Felix Guilermo Reyes Reyes - Academia.edu (original) (raw)
Papers by Felix Guilermo Reyes Reyes
Analytical and Bioanalytical Chemistry, 2004
Toxicology Letters, 2006
Tetracyclines are considered an important group of broad spectrum antimicrobials employed in Braz... more Tetracyclines are considered an important group of broad spectrum antimicrobials employed in Brazil in several species of animals producing food, including bovine, swine and fish. A HPLC method for the determination of oxytetracycline (OTC), doxycycline (DC) and tetracycline (TC) residues in milk and yogurt was developed and validated. The method was used to evaluate the degradation of these antimicrobial contaminants during the thermal treatment of milk, as well as during yogurt preparation and storage. Sample extraction was carried out using 30% (v/v) trichloroacetic acid to precipitate the proteins. For the HPLC analyses a Varian C 8 analytical column (250× 4.6 mm, 5 m) with a mobile phase: sodium acetate 0.1 mol L −1 + EDTA 25 mmol L −1 + calcium chloride 35 mmol L −1 : methanol (65:35, v/v) and fluorescence detection (λ excitation: 420 nm and λ emission: 530 nm) was used. Tetracycline recovery in milk and yogurt was 92-98% (OTC); 87-83% (DC) and 89-97% (TC). The quantitation limit was 27, 46 and 33 ng mL −1 for OTC, DC and TC, respectively. Different thermal treatments were used to evaluate the heat stability of the tetracyclines in milk: cooking stove treatment, hot plate and microwave oven. Higher degradation occurred using the hot plate, 10.9% (OTC), 27.7% (DC) and 15.0% (TC). With respect to the stability of the tetracyclines during the preparation and shelf life of yogurt, it was verified that 500 ng mL −1 (OTC), 1120 ng mL −1 (DC) and 600 ng mL −1 (TC) did not inhibit yogurt production, and that after 30 days under refrigeration (4 • C), residual levels of the contaminants still remained in the samples. Nonetheless, in relation to the original contamination in the yogurt, the tetracycline levels had diminished by 52%, 61% and 67%, for OTC, DC and TC, respectively. The data indicated that when conducting a risk assessment of tetracyclines in human health, the presence of these contaminants in milk and yogurt should be considered as a potential source. In addition, in order to protect consumer health, the governmental agencies should monitor the application of good practices in the use of these antimicrobials in the treatment of cows that produce milk for human consumption, as well as conducting health surveillance actions in order to control the residue levels of these substances in commercialized milk and yogurt.
Toxicology Letters, 2006
Tetracyclines are considered an important group of broad spectrum antimicrobials employed in Braz... more Tetracyclines are considered an important group of broad spectrum antimicrobials employed in Brazil in several species of animals producing food, including bovine, swine and fish. A HPLC method for the determination of oxytetracycline (OTC), doxycycline (DC) and tetracycline (TC) residues in milk and yogurt was developed and validated. The method was used to evaluate the degradation of these antimicrobial contaminants during the thermal treatment of milk, as well as during yogurt preparation and storage. Sample extraction was carried out using 30% (v/v) trichloroacetic acid to precipitate the proteins. For the HPLC analyses a Varian C 8 analytical column (250× 4.6 mm, 5 m) with a mobile phase: sodium acetate 0.1 mol L −1 + EDTA 25 mmol L −1 + calcium chloride 35 mmol L −1 : methanol (65:35, v/v) and fluorescence detection (λ excitation: 420 nm and λ emission: 530 nm) was used. Tetracycline recovery in milk and yogurt was 92-98% (OTC); 87-83% (DC) and 89-97% (TC). The quantitation limit was 27, 46 and 33 ng mL −1 for OTC, DC and TC, respectively. Different thermal treatments were used to evaluate the heat stability of the tetracyclines in milk: cooking stove treatment, hot plate and microwave oven. Higher degradation occurred using the hot plate, 10.9% (OTC), 27.7% (DC) and 15.0% (TC). With respect to the stability of the tetracyclines during the preparation and shelf life of yogurt, it was verified that 500 ng mL −1 (OTC), 1120 ng mL −1 (DC) and 600 ng mL −1 (TC) did not inhibit yogurt production, and that after 30 days under refrigeration (4 • C), residual levels of the contaminants still remained in the samples. Nonetheless, in relation to the original contamination in the yogurt, the tetracycline levels had diminished by 52%, 61% and 67%, for OTC, DC and TC, respectively. The data indicated that when conducting a risk assessment of tetracyclines in human health, the presence of these contaminants in milk and yogurt should be considered as a potential source. In addition, in order to protect consumer health, the governmental agencies should monitor the application of good practices in the use of these antimicrobials in the treatment of cows that produce milk for human consumption, as well as conducting health surveillance actions in order to control the residue levels of these substances in commercialized milk and yogurt.
Talanta, 2000
A polarographic method for the determination of nitrate in vegetables is presented. The method is... more A polarographic method for the determination of nitrate in vegetables is presented. The method is based on the reduction of nitrate to nitric oxide which reacts in solution with colbalt (II) and thiocyanate ions forming an electroactive complex that is reduced at the dropping mercury electrode at − 0.5 V (vs. SCE). The nitric oxide is generated outside the polarographic cell by addition of ferrous ammonium sulfate and ammonium molybdate in hydrochloric acid to the previously triturated vegetable matrices. The calibration graph was linear in the range of 2-12×10 − 6 mol nitrate. The recovery of nitrate in vegetable matrices (broccoli, kale, lettuce, radish, red beet, spinach, turnip and watercress) varied from 85.4 to 107.4 % and the nitrate content, expressed as sodium nitrate, varied from 751 to 10 806 mg kg − 1 of fresh vegetable. The relative standard deviation for the proposed method is lower than 7% and considering a sample of 5.0 g, the determination limit was 39 mg of nitrate per kg fresh vegetable weight. The precision and accuracy of the polarographic method were comparable to those of the reference spectrophotometric method (official AOAC reference method for the determination of nitrate in foodstuffs).
Química Nova, 2008
Recebido em 2/4/07; aceito em 20/9/07; publicado na web em 9/4/08 VALIDATION OF CHROMATOGRAPHIC M... more Recebido em 2/4/07; aceito em 20/9/07; publicado na web em 9/4/08 VALIDATION OF CHROMATOGRAPHIC METHODS FOR THE DETERMINATION OF RESIDUES OF VETERINARY DRUGS IN FOODS. Different agencies that supply validation guidelines worldwide establish almost the same parameters to be evaluated in the validation process of bioanalytical methods. However, they recommend different procedures, as well as establish different acceptance criteria. The present review delineates and discusses the stages involved in the validation procedures of bioanalytical methods designed for determining veterinary residues in food, explaining the main differences in the guidelines established for this purpose by the main regulatory agencies in the world.
International Journal of Environmental Analytical Chemistry, 1994
Neste trabalho foi desenvolvido um método para a determinação de hexaclorobenzeno, lindano, hepta... more Neste trabalho foi desenvolvido um método para a determinação de hexaclorobenzeno, lindano, heptaclor, heptaclor epóxido, aldrin, dieldrin, endrin, DDT e DDE em folhas de Mikania laevigata, Maytenus ilicifolia e Cordia verbenacea, empregando a Cromatografia Gasosa acoplada a Espectrometria de Massas (GC-MS). A extração dos pesticidas foi realizada por extração sólidolíquido (SLE), seguida de limpeza por extração em fase sólida (Florisil e silica-gel). A quantificação foi realizada usando o GC-MS no modo SIM. A recuperação média variou de 70 a 124%. A precisão inter-ensaio de uma amostra fortificada com 200 ng g -1 de cada pesticida variou de 1,0 a 7,3%. Os limites de quantificação variaram de 3,0 a 30 ng g -1 e estão abaixo dos limites máximos de resíduos (MLR) estabelecidos para os pesticidas sob estudo. O método foi empregado para analisar amostras de Mikania laevigata, Maytenus ilicifolia e Cordia verbenacea de um campo experimental de Paulínia, SP, Brasil. As amostras apresentaram contaminação com dieldrin acima do MRL estabelecido pela Farmacopéia Européia (50 ng g -1 ).
A method for the determination of volatile nitrosamines in sausages was developed using headspace... more A method for the determination of volatile nitrosamines in sausages was developed using headspace sampling by solid-phase microextraction and gas chromatography with thermal energy analyzer detection (HS-SPME-GC-TEA). Two fused silica fibers, one coated with polydimethylsiloxane-divinylbenzene (PDMS-DVB) and another with poliacrylate (PA) were evaluated. A factorial fractional design was employed in order to evaluate the influence of the equilibrium time, ionic
Food Chemistry, 2009
A high-performance liquid chromatographic method for the simultaneous determination of tetracycli... more A high-performance liquid chromatographic method for the simultaneous determination of tetracycline, oxytetracycline, chlortetracycline, sulfamethazine, sulfaquinoxaline, sulfamethoxazole and chloramphenicol in milk has been developed. The determination of these antimicrobials was carried out using HPLC-DAD with a C 18 hybrid column and gradient elution with a mobile phase composed of an aqueous phase of 0.075 mol L À1 sodium acetate, 0.035 mol L À1 calcium chloride and 0.025 mol L À1 sodium EDTA, pH 7 and an organic phase of methanol:acetonitrile, 75:25 v/v. Sample preparation involved protein precipitation followed by solid-phase extraction using a polymeric cartridge. The method was validated and applied for the analysis of pasteurised milk samples commercialised in Brazil. The limits of quantitation for all antimicrobials, with the exception of choramphenicol, were below the maximum residue limit, which indicates that the method is appropriate for the determination of these antimicrobials in milk.
Food Additives & Contaminants: Part A, 2009
A method for the simultaneous determination of flumequine, oxolinic acid, sarafloxacin, danofloxa... more A method for the simultaneous determination of flumequine, oxolinic acid, sarafloxacin, danofloxacin, enrofloxacin, and ciprofloxacin in tilapia (Orechromis niloticus) fillet, using high-performance liquid chromatography with fluorescence detection (HPLC-FLD) is presented. The quinolones were extracted from the food matrix with a solution of 10% trichloroacetic acid and methanol (80:20 v/v). Clean-up of the extract was performed using polymeric solid-phase extraction cartridges. Identification of the quinolones was confirmed by liquid chromatography-tandem mass spectrometry. The HPLC-FLD method was validated in-house and the following analytical parameters were obtained: linearity higher than 0.99 for all the quinolones; intra- and interassay precisions were lower than 3.5% and 10.9%, respectively; and recoveries ranged from 73% to 110%. The limit of quantification was below the maximum residue limit established by the Joint Expert Committee on Food Additives (JECFA), which indicates that the method is appropriate for the determination of quinolones in fish fillet.
Analytical and Bioanalytical Chemistry, 2009
A method for simultaneous determination of flumequine (FLM), oxolinic acid (OXO), sarafloxacin (S... more A method for simultaneous determination of flumequine (FLM), oxolinic acid (OXO), sarafloxacin (SAR), danofloxacin (DAN), enrofloxacin (ENR), and ciprofloxacin (CIP) in tilapia (Orechromis niloticus) fillets, using liquid chromatography-tandem mass spectrometry (LC-ESI-MS-MS QToF) is presented. The quinolones were extracted from the food matrix with a solution of 10% trichloroacetic acid-methanol (80:20 v/v) with ultrasonic assistance. Clean-up of the extract solution was performed by using polymeric solid-phase extraction cartridges. The LC separation was carried out on an octadecyl hybrid silica column (C 18 , 150 mm × 3 mm, 5 μm). The column temperature was set at 30°C, and gradient elution (0.2 mL min −1 ) was performed using water and acetonitrile, both containing 0.1% of acetic acid, as mobile phase components. The analytes were ionized using electrospray in the positive polarity mode. The following analytical results were obtained: linearity was about 0.99 for all the quinolones; intra and inter-assay precision (RSD%) were lower than 12.7 and 20%, respectively; and recoveries were from 89 to 112%. The quantitation limits were below the maximum residue limits established for the analytes. The method is suitable for the determination of quinolone residues in fish fillets and the QToF technique made it possible to obtain m/z ratios with less than 10 ppm of error for each analyte.
Food Additives and Contaminants Part A-chemistry Analysis Control Exposure & Risk Assessment, 2005
The nitrate content of leafy vegetables (watercress, lettuce and arugula) produced by different a... more The nitrate content of leafy vegetables (watercress, lettuce and arugula) produced by different agricultural systems (conventional, organic and hydroponic) was determined. The daily nitrate intake from the consumption of these crop species by the average Brazilian consumer was also estimated. Sampling was carried out between June 2001 to February 2003 in Campinas, São Paulo State, Brazil. Nitrate was extracted from
Analytical and Bioanalytical Chemistry, 2004
Toxicology Letters, 2006
Tetracyclines are considered an important group of broad spectrum antimicrobials employed in Braz... more Tetracyclines are considered an important group of broad spectrum antimicrobials employed in Brazil in several species of animals producing food, including bovine, swine and fish. A HPLC method for the determination of oxytetracycline (OTC), doxycycline (DC) and tetracycline (TC) residues in milk and yogurt was developed and validated. The method was used to evaluate the degradation of these antimicrobial contaminants during the thermal treatment of milk, as well as during yogurt preparation and storage. Sample extraction was carried out using 30% (v/v) trichloroacetic acid to precipitate the proteins. For the HPLC analyses a Varian C 8 analytical column (250× 4.6 mm, 5 m) with a mobile phase: sodium acetate 0.1 mol L −1 + EDTA 25 mmol L −1 + calcium chloride 35 mmol L −1 : methanol (65:35, v/v) and fluorescence detection (λ excitation: 420 nm and λ emission: 530 nm) was used. Tetracycline recovery in milk and yogurt was 92-98% (OTC); 87-83% (DC) and 89-97% (TC). The quantitation limit was 27, 46 and 33 ng mL −1 for OTC, DC and TC, respectively. Different thermal treatments were used to evaluate the heat stability of the tetracyclines in milk: cooking stove treatment, hot plate and microwave oven. Higher degradation occurred using the hot plate, 10.9% (OTC), 27.7% (DC) and 15.0% (TC). With respect to the stability of the tetracyclines during the preparation and shelf life of yogurt, it was verified that 500 ng mL −1 (OTC), 1120 ng mL −1 (DC) and 600 ng mL −1 (TC) did not inhibit yogurt production, and that after 30 days under refrigeration (4 • C), residual levels of the contaminants still remained in the samples. Nonetheless, in relation to the original contamination in the yogurt, the tetracycline levels had diminished by 52%, 61% and 67%, for OTC, DC and TC, respectively. The data indicated that when conducting a risk assessment of tetracyclines in human health, the presence of these contaminants in milk and yogurt should be considered as a potential source. In addition, in order to protect consumer health, the governmental agencies should monitor the application of good practices in the use of these antimicrobials in the treatment of cows that produce milk for human consumption, as well as conducting health surveillance actions in order to control the residue levels of these substances in commercialized milk and yogurt.
Toxicology Letters, 2006
Tetracyclines are considered an important group of broad spectrum antimicrobials employed in Braz... more Tetracyclines are considered an important group of broad spectrum antimicrobials employed in Brazil in several species of animals producing food, including bovine, swine and fish. A HPLC method for the determination of oxytetracycline (OTC), doxycycline (DC) and tetracycline (TC) residues in milk and yogurt was developed and validated. The method was used to evaluate the degradation of these antimicrobial contaminants during the thermal treatment of milk, as well as during yogurt preparation and storage. Sample extraction was carried out using 30% (v/v) trichloroacetic acid to precipitate the proteins. For the HPLC analyses a Varian C 8 analytical column (250× 4.6 mm, 5 m) with a mobile phase: sodium acetate 0.1 mol L −1 + EDTA 25 mmol L −1 + calcium chloride 35 mmol L −1 : methanol (65:35, v/v) and fluorescence detection (λ excitation: 420 nm and λ emission: 530 nm) was used. Tetracycline recovery in milk and yogurt was 92-98% (OTC); 87-83% (DC) and 89-97% (TC). The quantitation limit was 27, 46 and 33 ng mL −1 for OTC, DC and TC, respectively. Different thermal treatments were used to evaluate the heat stability of the tetracyclines in milk: cooking stove treatment, hot plate and microwave oven. Higher degradation occurred using the hot plate, 10.9% (OTC), 27.7% (DC) and 15.0% (TC). With respect to the stability of the tetracyclines during the preparation and shelf life of yogurt, it was verified that 500 ng mL −1 (OTC), 1120 ng mL −1 (DC) and 600 ng mL −1 (TC) did not inhibit yogurt production, and that after 30 days under refrigeration (4 • C), residual levels of the contaminants still remained in the samples. Nonetheless, in relation to the original contamination in the yogurt, the tetracycline levels had diminished by 52%, 61% and 67%, for OTC, DC and TC, respectively. The data indicated that when conducting a risk assessment of tetracyclines in human health, the presence of these contaminants in milk and yogurt should be considered as a potential source. In addition, in order to protect consumer health, the governmental agencies should monitor the application of good practices in the use of these antimicrobials in the treatment of cows that produce milk for human consumption, as well as conducting health surveillance actions in order to control the residue levels of these substances in commercialized milk and yogurt.
Talanta, 2000
A polarographic method for the determination of nitrate in vegetables is presented. The method is... more A polarographic method for the determination of nitrate in vegetables is presented. The method is based on the reduction of nitrate to nitric oxide which reacts in solution with colbalt (II) and thiocyanate ions forming an electroactive complex that is reduced at the dropping mercury electrode at − 0.5 V (vs. SCE). The nitric oxide is generated outside the polarographic cell by addition of ferrous ammonium sulfate and ammonium molybdate in hydrochloric acid to the previously triturated vegetable matrices. The calibration graph was linear in the range of 2-12×10 − 6 mol nitrate. The recovery of nitrate in vegetable matrices (broccoli, kale, lettuce, radish, red beet, spinach, turnip and watercress) varied from 85.4 to 107.4 % and the nitrate content, expressed as sodium nitrate, varied from 751 to 10 806 mg kg − 1 of fresh vegetable. The relative standard deviation for the proposed method is lower than 7% and considering a sample of 5.0 g, the determination limit was 39 mg of nitrate per kg fresh vegetable weight. The precision and accuracy of the polarographic method were comparable to those of the reference spectrophotometric method (official AOAC reference method for the determination of nitrate in foodstuffs).
Química Nova, 2008
Recebido em 2/4/07; aceito em 20/9/07; publicado na web em 9/4/08 VALIDATION OF CHROMATOGRAPHIC M... more Recebido em 2/4/07; aceito em 20/9/07; publicado na web em 9/4/08 VALIDATION OF CHROMATOGRAPHIC METHODS FOR THE DETERMINATION OF RESIDUES OF VETERINARY DRUGS IN FOODS. Different agencies that supply validation guidelines worldwide establish almost the same parameters to be evaluated in the validation process of bioanalytical methods. However, they recommend different procedures, as well as establish different acceptance criteria. The present review delineates and discusses the stages involved in the validation procedures of bioanalytical methods designed for determining veterinary residues in food, explaining the main differences in the guidelines established for this purpose by the main regulatory agencies in the world.
International Journal of Environmental Analytical Chemistry, 1994
Neste trabalho foi desenvolvido um método para a determinação de hexaclorobenzeno, lindano, hepta... more Neste trabalho foi desenvolvido um método para a determinação de hexaclorobenzeno, lindano, heptaclor, heptaclor epóxido, aldrin, dieldrin, endrin, DDT e DDE em folhas de Mikania laevigata, Maytenus ilicifolia e Cordia verbenacea, empregando a Cromatografia Gasosa acoplada a Espectrometria de Massas (GC-MS). A extração dos pesticidas foi realizada por extração sólidolíquido (SLE), seguida de limpeza por extração em fase sólida (Florisil e silica-gel). A quantificação foi realizada usando o GC-MS no modo SIM. A recuperação média variou de 70 a 124%. A precisão inter-ensaio de uma amostra fortificada com 200 ng g -1 de cada pesticida variou de 1,0 a 7,3%. Os limites de quantificação variaram de 3,0 a 30 ng g -1 e estão abaixo dos limites máximos de resíduos (MLR) estabelecidos para os pesticidas sob estudo. O método foi empregado para analisar amostras de Mikania laevigata, Maytenus ilicifolia e Cordia verbenacea de um campo experimental de Paulínia, SP, Brasil. As amostras apresentaram contaminação com dieldrin acima do MRL estabelecido pela Farmacopéia Européia (50 ng g -1 ).
A method for the determination of volatile nitrosamines in sausages was developed using headspace... more A method for the determination of volatile nitrosamines in sausages was developed using headspace sampling by solid-phase microextraction and gas chromatography with thermal energy analyzer detection (HS-SPME-GC-TEA). Two fused silica fibers, one coated with polydimethylsiloxane-divinylbenzene (PDMS-DVB) and another with poliacrylate (PA) were evaluated. A factorial fractional design was employed in order to evaluate the influence of the equilibrium time, ionic
Food Chemistry, 2009
A high-performance liquid chromatographic method for the simultaneous determination of tetracycli... more A high-performance liquid chromatographic method for the simultaneous determination of tetracycline, oxytetracycline, chlortetracycline, sulfamethazine, sulfaquinoxaline, sulfamethoxazole and chloramphenicol in milk has been developed. The determination of these antimicrobials was carried out using HPLC-DAD with a C 18 hybrid column and gradient elution with a mobile phase composed of an aqueous phase of 0.075 mol L À1 sodium acetate, 0.035 mol L À1 calcium chloride and 0.025 mol L À1 sodium EDTA, pH 7 and an organic phase of methanol:acetonitrile, 75:25 v/v. Sample preparation involved protein precipitation followed by solid-phase extraction using a polymeric cartridge. The method was validated and applied for the analysis of pasteurised milk samples commercialised in Brazil. The limits of quantitation for all antimicrobials, with the exception of choramphenicol, were below the maximum residue limit, which indicates that the method is appropriate for the determination of these antimicrobials in milk.
Food Additives & Contaminants: Part A, 2009
A method for the simultaneous determination of flumequine, oxolinic acid, sarafloxacin, danofloxa... more A method for the simultaneous determination of flumequine, oxolinic acid, sarafloxacin, danofloxacin, enrofloxacin, and ciprofloxacin in tilapia (Orechromis niloticus) fillet, using high-performance liquid chromatography with fluorescence detection (HPLC-FLD) is presented. The quinolones were extracted from the food matrix with a solution of 10% trichloroacetic acid and methanol (80:20 v/v). Clean-up of the extract was performed using polymeric solid-phase extraction cartridges. Identification of the quinolones was confirmed by liquid chromatography-tandem mass spectrometry. The HPLC-FLD method was validated in-house and the following analytical parameters were obtained: linearity higher than 0.99 for all the quinolones; intra- and interassay precisions were lower than 3.5% and 10.9%, respectively; and recoveries ranged from 73% to 110%. The limit of quantification was below the maximum residue limit established by the Joint Expert Committee on Food Additives (JECFA), which indicates that the method is appropriate for the determination of quinolones in fish fillet.
Analytical and Bioanalytical Chemistry, 2009
A method for simultaneous determination of flumequine (FLM), oxolinic acid (OXO), sarafloxacin (S... more A method for simultaneous determination of flumequine (FLM), oxolinic acid (OXO), sarafloxacin (SAR), danofloxacin (DAN), enrofloxacin (ENR), and ciprofloxacin (CIP) in tilapia (Orechromis niloticus) fillets, using liquid chromatography-tandem mass spectrometry (LC-ESI-MS-MS QToF) is presented. The quinolones were extracted from the food matrix with a solution of 10% trichloroacetic acid-methanol (80:20 v/v) with ultrasonic assistance. Clean-up of the extract solution was performed by using polymeric solid-phase extraction cartridges. The LC separation was carried out on an octadecyl hybrid silica column (C 18 , 150 mm × 3 mm, 5 μm). The column temperature was set at 30°C, and gradient elution (0.2 mL min −1 ) was performed using water and acetonitrile, both containing 0.1% of acetic acid, as mobile phase components. The analytes were ionized using electrospray in the positive polarity mode. The following analytical results were obtained: linearity was about 0.99 for all the quinolones; intra and inter-assay precision (RSD%) were lower than 12.7 and 20%, respectively; and recoveries were from 89 to 112%. The quantitation limits were below the maximum residue limits established for the analytes. The method is suitable for the determination of quinolone residues in fish fillets and the QToF technique made it possible to obtain m/z ratios with less than 10 ppm of error for each analyte.
Food Additives and Contaminants Part A-chemistry Analysis Control Exposure & Risk Assessment, 2005
The nitrate content of leafy vegetables (watercress, lettuce and arugula) produced by different a... more The nitrate content of leafy vegetables (watercress, lettuce and arugula) produced by different agricultural systems (conventional, organic and hydroponic) was determined. The daily nitrate intake from the consumption of these crop species by the average Brazilian consumer was also estimated. Sampling was carried out between June 2001 to February 2003 in Campinas, São Paulo State, Brazil. Nitrate was extracted from