Indian Journal of Chemistry

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Sect. A: Inorganic, Bio-inorganic, Physical, Theoretical & Analytical

 

VOLUME 45A

NUMBER 11

November 2006

CONTENTS

 

2369

 

Nucleophilicity/electrophilicity excess in analyzing molecular electronics

 

 

 

 

D R Roy, V Subramanian & P K Chattaraj*

 

 

 

Intramolecular electron transfer capability of all metal aromatic and anti-aromatic aluminum cluster compounds is reported in terms of density functional theory based global and local reactivity descriptors. Associated intermolecular reactivity pattern among the related molecules of various categories is also studied. A new local reactivity descriptor, nucleo(electro)-philicity excess is designed for this purpose.

 

 

 

2381

 

Zinc complexes for hydrolytic cleavage of DNA

 

 

 

 

 

 

 

 

 

Pulimamidi Rabindra Reddy, Sepuru Krishna Mohan,Rallabandi Madhusudan Raju & Pappula Ettaiah

 

 

 

Artificial metallonucleases [ZnII(CysGly)(HisAla)]  and [ZnII(CysGly)(HisLeu)] have been prepared, characterized and their DNA cleavage abilities have been probed.

 

 

 

2392

 

Synthesis, spectroscopy, thermal and X-structure studies of a seven coordinated hydrated Ca(II)-para-nitrobenzoate complex showing mono and bidentate carboxylate ligation

 

 

 

 

 

 

 

 

 

 

Bikshandarkoil R Srinivasan*, Jyoti V Sawant & Pallepogu Raghavaiah

 

 

 

The reaction of CaCO3 with 4-nitrobenzoic acid
(4-nbaH) results in the formation of a seven coordinated Ca(II) complex [Ca(H2O)4(4-nba)2]. The structure exhibits both monodentate and bidentate carboxylate ligation of the 4-nitrobenzoate ligand.

 

 

 

 

2400

 

Activation energies of hopping of vanadium 3d1 small polaron in 0.7V2O5-(0.3-x)P2O5-x(As2O3/ Sb2O3) (x=0, 0.05) glasses by EPR spectroscopy and DC electrical conductivity measurements

 

 

 

 

 

B B Das* & D Mohanty

 

 

 

Three glasses in the 0.7V2O5-(0.3-x)P2O5-x(As2O3/ Sb2O3) (x= 0, 0.05) system, G1 (x=0), G2 (x=0.05: As2O3) and G3 (x=0.05: Sb2O3) have been prepared by melting the appropriate amounts of the batches in silica crucibles in the temperature ~1120 K and quenching in air. The glassy phase has been ascertained by powder X-ray diffraction of the samples which shows a broad peak around 25° in 2θ vanishing at higher diffraction angles typical of glassy phase.

 

 

 

2406


Synthesis, characterisation and substitution reaction of trans-(diaqua)(N,N¢-ethylene-bis-salicyl-amide)chromium(III) ion

 

 

 

 

 

 

 

 

 

 

 

 

S C Dash, G S Brahma, R Das, N N Das* &P Mohanty*

 

 

 

Trans-[Cr(Salm)(OH2)2]NO3 has been synthesized and characterized by various physicochemical methods. The kinetics of substitution of [Cr(Salm)(OH2)2]+ with different nucleophiles, viz., thiocyanate, azide, imidazole, pyridine, pyridine-2-caroxylic acid and pyridine-3-caroxylic acid is also reported.

 

 

 

 

2412

 

Kinetics of oxidation of procaine hydrochloride by sodium N-chlorobenzenesulfonamide in acid and alkaline media: A mechanistic approach

 

 

 

 

 

 

 

 

Puttaswamy* & J P Shubha

 

 

 

A kinetic study of oxidation of procaine hydrochloride (one of the potent local anaesthetics) by sodium N-chlorobenzene­sulfonamide has been carried out in HClO4 (30°C) and NaOH (20°C) media. The reaction is found to be faster in alkaline medium in comparison with acid medium. The conjugate free acid C6H5SO2NHCl of CAB is postulated as the reactive oxidizing species in both the media. The observed results have been explained by plausible mechanisms and the related rate laws have been deduced.

 

 

Notes

 

 

2418

 

Synthesis and characterization of cryptates of Y(III), La(III), Gd(III), Yb(III) with a N2O6 cryptand

 

 

 

 

 

Yong Huang, Wei Wang, Lan Yan &Rudong Yang*

 

 

 

 

 

 

 

2421

 

Complexes of the Schiff base derived from 4-amino-phenyl benzimidazole and 2,2'-dehydropyrollidene-N-aldehyde with Zn (II), Cd (II) and Hg (II) halides

 

 

 

 

S Rekha & K R Nagasundara*

 

 

 

A new Schiff base, dhpyr4apbi, has been synthesized from 4-aminophenyl benzimidazole and 2,2¢-dehydropyrolli-dene-N-aldehyde and its complexes with Zn(II), Cd(II) and Hg(II) halides have been prepared. Physicochemical properties of these metal complexes have been investigated. The complexes are non-electrolytes and are dimeric in nature with the empirical formula M2L2X4 (M = Zn, Cd, Hg; X = Cl, Br.). The minimum energy configuration has been obtained for these complexes using the molecular model Pro Plus.

 

 

 

2426

 

Synthesis, spectroscopic and structural features of diorganotin(IV) oximates derived from 9,10-phen-anthrenequinone monooxime

 

 

 

 

Mayur Sharma, Sarita Jangir, C K Ojha &
P Pardasani*

 

 

 

Reactions of monofunctional 9,10-phenanthrenequinone monooxime with dialkyl-/diaryl-tin dichloride in desired molar ratios in refluxing benzene affords corresponding dialkyl-/diaryl-tin(IV) oximates. On the basis of calculation of C-Sn-C bond angle from coupling constant, trigonal-bipyramidal and octahedral geometry are proposed for the chelates. Semiempirical studies have been carried out to understand the tautomeric and conformational behaviour of the ligand.

 

 

 

2431

 

Cu (II) catalysed oxidation of o-mercaptobenzoic acid by methylene blue in acidic medium: A kinetic study

 

 

 

 

 

 

R Gupta, R Chaturvedi & K K Mishra*

 

 

 

Kinetics of oxidation of o-mercaptobenzoic acid by methylene blue catalyzed by Cu(II) in presence of sulphuric acid and in aqueous ethanol medium (4% v/v) have been studied. Two moles of the substrate are oxidized by one mole of methylene blue forming the disulphide and the leuco dye as the end products. The order in methylene blue is 3/2 which increases to two at lower concentrations of Cu(II). The order in o-mercaptobenzoic acid is nearly zero. Activation parameters have been evaluated and a plausible reaction scheme, presuming the reaction between metal – TSA complex and MB dimer as the rate determining step, has been proposed.

 

 

 

2435

 

Kinetics of oxidation of thymine by t-butoxyl radical — Protection and repair by caffeic acid

 

 

 

 

Lingareddy Charitha & Mundra Adinarayana*

 

 

 

 

 

2441

 

Kinetics and mechanism of oxidation of secondary alcohols by benzyltriethylammonium chlorochromate

 

 

 

 

Ravdeep Kaur, Neelam Soni & Vinita Sharma*

 

 

 

Oxidation of several aliphatic secondary alcohols by benzyltriethylammonium chlorochromate in dimethyl-sulfoxide leads to the formation of the corresponding ketones.

 

       R2 CHOH  +   O2CrClO-bteN+   ¾® 

                              R2 C = O   +   H2O   +   OCrClO-bteN+

 

 

 

 

2446

 

Highly selective chloride poly(vinyl chloride) membrane electrode based on vanadium(IV) oxide acetylacetonate

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Rakesh Kumar Mahajan* & Pallavi Sood

 

 

 

The response characteristics of a new solvent-polymeric membrane electrode with unique selectivity and detection limit towards chloride anion is reported here. The electrode is prepared by incorporating vanadium(IV) oxide acetylacetonate into a plasticized PVC-membrane and  exhibits high selectivity for chloride anion over other anions, including lipophilic inorganic anions like nitrate and perchlorate. The electrode has a linear dynamic range 2.5´10-5-1.0´10-1 M with a Nernstian slope –55.0±2 mV per decade and a low detection limit 4.27´10-6 M. The potentiometric response has been found to be independent of pH of the solution in the pH range 3.5-9.0. The electrode can be used for at least 9 months without any considerable divergence in its potential. It can be used as an indicator electrode in the potentiometric titration of silver ions.

 

 

 

Authors for correspondence are indicated by (*)


Indian Journal of Chemistry

Vol. 45A, November 2006, pp. 2369-2380

 

Nucleophilicity/electrophilicity excess in analyzing molecular electronics

D R Roy, V Subramanian* & P K Chattaraj *

Received 9 June 2006; revised 7 September 2006

Intramolecular electron transfer capability of all metal aromatic and anti-aromatic aluminum cluster compounds is reported here in terms of density functional theory based global and local reactivity descriptors. Associated intermolecular reactivity pattern among the related molecules of various categories is also studied. A new local reactivity descriptor, nucleo(electro)philicity excess is designed for this purpose. The findings will provide important inputs towards the fabrication of the material required for molecular electronics.

 

Indian Journal of Chemistry

Vol. 45A, November 2006, pp. 2381-2391

 

Zinc complexes for hydrolytic cleavage of DNA

Pulimamidi Rabindra Reddy*, Sepuru Krishna Mohan, Rallabandi Madhusudan Raju & Pappula Ettaiah

Received 7 March 2006; revised 9 September 2006

Artificial metallonucleases [ZnII(CysGly)(HisAla)] (1) and [ZnII(CysGly)(HisLeu)] (2) have been prepared, characterized and their DNA cleavage abilities probed. UV, viscosity and fluorescence investigations show that the 1:1:1 complexes bind to CT-DNA through an intercalation. Gel electrophoresis studies reveal that these complexes cleave the plasmid pBR 322 DNA (form I) through nicked (form II) to linear (form III) forms under physiological conditions (37°C, H2O, pH 7.5). DNA hydrolytic cleavage rate constants for complexes 1 and 2 at 37°C have been determined to be 0.55 h-1 and 0.49 h-1, respectively. Since redox-active metals can also account for the DNA cleavage, the cleavage by non-redox metal like zinc assumes importance.

IPC Code: Int. Cl.8 A61K31/555; C12N5/08; C12N15/87; C12Q1/68

 

Indian Journal of Chemistry

Vol 45A, November 2006, pp 2392-2399

 

Synthesis, spectroscopy, thermal and X-structure studies of a seven coordinated hydrated Ca(II)-para-nitrobenzoate complex showing mono and bidentate carboxylate ligation

Bikshandarkoil R Srinivasan*, Jyoti V Sawant & Pallepogu Raghavaiah

Received 21 August 2006; accepted 29 September 2006

The reaction of CaCO3 with 4-nitrobenzoic acid (4-nbaH) results in the formation of a seven coordinated Ca(II) complex [Ca(H2O)4(4-nba)2] 1, (4-nba being 4-nitrobenzoate). The compound has been characterized by elemental analysis, IR and UV-Vis spectra and its structure determined. The complex can be dehydrated to the corresponding anhydrous Ca(II)-bis-4-nitrobenzoate Ca(4-nba)2 2, and the anhydrous complex thus formed can be rehydrated as evidenced by IR spectra. The structure of 1 exhibits both monodentate and bidentate carboxylate ligation of the 4-nitrobenzoate ligand. The coordination by the O atom from four water molecules completes the heptacoordination around Ca(II). The free O atoms of the monodentate 4-nba and one of the coordinated O atom of the bidentate 4-nba in 1 are linked via H-bonding to one of the coordinated waters of a neighbouring Ca(II) resulting in the formation of psuedo dimers. The dimers thus formed are further linked with the aid of H-bonds, along a as well as b resulting in the formation of an intricate supramolecular network.

Indian Journal of Chemistry

Vol. 45A, November 2006, pp. 2400-2405

 

Activation energies of hopping of vanadium 3d1 small polaron in 0.7V2O5-(0.3-x)P2O5-x(As2O3/Sb2O3) (x=0, 0.05) glasses by EPR spectroscopy and DC electrical conductivity measurements

B B Das* & D Mohanty

Received 1 May 2006; revised 16 September 2006

The three glasses in the 0.7V2O5-(0.3-x)P2O5-x(As2O3/Sb2O3) (x= 0, 0.05) system, G1 (x=0), G2 (x=0.05: As2O3) and G3 (x=0.05: Sb2O3) have been prepared by melting the appropriate amounts of the batches in silica crucibles in the temperature ~1120 K and quenching in air. The glassy phase has been ascertained by powder X-ray diffraction of the samples which shows a broad peak around 25° in 2θ vanishing at higher diffraction angles typical of glassy phase. EPR studies of the glasses in the range 10-473 K show that the lineshapes are isotropic in nature. The observed values of the g-matrices are similar in all the glasses in the range 10-473 K which shows that the octahedra containing the paramagnetic sites are similar in all the glasses. The V4+(3d1) small polaron activation energies of hopping are lower in the case of G2 (1.16´10-4 eV) and G3 (1.27´10-4 eV) as compared with that of G1 (5.27´10-4 eV) due to the formation of As-V or Sb-V dΠdΠ bonds, which is absent in the case of the binary glass G1. The Log (Δν (Hz)) versus 103/T (K-1) plots of the glasses in the range 10-473 K are characterized by three regimes, viz. ω0τc>>1, w0tc=1 and ω0τc<<1 where ω0 is the resonance frequency in rad/s and τc is the correlation time of the polaron in the glassy matrices. The calculated values of the V4+(3d1) small polaron hopping activation energies due to viscosity effect on the tumbling of the paramagnetic sites in the regime ω0τc<<1 is found to be ~ 100 times higher than the activation energy of hopping (EEPR) due to life time broadening of the EPR lineshapes in the regime ω0τc>>1, which again are significantly different from the activation energies obtained for the glasses G1-G3, as 0.358, 0.619 and 0.509 eV, respectively from the DC electrical conductivity in the range ~300-473 K. It shows that the mechanism DC electrical conductivity in these glasses is different from the mechanism of EPR line narrowing.

IPC Code: Int. Cl.8 G01R33/60

 

Indian Journal of Chemistry

Vol. 45A, November 2006, pp. 2406-2411

 

Synthesis, characterisation and substitution reaction of trans-(diaqua)(N,N´-ethylene-bis-salicylamide)chromium(III) ion

S C Dash, G S Brahma, R Das, N N Das* & P Mohanty*

Received 27 March 2006; revised 7 September  2006

Trans-[Cr(Salm)(OH2)2]NO3 has been synthesized and characterized by various physicochemical methods. The kinetics of substitution of [Cr(Salm)(OH2)2]+ with different nucleophiles, viz., thiocyanate (SCN-), azide (N3-), imidazole (Imz), pyridine (Py), pyridine-2-caroxylic acid (pyc-2) and pyridine-3-caroxylic acid (Pyc-3) has been studied spectrophotometrically at 25-45°C (I = 0.5 mol dm-3 (KNO3), 4.0 £ pH £ 7.5). The reactions take place via outersphere association between the Cr(III) complex and various nucleophiles followed by transformation of the outer into inner sphere complexes by slow interchange. kan (25°C, 104) values are 18.91 (SCN-),  11.50 (N3-), 9.51 (Imz), 14.54 (Py), 17.6 (Pyc-2), and 18.76 (Pyc-3) and the corresponding DH# (kJ/mol) values are 63.1 ± 3.2, 70.6 ± 7.2, 46.4 ± 2.4, 40.7 ± 4.8, 28.3 ± 0.2 and 38.33 ± 6.5, the DS# (JK-1mol-1) values are -95.9 ± 9.5, -73 ± 21.5, -144 ± 3, -169 ± 16, -201 ± 0.6 and  -172 ± 19. The higher value of kan in comparison to kex and highly negative values of activation entropy and wide variation of kan by changing nucleophiles, support Ia mechanism for the substitution reactions.

IPC Code: Int. Cl.8  C07F11/00

 

Indian Journal of Chemistry

Vol. 45A, November 2006, pp. 2412-2417

 

Kinetics of oxidation of procaine hydrochloride by sodium N-chlorobenzene-sulfonamide in acid and alkaline media: A mechanistic approach

 

Puttaswamy*& J P Shubha

Received 20 March 2006; revised 22 September 2006

A kinetic study of oxidation of procaine hydrochloride (one of the potent local anaesthetics) by sodium N-chlorobenzene­sulfonamide (chloramine-B or CAB) has been carried out in HClO4 (30°C) and NaOH (20°C) media. In acid medium, the rate shows first-order dependence on [CAB]o and fractional–order dependence on [substrate]o. But, it is independent of the [acid]. In alkaline medium, the rate exhibits first-order dependence each on [CAB]o and [substrate]o, and inverse fractional-order on [OH-]. Activation parameters have been evaluated. The reaction is found to be faster in alkaline medium in comparison with acid medium. The conjugate free acid C6H5SO2NHCl of CAB is postulated as the reactive oxidizing species in both the media. The observed results have been explained by plausible mechanisms and the related rate laws have been deduced.

IPC Code: Int. Cl.8 C07B33/00

 

Indian Journal of Chemistry

Vol. 45A, November 2006, pp. 2418-2420

 

Synthesis and characterization of cryptates of Y(III), La(III), Gd(III), Yb(III) with a N2O6 cryptand

Yong Huang, Wei Wang, Lan Yan & Rudong Yang*

Received 30 November 2005; revised 7 September 2006

Four solid cryptates of a cage-type N2O6-heteroatom cryptand (L) with RE(III) nitrates (RE = Y, La, Gd, Yb) have been prepared and characterized by elemental analyses, IR spectra, thermogravimetric analyses and molar conductance measurements. Data show that the cryptand forms stable complexes with rare earth nitrates in the ratio 2:1 with the general formula RE2(NO3)6·L·H2O. The structure suggested based on the study is [RE(L)(NO3)(H2O)][RE(NO3)5].

IPC Code: Int. Cl.8 C07F5/00

 

Indian Journal of Chemistry

Vol. 45A, November 2006, pp. 2421-2425

 

Complexes of the Schiff base derived from 4-aminophenyl benzimidazole and 2, 2'- dehydropyrollidene-N-aldehyde with Zn (II), Cd (II) and Hg (II) halides

S Rekha & K R Nagasundara*

Received 22 August 2006

A new Schiff base, dhpyr4apbi, has been synthesized from 4-aminophenyl benzimidazole and 2, 2'- dehydropyrollidene-N-aldehyde and its complexes with Zn (II), Cd (II) and Hg (II) halides have been prepared. Physicochemical properties of these metal complexes have been investigated using elemental analysis, molar conductance, proton NMR and IR measurements. The complexes are non-electrolytes and are dimeric in nature with the empirical formula M2L2X4 (M = Zn, Cd, Hg; X = Cl, Br.). The minimum energy configuration has been obtained for these complexes using the molecular model Pro Plus. All the complexes have been screened for their biological activities. The Cd(II) and Hg(II) complexes show moderate antibacterial activity against Pseudomonas fluorescens.

IPC Code: Int. Cl.8 C07C251/02; C07F3/06; C07F3/08; C07F3/10

Indian Journal of Chemistry

Vol. 45A, November 2006, pp. 2426-2430

 

Synthesis, spectroscopic and structural features of diorganotin(IV) oximates derived from 9,10-phenanthrenequinone monooxime

Mayur Sharma, Sarita Jangir, C K Ojha & P Pardasani*

Received 24 February 2006; revised 11 September 2006

Reactions of monofunctional 9,10-phenanthrenequinone monooxime with dialkyl/diaryl-tin dichloride in desired molar ratios in refluxing benzene affords corresponding dialkyl-/diaryl-tin(IV) oximates, which have been characterized by elemental analyses (C, H, N and Sn), IR, multinuclear (1H, 13C and 119Sn) NMR and mass spectroscopy. On the basis of calculation of C-Sn-C bond angle from coupling constant, trigonal-bipyramidal and octahedral geometry are proposed for the chelates 5a-5c and 6a-6c. Semiempirical studies have been carried out to understand the tautomeric and conformational behaviour of the ligand.

IPC Code: Int. Cl.8  C07F7/22

 

Indian Journal of Chemistry

Vol. 45A, November 2006, pp. 2431-2434

 

Cu(II) catalysed oxidation of o-mercapto-benzoic acid by methylene blue in acidic medium: A kinetic study

R Gupta, R Chaturvedi & K K Mishra*

Received 24 February 2006; revised 20 September 2006

Kinetics of oxidation of o-mercaptobenzoic acid by methylene blue catalyzed by Cu(II) in presence of sulphuric acid and in aqueous ethanol medium (4% v/v) have been studied. Two moles of the substrate are oxidized by one mole of methylene blue forming the disulphide and the leuco dye as the end products. The order in methylene blue is 3/2 which increases to two at lower concentrations of Cu(II). The order in o-mercaptobenzoic acid is nearly zero. The rate is independent of variation in [H+] but at higher concentrations, the rate decreases to give a limiting value. The rate is not influenced on varying [Cu(II)] at higher levels but at lower concentrations (ca. < 6.0 ×10-6 M), there is a linear relationship between the rate and [Cu(II)]. The addition of reaction products does not influence the rate. Activation parameters have been evaluated and a plausible reaction scheme, presuming the reaction between metal – TSA complex and MB dimer as the rate determining step, has been proposed.

IPC Code: Int. Cl.8  C07B33/00

Indian Journal of Chemistry

Vol. 45A, November 2006, pp. 2435-2440

 

Kinetics of oxidation of thymine by t-butoxyl radical — Protection and repair by caffeic acid

Lingareddy Charitha & Mundra Adinarayana *

Received 9 April 2006; revised 17 August 2006

The kinetics of oxidation of thymine and caffeic acid by t-BuO· has been studied by the photolysis of t-butyl hydroperoxide in presence of t-butanol. The rates and the quantum yields (j) of oxidation of caffeic acid by t-BuO· radicals have been determined by varying concentrations of thymine. An increase in [thymine] has been found to decrease the rate of oxidation of caffeic acid suggesting that thymine and caffeic acid compete for t-BuO· radicals. From competition kinetics, the rate constant of t-BuO· - thymine reaction has been calculated to be 5.3´107 dm3 mol-1 s-1. The experimentally determined quantum yields (jexptl) and the calculated yields (jcal) of oxidation of caffeic acid, assuming that caffeic acid reacts only with t-BuO· radicals, suggest that caffeic acid not only protects thymine from t-BuO· radicals but also repairs thymine radicals formed by the reaction of t-BuO· radicals.

IPC Code: Int. Cl.8 C07B33/00

Indian Journal of Chemistry

Vol. 45A, November 2006, pp. 2441-2445

 

Kinetics and mechanism of oxidation of secondary alcohols by benzyltriethyl-ammonium chlorochromate

Ravdeep Kaur, Neelam Soni & Vinita Sharma*

Received 27 March 2006; revised 28 July 2006

Oxidation of several aliphatic secondary alcohols by benzyltriethylammonium chlorochromate in dimethylsulfoxide leads to the formation of corresponding ketones. The reaction is first order each in benzyltriethylammonium chlorochromate and the alcohols. The reaction is catalysed by hydrogen ions. Hydrogen‑ion dependence has the form: kobs = a + b [H+]. The oxidation of benzhydrol-a-d exhibits a substantial primary kinetic isotope effect (kH/kD = 6.12 at 288 K). Oxidation of 2-propanol has been studied in nineteen different organic solvents. The solvent effect has been analysed using Taft's and Swain's multiparametric equations. The reaction has been subjected to both polar and steric effects of the substituents. A mechanism involving transfer of hydride ion from alcohol to the oxidant via a chromate ester is also proposed.

IPC Code: Int. Cl.8  C07B33/00

Indian Journal of Chemistry

Vol. 45A, November 2006, pp. 2446-2449

 

Highly selective chloride poly(vinyl chloride) membrane electrode based on vanadium(IV) oxide acetylacetonate

 

Rakesh Kumar Mahajan* & Pallavi Sood

Received 20 April 2006; revised 21 September 2006

The response characteristics of a new solvent-polymeric membrane electrode with unique selectivity and detection limit towards chloride anion is reported here. The electrode is prepared by incorporating vanadium(IV) oxide acetylacetonate into a plasticized PVC-membrane. The resulting sensor exhibits high selectivity for chloride anion over other anions, including lipophilic inorganic anions like nitrate and perchlorate, etc. The electrode has a linear dynamic range 2.5´10-5-1.0´10-1 M with a Nernstian slope –55.0±2 mV per decade and a low detection limit 4.27´10-6 M. The potentiometric response has been found to be independent of pH of the solution in the pH range 3.5-9.0. The electrode can be used for at least 9 months without any considerable divergence in its potential. It can be used as an indicator electrode in the potentiometric titration of silver ions.

IPC Code: Int. Cl.8 G01N27/333