Journal of Chromatography B: Biomedical Sciences and Applications
Short communicationIon chromatographic method for simultaneous determination of nitrate and nitrite in human saliva
Introduction
Extensive interest has been attained in determining nitrite and nitrate in biological materials. Nitrite and nitrate are generally regarded as hazardous compounds, because they are highly toxic to humans and especially to infants, which usually results in methemoglobinemia and possibly death [1], [2]. Nitrite has the possibility to react with secondary amines and amides and form various carcinogenic N-nitroso compounds [3].
Salivary nitrite is produced due to microbial reduction of nitrate in the oral cavity. Therefore, ingested nitrite through foods and salivary nitrite can react in vivo with various amines and amides in the food in the acidic environment of human stomach or other parts of the body to form N-nitroso compounds [3]. This reason suggests the need for accurate control and monitoring of nitrite and nitrate level in human saliva, Many researchers have studied the effect of various nitrate-rich diets on salivary nitrite levels and ultimately on vivo N-nitrosation [3].
Several methods have been reported for the determination of nitrite and nitrate in foods and biological materials [4], [5], [6], [7], [8], these methods include high-performance liquid chromatography (HPLC) or flow injection with chemiluminescence detection [4], gas chromatography (GC) [5], [6], HPLC using a micellar mobile phase [7], HPLC by reversed-phase ion pair liquid chromatography [8] and spectrophotometric methods [9], [10], [11]. Where a spectrophotometric method is widely used, it is based on a diazotization of various aromatic amines with nitrite in acidic medium and on a subsequent coupling of the diazonium ions with N-(1-naphthyl)ethylenediamine [9], 8 quinoline [10], or resorcinol [11]. In general, spectrophotometric methods are subject to various interferences and lack of specificity. GC methods in general need a derivatization reaction and then partitioning to the organic layer prior to analysis, which is a complicated process. In liquid chromatography, nitrite is liable to be oxidized in the acidic medium during the process [12].
In the present communication we describe a selective and sensitive analytical method in which nitrite and nitrate are determined directly from human saliva using ion chromatography (IC) using an Ion Pac AS12A column, with suppressed conductivity detection. The method allows simultaneous determination of nitrite and nitrate in human saliva.
Section snippets
Instrumentation
A Dionex (Sunnyvale, CA, USA) a suppressed conductivity detection ASR-II, Auto suppression-II, recycle mode and LC25 enclosure system, was used. Chromatographic data were analyzed using a C-R6A chromatopac chart. The Ion Pac AS12A (200×4 mm) column was obtained from Dionex.
Materials
Human saliva samples were collected from different volunteers. Sodium nitrite and sodium nitrate were obtained from (Wako, Japan). Sodium carbonate and sodium hydrogencarbonate were also obtained from (Wako).
Ion chromatography
Nitrite and
Results and discussion
Fig. 1 shows the chromatogram of the standards nitrate and nitrite. Chromatograms of nitrite and nitrate for saliva samples obtained from different volunteers are shown in Fig. 2a and b. The chromatograms of of the spiked saliva with nitrite and nitrate are shown in Fig. 2c and d. The simultaneous determination of nitrite and nitrate in saliva by the Ion Pac AS12A column was performed with suppressed conductivity detection. The dissolved solution of solid saliva is centrifuged and was directly
Conclusion
The proposed analytical method for determining nitrate and nitrite in human saliva is simple, rapid and accurate. The anion-exchange column in conjunction with suppressed conductivity detection was adopted to provide to a selective determination of nitrate and nitrite from human saliva without interference from the matrix components present in the saliva. The saliva sample needs only centrifugation to remove the insoluble matter and no sample preparation or clean-up process is necessary. The
Acknowledgements
The authors are grateful to Japan Society for the promotion of Science (JSPS), Japan, for the award of a postdoctoral fellowship (P98448) and financial support. This work is partly supported by the Grant-in-Aids (10558085, 10650797) from The Ministry of Education, Science, Sports and Culture, Japan.
References (12)
Toxicol. Appl. Pharmacol.
(1975)J. Chromatogr.
(1993)- et al.
J. Chromatogr.
(1976) - et al.
Anal. Chim. Acta
(1982) - et al.
Talanta
(1983)
Cited by (143)
Parts per billion of nitrite in microcrystalline cellulose by ion chromatography mass spectrometry with isotope labeled internal standard
2023, Journal of Pharmaceutical and Biomedical AnalysisDetermination of nitrite in food specimens using electrochemical sensor based on polyneutral red modified reduced graphene oxide paste electrode
2023, International Journal of Electrochemical ScienceFabrication non-enzymatic electrochemical sensor based on methyl red and graphene oxide nanocomposite modified carbon paste electrode for determination of nitrite in food samples
2023, International Journal of Electrochemical Science