University of North Florida
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Stuart Chalk, Ph.D.
Department of Chemistry
University of North Florida
Phone: 1-904-620-1938
Fax: 1-904-620-3535
Email: schalk@unf.edu
Website: @unf

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Commercial product

Classification: Commercial product -> fertilizer

Citations 25

"A Robust Multi-syringe System For Process Flow Analysis. Part 3. Time Based Injection Applied To The Spectrophotometric Determination Of Nickel(II) And Iron Speciation"
Analyst 2001 Volume 126, Issue 6 Pages 903-910
Fernando Albertús, Andreu Cladera, Eduardo Becerra and Victor Cerdà

Abstract: A new software-controlled time-based system for sample or reagent introduction in process flow injection analysis was developed. By using a multi-syringe burette coupled with one multi-port selection valve, the time-based injection of precise known volumes was accomplished. Characteristics and performance of the injection system were studied by injecting an indicator in a buffered carrier. Two multi-syringe time-based injection (MS-TBI) systems were implemented: first, the injection of a sample in a multiple-channel manifold where the sample would sequentially merge and react with different reagents, and second, the sequential injection of several solutions (sample and reagents) into a particular flowing stream. The first system was applied to the spectrophotometric determination of nickel(ii) in diluted samples from the acidic nickel ore leaching process, by using ammonium citrate as carrier, a saturated solution of iodine as oxidizing agent and alkaline dimethylglyoxime as chromogenic reagent. The sampling frequency attained was 57 h-1. Determinations on process samples compared well at the 95% confidence level with the reference values obtained by ICP-OES. The second time-based injection system was applied to the speciation of iron. Total iron and iron(ii) concentrations were separately and sequentially determined using 1,10-phenanthroline in acetic buffer medium as reagent. The developed manifold allowed the optional use of two different carrier solutions, containing or not containing ascorbic acid, for performing the separate determinations. Also, in the sequential procedure, plugs of reducing carrier were alternatively intercalated before the sample injections used for total iron determinations. Sampling frequencies of 68 injections per hour were routinely used. Accuracy was assessed by analyzing synthetic known mixtures of Fe(iii) and Fe(ii) standard solutions. Recoveries of 98-100.5% with a maximum relative standard deviation of 3.6% were found. Results obtained for various samples of fertilizers agreed well with those attained by the standard batch procedure.
Nickel(II) Spectrophotometry Multisyringe Timed injection Method comparison Computer

"Flow Injection Determination Of Ammonia In Kjeldahl Digests By Gas Diffusion And Conductometry"
Anal. Chim. Acta 1987 Volume 193, Issue 1 Pages 19-27
Celio Pasquini and Lourival Cardoso de Faria

Abstract: The digest (100 µL) was injected into a stream of water (1.6 mL min-1) and mixed with a stream of 2 M or 3 M NaOH containing 1% of EDTA (1.6 mL min-1) at ambient temperature The resulting stream was passed (3.2 mL min-1) to a diffusion cell and the NH3 was allowed to diffuse through a PTFE membrane into a second water stream, which was passed into a flow cell for conductometric determination of NH3. The manifold was constructed from polyethylene tubing (0.8 mm i.d.). There was no interference from 1.25 M H2SO4, 7 to 30 g L-1 of K2SO4, 6 mM Ca(II), Fe(III), Al(III), Mg, Zn(II), Cu(II) or Se(IV) or 3 mM Hg(II) in the determination of 2 mM or 3 mM NH3. The method was applied to samples of vegetables, animal feeds and fertilizers, and results agreed with those by a distillation - titration method. In the determination of 1 to 4% of N the coefficient of variation (n = 5) was 1%. The sampling rate was ~100 h-1.
Ammonia Conductometry Gas diffusion Interferences Method comparison Teflon membrane Kjeldahl

"Flow Injection Spectrophotometric Determination Of Phosphate Using Crystal Violet"
Anal. Chim. Acta 1991 Volume 254, Issue 1-2 Pages 197-200
D. Thorburn Burns, D. Chimpalee, N. Chimpalee and S. Ittipornkul

Abstract: Aqueous fertilizer solution, and waste water after boiling with HNO3, were filtered and the pH was adjusted to between 5 and 8. The solution were injected into a carrier stream of 0.5% poly(vinyl alcohol) at 1.5 mL min-1 and were mixed with reagent streams of 0.1 M NaMoO4, 0.5 mM crystal violet [C. I. Basic Violet 3] and 12.5% HNO3, all at 1.5 mL min-1. The absorbances were measured at 560 nm. The calibration graph was rectilinear up to 5.0 µg mL-1 of phosphate with a limit of detection of 0.02 µg mL-1. The coefficient of variation for 1.0 µg mL-1 (n = 10) was 0.69%. The results were in good agreement with those obtained by a standard method.
Phosphate Spectrophotometry pH Standard method Method comparison

"Online Pervaporation Separation Process For The Potentiometric Determination Of Fluoride In 'dirty' Samples"
Anal. Chim. Acta 1995 Volume 308, Issue 1-3 Pages 246-252
I. Papaefstathiou, M. T. Tena and M. D. Luque de Castro*

Abstract: The FIA method was based on the reaction of fluoride with hexamethyldisilazane (HMDSA) in acidic medium to form trimethylfluorisilane (TMFS). TMFS was evaporated, diffused through a hydrophobic membrane and adsorbed into a NaOH acceptor stream. Fluoride was detected using a fluoride ISE. Streams of the sample solution and 1.5% HMDSA in 2 M H2SO4 were merged to give a combined flow of 0.5 ml/min and passed through a reactor coil (300 cm length) at 90°C. A portion of the solution was injected into a 1 M H2SO4 carrier stream (1.3 ml/min) and transferred to the pervaporation cell which was maintained at 80°C. The volatile TMFS was collected in a 0.05 M NaOH acceptor stream (1.3 ml/min). The acceptor stream was merged with a stream (1.3 ml/min) containing 0.2 M acetic acid and 1 M KCl before passing to the ISE detector. The system was operated in the continuous- and stopped-flow modes. The linear dynamic ranges were 40-100 ng/l (RSD = 2.6%) in the continuous-flow mode and 5-20 mg/l (RSD = 3.58%) in the stopped-flow mode. The sampling frequencies were 8 samples/h for the continuous-flow mode and 6 samples/h for the stopped-flow mode. The method was used to determine fluoride in water, fertilizers and ceramic industry waste water. The recovery of 10 and 50 mg/l fluoride from tap and well water was >89% and the RSD (n = 3) was 3.45%.
Fluoride Potentiometry Electrode Pervaporation Stopped-flow Hydrophobic membrane

"Determination Of Cadmium In Fertilizers By Flow Injection Spectrophotometry"
Anal. Chim. Acta 1995 Volume 308, Issue 1-3 Pages 439-445
JoséAnchieta Gomes Neto, H. Bergamin, Elias Ayres G. Zagatto* and Francisco J. Krug

Abstract: The flow injection procedure for the determination of Cd in fertilizers was based on the formation of the blue ternary complex between Cd, iodide and Malachite Green (MG). The fertilizer solution was injected into a 0.05 M HNO3 carrier stream (3.2 ml/min) using a 150 cm sampling loop. The stream was successively merged with reagents R1, R2 and a previously mixed stream of reagents R3 and R4. R1 was 0.01 M picolinic acid in 0.6 M sodium acetate/0.1 M acetic acid buffer at 0.4 ml/min. R2 was 200 µg/l Cd in 0.05 M HNO3 at 0.8 ml/min. R3 was 2 M KI in 5 mg/ml ascorbic acid solution at 0.4 ml/min and R4 was 0.5 M MG at 0.4 ml/min. The formed ternary complex was propelled to the detector where the absorbance was measured at 690 nm. The calibration graph for Cd was linear for up to 200 µg/l and the detection limit was 2 µg/l. The RSD (n = 10) for the determination of 93 and 35.3 µg/l of Cd were 1.3 and 4%, respectively. Interfering ions (Hg2+, Ag+, Cu2+ and Pb2+) were removed by inserting a Chelex-100 ion exchange column (5 cm x 3 mm i.d.; 50-100 mesh) into the sample stream. The sampling frequency was 60 samples/h. The results were confirmed by tungsten coil-AAS.
Cadmium Spectrophotometry Chelex Complexation Interferences Method comparison

"Sequential Analyte Removal In Flow-analysis Determination Of Nitrogen, Phosphorus And Potassium In Fertilizers"
Anal. Chim. Acta 1995 Volume 317, Issue 1-3 Pages 239-245
Patricia Benedini Martellia, JoséAnchieta Gomes Netoa, Elias Ayres G. Zagattoa,*, Sandra M. Boscolo Brienzab, M. Conceição B. S. M. Montenegrob and JoséLuis F. Costa Limab

Abstract: A new approach for multiparametric determinations in now analysis based on successive sequestering of analytes is proposed and exemplified in the determination of water soluble nitrogen, phosphorus and potassium in fertilizers. The analytes are partially and reproducibly removed from the sample zone in the main stream towards specific analytical channels without significant alterations in the flowing sample plug. By using gas diffusion, dialysis and asymmetric stream splitting, ammonium, potassium and orthophosphate ions are stripped out and determined by flow potentiometry, flame photometry and spectrophotometry, respectively. The system permits up to 75 samples to be examined per hour, requires 90 mg tris(hydroxymethyl)aminomethane plus 75 mg ammonium heptamolybdate tetrahydrate plus 75 mg ascorbic acid per sample, and yields reproducible results (RSD usually < 3%) in agreement with usual manual procedures. The feasibility of an analogous modular system with a random selection of procedures is discussed. (17 References)
Nitrogen Phosphorus Potassium Spectrophotometry Spectrophotometry Potentiometry Gas diffusion Sample splitting Dialysis

"Oxidative Detection Of Nitrite At An Electrocatalytic Dichloride-modified Electrochemical Sensor Applied For The Flow Injection Determination Of Nitrate Using A Copper-cadmium Reductor Column"
Anal. Chim. Acta 1996 Volume 319, Issue 1-2 Pages 111-120
Andrew P. Doherty*, Margaret A. Stanley, Donal Leech and Johannes G. Vos

Abstract: A vitreous C electrode (3 mm diameter) modified with the redox polymer [Ru(bipy)2(PVP)10Cl]Cl ~bipy = 2,2'-bipyridyl and PVP = poly-(4-vinylpyridine)~ was utilized in a FIA system for the determination of nitrate (I) following reduction to nitrite at a copperized cadmium reductor column. The single channel flow injection manifold consisted of a 50 µL sample injection loop, the reductor column (12 cm x 0.2 cm i.d.) packed with copperized cadmium chips and a thin-layer detection cell equipped with the working electrode at 0.95 V vs. SCE, a Ag/AgCl reference electrode and with the stainless steel body of the cell acting as the counter electrode. The composition of the carrier stream (0.5 mL/min) was not given. The calibration graph was linear from 10 µM-10 mM I and the detection limit was 5 µM. The RSD was 2% for 0.5 mM I. The method was applied to the determination of nitrate in commercial fertilisers and the results were confirmed by potentiometry.
Nitrate Amperometry Electrode Electrode Potentiometry Sensor Method comparison Reduction column

"Automatic Multicommutation Flow System For Wide Range Spectrophotometric Calcium Determination"
Anal. Chim. Acta 1998 Volume 366, Issue 1-3 Pages 45-53
F&aacute;bio R. P. Rocha, Patr&iacute;cia B. Martelli, Rejane M. Frizzarin and Boaventura F. Reis*

Abstract: An automatic flow system based on multicommutation concept is proposed to widen the linear concentration range for spectrophotometric calcium determination The flow network was build up with three way solenoid valves to permit implementation of different sample processing conditions to achieve limited, medium and large dispersion degree without modification of the manifold configuration. Dilutions were carried out by changing both sampled volume and the analysis path length or applying zone sampling approach. The software was developed to control all steps of sample processing and to allow changing the manifold configuration to obtain suitable sample dilution This condition was attained with up to 3 trials. A linear response from 0.250 to 1000 mg L-1, and a detection limit of 7 µg L-1 (99.7% confidence level) were achieved. The relative standard deviation was 0.83% (n = 10) or better. The sampling rate was ~60 h-1 and 0.27 µg of the chromogenic reagent (3,3'-bis[N,N-bis(carboxymethyl)aminomethyl]-o-cresolphthalein) was consumed per determination The procedure was applied to calcium determination in waters, plant materials, milk, antacid tablets, fertilizers and calcareous rocks. The results were in agreement with certified values or with those obtained with flame atomic absorption spectrophotometry at a 95% confidence level.
Calcium Spectrophotometry Automation Commutation Method comparison Reference material Valve Dilution

"Flow Injection Biamperometric Determination Of Nitrate (by Photoreduction) And Nitrite With The NO2-/I- Reaction"
Anal. Chim. Acta 1998 Volume 366, Issue 1-3 Pages 241-249
I. Gil Torr&oacute;a, J. V. Garc&iacute;a Mateob and J. Mart&iacute;nez Calatayuda,*

Abstract: An unsegmented continuous-flow method for the determination of nitrite and nitrate is proposed. Nitrate is photoreduced by UV irradn. with a low-pressure 8 w Hg lamp. The nitrite in the sample and that resulting from the photoredn. of nitrate were used to oxidize iodide ion. Tri-iodide thus formed is detected biamperometrically in excess iodide by using a flow-cell furnished with two Pt electrodes polarized at 100 mV. The limits of detection, throughput and reproducibility (n = 26) thus achieved for nitrite and nitrate are 25 and 50 µg L-1, 27 and 25 h-1, and 1.2 and 1.6%, respectively. The proposed method was used to determine nitrate and nitrite in natural waters, waste waters, soils, meat products and fertilizers. (29 References)
Nitrate Nitrite Biamperometry Electrode Catalysis Reduction column Indirect Photochemistry UV reactor

"Continuous-flow Chemiluminometric Determination Of Ammonium Ion In Fertilizers"
Talanta 1993 Volume 40, Issue 8 Pages 1245-1254
Stergios A. Halvatzis and Meropi M. Timotheou-Potamia*

Abstract: The continuous-flow system (shown diagramatically) incorporated flow lines for the ammonium-containing sample solution [which also contained 1 mM dichlorofluorescein (I) and 0.1 M NaOH] and 0.15 M N-bromosuccinimide in 0.1 M NaOH (respective flow rates 3.9 and 2.9 ml/min) and a coiled glass flow cell (3.5 turns of 2 mm glass tubing) situated in front of a photomultiplier tube. The calibration graph was linear from 0.054-5.4 µg/ml of ammonium with RSD of 1.6 and 0.4% for 0.54 and 3.6 µg/mL, respectively; the detection limit was 0.032 µg/ml. Surfactants suppressed the chemiluminescence. Sulfide, nitrite, arsenite and ferricyanide interfered, but nitrate and phosphate did not. Interferences from cations (in the presence of citrate to prevent precipitation) are listed. Urea caused slight positive interference at levels exceeding the ammonium concentration. The method was applied to aqueous extracts of solid and liquid fertilizers; recoveries from spiked samples were >97%.
Ammonium Chemiluminescence Interferences

"Rapid Determination Of Nitrogen, Phosphorus And Potassium In Fertilizers By Flow Injection Analysis"
Analyst 1977 Volume 102, Issue 1219 Pages 714-722
E. H. Hansen, F. J. Krug, Animesh K. Ghose and J. Ruzicka

Abstract: Nitrate, K, phosphate, and NH3 were determined in fertilizers by flow injection analysis of samples of 30 µL (and as low as 5 µL) using potentiometric and spectrophotometric detection; 85-120 samples per h were analyzed with high reproducibility and low reagent consumption. The results agreed well with those obtained by the fertilizer manufacturers by conventional techniques. Based on the flow injection technique and routinely using sample injections of 30 µL, and as low as 5 µL, reliable and sensitive methods for the determination of nitrate, potassium, phosphate and ammonia in fertilisers are described in which potentiometric and spectrophotometric detection is used. At sampling rates of 85-120 samples per hour high reproducibility of measurement and low reagent consumptions were achieved. The good agreement between the results obtained with the flow injection methods and those attained by the manufacturer of the fertilisers with conventional techniques shows that flow injection analysis is potentially suitable for the routine analysis of these and similar substrates.
Ammonia Nitrate Nitrogen Nitrogen, total Phosphorus Potassium Electrode Electrode Potentiometry Spectrophotometry Method comparison

"Flow Injection Analysis Of Environmental Samples For Nitrate Using An Ion Selective Electrode"
Analyst 1977 Volume 102, Issue 1219 Pages 705-713
E. H. Hansen, Animesh K. Ghose and J. Ruzicka

Abstract: NO3- in soil extracts, wastewater, and fertilizer solutions was determined by addition of a pH 9.5 buffer of 10^-2 M Na tetraborate + 10^-2 M NaOH and measuring the peak max. value in a flow injection system with a NO3--selective electrode. Aqueous extracts of particulate NO3- in air were analyzed without pretreatment. The electrode consisted of tetraoctylammonium bromide in di-Bu phthalate and was calibrated at 10^-5 - 10^-2 M NO3-. For injection of 0.3 mL samples the anal. rate was 90 samples/h. The standard deviation was typically 0.2-0.5 mV, equivalent to 1-2%. The electrode lifetime was 2-3 months. A method is proposed for identifying and correcting for the presence of interferents by observing the shape of each peak and determining its negative elevation. Based on the flow injection principle and employing a nitrate electrode situated in a flow-through cell, a simple, reliable and sensitive method for the automated determination of nitrate and its use for analyzing soil extracts, waste waters, fertiliser solutions and air samples are described. At a sampling rate of 90 samples per hour a standard deviation of only 1-2% is typical. A new approach to identifying and correcting for the presence of interfering species in potentiometric measurements is discussed.
Nitrate Electrode Apparatus Interferences

"Flow Injection Spectrophotometric Determination Of The Biuret Content In Urea Fertilizers"
Analyst 1990 Volume 115, Issue 3 Pages 319-321
Joanna Szpunar-Lobiska, Marek Trojanowicz and Liliana Ilcheva

Abstract: Flow injection systems are described (with diagrams). Fertilizer solution (50 µL) was injected into water carrier stream (0.7 mL min-1) and the stream was passed through a cation-exchange column (2 cm x 3 mm) packed with Dowex 50-X8 (100 to 200 mesh). The solution was mixed with 0.1 M sodium tartrate in 0.25 M NaOH (2.1 mL min-1) and 0.01 M CuSO4 in acidified water (1.4 mL min-1) and the absorbance was measured at 550 nm. Calibration graphs of biuret in the sample were rectilinear up to 5.0 mg mL-1; coefficient of variation were 1.2 to 2.5%. Recoveries were 98.9 to 104.5%. The only interferent, NH3, was removed with the ion-exchange column. Results agreed well with those by conventional methods.
Biuret Ion exchange Spectrophotometry Column Dowex Calibration Interferences Method comparison

"Multi-insertion Of Small Controlled Volumes Of Solutions In A Flow Assembly For Determination Of Nitrate And Nitrite With Proflavin Sulfate"
Analyst 1998 Volume 123, Issue 3 Pages 429-434
J. Mart&iacute;nez Calatayud, J. V. Garc&iacute;a Mateo and V. David

Abstract: A simple, maintenance-free, noncontaminating and completely automated flow system was developed for non-simultaneous determinations of nitrite and nitrate, in which spectrophotometric measurements at 328 nm were performed on the nitrite reaction with proflavin sulfate [bis(3,6-diaminoacridinium)sulfate]. The sample solutions were automatically inserted into phosphate buffer (pH 6.8) containing 10 mM EDTA by using a programmable solenoid valve; then they flowed through a 6.4 m x 0.5 mm id PTFE coil, wrapped around an 8 W low pressure Hg lamp, and finally they merged with a HCl solution of proflavin. With the lamp off the nitrite in the sample was selectively measured with a sensitivity of 0.75 x 104 absorbance (linearity range up to 0.6 absorbance; detection limit of 1.9 x 10^-7 M). With the lamp on, to determine the sum of nitrite + nitrate there was a decrease in sensitivity of 41% vs. that of the selective variant for nitrite determination The sample throughput was 15 h-1 and the relative standard deviation at a 6.4 x 10^-5 M level of nitrate was 0.4% (n = 15). Many interferences were studied and simple methods of correcting for them were applied to analyze samples such as waters, soils, fertilizers and meat. (26 References)
Nitrate Nitrite Spectrophotometry Automation Injection technique UV reactor Photochemistry Buffer Interferences EDTA Differential detection

"Flow Injection Potentiometric Determination Of Phosphate In Waste Waters And Fertilizers Using A Cobalt Wire Ion-selective Electrode"
Analyst 1998 Volume 123, Issue 7 Pages 1635-1640
Roland De Marco, Bobby Pejcic and Zuliang Chen

Abstract: Flow injection potentiometric (FIP) determinations of dihydrogen phosphate (H2PO4-) in fertilizers and waste waters were undertaken using a cobalt wire phosphate ion selective electrode (ISE). The Co wire electrode was used in the FIP determination of phosphate in a carrier containing 4 x 10^-2 mol L-1 potassium hydrogen phthalate (KHP) at pH 5. The FIP technique was validated for fertilizer and waste water samples against standard spectrophotometric methods of anal. FIP is a highly selective and accurate technique for the determination of phosphate in fertilizers [i.e., the FIP and spectrophotometric data compare to within a few percent (relative)]. A significant chloride interference occurs in waste water samples; however, this problem can be eradicated by using the chloride selectivity coefficient, chloride concentrations determined independently using ion-selective electrode potentiometry. The discrepancy between correlated FIP and spectrophotometric data for phosphate in waste waters is generally ±5% (relative). X-ray photoelectron spectroscopic and electrochemical impedance spectroscopic (EIS) results suggest that the Co oxide surface film of the electrode is dissolved in phosphate media, facilitating the corrosion process that regulates the response of the Co wire electrode. The EIS response of the Co wire electrode is dependent on both the pH and phosphate content of the solution A charge-transfer reaction mechanism, and accompanying Nernst equation, probably explain the phosphate response of the Co wire electrode.
Phosphate Electrode Electrode Potentiometry Apparatus Detector Method comparison Interferences

"Determination Of Phosphorus As Molybdovanadophosphoric Acid In Phosphate Rock With A Flow Injection Procedure"
Fresenius J. Anal. Chem. 1981 Volume 307, Issue 5 Pages 373-377
Willem D. Basson, Jacobus F. van Staden and Peter M. Cattin

Abstract: Based on the flow injection principle and by using small sample volumes and splitting of the colorimeter output, a good reliable and reproducible method for the determination of P2O5 in phosphate rock covering the range of 0-40% on a routine basis was achieved. The system described is suitable for the routine analysis of P2O5 in the prepared phosphate rock samples at a rate of approximately 90 samples per hour with a coefficient of variation of better than 1%.
Phosphorus Phosphorus pentoxide Spectrophotometry Signal splitting

"Potentiometric FIA System With Reactor Based On Natural Urease Source And Tubular Detector Of Ammonium-ions Determination Of Urea In Fertilizers"
Anal. Sci. 1997 Volume 13, Issue 4 Pages 589-594
L. R. JUNIOR, G. de OLIVEIRA NETO, J. L. F. C. LIMA, M.C. B. S. M. MONTENEGRO and V. L. SILVA

Abstract: An FIA system was developed to analyze urea by monitoring ammonium ions generated by enzymatic degradation with a tubular ion-selective electrode containing nonactin on polyvinyl chloride (PVC) membrane. As an urease source, 120 mg of the leguminous canavalia brasiliensis were immobilized in an enzymatic reactor with glutaraldehyde. Ammonium ions are converted to ammonia by an alkaline solution, 1 mol L-1 NaOH, and permeates through a polytetrafluoroethylene membrane until the detector. The method can be used in an urea concentration range of 2.5 x 10^-4 to 2.5 x 10^-3 mol L-1 (25.0°C). Analysis of 25 µl commercial samples of fertilizers, showed a relative error of 0.2% with a high selectivity to the species present. 19 References
Urea Potentiometry Electrode Electrode Teflon membrane Immobilized enzyme

"Determination Of Major Nutrients In Fertilizers"
Bunseki 1978 Volume 1978, Issue 11 Pages 803-809
Koshino, M.

Abstract: A review, with 42 refs., discussing official fertilizer anal. methods and determinations of N, P, K, B, Ca, and Mg in fertilizers. (SFS)
Boron Nitrogen Nitrogen, total Phosphorus Potassium Spectrophotometry

"Determination Of Biuret In Fertilizers By Flow Injection Analysis With Electrochemical Detection"
Izv. Khim. 1991 Volume 24, Issue 3 Pages 414-419
Ilcheva, L.I.;Dakashev, A.D.

Abstract: Sample was passed through a column filled with Cu(OH)2 (prep. described) and the Cu(II) - biuret complex formed was detected by measuring the oxidation current on a porous Pt electrode in NaOH medium. Recoveries were 99.1 to 100.5% with coefficient of variation of 0.75 to 1.54%. The method was applied to the determination of biuret in commercial fertilizers.
Biuret Electrochemical analysis Electrode Electrode Column

"Indirect Atomic Absorption Spectrophotometric Method For The Determination Of Nitrate"
J. Chem. Soc. Pak. 1985 Volume 7, Issue 3 Pages 209-213
Anwar, Jamil; Tanveer ul Haque (SFS)

Abstract: An indirect atomic absorption spectrophotometric method for the determination of 0.5-5 mmol NO3- is described. The method is based on the formation of the insoluble ternary complex, [Ag(Phen)2]NO3 (Phen = 1,10-phenanthroline) by adding an excess of [Ag(Phen)2]+ solution to the NO3- sample. The absorbance of the unreacted silver ions was measured in an air-C2H2 flame. The effect of various ions was investigated. The method is successfully employed for the determination of NO3- in fertilizer samples.
Nitrate Spectrophotometry Indirect Interferences Complexation

"Fundamentals And Applications Of Flow Injection Analysis. 2. Application Of The Method"
Jpn. J. Soil Sci. Plant Nutr. 1987 Volume 58, Issue 2 Pages 247-251
Koshino, Masayoshi

Abstract: A review on the application of flow injection analysis to soils and fertilizers. Determination of phosphorus, NH4+, NO2-, NO3-, SO42-, etc. with various detection systems such as spectrophotometry, electrochemical methods, atomic absorption spectrometry, and ICP-AES were explained. 29 references.
Phosphorus Ammonium Nitrate Nitrite Sulfate Spectrophotometry Spectrophotometry Spectrophotometry Electrochemical analysis Review

"Simultaneous Determination Of Urea- And Ammonia-nitrogen In Soil Extracts And Water By High Performance Liquid Chromatography"
Soil Sci. Soc. Am. J. 1988 Volume 52, Issue 4 Pages 969-973
A. Abshahi, S. S. Goyal and D. S. Mikkelsen*

Abstract: A HPLC system is described that utilizes three columns, viz, a guard column of Pellicular refill media - silica, a column of Partisil 10 SCX cation-exchange resin for separation of NH4+, and a column of urease - Nucleosil for catalysis of the hydrolysis of urea to NH4+. The mobile phase is 20 mM KH2PO4 of pH 6.9, and the NH4+ is detected fluorimetrically, after post-column derivatization with phthalaldehyde, at 455 nm (excitation at 344 nm). This rapid method can be applied in analysis of soil, water and fertilizers. Recoveries were almost quantitative.
Ammonia, nitrogen Urea HPIC Fluorescence Sample preparation Catalysis Immobilized enzyme Post-column derivatization

"Applications Of Flow Injection To Samples Of Agricultural Interest"
Tec. Lab. 1985 Volume 9, Issue 120 Pages 18-24
Martinez Calatayud, J.

Abstract: A review is presented, with 50 references, of methods applicable to soil, plants, fertilizers and water.
Review

"Determination Of Iron(III) By Spectrophotometric Flow Injection Analysis"
J. Anal. Chem. 1985 Volume 40, Issue 10 Pages 1859-1865
Kuznetsov, V.V.

Abstract: Fertilizers of superphosphate type are analyzed for ~2.3 to 3% of Fe2O3. The carrier stream, supplied from a Mariotte bottle at 3 mL min-1, is 40 mM in Na sulfosalicylate; its pH is 2 (HCl) or 9 (aqueous NH3) when determining 1 to 5 or 10 to 50 µg mL-1 of Fe, respectively. The 70-cm glass mixing coil has i.d. of 0.5 mm; 10 µL samples of acid extracts of the fertilizers can be injected at a rate of 200 samples h-1. The absorbance is measured at 490 nm (at pH 2) or 420 nm (pH 9); a 40 µL (2-cm) flow-through cell is used. The absorbance signal is digitized and the peak heights are printed automatically.
Iron(III) Spectrophotometry

"Determination Of Cadmium In Fertilizer By Atomic Absorption Spectrometry After APDC-MIBK Extraction In Continuous-flow"
Zhongguo Kexue Jishu Daxue Xuebao 1990 Volume 20, Issue 1 Pages 61-66
Zhao Huazhang, Lars-Goran Danielsson, Folke Ingman

Abstract: In a modified extraction-atomic absorption spectrometric system, APDC was mixed with MIBK and the mixture passed through a 5 cm segment coil before being mixed with acid-digested fertilizer solution in a 2.5 m extraction coil. The organic extract was led through a phase separator into an air/acetylene flame atomic absorption spectrometer. The APDC concentration was 0.2% for Cd determination and 0.5% for determination of seven other elements. Fe at >0.5 mg in 50 mL of solution interfered with Cd determination, but KI (2 mL, 30%) could mask at least 3 mg Fe. The detection limit for Cd was 1 ppb. Sensitivity was increased 23-fold for Cd and 11-17 fold for the other elements in comparison with results obtained by flame spectroscopy with direct aspiration of aqueous solution. The relative standard deviation was 1.9%, and recovery of added Cd was 98%.
Cadmium Spectrophotometry Sample preparation Extraction MIBK