Determination of sulphonated azo dyes in food by ion-pair liquid chromatography with photodiode array and electrospray mass spectrometry detection

An ion-pair liquid chromatography method with on-line photodiode-array and electrospray mass spectrometry detection was developed to determine 10 commonly used sulphonated azo dyes (Tartrazine, Amaranth, New Coccine, Sunset Yellow FCF, Allura Red AC, Ponceau R, Ponceau 3R, Orange I, Orange II and Metanil Yellow) in food. A reversed phase C(18) column with gradient elution was utilized to separate these compounds. Triethylamine was added in the mobile phase as an ion-pair reagent for chromatographic separation. Photodiode-array detection was employed for quantitative determination and electrospray mass spectrometry was used for identification. Good linearity (0.05-10 ppm, r(2)=0.999) and detection limit (<0.01 ppm) were determined with 5 mul injection. In addition, precision and accuracy associated with this newly developed method will be presented. A liquid extraction method was also developed to extract these dyes from different foodstuffs. The application of this method was demonstrated by analyzing sulphonated azo dyes in soft drinks, fruit jam, and salted vegetables.     

Development of a Solid-Phase Extraction Procedure for the Simultaneous Determination of Polyphenols, Organic Acids and Sugars in Wine

A solid-phase extraction (SPE) procedure that fractionates wine samples into 2 sub-samples containing sugars and organic acids (sub-sample 1) and low molecular weight polyphenols (sub-sample 2), respectively, together with rugged LC procedures for their analyses are described. Wine is adjusted to pH 2.5 and loaded on a styrene-divinylbenzene (SDB) cartridge. The organic acids and sugars are eluted with 20 mM sulphuric acid and the monomeric polyphenols with ethyl acetate. Glucose and fructose are analysed by normal phase LC with evaporative light scattering detection and the organic acids by ion exclusion chromatography with UV detection at 210 nm. Analysis of the phenolic fraction is performed by reversed phase LC with diode array detection. Recoveries and repeatabilitys for 27 standard compounds (2 sugars, 7 organic acids and 18 polyphenols) are presented. The method represents an improvement in terms of productivity and robustness compared to currently used procedures.     

Analytical method for the determination of the aminoglycoside gentamicin in hospital wastewater via liquid chromatography-electrospray-tandem mass spectrometry

A method for the determination of gentamicin residues in hospital wastewater has been developed using kanamycin as a surrogate standard. The method consists of solid-phase extraction (SPE) and detection by ion-pair chromatography with electrospray tandem mass spectrometry (LC–ES-tandem MS). The SPE was performed on a weak cation exchanger. Filtration should be avoided in the sample preparation, otherwise a significant loss of gentamicin occurs. Chromatographic separation on a C₁₈-column was achieved using a ternary eluent containing methanol, water and 20 mmol l⁻¹ heptafluorobutyric acid solution. Mean relative recoveries of the analytes in hospital wastewater varied between 107 and 111%. The limit of quantification (LOQ) was 0.20 μg l⁻¹ in hospital wastewater. Gentamicin was found in native hospital wastewater in a concentration range between 0.4 and 7.6 μg l⁻¹.     

X-ray fluorescence spectrometric determination of sulfur-containing anionic surfactants in water after their enrichment on a membrane filter as an ion-pair complex with a cationic surfactant.

Anionic surfactants containing sulfur in their structure were enriched on a mixed cellulose ester membrane filter (MF) by filtration as an ion-pair complex with a cationic surfactant. After their enrichment, the anionic surfactants were determined by X-ray fluorescence spectrometry of the sulfur enriched on the MF. A linear calibration was obtained over a concentration range from 0.05 to 0.8 mg L(-1) of sodium dodecyl sulfate as a standard material with less than 6% RSD. The detection limit based on 3s for the reagent blank was 2 microg L(-1). This method is very simple, rapid and highly selective for sulfur-containing surfactants, and does not require any organic solvent extraction. This method was applied to the determination of anionic surfactant in some urban river waters where domestic wastewater was discharged. The results were compared with those obtained by conventional solvent extraction-spectrophotometry. The distribution of the analyte complexes within the MF where the ion-pair was retained is also discussed.     

Tracing polar benzene- and naphthalenesulfonates in untreated industrial effluents and water treatment works by ion-pair chromatography-fluorescence and electrospray-mass spectrometry

This paper presents a protocol for the determination of a class of polar, ionic and highly water-soluble organic pollutants: benzene- and naphthalenesulfonic acids, compounds widely used in chemical, pharmaceutical, tannery, paper and textile industries. This protocol involves the use of a solid-phase extraction (SPE) followed by ion-pair chromatography-electrospray-mass spectrometry (IPC-ESI-MS). In this work two polymeric solid-phase extraction cartridges (Isolute ENV+ and Lichrolut EN) were compared, with the more effective being Isolute ENV+ sorbent. Recoveries and breakthrough volumes were calculated by loading volumes of 150, 200 and 300 ml of spiked ground water through the SPE columns. To enhance the effectiveness of the methodology, 1 ml of water containing 5 mM TEA was added before eluting with methanol. Average recoveries ranging from 70 to 100% were obtained for a variety of 13 analytes (only two naphthalenesulfonate compounds had recoveries below 50%.). Determination of benzene- and naphthalenesulfonates was accomplished by ion-pair chromatography-fluorescence detection (IPC-FLD).

The ESI-MS parameters were optimized to achieve maximum sensitivity. [M–H]⁻ ion was the base peak using low energies (fragmentor voltage: 80 V). Significant fragmentation of the quasi-molecular [M–H]⁻ ion occurs at higher fragmentor voltages, leading to [M–SO₂H]⁻, [M–SO₃H]⁻ and [SO₃]⁻ as diagnostic ions, but with some sensitivity losses (more than two orders of magnitude when 150 V are applied as fragmentor voltage). Collision-induced dissociation (CID) of the parent ions for the benzene- and naphthalenesulfonates studied gave the [SO₃]⁻ fragment ion common to sulfonated compounds, it has been shown to be characteristic of aromatic sulfonated compounds and could be used as a diagnostic tool to indicate the presence of these compounds.

Limits of detection (signal-to-noise ratio = 3) ranging from 0.03 pg to 0.05 ng, were achieved when 150 ml of ground water were processed and quantified by IPC-FLD. In IPC-ESI-MS, time-scheduled SIM mode with post-column addition of 0.2 m min⁻¹ of methanol was used. LODs range from 0.6 pg to 0.13 ng. In summary, with the development of a methodology based on SPE followed by IPC-ESI-MS, good sensitivity, structural information and unequivocal identification can be achieved.

This protocol was applied to the analysis of surface waters, untreated industrial waste waters and wastewater treatment works effluents and influents. In the case of tannery effluent samples, isomers of naphthalenesulfonic acid were found as major pollutants in concentrations up to 0.8 and 1.0 mg l⁻¹, for 1-naphthalenesulfonate and 2-naphthalenesulfonate, respectively. The main contaminants in wastewater treatment work samples were 2,6-naphthalenedisulfonate, 1-hydroxy-3,6-naphthalenedisulfonate, 3-nitrobenzenesulfonate, 1-naphthalenesulfonate and 2-naphthalenesulfonate, with levels of ug/l.     

Accurate Determination of Tributyltin in Tannery Wastewater by a New Procedure Using ID-HPLC–ICP-MS Combined with Low Temperature Extraction

Isotope dilution mass spectrometry is recognized as a primary method to obtain traceable values in the measurement of substances including trace elements and their organometallic compounds. This paper reports a novel method where isotope dilution high performance liquid chromatography inductively coupled plasma mass spectrometry (ID-HPLC–ICP-MS) was combined with low temperature extraction for the determination of tributyltin (TBT) in tannery wastewater from the leather industry. It has been found that the liquid–liquid extraction at very low temperature is in the favor of extraction of organotin, as the enrichment factor for low temperature (?80 °C) extraction was about 1.3 times higher than for extraction at room temperature (20 °C). The method detection limit of TBT, obtained from the proposed ID-HPLC–ICP-MS procedure after extraction with a sample volume of 7.5 by 2.5 mL of organic phase, was found to be 0.13 ng g^?1. When TBT was determined in a range of 10–1000 ng g^?1 in tannery wastewater samples, the analyte recoveries were in the range 90.1–107.2% with relative standard deviations of between 2.0 and 7.2%. Finally, the new method of ID-HPLC–ICP-MS combined with low temperature extraction was applied to the determination of TBT in actual tannery wastewater. The TBT contents from three different tanning procedures (chrome tanning, vegetable tanning and aldehyde tanning), expressed as the mean ± the expanded uncertainty (k = 2) were 378.65 ± 20.38, 110.04 ± 5.96 and 690.17 ± 35.31 ng g^?1, respectively.     

Simultaneous Analysis of Cimetidine and Ranitidine in Human Plasma by HPLC

Abstract

A rapid method for the simultaneous quantitation of the H₂-receptor antagonist drugs cimetidine and ranitidine in human plasma by isocratic ion-pair reverse-phase HPLC is described. The method involves a simple organic extraction step of the alkalinized plasma containing added internal standard followed by back extraction of the extract with dilute acetic acid and subsequent analysis of the aqueous acidic phase on a reverse-phase (C18) column. The eluting solvent was acetonitrile-water (20:80 v/v) containing 0.005 mole/litre octanesulphonic acid and was monitored at 229 nm. The run time for the assay was 12.5 minutes, with a detection limit for cimetidine of 50 ng/m1/(0.2 μmole/1) and that for ranitidine was 20 ng/ml (0.06 umole/1).     

Ion-pair liquid-liquid-liquid microextraction of nerve agent degradation products followed by capillary electrophoresis with contactless conductivity detection

The four nerve agent degradation products methylphosphonic acid (MPA), ethyl methylphosphonic acid (EMPA), isopropyl methylphosphonic acid (IMPA) and cyclohexyl methylphosphonic acid (CMPA) have been successfully extracted from aqueous sample solution by ion-pair liquid-liquid-liquid microextraction. In this procedure, the target analytes in the sample solution were converted into their ion-pair complexes with tri-n-butyl amine and then extracted by an organic solvent (1-octanol) layer on top of the sample solution. Simultaneously, the analytes were back-extracted into a drop of an aqueous acceptor solution which was suspended in the organic phase at a microsyringe needle tip. The factors influential to extraction: type of organic solvent, type of ion-pair reagent and its concentration, pH values of sample solution and acceptor aqueous phase, stirring rate and extraction time were investigated in detail. After extraction, the drop of the acceptor solution was withdrawn into the syringe and injected into a capillary electrophoresis system for analysis. Using contactless conductivity detection, direct quantification of these compounds is possible. Moreover, large-volume sample injection was employed for further preconcentration. Improvements in the limits of detection between 2.5 and 4 orders of magnitude could be achieved and concentrations at the ng/mL level can be determined. This newly established approach was successfully applied to a spiked river water sample.     

Extractive fluorimetric determination of ultratraces of lead with cryptand 2.2.2 and eosin

A new speetrofluorimetric method for determination of ultratraces of lead is based on solvent extraction into chloroform of the ion-pair formed between the positively-charged cryptate of lead with cryptand 2.2.2 and the eosinate anion. The detection limit for lead is 1 ng ml , and the linear working range is from the detection limit to 250 ng ml . The relative standard deviation is 3.7% at the 100 ng ml level. The method is highly selective for the extraction and determination of lead in the presence of other cations, and has been tested for direct determination of lead contamination in soft drinks. Aggregation of the extracted ion-pair in the organic phase has been demonstrated in fundamental extraction studies.     

Method for the analysis in maize of the Fusarium mycotoxin moniliformin employing ion-pairing extraction and high-performance liquid chromatography

The Fusarium mycotoxin moniliformin (hydroxycyclobutenedione) has been determined in maize using a novel method with a recovery of 70-80% at 400-1600 micrograms/kg and 60% at the detection limit of 100 micrograms/kg. The method requires extraction of the toxin into aqueous tetra-n-butylammonium hydroxide and removal of cations from this solution by ion-exchange chromatography. Following clean-up by partitioning against dichloromethane, further quaternary ammonium reagent was added to the aqueous phase which was absorbed onto a hydrophilic matrix and the tetra-n-butylammonium moniliformate ion pair extracted into dichloromethane. After evaporation of the organic eluent, the residue was dissolved in aqueous sodium chloride and moniliformin quantitated by ion-pair high-performance liquid chromatography with UV detection. A batch of five samples may be analysed in 5-6 h including the chromatographic determination.     

两性化合物与离子对试剂的混合物作流动相的流动相离子色谱法测定气溶胶中水溶性阴离子

用流动相离子色谱法(MPIC),以两性化合物与离子对试剂的混合溶液为流动相,在C18柱上抑制电导检测分析气溶胶中常规无机阴离子和有机酸。实验采用氢氧化四丁基铵(TBAOH)为离子对试剂,与两性化合物3-(N-吗啉)-1-丙磺酸(MOPS)混合,加入Na2CO3无机添加剂作流动相,其浓度为1mmol／L TBAOH／5mmol／LMOPS／0．5mmol／LNa2CO3。分离柱采用硅质C18柱,抑制电导检测。可以较好地分离和检测常见的无机和有机阴离子。该方法具有较好的重现性和线性关系,F^-、Cl^-、NO2^-、Br^-、C3H3O3^-、NO3^-的回收率分别为102．0％、104．6％、102．4％、97．8％、97．75％和102．5％;检出限分别为0．017、0．014、0．0048、0．036、0．16和0．017mg／L。     

Development and optimisation of a novel three‐way extraction technique based on a combination of Soxhlet extraction,membrane assisted solvent extraction and a molecularly imprinted polymer using sludge polycyclic aromatic hydrocarbons as model compounds

A novel technique that integrates extraction and clean‐up into a single step format is reported as part of the search for new sample preparation techniques in the analysis of persistent organic pollutants from complex samples. This was achieved by combining the extraction efficiency of the Soxhlet extractor, the selectivity of a size exclusion membrane and the specificity of a molecularly imprinted polymer for the extraction of polycyclic aromatic hydrocarbons from wastewater sludge followed by quantitation using gas chromatography with time‐of‐flight mass spectrometry. The approach is described as the Soxhlet extraction membrane‐assisted solvent extraction molecularly imprinted polymer technique. This technique was optimised for various parameters such as extraction solvent, reflux time and membrane acceptor phase. The applicability of the developed technique was optimised using a wastewater sludge certified reference material and then tested on real wastewater sludge samples. The method detection limits ranged from 0.14 to 12.86 ng/g with relative standard deviation values for the extraction of the 16 US‐EPA priority polycyclic aromatic hydrocarbons from wastewater sludge samples ranging from 0.78 to 18%. The extraction process was therefore reproducible and showed remarkable selectivity. The developed technique is a promising prospect that can be applied in the analysis of organic pollutants from complex solid samples.     

A modified method for the analysis of organics in industrial wastewater as directed by their toxicity to Vibrio fischeri

A method for the identification of toxic compounds in industrial wastewater is presented, consisting of sequential solid phase extraction (SPE), fractionation by HPLC and GC-MS for compound identification. All analytical steps are accompanied by an automated detection of the aquatic toxicity by luminescence inhibition of Vibrio fischeri, which helps to reduce the large number of samples and subsamples that have to be processed by exluding those without toxic effects. The advantages of this procedure in comparison to previous methods of toxicity directed water analysis are discussed. The procedure was successfully applied to various samples of tannery wastewater, showing that benzothiazoles account for the major toxicity of tanyard wastewater. For very polar wastewater constituents, such as in beamhouse wastewaters, the use of LC-MS/MS for the final compound identification is suggested. Received: 25 September 1998 / Revised: 20 November 1998 / Accepted: 26 November 1998     

A modified method for the analysis of organics in industrial wastewater as directed by their toxicity to Vibrio fischeri

A method for the identification of toxic compounds in industrial wastewater is presented, consisting of sequential solid phase extraction (SPE), fractionation by HPLC and GC-MS for compound identification. All analytical steps are accompanied by an automated detection of the aquatic toxicity by luminescence inhibition of Vibrio fischeri, which helps to reduce the large number of samples and subsamples that have to be processed by exluding those without toxic effects. The advantages of this procedure in comparison to previous methods of toxicity directed water analysis are discussed. The procedure was successfully applied to various samples of tannery wastewater, showing that benzothiazoles account for the major toxicity of tanyard wastewater. For very polar wastewater constituents, such as in beamhouse wastewaters, the use of LC-MS/MS for the final compound identification is suggested.     

Simultaneous determination of aliphatic and aromatic amines in water and sediment samples by ion-pair extraction and gas chromatography-mass spectrometry

A gas chromatography-mass spectrometry (GC-MS) method has been proposed for the determination of aliphatic and aromatic amines in a variety of environmental samples including wastewater, river water, sea water and sediment samples. The method includes ion-pair extraction with bis-2-ethylhexylphosphate (BEHPA), derivatisation of compounds with isobutyl chloroformate (IBCF) and their GC-MS analysis. Aliphatic and aromatic amines were isolated from aqueous samples using BEHPA as ion-pair reagent and derivatised with IBCF for their chromatographic analysis. Solid-liquid extraction of aliphatic and aromatic amines in sediment samples were performed in Soxhlet apparatus with acidic MeOH and ion-pair extraction with BEHPA were carried out for the isolation of amines followed by derivatisation with IBCF. Aliphatic and aromatic amines were then analysed with GC-MS in both electron impact (EI) and positive and negative ion chemical ionisation (PNICI) mode as their isobutyloxycarbonyl (isoBOC) derivatives. The obtained recoveries ranged from 81.0 to 98.0% and the precision of this method, as indicated by the relative standard deviations (RSDs) was within the range of 0.5 and 4.3%. The detection limits obtained from calculations by using GC-MS results based on S/N = 3 were within the range from 0.07 to 0.50 ng/l.     

Extractive fluorimetric determination of ultratraces of lead with 18-crown-6 and eosin

A highly sensitive and selective spectrofluorimetric procedure for the determination of lead in the range 0.003-0.5 ppm, based on solvent extraction of the ion-pair formed between the eosinate anion and the cationic complex of Pb(2+) with 18-crown-6, has been developed. The relative standard deviation is 3.7% at the 0.1 ppm level. The metal :ligand: counter-ion molecular ratio in the ion-pair extracted is 1:1:1, but aggregation of the complex may occur in the organic phase. The system proposed is exceptionally selective for extraction of lead in the presence of other cations frequently associated with it. The proposed method has been tested in the determination of lead in tap water. The results show good agreement with those found by the more common extractive atomic-absorption method using ammonium tetramethylenedithiocarbamate.     

A post-column extraction system for the determination of tertiary amines by liquid chromatography with chemiluminescence detection

Summary The combination of an ion-pair extraction detection system with peroxyoxalate chemiluminescence detection has been investigated. Ion-pairs of protonated tertiary amines with a chemiluminescent counter ion are on-line post-column extracted to 1,2-dichloroethane containing bis(2,4,6-trichlorophenyl)oxalate (TCPO). Hydrogen peroxide is added to the organic phase by means of a solid-state perhydrit reactor. The influence of the base catalyst (imidazole) on the chemiluminescence reaction in apolar solvents was studied. Some sulfonated chemiluminophores were compared with respect to their chemiluminescence, ion-pairing and extraction properties, and 5-dimethylaminonaphthalene-1-sulfonate was found to be the most suitable reagent. The detection limit of the potential drug secoverine is in the sub-nanogram range.     

阳离子表面活性剂Aliquat 336对水中双酚A的浊点萃取及作用机制

研究了阳离子表面活性剂Aliquat 336(三辛基甲基氯化铵)浊点萃取水中双酚A(BPA)后以高效液相色谱测定的方法.探讨了Aliquat 336与Na_2SO_4/NaCl用量、pH值、萃取时间等因素对萃取效果的影响,经条件实验选定各因素水平如下:0.8 g/L Aliquat 336,4.0 g/L Na_2SO_4,超声萃取15 min,pH和对萃取影响不大,故不予调节.结果表明: 在此选定条件下,本方法富集效率高(BPA在胶束相-水相分配系数达10~4),萃取效率稳定(相对标准偏差均小于10%),其对BPA在不同水质、不同加标浓度下的回收率均大于90%,去离子水中检出限为0.34 μg/L.本方法操作简单、方便、成本低,易于推广.同时以胶束粒径与Zeta电位分析等确证盐含量对阳离子表面活性剂胶束形成的决定性作用,并结合影响因子分析,推测Aliquat 336浊点萃取过程中BPA可能存在静电作用、阳离子-π键等疏水分配以外的作用机制.     

Ion-pair extraction of some cinchona alkaloids with various chiral organic anions

Some cinchona alkaloids, the quinine/quinidine and cinchonine/cinchonidine pairs, are extracted by ion-pair formation with some chiral amino acids and d-camphorsulfonic acid. Their extraction behaviors are examined and the differences between the two isomers are compared. These alkaloids are extracted into chloroform in the pH range 4–7 as the 1:1 ion-pair with the organic acid. The relationship between the distribution ratio of the ion-pair and pH is discussed. In the pH range between the pK_a1 and pK_a2 values of these alkaloids, logarithmic plots of the distribution ratio are independent of pH. In this pH region, the extraction constants are determined and the differences caused by the ion-pair formation are discussed.     

Determination of metal complexes of ethylenediaminetetraacetate in the presence of organic matter by high-performance liquid chromatography

A high-performance liquid chromatography method is described here for the determination of the Cd(II), Co(II), Cu(II), Pb(II), and Zn(II) complexes of ethylenediaminetetraacetate (EDTA) in municipal wastewaters and surface waters. The method involves separation by ion-exchange chromatography on a reversed-phase C18 column coated with ion-pair reagent, followed by post-column conversion to FeEDTA and subsequent detection by UV absorbance. Although Co(II) and Cu(II) coelute, they can be quantified by analyzing absorbance by CuEDTA2- prior to post-column conversion. The method detection limit of 6-8 x 10(-8) M (5-7 ng) is an order of magnitude improvement over previous UV absorbance post-column reaction methods. The technique can be used in the presence of organic matter encountered in matrices such as untreated wastewater without pre-concentration or sample cleanup.