Indian Journal of Chemical Technology

Research articles
Quantitative methods for the assay of acyclovir in non-aqueous medium	759
IPC Code: C07 D 473/18
K Basavaiah & H C Prameela

Determination of serum and urinary urate with reusable uricase strip	764
IPC Code: C03 C 17/28
Sushma, Rekha, Vijay Kumar, Suman & C S Pundir

Sensitive determination of atenolol in tablets using chloramines-T and two dyes	769
IPC Code: G01 J 3/00, G01 N 31/16
K Basavaiah, U Chandrashekar & P Nagegowda

Technique to determine anti-scalants efficiency for industrial cooling water system	777
IPC Code: C02 F 5/08
R S Chaudhary & Harish Kumar

Turbidity studies on mixed surfactant systems in hard water: A new method for estimation of water hardness	783
IPC Code: C11 D 1/02
Naorem Homendra & Ch. Indira Devi

Flotation-separation of nickel from aqueous media using some hydrazone derivatives as organic collectors and oleic acid as surfactant	787
IPC Code: B03 D 1/004, 101:02
S E Ghazy, H A Mostafa, S A El-Farra & A S Fouda

Separation of light hydrocarbons by gas chromatography using serpentine as stationary phase	793
IPC Code: B01 D 15/08
B N Singh & B Maiti

Electrochemical detection of phenol in aqueous solutions	797
IPC Code: G01 R 1/00
J Mathiyarasu, James Joseph, K L N Phani & V Yegnaraman

Optimising ANN architecture for shell and tube heat exchanger modelling	804
IPC Code: C09 K 5/00
S L Pandharipande, M A Siddiqui, A Dubey & S A Mandavgane

Dipole moment studies of H-bonded complexes of phenols and substituted phenols with benzaldehyde in tetrachloromethane	811
IPC Code: C07 C 39/04
U S Mahapatra, G S Roy & L Maharana
Enzymatic saccharification of cellulosic waste by cellulase system of Cellulomonas uda immobilized on tri(4-formyl phenoxy) cyanurate	816
IPC Code: C08 B 1/00
C N Khobragade, K Sureshkumar, Prita S Borkar & A D Sagar

Modelling of packed column using artificial neural networks	820
IPC Code: B01 D 3/26
S L Pandharipande & S A Mandavgane

Kinetic and equilibrium characterization of phenols adsorption onto a novel activated carbon in water treatment	825
IPC Code: B01 D 15/02
Sumol Varghese, V P Vinod & T S Anirudhan

Studies on (non) energetic compounds, Part 44: Kinetics of thermolysis of dichloroanilinium chloride salts	834
IPC Code: G01 N 25/00, G01 J 3/28, C07 C 211/46
Gurdip Singh & Jaya Srivastava

Synthesis and characterization of CoAlPO₄-5 and CoAlPO₄-31 molecular sieves	843
IPC Code: C01 B 37/06
N Venkatathri & G P Aswin Kumar

Phase transfer reaction of potassium superoxide with benzylic methyl and methylene compounds in aprotic medium	848
IPC Code: C07 B 33/10
Ajay Kumar Shukla & Krishna Nand Singh

Crosslinked polyethylene	853
IPC Code: C08 F 2/00
S M Tamboli, S T Mhaske & D D Kale

Notes
Correction factor to determine total hydrogen+deuterium concentration obtained by inert gas fusion-thermal conductivity detection (IGF-TCD) technique	865
IPC Code: G01 N 25/18, B01 D 59/00
K L Ramakumar, Y Sesha Sayi, P S Shankaran, G C Chhapru, C S Yadav & V Venugopal

Factal analysis of the contribution of aerosols from two different major sources	869
IPC Code: C10 B 57/00
Mrinal K Ghose & S K Banerjee

Educator
Bleaching-From antiquity to chlorine	876
Jaime Wisniak

Chem-Tech Scan	889

List of Referees	893

Annual Author Index	895

Annual Keywords Index	898

Quantitative methods for the assay of acyclovir in non‑aqueous medium

Three simple methods using visual titrimetric, potentiometric and spectrophotometric techniques are described for the determination of acyclovir in pure form and in pharmaceutical formulations. The methods are based on the neutralisation reaction involving the primary amino group of the drug and acetous perchloric acid in acetic acid medium. In titrimetric methods, the titration is completed with visual or potentiometric end-point detection, crystal violet being used as the indicator in visual titration. In spectrophotometry, the drug is treated with a fixed amount of perchloric acid-crystal violet mixture and absorbance of the resultant violet colour is measured at 570 nm and is related to drug concentration. Both titrimetric methods are applicable over 2-20 mg range of drug and the titration reaction follows a 1:1 stoichiometry. In spectrophotometry, Beer’s law is obeyed over the concentration range 5-55 mg mL^-1 with an apparent molar absorptivity and Sandell sensitivity of 1.78 × 10⁴ L mol^-1 cm^-1 and 12.68 ng cm^-2, respectively. The limits of detection and quantification are calculated to be 1.696 and 5.654 mg mL^-1, respectively. The methods were successfully applied to the determination of acyclovir in tablets. The validity of the methods was further ascertained by parallel determination by a reference method and by recovery studies via standard-addition technique.

Keywords: Acyclovir determination, potentiometry, titrimetry, spectrophotometry, antiviral drug

Determination of serum and urinary urate with reusable uricase strip

Commercial uricase has been immobilized covalently onto alkylamine glass beads affixed on a plastic strip with a conjugation yield of 87mg/g and 11.5% retention of initial activity of free enzyme. Maximum activity of immobilized enzyme was attained at pH 8.8, when incubated at 40°C for 20 min. K_m for uric acid and V_max of immobilized enzyme were 0.15mM and 0.68mmoles H₂O₂/min respectively. A method for uric acid determination in serum and urine was developed using the strip bound enzyme. The method is based on the measurement of H₂O₂ generated from uric acid by using a colour reaction consisting of 4-aminophenazone, p-hydroxybenzoic acid and horseradish peroxidase as chromogenic system. The minimum detection limit of the method was 1.68mg/dl and recovery of added uric acid in urine was 90% .The coefficient of variation (CV) were <5 and <2% for within batch and between batch respectively. The immobilized enzyme lost 50% of its initial activity after its regular uses for over 3 weeks, when stored in 0.05M glycine NaOH buffer, pH 8.8 at 4°C.

Sensitive determination of atenolol in tablets using chloramine-T and two dyes

Three methods, one titrimetric and two spectrophotometric, using chloramine-T (CAT) and two dyes, metanil yellow and indigocarmine have been developed for the determination of atenolol (ATN) in bulk drug and in tablets. The titrimetric method (Method A) involves the oxidation of the drug by a measured excess of CAT in acid medium followed by the determination of the residual oxidant by iodometric back titration. In spectrophotometric methods, ATN is oxidised by a known excess of CAT in acid medium followed by the determination of unreacted oxidant by reacting with a fixed amount of either metanil yellow (Method B) or indigo carmine (Method C) and measuring the increase in absorbance at 530 or 610 nm. Titrimetry is applicable in 3-20 mg range whereas in spectrophotometry, Beer's law is obeyed over the concentration ranges, 1-12 μg mL^-1 (Method B) and 2.5 - 20.0 μg mL^-1 (Method C). Molar absorptivity values as calculated from Beer's law data are found to be 1.19×10⁴ L mol^-1cm^-1(Method B) and 6.65×10³ L mol ^-1cm^-1 (Method C) and the corresponding Sandell sensitivity values are 0.022 and 0.040 μg cm^-2. The choice of experimental conditions, which provide the maximum accuracy, precision and sensitivity, is discussed. The common excipients and additives found in tablet preparations did not interfere. The proposed methods were successfully applied to the determination of the drug in tablets. Recoveries ranged from 96.43 to 103.74 %. The utility and accuracy of the methods were further established by parallel determination by the official Indian Pharmacopoeial method and by recovery studies.

Keywords: Atenolol determination, indigo carmine, metanil yellow, titrimetry, spectrophotometry

Technique to determine anti-scalants efficiency for industrial cooling water system

Techniques, presently used for the measurement of the efficiency of anti-scalants for industrial cooling water do not provide reproducible results, are time consuming and difficult to perform. It is also not possible using these techniques to find the efficiency of anti-scalants in actual cooling water. A problem is faced by industries in finding the optimum concentration of the anti-scalants in a cooling water of particular composition as the efficiency of the anti-scalants depends on the quality of cooling water. Consequently, the dose of the anti-scalant required in the cooling water system, is not possible to ascertain. A technique based on theoretical considerations has been reported herein, which not only provides reproducible results but is also easy and quick to perform using actual cooling water.

Turbidity studies on mixed surfactant systems in hard water: A new method for estimation of water hardness

Water hardness tolerance of anionic surfactants, viz. sodium dodecyl sulphate (SDS) and linear alkyl benzene sulphonate – sodium salt (LABS) has been investigated with the help of a digital Nephlo-turbidity meter. Effect of incorporation of small amount of a nonionic surfactant, Triton X-100 (TX-100), on the water hardness tolerance i.e. the lime soap dispersing ability (LSDA), of LABS has also been studied. It was observed that LABS generally exhibited superior LSDA than SDS and that incorporation of a small amount of TX-100 led to significant improvement of the LSDA of the anionic surfactants studied. In fact, incorporation of TX-100 beyond 10% concentration level, no turbidity was observed up to 300ppm hardness of water. The small angle X-ray scattering profile of the systems revealed that, at the maximum turbidity point, the anionic micelles were destroyed by the hardness causing ions. It was also observed that at certain range of the surfactant concentration in the pre-micellar region, the turbidity was found to vary linearly with the degree of hardness (ppm) of water. This linear relationship between the turbidity and the hardness can be effectively used for the estimation of the hardness causing ion with good reproducibility.

Flotation-separation of nickel from aqueous media using some hydrazone derivatives as organic collectors and oleic acid as surfactant

A simple and rapid procedure was developed for the quantitative flotation of nickel(II) from aqueous solutions. Hydrazone derivatives such as: 4-acetylpyridine-[N-(3-hydroxy-2-naphthoyl)]hydrazone (H₂APHNH), thiophene-2-carbox-aldehyde-[N-(3-hydroxy-2-naphthoyl)]hydrazone (H₂THNH), salicylaldehyde-[N-(3-hydroxy-2-naphthoyl)]-hydrazone (H₂SHNH), p-anisaldehyde-[N-(3-hydroxy-2-naphthoyl)]hydrazone (H₂-p-AHNH) and ethylacetoacetate-[N-(3-hydroxy-2-naphthoyl)]hydrazone (H₂EHNH) have been used as organic collectors and oleic acid as surfactant. The different parameters, affecting the flotation process, namely, ligand and surfactant concentrations, foreign ions (which are normally present in fresh and saline waters), pH and temperature are examined. Nearly 100% of nickel ions are floated at a metal:ligand ratio of 1:2, pH ~ 7 and at a temperature ~ 25ºC. The procedure is successfully applied to recover Ni(II) from some water samples. The flotation mechanism is suggested.

Keywords: Flotation, hydrazone derivatives, nickel, surfactant, oleic acid, organic collectors

Separation of light hydrocarbons by gas chromatography using serpentine as stationary phase

The application of serpentine ore (brownish colour) as a stationary phase for the separation of hydrocarbons by gas-solid chromatography has been tested. Separation of methane, ethane, propane, n-butane, iso-butane and acetylene has been accomplished at room temperature (25°C). The separated components were detected with a flame ionization detector. The peaks of isobutane and n-butane were rather broad, unsymmetrical and poorly resolved at room temperature but the resolution improved and the peaks were sharper and symmetrical when the separation was carried out at a higher temperature (50°C). The variation of retention time and peak shape have been studied as a function of flow rate and temperature of separation. Light hydrocarbons (C1-C4) could be separated at 25°C on a stainless steel column (2.8 M long and 2.3 mm i.d.) packed with 60-100 mesh particles using nitrogen as carrier gas flowing at 8 mL/min. The separation of hydrocarbons on serpentine column has been successfully applied to the determination of dissolved hydrocarbon gases in transformer oil. The results of the analysis agree well with those obtained using silica gel column.

Electrochemical detection of phenol in aqueous solutions

Phenol oxidation in aqueous solutions was carried out in a pH range of 7-12 using cyclic votlammetry (CV) and differential pulse voltammetry (DPV) studies on a glassy carbon electrode. Peak potentials are found to be distinct for each pH value. A linear relationship is observed between the peak current and the concentration ranging from micro- to milli-molar levels. The peak current is found to be proportional to the concentration of phenol up to 5 mM that allows determination of unknown concentrations of phenol down to 5 mM. Using DPV technique, the phenol concentration is detected up to a concentration of 0.5 mM.

Keywords: Phenol, electrochemical oxidation, electroanalysis, cyclic voltammetry, differential pulse voltammetry

Optimising ANN architecture for shell and tube heat exchanger modelling

Heat exchangers have a special place in chemical process industries. The shell and tube heat exchanger is commonly used for heating or cooling of process fluids. The various parameters to be taken into account for developing a model are inlet and outlet temperatures of shell and tube side fluids and their flow rates. Artificial Neural Networks (ANN) are effective in modeling of non-linear multi variable relationships and also referred to as the black box models. In the present work, various ANN models have been developed with single, two and three hidden layers for estimation of exit temperature of both the fluids as a function of inlet temperature conditions and also flow rates. The data used for training of ANN is generated on a small shell and tube heat exchanger, fabricated for this purpose. The ANN models thus developed are validated for test data that was not used for training of these models. The comparisons between models have been carried out. It is observed that ANN model with three hidden layers (15-15-15 neurons) has good level of accuracy (95-98%) for predicted values of training and test data set.

Dipole moment studies of H-bonded complexes of phenols and substituted phenols with benzaldehyde in tetrachloromethane

The dipole moment of 1:1 hydrogen bonded complexes of phenols and substituted phenols with benzaldehyde were determined from dielectric measurements at a temperature of 308.16 K. The dipole moment of the complex (m_ab), molar polarisation (P_ab), interaction dipole moment (Dm) for all the ternary systems were calculated for most favourable consideration predicted thermodynamically. The results indicate that complexation is predominantly due to polarization as well as electrostatic interaction.

Keywords: H-Bonded complex, relative permittivity, dipolemoment, molar polarization

Enzymatic saccharification of cellulosic waste by cellulase system of Cellulomonas uda immobilized on tri(4-formyl phenoxy) cyanurate

Cellulose is one of the most abundant non-degradable organic compound on earth. Near about half of the municipal and agricultural solid wastes contain cellulose or their derivatives. Saccharification or enzymatic hydrolysis of cellulosic wastes liberates glucose. In the present work, cellulase from Cellulomonas uda was extracted, partially purified by dialysis and immobilized on an organic support namely tri(4-formyl phenoxy) cyanurate. Percentage saccharification of seven different cellulosic waste materials was studied using native and immobilized cellulase systems. Maximum saccharification for both native and immobilized cellulase was observed for sawmill dust or wood dust (4.9 and 2.4% respectively) as compared to other cellulosic waste substrates.

Keywords: Cellulase, immobilization, tri(4-formyl phenoxy) cyanurate, Cellulomonas uda, saccharification

Modelling of packed column using artificial neural networks

Packed column is an established gas liquid contacting device with many industrial applications. Estimation of liquid hold up and pressure drop as a function of gas and liquid flow rates for single as well as two phase flow are of significance from operational as well as design point of view. Various empirical models have been suggested for the same. Artificial Neural Networks (ANN) are gaining importance in modelling of multivariable, non-linear relationship with high accuracy and even in presence of inadequate data. In present work multi layer perceptron (MLP) ANN with GDR based learning have been developed for estimation of liquid hold up and pressure drop for packed column. The ANN models thus developed are observed to be of good accuracy level, both for training and test data set.

Keywords: Artificial neural networks, ANN, packed column, Ergun’s equation

Kinetic and equilibrium characterization of phenols adsorption onto a novel activated carbon in water treatment

The present study envisages the use of an aquatic plant material, water hyacinth to prepare a novel activated carbon for the removal of phenol, p-chlorophenol and p-nitrophenol from simulated wastewaters by adsorption process. The effect of pH, contact time, initial concentration of adsorbate and temperature on removal process was investigated. The maximum removal of phenols from their aqueous solutions occurred at pH 6.0. The applicability of the intraparticular mass transfer diffusion kinetic model in each case of phenol, p-chlorophenol and p-nitrophenol was studied separately at different concentrations and temperatures. Kinetic parameters as a function of concentration and temperature were evaluated to predict the nature of adsorption. The adsorption process was found to be exothermic and the adsorption of phenols was found to follow the order: p-nitrophenol > p-chlorophenol > phenol. Equilibrium adsorption data were correlated with Langmuir, Freundlich and Redlich–Peterson adsorption isotherm models. Freundlich isotherm model was found applicable to represent the adsorption data for all three adsorbates. The maximum adsorption capacity of activated carbon was found to be 1.20, 1.28 and 1.35 mmol/g for phenol, p-chlorophenol and p-nitrophenol respectively. Adsorbed phenols on activated carbon were recovered (91.5– 96.3%) using 0.05 M sodium hydroxide. The petroleum refinery industry wastewater sample was treated by activated carbon to demonstrate its efficiency in removing phenols from wastewaters.

Studies on (non) energetic compounds, Part 44: Kinetics of thermolysis of dichloroanilinium chloride salts

Five salts of dichloroanilinium chloride (DCACl) were prepared and characterised by elemental and spectral studies. Thermal decomposition of these salts was investigated by simultaneous TG-DTG-DTA and isothermal TG. Kinetic parameters have been evaluated from the model fitting and model free isoconversional methods. It has been observed that simultaneous sublimation/decomposition processes are involved during the thermal decomposition of DCACl.

Keywords: TG, thermolysis, dichloroanilinium chloride, DTA, isoconversional method

Synthesis and characterization of CoAlPO₄-5 and CoAlPO₄-31 molecular sieves

Cobalt substituted AlPO₄-5 and AlPO₄-31 molecular sieves have been synthesized hydro thermally in the presence of Co(II) species and triethyl amine and di-n-propylamine as templating molecule. Various techniques of characterization show that Co²⁺ cations substitute Al³⁺ ions in the framework. Crystals of CoAlPO₄-5 and CoAlPO₄-31 are relatively large, and their morphology changes with the cobalt content. Samples are thermally stable and can be calcined in air without significant loss of the crystallinity. Upon calcination, part of the Co(II) species present in as-synthesized samples are converted into Co(III) species. These Co(III) species can be readily reduced in H₂ at 400^oC. CoAlPO₄-31 has been found to be an active catalyst compared to CoAlPO₄-5 in the ethyl benzene oxidation using tertiary butyl hydro peroxide.

Keywords: Cobalt, CoAlPO₄-5, CoAlPO₄-31, aluminophosphate, molecular sieves

Phase transfer reaction of potassium superoxide with benzylic methyl and methylene compounds in aprotic medium

Tetraethylammonium superoxide, generated in situ by the phase transfer reaction of potassium superoxide and tetraethylammonium bromide, brings about an easy oxidation of a variety of benzylic methyl and methylene compounds under significantly mild reaction conditions, at room temperature.

Keywords: Phase transfer reaction, tetraethylammonium superoxide, oxidation, benzylic methyl

Crosslinked polyethylene

Properties of polyolefins can be modified by crosslinking process. Different methods of crosslinking and effect of process parameters, selection of crosslinking agents and applications are briefly discussed.

Correction factor to determine total hydrogen+deuterium concentration obtained by inert gas fusion-thermal conductivity detection (IGF-TCD) technique

K L Ramakumar*, Y Sesha Sayi, P S Shankaran, G C Chhapru, C S Yadav & V Venugopal

The limitation of commercially available dedicated equipment based on Inert Gas Fusion-Thermal Conductivity Detection (IGF-TCD) for the determination of hydrogen+deuterium is described. For a given molar concentration, deuterium is underestimated vis a vis hydrogen because of lower thermal conductivity and not considering its molecular weight in calculations. An empirical correction factor based on the differences between the thermal conductivities of hydrogen, deuterium and the carrier gas argon, and the mole fraction of deuterium in the sample has been derived to correct the observed hydrogen+deuterium concentration. The corrected results obtained by IGF-TCD technique have been validated by determining hydrogen and deuterium contents in a few samples using an independent method based on hot vacuum extraction-quadrupole mass spectrometry (HVE-QMS). Knowledge of mole fraction of deuterium (X_D) is necessary to effect the correction. The correction becomes insignificant at low X_D values (X_D < 0.2) as the precision in the IGF measurements is comparable with the extent of correction.

Factal analysis of the contribution of aerosols from two different major sources

Indian coals have high percentage of ash content. Bigger sizes are crushed into smaller ones and fed for washing. The main air pollution problem due to washery project is the dust, which is more acute than any other coal processing industry. It is, therefore, essential to pay attention to assess the impact on air environment due to washery activities. Air pollution problem in the washery in question was due to the superimposition of pollutants from the washery and a thermal power plant (TPP). To evaluate the actual contribution of air pollutants by washery and thermal power plant factal analysis techniques were adopted. Approach to the selection of air monitoring stations for factal analysis and methods adopted for air quality survey have been described. Three season data were generated and the status of air pollution has been evaluated. The data were critically analysed on the basis of changes in wind directions at different seasons, the proportion of ash and volatile matter in washery dust and TPP fly ash, and microscopic examination of the SPM by identification of black dust from the coal washery and whitish gray dust from power plant. From the data results the actual contribution of pollutants by the washery and thermal power plant were evaluated. The results obtained by different techniques were found to be comparable.

Bleaching¾From antiquity to chlorine

The art of bleaching developed very slowly, as a labour and land intensive industry, between ancient times and the end of the eighteenth century. The sequels of the chemical revolution initiated by the Leblanc soda process brought into the market vast amounts of chlorine and caustic soda that changed completely the chemical industry in general, and the bleaching process in particular. Chemical bleaching reduced the process time from months to days, released large areas of land for agricultural purposes, allowed the technique to be used everywhere, and made white clothes available to all the social strata. Bleaching with chlorine and its derivatives is probably the most important development of the textile industry up to the introduction of synthetic dyes and synthetic fibres

ISSN:0971-457X		CODEN:ICHTEU 11(6) 751-902
VOLUME 11	NUMBER 6	NOVEMBER 2004