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Analytica Chimica Acta (v.610, #2)

Contents (pp. iii-iv).

Outside front cover - Editorial Board (pp. co1).

Editorial Board (pp. i).

Passive sampling of ambient ozone by solid phase microextraction with on-fiber derivatization by I-Su Lee; Shih-Wei Tsai (pp. 149-155).

The solid phase microextraction (SPME) device with the polydimethylsiloxane/divinylbenzene (PDMS/DVB) fiber was used as a passive sampler for ambient ozone. Both O-2,3,4,5,6-(pentafluorobenzyl)hydroxylamine hydrochloride (PFBHA) and 1,2-di-(4-pyridyl)ethylene (DPE) were loaded onto the fiber before sampling. The SPME fiber assembly was then inserted into a PTFE tubing as a passive sampler. Known concentrations of ozone around the ambient ground level were generated by a calibrated ozone generator. Laboratory validations of the SPME passive sampler with the direct-reading ozone monitor were performed side-by-side in an exposure chamber at 25°C. After exposures, pyriden-4-aldehyde was formed due to the reaction between DPE and ozone. Further on-fiber derivatizations between pyriden-4-aldehyde and PFBHA were followed and the derivatives, oximes, were then determined by portable gas chromatography with electron capture detector. The experimental sampling rate of the SPME ozone passive sampler was found to be 1.10×10⁻⁴cm³s⁻¹ with detection limit of 58.8μgm⁻³h⁻¹. Field validations with both SPME device and the direct-reading ozone monitor were also performed. The correlations between the results from both methods were found to be consistent with r=0.9837. Compared with other methods, the current designed sampler provides a convenient and sensitive tool for the exposure assessments of ozone.

Keywords: Ozone; 1,2-Di-(4-pyridyl)ethylene; O; -2,3,4,5,6-(pentafluorobenzyl)hydroxylamine hydrochloride; Solid phase microextraction; Passive sampler

Analytical methods for the determination of emerging organic contaminants in the atmosphere by Zhiyong Xie; Ralf Ebinghaus (pp. 156-178).

Concerns over the occurrence and transport of emerging organic contaminants (EOCs) from local sources to remote regions have resulted in wide developments in sampling strategy and analytical methodology for the determination of trace concentrations of EOCs in the atmosphere. This article discusses developments in the determination of EOCs in ambient air which includes polyfluorinated alkyl substances (PFASs), brominated-flame retardants (BFRs), synthesis musk fragrances, and alkylphenols (APs). References were mainly summarized from the past 5 years (2002 up to present) on new developments of sampling methods, extraction, separation/fractionation and/or applications of new technologies for sampling and determination.

Keywords: Emerging organic contaminants; Environmental analysis; Atmosphere; Review

Separate vaporisation of boric acid and inorganic boron from tungsten sample cuvette–tungsten boat furnace followed by the detection of boron species by inductively coupled plasma mass spectrometry and atomic emission spectrometry (ICP-MS and ICP-AES) by Hiroko Kataoka; Yasuaki Okamoto; Satoshi Tsukahara; Terufumi Fujiwara; Kazuaki Ito (pp. 179-185).

Utilising extremely different vaporisation properties of boron compounds, the determination procedures of volatile boric acid and total boron using tungsten boat furnace (TBF) ICP-MS and TBF-ICP-AES have been investigated. For the determination of volatile boric acid by TBF-ICP-MS, tetramethylammonium hydroxide (TMAH, Me₄NOH) was used as a chemical modifier to retain it during drying and ashing stages. As for the total boron, not only non-volatile inorganic boron such as boron nitride (BN), boron carbide (B₄C), etc. but also boric acid (B(OH)₃) was decomposed by a furnace-fusion digestion with NaOH to produce sodium salt of boron, a suitable species for the electrothermal vaporisation (ETV) procedure. The proposed method was applied to the analysis of various standard reference materials. The analytical results for various biological and steel samples are described.

Keywords: Electrothermal vaporisation inductively coupled plasma mass spectrometry; Electrothermal vaporisation inductively coupled plasma atomic emission spectrometry; Boron determination; Steel sample; Botanical sample

Three-way partial least-squares/residual bilinearization study of second-order lanthanide-sensitized luminescence excitation-time decay data by Valeria A. Lozano; Gabriela A. Ibañez; Alejandro C. Olivieri (pp. 186-195).

Lanthanide-sensitized luminescence excitation-time decay matrices were employed for achieving the second-order advantage using as chemometric algorithms parallel factor analysis (PARAFAC) and multidimensional partial least-squares with residual bilinearization (N-PLS/RBL). The second-order data were measured for a calibration set of samples containing the analyte benzoic acid in the concentration range from 0.00 to 5.00mgL⁻¹, for a validation set containing the analyte and the potential interferent saccharin (in the range 0.00–6.00mgL⁻¹), and for real samples of beverages containing benzoic acid as preservant, saccharin, and other potentially interfering compounds. All samples were treated with terbium(III), trioctylphosphine oxide as a synergistic ligand, and contained a suitable imidazol buffer, in order to ensure maximum intensity of the luminescence signals. The results indicate a slightly better predictive ability of the newly introduced N-PLS/RBL procedure over standard PARAFAC, both in what concerns the comparison with nominal analyte concentrations in the validation sample set and with results provided by the reference high-performance liquid chromatographic technique for the real sample set.

Keywords: Lanthanide-sensitized luminescence; Excitation-time decay matrices; Parallel factor analysis; Multidimensional partial least-squares; Residual bilinearization; Benzoic acid determination

Comparison of calibrations for the determination of soluble solids content and pH of rice vinegars using visible and short-wave near infrared spectroscopy by Fei Liu; Yong He; Li Wang (pp. 196-204).

Visible and short-wave near infrared (Vis/SWNIR) spectroscopy combined with chemometrics was investigated for the fast determination of soluble solids content (SSC) and pH values of rice vinegars. Two hundred and twenty-five samples (45 for each variety) were selected randomly for the calibration set, whereas, 75 samples (15 for each variety) for the validation set, and the remaining 25 samples for the independent set. After some preprocessing, partial least squares (PLS) analysis was implemented for calibration models with different wavelength bands including visible, SWNIR and Vis/SWNIR regions. The best PLS models were achieved with Vis/SWNIR (550–1000nm) region. Furthermore, different latent variables (5, 6, 7, 8 LVs) were used as inputs of least squares-support vector machine (LS-SVM) to develop the LV-LS-SVM models with grid search technique and RBF kernel. The optimal models were obtained with 6 LVs and they outperformed PLS models. Moreover, effective wavelengths (EWs) were selected according to regression coefficients. The EW-LS-SVM models were developed and an excellent prediction precision was achieved, and the effectiveness of the EWs was also validated. The correlation coefficient ( r), root mean square error of prediction (RMSEP) and bias for the best prediction by EW-LS-SVM were 0.999, 0.189 and 0.051 for SSC, whereas 0.999, 0.008 and −1.7×10⁻³ for pH, respectively. The overall results indicated that Vis/SWNIR spectroscopy combined with LS-SVM could be applied as a high precision and fast way for the determination of SSC and pH values of rice vinegars.

Keywords: Visible and short-wave near infrared spectroscopy; Soluble solids content and pH; Rice vinegar; Effective wavelength; Partial least squares; Least squares-support vector machine

An improved bonded-polydimethylsiloxane solid-phase microextraction fiber obtained by a sol–gel/silica particle blend by Manuel Azenha; Pedro Nogueira; A. Fernando-Silva (pp. 205-210).

A novel procedure for solid-phase microextraction fiber preparation is presented, which combines the use of a rigid titanium alloy wire as a substrate with a blend of PDMS sol–gel mixture/silica particles, as a way of increasing both the mechanical robustness and the extracting capability of the sol–gel fibers. The ∼30μm average thick fibers displayed an improvement in the extraction capacity as compared to the previous sol–gel PDMS fibers, due to a greater load of stable covalently bonded sol–gel PDMS. The observed extraction capacity was comparable to that of 100μm non-bonded PDMS fiber, having in this case the advantages of the superior robustness and stability conferred, respectively, by the unbreakable substrate and the sol–gel intrinsic characteristics. Repeatability ( n=3) ranged 1–8% while fiber production reproducibility ( n=3) ranged 15–25%. The presence of the silica particles was found to have no direct influence on the kinetics and mechanism of the extraction process, thus being possible to consider the new procedure as a refinement of the previous ones. The applicability potential of the devised fiber was illustrated with the analysis of gasoline under the context of arson samples.

Keywords: Solid-phase microextraction; Sol–gel; Polydimethylsiloxane (PDMS); Porous silica; Titanium alloy

Modified solvent microextraction with back extraction combined with liquid chromatography-fluorescence detection for the determination of citalopram in human plasma by Habib Bagheri; Faezeh Khalilian; Esmaeil Babanezhad; Ali Es-haghi; Mohammad-Reza Rouini (pp. 211-216).

A modified solvent microextraction with back extraction method (SME/BE) combined with high performance liquid chromatography and fluorescence detection (HPLC-FD) was developed for the determination of citalopram in human plasma. Extraction process was performed in a home-made total glass vial without using a teflon ring, usually employed in SME/BE. Citalopram was first extracted from 0.5mL of plasma, modified with sodium hydroxide, into hexane. Back extraction step was then performed into 5.2μL of 45mM ammonium formate solution (pH 4) using a GC microsyringe. The extract was subsequently transferred into a liner-like vial and then injected into the HPLC system. An enrichment factor of 150 along with a good sample clean-up was obtained. The calibration curve showed linearity in the range of 1.0–130.0ngmL⁻¹ with regression coefficient corresponding to 0.992. This range covers therapeutic window and even lower amounts which is important in pharmacokinetic studies. Limits of detection and quantification, based on a signal to noise ratio (S/N) of 3 and 10, were 0.3 and 0.8ngmL⁻¹, respectively. The method was also applied for the determination of citalopram in plasma samples after oral administration of 40mg single dose of citalopram.

Keywords: Modified solvent microextraction with back extraction; High performance liquid chromatography-fluorescence detection; Citalopram; Human plasma

Determination of total flavonoids in Scutellaria barbata D. Don by dynamic ultrasonic extraction coupled with on-line spectrophotometry by Xiuli Hu; Jingyan You; Changli Bao; Huarong Zhang; Xiangzhe Meng; Tingting Xiao; Kun Zhang; Yutang Wang; Huimin Wang; Hanqi Zhang; Aimin Yu (pp. 217-223).

A dynamic ultrasonic extraction (DUE) coupled with on-line detection by spectrophotometry is proposed for the determination of total flavonoids (calculated against scutellarin) in Scutellaria barbata D. Don. The extraction was performed in a common self-made extraction vessel put in an ultrasonic bath and a peristaltic pump was used to deliver the extraction solvent. Several experimental parameters of DUE, including flow rate and concentration of extraction solvent, ultrasonic power and sample amount, were optimized. In this work an on-line method was provided with the advantages of minimum sample amount (5mg), on-line monitoring the extraction process and time saving (12.5min). Compared with off-line method, the proposed method would be more convenient for obtaining continuous measurements and rapid optimization of the extraction process.

Keywords: Dynamic ultrasonic-assisted extraction; Spectrophotometry; On-line detection; Scutellarin

Simultaneous determination of three bufadienolides in rat plasma after intravenous administration of bufadienolides extract by ultra performance liquid chromatography electrospray ionization tandem mass spectrometry by Yu Zhang; Xing Tang; Xiaoliang Liu; Fang Li; Xia Lin (pp. 224-231).

A novel, rapid and specific ultra performance liquid chromatography electrospray ionization tandem mass spectrometry (UPLC-ESI-MS/MS) method has been developed for simultaneous determination and pharmacokinetic studies of three bufadienolides (bufalin, cinobufagin and resibufogenin) in rat plasma. The analytes, bufalin, cinobufagin, resibufogenin and the internal standard, diphenhydramine were extracted from rat plasma samples by a one-step liquid–liquid extraction and separated on an ACQUITY UPLC™ BEH C₁₈ column with gradient elution using a mobile phase composed of acetonitrile and water (containing 0.1% formic acid) at a flow rate of 0.20mLmin⁻¹. Detection was carried out on a triple-quadrupole tandem mass spectrometer in the multiple reaction monitoring (MRM) mode via an electrospray ionization (ESI) interface. The three bufadienolides could be simultaneously determined within 3.0min. Linear calibration curves were obtained over the concentration ranges of 1.0–200ngmL⁻¹ for all the analytes. The intra- and inter-day precisions (relative standard deviation (R.S.D.)) were less than 11.35 and 10.87%, respectively. The developed method was applied for the first time to the pharmacokinetic studies of bufadienolides in rats following a single intravenous administration of 2.10mgkg⁻¹ bufadienolides.

Keywords: Bufadienolides; Ultra performance liquid chromatography–tandem mass spectrometry; Pharmacokinetics; Rat plasma

Short-wave near-infrared spectroscopy analysis of major compounds in milk powder and wavelength assignment by Di Wu; Yong He; Shuijuan Feng (pp. 232-242).

In this study, short-wave near-infrared (NIR) spectroscopy at 800–1050nm region was investigated for the analysis of main compounds in milk powder. Through quantitative analysis, the feasibility is further demonstrated for the simultaneous measurement of fat, proteins and carbohydrate in milk powder. Two models, partial least-squares and least-squares support vector machine, were compared and utilized for regression coefficients and loading weights. The affect of standard normal variate spectral pretreatment to model performance was evaluated. Based on the resulted coefficients and loading weights, interesting wavelength regions of nutrition in milk powder are screened and the assignment of all specific wavelengths is firstly proposed in the details associated with chemical base. Instead of the whole short-wave NIR spectral data, these assigned wavelengths which can be reliably exploited were used for the content determination. Compared with other spectroscopy technique, assigned short-wave NIR spectral wavelengths did a good work. Determination coefficients for prediction are 0.981, 0.984, and 0.982, respectively for three components. The proposed wavelength assignment in the short-wave NIR region could be used for the component contents determination of milk powder, and could be as a guidance to interpret the spectra of milk powder.

Keywords: Short-wave near-infrared spectroscopy (short-wave NIRS); Milk powder; Wavelength assignment; Partial least-squares (PLS); Least-squares support vector machine (LS-SVM)

Effect of gold nanoparticle as a novel nanocatalyst on luminol–hydrazine chemiluminescence system and its analytical application by A. Safavi; G. Absalan; F. Bamdad (pp. 243-248).

In this work the catalytic role of unsupported gold nanoparticles on the luminol–hydrazine reaction is investigated. Gold nanoparticles catalyze the reaction of hydrazine and dissolved oxygen to generate hydrogen peroxide and also catalyze the oxidation of luminol by the produced hydrogen peroxide. The result is an intense chemiluminescence (CL) due to the excited 3-aminophthalate anion. In the absence of gold nanoparticles no detectable CL was observed by the reaction of luminol and hydrazine unless an external oxidant is present in the system. The size effect of gold nanoparticles on the CL intensity was investigated. The most intensive CL signals were obtained with 15-nm gold nanoparticles. UV–vis spectra and transmission electron microscopy studies were used to investigate the CL mechanism. The luminol and hydroxide ion concentration, gold nanoparticles size and flow rate were optimized. The proposed method was successfully applied to the determination of hydrazine in boiler feed water samples. Between 0.1 and 30μM of hydrazine could be determined with a detection limit of 30nM.

Keywords: Unsupported gold nanoparticles; Catalysis; Chemiluminescence; Hydrazine; Nanocatalyst

Immobilization enzyme fluorescence capillary analysis for determination of lactic acid by Yong-Sheng Li; Xiang Ju; Xiu-Feng Gao; Yuan-Yuan Zhao; Yan-Fei Wu (pp. 249-256).

A new method for the determination of lactic acid based on the immobilization enzyme fluorescence capillary analysis (IE-FCA) was proposed. Lactic dehydrogenase (LDH) was immobilized on inner surface of a capillary with glutaraldehyde, and an immobilized enzyme lactate capillary bioreactor (IE-LCBR) was formed for the determination of lactic acid. After nicotinamide adenine dinucleotide (NAD⁺) is mixed with lactic acid solution, it was sucked into the IE-LCBR and was detected at λ_ex 353nm/ λ_em 466nm. Optimized conditions are as follows: the temperature is 38°C; the reaction time is 15min; the concentrations of Tris buffer (pH 8.8) and NAD⁺ are 0.1molL⁻¹ and 4mmolL⁻¹, respectively; the concentration of LDH used for immobilization is 15kUL⁻¹. The concentration of lactic acid is directly proportional to the fluorescence intensity measured from 0.50 to 2.0mmolL⁻¹; and the analytical recovery of added lactic acid was 99–105%. The minimum detection limit of the method is 0.40mmolL⁻¹ and sensitivity of the IE-CBR is 4.6Fmmol⁻¹L⁻¹ lactate. Its relative standard deviation (R.S.D.) is ≤2.0%. This IE-FCA method was employed for determination of lactate in milk drink.

Keywords: Immobilization enzyme; Fluorescence capillary analysis; Reduced nicotinamide adenine dinucleotide; Lactic acid

Determination of adenosine disodium triphosphate using prulifloxacin–terbium(III) as a fluorescence probe by spectrofluorimetry by Fengshan Yu; Lin Li; Fang Chen (pp. 257-262).

A new spectrofluorimetric method is developed for determination of adenosine disodium triphosphate (ATP). The interactions between prulifloxacin (PUFX)–Tb³⁺ complex and adenosine disodium triphosphate has been studied by using UV–vis absorption and fluorescence spectra. Using prulifloxacin–Tb³⁺ as a fluorescence probe, under the optimum conditions, ATP can remarkably enhance the fluorescence intensity of the prulifloxacin–Tb³⁺ complex at λ=545nm and the enhanced fluorescence intensity is in proportion to the concentration of ATP. Optimum conditions for the determination of ATP were also investigated. The dynamic range for the determination of ATP is 4.0×10⁻⁷ to 2.0×10⁻⁵molL⁻¹, and the detection limit (3 σ/ k) is 1.7×10⁻⁸molL⁻¹. This method is simple, practical and relatively free interference from coexisting substances and can be successfully applied to determination of ATP in real pharmaceutical samples. The mechanism of fluorescence enhancement of prulifloxacin–Tb³⁺ complex by ATP was also discussed.

Keywords: Terbium; Prulifloxacin; Spectrofluorimetry; Adenosine disodium triphosphate; Luminescence mechanism

Enantioseparation and impurity determination of the enantiomers of novel phenylethanolamine derivatives by high performance liquid chromatography on amylose stationary phase by Jing Yang; Jin Guan; Li Pan; Kun Jiang; Maosheng Cheng; Famei Li (pp. 263-267).

Simple and efficient analytical HPLC methods using Chiralpak AS-H as chiral stationary phase were developed for direct enantioseparation of 11 novel phenylethanolamine derivatives. The chromatographic experiments were performed in normal phase mode with n-hexane–ethanol–triethylamine (TEA) as mobile phase. Excellent baseline enantioseparation was obtained for most of compounds. The effects of the concentration of organic modifiers and column temperature were studied for the enantiomeric separation. The mechanism of chiral recognition was discussed based on the relationship between the thermodynamic parameters and structures of compounds. It was found that the enantioseparations were all enthalpy driven, and the tert-butyl groups of compounds had significant influence on the chiral recognition. Trantinterol enantiomers were resolved ( R_s=2.73) within 14min using n-hexane–ethanol–TEA (98:2:0.1, v/v/v) as mobile phase with a flow rate of 0.8mLmin⁻¹ at 30°C. The optimized method was validated for linearity, precision, accuracy and stability in solution and proved to be robust. The limits of detection (LOD) and quantification (LOQ) for (+)-trantinterol were 0.15 and 0.46μgmL⁻¹. The method was applied for enantiomeric impurity determination of (−)-trantinterol bulk samples.

Keywords: Chiral stationary phase; Chiral separation; Phenylethanolamine derivatives; Trantinterol enantiomers; Validation method

Automatic in-tube SPME and fast liquid chromatography: A cost-effective method for the estimation of dibuthyl and di-2-ethylhexyl phthalates in environmental water samples by C. Cháfer-Pericás; P. Campíns-Falcó; M.C. Prieto-Blanco (pp. 268-273).

A 80-cm length commercially available capillary coated with 95% polydimethylsiloxane and 5% polydiphenylsiloxane (TBR-5) was employed to carry out on-line extraction and preconcentration of dibuthyl phthalate (DBP) and di-2-ethylhexyl phthalate (DEHP) in the chromatographic system. The coated capillary was placed between the sample injection loop and the injection needle of an autosampler. Variables affecting the automatic in-tube solid-phase microextraction (SPME) were optimized. A Genesis C₁₈ (5cm×4.6mm i.d., 4μm particle size) was employed as analytical column. The achieved limits of detection by use of diode array detection were 1 and 2.5μgL⁻¹, respectively. The proposed conditions have been applied to determine those compounds at low ppb levels (≤250μgL⁻¹) in aqueous samples. No matrix effect was found, and recoveries between 85 and 115% were obtained. The precision of the method was good, and the achieved intra- and inter-day variation coefficients were between 5 and 20%. The analysis time per sample was 20min and any off-line pre-treatment of the samples was needed. The taken sample volume was 100μL. Data on the application of the described method to the analysis of different water samples are presented.

Keywords: In-tube solid-phase microextraction; Dibuthyl phthalate; Di-2-ethylhexyl phthalate; Liquid chromatography; Diode array detection; Automatic method

Simultaneous analysis of different classes of phytohormones in coconut ( Cocos nucifera L.) water using high-performance liquid chromatography and liquid chromatography–tandem mass spectrometry after solid-phase extraction by Zhen Ma; Liya Ge; Anna S.Y. Lee; Jean Wan Hong Yong; Swee Ngin Tan; Eng Shi Ong (pp. 274-281).

Coconut ( Cocos nucifera L.) water, which contains many uncharacterized phytohormones is extensively used as a growth promoting supplement in plant tissue culture. In this paper, a high-performance liquid chromatography (HPLC) method was developed for the simultaneous determination of various classes phytohormones, including indole-3-acetic acid (IAA), indole-3-butyric acid (IBA), abscisic acid (ABA), gibberellic acid (GA), zeatin (Z), N⁶-benzyladenine (BA), α-naphthaleneacetic acid (NAA) and 2,4-dichlorophenoxyacetic acid (2,4-D) in young coconut water (CW). The analysis was carried out using a reverse-phase HPLC gradient elution, with an aqueous mobile phase (containing 0.1% formic acid, pH adjusted to 3.2 with triethylamine (TEA)) modified by methanol, and solute detection made at 265nm wavelength. The method was validated for specificity, quantification, accuracy and precision. After preconcentration of putative endogenous phytohormones in CW using C₁₈ solid-phase extraction (SPE) cartridges, the HPLC method was able to screen for putative endogenous phytohormones present in CW. Finally, the identities of the putative phytohormones present in CW were further confirmed using independent liquid chromatography–tandem mass spectrometry (LC–MS/MS) equipped with an electrospray ionization (ESI) interface.

Keywords: Coconut water; Phytohormones; High-performance liquid chromatography; Liquid chromatography–tandem mass spectrometry

Computational design and synthesis of molecular imprinted polymers with high selectivity for removal of aniline from contaminated water by Junhai Yao; Xin Li; Wu Qin (pp. 282-288).

A computational approach was developed to screening functional monomers and polymerization solvents for rational design of molecularly imprinted polymer (MIP). It was based on the comparison of the binding energy of the complexes between the template and different functional monomers. The effect of the polymerization solvent was included using the polarizable continuum model. According to the theoretical calculation results, the MIP with aniline as template was prepared by emulsion polymerization method using acrylamide (AAM) as functional monomer and divinylbenzene as cross-linker in carbon tetrachloride. The synthesized MIP was then tested by equilibrium-adsorption method, and the MIP demonstrated high removal efficiency to the aniline. The results of this study have indicated the possibility of using computer aided design for rational selection of functional monomers and solvents capable of removal of aniline from contaminated water.

Keywords: Molecularly imprinted polymer; Aniline; Molecular modeling; Ab initio calculation

Influences of sampling volume and sample concentration on the analysis of atmospheric carbonyls by 2,4-dinitrophenylhydrazine cartridge by Raktim Pal; Ki-Hyun Kim (pp. 289-296).

In this study, the analytical bias involved in the application of the 2,4-dinitrophenylhydrazine (2,4-DNPH)-coated cartridge sampling method was investigated for the analysis of five atmospheric carbonyl species (i.e., acetaldehyde, propionaldehyde, butyraldehyde, isovaleraldehyde, and valeraldehyde). In order to evaluate the potential bias of the sampling technique, a series of the laboratory experiments were conducted to cover a wide range of volumes (1–20L) and concentration levels (approximately 100–2000ppb in case of acetaldehyde). The results of these experiments were then evaluated in terms of the recovery rate (RR) for each carbonyl species. The detection properties of these carbonyls were clearly distinguished between light and heavy species in terms of RR and its relative standard error (R.S.E.). It also indicates that the studied analytical approach can yield the most reliable pattern for light carbonyls, especially acetaldehyde. When these experimental results were tested further by a two-factor analysis of variance (ANOVA), the analysis based on the cartridge sampling method is affected more sensitively by the concentration levels of samples rather than the sampling volume.

Keywords: Carbonyl; 2,4-Dinitrophenylhydrazine cartridge; Sampling volume; Analytical bias

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Analytica Chimica Acta (v.610, #2)