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Analytical and Bioanalytical Chemistry (v.377, #7-8)
Always learning: continuing education for industrial chemists (and others, too!)
by John Fetzer (pp. 1087-1088).
Book review: Guidelines for Achieving High Accuracy in Isotope Dilution Mass Spectrometry (IDMS)
(pp. 1091-1092).
FT/ICR–mass spectrometry in nanotechnology: the investigation of metalloid clusters by Katharina Weiß; Hansgeorg Schnöckel (pp. 1098-1101).
The particularity of metalloid clusters as a special kind of metal atom cluster is described. For the first time such metalloid clusters are investigated in the gas phase by means of FT/ICR–mass spectrometry, the results of which show that metalloid clusters represent a bridge between the bulk metal and metal compounds that can be found in solution after oxidation of the bulk metal. The metalloid clusters presented herein are [Ga19R6]− (R=C(SiMe3)3), and SiAl14Cp*6 and the precursor Al4Cp*4 (Cp*=η 5-C5Me5).
Keywords: FT/ICR–mass spectrometry; Gas-phase reactions; Metalloid clusters; SORI–CAD (sustained off resonance irradiation–collision-activated dissociation)
Detection of protease activities with the mass-spectrometry-assisted enzyme-screening (MES) system by Hartmut Schlüter; Joachim Jankowski; Jana Rykl; Joachim Thiemann; Swetlana Belgardt; Walter Zidek; Brigitte Wittmann; Thomas Pohl (pp. 1102-1107).
The MALDI-MES provides a rapid, sensitive and reproducible alternative approach to existing analytical techniques for the detection of enzymatic activities that does not require a chromophore or radiolabeling. An improved method is presented, by which enzymes with defined substrate specificities can be detected with a MALDI mass spectrometer in complex protein fractions. In order to demonstrate the utility of the new method, in this study we describe the use of MALDI-MES to detect proteolytic activities in a protein extract from porcine renal tissue, which contained several thousand proteins as visualized by 2D electrophoresis. The analytical procedure is based on covalent immobilization of proteins to beads. By immobilizing proteins, autolytic and proteolytic degradation is prevented and the removal of those molecules from the protein fraction is achieved, which otherwise would interfere with the mass spectrometric detection of the enzymatic reaction products. The enzymatic activity is determined by incubating the immobilized proteins with a reaction-specific probe, followed by the analysis of the reaction mixture with the MALDI-MS after defined incubation times. The presence of the target enzyme is validated by locating a signal, which fits the molecular mass of the expected reaction product in the mass spectrum. To demonstrate how to detect proteolytic activities in this system, the reactions catalyzed by endopeptidase, angiotensin-converting enzyme, kallikrein, renin, and urotensin-converting enzyme were monitored. The experiments showed that the MALDI-MES method is sufficient according the quantification to investigate the effects of inhibitors. This is demonstrated using a specific renin inhibitor to inhibit an angiotensin-I generating enzyme activity in a renal protein extract.
Keywords: MALDI-MS; Enzyme assay; Protease activity; Angiotensin-converting enzyme; Kallikrein; Renin; Urotensin-converting enzyme
Use of electrospray ionization mass spectrometry for the investigation of radical cation chain reactions in solution: detection of transient radical cations by Sven Meyer; Jürgen O. Metzger (pp. 1108-1114).
Electrospray ionization mass spectrometry (ESI-MS) coupled to a microreactor is an excellent tool for the investigation of reactions in solution. Here, we report the first results of our investigations into preparatively interesting electron-transfer-initiated chain reactions in solution which proceed via radical cations as reactive intermediates. The tris(p-bromophenyl)aminium hexachloroantimonate (1)-mediated [2+2] cycloaddition of trans-anethole (2) to give 1,2-bis(4-methoxyphenyl)-3,4-dimethylcyclobutane (3) was investigated. The reaction proceeds as a radical cation chain reaction via transient intermediates 2 ●+ and 3 ●+ that could be detected and characterized unambiguously directly in the reacting solution by ESI-MS/MS. The identity of the intermediates was confirmed by comparison with authentic MS/MS spectra of 2 ●+ and 3 ●+ obtained by atmospheric pressure chemical ionization mass spectrometry (APCI-MS). In addition, substrate and product can be monitored easily in the reacting solution by APCI-MS.
Keywords: Cycloaddition; Mass spectrometry; Microreactor; Radical cation; Reactive intermediate
Dissociative electron attachment to gas-phase glycine by S. Ptasinska; S. Denifl; A. Abedi; P. Scheier; T. D. Märk (pp. 1115-1119).
By using a high-resolution electron energy monochromator low-energy electron attachment to gas-phase glycine (H2NCH2COOH, or G) has been studied by means of mass spectrometric detection of the product anions. In the same way as for several other biologically relevant molecules no stable parent anion was formed by free electron attachment. The largest dissociative electron attachment (DEA) cross-section, approximately 5×10−20 m2, was observed for (G−H)–+H at an electron energy of 1.25 eV. Glycine and formic acid (HCOOH) have several common features, because a precursor ion can be characterized by electron attachment to the unoccupied π* orbital of the –COOH group. At higher incident electron energies several smaller fragment anions are formed. Except for H–, which could not be observed in this study, there was good agreement with an earlier investigation by Gohlke et al.
Keywords: Glycine; Negative fragment ion; Free-electron attachment
Feasibility study: fast liquid chromatography–mass spectrometry for the quantification of aspartic acid in an aspartate drug by Jochen Schmidt (pp. 1120-1123).
We have studied the feasibility of fast high-performance liquid chromatography coupled to electrospray ionization mass spectrometry in the selected ion monitoring mode for the quantitative determination of aspartic acid in an aspartate drug. Internal standardization was required, but mass spectrometric detection allowed for very short retention times of approximately 0.5 min for the analyte and the internal standard without chromatographic separation. The analytical system was found stable, as demonstrated by multiple injections giving a coefficient of variation of 4% for the peak area ratio of aspartic acid and glutamic acid. Calibrations were linear between 0.5 ng and 150 ng aspartic acid injected, with accuracies between 99.8% and 102% found for the back-calculated amounts. Investigation of several drug batches gave reasonable results. Therefore, the method appeared feasible for the determination of aspartic acid in an aspartate drug from 0.3 wt% to 100 wt% aspartic acid.
Keywords: Quantification; Aspartic acid; Aspartate drug; Fast HPLC-MS; Electrospray ionization; Selected ion monitoring
Rapid analysis of aromatic contaminants in water samples by means of laser ionization mass spectrometry by Daniel Globig; Christian Weickhardt (pp. 1124-1132).
Three different approaches to laser ionization mass spectrometric analysis of aromatic compounds in water samples are described and their performances are compared. Whereas the first two methods are based on direct laser desorption and subsequent laser ionization of either frozen or adsorbed samples in a time-of-flight mass analyzer, the third performs laser ionization in a quadrupole ion-trap into which the sample is transferred from a GC injector via a short piece of capillary tubing. For the laser-desorption method a detection limit in the 100 µg L−1 range was determined for fluorene in frozen samples. The easier to handle analysis of adsorbed samples yielded sensitivities which were lower by about two orders of magnitude. As both direct techniques do not reach the sensitivity required for ultra trace analysis in water a preconcentration step in form of solid-phase microextraction was added before measurement using the laser ionization quadrupole ion-trap mass spectrometer. Sensitivity in the desired ng L−1 range was easily achieved.
Keywords: Laser ionization; Mass spectrometry; Rapid water analysis; Aromatic contaminants
Cluster calibration in mass spectrometry: laser desorption/ionization studies of atomic clusters and an application in precision mass spectrometry by K. Blaum; A. Herlert; G. Huber; H.-J. Kluge; J. Maul; L. Schweikhard (pp. 1133-1139).
For accurate mass measurements and identification of atomic and molecular species precise mass calibration is mandatory. Recent studies with laser desorption/ionization and time-of-flight analysis of cluster ion production by use of fullerene and gold targets demonstrate the generation of atomic clusters for calibration purposes. Atomic ion results from the Penning trap mass spectrometer ISOLTRAP, in which a carbon cluster ion source has recently been installed, are presented as an application in the field of precision mass spectrometry.
Keywords: Atomic masses; Carbon clusters; Cluster calibration; Fullerenes; Gold clusters; Laser desorption/ionization; MALDI–TOF; Mass spectra; Mass spectrometry
Interlaboratory comparison study for the determination of methyl tert-butyl ether in water by Rainer Schuhmacher; Manuela Führer; Wolfgang Kandler; Caroline Stadlmann; Rudolf Krska (pp. 1140-1147).
This is the first publication which describes the evaluation of the analytical performance and state-of-the-art of the determination of methyl tert-butyl ether (MTBE) in water at ng L−1 concentrations. An interlaboratory comparison study for the determination of MTBE in water was carried out. Twenty-eight laboratories from seven European countries participated in the study. Twenty of those finally transmitted results to the organiser. Italian spring water, containing no detectable amounts of MTBE was fortified to yield two samples with MTBE concentrations of 0.074±0.004 µg L−1 and 0.256±0.010 µg L−1. The laboratories applied their regular in-house methods to analyse the water samples. Static headspace, Purge & Trap, solid-phase microextraction (SPME) or direct aqueous injection were used as sample preparation techniques. Subsequent separation and detection of MTBE were performed by gas chromatography/mass spectrometry (GC/MS) or gas chromatography/flame ionisation detection (GC/FID). After rejection of outliers, the overall arithmetic mean of laboratory results corresponded to recoveries of 78±20% (Sample A) and 88±20% (Sample B) of the reference concentrations. The between laboratory coefficients of variation (CV) were 32% and 31%, respectively. The organisation of the study and quality assurance measures at the organiser's laboratory are described. Moreover, the measurement results of the participants and the analytical methods used for the determination of MTBE are presented and the correlation between selected method parameters and data quality is discussed.
Keywords: MTBE; Water analysis; Quality assurance; Analytical methods
A multi-residue method for characterization and determination of atmospheric pesticides measured at two French urban and rural sampling sites by Laurent Baraud; Didier Tessier; Jean-Jacques Aaron; Jean-Paul Quisefit; Johann Pinart (pp. 1148-1152).
The extensive use of pesticides to protect agricultural crops can result in the transfer of these compounds into the atmosphere and their diffusion towards urban areas. Precise evaluation of the geographic impact of this type of pollution is important environmentally. In this paper, analytical methods for the sampling, characterization, and determination of agricultural pesticides in air were developed; the methods were then applied in the Paris and Champagne regions. Sixteen pesticides belonging to nine chemical families were monitored. Sampling was carried out in urban (Paris) and rural (Aube district) sites, utilizing either a high-volume pump (12.5 m3 h−1) (urban site) or a low-volume pump (2.3 m3 h−1) for the rural site. Quartz filters and polyurethane foams (PUF) were used for sampling in all cases. After extracting the samples and concentrating the recovered solutions, high-performance liquid chromatography (HPLC) analysis with UV detection was performed. Identification of the pesticides was confirmed by applying to the HPLC measurements a novel UV-detection procedure based on the normalized absorbance variation with wavelength (Noravawa procedure). The presence of metsulfuron methyl, isoproturon, linuron, deltamethrin (and/or malathion), and chlorophenoxy acids (2,4-D and MCPP) was found at the urban sampling site at levels ranging from about 1 to 1130 ng m−3 of air, depending on the compound and sampling period. On the rural sampling site residues of isoproturon, deltamethrin (and/or malathion), MCPP, and 2,4-D were generally detected at higher levels (19–5130 ng m−3) than on the urban site, as expected. The effects of the weather conditions and agricultural activity on the atmospheric concentrations of pesticides are discussed, as are long-range atmospheric transfer processes for these pesticides.
Keywords: Pesticides; Atmosphere; Air sampling; Soxhlet extraction; HPLC analysis
Genetic algorithms based on wavelet transform for resolving simulated overlapped spectra by Xiuqi Zhang; Jiye Jin; Jianbin Zheng; Hong Gao (pp. 1153-1158).
Wavelet transform-based genetic algorithms are proposed for resolving simulated overlapped spectra. Wavelet transform as a derivative method is used for de-noising, for deducting background absorption as well as for peak finding in order to get an estimation of parameters of unresolved spectra. Then genetic algorithms, using the estimations of parameters as input values, are employed to resolve unresolved bands. As a consequence, a good optimized solution was achieved since the reliable estimation of initial values can greatly facilitate the convergence of genetic algorithms and the calculation time is shortened accordingly.
Keywords: Resolving overlapped spectra; Genetic algorithms; Wavelet transform; Genetic algorithms based on wavelet transform
Chemometrics-assisted simultaneous determination of atenolol and chlorthalidone in synthetic binary mixtures and pharmaceutical dosage forms by Mónica C. F. Ferraro; Patricia M. Castellano; Teodoro S. Kaufman (pp. 1159-1164).
Resolution of binary mixtures of atenolol (ATE) and chlorthalidone (CTD) with minimum sample pre-treatment and without analyte separation has been successfully achieved, using a new and rapid method based on partial least squares (PLS1) analysis of UV spectral data. The simultaneous determination of both analytes was possible by PLS1 processing of sample absorbances between 255 and 300 nm for ATE and evaluation of absorbances in the 253–268 nm region for CTD. The mean recoveries for synthetic samples were 100.3±1.0% and 100.7±0.7% for ATE and CTD, respectively. Application of the proposed method to two commercial tablet preparations in the content uniformity test showed them to contain 103.5±0.8% and 104.9±1.8% ATE respectively, as well as 103.4±1.2% and 104.5±2.2% CTD. Use of this method also allowed the elaboration of dissolution profiles of the drugs in two commercial combined formulation products, through the simultaneous determination of both drugs during the dissolution test. At the dissolution time of 45 min specified by USP XXIV, both pharmaceutical formulations complied with the test.
Keywords: Atenolol; Chlorthalidone; PLS1; Dissolution; Chemometric method
Direct solid analysis of powdered tungsten carbide hardmetal precursors by laser-induced argon spark ablation with inductively coupled plasma atomic emission spectrometry by Markéta Holá; Viktor Kanický; Jean-Michel Mermet; Vítězslav Otruba (pp. 1165-1174).
The potential of the laser-induced argon spark atomizer (LINA-Spark atomizer) coupled with ICP-AES as a convenient device for direct analysis of WC/Co powdered precursors of sintered hardmetals was studied. The samples were presented for the ablation as pressed pellets prepared by mixing with powdered silver binder containing GeO2 as internal standard. The pellets were ablated with the aid of a Q-switched Nd:YAG laser (1064 nm) focused 16 mm behind the target surface with a resulting estimated power density of 5 GW cm−2. Laser ablation ICP-AES signals were studied as a function of ablation time, and the duration of time prior to measurement (pre-ablation time) which was necessary to obtain reliable results was about 40 s. Linear calibration plots were obtained up to 10% (m/m) Ti, 9% Ta and 3.5% Nb both without internal standardization and by using germanium as an added internal standard or tungsten as a contained internal standard. The relative uncertainty at the centroid of the calibration line was in the range from ±6% to ±11% for Nb, Ta and Ti both with and without internal standardisation by Ge. A higher spread of points about the regression was observed for cobalt for which the relative uncertainty at the centroid was in the range from ±9% to ±14%. Repeatability of results was improved by the use of both Ge and W internal standards. The lowest determinable quantities calculated for calibration plots were 0.060% Co, 0.010% Nb, 0.16% Ta and 0.030% Ti with internal standardization by Ge. The LA-ICP-AES analyses of real samples led to good agreement with the results obtained by solution-based ICP determination with a relative bias not exceeding 10%. The elimination of the dissolution procedure of powdered tungsten (Nb, Ta, Ti) carbide is the principal advantage of the developed LA-ICP-AES method.
Keywords: Infrared laser ablation; Inductively coupled plasma; Atomic emission spectrometry; Tungsten carbide
A study of low level selenium determination by hydride generation atomic fluorescence spectrometry in water soluble protein and peptide fractions by V. Stibilj; D. Mazej; I. Falnoga (pp. 1175-1183).
Development of a method for very low level selenium determination in water soluble protein and peptide fractions, obtained after various separation procedures, is presented. A hydride generation atomic fluorescence spectrometry (HG-AFS) detection system was optimised and the influence of Cu(II), Sb(V), As(III) and HNO3 interferences in the measurement of Se by HG-AFS was investigated. A destruction procedure using HNO3 and H2O2 was also optimised and the average recovery of the digestion of a solution of selenomethioneine was 92 ± 4% (n=14). Combination of this digestion with the detection system gave reliable results. Accuracy was tested by comparison with two independent methods. A very low detection limit (DL) of 0.2 ng/g of measuring solution was achieved. The whole procedure from weighing to measuring was performed in the same Teflon tube. The addition of HNO3 to the fractions before long term storage at -20°C was necessary to prevent adsorption on the test tubes.Selenium was measured in water soluble protein and peptide fractions obtained after extraction, and Sephadex G-75 chromatography performed on liver samples from: i) hens exposed to As2O3, ii) hens fed with a high fat feed and iii) the certified reference material dogfish liver (CRM DOLT-2). Because of the very low DL we were able to observe the Se distribution in chromatographic fractions of samples of organisms which were not exposed to excess amounts of Se. The presence of selenium associated with metallothioneins was observed.
Keywords: Selenium; HG-AFS; Liver; Size exclusion chromatography; Metallothioneins
Rapid determination of telmisartan in pharmaceuticals and serum by the parallel catalytic hydrogen wave method by Maotian T. Xu; Junfeng F. Song; Ning Li (pp. 1184-1189).
The polarographic characteristics of telmisartan have been investigated in 0.8 mol L−1 NH3.H2O–NH4Cl (pH 8.9)–0.01 mol L−1 H2O2 as supporting electrolyte. The results demonstrate that the polarographic reduction wave at ca. −1.30 V in the absence of H2O2 is a catalytic hydrogen wave, and the reduction wave enhanced by H2O2 is a so-called parallel catalytic hydrogen wave. The analytical sensitivity of the parallel catalytic hydrogen wave is ca. 60 times higher than that of the corresponding catalytic hydrogen wave. Based on the parallel catalytic hydrogen wave a novel method has been developed for determination of telmisartan by linear sweep polarography. The calibration curve is linear in the range 2.0×10−8–2.0×10−6 mol L−1 and the detection limit is 1.0×10−8 mol L−1. The precision is excellent with relative standard deviations of 2.6% at a concentration of 1.0×10−7 mol L−1 telmisartan. The proposed method has been applied to the direct determination of the telmisartan in capsule forms and biological samples. The proposed method has been proved to be advantageous over existing CZE and MEKC methods in simplicity, rapidity, and reproducibility.
Keywords: Telmisartan; H2O2 ; Parallel catalytic hydrogen wave; Catalytic hydrogen wave; Linear sweep polarography; Pharmaceutical analysis
Superheated liquids for extraction of solid residues from winemaking processes by J. González-Rodríguez; P. Pérez-Juan; M. D. Luque de Castro (pp. 1190-1195).
Solid residues from winemaking processes have been subjected to extraction with superheated water–ethanol mixtures. Identification and characterization of the extracted compounds were achieved by spectrophotometry, gas chromatography with either flame-ionization or mass detectors, and-high performance liquid chromatography with UV detection. Extraction was performed statically with single or repeated cycles. All variables affecting the extraction process have been studied and optimised. The extraction time and temperature were 65 min and 210 °C, respectively. Extracts comprised two phases—an aqueous phase, rich in phenolic compounds, and an oily phase, comprising mainly fatty acids. The method allows manipulation of extract composition by changing the applied pressure, temperature, water-to-ethanol ratio, and pH. The method is faster than traditional extraction procedures for obtaining valuable compounds from these residues.
Keywords: Solid-liquid extraction; Liquid chromatography; Gas chromatography; Mass spectrometry; Superheated liquids; Winemaking residues
Influence of chloride and sediment matrix on the extractability of HgS (cinnabar and metacinnabar) by nitric acid by Nevenka Mikac; Delphine Foucher; Sylvie Niessen; Sonja Lojen; Jean-Claude Fischer (pp. 1196-1201).
The extractability of metacinnabar and cinnabar, alone or in the presence of some sediment components, with various concentrations of HNO3 (1, 4, 6, and 14 M) was studied. Both forms of HgS (0.2–0.3 mg HgS in 10–20 mL of acid) were insoluble in all HNO3 concentrations as pure compounds. The presence of FeCl3 enhanced solubility of both cinnabar and metacinnabar, especially when concentrated HNO3 was used for the extraction. As the same effect was not obtained in the presence of FeOOH, we concluded that chloride and not Fe3+ was responsible for HgS dissolution. In fact, addition of very low chloride concentration to concentrated HNO3 provoked partial (Cl>10−4 M) or even total dissolution (Cl>10−2 M) of HgS. In dilute HNO3 (4–6 M) cinnabar was much less affected by chloride addition than metacinnabar. Extraction of HgS by concentrated HNO3 in the presence of sediment of various salinities demonstrated that the amount of dissolved HgS increased with the increase of the sediment salinity (from freshwater to estuarine and marine sediment), confirming that chloride enhances dissolution of HgS. Removal of chloride by washing the sediment with Milli-Q water significantly reduced dissolution of added HgS during extraction by concentrated HNO3. These results demonstrate that conclusions based on the extraction schemes using concentrated HNO3 as single extractant or as the first extractant in the sequential extraction procedures can be biased. A verification of artifactual oxidation of HgS, when using more concentrated HNO3 as extractant, would help to verify reliability of the applied extraction procedure.
Keywords: Extraction; Cinnabar; Nitric acid; Mercury; Sediment
Comparison of different fluorimetric HPLC methods for analysis of acidic polyether toxins in marine phytoplankton by M. J. Nogueiras; Ana Gago-Martínez; Antonio I. Paniello; Marian Twohig; Kevin J. James; James F. Lawrence (pp. 1202-1206).
The human toxic syndrome, diarrhetic shellfish poisoning (DSP), is caused by polyether toxins that are present in bivalve molluscs but originate from some species of marine phytoplankton. During the last few years different HPLC methods with fluorescence detection (FLD) have been proposed for analysis of marine toxins, including polyether toxins, in shellfish and phytoplankton. Several derivatization reagents have been proposed in the literature, with the aim of converting the acidic DSP toxins into their corresponding fluorescent derivatives. In this work we report results obtained from HPLC–FLD analysis of extracts from phytoplankton, including Dinophysis spp., harvested off the south-west coast of Ireland. Three different reagents were used for fluorescent derivatization: 3-bromomethyl-6,7-dimethoxy-1-methyl-2(1H)-quinoxalinone (BrDMEQ), 9-chloromethylanthracene (CA), and “in situ” 9-anthracenyldiazomethane (ADAM). Derivatization was performed under conditions previously optimised. The DSP derivatives were cleaned using different SPE procedures then analysed by HPLC–FLD. In this study, the use of BrDMEQ, CA, and “in situ” ADAM was compared in terms of sensitivity and selectivity. Evaluation of HPLC methods for analysis of DSP toxin derivatives was also conducted; the presence of okadaic acid (OA), dinophysistoxin-2 (DTX-2), and pectenotoxin-2 seco acids (PTX1SAs) was detected in the sample extracts studied.
Keywords: Diarrhetic shellfish poisoning toxins; 9-Anthryldiazomethane; 3-Bromomethyl-6,7-dimethoxy-1-methyl-2(1H)-quinoxalinone; 9-Chloromethylanthracene
Direct determination of bromide ions in seawater by capillary zone electrophoresis using polyethyleneimine-coated capillaries by Nilgün Kocatürk; Nevin Öztekin; F. Bedia Erim (pp. 1207-1211).
A rapid and simple capillary electrophoretic method was developed for the direct determination of bromide ion in seawater. We have found an effective method, based on the use of polyethyleneimine-coated capillaries and the addition of sodium chloride to the background electrolyte. The use of coated capillaries with a cationic polymer changes the direction of the electroosmotic flow in the capillary, which favors the migration speed of the bromide ion and enables the use of low salt concentrations in the separation electrolyte. Bromide ion in seawater can be determined within 2 min using this system and 20 mmol L-1 NaCl-containing separation electrolyte. The detection limit for the bromide ion was 0.45 μg ml-1. The method was applied to the determination of bromide ion in seawater samples collected from the Bosphorus and the Black Sea. Bromide contents in samples from 0 to 72 m depths varied between 33.2 and 72.8 mg L-1 with a mean 3.0% RSD.
Keywords: Capillary electrophoresis; Seawater; Bromide
Flow injection chemiluminescence determination of l-cysteine in amino acid mixture and human urine with the BrO3 −–quinine system by Baoxin Li; Zhujun Zhang; Meilin Liu; Chunli Xu (pp. 1212-1216).
In this paper, a novel flow injection chemiluminescence (CL) determination of l-cysteine is proposed. The method is based on the CL reaction of l-cysteine and KBrO3 in acidic medium. The CL intensity was greatly enhanced in the presence of quinine. The CL intensity was linear with l-cysteine concentration in the range of 0.2–80 μg L−1, and the detection limit was 0.1 μg L−1 (3σ). A complete analysis, including sampling and injecting, could be performed in 1 min, giving a throughput of about 60 h−1. The relative standard deviation was 1.6% for 0.8 μg L−1 l-cysteine (n=11). The proposed method was satisfactorily applied to the determination of cysteine in an amino acid mixture and human urine. The mechanism of the CL reaction is also discussed.
Keywords: Chemiluminescence; Flow injection analysis; l-Cysteine; BrO3 −–quinine