106 trypomastigotes per animal. Each group was divided into 3 subgroups of 6 rats and blood was collected during different periods post-infection (p.i.) as follows: day 5 (A1 and B1), day 15 (A2 and B2) and day 30 PI (A3 and B3). Blood samples were collected by cardiac puncture to estimate red blood cell parameters (RBC), δ-ALA-D activity and serum levels of iron, zinc and thiobarbituric acid reactive substances (TBARS). Rats in group B showed a significant (P<0·05) reduction of RBC count, haemoglobin concentration and haematocrit at days 5 and 15 p.i. The activity of δ-ALA-D in blood was significantly (P<0·001) increased at days 15 and 30 p.i. δ-ALA-D activity in blood had a significant (P<0·05) negative correlation with haematocrit (r=-0·61) and haemoglobin (r=-0·70) at day 15 p.i. There was a significant (P<0·05) decrease in serum iron and zinc levels and an increase in TBARS levels (P<0·05) during infection. The δ-ALA-D activity in blood was negatively correlated with the levels of iron (r=-0·68) and zinc (r=-0·57) on day 30 p.i. It was concluded that the increased activity of δ-ALA-D in blood might have occurred in response to the anaemia in remission as heme synthesis was enhanced.

Iodine determination in food by inductively coupled plasma mass spectrometry after digestion by microwave-induced combustion.

Iodine determination in food samples was performed by inductively coupled plasma mass spectrometry (ICP-MS) after digestion by microwave-induced combustion (MIC). Sample masses up to 500 mg of bovine liver, corn starch, milk powder, or wheat flour were completely combusted using the MIC system. Ammonium nitrate (6 mol l(-1) solution, 50 µl) was used as an aid for ignition and vessels were charged with 15 bar of O(2). The use of H(2)O, 0.9 mmol l(-1) H(2)O(2), 10 to 50 mmol l(-1) (NH(4))(2)CO(3) and 56 mmol l(-1) tetramethylammonium hydroxide was investigated as absorbing solutions, as well as the suitability of performing a reflux step after the combustion process. Digestion of food samples by pressurized microwave-assisted acid digestion, microwave-assisted extraction and conventional extraction of iodine in alkaline solution were also evaluated. Iodine recoveries higher than 99% were obtained using MIC and 50 mmol l(-1) (NH(4))(2)CO(3) or 56 mmol l(-1) tetramethylammonium hydroxide as absorbing solution and with 5 min for the reflux step. Accuracy was evaluated using certified reference materials (bovine muscle, corn bran, and milk powder) and agreement better than 97% was obtained. The limit of quantification by MIC and further ICP-MS determination was 0.002 µg g(-1). Blanks were always low and no memory effects were observed. Digestion by MIC allowed the processing of up to eight samples by each run in 25 min with high efficiency of digestion (residual carbon content lower than 1%) providing a suitable medium for further iodine determination by ICP-MS.

Evaluation of sample preparation methods for elastomer digestion for further halogens determination.

In this work, three sample preparation methods were evaluated for further halogen determination in elastomers containing high concentrations of carbon black. Samples of nitrile-butadiene rubber, styrene-butadiene rubber, and ethylene-propylene-diene monomer elastomers were decomposed using oxygen flask combustion and microwave-induced combustion (MIC) for further Br and Cl determination by ion chromatography (IC), inductively coupled plasma optical emission spectrometry (ICP OES), and inductively coupled plasma mass spectrometry (ICP-MS). Extraction assisted by microwave radiation in closed vessels was also evaluated using water or alkaline solution. Digestion by MIC was carried out using 50 mmol l(-1) (NH(4))(2)CO(3) as the absorbing solution. The effect of the reflux step was also evaluated. Accuracy was evaluated using certified reference materials with polymeric matrix composition and by comparison of results using neutron activation analysis. Agreement for Br and Cl was better than 95% by MIC using 5 min of reflux, and no statistical difference was found using IC, ICP OES, and ICP-MS for determination of both analytes. For MIC, the relative standard deviation (RSD) was lower than 5%. Using extraction in closed vessels, a high amount of residues was observed, and recoveries were lower than 45% for both analytes. For oxygen flask combustion, the agreement was similar using MIC but RSD was higher (20%). The residual carbon content, an important parameter used to evaluate the digestion efficiency, was always below 1% for MIC. Using MIC, it was possible to digest elastomers with high efficiency, resulting in a single solution suitable for halogen determination by different techniques.

Protective effect of high alkalinity against the deleterious effects of chronic waterborne cadmium exposure on the detection of alarm cues by juvenile silver catfish (Rhamdia quelen).

The objective of the present study was to analyze the effect of chronic cadmium (Cd) exposure at two alkalinity levels (63 and 92 mg l(-1) CaCO(3)) on the antipredatory behavior of juvenile silver catfish (Rhamdia quelen) exposed to conspecific skin extract and predator odor. At an alkalinity of 63 mg l(-1) CaCO(3), 30 days of exposure to either 4.5 or 8.0 microg l(-1) Cd impaired the catfish's antipredatory response to alarm cues. However, silver catfish exposed to 4.5 microg l(-1) Cd at an alkalinity of 92 mg l(-1) CaCO(3) responded to skin extract and predator odor. In catfish exposed to 8.0 microg l(-1) Cd at the same alkalinity, only the number of feeding bites decreased, and this occurred only for specimens exposed to predator odor. Our results show that higher alkalinity protected against the deleterious effects of Cd on alarm cue detection but only in the larvae exposed to the lowest waterborne Cd level.

Chloride determination by ion chromatography in petroleum coke after digestion by microwave-induced combustion.

Microwave-induced combustion was applied to petroleum coke digestion in closed vessels for further chloride determination by ion chromatography. Samples were pressed as pellets and placed on a quartz holder. Combustion was performed using oxygen pressure of 2 MPa and 50 microl of 6 moll(-1) NH(4)NO(3) as aid for ignition. Recoveries from 97 to 102% were obtained for all studied absorbing solutions (water, H(2)O(2), Na(2)CO(3) or (NH(4))(2)CO(3)). Accuracy was evaluated using certified reference materials with agreement better than 98% using water as absorbing solution with reflux step. The limit of quantification was 3.8 microg g(-1).

Biochemistry, cytogenetics and bioaccumulation in silver catfish (Rhamdia quelen) exposed to different thorium concentrations.

The objective of this study was to evaluate the effect of thorium (Th) bioaccumulation on the metabolism of silver catfish (Rhamdia quelen) through biochemical parameters of the muscle (glycogen, glucose, lactate, protein, and ammonia). In addition, lipidic peroxidation levels (TBARS), catalase (CAT) and glutathione-S-transferase (GST) in the gills and in hepatic and muscular tissues were also analyzed. Cytogenetic parameters were studied through the evaluation of nuclear abnormalities in red blood cells. Silver catfish juveniles were exposed to different waterborne Th levels (in microg L(-1)): 0 (control), 25.3+/-3.2, 69.2+/-2.73, 209.5+/-17.6, and 608.7+/-61.1 for 15 days. The organs that accumulated the highest Th levels were the gills and skin. The increase of waterborne Th concentration corresponded to a progressive increase of Th levels in the gills, liver, skin and kidneys, with the highest accumulation in the gills and skin. Metabolic intermediates in the muscle were altered by Th exposure, but no clear relationship was found. CAT and GST activities in the hepatic and muscular tissues of this species suggest that the enzymatic activities can be stimulated at the lowest Th levels and inhibited at the higher levels (mainly in 608.7 microg L(-1)). The results of the cytogenetic assay contribute to this hypothesis because the higher toxicity in blood samples was found in juveniles exposed to 69.2 and 209.5 microg L(-1) Th.

Rare earth elements profile in a cultivated and non-cultivated soil determined by laser ablation-inductively coupled plasma mass spectrometry.

Rare earth elements (REEs) have several applications but the effects on environment are not well known. Therefore, the aim of this work is to establish a method for direct solid sample analysis by laser ablation-inductively coupled plasma mass spectrometry (LA-ICP-MS) to evaluate the concentration and distribution of REEs in cultivated and non-cultivated soil. Samples were collected in two areas to 40 cm of depth. The LA-ICP-MS method is easy to be implemented and the sample treatment is very fast comprising only its drying, grounding and pressing as a pellet. The accuracy of the method was evaluated by using a certified reference material (BCR 667 - Estuarine Sediment, Institute for Reference Materials and Measurements (IRMM)) where good agreement with the certified values was obtained. Analyte recovery at two levels of concentration (2.5 and 15.0 µg g-1) was also performed and recoveries in the range of 85%-120% were achieved, values that are acceptable for LA-ICP-MS analysis. In general, the concentration of the REEs is higher in the cultivated soil and increased from the surface to deeper layers, which can be a consequence of fertilizer application.

Delta-aminolevulinate dehydratase (delta-ALA-D) activity in diabetes and hypothyroidism.

OBJECTIVES: This study analyzed the influence of type 2 diabetes mellitus and primary hypothyroidism on the activity of the delta-aminolevulinate dehydratase (delta-ALA-D) in human blood. DESIGN AND METHODS: Delta-ALA-D enzyme activity was determined in normal (healthy) people (n=29), compensated (DMC, n=11) and non-compensated diabetic patients (NDMC, n=23), and in patients with compensated (CH, n=19) and non-compensated primary hypothyroidism (NCH, n=10). The determination of lead, copper, zinc and magnesium was performed by graphite furnace atomic absorption spectrometry. RESULTS: This study shows that delta-ALA-D activity was decreased (P<0.05) in situations associated to hyperglycemia maintained for long periods (HbA1c high). Another finding of this study suggests that states of hypofunction of the thyroid gland, when non-compensated, increase the activity of delta-ALA-D (P<0.001). In addition, copper was elevated in HNC, zinc was diminished in DMC, HC and HNC, and magnesium was diminished in the HNC group. CONCLUSION: This result points out that there is a correlation among diabetes, hypothyroidism and delta-ALA-D activity.

Sr and Fe relationship with hormone replacement therapy and bone mineral density.

BACKGROUND: We determined blood strontium (Sr) and iron (Fe) concentrations and their relationship with bone mineral density (BMD) and some biochemical parameters in premenopausal and postmenopausal women without or with hormone replacement therapy (HRT). METHODS: Blood Sr and Fe concentrations, BMD, follicle stimulating hormone (FSH), 17beta-estradiol (E2), creatinine, albumin, blood calcium and alkaline phosphatase activity were determined in premenopausal and postmenopausal women without or with HRT (mean ages: 47, 59, and 57 y, respectively). RESULTS: Blood Sr (microg/l) and Fe (mg/l) concentrations in premenopausal (31.65+/-2.96 and 496.05+/-14.37) and postmenopausal women without (28.85+/-2.48 and 525.27+/-8.56) or with (25.98+/-2.73 and 535.77+/-17.57) HRT were not significantly different. BMD L1-L4 and BMD femur (g/cm2) were significantly higher in premenopausal women (1.05+/-0.02 and 0.84+/-0.02) when compared both to postmenopausal women without (0.90+/-0.03 and 0.75+/-0.02) and with (0.93+/-0.03 and 0.73+/-0.01) HRT. However, BMD had no relationship with blood metal concentrations. E2 concentrations were lower in postmenopausal women without HRT, while FSH concentrations were higher in both postmenopausal groups (p<0.05). CONCLUSIONS: Physiological whole blood Sr and Fe concentrations had no significant effect in BMD and other biochemical parameters in pre and postmenopausal women. However, BMD was negatively influenced by FSH concentrations and associated with age.

Arsenic determination in marine sediment using ultrasound for sample preparation.

This work deals with As determination in marine sediment using ultrasound for sample preparation. It is shown that As can be quantitatively extracted from marine sediment using 20% (v/v) HCl and sonication. The slurry is centrifuged and the analyte is determined in the supernatant by hydride generation atomic absorption spectrometry (HG AAS). A flow injection (FI) system is employed for hydride generation, with 0.5% (m/v) NaBH(4) used as reducdant and a 20% (v/v) HCl used as sample carrier. The limit of quantification is 1.6 microg g(-1) of As, which is based on 800 microl of sample solution and 0.200 g of sample mass in a volume of 50 mL. Certified and non certified marine sediment samples were analyzed; the results were in accordance with the certified or reference values. Speciation analysis by HPLC-ICP-MS showed that As(V) is the only detectable As species present in the supernatant of the centrifuged sample.

A new approach to calibration and determination of selected trace elements in food contact polymers by LA-ICP-MS.

A calibration strategy using porous nylon disks and reference solutions is proposed for the first time for matrix matching and determination of As, Ba, Cd, Cr, Pb, Sr and Zn in polymers by laser ablation-inductively coupled plasma mass spectrometry (LA-ICP-MS). Polymer samples commonly used in contact with food were analyzed. The procedure consists on the use of porous nylon disks as support for a dried droplet reference solution. Calibration in the range of 0.50-190µgg-1 for Ba, Cd, Cr, Pb, Sr and Zn and from 0.30-9.0µgg-1 for As was used. Laser and ICP-MS instrument conditions were evaluated in order to achieve the best signal-to-background ratio. The radiofrequency power and carrier gas flow rate were fixed at 1300W and 1.25Lmin-1, respectively. Spot size, repetition rate, scan line speed and laser fluency were set to 100µm, 20Hz, 100µms-1 and 17.9Jcm-2, respectively, as the established conditions for analysis of standards and samples. By using these conditions, limits of detection, estimated considering B+3s (where B is the value of the blank and s is the standard deviation of 10 measurements of the blank), ranged from 0.09µgg-1 (208Pb) to 1.09 (53Cr) and 0.05µgg-1 (208Pb) to 2.10 (53Cr) for calibration with and without 13C as internal standard (IS). In spite to the use of nylon for matrix matching of different polymeric matrices, the normalization with 13C as IS was also evaluated. The precision of the method is relatively good (RSD<20%), and the accuracy of the method, evaluated by analysis of certified reference materials (CRM) and by comparison with results obtained from solution analysis by ICP-MS after sample decomposition by microwave induced combustion (MIC) is relatively good. The suitability of the proposed method resulted in direct and reliable analyses of polymer samples with a simplified or unnecessary sample preparation step. In addition, the calibration with dried droplet reference solutions may be considered a promising procedure in view of its advantages to other forms of calibration, as the use of CRM or the preparation of synthetic standards. The use of porous nylon disks spiked with reference solutions for calibration is the main advantage of the present work.

External calibration strategy for trace element quantification in botanical samples by LA-ICP-MS using filter paper.

The use of reference solutions dispersed on filter paper discs is proposed for the first time as an external calibration strategy for matrix matching and determination of As, Cd, Co, Cr, Cu, Mn, Ni, Pb, Sr, V and Zn in plants by laser ablation-inductively coupled plasma mass spectrometry (LA-ICP-MS). The procedure is based on the use of filter paper discs as support for aqueous reference solutions, which are further evaporated, resulting in solid standards with concentrations up to 250 µg g(-1) of each element. The use of filter paper for calibration is proposed as matrix matched standards due to the similarities of this material with botanical samples, regarding to carbon concentration and its distribution through both matrices. These characteristics allowed the use of (13)C as internal standard (IS) during the analysis by LA-ICP-MS. In this way, parameters as analyte signal normalization with (13)C, carrier gas flow rate, laser energy, spot size, and calibration range were monitored. The calibration procedure using solution deposition on filter paper discs resulted in precision improvement when (13)C was used as IS. The method precision was calculated by the analysis of a certified reference material (CRM) of botanical matrix, considering the RSD obtained for 5 line scans and was lower than 20%. Accuracy of LA-ICP-MS determinations were evaluated by analysis of four CRM pellets of botanical composition, as well as by comparison with results obtained by ICP-MS using solution nebulization after microwave assisted digestion. Plant samples of unknown elemental composition were analyzed by the proposed LA method and good agreement were obtained with results of solution analysis. Limits of detection (LOD) established for LA-ICP-MS were obtained by the ablation of 10 lines on the filter paper disc containing 40 µL of 5% HNO3 (v v(-1)) as calibration blank. Values ranged from 0.05 to 0.81  µg g(-1). Overall, the use of filter paper as support for dried aqueous standards showed to be a useful strategy for calibration and plant analysis by LA-ICP-MS.