2,4-Toluene diamine (TDA), a class A carcinogen, is a major raw material for the production of toluene diisocyanate (TDI), which is one of the precursors for the production of polyurethane foams (PU). This review deals with 2,4-toluene diamine’s (TDA) carcinogenicity, analytical techniques, biodegradation and use as a biosensor for biogenic and synthetic amines, emphasizing various carcinogenicity studies by 2,4-TDA on animals and humans. This review reports some publications of the analysis of body fluid samples of workers from a PU producing factory for presence of TDA and TDI, since TDI gets absorbed into the worker’s body, getting metabolized into TDA. Biodegradations of 2,4-TDA by various researchers are reported and also our own research experience with biodegradation of 2,4-TDA using Aspergillus nidulans isolated from soil site at a polyurethane foam dumping site have been discussed in this review. Biosensors for various biogenic and synthetic amines are discussed.

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A novel fluorometric method has been developed for rapid determination of DNA and RNA with calcein-neodymium complex as a fluorescence probe. The method is based on the fluorescence enhancement of calcein-Nd(III) complex in the presence of DNA or RNA, with maximum excitation and emission wavelength at 489 nm and 514 nm, respectively. Under optimal conditions, the calibration graphs are linear over the range 0.5 - 3.0 μg/ml for both DNA and yeast RNA, 0.4 - 2.0 μg/ml for fish sperm DNA (FS DNA) and 0 - 3.0 μg/ml for calf thymus DNA (CT DNA). The corresponding detection limits are 15.1 ng/ml for DNA, 21.2 ng/ml for yeast RNA, 10.5 ng/ml for FS DNA and 8.9 ng/ml for CT DNA. The interaction mechanism for the binding of calcein-Nd(III) complex to DNA is also studied. The results of absorption spectra, fluorescence polarization measurements and thermal denaturation experiments, suggested that the interaction between calcein-Nd(III) complex and DNA is an electrostatic interaction.

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A stepwise titrimetric method has been developed for the simultaneous determination of pharmaceutical quaternary ammonium salts (R₄N⁺) and aromatic amines (R₃N). The method is based on the solvent extraction of R₄N⁺ and R₃NH⁺ with an ion association reagent. Sodium tetrakis(4-fluorophenyl)borate and sodium tetraphenylborate were used as titrants and potassium tetrabromophenolphthalein ethyl ester (TBPE) was used as an indicator. The ion associate which formed between R₄N⁺ ion and TBPE made a blue color in 1,2-dichloroethane, while the ion associate formed between R₃NH⁺ and TBPE showed a red-violet one. Sample solutions containing quaternary ammonium and/or amine compounds were titrated with sodium tetrakis(4-fluorophenyl)borate or sodium tetraphenylborate. When one drop of excess titrant was added, the color of the organic phase turned from blue or red-violet to yellow at the equivalence point. On the other hand, in the mixture of R₄N⁺ and R₃N, the color changed from blue to red-violet at the first equivalence point, and then its color turned to yellow at the second equivalence point. The quaternary ammonium compound and aromatic amine in pharmaceuticals could be simultaneously and successfully determined by the proposed titration method.

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A handy and simple detection cell was constructed using a mixing joint for end-column electrochemical detection in capillary electrophoresis (CE). The cell allows for positioning of the working electrode at the end of the separation capillary without the aid of micropositioners. The design facilitates the exchange of electrodes and capillaries without the need to refabricate the entire capillary-electrode setup. The cell can be assembled in a short period of time. Alignment with the joint screw proved to be reproducible for working electrodes of copper and gold. The advantages of reduced time and low cost make the device very attractive for the routine analysis of electroactive species, such as carbohydrates and their derivatives, purine bases and nucleosides, amino acids, and catecholamines etc. by CE with electrochemical detection.

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The construction and general performance characteristics of three piezoelectric quartz crystal sensors responsive to the pentoxyverine are described here. This kind of non-potentiometric sensing method is based on use of ion-pair complexes of the pentoxyverine cation with three counter anions, namely, tungstophosphate, tetraphenylborate and picrolonate. The complexes were embedded in a PVC matrix. Adsorption of the pentoxyverine ion on the complex caused a frequency decrease of the crystal. The frequency decrease was proportional to the amount of adsorbed analyte. The influencing factors were investigated in detail, and then optimized. The proposed sensors exhibit reasonable selectivity and a higher sensitivity than the potentiometric sensors. For a sensor modified with pentoxyverine-phosphotungstate, the calibration graph was linear over concentration of 1.0 × 10^-7 - 5.0 × 10^-5 M with a detection limit of 6 × 10^-8 M at pH 5.4.

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A comparison was made of different digestion methods for the total decomposition of siliceous and organically environmental samples prior to their analysis by inductively coupled plasma optical emission spectrometry (ICP-OES). In the present study, three different digestion methods, including microwave-assisted, hot plate heating and pressurized digestion (pressure bomb), were employed for the determination of nine heavy metals, i.e. Ag, Cd, Cr, Cu, Fe, Mn, Ni, Pb and Zn in sediment, soil, sludge and oil. The investigation of different combinations of acids through their analytical performance demonstrated that HCl plays a vital role in the determination of silver. The combination of HNO₃ and HCl possesses more reactive ability in oxidizing organic matter. The recoveries of all elements of interest in sediment (NIST 2704) obtained by different digestion methods were found to be 86% to 113%, while microwave assisted digestion with various combinations of HNO₃-HCl-HF and HNO₃-HClO₄-HF was considered to be a viable alternative to the conventional digestion systems because of its more intensive reaction conditions. The analytical results of four certified reference materials with different matrices, including sediment (GBW 07305), soil (GBW 07411), sludge (BCR R-143) and oil (NIST 1085a), by the microwave-assisted acid digestion method indicated that the recoveries of all elements of interest were more than 85% and the throughput of applied analytical method could be elevated significantly.

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A unified ion chromatographic (IC) system was developed for the determination of acidity or alkalinity. Separation column used was a reversed-phase ODS packed column, which had been modified by saturating it with lithium dodecylsulfate. A slightly acidified LiCl (50 mM LiCl and 0.05 mM H₂SO₄) aqueous solution was used as the eluent. By conditioning the separation column in this way, both H⁺ and Li⁺ ions became bound to the stationary phase. Dodecylsulfate groups with Li⁺ counterions acted as cation-exchange sites for the separation of hydrogen ions (free acidity determination). The remaining dodecylsulfate groups, with H⁺ counterions acted as a titrant, which reacted with basic species (total alkalinity determination). The acidity or alkalinity of each sample was measured according to the change in conductance from the eluent baseline level. A positive peak was observed from those samples with a free acidity greater than their total alkalinity, due to the separation/elution of free H⁺ ions. A negative peak was observed from those samples with a free acidity less than their total alkalinity. This was due to an equivalent amount of eluent H⁺ ions being re-supplied to the stationary phase while the “solid titrant” consumed by the acid-base reaction was regenerated. The retention time for the peak corresponding to the acidity or alkalinity was governed by the retention time for H⁺ ions in this IC system. Samples with a free acidity greater than 2.25 μM (tested by determination of H⁺ ions in pure water in equilibrium with atmospheric CO₂) could be analyzed by this method. A very similar detection level was obtained for alkalinity (tested by analyzing standard aqueous NaHCO₃ solutions). Aqueous solutions of some strong-acid/strong-base inorganic salts were found to be slightly alkaline. This was measured as a percentage, relative to an NaHCO₃ solution at the same concentration. Solutions of NaClO₄, Na₂SO₄, NaI, NaNO₃, and NaCl, gave comparative alkalinity values of 8.75%, 1.83%, 0.42%, 0.35%, and 0.33%, respectively.

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The liquid ionization (LPI) mass spectra of the triorganotin carboxylates were described and compared with those obtained by other methods such as EI, FAB and ESI, in which [M + H]⁺ were not observed or the spectra were complicated. The liquid ionization mass spectra of triorganotin carboxylates varied with solvents and sample concentrations. For instance, the fragment ions [M + (C₄H₉)₃Sn]⁺ of dimeric ions were observed with chloroform used as a solvent, while the [M + H]⁺ were observed as the base peak using ethylene dichloride. Spectra useful for the differentiation of isomers [C₈H₇O₃Sn(C₄H₉)₃] were obtained by the formation of characteristic adduct ions, such as [M + EA + H]⁺ and [M + 2EA + H]⁺, with a reagent like 2-aminoethanol. Collision-induced dissociation (CID) spectra observed by ESI and LPI mass spectrometry were similar and provided less information than adduct ions did.

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The effects of various salts and HClO₄ on the configuration change of cobalt(II)-halide complexes in CHCl₃/CTAC or CTAB/H₂O reverse micelle systems were examined at 25°C by means of spectrophotometry, where CTAC and CTAB represent cetyltrimethylammonium chloride and bromide, respectively. The formation of the [CoCl₄]^2- or [CoBr₄]^2- species of the tetrahedral configuration from [Co(H₂O)₆]²⁺ of the octahedral configuration in the reverse micelles was greatly promoted not only by a decrease in the W value (W = [H₂O]/[surfactant]), but also, at a constant W value (e.g., W = 2.0), by the addition of relatively low concentrations of salts or the acid (e.g., 4.0 mol dm^-3 in the aqueous phase or 4.0 × 10^-2 mol dm^-3 in the whole reverse micelle system). The effects of perchlorate salts increased as Na⁺ ≤ Li⁺ ∼ H⁺ < Sr²⁺ < Ca²⁺ < Mg²⁺. Non-metallic salts, various tetraalkylammonium (R₄N⁺) salts at lower concentrations, gave minor effects. The enhanced effects of metal salts on the configuration change of the cobalt(II)-halide complexes were interpreted by a further distortion of the hydrogen-bonded structure of the water in a “water pool” in the presence of salts of even relatively low concentrations. A conformation change with increasing temperature was also attributed to a further distortion of the water structure. An almost completed formation of [CoBr₄]^2- as well as [CoCl₄]^2- was attained in the reverse micelles at a low W value of 0.69 containing LiClO₄ or HClO₄. A partial transfer of the [CoX₄]^2- species from a “water pool” into the CHCl₃ phase by the addition of the metal salts may be suspected. An examination of cobalt(II)-bromide complexes in dichloromethane/CTAB/H₂O at W = 1.3 - 5.55 justified all the arguments concerning the chloroform systems. The Raman spectra of D₂O containing concentrated LiBr and LiClO₄ have supplied conclusive evidence that the hydrogen-bonded structure of the bulk water is completely distorted by extremely concentrated salts.

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The determination of trace amounts of boron in steel by reversed-phase high-performance liquid chromatography (HPLC) is described. As a derivatizing reagent for the HPLC determination of boron, 8-hydroxy-1-(salicylideneamino)-3,6-naphtalenedisulfonic acid (azomethine-H) was used with a spectrophotometric detection. A peak of boron-azomethine-H chelate was resolved from other peaks using an acetonitrile-water (29 + 71 m/m) eluent containing 8 × 10^-3 mol kg^-1 tetrabutylammonium bromide and 5 × 10^-3 mol kg^-1 acetate buffer (pH 5.0). The lower determination limit (10σ) of boron was 3.3 × 10^-8 mol dm^-3 for a solution injected into HPLC, which is translated to 0.09 μgB/g when 0.1 g of a steel sample was subjected to the analysis. The analytical results of certified steel samples were in good agreement with the guaranteed values. The addition of ethylenediamine-N,N,N′,N′-tetraacetate as a masking agent for the iron(III) matrix with the optimized eluent enables one to achieve the direct determination of trace amounts of boron in such steel sample solutions without any tedious matrix removal or preconcentration.

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An iron(III) complex of thiacalix[4]arenetetrasulfonate on a modified anion-exchanger (Fe³⁺-TCAS_A-500) has shown high peroxidase-like activity at pH 5 - 6 for the reaction of quinoid-dye formation between 3-methyl-2-benzothiazolinone hydrazone and N-(3-sulfopropyl)aniline in the presence of hydrogen peroxide. Utilizing the peroxidase-like activity of Fe³⁺-TCAS_A-500 for this reaction, a method using Fe³⁺-TCAS_A-500 was applied for the spectrophotometric determination of hydrogen peroxide. The calibration curve by the method using Fe³⁺-TCAS_A-500 was linear over the range from 1 to 10 μg of hydrogen peroxide in a 1 ml sample solution. The apparent molar absorptivity for hydrogen peroxide was 2.4 × 10⁴ l mol^-1 cm^-1, which was about 80% of that by peroxidase under the same conditions. This determination method of hydrogen peroxide using Fe³⁺-TCAS_A-500 was applied for the determination of glucose in diluted normal and abnormal control serum I and II.

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A very simple, easy and sensitive spectrophotometric manual determination method of phosphorus for the PO₄^3- ion, based on the formation of the reduced 12-molybdophosphate complex, was developed. The effect of the kind of water-miscible organic solvent and the concentration of organic solvent, ascorbic acid and HCl on the formation of the complex was investigated. The optimum determination condition was confirmed based on these results. In an aqueous-CH₃CN solution, a P-PO₄^3- of 0.01 - 20 mg l^-1 could thus be determined. It was noted that the determination range of this study was wider than that of the phosphoantimonylmolybdenum blue method (0.032 - 1 mg l^-1). The effect of foreign ions on the absorbance was examined. The P-PO₄^3- in river water and seawater sampled in Kochi was determined by this method. The results were also compared with those of the phosphoantimonylmolybdenum blue method and capillary electrophoresis with an indirect detection method using K₂CrO₄.

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A catalytic spectrophotometric method for the determination of trace amounts of nitrite is proposed. In acidic solution, chlorpromazine (CP) is oxidized by nitric acid to form a red compound, which is further oxidized to a colorless compound. The reaction is accelerated by trace amounts of nitrite and can be followed by measuring the absorbance at 525 nm: nitrite ion is regenerated and multiplied by nitric acid. The absorbance of the reaction increased with an increase in the reaction time, reached a maximum and decreased rapidly. Since the time required for the absorbance to reach the maximum decreased with increasing nitrite concentration, this value was used as the measured parameter for the nitrite determination. Under the optimum experimental conditions (2.3 M nitric acid, 1.2 × 10^-5 M CP, 40°C), nitrite can be determined in the range 0 - 100 μg l^-1. The relative standard deviations (n = 6) are 4.7 and 1.8% for 40 and 100 μg l^-1 nitrite, respectively. The detection limit of this method (3σ) is 1.2 μg l^-1. This method was successfully applied to a determination of nitrite in natural water samples.

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High resolution spectral data of 100 ppmV (10^-6 per volume) concentrations of the trace gases bromo methane (BM, CH₃Br), and methyl bromide (DME, (CH₃)₂O), buffered in synthetic air (80% N₂, 20% O₂) at atmospheric pressure and room temperature are reported. The spectra are recorded with a continuously tunable 10-bar CO₂ laser based photoacoustic (PA) spectrometer. The tuning range covers 76 cm^-1 between 9.2 μm (1087 cm^-1) and 10.7 μm (935 cm^-1) at a constant narrow line-width of 0.018 cm^-1 (540 MHz). The non-resonant PA measuring cell employs an in-line 10-microphone array. The estimated detection limits for BM and DME are approximately 2 ppmV for a signal-to-noise ratio (SNR) of 3. This corresponds to a calculated detection limit of∼76 ppbV for ethylene.

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