Simultaneous extraction and determination of anionic surfactants in waters and sediments

A new method has been developed for the simultaneous determination of the most frequently used anionic surfactants - linear alkylbenzene sulfonates (LAS), alkyl ethoxysulfates (AES) and alkyl sulfates (AS) - in aqueous and sediment samples. Preconcentration and purification of water samples are carried out by means of solid-phase extraction (SPE). The efficiency of two different extraction methods for the analysis of sediments - Soxhlet extraction and pressurized liquid extraction (PLE) - has been compared. Identification and quantification of the target compounds is performed using a liquid chromatography - mass spectrometry (LC-MS) system equipped with an electrospray interface (ESI) in negative ion-mode. Homologue recoveries are 85-123% for SPE, 94-112% for Soxhlet extraction and 81-125% for PLE in the case of LAS, and 60-94% for SPE, 61-109% for Soxhlet extraction and 55-99% for PLE in the case of AES, whereas the limits of detection are 0.1-0.5 ngml(-1) in water and 1-5 ngg(-1) in sediment. This method has been applied to the determination of anionic surfactants in the Guadalete estuary (SW Spain), and LAS concentration levels from 538 to 1014 ngg(-1) in sediments and from 25.1 to 64.4 ngml(-1) in waters have been found. AES values from 168 to 536 ngg(-1) in sediments and from 4.5 to 11.9 ngml(-1) in waters are reported for the first time in European rivers.     

Spectrophotometric study of the reaction mechanism between DDQ Pi- and iodine sigma-acceptors and chloroquine and pyrimethamine drugs and their determination in pure and in dosage forms

Two simple and accurate spectrophotometric methods are presented for the determination of anti-malarial drugs, chloroquine phosphate (CQP) and pyrimethamine (PYM), in pure and in different pharmaceutical preparations. The charge transphere (CT) reactions between CQP and PYM as electron donors and 2,3-dichloro-5,6-dicyano-p-benzoquinone (DDQ) pi-acceptor and iodine sigma-acceptor reagents to give highly coloured complex species have been spectrophotometrically studied. The optimum experimental conditions have been studied carefully. Beer' law is obeyed over the concentration range of 1.0-15 microg ml(-1) for CQP and 1.0-40 microg ml(-1) for PYM using I(2) and at 5.0-53 microg ml(-1) for CQP and 1.0-46 microg ml(-1) for PYM using DDQ reagents, respectively. For more accurate results, Ringbom optimum concentration range is calculated and found to be 10-53 and 8-46 microg ml(-1) for CQP and PYM using DDQ, respectively and 5-15 and 8-40 microg ml(-1) for CQP and PYM using iodine, respectively. The Sandell sensitivity is found to be 0.038 and 0.046 g cm(-2) for DDQ method and 0.0078 and 0.056 g cm(-2) for I(2) method for CQP and PYM, respectively which indicates the high sensitivity of both methods. Standard deviation (S.D.=0.012-0.014 and 0.013-0.015) and relative standard deviation (R.S.D.=0.09-1.4 and 1.3-1.5%) (n=5) for DDQ and I(2) methods respectively, refer to the high accuracy and precision of the proposed methods. These results are also confirmed by between day precision of percent recovery of 99-100.6%, and 98-101% for CQP and PYM by DDQ method and 99-102% and 99.2-101.4% for CQP and PYM by I(2) method respectively. These data are comparable to those obtained by British and American pharmacopoeias assay for the determination of CQP and PYM in raw materials and in pharmaceutical preparations.     

Spectrophotometric methods for determination of enalapril and timolol in bulk and in drug formulations

Two simple and accurate spectrophotometric methods for determination of timolol and enalapril maleate are described. The first method is based on chelate formation with palladium(II) chloride in buffered medium. The second method is based on the formation of the colored complex between palladium(II), eosin, and the two cited drugs using methylcellulose as surfactant to increase the solubility and intensity of the formed complexes. Under optimum conditions the complexes showed maximum absorption at 369.4 nm and 362.8 nm for timolol and enalapril maleate, respectively, in the first method and 552.2 and 550.6 nm for the second method. Apparent molar absorptivities were 1.8 x 10(3) and 1.3 x 10(3) and Sandell's sensitivities were 5.9 x 10(-4) and 2.7 x 10(-4) for timolol and enalapril maleate in the first method; in the second method molar absorptivities were 2.8 x 10(4) and 1.1 x 10(4) while Sandell's constants were 9.1 x 10(-3) and 2.3 x 10(-3) for timolol and enalapril maleate. The solutions of the complexes obeyed Beer's law in the concentration ranges 20-200 micro g mL(-1) and 50-300 micro g mL(-1) for timolol and enalapril maleate, respectively. In the second method, because the reaction was more sensitive the ranges were reduced to 1.6-16 micro g mL(-1) for timolol 8-56 micro g mL(-1) for enalapril maleate. The proposed methods were applied to the determination of the two drugs in their pharmaceutical formulation.     

Spectrophotometric determination of flucloxacillin and dicloxacillin in pure and dosage forms

A simple, rapid and accurate spectrophotometric method for the determination of antibiotic drugs, flucloxacillin (Fluclox) and dicloxacillin (Diclox), in pure form and different pharmaceutical preparations has been developed. The charge transfer (CT) reactions between Fluclox and Diclox as electron donors and 7,7,8,8-tetracyanoquinodimethane (TCNQ) and tetracyanoethylene (TCNE) as pi-acceptors to give highly coloured complex species have been spectrophotometrically studied. The optimum experimental conditions for these CT reactions have been studied carefully. Beer's law is obeyed over the concentration ranges of 4-180 microg mL(-1) and 4-70 microg mL(-1) for Fluclox and Diclox drugs using TCNQ and TCNE reagents, respectively. The Sandell sensitivities (S) are found to be 0.016-0.035 microg cm(-2) and 0.011-0.016 microg cm(-2) for Fluclox and Diclox, respectively, which indicate the high sensitivity of the proposed method. The relative standard deviations (R.S.D.: 0.08-0.49 and 0.15-0.80) for the determination of Fluclox and (R.S.D.: 0.05-0.75 and 0.13-0.75) for Diclox were obtained for four to six replicates using TCNQ and TCNE reagents, respectively, refer to the high accuracy and precision of the proposed method. These results are also confirmed by the between-day precision and the percent recovery of 99.90-100.1 and 99.60-100.4 for Fluclox and 99.90-100.5 and 99.40-100.1 for Diclox using TNCQ and TCNE reagents, respectively. The results obtained for the two reagents are comparable with those obtained by the official method.     

Spectrophotometric study of the reaction mechanism between DDQ as pi-acceptor and potassium iodate and flucloxacillin and dicloxacillin drugs and their determination in pure and in dosage forms

Two simple and accurate spectrophotometric methods are presented for the determination of beta-lactam drugs, flucloxacillin (Fluclox) and dicloxacillin (Diclox), in pure and in different pharmaceutical preparations. The charge transfer (CT) reactions between Fluclox and Diclox as electron donors and 2,3-dichloro-5,6-dicyano-p-benzoquinone (DDQ) pi-acceptor and potassium iodate via oxidation reduction reaction where the highly coloured complex species or the liberated iodine have been spectrophotometrically studied. The optimum experimental conditions have been studied carefully. Beer's law is obeyed over the concentration range of 2-450 microg ml(-1) for Fluclox and 10-450 microg ml(-1) for Diclox using DDQ reagent and at 50-550 microg ml(-1) for Fluclox and 50-560 microg ml(-1) for Diclox using iodate method, respectively. For more accurate results, Ringbom optimum concentration range is calculated and found to be 6-450 and 15-450 microg ml(-1) for Fluclox and Diclox using DDQ, respectively, and 65-550 and 63-560 microg ml(-1) for Fluclox and Diclox using iodine, respectively. The Sandell sensitivity is found to be 0.018 and 0.011 microg cm(-2) for DDQ method and 0.013 and 0.011 microg cm(-2) for iodate method for Fluclox and Diclox, respectively, which indicates the high sensitivity of both methods. Standard deviation (S.D.=0.01-0.80 and 0.07-0.98) and relative standard deviation (R.S.D.=0.13-0.44 and 0.11-0.82%) (n=5) for DDQ and iodate methods, respectively, refer to the high accuracy and precision of the proposed methods. These results are also confirmed by between-day precision of percent recovery of 99.87-100.2 and 99.90-100% for Fluclox and Diclox by DDQ method and 99.88-100.1 and 99.30-100.2% for Fluclox and Diclox by iodate method, respectively. These data are comparable to those obtained by British and American pharmacopoeias assay for the determination of Fluclox and Diclox in raw materials and in pharmaceutical preparations.     

Spectrophotometric and potentiometric determination of piroxicam and tenoxicam in pharmaceutical preparations

Two simple and accurate methods are described for the determination of piroxicam and tenoxicam in their pharmaceutical preparations. The spectrophotometric method involves the oxidation of these drugs with potassium iodate in acid medium with the liberation of iodine and subsequent extraction with cyclohexane followed by measuring the absorbance at lambda=522 nm. Beer's law is obeyed in the concentration range of 0.05-1.1 and 0.05-0.6 mg x ml(-1) for piroxicam and tenoxicam, respectively. The apparent molar absorptivities of the resulting coloured products are found to be 2.7 x 10(3) and 2.5 x 10(3) l mol(-1) x cm(-1), whereas Sandell sensitivities are 0.012 and 0.013 g x cm(-2) for piroxicam and tenoxicam, respectively. The potentiometric method involves the direct titration of both drugs with N-bromosuccinimide in acid medium and the end point is determined potentiometrically using platinum indicator electrode. Piroxicam and tenoxicam can be determined quantitatively in the concentration range of 0.33-3.37 and 0.33-4.08 mg x ml(-1) for tenoxicam and piroxicam, respectively. The standard deviation and relative standard deviation values are found to be ranged from 0.05-0.07 and 0.37-0.98% and 0.025-0.078 and 0.25-1.2% for tenoxicam and piroxicam, respectively. The two methods are accurate within +/-1.0%. Optimum conditions affecting both methods are studied. The proposed methods are applied for the determination of the drugs in pure form and in commercial pharmaceutical preparations.     

Ultratrace analysis of uranium and thorium in glass

Three methods of determination for uranium and thorium traces and ultratraces in glass were developed: a simple and powerful ICP-MS method exhibiting limits of determination in the one ng/g-range; a complex method with end-determination by classical photometry and a limit of determination for U and Th of 20 ng/g; and a method with chelate-complex formation for U and Th and subsequent GC-detection with a ⁶³Ni-ECD with limits of determination in the g/g-range. These methods are critically compared and tested for real type samples of special glasses.Abbreviations used AAS Atomic absorption spectrophotometry - ECD Electron capture detector - FOD 1,1,1,2,2,3,3-Heptafluoro-7,7-dimethyl-4,6-octanedion - GC Gas chromatography - HFA 1,1,1,5,5,5-Hexafluoro-2,4-pentanedione - ICP-AES, -MS Inductively coupled plasma-atomic emission spectrometry, metry, -mass spectrometry - LAS Liquid absorption spectrophotometry = classical photometry - NAA Neutron activation analysis - NIST National Institute of Standardization and Technology (Gaithersburg, U.S.A.) - TBP Tri-(n-butyl)-phosphate - TFA 1,1,1-Trifluoro-2,4-pentanedione - TTFA 1-(2-Thenoyl)-3,3,3-trifluoroacetone - XRS X-ray (fluorescence) spectrometry     

Spectrophotometric and spectrodensitometric determination of paracetamol and drotaverine HCl in combination

Thin-layer chromatography, first derivative, ratio spectra derivative spectrophotometry and Vierordt's method have been developed for the simultaneous determination of paracetamol and drotaverine HCl. TLC densitometric method depends on the difference in Rf values using ethyl acetate:methanol:ammonia (100:1:5 v/v/v) as a mobile phase. The spots of the two drugs were scanned at 249 and 308 nm over concentration ranges of 60-1200 microg/ml and 20-400 microg/ml with mean percentage recovery 100.11%+/-1.91 and 100.15%+/-1.87, respectively. The first derivative spectrophotometric method deals with the measurements at zero-crossing points 259 and 325 nm with mean percentage recovery 99.25%+/-1.08 and 99.45%+/-1.14, respectively. The ratio spectra first derivative technique was used at 246 and 305 nm with mean percentage recovery 99.75%+/-1.93 and 99.08%+/-1.22, respectively. Beer's law for first derivative and ratio spectra derivative methods was obeyed in the concentration range 0.8-12.8 and 0.4-6.4 microg/ml of paracetamol and drotaverine HCl, respectively. Vierordt's method was applied to over come the overlapping of paracetamol and drotaverine HCl in zero-order spectra in concentration range 2-26 and 2-40 microg/ml respectively. The suggested methods were successfully applied for the analysis of the two drugs in laboratory prepared mixtures and their pharmaceutical formulation. The validity of the methods was assessed by applying the standard addition technique. The obtained results were statistically agreed with those obtained by the reported method.     

粤航一号稻米及其亲本抗性淀粉含量的测定与比较

为确定航天品种功能稻米——粤航一号抗性淀粉含量,给临床观察膳食干预后果判断提供实验参考数据,并了解航天育种对该品种大米抗性淀粉含量的影响,用Goni测定方法测定了粤航一号、富硒粤航一号、长丝占、粳籼89 4种稻米的抗性淀粉含量。结果表明,粤航一号、富硒粤航一号、长丝占、粳籼89 4种稻米的抗性淀粉含量分别是(0.30±0.11)%、(0.47±0.37)%、(0.31±0.66)%、(0.36±0.62)%。可见粤航一号与亲本长丝占,及与富硒品种富硒粤航一号,和非航天品种优质大米粳籼89在抗性淀粉含量上无差异,航天育种对该品种稻米抗性淀粉生成遗传特征无影响。     

毛细管电泳对微生物代谢中硫酸根和硫代硫酸根的分离与测定

建立了微生物代谢中硫酸根和硫代硫酸根的毛细管电泳分析方法．在选定实验条件下，各种阴离子（Ｓ２Ｏ２－３、ＳＯ２－４、ＣＩ－、ＮＯ－３、ＰＯ３－４）在４ ｍｉｎ内达到完全分离，其中 Ｓ２Ｏ２－３和ＳＯ２－４迁移时间的相对标准偏差小于１％，峰面积的相对标准偏差小于５％．测定了４种菌株分别在两种培养基中的Ｓ２Ｏ２－３和ＳＯ２－４浓度随培养时间的变化．结果表明，其中一菌株在ＳＫ基中对Ｓ２Ｏ２－３有明显的氧化作用．     

Spectrophotometric studies and applications for the determination of yttrium in pure and in nickel base alloys

Yttrium reacts with 5-(4'-chlorophenylazo)-6-hydroxypyrimidine-2,4-dione (I), 5-(2'-bromophenylazo)-6-hydroxypyrimidine-2,4-dione (II), 5-(2',4'-dimethylphenylazo)-6-hydroxypyrimidine-2,4-dione (III), 5-(4'-nitro-2',6'-dichlorophenylazo)-6-hydroxypyrimidine-2,4-dione (IV), 5-(2'-methyl-4'-hydroxyphenylazo)-6-hydroxypyrimidine-2,4-dione (V) to form a dark pink complexes, having an absorption maximum at 610, 577, 596, 567 and 585 nm, respectively. The complex formation was completed spontaneously in theil buffer solution and the resulting complex was stable for at least 3 h after dilution. Under the optimum conditions employed, the molar absorptivities were found to be 1.60 x 10(4), 1.29 x 10(4), 1.96 x 10(4), 1.45 x 10(4) and 1.21 x 10(4) l mol(-1) cm(-1) and the molar ratios were (1:1) and (1:2) (M:L). The linear ranges were found within 95 microg of yttrium in 25 ml solution. One of the characteristics of the complex was its high tolerance for calcium and hence a method of separation and enrichment of microamounts of yttrium by using calcium oxalate precipitate was developed and applied to measure yttrium in nickel-base alloys. Interfering species and their elimination have been studied. The precision and recovery are both satisfactory.     

Determination and dynamics of difenoconazole residues in Chinese cabbage and soil

An analytical method was developed using a solid phase extraction （SPE） cleanup and gas chromatography for detecting the residues of difenoconazole in Chinese cabbage and soil. The recovery and the relative standard deviation of this method in Chinese cabbage was 87.6-99.0%, 1.71-10.50%, respectively; in soil was 92.4-95.5%, 4.93-10.70%, respectively. Further degradation of difenoconazole residue in Chinese cabbage and soil was studied to evaluate residue behavior and environmental safety of difenoconazole. Degradation rate of difenoconazole in both Chinese cabbage and soil followed the first order kinetics with the half-lives of 6.6-7.8 and 54.2-55.0 days, respectively.     

Solubility and protonation of EDTA, DCTA and DPTA in acidic perchlorate medium

From measurements of solubility as a function of pC(H), the protonation constants of EDTA, DCTA and DTPA for the first dissociation and addition steps have been determined. The following values were found: EDTA: log k(6) = -0.10 +/- 0.05, log k(5) = 1.45 +/- 0.02, log k(4) = 1.95 +/- 0.02 and log k(3) = 2.50 +/- 0.03; DCTA: log k(5) = 1.78 +/- 0.02, log k(4) = 2.30 +/- 0.02 and log k(3) = 3.50 +/- 0.03; DTPA: log k(7) = 0.75 +/- 0.03, log k(6)= 1.22 +/- 0.02 and log k(5) = 2.08 +/- 0.02. The experiments were done in acidic perchlorate medium (I = 1.0) at room temperature (21 degrees ).     

Kinetics and mechanisms of the reactions of hydroxyl radicals and hydrated electrons with nitrosamines and nitramines in water

Absolute rate constants for hydroxyl radical, *OH, and hydrated electron, e(aq)(-), reactions with low-molecular-weight nitrosamines and nitramines in water at room temperature were measured using the techniques of electron pulse radiolysis and transient absorption spectroscopy. The bimolecular rate constants obtained, k (M(-1) s(-1)), for e(aq)(-) and *OH reactions, respectively, were as follows: methylethylnitrosamine, (1.67 +/- 0.06) x 10(10) and (4.95 +/- 0.21) x 10(8); diethylnitrosamine, (1.61 +/- 0.06) x 10(10) and (6.99 +/- 0.28) x 10(8); dimethylnitramine, (1.91 +/- 0.07) x 10(10) and (5.44 +/- 0.20) x 10(8); methylethylnitramine, (1.83 +/- 0.15) x 10(10) and (7.60 +/- 0.43) x 10(8); and diethylnitramine, (1.76 +/- 0.07) x 10(10) and (8.67 +/- 0.48) x 10(8), respectively. MNP/DMPO spin-trapping experiments demonstrated that hydroxyl radical reaction with these compounds occurs by hydrogen atom abstraction from an alkyl group, while the reaction of the hydrated electron was to form a transient radical anion. The latter adduct formation implies that the excess electron could subsequently be transferred to regenerate the parent chemical, which would significantly reduce the effectiveness of any free-radical-based remediation effort on nitrosamine/nitramine-contaminated waters.     

Photodissociation of p-xylene in polar and nonpolar solutions

The photodissociation of p-xylene at 266 nm in n-heptane and acetonitrile has been studied with use of nanosecond fluorescence and absorption spectroscopy. The p-methylbenzyl radical was identified in n-heptane and acetonitrile by its fluorescence, which was induced by excitation at 308 nm. The p-xylene radical cation was observed in acetonitrile by its absorption. In n-heptane, the decay rate of the S(1) state of p-xylene ((3.2 +/- 0.2) x 10(7) s(-1)) is equal to the growth rate of the p-methylbenzyl radical ((2.7 +/- 0.4) x 10(7) s(-1)), showing that the molecule dissociates via the S(1) state into the radical by C-H bond homolysis (quantum efficiency approximately 5.0 x 10(-3)). In acetonitrile, the formation of the p-xylene radical cation requires two 266 nm photons, and the decay rate of the radical cation ((1.6 +/- 0.2) x 10(6) s(-1)) equals the growth rate of the p-methylbenzyl radical ((2.0 +/- 0.2) x 10(6) s(-1)). This shows that the radical cation dissociates into the radical by deprotonation (quantum efficiency approximately 8.9 x 10(-2)).     

微环境影响下的乙酰基香豆素与吲哚的固相光反应

本文研究了乙酰基香豆素及其衍生物与吲哚的混晶在微环境影响下的固相光反应，并用固体紫外光谱、固体荧光光谱和X-射线粉末衍射技术考察了混晶的特征。实验结果表明，3-乙酰基香豆素及其7-乙酰氧基、7-苯甲酰氧基、5,6-苯并和6-溴衍生物与吲哚的固相光反应分别得到1:2缩合产物1～5，而6-硝基衍生物与吲哚的固相光反应却得到开环脱羰加成产物6。通过IR、MS、^1H NMR和元素分析结果确定了这六个新产物的结构。固体光谱的测试结果表明，取代乙酰基香豆素与吲哚间混晶的形成，分子间存在相互作用，使分子所处的微环境条件发生了变化。     

Kinetics of the initiated and inhibited oxidation of methyl oleate in homogeneous and aqueous emulsion media

The kinetics of the 2,2′-azobisisobutyronitrile-initiated oxidation of methyl oleate (MO) in the medium of the oxidized substrate itself (homogeneous system) and in an aqueous solution of cetyltrimethylammonium bromide (aqueous emulsion system, AES) was studied. The oxidation was found to occur as a nonbranched chain reaction with quadratic-law chain termination in both neat methyl oleate ([MO] ≈ 2.6 mol/l) and AES. The temperature dependence of the oxidizability parameter for methyl oleate in the temperature range from 303 to 333 K was described by the following expressions:

Photoisomerization of naphthylquinolylethylenes in neutral and protonated forms

The quantum yield of the trans-cis photoisomerization of 1-(1-naphthyl)-2-(2-quinolyl)ethylene and 1-(2-naphthyl)-2-(2-quinolyl)ethylene is close to the theoretical limit (0.5) for diabatic photoisomerization and does not change on passing from the neutral to the protonated form. The data obtained indicate the absence of the α-effect for the test compounds, which consists in an increase in the trans-cis photoisomerization quantum yield to values of >0.5 upon protonation of some azadiarylethylenes with the nitrogen atom in the α-position to the ethylene group.     

Flow-injection chemiluminescence determination of ofloxacin and levofloxacin in pharmaceutical preparations and biological fluids.

A novel, rapid and sensitive analytical method is described for determination of ofloxacin and levofloxacin by enhanced chemiluminescence (CL) with flow-injection sampling. The method is based on the CL reaction of the Ce(IV)-Na2S2O4-ofloxacin/levofloxacin-H2SO2 system. The enhanced CL mechanism was developed and the optimum conditions for CL emission were investigated. The CL intensity was correlated linearly (r = 0.9988) with the concentration of ofloxacin (or levofloxacin) in the range of 1.0 x 10(-8) - 1.0 x 10(-7) g ml(-1) and 1.0 x 10(-7) - 6.0 x 10(-6) g ml(-1). The detection limit (S/N = 3) is 7 x 10(-9) g ml(-1). The relative standard derivation (RSD, n = 11) is 2.0% for ofloxacin at 4 x 10(-7) g ml(-1) and for levofloxacin at 6 x 10(-7) g ml(-1). This method has been successfully applied for the determination of ofloxacin and levofloxacin in pharmaceutical preparations and biological fluids with satisfactory results.