Gas chromatography mass spectrometer determination of dimethylamine impurity in N,N-dimethylformamide solvent by derivatization of N,N-dimethylbenzamide with benzoyl chloride agent.

This study describes the development of a reliable and linear analytical method for precisely determining dimethylamine impurity in N,N-dimethylformamide solvent utilizing a benzoyl chloride derivatization reagent and a gas chromatography mass spectrometer. Benzoyl chloride was used to derivatize dimethylamine. At normal temperature, benzoyl chloride combined with dimethylamine, producing N,N-dimethylbenzamide. This method separated N,N-dimethylbenzamide using Rtx-5 amine (30 m × 0.32 mm × 1.50 µm) as the stationary phase, helium as the carrier gas, argon as the collision gas, and methanol as the diluent. The column flow rate was 2 mL/min. The retention time of N,N-dimethylbenzamide was determined to be 8.5 min. Precision, linearity, and accuracy were tested using ICH Q2 (R2) and USP<1225> guidelines. The percentage coefficient of variation (CV) for N,N-dimethylbenzamide in the system suitability parameter was 1.1%. The correlation coefficient of N,N-dimethylbenzamide was found to be >0.99. In the method precision parameter, the % CV for N,N-dimethylbenzamide was found to be 1.9%, whereas the % CV for N,N-dimethylbenzamide was 1.2% in intermediate precision. The percentage recovery of N,N-dimethylbenzamide was determined to be between 80% and 98%.

Competitive Uptake of Dimethylamine and Trimethylamine against Ammonia on Acidic Particles in Marine Atmospheres.

Alkaline gases such as NH3 and amines play important roles in neutralizing acidic particles in the atmosphere. Here, two common gaseous amines (dimethylamine (DMA) and trimethylamine (TMA)), NH3, and their corresponding ions in PM2.5 were measured semicontinuously using an ambient ion monitor-ion chromatography (AIM-IC) system in marine air during a round-trip cruise of approximately 4000 km along the coastline of eastern China. The concentrations of particulate DMA, detected as DMAH+, varied from <4 to 100 ng m-3 and generally decreased with increasing atmospheric NH3 concentrations. Combining observations with thermodynamic equilibrium calculations using the extended aerosol inorganics model (E-AIM) indicated that the competitive uptake of DMA against NH3 on acidic aerosols generally followed thermodynamic equilibria and appeared to be sensitive to DMA/NH3 molar ratios, resulting in molar ratios of DMAH+ to DMA + DMAH+ of 0.31 ± 0.16 (average ± standard deviation) at atmospheric NH3 concentrations over 1.8 µg m-3 (with a corresponding DMA/NH3 ratio of (1.8 ± 1.0) × 10-3), 0.80 ± 0.15 at atmospheric NH3 concentrations below 0.3 µg m-3 (with a corresponding DMA/NH3 ratio of (1.3 ± 0.6) × 10-2), and 0.56 ± 0.19 in the remaining cases. Particulate TMA concentrations, detected as TMAH+, ranged from <2 to 21 ng m-3 and decreased with increasing concentrations of atmospheric NH3. However, TMAH+ was depleted concurrently with the formation of NH4NO3 under low concentrations of atmospheric NH3, contradictory to the calculated increase in the equilibrated concentration of TMAH+ by the E-AIM.

Fast and Robust Quantification of Detergent Micellization Thermodynamics from Isothermal Titration Calorimetry.

Detergents are widely used in modern in vitro biochemistry and biophysics, in particular to aid the characterization of integral membrane proteins. An important characteristic of these chemicals in aqueous solutions is the concentration above which their molecular monomers self-associate to form micelles, termed the critical micellar concentration (CMC). Micelles are supramolecular assemblies arranged with the hydrophobic portions oriented inward and the hydrophilic head groups positioned outward to interact with the aqueous solvent. Knowledge of the CMC is not only of practical relevance but also of theoretical interest because it provides thermodynamic insights. Isothermal titration calorimetry (ITC) is a powerful method to determine CMCs, as it furnishes additional information on the enthalpy and entropy of micellization. Here we describe our extension of previous methods to determine CMCs and other thermodynamic parameters from ITC demicellization curves. The new algorithm, incorporated into the stand-alone software package D/STAIN, analyzes ITC demicellization curves by taking advantage of state-of-the-art thermogram-integration techniques and automatically providing rigorous confidence intervals on the refined parameters. As a demonstration of the software's capabilities, we undertook ITC experiments to determine the respective CMCs of n-octyl ß-d-glucopyranoside (OG), n-dodecyl ß-d-maltopyranoside (DDM), and lauryldimethylamine N-oxide (LDAO). Motivated by the fact that in vitro membrane protein studies often require additives such as precipitants (e.g., polyethylene glycol (PEG)), we also carried out ITC demicellization studies in the presence of PEG3350, finding in all cases that PEG had significant effects on the thermodynamics of detergent micellization.

A faster and simpler UPLC-MS/MS method for the simultaneous determination of trimethylamine N-oxide, trimethylamine and dimethylamine in different types of biological samples.

Gut microbiota-dependent metabolites trimethylamine N-oxide (TMAO), trimethylamine (TMA) and dimethylamine (DMA) from dietary methylamines have recently gained much attention due to their high association with chronic kidney disease risk. Hence a simpler and faster performance liquid chromatography-tandem mass spectrometry method was developed and validated. The quantitative analysis was achieved within 6 min by using Agilent 6460C UPLC-MS/MS with 10% methyl alcohol isocratic elution and was more simple, convenient and rapid than that of previously reported methods. Furthermore, method verification results showed that the method correlation coefficient was 0.99978293, 0.99997514 and 0.98784721, and the detection limit was 0.121, 8.063 and 0.797 µg L-1, and the precision of the retention time and peak area of analytes was less than 0.331 and 3.280, respectively. The method was applied to simultaneously determine TMAO, TMA and DMA in the urine and serum from mice treated with normal, high l-carnitine, or high choline diet. Quantitative recoveries of TMAO, TMA and DMA were in the range of 94.2%-101.0%, and the RSD values were lower than 5.17%. The proposed UPLC-MS/MS-based assay should be of value for further evaluating TMAO as a risk marker and for examining the effect of dietary factors on TMAO metabolism.

The presence of aliphatic and aromatic amines in reservoir and canal water as precursors to disinfection by-products.

This research aimed at determining the dimethylamine (DMA), diethylamine (DEA), dibutylamine (DBA), and aromatic aniline (AN) in reservoir and canal water in the U-Tapao River Basin, Songkhla, Thailand. The trihalomethane formation potential (THMFP) and N-nitrosodimethylamine formation potential (NDMA-FP) of the reservoir and canal water were analyzed. Water samples from two reservoirs and raw water from water treatment plants at upstream, midstream, and downstream locations of the canal were collected twice. The analysis of the DMA, DEA, DBA, and AN were conducted using gas chromatography and spectrofluorometry techniques. The DMA, DEA, and DBA levels in the reservoir and canal waters ranged from not detectable (ND) to 10 µg/L and from ND to 21.2 µg/L, respectively. AN was detected from 123 to 129 ng/L and from 112 to 177 ng/L in the reservoir and canal waters, respectively. The DMA, DEA, DBA, and AN exhibited two fluorescent peaks at 230nmEx/345nmEm and 280 nmEx/355nmEm. These two peaks corresponded to the peak positions of tryptophan. Detection limits of DMA, DEA, and DBA for fluorescent analysis were 500 µg/L whereas that of AN and tryptophan were 10 and 0.5 µg/L, respectively. The NDMA-FP measured in all the water samples was lower than the detection limit of 237 ng/L. THMFP ranged from 175 to 248 µg/L and 214 to 429 µg/L was detected in the reservoir and canal waters, respectively. The THMFP/dissolved organic carbon (DOC) of the reservoir and canal waters were comparable within the ranges of 73 to 131 µg THMFP/mg DOC.

A novel liquid chromatography-mass spectrometric method for the simultaneous determination of trimethylamine, dimethylamine and methylamine in fishery products.

A novel multianalyte method has been developed to determine the concentration of trimethylamine (TMA), dimethylamine (DMA) and methylamine (MA) in fish. The optimal points of the key parameters (pH 8, 60 °C and 60 min of reaction time) were determined for the reaction with tert-butyl bromoacetate. An HILIC column was used to elute all the compounds in only 12 min and selective quantitation of the compounds was achieved. The methodology was validated in trout, hake and Atlantic horse mackerel and was used to study the shelf life of fish under refrigeration. A good correlation with the picrate method was obtained and the proposed methodology has been proved to be robust, specific and sensible with a limit of detection of 0.08 mg N-TMA kg(-1) in freshwater fish and 1 mg N-TMA kg(-1) in marine fish. In addition, TMA has been proved to be a good spoilage indicator also in freshwater fish.

Development of an SPME-GC-MS method for the specific quantification of dimethylamine and trimethylamine: use of a new ratio for the freshness monitoring of cod fillets.

BACKGROUND: Fish is a highly perishable food, so it is important to be able to estimate its freshness to ensure optimum quality for consumers. The present study describes the development of an SPME-GC-MS technique capable of quantifying both trimethylamine (TMA) and dimethylamine (DMA), components of what has been defined as partial volatile basic nitrogen (PVB-N). This method was used, together with other reference methods, to monitor the storage of cod fillets (Gadus morhua) conserved under melting ice. RESULTS: Careful optimisation enabled definition of the best parameters for extracting and separating targeted amines and an internal standard. The study of cod spoilage by sensory analysis and TVB-N assay led to the conclusion that the shelf-life of cod fillet was between 6 and 7 days. Throughout the study, TMA and DMA were specifically quantified by SPME-GC-MS; the first was found to be highly correlated with the values returned by steam distillation assays. Neither TMA-N nor DMA-N were able to successfully characterise the decrease in early freshness, unlike dimethylamine/trimethylamine ratio (DTR), whose evolution is closely related to the results of sensory analysis until the stage where fillets need to be rejected. CONCLUSION: DTR was proposed as a reliable indicator for the early decrease of freshness until fish rejection. © 2015 Society of Chemical Industry.

Role of Chlorine Dioxide in N-Nitrosodimethylamine Formation from Oxidation of Model Amines.

N-Nitrosodimethylamine (NDMA) is an emerging disinfection byproduct, and we show that use of chlorine dioxide (ClO2) has the potential to increase NDMA formation in waters containing precursors with hydrazine moieties. NDMA formation was measured after oxidation of 13 amines by monochloramine and ClO2 and pretreatment with ClO2 followed by postmonochloramination. Daminozide, a plant growth regulator, was found to yield 5.01 ± 0.96% NDMA upon reaction with ClO2, although no NDMA was recorded during chloramination. The reaction rate was estimated to be ∼0.0085 s(-1), and on the basis of our identification by mass spectrometry of the intermediates, the reaction likely proceeds via the hydrolytic release of unsymmetrical dimethylhydrazine (UDMH), with the hydrazine structure a key intermediate in NDMA formation. The presence of UDMH was confirmed by gas chromatography-mass spectrometry analysis. For 10 of the 13 compounds, ClO2 preoxidation reduced NDMA yields compared with monochloramination alone, which is explained by our measured release of dimethylamine. This work shows potential preoxidation strategies to control NDMA formation may not impact all organic precursors uniformly, so differences might be source specific depending upon the occurrence of different precursors in source waters. For example, daminozide is a plant regulator, so drinking water that is heavily influenced by upstream agricultural runoff could be at risk.

Single-particle speciation of alkylamines in ambient aerosol at five European sites.

Alkylamines are associated with both natural and anthropogenic sources and have been detected in ambient aerosol in a variety of environments. However, little is known about the ubiquity or relative abundance of these species in Europe. In this work, ambient single-particle mass spectra collected at five sampling sites across Europe have been analysed for their alkylamine content. The aerosol time-of-flight mass spectrometer (ATOFMS) data used were collected in Ireland (Cork), France (Paris, Dunkirk and Corsica) and Switzerland (Zurich) between 2008 and 2013. Each dataset was queried for mass spectral marker ions associated with the following ambient alkylamines: dimethylamine (DMA), trimethylamine (TMA), diethylamine (DEA), triethylamine (TEA), dipropylamine (DPA) and tripropylamine (TPA). The fraction of ambient particles that contained detectable alkylamines ranged from 1 to 17 % depending on location, with the highest fractions observed in Paris and Zurich in the winter months. The lowest fractions were observed at coastal sites, where the influence of animal husbandry-related alkylamine emissions is also expected to be lowest. TMA was the most ubiquitous particle phase alkylamine detected and was observed at all locations. Alkylamines were found to be internally mixed with both sulphate and nitrate for each dataset, suggesting that aminium salt formation may be important at all sites investigated. Interestingly, in Corsica, all alkylamine particles detected were also found to be internally mixed with methanesulphonic acid (MSA), indicating that aminium methanesulphonate salts may represent a component of marine ambient aerosol in the summer months. Internal mixing of alkylamines with sea salt was not observed, however. Alkylamine-containing particle composition was found to be reasonably homogeneous at each location, with the exception of the Corsica and Dunkirk sites, where two and four distinct mixing states were observed, respectively.

Branching ratios in reactions of OH radicals with methylamine, dimethylamine, and ethylamine.

The branching ratios for the reaction of the OH radical with the primary and secondary alkylamines: methylamine (MA), dimethylamine (DMA), and ethylamine (EA), have been determined using the technique of pulsed laser photolysis-laser-induced fluorescence. Titration of the carbon-centered radical, formed following the initial OH abstraction, with oxygen to give HO2 and an imine, followed by conversion of HO2 to OH by reaction with NO, resulted in biexponential OH decay traces on a millisecond time scale. Analysis of the biexponential curves gave the HO2 yield, which equaled the branching ratio for abstraction at αC-H position, r(αC-H). The technique was validated by reproducing known branching ratios for OH abstraction for methanol and ethanol. For the amines studied in this work (all at 298 K): r(αC-H,MA) = 0.76 ± 0.08, r(αC-H,DMA) = 0.59 ± 0.07, and r(αC-H,EA) = 0.49 ± 0.06 where the errors are a combination in quadrature of statistical errors at the 2σ level and an estimated 10% systematic error. The branching ratios r(αC-H) for OH reacting with (CH3)2NH and CH3CH2NH2 are in agreement with those obtained for the OD reaction with (CH3)2ND (d-DMA) and CH3CH2ND2 (d-EA): r(αC-H,d-DMA) = 0.71 ± 0.12 and r(αC-H,d-EA) = 0.54 ± 0.07. A master equation analysis (using the MESMER package) based on potential energy surfaces from G4 theory was used to demonstrate that the experimental determinations are unaffected by formation of stabilized peroxy radicals and to estimate atmospheric pressure yields. The branching ratio for imine formation through the reaction of O2 with α carbon-centered radicals at 1 atm of N2 are estimated as r(CH2NH2) = 0.79 ± 0.15, r(CH2NHCH3) = 0.72 ± 0.19, and r(CH3CHNH2) = 0.50 ± 0.18. The implications of this work on the potential formation of nitrosamines and nitramines are briefly discussed.

Molecular understanding of atmospheric particle formation from sulfuric acid and large oxidized organic molecules.

Atmospheric aerosols formed by nucleation of vapors affect radiative forcing and therefore climate. However, the underlying mechanisms of nucleation remain unclear, particularly the involvement of organic compounds. Here, we present high-resolution mass spectra of ion clusters observed during new particle formation experiments performed at the Cosmics Leaving Outdoor Droplets chamber at the European Organization for Nuclear Research. The experiments involved sulfuric acid vapor and different stabilizing species, including ammonia and dimethylamine, as well as oxidation products of pinanediol, a surrogate for organic vapors formed from monoterpenes. A striking resemblance is revealed between the mass spectra from the chamber experiments with oxidized organics and ambient data obtained during new particle formation events at the Hyytiälä boreal forest research station. We observe that large oxidized organic compounds, arising from the oxidation of monoterpenes, cluster directly with single sulfuric acid molecules and then form growing clusters of one to three sulfuric acid molecules plus one to four oxidized organics. Most of these organic compounds retain 10 carbon atoms, and some of them are remarkably highly oxidized (oxygen-to-carbon ratios up to 1.2). The average degree of oxygenation of the organic compounds decreases while the clusters are growing. Our measurements therefore connect oxidized organics directly, and in detail, with the very first steps of new particle formation and their growth between 1 and 2 nm in a controlled environment. Thus, they confirm that oxidized organics are involved in both the formation and growth of particles under ambient conditions.

Factors affecting catalysis of copper corrosion products in NDMA formation from DMA in simulated premise plumbing.

This study investigated the effects of corrosion products of copper, a metal commonly employed in household plumbing systems, on N-nitrosodimethylamine (NDMA) formation from a known NDMA precursor, dimethylamine (DMA). Copper-catalyzed NDMA formation increased with increasing copper concentrations, DMA concentrations, alkalinity and hardness, but decreased with increasing natural organic matter (NOM) concentration. pH influenced the speciation of chloramine and the interactions of copper with DMA. The transformation of monochloramine (NH2Cl) to dichloramine and complexation of copper with DMA were involved in elevating the formation of NDMA by copper at pH 7.0. The inhibiting effect of NOM on copper catalysis was attributed to the rapid consumption of NH2Cl by NOM and/or the competitive complexation of NOM with copper to limit the formation of DMA-copper complexes. Hardness ions, as represented by Ca(2+), also competed with copper for binding sites on NOM, thereby weakening the inhibitory effect of NOM on NDMA formation. Common copper corrosion products also participated in these reactions but in different ways. Aqueous copper released from malachite [Cu2CO3(OH)2] was shown to promote NDMA formation while NDMA formation decreased in the presence of CuO, most likely due to the adsorption of DMA.

Photo-dissociation of dimethylamine by KrBr* excilamp.

A study of dimethylamine photo-dissociation in the gas phase has been conducted using UV radiation delivered from a KrBr(*) excilamp, driven by a sinusoidal electronic control gear with maximum emission at wavelength of 207 nm. The electrical input power and radiant power of the lamp were measured to determine their effects on the degradation. The influence of flow velocity and initial concentration of dimethylamine were also examined. In order to evaluate the photo-dissociation process comprehensively, several parameters were investigated, including removal efficiency, energy yield, carbon balance and CO2 selectivity. It is shown that the removal efficiency increases with enhanced input power and decreased gas flow rate. A high removal efficiency of 68% is achieved for lamp power 102W and flow velocity 15 m(3) h(-1). The optimum dimethylamine initial concentration is around 3520 mg m(-3), for which the energy yield reaches up to 442 gk Wh(-1) when the input power is 65W. In addition, two chain compounds (1,3-bis-dimethylamino-2-propanol; 3-penten-2-one, 4-amino) and three ring organic matters (1-azetidinecarboxaldehyde, 2,2,4,4-tetramethyl; N-m-tolyl-succinamic acid; p-acetoacetanisidide), were identified by GC-MS as secondary products, in order to demonstrate the pathways of the dimethylamine degradation.

Decomposition of dimethylamine gas with dielectric barrier discharge.

The decomposition of dimethylamine (DMA) with gas under high flow rate was investigated with dielectric barrier discharge (DBD) technology. Different parameters including removal efficiency, energy yield, carbon balance and CO2 selectivity, secondary products, as well as pathways and mechanisms of DMA degradation were studied. The experimental results showed that removal efficiency of DMA depended on applied voltage and gas flow rate, but had no obvious correlation with initial concentration. Excellent energy performance was obtained using present DBD technology for DMA abatement. When experiment conditions were controlled at: gas flow rate of 14.9 m(3)/h, initial concentration of 2104 mg/m(3), applied voltage of 4.8 kV, removal efficiency of DMA and energy yield can reach 85.2% and 953.9 g/kWh, respectively. However, carbon balance (around 40%) was not ideal due to shorter residence time (about 0.1s), implying that some additional conditions should be considered to improve the total oxidation of DMA. Moreover, secondary products in outlet gas stream were detected via gas chromatogram-mass spectrum and the amounts of NO3(-) and NO2(-) were analyzed by ion chromatogram. The obtained data demonstrated that NOx might be suppressed due to reductive NH radical form DMA dissociation. The likely reaction pathways and mechanisms for the removal of DMA were suggested based on products analysis. Experimental results demonstrated the application potential of DBD as a clean technology for organic nitrogen-containing gas elimination from gas streams.

Dissipation and residues of 2,4-D: -dimethylammonium in wheat and soil.

The environmental behavior of 720 g/L 2,4-D: -dimethylammonium AS under wheat field conditions was studied in detail. The dissipation behaviors of 2,4-D: -dimethylammonium in wheat and soil were fitted to first-order kinetic equation (C = C (0) e (-lambdat )). But different experimental points and years have different initial deposits and half-lives (T (1/2)). After applying 720 g/L 2,4-D: -dimethylammonium AS at recommended dosage and 1.5-fold recommended dosage during 3-4 leaf stage, the residues of 2,4-D: -dimethylammonium in wheat plant, wheat grain and soil were all lower than 0.02 mg/kg. The obtained results suggested that, it is safety for application at the recommended dosage during 3-4 leaf stage to control weeds in wheat field.

Dimethylamine, trimethylamine, and biogenic amine formation in high-pressure processed semidried squid (Todarodes pacificius) during refrigerated storage.

The quality properties of semidried squid treated with high-pressure processing (HPP) were investigated during refrigerated storage. The vacuum-packed semidried squid samples were subjected to 500 MPa for 0 min (HPP-0), 5 min (HPP-5), and 10 min (HPP-10) by using a custom-made high-pressure processor and stored at a refrigerated temperature for 28 d. The populations of indigenous psychrotrophic and mesophilic bacteria were effectively reduced by approximately 1 and 2 log CFU/g at the HPP-10 treatment, respectively. Compared to the control, the bacterial counts in HPP-treated semidried squid samples were maintained at low levels throughout the storage period. The increase in the amounts of dimethylamine (DMA) and trimethylamine (TMA) was more pronounced at the unpressurized control than at the HPP treatments. The production of biogenic amines (BAs) varied with HPP treatment during refrigerated storage. Therefore, the application of HPP may provide a significant improvement in the safety and quality of semidried squid.

Simultaneous determination of dimethylamine, trimethylamine and trimethylamine-n-oxide in aquatic products extracts by ion chromatography with non-suppressed conductivity detection.

An ion chromatography method with non-suppressed conductivity detection was developed for the simultaneous determination of dimethylamine (DMA), trimethylamine (TMA) and trimethylamine-n-oxide (TMAO) in aquatic products. They were separated by means of cation-exchange chromatography using a 3.0 mmol/L methanesulfonic acid solution as eluent and an IonPac CS17 column (250 mm x 4 mm i.d.) as the separation column. Detection limits of dimethylamine, trimethylamine and trimethylamine-n-oxide were 0.06, 0.08 and 0.10 mg/L, respectively. The relative standard deviations (RSDs) of peak area were less than 3.53%. The recoveries were between 93.7% and 104.1%. Unlike traditional methods, this validated method is inexpensive and stable.

Fabric softeners: nearly instantaneous characterization and quality control of cationic surfactants by easy ambient sonic-spray ionization mass spectrometry.

A tiny droplet of typical samples of fabric softeners from different commercial brands placed on a smooth paper surface was subjected to easy ambient sonic-spray ionization mass spectrometry (EASI-MS). With no need for sample-preparation or pre-separation procedures, EASI-MS and EASI-MS/MS identify nearly instantaneously the main surfactants and the homologous series employed in their formulations. Adulterated and low quality samples containing no or less efficient softeners are also easily recognized.

Trimethylamine oxide, dimethylamine, trimethylamine and formaldehyde levels in main traded fish species in Hong Kong.

Levels of trimethylamine oxide (TMAO), dimethylamine (DMA), trimethylamine (TMA) and formaldehyde (FA) were studied in 266 different fishes, including fresh/frozen raw whole fishes of 89 different species that traded in Hong Kong, China. Determination of TMAO can confirm the source of DMA and FA if present in the sample. These samples were purchased from different commercial outlets between April and August 2007. All samples of raw whole fish were identified for their species by the Agriculture, Fisheries and Conservation Department. The content of TMAO was determined by high-performance liquid chromatography (HPLC) coupled with a chemiluminescent nitrogen detector. The possible decomposition products of TMAO, DMA and TMA were analysed by headspace solid-phase micro-extraction gas chromatography-mass spectrometry (HS-SPME-GC-MS), while FA was conducted by steam distillation then quantified by a HPLC. The range for TMAO of all samples was <5-3800 mg kg(-1) with median of 970 mg kg(-1), while the endogenous enzymatic cleavage products DMA, TMA and FA were in the range of <2-320, <1-190 and <1-160 mg kg(-1), respectively. These cleavage products were mainly found in three fish species, Harpadon nehereus, Saurida elongata and Saurida tumbil, that belong to the family Synodontidae (Lizardfishes) and subfamily Harpadontinae. Besides, freshwater fish species, namely, Micropterus salmoides, Oreochromis niloticus niloticus and Siniperca chuatsi, were found to contain TMAO in the range of 510-760, 85-720 and 400-640 mg kg(-1), respectively.