Graphene-coated cotton fibers as a sorbent for the extraction of multiclass pesticide residues from water and their determination by gas chromatography with mass spectrometry.

A straightforward functionalization procedure is proposed for synthesizing a cotton-supported graphene as an extraction material, which is effectively employed for the extraction of multiclass pesticides from environmental waters prior to their determination by gas chromatography with mass spectrometry. Different experimental parameters that affect the extraction efficiency, including pH of the extraction, stirring rate, extraction time, ionic strength, presence of humic acid, sample volume, amount of sorbent, and elution conditions, were investigated and properly established. The advantages of the present extraction method are the simplicity of implementation, rapidity, and low consumption of sorbent per extraction. Moreover, the pesticides on the adsorbent are stable, under certain storage conditions, rendering the cotton-supported graphene suitable for environmental field studies. The applicability of the cotton-graphene-based procedure for routine analysis was demonstrated by the determination of pesticides in a lake water sample. The recoveries ranged from 83 to 107%, the limits of quantitation were in the range of 0.02-0.09 µg/L, and the calculated relative standard deviations varied from 3 to 8% (data obtained with the same batch of sorbent). Because of the acceptable analytical characteristics, the developed method shows great prospects in determining certain classes of pesticides in water.

Continuous solid-phase extraction method for the determination of amines in human urine following on-line microwave-assisted acid hydrolysis.

Humans are exposed to endogenous or exogenous formation of aromatic amines (AAs) and N-nitrosamines (NAms), which are considered to be potent carcinogens. The objective of this study was to monitor AAs and NAms in human urine to obtain a way to assess exposure. However, while NAms can be directly detected in urine samples, AAs require hydrolysis to convert their conjugates into free amines. A semiautomatic flow-base method is proposed for the simultaneous determination of aliphatic and aromatic NAms, anilines and chloroanilines in human urine in one analytical run. Conjugated AAs are released from urine by on-line microwave-assisted acid hydrolysis without degradation of NAms; all amines were then preconcentrated using solid-phase extraction. Separation/determinations are carried out by gas chromatography and mass spectrometry operating in selected ion monitoring mode. The method is fast (∼15 min for 25 mL of sample) and provides low limits of detection (from 2 to 26 ng/L) with good precision (relative standard deviation within and between days less than 7%). Finally, the proposed method was successfully applied to check AAs and NAms in the human urine of exposed and unexposed researchers. The kinetics of amine excretion in the urine of the researchers exposed is calculated after termination of the exposure and shows half-life times between 1.3 and 2.1 h, and that the dosage absorbed was eliminated within 6 h after exposure.

Evaluation of stationary phases and gas chromatographic detectors for determination of amines in water.

For the first time, a systematic overview deals with the advantages and disadvantages of several stationary phases (polar and non-polar) and gas chromatographic detectors (flame ionization detector, nitrogen-phosphorus detector and MS) for the determination of 27 amines (aliphatic and aromatic amines and N-nitrosamines) in water samples. To increase sensitivity (250 mL of sample was eluted with 150 µL of solvent) and matrix elimination, an automatic SPE system was employed prior to GC determination. The best results in terms of resolution and retention times were achieved using a column coated with 5% phenyl-dimethylpolysiloxane (DB-5). Capacity factor (k) values for the 27 amines increased with the rise in the polarity of the stationary phase, ranging from 3.0-27.7 and 2.2-14.4 for polar (polyethylene glycol) and non-polar (DB-5) columns, respectively. The detection limits of the method were 0.9-9 µg/L for flame ionization detector, 8-95 ng/L for nitrogen-phosphorus detector and 0.2-6.3 ng/L for MS. The precision was similar for the three detectors (RSD, 3.7-6.0%). The GC-MS method was applied with a high degree of accuracy and precision to determine amines in real samples including tap, river, pond, well, swimming pool and wastewaters.

Screening of N-nitrosamines in tap and swimming pool waters using fast gas chromatography.

N-Nitrosamines (NAms) are suspected human carcinogens that have been identified as drinking water and wastewater pollutants. In this work, a sensitive screening/confirmation method was proposed for the determination of the most toxic NAms that can be found in water samples (N-nitrosodimethylamine, N-nitrosodiethylamine, N-nitrosodibutylamine, N-nitrosomorpholine, N-nitrosopiperidine, and N-nitrosopyrrolidine). A sample volume of 250 mL was first preconcentrated in an automatic SPE unit and then the extract was concentrated to a final volume of 10 microL (providing a preconcentration factor of 25,000). Aliquots of the extract were subjected to a rapid screening process (1.6 min) by using a short capillary polar column (1.5 m length) and GC with nitrogen-phosphorous detection. In this way, the high number of samples to be tested routinely in a water laboratory is simplified due to a reduction in the analysis time. Thus, the screening method acts as a filter that indicates whether target analytes are present, above or below the cut-off level (3.8 or 10.4 ng/L), giving no false negatives at concentrations below the guide values for NAms in drinking water established by different countries. Positive samples (tap and swimming pool waters) were then confirmed by GC-MS detection.

Fullerenes for aromatic and non-aromatic N-nitrosamines discrimination.

The detection of N-nitrosamines (NAms) in water supplies is an environmental and public health issue because many NAms are classified as probable human carcinogens. Non-aromatic (aliphatic and cyclic) NAms are more toxic than aromatic ones as their maximum admissible concentration is limited in drinking water (20-2000ngL(-1)). From that premise, a simple and novel method to discriminate between both fractions of NAms according to their toxicity was proposed. An automatic solid-phase extraction unit containing two sequential sorbent columns was constructed. A sample volume of 25mL was passed through a C(60) fullerene column in which only the aromatic fraction was retained, and the effluent was then passed through a Merck LiChrolut EN column where the non-aromatic fraction was retained. Following elution of the non-aromatic NAms with 150microL of ethyl acetate-acetonitrile (9:1), 1microL of the extract was injected into a GC/MS. A comparative study of C(60) and C(70) fullerenes and nanotubes revealed C(60) fullerene to be the best choice to selectively retain the aromatic fraction. The method exhibits a linear range of 15-20,000ngL(-1); limits of detection of 4-15ngL(-1); and an RSD of approximately 5%. Recoveries throughout the whole method were between 95% and 102% for six non-aromatic NAms spiked into several types of waters. Our study demonstrates that a simple and fast SPE system (10min per sample) with a customary GC-MS instrument permits the quantification of these amines in complex matrices with considerable sensitivity and selectivity.

Natural attenuation of diesel aliphatic hydrocarbons in contaminated agricultural soil.

A diesel fuel spill at a concentration of 1 L m(-2) soil was simulated on a 12 m(2) plot of agricultural land, and natural attenuation of aliphatic hydrocarbons was monitored over a period of 400 days following the spill after which the aliphatic hydrocarbon concentrations were found to be below the legal contamination threshold for soil. The main fraction of these compounds (95%) remained at the surface layer (0-10 cm). Shortly after the spill (viz. between days 0 and 18), evaporation was the main origin of the dramatic decrease in pollutant concentrations in the soil. Thereafter, soil microorganisms used aliphatic hydrocarbons as sources of carbon and energy, as confirmed by the degradation ratios found. Soil quality indicators, soil microbial biomass and dehydrogenase activity, regained their original levels about 200 days after the spill.

Determination of several common disinfection by-products in frozen foods.

Disinfected water and/or disinfectants are commonly used by the freezing industry in such processes as sanitising, washing, blanching, cooling and transporting the final product. For this reason, disinfection by-products (DBPs) can be expected in frozen foods. This study focused on the presence of DBPs in a wide variety of frozen vegetables, meats and fish. For this purpose, the 14 halogenated DBPs more prevalent in disinfected water were selected (four trihalomethanes, seven haloacetic acids, two haloacetonitriles and trichloronitromethane). Up to seven DBPs were found in vegetables, whereas only four DBPs were present in meats and fish, and at lower concentrations, since their contact with disinfected water is lower than in frozen vegetables. It is important to emphasise that trichloronitromethane (the most abundant nitrogenous DBP in disinfected water) was found for the first time in foods. Finally, it was concluded that the freezing process can keep the compounds stable longer than other preservation processes (viz. sanitising, canning) and, therefore, frozen foods present higher DBP concentrations than other food categories (minimally processed vegetables, or canned vegetables and meats).

Comparison of the sensitivities of seven N-nitrosamines in pre-screened waters using an automated preconcentration system and gas chromatography with different detectors.

A simple, expeditious procedure for confirming the presence of N-nitrosamines in previously screened positive water samples was proposed. Water samples were continuously aspirated into a photometric flow system for screening. Positive samples were then confirmed and N-nitrosamines were identified by gas chromatography using different detectors (mass spectrometry, flame ionization and nitrogen-phosphorus). The system for the screening purpose was based on the preconcentration of the analytes onto a sorbent column, elution, and derivatization to form nitrite, then formation of a coloured product (Griess reaction) and photometric detection. The detection limits of the gas chromatographic method for 100 ml of sample were 2.0-3.5 microg/l, 20-80 and 3-13 ng/l for flame ionization, nitrogen-phosphorus and mass spectrometric detectors, respectively. The precision as RSD was similar for all detectors (3.0-6.5%). The screening of different types of water showed that wastewaters contain levels of N-nitrosamines that can be detected only using MS as a detector.

Gas chromatographic determination of N-nitrosamines in beverages following automatic solid-phase extraction.

A semiautomatic method for the determination of seven N-nitrosamines in beverages by gas chromatography with nitrogen-phosphorus detection is proposed. Beverage samples are aspirated into a solid-phase extraction module for preconcentration and cleanup. The influence of the experimental conditions was examined by using various sorbents among which LiChrolut EN was found to provide quantitative elution and the highest preconcentration factors of all. The proposed method is sensitive, with limits of detection between 7 and 33 ng/kg, and precise, with relative standard deviations from 4.3% to 6.0%. The recoveries of N-nitrosamines from beverage samples spiked with 0.5 or 1 microg/kg concentrations of these compounds ranged from 95% to 102%. The method was successfully applied to the determination of residues of the studied N-nitrosamines in beverages including beer, wine, liquor, whisky, cognac, rum, vodka, grape juice, cider, tonic water, and soft drinks. The analytes were only detected in beer samples, positives being confirmed by gas chromatography coupled with impact ionization mass spectrometry.

Quantitative analysis of aldehydes in canned vegetables using static headspace-gas chromatography-mass spectrometry.

Volatile aldehydes appear in canned vegetables as constituents and some of them can also be present as disinfection by-products (DBPs) because of the contact between vegetables and treated water. This paper describes two static headspace-gas chromatography-mass spectrometry (SHS-GC-MS) methods to determine 15 aldehydes in both the solid and the liquid phases of canned vegetables. The treatment for both phases of samples was carried out simultaneously into an SHS unit, including the leaching of the aldehydes (from the vegetable), their derivatization and volatilization of the oximes formed. Detection limits were obtained within the range of 15-400µg/kg and 3-40µg/L for aldehydes in the solid and the liquid phases of the food, respectively. The relative standard deviation was lower than 7% -for the whole array of the target analytes-, the trueness evaluated by recovery experiments provided %recoveries between 89 and 99% and short- and long-term stability studies indicated there was no significant variation in relative peak areas of all aldehydes in both phases of canned vegetables after their storing at 4°C for two weeks. The study of the origin of the 15 aldehydes detected between both phases of canned vegetables showed that: i) the presence of 13 aldehydes -at average concentrations of 2.2-39µg/kg and 0.25-71µg/L for the solid and the liquid phases, respectively- is because they are natural constituents of vegetables; and ii) the presence of glyoxal and methylglyoxal -which are mainly found in the liquid phase (average values, 1.4-4.1µg/L)- is ascribed to the use of treated water, thereby being DBPs.

Origin of low-molecular mass aldehydes as disinfection by-products in beverages.

A novel, simple and automatic method based on static headspace-gas chromatography-mass spectrometry has been developed to determine 10 low-molecular mass aldehydes that can be found in beverages, coming from the treated water used in their production. These aldehydes are the most frequently found in treated water as water disinfection by-products, so they can be used as indicators of the addition of treated water to beverages. The study covered a large number of fruit juices and soft drinks. The presence of the whole array of analytes is related to the contact with treated water during beverage production, mainly by the addition of treated water as ingredient. In particular, propionaldehyde, valeraldehyde and benzaldehyde can be used as indicators of the addition of treated water in these kinds of beverages. Among the ten aldehydes, only formaldehyde and acetaldehyde are naturally present in all kinds of fruit, and their concentrations are related to stage of the ripening of the fruit.

Simultaneous determination of 14 disinfection by-products in meat products using microwave-assisted extraction and static headspace coupled to gas chromatography-mass spectrometry.

This paper described the first analytical method to simultaneously determine 14 disinfection by-products (DBPs) in meat products using microwave-assisted extraction (MAE) and static headspace (SHS) followed by gas chromatography-mass spectrometry (GC-MS). The DBPs included were 4 trihalomethanes, 7 haloacetic acids, 2 haloacetonitriles and trichloronitromethane, which are commonly formed as a consequence of the disinfection process of water. The combination of the MAE and SHS techniques allows meat samples to be analysed in two sequential steps into the same HS vial in spite of the sample's complexity. Detection limits were obtained within the range of 0.06-0.70ng/g, and the average relative standard deviation was 7.4%. Recoveries throughout the whole process were between 86 and 95%. The SHS-GC-MS method was applied to determine DBPs in meat products with different industrial processing which could be contaminated through contact with disinfectants and/or treated water employed in the factory either for washing or for the cooking of meat. Up to 5 DBPs were found at ng/g levels in about 36% of the samples analysed, cooked ham being the most contaminated meat product because of the brine solutions employed in its manufacturing process.

Control of disinfection by-products in canned vegetables caused by water used in their processing.

Canned vegetables come into contact with sanitizers and/or treated water in industry during several steps (namely washing, sanitising, blanching and filling with sauces or brine solutions) and therefore they can contain disinfection by-products - DBPs). This study focused on the occurrence of trihalomethanes (THMs) and haloacetic acids (HAAs) in a wide variety of canned vegetables (75 samples). For each vegetable, the edible solid and liquid phases of the package were separated and analysed individually. DBPs can be present in both solid (up to eight species) and liquid (up to 11 species) phases, their levels being higher in liquid ones. Volatile THMs predominate in the edible solid phase (up to four species), while HAAs do so in the liquid phase (up to five species) according to their ionic and non-volatile nature. The lowest concentrations of DBPs were found in tomatoes because they were often preserved in their own juice, without water.

Origin of disinfection by-products in cheese.

The disinfection of water, equipment and surfaces in a cheese factory is one of the factors that can originate disinfection by-products (DBPs) in cheese. This research has focused on studying cheese factories in order to evaluate the individual contribution of each step of the cheese-making process that can contribute to the presence of DBPs in cheese. Ten factories were selected according to their salting processes (brine or dry salting). Each factory was monitored by the collection of six representative samples (factory water supply, brine solution, milk, whey, curd and cheese) in which the concentrations of up to eight chemicals were detected. The study shows that contact with brine solutions containing significant levels of DBPs is the main source of these chemicals in cheese. A minor factor is the pasteurised milk used in their manufacture.

Assessment of natural attenuation of volatile aromatic hydrocarbons in agricultural soil contaminated with diesel fuel.

A diesel fuel spill was simulated on a 12-m(2) plot of agricultural land, at a concentration of 1 Lm(-2) of soil. The natural attenuation of Volatile Aromatic Hydrocarbons (VAHs) was monitored at different soil depths over a period of 50 days. The natural attenuation of VAHs in the surface layer would be attributed to two processes, namely: volatilisation (mainly linked to the boiling point of each VAH, with t(1/2) from 2 to 71 min for benzene and p-isopropyltoluene, respectively); and dissipation (related to the boiling point as well as the analyte-soil matrix interaction, with t(1/2) from 2 to 169 h for benzene and p-isopropyltoluene, respectively). As expected, in the deeper layers, dissipation prevails over volatilisation. 50 days after the spill, only two VAHs were detected in the surface layer, at concentrations of 5-20 ngg(-1), which had disappeared after 80 days of the spill.

Static headspace-gas chromatography-mass spectrometry for the simultaneous determination of trihalomethanes and haloacetic acids in canned vegetables.

Canned vegetables appear to be a possible exposure pathway for hazardous disinfection by-products due to the use of sanitizers and treated water by the canning industry in the preparation of these foods. This work reports on two static headspace-gas chromatography-mass spectrometry methods for the simultaneous determination of 10 trihalomethanes (THMs) and 13 haloacetic acids (HAAs) in both solid and liquid phases of the canned vegetables. Both methods carry out the whole process (including the leaching of target analytes from the vegetable), derivatization of HAAs and volatilization of THMs and HAA esters, in a single step within a static headspace unit. The methods proposed provide an efficient and simple tool for the determination of regulated disinfection by-products in canned vegetables. Average limits of detection for THMs and HAAs were 0.19 and 0.45µg/kg, respectively, in the solid phase of canned vegetables, and 0.05 and 0.09µg/L, respectively, in the liquid phase. Satisfactory recoveries (90-99%) and precision, calculated as relative standard deviations (RSD≤10%), were obtained in both phases of canned vegetables. The methods proposed were applied for the analysis of frequently-used canned vegetables and confirmed the presence of up to 3 THMs and 5 HAAs at microgram per kilogram or liter levels in both phases of the samples.

Origin of haloacetic acids in milk and dairy products.

Haloacetic acids (HAAs) are formed during the process of water disinfection. Therefore their presence in foods can be correlated with the addition of or contact with treated water. To determine the origin of HAAs in milk and dairy products, firstly a chromatographic method was developed for their determination. The sample treatment involves deproteination of milk followed by derivatization/extraction of the HAAs in the supernatant. About 20% of the foods analyzed contained two HAAs - which in no case exceeded 2 µg L(-1), that can be ascribed to contamination from sanitizers usually employed in the dairy industry. The process of boiling tap water (containing HAAs) for the preparation of powdered infant formula did not remove them; therefore it would be advisable to prepare this type of milk with mineral water (free of HAAs). In addition, it is possible to establish if the milk has been adulterated with treated water through the determination of HAAs.

Analysis of endogenous aldehydes in human urine by static headspace gas chromatography-mass spectrometry.

Endogenous aldehydes (EAs) generated during oxidative stress and cell processes are associated with many pathogenic and toxicogenic processes. The aim of this research was to develop a solvent-free and automated analytical method for the determination of EAs in human urine using a static headspace generator sampler coupled with gas chromatography-mass spectrometry (HS-GC-MS). Twelve significant EAs used as markers of different biochemical and physiological processes, namely short- and medium-chain alkanals, α,ß-unsaturated aldehydes and dicarbonyl aldehydes have been selected as target analytes. Human urine samples (no dilution is required) were derivatized with O-2,3,4,5,6-pentafluorobenzylhydroxylamine in alkaline medium (hydrogen carbonate-carbonate buffer, pH 10.3). The HS-GC-MS method developed renders an efficient tool for the sensitive and precise determination of EAs in human urine with limits of detection from 1 to 15ng/L and relative standard deviations, (RSDs) from 6.0 to 7.9%. Average recoveries by enriching urine samples ranged between 92 and 95%. Aldehydes were readily determined at 0.005-50µg/L levels in human urine from healthy subjects, smokers and diabetic adults.

1-Butyl-3-aminopropyl imidazolium-functionalized graphene oxide as a nanoadsorbent for the simultaneous extraction of steroids and ß-blockers via dispersive solid-phase microextraction.

In this study, we describe the synthesis of graphene oxide functionalized with the ionic liquid 1-butyl-3-aminopropyl imidazolium chloride and its use as an adsorbent for the dispersive solid-phase microextraction (micro SPE) of four anabolic steroids and six ß-blockers from aqueous samples of environmental importance, prior to their HPLC-diode array detector analysis. As the ionic liquid is covalently attached to graphene oxide sheets, it is made possible for it to participate in the dispersive micro SPE procedure. The limits of detection and limits of quantification of the proposed method were found to be in the range of 7-23ng/L and between 20 and 70ng/L, respectively. The linearity was satisfactory, with the determination coefficients to range from 0.9940 to 0.9998 while the within- and between-day relative standard deviation of the method ranged between 3.1 and 7.6% and from 4.0 to 8.5%, respectively. In order to test the applicability of the proposed method in real-life samples, the effluent from a municipal wastewater treatment plant as well as natural water samples from two rivers and a lake were collected and analyzed. After the analysis of samples, the effluent from municipal wastewater treatment plant was fortified with the analytes, at concentrations equal to 2 and 10 times the LOQs. Recoveries were calculated after subtracting the native (no-spike) concentrations of analytes, when needed. All the recoveries were in the range of 87-98%. A comparison study attests to the superiority of the developed nanomaterial over graphene oxide and graphene for the dispersive micro SPE of steroids and ß-blockers.

Detection of regulated disinfection by-products in cheeses.

Cheese can contain regulated disinfection by-products (DBPs), mainly through contact with brine solutions prepared in disinfected water or sanitisers used to clean all contact surfaces, such as processing equipment and tanks. This study has focused on the possible presence of up to 10 trihalomethanes (THMs) and 13 haloacetic acids (HAAs) in a wide range of European cheeses. The study shows that 2 THMs, (in particular trichloromethane) and 3 HAAs (in particular dichloroacetic acid) can be found at µg/kg levels in the 56 cheeses analysed. Of the two types of DBPs, HAAs were generally present at higher concentrations, due to their hydrophilic and non-volatile nature. Despite their different nature (THMs are lipophilic), both of them have an affinity for fatty cheeses, increasing their concentrations as the percentage of water decreased because the DBPs were concentrated in the aqueous phase of the cheeses.