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| Content Provider | World Health Organization (WHO)-Global Index Medicus |
|---|---|
| Author | Brandao, Geovani C. Matos, Geraldo D. Pereira, Raimundo N. Ferreira, Sergio L. C. |
| Description | Author Affiliation: Brandao GC ( Universidade Federal da Bahia, Instituto de Química, Campus Ondina, Salvador BA 40170-115, Brazil); Matos GD ( Universidade Federal da Bahia, Instituto de Química, Campus Ondina, Salvador BA 40170-115, Brazil); Pereira RN ( Universidade Federal da Bahia, Instituto de Química, Campus Ondina, Salvador BA 40170-115, Brazil.); Ferreira SL ( Universidade Federal da Bahia, Instituto de Química, Campus Ondina, Salvador BA 40170-115, Brazil) |
| Abstract | In this work, it was developed a method for the determination of nitrite and nitrate in groundwater by high-resolution continuum source electrothermal molecular absorption spectrometry of NO produced by thermal decomposition of nitrate in a graphite furnace. The NO line at 215.360 nm was used for all analytical measurements and the signal obtained by integrated absorbance of three pixels. A volume of 20 µL of standard solution or groundwater sample was injected into graphite furnace and 5 µL of a 1% (m/v) Ca solution was co-injected as chemical modifier. The pyrolisis and vaporization temperatures established were of 150 and 1300°C, respectively. Under these conditions, it was observed a difference of thermal stability among the two nitrogen species in the presence of hydrochloric acid co-injected. While that the nitrite signal was totally suppressed, nitrate signal remained nearly stable. This way, nitrogen can be quantified only as nitrate. The addition of hydrogen peroxide provided the oxidation of nitrite to nitrate, which allowed the total quantification of the species and nitrite obtained by difference. A volume of 5 µL of 0.3% (v/v) hydrochloric acid was co-injected for the elimination of nitrite, whereas that hydrogen peroxide in the concentration of 0.75% (v/v) was added to samples or standards for the oxidation of nitrite to nitrate. Analytical curve was established using standard solution of nitrate. The method described has limits of detection and quantification of 0.10 and 0.33 µg mL(-1) of nitrogen, respectively. The precision, estimated as relative standard deviation (RSD), was of 7.5 and 3.8% (n=10) for groundwater samples containing nitrate-N concentrations of 1.9 and 15.2 µg mL(-1), respectively. The proposed method was applied to the analysis of 10 groundwater samples and the results were compared with those obtained by ion chromatography method. In all samples analyzed, the concentration of nitrite-N was always below of the limit of quantification of both the methods. The concentrations of nitrate-N varied from 0.58 to 15.5 µg mL(-1). No significant difference it was observed between the results obtained by both methods for nitrate-N, at the 95% confidence level. |
| File Format | HTM / HTML |
| ISSN | 00032670 |
| Volume Number | 806 |
| e-ISSN | 18734324 |
| Journal | Analytica Chimica Acta |
| Language | English |
| Publisher | Elsevier |
| Publisher Date | 2014-01-02 |
| Publisher Place | Netherlands |
| Access Restriction | One Nation One Subscription (ONOS) |
| Subject Keyword | Discipline Analytical Discipline Chemistry Chemistry Techniques, Analytical Methods Environmental Monitoring Groundwater Chemistry Nitrates Analysis Nitrites Spectrophotometry, Atomic Graphite Hydrochloric Acid Hydrogen Peroxide Oxidation-reduction Temperature Journal Article Research Support, Non-u.s. Gov't |
| Content Type | Text |
| Resource Type | Article |
| Subject | Spectroscopy Environmental Chemistry Analytical Chemistry Biochemistry |
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