In situ derivatization hollow fibre liquid-phase microextraction for the determination of biogenic amines in food samples

Hollow fibre liquid-phase microextraction with in situ derivatization using dansyl chloride has been successfully developed for the high-performance liquid chromatography-ultraviolet (HPLC-UV) determination of the biogenic amines (tryptamine, putrescine, cadaverine, histamine, tyramine, spermidine) in food samples. Parameters affecting the performance of the in situ derivatization process such as type of extraction solvent, temperature, extraction time, stirring speed and salt addition were studied and optimized. Under the optimized conditions (extraction solvent, dihexyl ether; acceptor phase, 0.1 M HCl; extraction time, 30 min; extraction temperature, 26 °C; without addition of salt), enrichment factors varying from 47 to 456 were achieved. Good linearity of the analytes was obtained over a concentration range of 0.1–5 μg mL⁻¹ (with correlation coefficients of 0.9901–0.9974). The limits of detection and quantification based on a signal-to-noise ratio of 3–10, ranged from 0.0075 to 0.030 μg mL⁻¹ and 0.03 to 0.10 μg mL⁻¹, respectively. The relative standard deviations based on the peak areas for six replicate analysis of water spiked with 0.5 μg mL⁻¹ of each biogenic amine were lower than 7.5%. The method was successfully applied to shrimp sauce and tomato ketchup samples, offering an interesting alternative to liquid–liquid extraction and solid phase extraction for the analysis of biogenic amines in food samples.     

A new method for the determination of biogenic amines in cheese by LC with evaporative light scattering detector

This paper presents a new LC method with evaporative light scattering detection (ELSD), for the separation and determination of the biogenic amines (histamine, spermidine, spermine, tyramine, putrescine and β-phenylethylamine) which are commonly present in cheese, as their presence and relative amounts give useful information about freshness, level of maturing, quality of storage and cheese authentication. The LC-ELSD method is validated by comparison of the results with those obtained through LC-UV determination, based on a pre-column dansyl chloride derivatisation step. The obtained data demonstrate that both methods can be interchangeably used for biogenic amines determination in cheese. The new LC-ELSD method shows good precision and permits to achieve, for standard solutions, limit of detection (LOD) values ranging from 1.4 to 3.6 mg L⁻¹ and limit of quantitation (LOQ) values ranging from 3.6 to 9.3 mg L⁻¹. The whole methodology, comprehensive of the homogenization-extraction process and LC-ELSD analysis, has been applied in the analysis of a typical Calabria (Southern Italy) POD cheese, known as Caciocavallo Silano. The most aboundant amine found was histamine, followed, in decreasing order, by tyramine, spermine, putrescine, β-phenylethylamine and spermidine, for a total amount of 127 mg kg⁻¹. This value does not represent a possible risk for consumer health, according to the toxicity levels reported in literature and regarded as acceptable.     

Conversion to isothiocyanates via dithiocarbamates for the determination of aromatic primary amines by headspace-solid phase microextraction and gas chromatography

A novel and highly selective method has been developed for the determination of aromatic primary amines by their conversion to dithiocarbamates by reaction with carbon disulphide, and then to isothiocyanates, which are volatile, by heating in the presence of a heavy metal ion. Zinc(II) was selected owing to its low toxicity and optimum yield of isothiocyanates. The latter were sampled by headspace-solid phase microextraction (HS-SPME) on divinylbenzene-carboxen-polydimethylsiloxane fibre, 50/30 μm. The HS-SPME procedure was optimized to provide adequate limits of detection in the analysis of aromatic amines in their real samples by gas chromatography with mass spectrometry (GC–MS) or flame ionization detection (GC–FID). The method gave rectilinear calibration graph, correlation coefficient and limit of detection, respectively, over the range 0.08–100 μg L⁻¹, 0.9950–0.9990 and 25–240 ng L⁻¹ in gas chromatography–mass spectrometry, and 0.01–10 mg L⁻¹, 0.9910–0.9991 and 0.8–3.0 μg L⁻¹ in gas chromatography–flame ionization detection. At two different levels, 10 and 40 μg L⁻¹, the range of intra-day RSD was 3.7–8.5% (GC–MS) and 3.3–9.2% (GC–FID), respectively. The proposed method is simple and rapid, and has been applied to determine aromatic primary amines in the environmental waters, food samples of ice cream powder and soft drinks concentrate, and food colours. The intra-day RSD in the analysis of real samples by GC–MS was in the range 3.6–6.2%. The food/colour samples were found to contain elevated levels of aniline and 2-toluidine.     

Analysis of aldehydes in beer by gas-diffusion microextraction: Characterization by high-performance liquid chromatography–diode-array detection–atmospheric pressure chemical ionization–mass spectrometry

In this work, a recently developed extraction technique for sample preparation aiming the analysis of volatile and semi-volatile compounds named gas-diffusion microextraction (GDME) is applied in the chromatographic analysis of aldehydes in beer. Aldehydes—namely acetaldehyde (AA), methylpropanal (MA) and furfural (FA)—were simultaneously extracted and derivatized with 2,4-dinitrophenylhydrazine (DNPH), then the derivatives were separated and analyzed by high-performance liquid chromatography with spectrophotometric detection (HPLC–UV). The identity of the eluted compounds was confirmed by high-performance liquid chromatography–atmospheric pressure chemical ionization–mass-spectrometry detection in the negative ion mode (HPLC–APCI–MS). The developed methodology showed good repeatability (ca. 5%) and linearity as well as good limits of detection (AA–12.3, FA–1.5 and MA 5.4 μg L⁻¹) and quantification (AA–41, FA–4.9 and MA 18 μg L⁻¹); it also appears to be competitive in terms of speed and cost of analysis.     

Feasibility of ultra-high performance liquid and gas chromatography coupled to mass spectrometry for accurate determination of primary and secondary phthalate metabolites in urine samples

Phthalates (PAEs) are ubiquitous toxic chemical compounds. During the last few years, some phthalate metabolites (MPAEs) have been proposed as appropriate biomarkers in human urine samples to determine PAE human intake and exposure. So, it is necessary to have fast, easy, robust and validated analytical methods to determine selected MPAEs in urine human samples. Two different instrumental methods based on gas (GC) and ultra-high performance liquid (UHPLC) chromatography coupled to mass spectrometry (MS) have been optimized, characterized and validated for the simultaneous determination of nine primary and secondary phthalate metabolites in urine samples. Both instrumental methods have similar sensitivity (detection limits ranged from 0.03 to 8.89 pg μL⁻¹ and from 0.06 to 0.49 pg μL⁻¹ in GC–MS and UHPLC–MS², respectively), precision (repeatability, expressed as relative standard deviation, which was lower than 8.4% in both systems, except for 5OH-MEHP in the case of GC–MS) and accuracy. But some advantages of the UHPLC–MS² method, such as more selectivity and lower time in the chromatographic runs (6.8 min vs. 28.5 min), have caused the UHPLC–MS² method to be chosen to analyze the twenty one human urine samples from the general Spanish population. Regarding these samples, MEP showed the highest median concentration (68.6 μg L⁻¹), followed by MiBP (23.3 μg L⁻¹), 5cx-MEPP (22.5 μg L⁻¹) and MBP (19.3 μg L⁻¹). MMP (6.99 μg L⁻¹), 5oxo-MEHP (6.15 μg L⁻¹), 5OH-MEHP (5.30 μg L⁻¹) and MEHP (4.40 μg L⁻¹) showed intermediate levels. Finally, the lowest levels were found for MBzP (2.55 μg L⁻¹). These data are within the same order of magnitude as those found in other similar populations.     

Sensitive determination of hydrazine in water by gas chromatography–mass spectrometry after derivatization with ortho-phthalaldehyde

A gas chromatography–mass spectrometric (GC–MS) method has been established for the determination of hydrazine in drinking water and surface water. This method is based on the derivatization of hydrazine with ortho-phthalaldehyde (OPA) in water. The following optimum reaction conditions were established: reagent dosage, 40 mg mL⁻¹ of OPA; pH 2; reaction for 20 min at 70 °C. The organic derivative was extracted with methylene chloride and then measured by GC–MS. Under the established condition, the detection and the quantification limits were 0.002 μg L⁻¹ and 0.007 μg L⁻¹ by using 5.0-mL of surface water or drinking water, respectively. The calibration curve showed good linearity with r² = 0.9991 (for working range of 0.05–100 μg L⁻¹) and the accuracy was in a range of 95–106%, and the precision of the assay was less than 13% in water. Hydrazine was detected in a concentration range of 0.05–0.14 μg L⁻¹ in 2 samples of 10 raw drinking water samples and in a concentration range of 0.09–0.55 μg L⁻¹ in 4 samples of 10 treated drinking water samples.     

Determination of octylphenol and nonylphenol in aqueous sample using simultaneous derivatization and dispersive liquid–liquid microextraction followed by gas chromatography–mass spectrometry

A simple and fast sample preparation method for the determination of nonylphenol (NP) and octylphenol (OP) in aqueous samples by simultaneous derivatization and dispersive liquid–liquid microextraction (DLLME) was investigated using gas chromatography–mass spectrometry (GC/MS). In this method, a combined dispersant/derivatization catalyst (methanol/pyridine mixture) was firstly added to an aqueous sample, following which a derivatization reagent/extraction solvent (methyl chloroformate/chloroform) was rapidly injected to combine in situ derivatization and extraction in a single step. After centrifuging, the sedimented phase containing the analytes was injected into the GC port by autosampler for analysis. Several parameters, such as extraction solvent, dispersant solvent, amount of derivatization reagent, derivatization and extraction time, pH, and ionic strength were optimized to obtain higher sensitivity for the detection of NP and OP. Under the optimized conditions, good linearity was observed in the range of 0.1–1000 μg L⁻¹ and 0.01–100 μg L⁻¹ with the limits of detection (LOD) of 0.03 μg L⁻¹ and 0.002 μg L⁻¹ for NP and OP, respectively. Water samples collected from the Pearl River were analyzed with the proposed method, the concentrations of NP and OP were found to be 2.40 ± 0.16 μg L⁻¹ and 0.037 ± 0.001 μg L⁻¹, respectively. The relative recoveries of the water samples spiked with different concentrations of NP and OP were in the range of 88.3–106.7%. Compared with SPME and SPE, the proposed method can be successfully applied to the rapid and convenient determination of NP and OP in aqueous samples.     

Multi-residue method for the determination of organochlorine pesticides in fish feed based on a cleanup approach followed by gas chromatography–triple quadrupole tandem mass spectrometry

A multi-residue method for the determination of organochlorine pesticides in fish feed samples was developed and optimized. The method is based on a cleanup step of the extracted fat, carried out by liquid–liquid extraction on diatomaceous earth cartridge with n-hexane/acetonitrile (80/20, v/v) followed by solid phase extraction (SPE) with silica gel–SCX cartridge, before the identification and quantification of the residues by gas chromatography–triple quadrupole tandem spectrometry (GC–MS/MS). Performance characteristics, such as accuracy, precision, linear range, limits of detection (LOD) and quantification (LOQ), for each pesticide were determined. Instrumental LODs ranged from 0.01 to 0.11 μg L⁻¹, LOQs were in the range of 0.02–0.35 μg L⁻¹, and calibration curves were linear (r² > 0.999) in the whole range of explored concentrations (5–100 μg L⁻¹). Repeatability values were in the range of 3–15%, evaluated from the relative standard deviation of six samples spiked at 100 μg kg⁻¹ of fat, and in compliance with that derived by the Horwitz's equation. No matrix effects or interfering substances were observed in fish feed analyses. The proposed method allowed high recoveries (92–116%) of spiked extracted fat samples at 100 μg kg⁻¹, and very low LODs (between 0.02 and 0.63 μg kg⁻¹) and LOQs (between 0.05 and 2.09 μg kg⁻¹) determined in fish feed samples.     

A new multiresponse optimization approach in combination with a D-Optimal experimental design for the determination of biogenic amines in fish by HPLC-FLD

A new strategy to approach multiresponse optimization in conjunction to a D-optimal design for simultaneously optimizing a large number of experimental factors is proposed. The procedure is applied to the determination of biogenic amines (histamine, putrescine, cadaverine, tyramine, tryptamine, 2-phenylethylamine, spermine and spermidine) in swordfish by HPLC-FLD after extraction with an acid and subsequent derivatization with dansyl chloride. Firstly, the extraction from a solid matrix and the derivatization of the extract are optimized. Ten experimental factors involved in both stages are studied, seven of them at two levels and the remaining at three levels; the use of a D-optimal design leads to optimize the ten experimental variables, significantly reducing by a factor of 67 the experimental effort needed but guaranteeing the quality of the estimates. A model with 19 coefficients, which includes those corresponding to the main effects and two possible interactions, is fitted to the peak area of each amine. Then, the validated models are used to predict the response (peak area) of the 3456 experiments of the complete factorial design. The variability among peak areas ranges from 13.5 for 2-phenylethylamine to 122.5 for spermine, which shows, to a certain extent, the high and different effect of the pretreatment on the responses. Then the percentiles are calculated from the peak areas of each amine. As the experimental conditions are in conflict, the optimal solution for the multiresponse optimization is chosen from among those which have all the responses greater than a certain percentile for all the amines. The developed procedure reaches decision limits down to 2.5 μg L⁻¹ for cadaverine or 497 μg L⁻¹ for histamine in solvent and 0.07 mg kg⁻¹ and 14.81 mg kg⁻¹ in fish (probability of false positive equal to 0.05), respectively.     

Determination of priority pollutants in aqueous samples by dispersive liquid–liquid microextraction

A dispersive liquid–liquid microextraction (DLLME) method followed by high-performance liquid chromatography–triple quadrupole mass spectrometry has been developed for the simultaneous determination of linear alkylbenzene sulfonates (LAS C₁₀, C₁₁, C₁₂, and C₁₃), nonylphenol (NP), nonylphenol mono- and diethoxylates (NP₁EO and NP₂EO), and di-(2-ethylhexyl)phthalate (DEHP). The applicability of the method has been tested by the determination of the above mentioned organic pollutants in tap water and wastewater. Several parameters affecting DLLME, such as, the type and volume of the extraction and disperser solvents, sample pH, ionic strength and number of extractions, have been evaluated. Methanol (1.5 mL) was selected among the six disperser solvent tested. Dichlorobenzene (50 μL) was selected among the four extraction solvent tested. Enrichment factor achieved was 80. Linear ranges in samples were 0.01–3.42 μg L⁻¹ for LAS C₁₀–₁₃ and NP₂EO, 0.09–5.17 μg L⁻¹ for NP₁EO, 0.17–9.19 μg L⁻¹ for NP and 0.40–17.9 μg L⁻¹ for DEHP. Coefficients of correlation were higher than 0.997. Limits of quantitation in tap water and wastewater were in the ranges 0.009–0.019 μg L⁻¹ for LAS, 0.009–0.091 μg L⁻¹ for NP, NP₁EO and NP₂EO and 0.201–0.224 μg L⁻¹ for DEHP. Extraction recoveries were in the range from 57 to 80%, except for LAS C₁₀ (30–36%). The method was successfully applied to the determination of these pollutants in tap water and effluent wastewater from Seville (South of Spain). The DLLME method developed is fast, easy to perform, requires low solvent volumes and allows the determination of the priority hazardous substances NP and DEHP (Directive 2008/105/EC).     

Determination of oxytetracycline in milk samples by polymer inclusion membrane separation coupled to high performance liquid chromatography

The determination of oxytetracycline in milk samples using a polymer inclusion membrane concept with high performance liquid chromatography (HPLC) was studied. The membranes developed are composed by cellulose acetate as polymer base, Cyanex 923 as carrier and o-nitrophenyl octyl ether as plasticizer. In the optimal conditions, the method exhibits good linearity in the range 0.03–0.20 mg L⁻¹ with a limit of detection and quantification of 8.2 and 27.3 μg L⁻¹ respectively. The method was successfully applied to the analysis of milk samples with high selectivity.     

Preparation of stir cake sorptive extraction based on polymeric ionic liquid for the enrichment of benzimidazole anthelmintics in water,honey and milk samples

In this work, a new stir cake sorptive extraction (SCSE) using polymeric ionic liquid monolith as sorbent was prepared. The sorbent was obtained by in situ copolymerization of an ionic liquid, 1-allyl-3-methylimidazolium bis[(trifluoro methyl)sulfonyl]imide (AMII) and divinylbenzene (DB) in the presence of N,N-dimethylformamide. The influence of the content of ionic liquid and the porogen in the polymerization mixture on extraction performance was studied thoroughly. The physicochemical properties of the polymeric ionic liquid were characterized by infrared spectroscopy, elemental analysis, scanning electron microscopy and mercury intrusion porosimetry. The usefulness of SCSE–AMIIDB was demonstrated by the enrichment of trace benzimidazole anthelmintics. Several parameters affecting the extraction efficiency were investigated, and under the optimized conditions, a simple and effective method for the determination of trace benzimidazoles residues in water, milk and honey samples was established by coupling SCSE–AMIIDB with high performance liquid chromatography/diode array detection (SCSE–AMIIDB–HPLC/DAD). Results indicated that the limits of detection (S/N = 3) for target compounds were 0.020–0.072 μg L⁻¹, 0.035–0.10 μg L⁻¹ and 0.026–0.076 μg L⁻¹ in water, milk and honey samples, respectively. In addition, an acceptable reproducibility was achieved by evaluating the repeatability and intermediate precision with relative standard deviations (RSD) of less than 9% and 11%, respectively. Finally, the established AMII–SCSE–HPLC/DAD method was successfully applied for the determination of benzimidazoles residues in milk, honey and environmental water samples. Recoveries obtained for the determination of benzimidazole anthelmintics in spiking samples ranged from 70.2% to 117.6%, with RSD below 12% in all cases.     

Quantitative determination of 22 primary aromatic amines by cation-exchange solid-phase extraction and liquid chromatography–mass spectrometry

Primary aromatic amines (PAAs) have been broadly studied due to their high toxicity. In this work a method for the analysis of 22 PAAs in aqueous simulants has been developed. The method is based on a solid-phase extraction step using cation-exchange cartridges and the subsequent analysis of the extracts by ultra-high-performance liquid chromatography with mass spectrometric detection. The recoveries obtained for all the amines analyzed ranged between 81 and 109%, linear range was between 0.03 and 75 μg L⁻¹, with the RSD values between 4.5 and 13.4% and an average value of 7.5% and limits of detection at μg L⁻¹ level. The method has been applied to two real samples obtained from migration experiments of polyurethane based laminates to simulant B (water with 3% (w/v) acetic acid) which represents the worst case for the migration of aromatic amines. The main amines found in both samples were methylenedianiline isomers, obtained from the corresponding residual diisocyanates used during polyurethane adhesive polymerization. The total amine concentration found was 26 and 6.3 μg of aniline equivalents per kg of food simulant.     

Ion chromatography for rapid and sensitive determination of fluoride in milk after headspace single-drop microextraction with in situ generation of volatile hydrogen fluoride

In this article, we report a new method that involves headspace single-drop microextraction and ion chromatography for the preconcentration and determination of fluoride. The method lies in the in situ hydrogen fluoride generation and subsequent sequestration into an alkaline microdrop (15 μL) exposed to the headspace above the stirred aqueous sample. The NaF formed in the drop was then determined by ion chromatography. The influences of some crucial single-drop microextraction parameters such as the extraction temperature, extraction time, sample stirring speed, sulphuric acid concentration and ionic strength of the sample, on extraction efficiency were investigated. In the optimal condition, an enrichment factor of 97 was achieved in 15 min. The calibration working range was from 10 μg L⁻¹ to 2000 μg L⁻¹ (R² = 0.998), and the limit of detection (signal to noise ratio of 3) was 3.8 μg L⁻¹ of fluoride. Finally, the proposed method was successfully applied to the determination of fluoride in different milk samples. The recoveries of fluoride (at spiked concentrations of 200 μg L⁻¹ and 600 μg L⁻¹ into milk) in real samples ranged from 96.9% to 107.7%. Intra-day precision (N = 3) in terms of peak area, expressed as relative standard deviation, was found to be within the range of 0.24-1.02%.     

Development and validation of a hydrophilic interaction liquid chromatographic method for determination of aromatic amines in environmental water

A simple, precise, and accurate hydrophilic interaction liquid chromatographic (HILIC) method has been developed for the determination of five aromatic amines in environmental water samples. Chromatography was carried out on a bare silica column, using a mixture of acetonitrile and a buffer of NaH₂PO₄–H₃PO₄ (pH 1.5, containing 10 mM NaH₂PO₄) (85:15, v/v) as a mobile phase at a flow rate of 1 mL min⁻¹. Aromatic amines were detected by UV absorbance at 254 nm. The linear range of amines was good (r² > 0.998) and limit of detection (LOD) within 0.02–0.2 mg L⁻¹ (S/N = 3). The retention mechanism for the analytes under the optimum conditions was determined to be a combination of adsorption, partition and ionic interactions. The proposed method was applied to the environmental water samples. Aromatic amines were isolated from aqueous samples using solid-phase extraction (SPE) with Oasis HLB cartridges. Recoveries of greater than 75% with precision (RSD) less than 12% were obtained at amine concentrations of 5–50 μg L⁻¹ from 100 mL river water and influents from a wastewater treatment plant (WWTP). The present HILIC technique proved to be a viable method for the analysis of aromatic amines in the environmental water samples.     

A novel capillary electrophoretic method for determining methylglyoxal and glyoxal in urine and water samples

Two non-electroactive biomarkers methylglyoxal (MGo) and glyoxal (Go) in urine and environmental water samples were determined for the first time by capillary electrophoresis with amperometric detection (CE-AD) after derivatizing with an electroactive compound 2-thiobarbituric acid. Experimental conditions of derivatization and CE-AD detection were optimized. Highly linear response was obtained for these two biomarkers over three orders of magnitude with good correlation (r² > 0.999). The limits of detection (LODs) and limits of quantitation (LOQs) of MGo and Go were 0.2 μg L⁻¹ and 1.0 μg L⁻¹, 0.5 μg L⁻¹ and 2.0 μg L⁻¹, respectively. The average recovery and relative standard deviation (RSD) were within the range of 90.9–101.3% and 0.7–2.2%, respectively. The proposed CE-AD method provides a reliable and sensitive quantitative evaluation of MGo and Go in real sample matrices by employing relatively simple and inexpensive instrument.     

Mass spectrometric profiling of saturated fatty acid esters of steroids separated by high-temperature gas chromatography

An efficient analytical method for simultaneous determination of 12 SFEs in serum is described. The method involves solid-phase extraction to isolate of SFEs from interfering species, especially cholesteryl esters, conversion to trimethylsilyl (TMS) ether derivatives for the direct analysis by gas chromatography–mass spectrometry (GC–MS) using a high temperature MXT-1 (Silcosteel-treated stainless steel) capillary column. All SFEs as their TMS derivatives were well separated with excellent peak shapes within 12 min. Overall recoveries ranged from 88% to 119%, with a detection limits for SFEs ranged from 2 to 30 μg L⁻¹. The linearity as correlation coefficient was higher than 0.99 except for pregnenolone-3-arachidate (r² = 0.98) in the concentration range of 5–3000 μg L⁻¹. Ten serum samples obtained from volunteers were also analyzed and quantitatively determined of DHEA-3-palmitate and pregnenolone-3-stearate in 1.8–1195.8 μg L⁻¹ concentration. The devised high temperature GC–MS method could be useful for identification of SFEs in biological specimens including serum.     

Monitoring of biologically active amines in cereals and cereal based food products by HPLC

Summary Biologically active amines (putreanine sulphate, N-acetyl putrescine, putrescine, cadaverine, histamine, agmatine, N-acetyl spermidine, spermidine, spermine) were separated and quantified in cereal flour and cereal products by a liquid chromatographic method. The method consists of the separation of ion pairs formed between biologically active amines and octanesulphonic acid on a reversed-phase column, postcolumn derivatization with o-phtalaldehyde-2-mercapthoethanol and spectrofluorometric detection. Results of the reliability study were satisfactory. The method was linear for each amine at 1–10 mg L⁻¹. Putrescine and spermidine were the only amines always detected in cereal flour and cereal products, ranging from 2.45 to 47.83 mg kg⁻¹ for putrescine and 3.27 to 37.14 mg kg⁻¹ for spermidine. The most important differences among types of samples were found in polyamine derivatives. Presented at: Balaton Symposium on High-Performance Separation Methods, Siófok, Hungary, September 3–5, 1997.     

Determination of the steroid hormone levels in water samples by dispersive liquid-liquid microextraction with solidification of a floating organic drop followed by high-performance liquid chromatography

In this study, the steroid hormone levels in river and tap water samples were determined by using a novel dispersive liquid-liquid microextraction method based on the solidification of a floating organic drop (DLLME-SFO). Several parameters were optimized, including the type and volume of the extraction and dispersive solvents, extraction time, and salt effect. DLLME-SFO is a fast, cheap, and easy-to-use method for detecting trace levels of samples. Most importantly, this method uses less-toxic solvent. The correlation coefficient of the calibration curve was higher than 0.9991. The linear range was from 5 to 1000 μg L⁻¹. The spiked environmental water samples were analyzed using DLLME-SFO. The relative recoveries ranged from 87% to 116% for river water (which was spiked with 4 μg L⁻¹ for E1, 3 μg L⁻¹ for E2, 4 μg L⁻¹ for EE2 and 9 μg L⁻¹ for E3) and 89% to 102% for tap water (which was spiked with 6 μg L⁻¹ for E1, 5 μg L⁻¹ for E2, 6 μg L⁻¹ for EE2 and 10 μg L⁻¹ for E3). The detection limits of the method ranged from 0.8 to 2.7 μg L⁻¹ for spiked river water and 1.4 to 3.1 μg L⁻¹ for spiked tap water. The methods precision ranged from 8% to 14% for spiked river water and 7% to 14% for spiked tap water.     

NMR investigation of acrolein stability in hydroalcoholic solution as a foundation for the valid HS-SPME/GC–MS quantification of the unsaturated aldehyde in beverages

Acrolein (propenal) is found in many foods and beverages and may pose a health hazard due to its cytotoxicity. Considerable knowledge gaps regarding human exposure to acrolein exist, and there is a lack of reliable analytical methods. Hydroalcoholic dilutions prepared for calibration purposes from pure acrolein show considerable degradation of the compound and nuclear magnetic resonance (NMR) spectroscopy showed that 1,3,3-propanetriol and 3-hydroxypropionaldehyde are formed. The degradation can be prevented by addition of hydroquinone as stabilizer to the calibration solutions, which then show linear concentration-response behaviour required for quantitative analysis. The stabilized calibration solutions were used for quantitative headspace solid-phase microextraction/gas chromatography–mass spectrometry (HS-SPME/GC–MS) determination of acrolein in alcoholic beverages with a detection limit of 14 μg L⁻¹. Of 117 tested alcoholic beverages, 64 were tested positive with the highest incidence in grape marc spirits and whiskey (100%, mean 252 μg L⁻¹), followed by fruit spirits (86%, mean 591 μg/L⁻¹), tequila (86%, mean 404 μg L⁻¹), Asian spirits (43%, mean 54 μg L⁻¹) and wine (9%, mean 0.7 μg L⁻¹). Acrolein could not be detected in beer, vodka, absinthe and bottled water. Six of the fruit and grape marc spirits had acrolein levels above the World Health Organization (WHO) provisional tolerable concentration of 1.5 mg L⁻¹.