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1.
Application of a pH Feedback-Controlled Substrate Feeding Method in Lactic Acid Production 总被引:1,自引:0,他引:1
Substrate concentration in lactic acid fermentation broth could not be controlled well by traditional feeding methods, including
constant, intermittent, and exponential feeding methods, in fed-batch experiments. A simple feedback feeding method based
on pH was proposed to control pH and substrate concentration synchronously to enhance lactic acid production in fed-batch
culture. As the linear relationship between the consumption amounts of alkali and that of substrate was concluded during lactic
acid fermentation, the alkali and substrate in the feeding broth were mixed together proportionally. Thus, the concentration
of substrate could be controlled through the adjustment of pH automatically. In the fed-batch lactic acid fermentation with
Lactobacillus lactis-11 by this method, the residual glucose concentration in fermentation broth was controlled between 4.1 and 4.9 g L−1, and the highest concentration of lactic acid, maximum cell dry weight, volumetric productivity of lactic acid, and yield
were 96.3 g L−1, 4.7 g L−1, 1.9 g L−1 h−1, and 0.99 g lactic acid per gram of glucose, respectively, compared to 82.7 g L−1, 3.31 g L−1, 1.7 g L−1 h−1, and 0.92 g lactic acid per gram of glucose in batch culture. This feeding method was simple and easily operated and could
be feasible for industrial lactic acid production in the future. 相似文献
2.
Amereih S Meisel T Kahr E Wegscheider W 《Analytical and bioanalytical chemistry》2005,383(7-8):1052-1059
Speciation analysis of Sb(III) and Sb(V) in a soil sample was performed through extraction and on-line isotope dilution concentration
determination after a chromatographic separation. The total Sb concentration found in a through traffic contaminated soil
sample was (4.17 μg g−1, 0.3 μg g−1 SD, n=6). It was determined using ICP-MS after soil digestion using the sodium peroxide sintering method. The optimized extraction
procedure for speciation analysis was carried out using 100 mmol L−1 citric acid at pH 2.08 by applying an ultrasonic bath for 45 min at room temperature. The effects of citric acid concentration
(0–500 mmol L−1), pH (1–6), and temperature (30–60°C) on inorganic antimony species distribution in the examined sample were studied and
optimized. The separation of Sb(III) and Sb(V) was achieved using an anion exchange column (PRP-X100) and 10 mmol L−1 EDTA and 1 mmol L−1 phthalic acid at pH 4.5 as a mobile phase. The eluent from the HPLC was mixed with an enriched (94.2%) 123Sb spike solution that was pumped by a peristaltic pump with a constant flow rate (0.5 mL min−1) in a three-way valve. The blend passed directly to the Conikal nebulizer of the ICP-MS. By using the above extraction procedure
and methodology, 43.2% Sb(V) (2.9% RSD, n=3) and 6.0% Sb(III) (1.3% RSD, n=3) of total Sb found in the sample could be detected. The detection limits achieved by the proposed method were 20 ng L−1 and 65 ng L−1 for Sb(V) and Sb(III), respectively. The precision, evaluated by using RSD with 100 ng L−1 calibration solutions, was 2.7% and 3.2% (n=6) for Sb(V) and Sb(III), respectively, in aqueous solutions. 相似文献
3.
Determination of organic acids in air by capillary electrophoresis and ion-exclusion chromatography 总被引:2,自引:0,他引:2
Summary A capillary electrophoretic (CE) method for the determination of organic acids in the low ppm range is described. The buffer
consisted of 5 mM 2,6-pyridinedicarboxylic acid and 0.5 mM cetyltrimethylammonium bromide, pH 5.6. The former served as background
electrolyte for indirect UV detection at 200 nm, whereas the latter was used to reverse electroosmotic flow. In <5 min 8 low
molecular mass organic acids (oxalic, formic, malonic, glutaric, glycolic, acetic, lactic and propanoic) and two inorganic
acids (hydrochloric and sulphuric) were separated. Detection limits for anions tested were 0.04 mg L−1 (lactic acid) to 0.6 mg L−1 (malonic acid).
The method was applied to the determination of organic acids in air samples. The CE results when compared with ion-exclusion
chromatography (IEC) agreed well. The use of electrokinetic injection in CE proved beneficial for preconcentration of organic
acids in real samples. Using electrokinetic injection, preconcentration factors ranging from 14 (hydrochloric acid) to 3 (propanoic
acid) were obtained.
Presented at Balaton Symposium on High-Performance Separation Methods, Siófok, Hungary, September 1–3, 1999 相似文献
4.
Silva SG Morales-Rubio A de La Guardia M Rocha FR 《Analytical and bioanalytical chemistry》2011,401(1):365-371
A new procedure for spectrofluorimetric determination of free and total glycerol in biodiesel samples is presented. It is
based on the oxidation of glycerol by periodate, forming formaldehyde, which reacts with acetylacetone, producing the luminescent
3,5-diacetyl-1,4-dihydrolutidine. A flow system with solenoid micro-pumps is proposed for solution handling. Free glycerol
was extracted off-line from biodiesel samples with water, and total glycerol was converted to free glycerol by saponification
with sodium ethylate under sonication. For free glycerol, a linear response was observed from 5 to 70 mg L−1 with a detection limit of 0.5 mg L−1, which corresponds to 2 mg kg−1 in biodiesel. The coefficient of variation was 0.9% (20 mg L−1, n = 10). For total glycerol, samples were diluted on-line, and the linear response range was 25 to 300 mg L−1. The detection limit was 1.4 mg L−1 (2.8 mg kg−1 in biodiesel) with a coefficient of variation of 1.4% (200 mg L−1, n = 10). The sampling rate was ca. 35 samples h−1 and the procedure was applied to determination of free and total glycerol in biodiesel samples from soybean, cottonseed,
and castor beans. 相似文献
5.
Fernando Maya José Manuel Estela Víctor Cerdà 《Analytical and bioanalytical chemistry》2009,394(6):1577-1583
In this work, the hyphenation of the multisyringe flow injection analysis technique with a 100-cm-long pathlength liquid core
waveguide has been accomplished. The Cl−/Hg(SCN)2/Fe3+ reaction system for the spectrophotometric determination of chloride (Cl−) in waters was used as chemical model. As a result, this classic analytical methodology has been improved, minimizing dramatically
the consumption of reagents, in particular, that of the highly biotoxic chemical Hg(SCN)2. The proposed method features a linear dynamic range composed of two steps between (1) 0.2–2 and (2) 2–8 mg Cl− L−1, thus extended applicability due to on-line sample dilution (up to 400 mg Cl− L−1). It also presents improved limits of detection and quantification of 0.06 and 0.20 mg Cl− L−1, respectively. The coefficient of variation and the injection throughput were 1.3% (n = 10, 2 mg Cl− L−1) and 21 h−1. Furthermore, a very low consumption of reagents per Cl− determination of 0.2 μg Hg(II) and 28 μg Fe3+ has been achieved. The method was successfully applied to the determination of Cl− in different types of water samples. Finally, the proposed system is critically compared from a green analytical chemistry
point of view against other flow systems for the same purpose. 相似文献
6.
By alternate use of two different extraction solvents, n-hexadecane and benzyl alcohol, a headspace-solvent microextraction (HSME)–GC–FID/MS method has been established for characterization
of the volatile components of an orange juice beverage. The method avoids two disadvantages of conventional HSME—difficulty
identifying components obscured by the solvent peak and inefficient extraction of some of the compounds if one solvent only
is used. The optimum conditions (droplet volume, equilibration temperature and time, extraction time, and ionic strength)
were determined by the factor-rotation method. The volatile components of the beverage were mainly terpenes, terpenols, fatty
acids, and alcohols, for example limonene (114.71 mg L−1), phellandrene (4.50 mg L−1), terpineol (p-menth-1-en-8-ol; 3.12 mg L−1), α-pinene (0.33 mg L−1), n-hexadecanoic acid (0.28 mg L−1), and terpinol (0.13 mg L−1). 相似文献
7.
Determination of magnesium,calcium, sodium,and potassium in blood plasma samples by capillary zone electrophoresis 总被引:1,自引:0,他引:1
A capillary zone electrophoretic assay has been developed and validated for analysis of magnesium, calcium, sodium, and potassium
in blood plasma samples. Optimum results were obtained with 20 mmol L−1 imidazole (pH 2.8) and 0.5 mmol L−1 oxalic acid containing 5% methanol, capillary temperature 25°C, applied voltage 30 kV, hydrodynamic injection time 3 s, and
a poly(vinyl alcohol)-coated capillary (i.d. 50 μm, total length 64.5 cm and effective length 56 cm). Indirect detection was
performed at 214 nm. Cadmium was used as internal standard. The migration times of magnesium, calcium, sodium, and potassium
were 4.25, 3.79, 3.96, and 2.79 min, respectively. The method was applied to the determination of magnesium, calcium, sodium,
and potassium in blood plasma samples. The results were compared with those from atomic absorption spectrophotometry and no
statistically significant difference was found (P>0.05).
This study was supported by the Turkish Republic, Prime Ministry State Planning Organization (Project Number: 98K121730) 相似文献
8.
Panayot K. Petrov Jožica Majda Serafimovska Sonja Arpadjan Dimiter L. Tsalev Trajče Stafilov 《Central European Journal of Chemistry》2008,6(2):216-221
The influence of EDTA, carboxylic acids, amino-and hydroxocarboxylic acids, monosaccharides and humic substances on the generation
of arsines in hydride generation atomic absorption spectrometry (HGAAS) was investigated. EDTA (0.02 mol L−1), ascorbic acid (0.02 mol L−1) and glucose or fructose (0.2 mol L−1) are useful additives for levelling sensitivities for As(III), monomethylarsonate (MMA) and dimethylarsinate (DMA). The presence
of glycine, malonic, tartaric acids, BICIN and soil humin extracts leads to differences in analytical signal response between
these arsenic species. An analytical application to the determination of the sum of As(III), monomethylarsonate (MMA) and
dimethylarsinate (DMA) as well as the sum of toxicologically relevant hydride forming arsenic fraction As(III) + As(V) + MMA
+ DMA in EDTA soil/sediment extracts using continuous flow HGAAS was demonstrated. The limit of detection was 0.2 mg kg−1 As. Within-day and between-day precision were in the range 3–7% and 4–10%, respectively, for arsenic contents of 0.7–25 mg
kg−1, with recoveries 95–103%.
相似文献
9.
This paper reports silica gel loaded with p-tert-butylcalix[8]arene as a new solid phase extractor for determination of trace level of uranium. Effective extraction conditions
were optimized in column methods prior to determination by spectrophotometry using arsenazo(III). The results showed that
U(VI) ions can be sorbed at pH 6 in a mini-column and quantitative recovery of U(VI) (>95–98%) was achieved by stripping 0.4 mol L−1 HCl. The sorption capacity of the functionalized sorbent is 0.072 mmol uranium(VI) g−1 modified silica gel. The relative standard deviation and detection limit were 1.2% (n = 10) for 1 μg uranium(VI) mL−1 solution and 0.038 μg L−1, respectively. The method was employed to the preconcentration of U(VI) ions from spiked ground water samples. 相似文献
10.
George A. Zachariadis Anastasia I. Lyratzi John A. Stratis 《Central European Journal of Chemistry》2011,9(5):941-947
An efficient ion chromatographic (IC) method was developed for the simultaneous quantitative determination of Li+, Na+, NH4
+, K+, Cs+, Ca2+, Mg2+, Sr2+, Ba2+ and Be2+ in energy drinks, pharmaceutical and drinking water samples by non-suppressed conductometric detection. The separation of
ten cations including ammonium was achieved using a cation-exchange column and low conductivity mobile phase. The mobile phase
consisted of tartaric acid, dipicolinic acid and boric acid. The separation of the cations was completed in less than 18 min,
with a flow rate of 1.2 mL min−1. The separation was not affected by the existence of cations Co2+, Cr3+, Cd2+, Cu2+, Bi3+, Ag+, Fe3+ and Zn2+ in concentrations up to 20 mg L−1. Using an injection volume of 20 μL the obtained detection limits were 0.003 mg L−1, 0.02 mg L−1, 0.01 mg L−1, 0.01 mg L−1, 0.10 mg L−1, 0.01 mg L−1, 0.02 mg L−1, 0.02 mg L−1, 0.003 mg L−1 and 0.1 mg L−1, for Li+, Na+, NH4+, K+, Cs+, Ca2+, Mg2+, Sr2+, Be2+ and Ba2+ respectively. The intra-day repeatability (RSD%, n=5) ranged from 1.1% to 4.8%, and the inter-day (n=5) between 1.8% and
5.4% respectively. The method was applied to the analysis of various bottled and tap water, pharmaceutical preparations and
energy drinks commercially available.
相似文献
11.
Marta Pedrouzo Francesc Borrull Rosa Maria Marcé Eva Pocurull 《Analytical and bioanalytical chemistry》2010,397(7):2833-2839
Stir-bar-sorptive extraction (SBSE) with liquid desorption (LD) and ultra-high-performance liquid chromatography–electrospray
ionization triple-quadrupole tandem mass spectrometry (UHPLC–(ESI)MS–MS) were used for analysis of six personal care products
in environmental water: four UV filters (2,2-dihydroxy-4-methoxybenzophenone, benzophenone-3, octocrylene, and octyldimethyl-p-aminobenzoic acid) and two antimicrobial agents (triclocarban and triclosan). Experimental conditions that affect SBSE-LD
sorption efficiency (extraction time and temperature, sample pH, and ionic strength) and desorption efficiency (solvent, temperature,
and time) were optimized. The method proved to be sensitive—a 50-mL sample was used to determine these compounds in environmental
waters at trace levels. The detection limits of the analytical method were 2.5 ng L−1 for river water and 5–10 ng L−1 for effluent and influent sewage water. In river waters, benzophenone-3 was found at levels from 6 ng L−1 to 28 ng L−1 and triclosan at levels <LOQ. Benzophenone-3 was found between 75 and 127 ng L−1 in influent sewage, whereas concentrations of benzophenone-3 and triclosan were commonly below 25 ng L−1 in effluent sewage. 相似文献
12.
Nitrate ions were used as the oxidant in the cathode chamber of a microbial fuel cell (MFC) to generate electricity from organic
compounds with simultaneous nitrate removal. The MFC using nitrate as oxidant could generate a voltage of 111 mV (1,000 Ω)
with a plain carbon cathode. The maximum power density achieved was 7.2 mW m−2 with a 470 Ω resistor. Nitrate was reduced from an initial concentration of 49 to 25 mg (NO3−−N) L−1 during 42-day operation. The daily removal rate was 0.57 mg (NO3−–N) L−1 day−1 with a voltage generation of 96 mV. In the presence of Pt catalyst dispersed on cathode, the cell voltage was significantly
increased up to 450 mV and the power density was 117.7 mW m−2, which was 16 times higher than the value without Pt catalyst. Significant nitrate removal was also observed with a daily
removal rate of 2 mg (NO3−–N) L−1 day−1, which was 3.5 times higher compared with the operation without catalyst. Nitrate was reduced to nitrite and ammonia in the
liquid phase at a ratio of 0.6% and 51.8% of the total nitrate amount. These results suggest that nitrate can be successfully
used as an oxidant for power generation without aeration and also nitrate removal from water in MFC. However, control of the
process would be needed to reduce nitrate to only nitrogen gas, and avoid further reduction to ammonia. 相似文献
13.
Jiang L Wang J Liang S Wang X Cen P Xu Z 《Applied biochemistry and biotechnology》2010,160(2):350-359
Butyric acid has many applications in chemical, food, and pharmaceutical industries. In the present study, Clostridium tyrobutyricum ATCC 25755 was immobilized in a fibrous-bed bioreactor to evaluate the performance of butyrate production from glucose and
xylose. The results showed that the final concentration and yield of butyric acid were 13.70 and 0.46 g g−1, respectively, in batch fermentation when 30 g L−1 glucose was introduced into the bioreactor. Furthermore, high concentration 10.10 g L−1 and yield 0.40 g g−1 of butyric acid were obtained with 25 g L−1 xylose as the carbon source. The immobilized cells of C. tyrobutyricum ensured similar productivity and yield from repeated batch fermentation. In the fed-batch fermentation, the final concentration
of butyric acid was further improved to 24.88 g L−1 with one suitable glucose feeding in the fibrous-bed bioreactor. C. tyrobutyricum immobilized in the fibrous-bed bioreactor would provide an economically viable fermentation process to convert the reducing
sugars derived from plant biomass into the final bulk chemical (butyric acid). 相似文献
14.
Ying Xu Fei Wang Le Wang Fangyuan Zhao Baocheng Yang Baoxian Ye 《Journal of Solid State Electrochemistry》2012,16(4):1473-1480
A novel voltammetric sensor, based on single-walled carbon nanotubes (SWNT) dispersed in Nafion and modified glassy carbon
electrode (GCE), was fabricated and used to determine the trace amounts of dihydromyricetin (DMY). The electrochemical behavior
of DMY at this sensor was investigated in 0.1 mol L−1 sulfuric acid solutions + 0.1 mol L−1 NaCl by cyclic voltammetry and squarewave voltammetry. Compared with bare GCE, the electrode presented an excellent response
of DMY through an adsorption-controlled quasi-reversible process. Under the optimum conditions, the response peak currents
were linear relationship with the DMY concentrations in the range of 1.0 × 10−7–1.0 × 10−5 mol L−1 with a detection limit of 9 × 10−8 mol L−1. Based on this voltammetric sensor, a simple and sensitive electroanalytical method for DMY was proposed and applied to quantitative
determination of DMY in Ampelopsis grossedentata samples. In addition, the oxidation mechanism was proposed and discussed, which could be a reference for the pharmacological
action of DMY in clinical study. 相似文献
15.
Summary Capillary electrophoresis with amperometric detection has been evaluated for the simultaneous determination of rutin and quercetin.
The cyclic voltammogram, hydrodynamic voltammogram, and the effects of pH, concentration of buffer and sodium dodecyl sulfate
(SDS), and amount of organic modifier on the separation and the detection were studied. The optimized conditions were: detection
potential 1.2V, separation at 12 kV, 5 s at 15 kV for sample injection, running electrolyte 20 mmol L−1 borate buffer, pH 8.8, containing 40 mmol L−1 SDS and 10% acetonitrile. The detection limit of the method was low, 0.001 and 0.0005 mg mL−1, for rutin and quercetin, respectively; the linear ranges were wide −0.005–0.5 and 0.005–0.4 mg mL−1, respectively. The variations in peak current and migration time for eight consecutive injections of a standard solution
containing 0.1 mg mL−1 of each compound were 4.78 and 3.63%, and 6.50 and 2.59% for rutin and quercetin, respectively. The levels of the two compounds
in traditional Chinese herbal drugs were easily determined. 相似文献
16.
Phenolic acids and derivatives of quercetin in Indian (amla) and European gooseberry were determined by high-performance liquid
chromatography with diode array detector. The calibration curves were constructed using phenolic compounds standards (the
coefficient of determination (R
2) was 0.9990–0.9997 for phenolic acids and 0.9989–0.9994 for flavonols, respectively). The lowest detection limit was 0.28
mg L−1 and 0.35 mg L−1 for hyperoside and gallic acid, respectively, whereas the highest was 1.80 mg L−1 and 7.98 mg L−1 for quercetin and chlorogenic acid, respectively. The quantification limits calculated were 0.85–24.04 mg L−1 for hyperoside and chlorogenic acid, respectively. The predominant phenolic acid in amla and gooseberry is gallic acid: (5.37
± 0.04) mg per 100 g of dry mass (d.m.) and (3.21 ± 0.03) mg per 100 g of d.m., respectively. The next one was caffeic acid,
0.65–1.22 mg per 100 g of d.m., followed by p-coumaric acid, 0.84–1.17 mg per 100 g of d.m. Out of the flavonols, rutin is predominant: (3.11 ± 0.13) mg per 100 g of d.m.
and (2.12 ± 0.03) mg per 100 g of d.m., respectively. Anti-oxidant activity was also determined. 相似文献
17.
Mangal S. Rathore J. Chikara N. S. Shekhawat 《Applied biochemistry and biotechnology》2011,163(7):860-868
Aloe vera L., a member of Liliaceae, is a medicinal plant and has a number of curative properties. We describe here the development
of tissue culture method for high-frequency plantlet regeneration from inflorescence axis-derived callus cultures of sweet
aloe genotype. Competent callus cultures were established on 0.8% agar-gelled Murashige and Skoog’s (MS) basal medium supplemented
with 6.0 mg l−1 of 2,4-dichlorophenoxyacetic acid (2,4-D) and 100.0 mg l−1 of activated charcoal and additives (100 mg l−1 of ascorbic acid, 50.0 mg l−1 each of citric acid and polyvinylpyrrolidone, and 25.0 mg l−1 each of l-arginine and adenine sulfate). The callus cultures were cultured on MS medium containing 1.5 mg l−1 of 2,4-D, 0.25 mg l−1 of Kinetin (Kin), and additives with 4% carbohydrate source for multiplication and long-term maintenance of regenerative
callus cultures. Callus cultures organized, differentiated, and produced globular embryogenic structures on MS medium with
1.0 mg l−1 of 2,4-D, 0.25 mg l−1 of Kin, and additives (50.0 mg l−1 of ascorbic acid and 25.0 mg l−1 each of citric acid, l-arginine, and adenine sulfate). These globular structures subsequently produced shoot buds and then complete plantlets on
MS medium containing 1.0 mg l−1 of 6-benzylaminopurine and additives. A hundred percent regenerated plantlets were hardened in the greenhouse and stored
under an agro-net house/nursery. The regeneration system defined could be a useful tool not only for mass-scale propagation
of selected genotype of A. vera, but also for genetic improvement of plant species through genetic transformation. 相似文献
18.
Ainara Barriola José I. Miranda Miren Ostra Carlos Ubide 《Analytical and bioanalytical chemistry》2010,398(2):1085-1094
The use of proton nuclear magnetic resonance (1H-NMR) for the quantification of additives in an electrolytic Zn bath is reported. A simple and quick method is described
that does not need any prior sample preparation. Contrary to other analytical methods, the three additives in the bath, benzylidene
acetone (BDA), benzoic acid (BA) and poly(ethylene glycol) (PE400), can be quantified. Two calibration methods were tried:
integration of NMR signals with the use of an internal standard and partial least squares (PLS) regression applied to the
characteristic NMR peaks. Both methods are compared and the univariate method was preferred because of simplicity, accuracy
and precision. The following limits of detection were found: 0.30 g L−1 BA, 0.08 g L−1 BDA and 0.7 g L−1 PE400 with dynamic ranges of at least 1.0–6.0, 0.1–0.6 and 3.0–18.0 g L−1 respectively. Those concentration ranges are suitable to follow the concentration of additives in the bath in real time.
1H-NMR spectra provide evidence for the BDA degradation pattern. 相似文献
19.
Gang Li Suling Yang Lingbo Qu Ran Yang Jianjun Li 《Journal of Solid State Electrochemistry》2011,15(1):161-166
A Nafion/multi-wall carbon nanotubes (MWNT) composite film-modified electrode was fabricated. The modified electrode showed
excellent electrocatalytic activity toward ascorbic acid (AA) and uric acid (UA) in 0.1-mol L−1 NaCl medium (pH 6.5). Compared to the bare electrode that only displayed a broad and overlapped oxidation peak, the Nafion/MWNT
film-modified electrode not only remarkably enhanced the anodic peak currents of AA and UA but also avoided the overlapping
of the anodic peaks of AA and UA with a 320-mV separation of both peaks. Under the optimized conditions, the peak currents
of AA and UA were proportional to their concentration at the ranges of 8.0 × 10−5 to 6.0 × 10−3 mol L−1 and 6.0 × 10−7 to 8.0 × 10−5 mol L−1, respectively. The proposed method was used for the detection of AA and UA in real samples with satisfactory results. 相似文献
20.
García-Galán MJ Garrido T Fraile J Ginebreda A Díaz-Cruz MS Barceló D 《Analytical and bioanalytical chemistry》2011,399(2):795-806
The present study describes an automated methodology based on a liquid chromatography-electrospray, tandem mass spectrometry
method combined with online solid phase extraction (online SPE-LC-ESI-MS/MS) for the simultaneous analysis of 16 sulfonamides
(SAs) and five of their acetylated metabolites in groundwater. The evaluation of the degree of SA pollution in groundwater
was made through the analysis of a total of 39 samples taken in seven groundwater bodies of Catalonia (Spain). Recovery values
obtained ranged from 34.3% (N
4-acetylsulfadiazine) to 134.4% (sulfabenzamide). The method limits of detection for all the analytes were 0.09–11 ng L−1. Sulfamethoxazole was the SA detected more frequently (56.4% of the samples), with an average concentration of 2.3 ng L−1, followed by sulfadimethoxine, present in 54% of the samples with an average concentration of 0.2 ng L−1. It should be highlighted that the acetylated metabolites were ubiquitous in the different samples, with frequencies of detection
up to 36% and maximum concentrations of 18 ng L−1 (N
4-acetylsulfamerazine). 相似文献