Flow analysis methods for the direct ultra-violet spectrophotometric measurement of nitrate and total nitrogen in freshwaters.

Second derivative ultra-violet spectrophotometric methods are described for the measurement of nitrate and total nitrogen in freshwaters using flow analysis techniques. A simple flow system consisting of a peristaltic pump and a single-reflection flow-through cell was used for the measurement of nitrate. Quantification of total nitrogen using alkaline peroxodisulfate photo-digestion was achieved by incorporating an ultra-violet photo-reactor, a hollow-fibre filter and a debubbler into the flow system. The nitrate system featured a limit of detection of 0.04 mg N L(-1), 0.4%RSD (1 mg N L(-1) as nitrate, n=10), a coefficient of determination (R(2)) of 0.9995 over the calibration range 0.0-2.0 mg N L(-1), and a data acquisition time of 1.5s per spectrum. The total nitrogen system featured a limit of detection of 0.05 mg N L(-1), 1%RSD (1 mg N L(-1) as ammonium chloride, n=10), a coefficient of determination of 0.9989 over the calibration range 0.0-2.0 mg N L(-1), and a throughput of 5 sample h(-1) measured in triplicate. Digestions of five model nitrogen compounds returned recoveries of >88%. Determinations carried out using the developed systems show a high degree of agreement with data obtained using reference methods. These methods require no colorimetric reagents and eliminate the requirement for a toxic cadmium reduction column. The overlap of chloride and nitrate spectra in seawater is not eliminated entirely by the use of second derivative spectrophotometry, and consequently the methods are restricted to the analysis of freshwaters.

[1]  E. Lewis,et al.  The practical salinity scale 1978 and its antecedents , 1980 .

[2]  Pavel Mikusˇka,et al.  Flow-injection chemiluminescence determination of ultra low concentrations of nitrite in water , 1995 .

[3]  I. McKelvie,et al.  Analysis of total dissolved nitrogen in natural waters by on-line photooxidation and flow injection , 1994 .

[4]  Olivier Thomas,et al.  Wastewater quality monitoring , 1997 .

[5]  Paul J. Worsfold,et al.  Determination of carbon, phosphorus, nitrogen and silicon species in waters , 1994 .

[6]  Jaromir Růžička,et al.  Flow injection analysis , 1981 .

[7]  F. A. Richards,et al.  Determination of nitrate in sea water by cadmium-copper reduction to nitrite , 1967, Journal of the Marine Biological Association of the United Kingdom.

[8]  P. Mitchell,et al.  Nitrate and organic N analyses with second-derivative spectroscopy , 1992 .

[9]  F. Armstrong Determination of Nitrate in Water Ultraviolet Spectrophotometry. , 1963 .

[10]  Iver W. Duedall,et al.  PREPARATION OF ARTIFICIAL SEAWATER1 , 1967 .

[11]  A. C. Redfield The biological control of chemical factors in the environment. , 1960, Science progress.

[12]  O. Thomas,et al.  Measurement of dissolved total nitrogen in wastewater by UV photooxidation with peroxodisulphate , 1999 .

[13]  Manfred Ehrhardt,et al.  Methods of seawater analysis , 1999 .

[14]  B. C. Madsen Utilization of flow injection with hydrazine reduction and photometric detection for the determination of nitrate in rain-water , 1981 .

[15]  J. Miller,et al.  Statistics and chemometrics for analytical chemistry , 2005 .

[16]  R. Compton,et al.  Detection and determination of nitrate and nitrite: a review. , 2001, Talanta.

[17]  Ali Mohammad Haji Shabani,et al.  Field measurement of nitrate in marine and estuarine waters with a flow analysis system utilizing on-line zinc reduction. , 2011, Talanta: The International Journal of Pure and Applied Analytical Chemistry.

[18]  C. R. Sawicki,et al.  Colorimetric determination of nitrate after hydrazine reduction to nitrite , 1971 .

[19]  I. McKelvie,et al.  Sensitive flow-injection technique for the determination of dissolved organic carbon in natural and waste waters , 1992 .

[20]  P. M. Williams,et al.  Photo-oxidation of Organic Matter in Sea Water by Ultra-violet Radiation, Analytical and Other Applications , 1966, Nature.

[21]  H. Mckenzie The kjeldahl determination of nitrogen: Retrospect and prospect , 1994 .

[22]  Olivier Thomas,et al.  Ultraviolet multiwavelength absorptiometry (UVMA) for the examination of natural waters and wastewaters , 1990 .

[23]  A. W. Morris,et al.  The determination of nitrate in sea water , 1963 .

[24]  D. Langmuir,et al.  Specific-ion electrode determination of nitrate in some fresh waters and sewage effluents , 1970 .

[25]  R. Kellner Analytical chemistry : the approved text to the FECS curriculumanalytical chemistry , 1998 .

[26]  Celio Pasquini,et al.  Flow-injection Determination Of Inorganic Forms Of Nitrogen By Gas Diffusion And Conductimetry , 1991 .

[27]  R. Shannon,et al.  Evaluation of a second derivative UV/visible spectroscopy technique for nitrate and total nitrogen analysis of wastewater samples. , 2001, Water research.

[28]  Leo M.L. Nollet,et al.  Handbook of Water Analysis , 2013 .

[29]  F. R. Rocha,et al.  A green analytical procedure for flow-injection determination of nitrate in natural waters. , 2005, Talanta.

[30]  C. Stalikas,et al.  Ion chromatographic method for the simultaneous determination of nitrite and nitrate by post-column indirect fluorescence detection. , 2003, Journal of chromatography. A.

[31]  Tim D Fletcher,et al.  Nitrogen composition in urban runoff--implications for stormwater management. , 2005, Water research.

[32]  A. Townshend,et al.  Spectrophotometric flow-injection determination of nitrate based on reduction with titanium(III) chloride , 1986 .

[33]  G. G. Stokes "J." , 1890, The New Yale Book of Quotations.

[34]  D. Keeney,et al.  Determination of nitrate in waters with the nitrate-selective ion electrode. , 1970, The Analyst.

[35]  F. Nydahl On the optimum conditions for the reduction of nitrate to nitrite by cadmium. , 1976, Talanta.

[36]  J. Kjeldahl,et al.  Neue Methode zur Bestimmung des Stickstoffs in organischen Körpern , 1883 .

[37]  M. S. Finch,et al.  A low power ultra violet spectrophotometer for measurement of nitrate in seawater: introduction, calibration and initial sea trials , 1998 .