Reference 1. Grupo de Análise Instrumental Aplicada, Procedimentos Preparo de Amostras empregando Radiação Microondas, 2006.

Transcription

1 Preface This manual contains procedures proposed in the literature for microwave-assisted digestion of organic and inorganic samples. The literature search was based on papers published in 2006 and 2007, because previous years were covered in the first version of this manual [1]. Procedures employing microwave ovens designed for domestic use were not included for safety reasons. On the other hand, digestion procedures using flow-based systems were also not included because of the lack of commercial equipments that would make them available for laboratories performing routine analysis. The compilation was focused on developed procedures using commercial microwave ovens designed for laboratory applications. The main focus was put on inorganic elemental analysis, but some extraction procedures and procedures applicable for speciation analysis were also included as important strategies that certainly will have a fast growing in the coming years. The compilation is not comprehensive, but reflects the experience of the Group of Applied Instrumental Analysis (GAIA, Department of Chemistry, Federal University of São Carlos, and Embrapa Cattle- Southeast, São Carlos, SP, Brazil) and of the Group of Environmental Analytical Chemistry (Department of Chemistry, Federal University of Santa Maria, Santa Maria, RS, Brazil). However, it must be emphasized that the listed procedures were not tested in the authors laboratories and the authors cannot assume any responsibility about safety aspects. ATTENTION: The experimental work with concentrated acids at high pressures and temperatures is dangerous and may expose the analyst to critical safety conditions.

2 The authors intend to follow this series of compilations about microwave-assisted procedures with a publication titled Sample Preparation Information Newsletter, but the periodicity of this publication and its publication either in paper or in a digital medium is still being discussed. All work was made by the following members of both groups: Group of Applied Instrumental Analysis (GAIA, UFSCAR, and Embrapa Cattle-Southeast, SP, Brazil): Adriana Alice de Oliveira, Allen Lopes de Barros, Amália Geiza Gama Dionísio, Ana Rita de Araujo Nogueira, Carla Maira Bossu, Daniela Schiavo, Edenir Rodrigues Pereira Filho, Eveline de Abreu Menezes, Fernanda Santiago Chaves, Gilberto Batista de Souza, Joaquim de Araújo Nóbrega, Juliana Aparecida Ferreira, Kelber dos Anjos de Miranda, Larissa Macedo dos Santos, Marcos da Silva Gomes, Mário Henrique Gonzalez, Rodolfo Carapelli, Silmara Rossana Bianchi, Silvéria Neves de Paula e Souza, Simone Reder Matos Neves e Wladiana Oliveira Matos. Group of Environmental Analytical Chemistry UFSM, Santa Maria, RS Brazil): Cezar Augusto Bizzi, Érico Marlon de Moraes Flores, Fabiane Goldschmidt Antes, Juliana Severo Fagundes Pereira e Paola de Azevedo Mello Reference 1. Grupo de Análise Instrumental Aplicada, Procedimentos Preparo de Amostras empregando Radiação Microondas, (CD-ROM)

3 Comparative studies of the sample decomposition of green and roasted coffee for determination of nutrients and data exploratory analysis Amorim Filho, V. R., Polito, W. L., Gomes Neto, J. A., Journal the Brazilian Chemical Society, 18 (1), 47-53, 2007 The contents of some nutrients in 35 Brazilian green and roasted coffee samples were determined by flame atomic absorption spectrometry (Ca, Mg, Fe, Cu, Mn, and Zn), flame atomic emission photometry (Na and K) and Kjeldahl (N) after preparing the samples by wet digestion procedures using i) a digester heating block and ii) a conventional microwave oven system with pressure and temperature control. The accuracy of the procedures was checked using three standard reference materials (National Institute of Standards and Technology, SRM 1573a Tomato Leaves, SRM 1547 Peach Leaves, SRM 1570a Trace Elements in Spinach). Analysis of data after application of t-test showed that results obtained by microwaveassisted digestion were more accurate than those obtained by block digester at 95% confidence level. Additionally to better accuracy, other favorable characteristics found were lower analytical blanks, lower reagent consumption, and shorter digestion time. Exploratory analysis of results using Principal Component Analysis (PCA) and Hierarchical Cluster Analysis (HCA) showed that Na, K, Ca, Cu, Mg, and Fe were the principal elements to discriminate between green and roasted coffee samples. Type of sample: green and roasted coffee Sample amount: g Microwave oven (model): Perkin-Elmer-Anton Paar Multiwave (Graz, Austria). Vessel material: TFM (Teflon Fluor Modified) Heating: Dig. A. Step 1: ramp time 3 min, initial power (100 W) and final power (800 W). Step 2: 5 min, initial power (800 W) and final power (800

4 W). Step 3: ramp time 2 min, initial power (1000 W) and final power (1000 W). Step 4: 8 min, initial power (0 W) and final power (0 W). Number of samples simultaneously digested: 8 Reagents: 6.0 ml concentrated HNO ml H 2 O 2 Pretreatment general aspects: A mass of green coffee was added to the polycarbonate container until approximately half of its total volume with the magnetic bar, which tightly closed, was adapted to the support and immersed in liquid nitrogen. Samples were pulverized by the impact between coffee beans and the magnetic bar submitted to an oscillating magnetic field of 20 impacts s -1. The cryogenic mill program consisted of 2 steps: 5 min of pre-cool and 2 min of mill. One of the selected samples (sample number identification 1) was also ground using a Tecnal TE-648 Willye-type mill (Piracicaba, Brazil) without a previous sample freezing in order to verify eventual contamination by mill components. This sample was identified as number 2. Samples were oven-dried at 60 o C for 12 h. Detection technique: flame atomic absorption spectrometry, flame atomic emission spectrometry and Kjeldahl Analytes: Ca, Fe, K, Mg, Cu, Mn, Na and Zn

5 Direct determination of arsenic in beer by electrothermal atomic absorption spectrometry with deuterium background correction (D2-ET-AAS) Husakova, L., Cernohorsky, T., Sramkova, J. and Vavrusova, L., Food Chemistry, 105 (1), , 2007 We describe here a method for the direct determination of As in beer by D2-ET-AAS, using Pd modifier, the atomization from platform and insertion of a cooling step before atomization. This method results in a 40% increase of sensitivity in peak-height measurements. Pd was found to be the most advantageous chemical modifier for the elimination of phosphate interference compared to Ni or Pt + citric acid. In addition, Pd is able to stabilize As at charring temperatures of 1500 o C and further addition of V, Mg or Sr have no influence. Addition of the modifier to standards and samples made possible the use of matrix-free standard solutions for attaining accurate analysis of diluted samples. The accuracy was checked by the comparison of results of direct analysis of beer samples by the proposed method with those found for microwave-digested samples measured by an inductively coupled plasma orthogonal acceleration timeof-flight mass spectrometer (ICP-TOFMS) method. The accuracy was also confirmed by the analysis of certified reference samples. Type of sample: beer Sample amount: 5.0 ml Microwave oven (model): Microwave system Speedwave TM MWS-3 +. The maximum total output of the microwave generator is 1450 W. Vessel material: PTFE Heating: Step 1: 5 min at 150 o C and 50% power. Step 2: 5 min at 220 o C and 70% power. Step 3: 5 min at 100 o C and 10% power. Number of samples simultaneously digested: not informed

6 Reagents: 6 ml of HNO 3 (65% v/v) Pretreatment general aspects: - Detection technique: ICP-TOFMS Analytes: As

7 Effect of four bentonite samples on the rare earth element concentrations of selected Hungarian wine samples Tatár, E., Mihucz, V. G., Virág, I., Rácz, L. and Záray, G., Microchemical Journal, 85 (1), , 2007 Rare earth elements (REEs) were detected and determined (except Eu, and in some cases Gd, Tb and Tm) in three Hungarian wine samples Királyleányka, Blauer Portugieser and Merlot (2004 vintage) from the Eger viticulture area by double focusing inductively coupled plasma sector field mass spectrometry (ICP-SF-MS) in low resolution mode (R=300). The REE average concentrations of the samples determined after microwave-assisted digestion were in the pg/cm 3 concentration range. According to the results, among these grapes grown on volcanic slopes, the REEs uptake by the Királyleányka and Blauer Portugieser seemed to be more inhibited. Four, commercially available bentonite samples fibrous (Gelbenton), protein containing (Evergel), and two Na bentonites (BW200 and Tükrös) were used for wine clarifying. Gelbenton altered the less the REE concentrations of the wine samples. The lowest increase ( times) was established for the Merlot red wine sample. Type of sample: wine Sample amount: 2 ml Microwave oven (model): Multiwave Paar Physica device (Paar, Austria). Vessel material: quartz Heating: 40 min at 1000 W (nominal power value per six bombs) achieved with a ramp of 50 W/min. Number of samples simultaneously digested: 6 Reagents: 2 ml HNO 3 65% (v/v) Pretreatment general aspects: Samples were filtered through Millex PDVF filters of 0.2 μm pore size

8 Detection technique: ICP-SF-MS Analytes: Rare earth elements (REEs)

9 Influence of different bentonites on the rare earth element concentrations of clarified Romanian wines Mihucz, V. G., Done, C. J., Tatár, E., Virág, I., Záray, G. and Baiulescu, E. G., Talanta, 70 (5), , 2006 The rare earth element (REE) concentrations of 19 Romanian young wine samples originating from the Dealurile Moldovei viticulture area were determined by double focusing inductively coupled plasma mass spectrometry (DF-ICP-MS) after microwave-assisted digestion with nitric acid. The determination of Eu was hampered by the BaO molecular interference. Generally, the red wine samples were more concentrated for REEs than the white wine samples studied. The REE concentrations of the four bentonites (Gelbenton, Evergel, BW200, Tükrös) determined after their fusion were higher by three orders of magnitude than those of the wine samples. After a simulated wine purification process performed with these bentonite samples and a red and white pool samples, the REE concentrations of the clarified wine samples increased by times for red, and times for white wines in case of the fibrous bentonite sample (Gelbenton), by about 2 5 times in case of the bentonite containing ovalbumin, caseine and gelatine (Evergel), meanwhile this factor was about for Na bentonite powder samples (BW200, Tükrös). On basis of the chemometric evaluation using the REE concentrations as input data, the majority of the Feteasca wines belonged to the same cluster as well as the two Cabernet Sauvignon to another subcluster. The adequate choice of the bentonite may allow the use of REEs as fingerprints for determining the wine provenance. Type of sample: white and read wine samples Sample amount: 2 ml Microwave oven (model): Multiwave Paar Physica (Anton Paar, Austria)

10 Vessel material: quartz Heating: 40 min at 1000 W achieved with a ramp of 50 W/min. Number of samples simultaneously digested: 6 Reagents: 2 ml of HNO 3 65% (v/v) Pretreatment general aspects: 2 ml of samples were previously filtered through Millex PDVF filters of 0.2 μm. Detection technique: double focusing ICP-MS. Analytes: rare earth elements

11 Arsenic in marine tissue The chalenging problems to electrothermal and hydride generation atomic absorption spectrometry Karadjova, I. B., Petrov, P. K., Serafimovski, I., Stafilov, T. and Tsalev, D. L., Spectrochimica Acta Part B, 62 (3), , 2007 Analytical problems in determination of arsenic in marine tissues are addressed. Procedures for the determination of total As in solubilized or extracted tissues with tetramethylammonium hydroxide and methanol have been elaborated. Several typical lyophilized tissues were used: NIST SRM 1566a Oyster Tissue, BCR-60 CRM Trace Elements in an Aquatic Plant Lagarosiphon major), BCR-627 Forms of As in Tuna Fish Tissue, IAEA- 140/TM Sea Plant Homogenate, NRCC DOLT-1 Dogfish Liver and two representatives of the Black Sea biota, Mediterranean mussel (Mytilus galloprovincialis) and Brown algae (Cystoseira barbata). Tissues (nominal 0.3 g) were extracted in tetramethylammonium hydroxide (TMAH) 1 ml of 25% m/v TMAH and 2 ml of water) or 5 ml of aqueous 80% (v/v) methanol (MeOH) in closed vessels in a microwave oven at 50 C for 30 min. Arsenic in solubilized or extracted tissues was determined by electrothermal atomic absorption spectrometry (ETAAS) after appropriate dilution (nominally to 25 ml, with further dilution as required) under optimal instrumental parameters (pyrolysis temperature 900 C and atomization temperature 2100 C) with 1.5 μg Pd asmodifier on Zr Ir treated platform. Platforms have been pre-treated with 2.7 μmol of zirconium and then with 0.10 μmol of iridium which served as a permanent chemical modifier in direct ETAAS measurements and as an efficient hydride sequestration medium in flow injection hydride generation (FI-HG) ETAAS. TMAH and methanol extract % and % of As from CRMs. Various calibration approaches have been considered and critically evaluated. The effect of species-dependent slope of calibration

12 graph or standard additions plot for total As determination in a sample comprising of several individual As species with different ETAAS behavior has been considered as a kind of intrinsic element speciation interference that cannot be completely overcome by standard additions technique. Calibration by means of CRMs has given only semi-quantitative results. The limits of detection (3σ) were in the range mg/kg As dry weight (wt.) for direct ETAAS analysis of extracts in both TMAH and MeOH. Within-run precision (RSD, %) was 5 15% and 7 20 % for TMAH and MeOH extracts at As levels 4 50 mg/kg dry wt., respectively. The hydride active fraction of As species in extracts, i.e. the sum of oxicologically-relevant arsenic species (inorganic As(III), inorganic As (V), monomethylarsonate (MMA) and imethylarsinate (DMA) was determined by FI-HG ETAAS in diluted tissue extracts. Arsine, monomethylarsine and dimethylarsine were generated from diluted TMAH and MeOH extracts in the presence of mol/l hydrochloric acid and mol/l L-cysteine. Collection, pyrolysis and atomization temperatures were 450, 500, 2100 and 2150 C, respectively. The LODs for the determination of hydride forming fraction arsenite + arsenate + MMA + DMA) in TMAH and MeOH extracts were in the range mg/kg As dry wt. Within-run precision (RSD, %) was 3 12% and 3 7% for MAH and methanol extracts at As levels mg/kg dry wt., respectively. Results for the hydride forming fraction of As in TMAH and MeOH extract as % from the certified value for total As (for CRMs) or vs. the total As in TMAH extract (for real marine samples) are generally in agreement. Type of sample: marine tissue Sample amount: 0.3 g Microwave oven (model): Model MARS 5 (CEM Corporation, Matthews, NC, USA)

13 Vessel material: Plastic CEM extraction vessel Heating: Procedure A: 50 ºC (10min ramp time- 20 min hold time); Procedure B: 50º C (10 min ramp time- 10 min hold time) Number of samples simultaneously digested: not informed Reagents: Procedure A: Extraction 1: 1 ml of aqueous 25% (m/v) solution of tetramethylammonium hydroxide (TMAH); Extraction 2: 5 ml of 80% (v/v) methanol. Procedure B: 0.3 ml of aqueous 25% (m/v) solution of TMAH. Pretreatment general aspects: Samples were left for 30 min, capped and placed in the rotor of MW extraction module Detection technique: ETAAS and FI-HG-ETAAS Analytes: As

14 Comparison of laser ablation, electrothermal vaporization and solution nebulization for the determination of radionuclides in liquid samples by inductively coupled plasma mass spectrometry Grinberg, P., Yang, L., Mester, Z., Willie, S. and Sturgeon, R.E., Journal of Analytical Atomic Spectrometry, 21 (11), , 2006 The performance of solution nebulization (SN), electrothermal vaporization (ETV) and laser ablation (LA) of dried micro-droplets as sample introduction systems for ICP-MS are compared for the determination of several radionuclides in digested biological tissue, nearshore sea-water and river water. Samples were subjected to a Ca 3 (PO 4 ) 2 co-precipitation preconcentration prior to analysis. Each introduction system possesses unique advantages and disadvantages. ETV accommodates samples having higher dissolved solids content; consequently, for SN and LA, sample concentrates require additional dilution by 50- and 10-fold, respectively. ETV and LA achieved similar sensitivities and limits of detection, the latter ranging from to pg/ml. Although SN provides the best precision (2% RSD versus 7 and 8% for ETV and LA, respectively), formation of uranium hydride can be reduced at least 100-fold using LA of dried micro-droplets of samples. The accuracy of the method was validated by determination of U and Th in NIST SRM 1566b Oyster Tissue, NRC CRM CASS-4 Nearshore Seawater and SLRS-4 Riverine Water and via spike recoveries for Pu. Type of sample: tissue Sample amount: 0.25 g Microwave oven (model): MDS 2100 (CEM Corporation, Matthews, NC, USA) Vessel material: Teflon

15 Heating: pressure of 8.16 atm for 30 min. After cooling, 200 µl of H 2 O 2 (30%) was added, the vessels were recapped and heated again using the same microwave program. Number of samples simultaneously digested: not informed Reagents: 7 ml HNO 3 conc µl H 2 O 2 30% (v/v) Pretreatment general aspects: - Detection technique: ICP-MS Analytes: Th, U and Pu

16 Determination of arsenic species in marine samples by HPLC-ICP-MS Hirata, S., Toshimitsu, H. and Aihara, M., Analytical Sciences, 22 (1), 39-43, 2006 Arsenic speciation analysis in marine samples was performed using high performance liquid chromatography (HPLC) with ICP-MS detection. The separation of eigth arsenic species viz. arsenite (As III ), monomethylarsonic acid (MMA), dimethylarsinic acid (DMA), arsenate (As V ), arsenobetaine, trimethylarsine oxide (TMAO), arsenocholine and tetramethylarsonium ion (TeMAs) was achived on a Shiseido Capcell Pak C 18 column by using an isocratic eluent (ph 3.0), in wich condition A III and MMA were co-eluted. The entire separation was accoplished in 15 min. The detection limits for 8 arsenic species by HPLC/ICP-MS were in range of μg L -1 based on 3δ of blank response (n = 9). The precision was calculated to be % (RSD) for all eight species. The method them succesfully applied to several marine samples e.g., oyster, scallop, fish, and shrimps. For the extraction of arsenic species from seafood products, the low power of microwave digestion was employed. The extraction efficiency was in the range of %. Total arsenic concentrations were analyzed by using the microwave acid digestion. The total arsenics in the certified reference materials (DORM-2 and TORT-2) were analyzed and agreed with the certified values. The concentrations of arsenics in marine samples were in the range μg/g. Type of sample: oyster, scallop, fish and shrimps Sample amount: g Microwave oven (model): MCS 950 (Prolabo, France) Vessel material: Teflon Heating: 10 min at 50 W Number of samples simultaneously digested: not informed

17 Reagents: 10 ml H 2 O Pretreatment general aspects: the samples were dried previously the microwave extraction procedure. Detection technique: HPLC/ICP-MS Analytes: arsenite (As III ), monomethylarsonic acid (MMA), dimethylarsinic acid (DMA), arsenate (As V ), arsenobetaine, trimethylarsine oxide (TMAO), arsenocholine and tetramethylarsonium ion (TeMAs).

18 Determination of 30 elements in colorectal biopsies by sector field inductively coupled plasma mass spectrometry: method development and preliminary baseline levels Bocca, B., Lamazza, A., Pino, A., Masi, E., Iacomino, M., Mattei, D., Rahimi, S., Fiori, E., Schillaci, A., Alimonti, A. and Forte, G. Rapid Communications in mass spectrometry, 21 (11), , 2007 An analytical procedure applicable to restricted sample sizes was developed and applied to the analysis of 30 chemical elements in colorectal biopsies of healthy patients. Acidic microwave digestion processed 10mg of tissue at 80 o C in 15 ml polystyrene liners. The digests were diluted to a volume of 2 ml with high-purity water and directly analyzed by sector field inductively coupled plasma mass spectrometry without further specimen handling. A careful selection of isotopes and instrumental resolution permitted the quantification in a single analytical sequence both of the elements present at parts per trillion and of those at parts per million. The accuracy calculated on BCR 184 ranged from %, the recoveries of the biopsy material was in the range %, the precision was < 10%, and the blank levels were much below those expected in biopsy samples. The metal concentrations (on a dry-weight basis) in colorectal normal tissue showed a large range of variation: Ag, Au, Be, Bi, Co, Li, Sb, Tl, V,Wand Zr were below 50 ng/g; As, Ba, Cd, Cr, Cs, Hg, Mo, Ni, Pb, Se and Sn were distributed from 100 to 500 ng/g; Al, Cu, Fe, Mn, Sr and Zn were from a few mg/g to 100 mg/g; and Ca and Mg were at a level of 1000 mg/g. These data represent the first attempt to achieve an elemental profile in the colorectal mucosa of healthy patients as baseline level measurements for studies focused on the imbalance of chemical elements in diseased mucosa. Type of sample: colorectal biopsies

19 Sample amount: g Microwave oven (model): Milestone Ethos 900-Mega II oven (FKV, Milestone, Bergamo, Italy) loading a MultiPREP 80 rotor (FKV Milestone) Vessel material: not informed Heating: temperature ramp from 25 to 808 o C, for a total digestion time of about 2 h Number of samples simultaneously digested: capacity of 79 liners plus Reagents: 0.5 ml of ultrapure HNO 3 Pretreatment general aspects: The tissues were dried at 105 o C overnight, with water content ranging between 59 and 84% Detection technique: SF-ICP-MS Analytes: Ag, As, Au, Be, Bi, Co, Li, Sb, Tl, V, Zr, Ba, Cd, Cr, Cs, Hg, Mo, Ni, Pb, Se, Sn, Al, Cu, Fe, Mn, Sr and Zn

20 Determination of Hg and Se in biological materials by chemical vapor generation electrothermal vaporization inductively coupled plasma mass spectrometry using isotope dilution calibration after microwaveassisted digestion with aqua regia Vieira, M. A., Ribeiro, A. S., Dias, L. F. and Curtius, A. J., Journal of Brazilian Chemical Society, 17 (5), , 2006 A method for the determination of Hg and Se in biological materials by chemical vapor generation electrothermal vaporization inductively coupled plasma mass spectrometry (CVG-ETV-ICP-MS) using isotope dilution calibration after acid digestion is proposed. The samples were digested with aqua regia in a microwave oven. The isotope ratios used for quantification were: 201 Hg/ 202 Hg and 77 Se/ 82 Se. A NaBH 4 solution stabilized with NaOH was used as reducing agent. The retention and vaporization temperatures in the graphite tube were 150 and 2000 ºC, respectively. Six certified biological materials were analyzed and the obtained concentrations were in good agreement with the certified values according to the t-test for a confidence level of 95%. The detection limits in the sample were 0.7 and 3 ng/g, for Hg and Se respectively. The method is precise, accurate and adequate for the analysis of biological samples in routine and demonstrates the feasibility of using isotope dilution for the proposed system. Type of sample: biological materials (human hair, lyophilized pig kidney, dogfish liver, dogfish muscle and lobster hepatopancreas) Sample amount: 0.25 g Microwave oven (model): Ethos Plus (Milestone Corporation, Sorisole, Italy) Vessel material: PTFE Heating: 5 steps microwave oven temperature program was adopted 2 min at 50 C and 400 W maximum power; 2 min at 50 C and 200 W

21 maximum power; 6 min at 80 C and 550 W maximum power; 5 min at 80 C and 1000 W maximum power; 7 min at 160 C and 1000 W maximum power Number of samples simultaneously digested: not informed Reagents: 3.5 ml of aqua regia + 1 ml of deionized water Pretreatment general aspects: - Detection technique: CVG-ETV-ICP-MS Analytes: Hg and Se

22 Determination of soluble toxic arsenic species in alga samples by microwave-assisted extraction and high performance liquid chromatography hydride generation inductively coupled plasmaatomic emission spectrometry Salgado, S. G., Nieto, M. A. Q. and Simón, M. M. B., Journal of Chromatography A, 1129 (1), 54-60, 2006 A microwave-based procedure for arsenic species extraction in alga samples (Sargassum fulvellum, Chlorella vulgaris, Hizikia fusiformis and Laminaria digitata) is described. Extraction time and temperature were tested in order to evaluate the extraction efficiency of the process. Arsenic compounds were extracted in 8ml of deionised water at 90 ºC for 5 min. The process was repeated three times. Soluble arsenic compounds extracted accounted for about 78 98% of total arsenic. The results were compared with those obtained in a previous work, where the extraction process was carried out by ultrasonic focussed probe for 30 s. Speciation studies were carried out by high performance liquid chromatography hydride generation inductively coupled plasma-atomic emission spectrometry (HPLC-HG-ICP-AES). The chromatographic method allowed us to separate As(III), As(V), monomethylarsonic acid and dimethylarsinic acid in less than 13 min. The chromatographic analysis of the samples allowed us to identify and quantify As(V) in Hizikia sample and Sargasso material, while the four arsenic species studied were found in Chlorella sample. In the case of Laminaria sample, none of these species was identified by HPLC-HG-ICP-AES. However, in the chromatographic analysis of this alga by HPLC-ICP-AES, an unknown arsenic species was detected. Type of sample: alga (Sargassum fulvellum, Chlorella vulgaris, Hizikia fusiformis and Laminaria digitata) Sample amount: 0.2 g for extraction and 0.25 g for digestion

23 Microwave oven (model): MARS 5 Microwave oven (CEM Corporation, Matthews, NC, USA) Vessel material: Teflon and Pyrex Heating: 90 ºC was applied for 5 min for extraction procedure and 30 min at atm and 210 ºC for digestion procedure. Number of samples simultaneously digested: not informed Reagents: 8 ml of deionised water for extraction procedure and 10 ml of HNO 3 conc. for digestion procedure. Pretreatment general aspects: Hijiki algawas triturated in a mill to a particle size of 125 μm and Laminaria capsules were opened and placed in a polyethylene bottle before the analytical treatment. Detection technique: HPLC-HG-ICP-AES Analytes: arsenic species

24 Digestion of biological materials using the microwave-assisted sample combustion technique Mesko, M. F., Moraes, D. P., Barin, J. S., Dressler, V. L., Knapp, G. and Flores, E. M. M., Microchemical Journal, 82 (2), , 2006 In this study a procedure for sample digestion based on sample combustion assisted by microwave radiation is proposed. Combustion is started by microwave radiation in the presence of oxygen under pressure using ammonium nitrate as aid for ignition. The system was adapted in a microwave oven with quartz closed vessels. A quartz piece is used simultaneously as a sample holder and as protection to the cap of quartz vessel from the flame generated in the combustion process. Sample was pressed into a pellet and placed on a disc paper in the holder and 50 μl of 50% m/v ammonium nitrate solution was added. The influence of the absorption solution (diluted and concentrated nitric acid or water) on the recoveries for Cu and Zn was evaluated. About 3 s of microwave irradiation was necessary to start the combustion. The combustion process was evaluated in relation to the influence of sample mass on the ignition time, combustion time and maximum operation pressure. Bovine liver, milk powder and oyster tissue certified reference materials were used to evaluate the accuracy of the procedure for determination of copper and zinc. Good agreement for zinc (96% to 103%) was obtained from bovine liver certified reference material when microwave combustion and microwave combustion followed by reflux were used to sample decomposition, even if water was used for absorption of analyte. For copper, the combustion followed by reflux of 5 min allows an agreement from 96% to 100%. Similar results were obtained for oyster tissue samples. However, for milk powder good agreement close to 100% was obtained only if 4 mol/l HNO 3 was used with a reflux step. Results from the

25 proposed procedure were also compared to those from conventionally used procedures for biological samples decomposition, such as wet digestion in open vessels and microwave-assisted digestion in closed vessels. The advantages of this procedure include the complete sample decomposition in less time than other procedures and the acid consumption was always lower than 2%. Another advantage is the low residual carbon content, less of 1.4% without reflux and less than 0.3% with the reflux step and the possibility of use of diluted acid as absorbing solution. Moreover, the new holder allows an effective protection of the vessel cap to burnt high masses. Type of sample: Bovine liver, milk powder and oyster tissue certified reference materials Sample amount: 0.5 g Microwave oven (model): Multiwave 3000 (Anton Paar) Vessel material: Quartz Heating: The microwave irradiation program used for the combustion procedure was as follows: 1) 1400 W for 60 s, 2) 1400 W for 5 min (optional step for reflux), and 3) 0 W for 20 min for cooling if step 2 was applied. During steps 1 and 2, the cooling fan was selected at level 2 (level 3 was applied only for cooling). Number of samples simultaneously digested: not informed Reagents: 6 ml HNO 3 Pretreatment general aspects: samples between 50 and 500 mg were pressed and weighed directly on the filter paper. Detection technique: FAAS Analytes: Cu and Zn

26 Element fingerprinting of marine organisms by dynamic reaction cell inductively coupled plasma mass spectrometry Cubadda, F., Raggi, A. and Coni, E., Analytical and Bionalytical Chemistry, 384 (4), , 2006 A method for the determination of sixteen elements (Al, As, Cd, Co, Cr, Cu, Fe, Hg, Mn, Mo, Ni, Pb, Se, Sn, V, Zn) in seafood by dynamic reaction cell inductively coupled plasma mass spectrometry (ICP DRC MS) is presented. A preliminary study of polyatomic interferences was carried out in relation to the chemical composition of marine organisms belonging to different taxa. Acid effects and other matrix effects in marine organisms submitted to closed-vessel microwave digestion were investigated as well. Ammonia was the reactive gas used in the DRC to remove polyatomic ions interfering with 27 Al, 52 Cr, 56 Fe and 51 V. Optimal conditions for the simultaneous determination of analytes were identified in order to develop a fast multielement method. A suite of real samples (mussels and various fish species) were used during method development along with three certified reference materials: BCR CRM 278R (mussel tissue), BCR CRM 422 (cod muscle) and DORM-2 (dogfish muscle). The proposed analytical approach can be used in conjunction with suitable chemometric procedures to address quality and safety issues in aquaculture and fisheries. As an example, a case study is described in which mussels from three farming sites in the Venice Lagoon were distinguished by multivariate analysis of element fingerprints. Type of sample: Biological Sample amount: 2.0 g Microwave oven (model): Ethos Pro microwave labstation (Milestone Corporation, Sorisole, Italy) Vessel material: PTFE

27 Heating: Temperature control during microwave irradiation allowed automatic continuous adjustment of power output and the accomplishment of the following temperature profile: 5 min ramp to 120 C, 5 min at 120 C, 5 min ramp to 190 C, 15 min at 190 C. The digested samples were kept refrigerated at 4 C. Number of samples simultaneously digested: not informed Reagents: 5 ml HNO ml H 2 O ml H 2 O (sample), and 3 ml HNO ml H 2 O ml H 2 O (certified reference materials) Pretreatment general aspects: - Detection technique: ICP-MS Analytes: Al, As, Cd, Co, Cr, Cu, Fe, Hg, Mn, Mo, Ni, Pb, Se, Sn, V and Zn

28 Evaluation of toxic metals in biological samples (scalp hair, blood and urine) of steel mill workers by electrothermal atomic absorption spectrometry Afridi, H. I., Kazi, T. G., Jamali, M. K., Kazi, G. H., Arain, M. B., Jalbani, N., Shar, G. Q. and Sarfaraz, R. A., Toxicology and Industrial Health, 22 (9), , 2006 The determination of toxic metals in the biological samples of human beings is an important clinical screening procedure. This study aimed to assess the possible influence of environmental exposure on production workers (PW) and quality control workers (QCW) of a steel mill, all male subjects aged years. In this investigation, the concentrations of Pb, Cd, Ni and Cr were determined in biological samples (blood, urine and scalp hair samples) from these steel mill workers in relation to controlled unexposed healthy subjects of the same age group. After pre-treatment with nitric acid-hydrogen peroxide, the samples were digested via a microwave oven, and for comparison purposes, the same samples were digested by the conventional wet acid digestion method. The samples digested were subjected to graphite furnace atomic absorption spectrometry (GF AAS). To assess the reliability of these methods, critical factors, such as detection limit(s), calibration range(s), accuracy and precision, were studied. Quality control for these procedures was established with certified sample of human hair, urine and whole blood. The results indicate that the level of lead, cadmium and nickel in scalp hair, blood and urine samples were significantly higher in both groups of exposed workers (QW and PW) than those of the controls. The possible connection of these elements with the etiology of disease is discussed. The results also show the need for immediate improvements in workplace ventilation and industrial hygiene practices.

29 Type of sample: scalp hair, blood and urine Sample amount: 0.2 g of scalp hair, 0.5 ml of blood and 1 ml of urine Microwave oven (model): not informed Vessel material: Teflon PFA Heating: 250 W for 5 min for blood and urine, and 250 W for 15 min for hair samples. Number of samples simultaneously digested: not informed Reagents: 2 ml of concentrated HNO 3 and 1 ml of H 2 O 2 30% (v/v) Pretreatment general aspects: - Detection technique: GF AAS Analytes: Pb, Cd, Ni and Cr

30 Highly improved sensitivity of TS-FF-AAS for Cd(II) determination at ng L -1 levels using a simple flow injection minicolumn preconcentration system with multiwall carbon nanotubes Tarley, C. R. T., Barbosa, A. F., Segatelli, M. G., Figueiredo, E. C. and Luccas, P. O., Journal of Analytical Atomic Spectrometry, 21 (11), , 2006 A new method for cadmium determination at ng L -1 levels is described. The method is based on the on-line coupling of a flow preconcentration system using multiwall carbon nanotubes (MWCNT) as sorbent with TS-FF-AAS determination. Cadmium preconcentration was at ph 4.9 onto an MWCNT minicolumn (30 mg) for 2 min at a 5.0 ml min -1 flow rate. The elution step is performed by using 0.5 mol/l HNO 3 and the cadmium desorbed is directly pumped to a TS-FF-AAS. All experimental parameters that play important roles in system performance were evaluated and optimized by means of fractional factorial designs and response surface methodology. The excellent characteristics of MWCNT as sorbent, mainly owing to its high surface area, make it possible to obtain a preconcentration factor of 51-fold, thus improving the detection and quantification limits in TS-FF-AAS, 11.4 and 38.1 ng/l, respectively. When the flow preconcentration system, FI-TS-FF-AAS, was compared with FAAS alone, an increase in the sensitivity of 640-fold was obtained. The calibration graph was linear with a correlation coefficient higher than from 38.1 to 1250 ng/l. Repeatability of the measurements (n = 10), assessed as relative standard deviation (RSD), was found to be 6.5 and 2.1% for cadmium concentrations of 100 and 1000 ng L -1, respectively. Important parameters to characterize the flow preconcentration system were also evaluated, the consumption index being ml, the concentration efficiency 25.5 min -1 and the sample throughput 20 samples per hour. In

31 order to demonstrate the accuracy of the system, addition and recovery studies in water samples (mineral water, tap water and river water) and cigarette samples were carried out. Moreover, for the same purpose, cadmium was determined in certified biological materials (Bovine Liver and Rye Grass), giving an average result in close agreement with the certified value. Type of sample: Bovine Liver, Rye Grass and cigarette samples Sample amount: 0.20 g Microwave oven (model): microwave oven Milestone Corporation, Sorisole, Italy Vessel material: not informed Heating: samples were digested using two heating steps in a microwave oven: 5 min at 400 W and 5 min at 700 W. After digestion, solutions were heated on a hot plate to near dryness. Number of samples simultaneously digested: two Reagents: 10 ml HNO 3 65% (v/v)+ 4 ml 30% (m/v) H 2 O 2 Pretreatment general aspects: - Detection technique: TS-FF-AAS Analytes: Cd

32 Manganese determination by GFAAS in feces and fish feed slurries Loureiro, V. R., Saleh, M. A. D., Moraes, P. M., Neves, R. C. F., Silva, F. A., Padilha, C. C. F., Padilha, P. M., Journal the Brazilian Chemical Society, 18 (6), , 2007 This paper presents a simple, fast and sensitive method to determine manganese in samples of feces and fish feed by graphite furnace atomic absorption spectrometry (GFAAS) by the direct introduction of slurries into the graphite tube. The limits of detection (LOD) and quantification (LOQ) calculated for 20 readings of the blank of the standard slurries (0.50% m/v of feces or feed devoid of manganese) were 28 and 92 µg/kg for the standard feces slurries and 34 and 110 µg/kg for the standard feed slurries. The proposed method was applied in bioavailability studies of manganese in different fish feeds and their results proved compatible with those obtained for samples mineralized by acid digestion using microwave oven. Type of sample: feces and fish feed Sample amount: g Microwave oven (model): Model DGT 100, Provecto Analítica, Brazil Vessel material: PTFE Heating: Step 1: 300 W, 3 min. Step 2: 0 W, 2 min. Step 3: 450 W, 5 min. Step 4: 550 W, 5 min. Step 5: 650 W, 5 min. Step 6 (ventilation): 0 W, 5 min. Number of samples simultaneously digested: 6 Reagents: 2.5 ml HNO ml H 2 O 2 30% Pretreatment general aspects: The fish feces and feed samples were dried at 50 C in an oven with forced air circulation for 48 h and then cryogenically ground. Detection technique: GFAAS Analytes: Mn

33 Method for determination of selenium and arsenic in human urine by atomic fluorescence spectrometry Wieteha-Posłuszny, R., and Dobrowolska, J., Analytical Letters, 39 (15), , 2006 The study presents the method for simultaneous determination of selenium and arsenic in human urine by atomic fluorescence spectrometry (AFS). According to the procedure developed, a sample is first digested in the microwave system, then chemically treated in the flow through a hydride generation system, and finally exposed to measurements in a doublechannel atomic fluorescence spectrometer. It has been revealed that selenium and arsenic can be accurately determined with detection limit of 0.13 and 0.16 mg/l and repeatability (RSD) of 1.0 and 1.2%, respectively. The urine samples taken from a control group and from persons subjected to a special diet were analyzed. The obtained results proved that the method developed was capable of controlling reliably even slight changes of both elements in a wide range of their concentrations, and, as such, that it can be recommended to be used for clinical and toxicological purposes. Type of sample: human urine Sample amount: 0.5 ml Microwave oven (model): MARS 5 (CEM Corporation, Matthews, NC, USA) Vessel material: not informed Heating: The digestion condition for the microwave system was applied as 8 min for 960 W, 8 min for 960 W, and 8 min for 1080 W. After digestion, the sample solution was cooled in the air to 25 C and then blown under nitrogen flow for 10 min. At the end, a sample was transferred into a 25 ml volumetric flask, dosed by 12.5 ml of 6 mol/l HCl, and diluted to the mark with water.

34 Number of samples simultaneously digested: not informed Reagents: 7 ml HNO 3 Pretreatment general aspects: - Detection technique: AFS Analytes: As and Se

35 Monitoring trace elements in selected organs of Antarctic penguin (Pygoscelis adeliae) by plasma-based techniques Smichowski, P., Vodopivez, C., Muñoz-Olivas, R., and Gutierrez, A.M., Microchemical Journal, 82 (1), 1-7, 2006 A study was undertaken to evaluate the content and distribution of eight key elements, namely, As, Cd, Co, Cu, Hg, Mn, Pb and Se in liver, kidney and muscle of chick individuals of Adélie penguin (Pygoscelis adeliae). Samples were collected during the 2002/2003 austral summer season campaign around Jubany Station (Argentine scientific station), Potter Cove, King George Island. Solutions of organs were prepared by acid-assisted microwave (MW) digestion by employing HNO 3 and H Instrumental techniques selected to analyze the different tissues were inductively coupled plasma optical emission spectroscopy (ICP OES) and inductively coupled plasma mass spectrometry (ICP-MS). A wide range of elements retention capacity among the different organs was observed and the ranges ascertained are as follows (in µg/g): As, 0.5 (liver) 0.8 (muscle); Cd, <0.07 (muscle) 3.4 (kidney); Co, 0.07 (liver) 0.7 (muscle); Cu, 0.6 (muscle) 18 (liver); Hg, 0.2 (kidney) 2.7 (liver); Mn, 1.5 (muscle) 10 (liver); Pb, 0.1 (muscle) 2.0 (liver); Se, 3.0 (muscle) 8.4 (liver). The observed trend in metal accumulation in the three organs of chick penguins was in the order Cu>Mn>Se >>As>Co>Pb>>Cd>Hg. Levels of metals and metalloids were, in general terms, higher in liver that is a specific target organ for metal accumulation. This study aimed at contributing to the establishment of base-line data on potential pollutants of ecotoxicological interest in the Antarctic ecosystem. Type of sample: liver, kidney and muscle of penguin Sample amount: 0.35 g

36 Microwave oven (model): CEM MSP-1000 (CEM Corporation, Matthews, NC, USA) Vessel material: Teflon-PFA Heating: The MW program is: 1 min at 250 W, 1 min at 0 W, 5 min at 250 W, 5 min at 400 W and 5 min at 650 W. After cooling, a completely clear and homogeneous digest was observed and it was diluted to 25 ml with deionized water. Number of samples simultaneously digested: two Reagents: 4 ml HNO 3 conc ml H 2 O 2 (m/v) Pretreatment general aspects: Samples were defrosted in the laboratory, dried at 50 -C until constant weight and stored in a dark place (at room temperature) until their analysis. Samples were homogenized and ground to a fine powder in a tungsten carbide mortar. Detection technique: ICP OES and ICP-MS Analytes: Pb, Mn, Se, Ar, Cd, Co, Cu and Hg

37 Multi-element determination in raft mussels by fast microwaveassisted acid leaching and inductively coupled plasma-optical emission spectrometry Seco-Gesto, E. M., Moreda-Piñeiro, A., Bermejo-Barrera, A. and Bermejo- Barrera, P., Talanta, 72 (3), , 2007 Studies on the application of a short microwave irradiation cycle and the use of diluted acids to extract trace elements from raft mussel samples were developed. Multi-element determinations (Al, Ba, Cd, Cr, Cu, Fe, Mn, Pb, Sn, V and Zn) were carried out by inductively coupled plasmaoptical emission spectrometry (ICP-OES). Parameters such as acid/oxidizing reagents (diluted nitric acid, hydrochloric acid and hydrogen peroxide) concentrations, acid/oxidizing solution volume, temperature, ramp time and hold time for the microwave heating were simultaneously studied by using an experimental design approach. The optimum conditions have showed the sample pre-treatment of 10 mussel samples to less than 3.0 min when a microwave power of 600Wand a controlled temperature of 65 C were used. This time (hold time plus ramp time) is quite shorter than those reported for conventional microwave-assisted acid digestion procedures. Since temperature inside the reactor is not high, the venting time can be shorted to 15 min. In addition, the concentration of acid/oxidizing reagents needed to complete the acid leaching (2.5 M, 3.0 M and 0.5% (m/v) for nitric acid, hydrochloric acid and hydrogen peroxide, respectively) is lower than the required concentration for a conventional microwave-assisted acid digestion (concentrated acids). The proposed method has showed a good repeatability of the overall method, and relative standard deviations between 11 and 2% were reached for 12 replicate microwave-assisted acid leaching and ICP-OES measurements. The method was finally validated by analyzing TORT-1 and GBW certified reference materials and it

38 was successfully applied to fast multi-element determinations in several raft mussel samples. Type of sample: Mussel (Mytilus galloprovincialis) soft tissue (muscle and gill) Sample amount: 0.5 g Microwave oven (model): Ethos Plus (Milestone, Sorisole, Italy) Vessel material: PTFE Heating: Step 1: 65 ºC, 2.5 min. Step 2: 600 W, 65 ºC and 0.5 min Number of samples simultaneously digested: not informed Reagents: 15 ml of oxidizing solution (2.5 mol/l, 3.0 mol/l and 0.5% (m/v) of HNO 3, HCl e H 2 O 2, respectively) Pretreatment general aspects: Mechanical blending, homogenization and freeze dry processes; samples were ground in a ball mill, mean particle size 50 µm. Detection technique: ICP OES Analytes: Al, Ba, Cd, Cr, Cu, Fe, Mn, Pb, Sn, V and Zn

39 Sample preparation for metalloprotein analysis: A case study using horse chestnuts Magalhães, C. S. and Arruda, M. A. Z., Talanta, 71 (5), , 2007 In the present work, 11 different procedures for protein and metalloprotein extraction from horse chestnuts (Aescullus hippocastanum L.) in natura were tested. After each extraction, total protein was determined and, after protein separation through sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE), those metals belonging to the protein structure were mapped by synchrotron radiation X-ray fluorescence (SRXRF). After mapping the elements (Cr, Fe and Mn) in the protein bands (ca. 33 and 23.7 kda), their concentrations were determined using atomic absorption spectrometry (ET AAS). Good results were obtained for protein extraction using a combination of grinding and sonication. However, this strategy was not suitable to preserve metal ions in the protein structure. In fact, there was 42% decrease on Mn concentration using this procedure, compared to that performed with sample agitation in water (taken as reference). On the other hand, when grinding and agitation with an extracting buffer was used, there was a 530% increase of Mn concentration, when compared to the reference procedure. These results indicate agreement between metal identification and determination in proteins as well as the great influence of the extraction procedure (i.e., the sample preparation step) for preserving metals in the protein structures. Type of sample: gel protein band (horse chesnusts) Sample amount: g Microwave oven (model): Model DTG 100 Provecto, Brazil Vessel material: Teflon Heating: Three steps: 1) 3 min at 400 W. 2) 6 min at 790 W. 3) 3 min at 0 W, the program being running twice. After finishing the sample

40 decomposition program, the Teflon vessels were placed on a hot plate (60 70 o C) for evaporation the excess of HNO 3. Number of simultaneous treated samples: not informed Reagents: 5 ml HNO ml H 2 O 2 Pretreatment general aspects: 5mL of HNO 3 and 1mL of H 2 O 2 : 30 min for safety reasons Detection technique: ETAAS Analytes: Fe, Cr and Mn

41 Simultaneous determination of inorganic mercury, methylmercury, and total mercury concentrations in cryogenic fresh-frozen and freezedried biological reference materials Point, D., Davis, W. C., Alonso, J. I. G., Monperrus, M., Christopher, S. J., Donard, O. F. X., Becker, P. R. and Wise, S. A., Analytical and Bioanalytical Chemistry, 389 (3), , 2007 Two speciated isotope dilution (SID) approaches consisting of a singlespike (SS) method and a double-spike (DS) method including a reaction/transformation model for the correction of inadvertent transformations affecting mercury species were compared in terms of accuracy, method performance, and robustness for the simultaneous determination of methylmercury (MeHg), inorganic mercury (ihg), and total mercury (HgT) concentrations in five biological Standard Reference Materials (SRMs). The SRMs consisted of oyster and mussel tissue materials displaying different mercury species concentration levels and different textural/matrix properties including freeze-dried (FD) materials (SRMs 1566b, 2976, and 2977) and cryogenically prepared and stored fresh-frozen (FF) materials (SRMs 1974a, 1974b). Each sample was spiked with (201)iHg (Oak Ridge National Laboratory, ORNL) and (MeHg)-Hg- 202 (Institute for Reference Materials and Measurements. IRMM-670) solutions and analyzed using alkaline microwave digestion, ethylation, and gas chromatography inductively coupled plasma mass spectrometry (GC/ICP-MS). The results obtained by the SS-SID method suggested that FF and FD materials are not always commutable for the simultaneous determination of ihg, MeHg, and HgT, due to potential transformation reactions resulting probably from the methodology and/or from the textural/matrix properties of the materials. These transformations can occasionally significantly affect mercury species concentration results