Optically active triosmium clusters containing the cysteine ligand

The reactions of cysteine ethyl ester with a series of triosmium clusters have been studied. Enantiomeric (-H)Os₃{-SCH₂CH(CO₂Et)NH₂}(CO)₁₀ and diastereomeric (-H)Os₃{-²-SCH₂CH(CO₂Et)NH₂}(CO)₉ forms of the optically active cluster complexes have been obtained. Diastereomeric clusters have been separated by TLC on Silufol plates. The treatment of the enantiomeric complex (-H)Os₃{-SCH₂CH(CO₂Et)NH₂}(CO)₁₀ with the trimethylamine oxide yields the diastereomeric pair (-H)Os₃{-²-SCH₂CH(CO₂Et)NH₂}(CO)₉. The structures of the complexes obtained have been established on the basis of IR,¹H NMR and mass spectrometry as well as X-ray analysis data.Translated fromIzyestiya Akademii Nauk. Seriya Khimicheskaya, No. 11, pp. 1981–1984, November, 1993.     

Determination of traces of sodium alkylbenzenesulphonate by high-performance liquid chromatography. Application to water

Summary For the trace determination of sodium alkylbenzenesulphonate (ABS) by HPLC the following conditions were employed: Shimadzu ZORBAX SIL Column (5 m, 4.6 mm i.d. x 150 mm) as stationary phase, 0.2% ammoniaethanol (v/v) as mobile phase, UV detector at 225 nm, injection volume 12 l. The chromatograms of ABS were simple and sharp (detection limit of ABS 0.02 g in 12 l of ethanol). The calibration curves of ABS were linear in a concentration range of 0.03 0.3 g in 12 l of ethanol. In the case of linear sodium dodecylbenzenesulphonate positive errors of 1 4% were caused by non-ionic surfactants or laurylsulphate (6 times excess), 10 50% positive errors were caused by 2 6 times excess of household detergents.Standard water samples containing ABS were treated with a weak base anion-exchange resin, the adsorbed ABS were eluted, and then determined either by HPLC or by the methylene blue spectrophotometric method. Recoveries of ABS in water were about 92 107% by HPLC.

---

Bestimmung von Spuren Natriumalkylbenzolsulfonat mit Hilfe der HPLC. Anwendung auf Wasser

Zusammenfassung Für die Spurenbestimmung von Natriumalkylbenzolsulfonat (ABS) durch HPLC werden die folgenden Bedingungen empfohlen:Shimadzu ZORBAX SIL (5 m, 4,6 mm x 150 mm) als stationäre Phase, 0,2% Ammoniak/Ethanol als mobile Phase, UV-Detektor bei 225 nm, Injektionsvolumen 12 l. Die erhaltenen Chromatogramme sind einfach und scharf (Nachweisgrenze 0,02 g in 12 ml Ethanol). Die Eichkurven sind im Konzentrationsbereich von 0,03–0,3 g in 12 l Ethanol linear. Im Falle des linearen Natriumdodecylbenzolsulfonats werden bei Anwesenheit von nicht-ionischen oberflächenaktiven Substanzen oder von Laurylsulfat in 6fachem Überschuß positiver Fehler von 1–4% erhalten; bei 2–6fachem Überschuß von Haushaltswaschmitteln ergeben sich positive Fehler von 10–50%.Standard-Wasserproben werden zunächst einer Behandlung mit einem Anionenaustauscher unterzogen, die adsorbierten ABS eluiert und durch HPLC oder nach der Methylenblaumethode analysiert. Wiederfindungsraten liegen bei 92–107%.

     

Spectrophotometric determination of palladium with 4-(2-pyridylazo)-resorcinol (PAR)

Summary A spectrophotometric method for the determination of palladium is described using 4-(2-pyridylazo)-resorcinol as reagent. The method involves the formation of two red coloured chelates of palladium-PAR at p_H 4.0 and 10.5 respectively. The colour reactions have sensitivity of 0.0085g cm^–2 and 0.0071g cm^–2 for logI ₀/I= 0.001. The effects of p_H, time, order of addition of reagents, temperature etc. have been investigated. The composition of the complexes (metalreagent) have been confirmed by two methods as 11 (at p_H 4.0) and 32 (at p_H 10.5).

---

Zusammenfassung Eine spektrophotometrische Methode zur Palladiumbestimmung mit PAR [4-(2-Pyridylazo)-resorcin] wurde beschrieben. Zwei rotgefärbte Chelate werden bei p_H 4,0 bzw. 10,5 gebildet. Die Empfindlichkeit der beiden Reaktionen beträgt 0,0085 bzw. 0,0071g · cm^–2. Der Einfluß von p_H, Zeit, Reihenfolge der Reagenzien, Temperatur usw. wurde untersucht. Die Zusammensetzung der Komplexe entspricht dem Molverhältnis Pd: Reagens= =11 bei p_H 4,0 bzw. 32 bei p_H 10,5.

     

Spectrophotometric determination of mercury with 5,10,15,20-tetrakis(3-chloro-4-sulfophenyl)porphine by flow injection analysis

5,10,15,20-tetrakis(3-chloro-4-sulfophenyl)porphine (m-Cl-TPPS₄) was synthesized and used for the Spectrophotometric determination of mercury by flow injection analysis. A pseudo-first-order reaction kinetic mechanism was proposed with a rate constant of 0.8 min^–1 for Hg(II) withm-Cl-TPPS₄ in the presence of 8-hydroxyquinoline in a medium of 1.0M acetic acid and sodium acetate buffer solution (pH 6.22). In the optimum conditions of reaction temperature (85 ° C), stopped-flow time (60 s) and sampling volume (100 l), the method's relative standard deviation was 0.82% (n = 12) at 5.0 g ml^–1 mercury, with a linear range of 0–12.0 g ml^–1 and an analytical frequency of 60h^–1. The detection limit (3) was 0.025 g ml^–1. Interference studies showed that most metal ions co-existing with Hg²⁺ could be tolerated at 100-fold excess levels, but Zn²⁺, Cu²⁺ and Mn²⁺ needed to be masked. The method has been applied to the analysis of water samples with satisfactory results.     

Differential pulse voltammetric methods for the simultaneous estimation of uranium-iron and uranium-cadmium mixtures in solution

Differential pulse voltammetric methods have been developed for the simultaneous estimation of the constituents of uranium-iron and uranium-cadmium mixtures in solution. A mixture of 1M H₃PO₄–1M KH₂PO₄ (with a pH1.5), was found to be the most ideal supporting electrolyte for both methods, among many that were evaluated for their suitability. In uranium-iron mixtures the calibration for iron was found to be linear up to 150 g ml^–1 (r²=0.9986), while that of uranium up to 500 g ml^–1 (r²=0.999). Iron at 6.7 g ml^–1 level could be determined in the presence of 800 fold uranium (wt/wt) without significant interference. Uranium at 21 g ml^–1 level could be analyzed with 5-fold iron (wt/wt). This upper limit of iron was due to the precipitation of iron as phosphate. In the case of uranium — cadmium mixtures, cadmium calibration for cadmium was found to be linear up to 1300 g ml^–1 (r²=0.9993). Concentration levels of 4.6 g ml^–1 Cd could be determined at a 500-fold excess (wt/wt) of uranium. Uranium calibration was linear up to 500 g ml^–1 (r²=0.999) and 21 g ml^–1 uranium could tolerate up to a 1000-fold excess of cadmium (wt/wt). Both procedures could tolerate 10 g ml^–1 levels of metal ions, such as chromium, copper, manganese, molybdenum and vanadium.     

Spectrofluorimetric flow-injection determination of cerium in carbon and low alloy steels

Cerium can be determined spectrofluorimetrically (_em 350 nm, _ex 260 nm) based on the relatively intense native fluorescence of the cerium(III) aquo-ion. The main potential interference in the analysis of steel from iron(III), cerium(IV) and chromium(VI) are removed by use of a carrier solution containing 2.5% w/v hydroxylammonium chloride. The slight residual interference from iron(II) can be corrected by a matrix matching factor linearly related to the amount of iron present. The calibration graphs are linear over the range 0–7 g ml^–1 based on 250 l injection volumes. The sampling rate was 30 h^–1. The relative standard deviation was 2.0% (n=5) at 3 g ml^–1 cerium. The system has been applied to the determination of cerium in carbon or low alloy steels.     

Characterization of airborne particulates by laser microprobe mass analysis

Summary Laser microprobe mass analysis (LAMMA) was applied to characterize aerosol particles collected and separated from 16m to 0.06m by a low pressure cascade impactor. Positive ion LAMMA spectra showed characteristic molecular peaks such as PbCl⁺, a series of Si₂O⁺–Si₂O₄ ⁺ and NaAl₂Si₂O₂ ⁺–NaAl₂Si₂O₅ ⁺, and TiO⁺ in 0.06–0.12m, 0.5–1m and 4–8m fraction, respectively. In the negative ion LAMMA spectra, it was observed that the fragment peaks of sulfate ions were deficient above 2m and those of nitrate ions were deficient under 2m. LAMMA allows remarkable insights into the chemical nature of aerosol particles.

---

Charakterisierung luftgetragener Teilchen durch Laser-Microprobe-Massenspektrometrie

Zusammenfassung Laser-Microprobe-Spektrometrie (LAMMS) wurde zur Analyse atmosphärischen Aerosols herangezogen, welches im Korngrößenbereich zwischen 16m und 0.06m mit einem Niederdruckkaskadenimpaktor fraktioniert gesammelt wurde. Positive LAMMS-Spektren zeigten charakteristische molekulare Peaks, wie etwa PbCl⁺, eine Serie von Si₂O⁺–Si₂O₄ ⁺ und NaAl₂Si₂O₂ ⁺–NaAl₂Si₂O₅ ⁺, sowie TiO⁺ in der 0,06–0,12-m,- 0,5–1–m- bzw. 4–8-m-Fraktion. In den negativen LAMMS-Spektren konnten über 2m keine Fragmentpeaks für Sulfationen, unter 2m. keine für Nitrationen beobachtet werden. LAMMS ermöglicht eine bemerkenswerte Einsicht in die chemische Natur von Aerosolteilchen.

     

Thiazane-2, 4-dithione and its 3-aryl derivatives

Reaction of 2-thiothiazane-4-one and its 3-aryl derivatives with phosphorus pentasulfide in toluene or dichloroethane gives thiazane-2, 4-dithione, or the corresponding 3-aryl derivatives. The compounds are characterized by absorption maxima (or bends) at three bands, 244–262, 315–321, and 339–350 m. The IR spectra exhibit bands at 14.93 (C-S-C), 6.64, and 6.84 (N-C-S), and 7.34, 8.43, 7.14 (CH₂).     

Extractive spectrophotometric determination of niobium(V) using 3-hydroxyflavone

A simple, rapid method for the spectrophotometric determination of niobium in trace amounts is presented, employing 3-hydroxyflavone as a ligand for the complexation of the metal ion and extracting the coloured complex into chloroform from 4M HClO₄ solution. Beer's law is obeyed in the range 0.0 to 3.2 g ml^–1 Nb(V), with a lower working limit of 0.1 g ml^–1 Nb(V). Molar absorptivity and Sandell's sensitivity of the complex at 395 nm are 4.088 × 10⁴l mol^–1 cm^–1 and 0.002g Nb(V) cm^–2, respectively. The stoichiometry of the complex is established as 12 by Job's and mole ratio methods. The method is free from the interference of a large number of analytically important elements. The proposed system handles satisfactorily the analysis of several samples of varying complexity. The results are highly reproducible with a relative standard deviation of 0.34% for 20 g of Nb.     

A toxic reagent-free method for normal-phase matrix solid-phase dispersion extraction and reversed-phase liquid chromatographic determination of aldrin,dieldrin, and DDTs in animal fats

A method for the determination of aldrin, dieldrin, DDT, DDE, and DDD contamination in animal fats (beef tallow, lard, and chicken fat) without using toxic reagents is developed, that uses high-performance liquid chromatography after the sample has been prepared by matrix solid-phase dispersion (MSPD) with acidic alumina oxide. A reversed-phase C₁-silica column with a mobile phase of 50% (v/v) ethanol solution (in water) and a photo-diode array detector were used for the determination. Average recoveries of the target compounds (0.2–5.0 g g^–1) ranged from 84–98%, with coefficients of variation of <5%. The limits of quantitation were 0.16 g g^–1 for AD, 0.10 g g^–1 for DD, 0.06 g g^–1 for DDT, 0.07 g g^–1 for DDE, and 0.05 g g^–1 for DDD. No toxic reagents were used at all.     

Half-sandwich metal diselenolate complexes Cp#M(NO)(SePh)2 (M = Mo or W; Cp# = Cp or MeCp) as ligands. Synthesis of selenolate-bridged heterobimetallic compounds

The reactions of half-sandwich diselenolate Mo and W complexes Cp^#M(NO)(SePh)₂ (M = Mo; Cp^# = Cp (1a), MeCp (1b); M = W; Cp^# = Cp (1c)) with (Norb)Mo(CO)₄, Ni(COD)₂ and Fe(CO)₅ have been investigated. Treatment of (1a), (1b) and (1c) with (Norb)Mo(CO)₄ in PhMe gave the bimetallic complexes: CpMo(NO)(-SePh)₂Mo(CO)₄ (2a), MeCpMo(NO)(-SePh)₂Mo(CO)₄ (2b) and CpW(NO)(-SePh)₂Mo(CO)₄ (2c) in moderate yields. Irradiation of (1a) and (1c) in the presence of Fe(CO)₅ gave heterobimetallic complexes CpMo(CO)(-SePh)₂Fe(CO)₃ (3a) and CpW(NO)(-SePh)₂Fe(CO)₃ (3c). Ni(COD)₂ reacts with two equivalents of (1a), (1b) and (1c) to give [CpMo(NO)(-SePh)₂]₂Ni (4a), [MeCpMo(NO)(-SePh)₂]₂Ni (4b) and [CpW(NO)(-SePh)₂]₂Ni (4c) in good yields. The new heterobimetallic complexes were characterized by i.r., ¹H-n.m.r., ¹³C-n.m.r. and EI-MS spectroscopy.     

Untersuchungen zur mikroanalytischen Bestimmung der langkettigen Fetts?uren im Blut

Zusammenfassung Für die im Plasma an Albumin gebundenen sog. freien Fettsäuren (FFS) wird ein neues gas-chromatographisches Analysenverfahren vorgestellt. Das Probenvolumen beträgt 50 l Serum oder Plasma. Die Extraktion erfolgt in 1,1 ml CHCl₃/CH₃OH (21, v/v) mit n-Heptadecansäure als innerem Standard (0,05 Val C₁₇₀/ml). Nach Eindampfen am Rotationsverdampfer werden die FFS im verschlossenen Reaktionskölbchen mit 20 l CH₃J/Essigsäureäthylester (11, v/v) über festem K₂CO₃ bei 90°C 1 h verestert. Die Varianz des Verfahrens errechnet sich bei 15 Parallelbestimmungen zu 4,85%.Vortrag anläßlich der Tagung Spurenanalyse, 2. bis 5. April 1973 in Erlangen.     

Magnetische Eigenschaften von Fe3Al und FeAl und spezifische Wärmen bei tiefen Temperaturen

Zusammenfassung Wir berechneten die magnetischen Momente, die in Verbindung mit Fe-Atomen in Fe–Al-Legierungen auftreten, für Umgebungen mit verschiedenen nächsten Nachbarn. Dazu analysierten wir die Ergebnisse aus früheren Neutronenbeugungsexperimenten und aus neuen Messungen der Magnetisierung an Fe₃Al-Proben mit bekannten Fernordnungsparametern. Die einander augenscheinlich widersprechenden Ergebnisse von Untersuchungen der magnetischen Eigenschaften können miteinander und mit dem Modell der atomaren Umgebung von nächsten Nachbarn in Einklang gebracht werden, wenn man die Ergebnisse eingehender magnetischer Messungen und Untersuchungen der spezifischen Wärme bei tiefen Temperaturen mit folgenden Vorstellungen zu erklären versucht: magnetische Cluster ( 21 _B), individuelle Momente des Fe ( 2,2 _B) und keine Momente, aber verstärkter Paramagnetismus der meisten Fe-Atome, je nach der lokalen atomaren Umgebung.

---

Magnetic properties and low temperature specific heat of Fe₃Al and FeAl

The moments associated with Fe atoms in Fe–Al alloys, with various nearest neighbor atomic environments, have been evaluated by analyzing earlier neutron diffraction results together with new magnetization data for a Fe₃Al specimen with known long range order parameters. The apparently contradictory reports on the magnetic properties of FeAl can be reconciled with one another and with the nearest neighbor atomic environment model by interpreting the results of detailed magnetic measurements and of a study of the low temperature specific heat in terms of magnetic clusters ( 21 _B), of individual Fe moments ( 2,2 _B) and of no moments, but enhanced paramagnetism for most Fe atoms, depending on the local atomic environment.

---

---

Mit 5 Abbildungen

---

Herrn Prof. Dr.H. Nowotny gewidmet.

---

Diese Arbeit entstand mit Unterstützung der U.S. National Science Foundation.     

Critical behavior and interfacial tension of mixtures of propylene glycol and ethylene glycol oligomers

This investigation presents an analysis of the critical behavior of mixtures of oligomers of propylene glycol, PG₁₇, and ethylene glycol, EG_n, withn=3, 4, 5, 6.4, 8.7, 12.1 and 22.1. The critical coordinates, _c andT _c were determined from the phase diagrams. The critical compositions compare very well with the Huggins-Flory predictions. The interaction parameter _n is around one for EG₃, EG₄ and EG₅ and it increases up to two for the higher oligomers. The break in the interaction parameter also corresponds to a minimum in the critical temperature. The phase diagrams and the interfacial tension were used to get the critical exponents and , respectively. The data were analysed with two approaches. First, from the temperature dependence of the length of the tie-lines and of the interfacial tension up to the upper critical solution temperature, UCST. Second, with the data at 30°C using the critical temperature of the systems as the variable. The first method led to =0.39±0.05 in good agreement with the result of the second method, =0.37±0.04. The exponents for the interfacial tension, , determined with the first method for PG₁₇ with EG_6.4, EG_8.7 and EG_12.1 are =1.66±0.11, 1.46±0.25 and 1.73±0.18, respectively. The second method led to =1.17±0.14. The critical exponents are compared to mean field and ising-3D predictions.     

Effect of Surfactants on the Immobilization of 4-(2-Pyridylazo)resorcinol on Silochroms

The effect of cationic surfactants (cetyltrimethylammonium bromide, cetylpyridinium bromide, and tetrabutylammonium perchlorate) and a nonionic surfactant (OP-7) on the conditions of the immobilization of 4-(2-pyridylazo)resorcinol (PAR) on three types of silica gel (Silochrom S-120 (200–350 m), Silochrom S-120 (315–500 m), and Silochrom S-80 (200–350 m)) was studied. It was found that OP-7 does not affect the adsorption of surfactants. The effect of cationic surfactants increases in the order tetrabutylammonium perchlorate < cetyltrimethylammonium bromide < cetylpyridinium bromide. The adsorption activity of silica gels increases in the order Silochrom S-120 (315–500 m) < Silochrom S-80 (200–350 m) < Silochrom S-120 (200–350 m). Cetylpyridinium bromide provides full immobilization of PAR on silica gel Silochrom S-120 (200–350 m) in the pH range 2–9.     

Trace and minor elements in four commercial honey brands

Instrumental neutron activation analysis was used to measure the concentrations of 24 elements in four honey brands commercially available in Austin, Texas (USA). The measured elements (and concentration) were: As, (<30 ng/g); Ba, (<2 g/g); Br, (0.24–0.49 g/g); Ce, (<20 ng/g); Co, (9–180 ng/g); Cr, (37–64 ng/g); Cs, (<3–45 ng/g); Fe, (<4–15.9 g/g); Hf, (<3 ng/g); Hg, (1 ng/g); K, (91–230 g/g); La, (<4 ng/g); Na, (20.3–25.3 g/g); Ni, (0.39–0.77 g/g); Rb, (68–340 ng/g); Sb, (13–61 ng/g); Sc, (<0.3–200 ng/g); Se, (<20 ng/g); Sm, (<9 ng/g); Sr, (<2 ng/g); Th, (<4 ng/g); U, (<30 ng/g); Zn, (3.36–4.61 g/g); and Zr, (<0.5–0.84 g/g). The results obtained were compared to the concentration of the same elements in honey produced or commercially available in Turkey, Mexico, El-Salvador, China, Czechoslovakia and Yugoslavia.     

The oxidative addition of diphenylphosphine and monophenylphosphine to the electron-rich rhenium-rhenium triple bond. The isolation and characterization of compounds that contain the four-center Re(μ-X)(μ-PR2)Re cluster (X=halide)

Diphenylphosphine oxidatively adds to the ReRe bonds of Re₂ X ₄(-dppm)₂ (X=Cl or Br; dppm=Ph₂PCH₂PPh₂) and Re₂Cl₄(-dpam)₂ (dpam=Ph₂AsCH₂AsPh₂) to afford the dirhenium(III) complexes Re₂(-X)(-PPh₂)HX ₃(-LL)₂. The dppm complexes have also been prepared from the reactions of Re₂(-O₂CCH₃)X ₄(-dppm)₂ with Ph₂PH, and a similar strategy has been used to prepare Re₂(-Cl)(-PPh₂)HCl₃(-dmpm)₂ (dmpm=Me₂PCH₂PMe₂) from Re₂(-O₂CCH₃)Cl₄(dmpm)₂. Phenylphosphine likewise reacts with Re₂ X ₄(-dppm)₂ to give Re₂(-X)(-PHPh)HX ₃(-dppm)₂. An X-ray crystal structure determination on Re₂(-Cl)(-PPh₂)HCl₃(-dppm)₂ confirms its edge-shared bioctahedral structure. This complex crystallizes in the space group (No. 148) witha=21.699(3) Å, =84.50(4)°,V=10084(5) ų, andZ=6. The structure was refined toR=0.049 (R _w 0.069) for 5770 data withI>3.0(I). The Re-Re distance is 2.5918(7) Å. Oxidation of the bromide complex Re₂(-Br)(-PPh₂)HBr₃(-dppm)₂ with NOPF₆ produces the unusual dirhenium(III, II) cation [Re₂(-H)(-Br)[P(O)Ph₂]Br₂(NO)(-dppm)₂]⁺ which has been structurally characterized as its perrhenate salt, [Re₂(-H)(-Br)[P(O)Ph₂]Br₂(NO)(-dppm)₂]ReO₄ · 2CH₂Cl₂. This complex crystallizes in the space group (No. 2) witha=14.187(7) Å,b=16.419(5) Å,c=16.729(5) Å, =98.76(2)°, =110.11(3)°, =104.66(3)°,V=3414(6) ų,Z=2. The structure was refined toR=0.040 (R _w =0.051) for 5736 data withI>3.0(I). The presence of a phosphorus-bound [P(O)Ph₂]^– ligand, a linear nitrosyl and a bridging hydrido ligand has been confirmed. The Re-Re distance is 2.6273(8) Å.     

Quantitative chemical analysis on paper. I

Summary A method has been proposed for the determination of small quantities of Cl^–, SCN^– and I^– in mixtures. The method is based on the use of filter paper evenly impregnated with Ag₂CrO₄. The method permits the determination of 5 to 50g of Cl^–; 15 to 100g of I^– and 10 to 150g of SCN^– with an accuracy of 1.5%.The method may also be used for determination of SCN^– alone.

---

Zusammenfassung Ein Verfahren für die Bestimmung kleiner Mengen Chlorid, Rhodanid und Jodid in deren Gemischen wird vorgeschlagen. Es beruht auf der Verwendung eines mit Silberchromat gleichmäßig imprägnierten Filtrierpapierstreifens und ermöglicht die Bestimmung von 5 bis 50g Chlorid,15 bis 100g Jodid und 10 bis 150g Rhodanid mit einer Genauigkeit von 1,5%. Das Verfahren kann auch für die Bestimmung von Rhodanid allein verwendet werden.

---

Résumé On a proposé une méthode pour le dosage de petites quantités de Cl^–, SCN^–, et I^– en mélanges. La méthode est fondée sur l'emploi d'un papierfiltre uniformément imprégné d'Ag₂CrO₄. Elle permet le dosage de 5 à 50g de Cl^–, 15 à 100g d'I^– et de 10 à 150g de SON^–, à la précision de 1,5%. On peut aussi utiliser la méthode pour le dosage de SCN^– seul.

     

Spectrophotometric determination of nitrite in environmental waters using column preconcentration on biphenyl

Column preconcentration methods have been established for the spectrophotometric determination of trace nitrite with sulfanilic acid (SA) orp-aminoacetophenone (AAP) as the diazotizable aromatic amine andN, N-dimethylaniline (DMA) or 1-aminonaphthalene (AN) as the coupling agent, using differention-pairs co-precipitated with biphenyl. Nitrite ion reacts with SA in the pH range 2.0–3.0 and AAP in the pH range 1.7–3.0 in HCl medium to form water-soluble colourless diazonium cations. These cations are subsequently coupled with DMA in the pH range 3.7–6.1 for the SA-DMA system and AN in the pH range 1.7–2.3 for the AAP-AN system to be retained on microcrystalline biphenyl packed in a column. The solid mass is dissolved out from the column with 5 ml of DMF and the absorbance is measured by a spectrophotometer at 420 nm for the SA-DMA system and at 517 nm for the AAP-AN system. The calibration was linear over the concentration ranges 0.3–6.0 g of nitrite in 5 ml of DMF solution (i.e., 0.02–0.40 g/ml in the sample solution) for the SA-DMA system and 0.5–7.0 g of nitrite in 5 ml of DMF solution (i.e., 0.03–0.47 g/ml in the sample solution) for the AAP-AN system. The molar absorptivity and Sandell's sensitivity were respectively 2.63 × 10⁴lmol^–1cm^–1 and 1.75 × 10^–3 g cm^–2 for SA-DMA and 3.28 × 10⁴lmol^–1 cm^–1 and 1.40 × 10^–3 g cm^–2 for AAP-AN. The concentration factors were 4 and 16 for SA-DMA and AAP-AN, respectively. The detection limits were 0.0138 and 0.0175 g/ml NO₂ ^– for SA-DMA and AAP-AN, respectively. Seven replicate determinations of a solution containing 3.5 g of nitrite gave mean absorbances of 0.410 and 0.500 with relative standard deviations of 0.51 and 0.55% for SA-DMA and AAP-AN, respectively. Interference from various foreign ions has been studied and the methods have been applied to the determination of nitrite in environmental samples.