Journal of Analytical Methods in Chemistry

Journal of Analytical Methods in Chemistry / 2019 / Article

Research Article | Open Access

Volume 2019 |Article ID 3201370 | 9 pages | https://doi.org/10.1155/2019/3201370

Quantitative Characteristics of Toxic Compounds According to the Solvent Type

Academic Editor: Paolo Montuori
Received30 Sep 2018
Accepted24 Mar 2019
Published30 Apr 2019

Abstract

The quantitative analysis of target substances is an important part of assessing the toxicity of diverse materials. Usually, the quantitation of target compounds is conducted by instrumental analysis such as chromatography and capillary electrophoresis. If solvents are used in the pretreatment step of the target analyte quantification, it would be crucial to examine the solvent effect on the quantitative analysis. Therefore, in this study, we assessed the solvent effects using four different solvents (methanol, hexane, phosphate buffered saline (PBS), and dimethyl sulfoxide (DMSO)) and three toxic compounds (benzene, toluene, and methylisothiazolinone (MIT)). Liquid working standards containing the toxic compounds were prepared by dilution with each solvent and analyzed by gas chromatography-mass spectrometry (GC-MS). As a result, we found that the response factor (RF) values of the target analytes were different, depending on the solvent types. In particular, benzene and toluene exhibited their highest RF values (33,674 ng−1 and 78,604 ng−1, respectively) in hexane, while the RF value of MIT was the highest (9,067 ng−1) in PBS. Considering the correlation (R2) and relative standard deviation (RSD) values, all target analytes showed fairly good values (R2 > 0.99 and RSD < 10%) in methanol and DMSO. In contrast, low R2 (0.0562) and high RSD (10.6%) values of MIT were detected in hexane, while benzene and toluene exhibited relatively low R2 and high RSD values in PBS (mean R2 = 0.9892 ± 0.0146 and mean RSD = 13.3 ± 4.1%). Based on these findings, we concluded that the results and reliability of the quantitative analysis change depending on the analyte and solvent types. Therefore, in order to accurately assess the toxicity of target compounds, reliable analytical data should be obtained, preferentially by considering the solvent types.

1. Introduction

Chemical products that are generally used to clean, sanitize, and disinfect are widely employed in our living environments. However, several of these are known to contain toxic compounds, which can damage the human health and natural environment [1, 2]. Due to their hazardous properties, these chemicals are usually regulated through a toxicology analysis such as safety assessment and toxicity testing [3]. In the toxicity testing, the accurate exposure of target chemicals to experimental animals or cells is important. As such, the stability of target chemicals should first be evaluated and ensured, the latter of which is commonly performed with the use of solvents [4, 5]. In case of the U.S. Environmental Protection Agency, the use of acetone, dimethylformamide (DMF), dimethyl sulfoxide (DMSO), and methanol as solvents is recommended for toxicity tests on aquatic invertebrates [6].

In general, a variety of solvents have been used to performing toxicity test [7, 8]. For example, in the case of an inhalation toxicity testing, solvents are mainly used for the sample extraction, absorption, and dilution steps. More specifically, if the filter sampling is conducted, the inhalable samples are first collected by filters (i.e., glass, quartz, or Teflon filters), after which the samples loaded on the filters are extracted and diluted by solvents [912]. Solvents are also used as the absorption solution to collect directly the inhalable samples [13]. In contrast, in the case of a cytotoxicity test, solvents are used for the storage and extraction of target analytes from cells [14, 15]. For this purpose, phosphate buffered saline (PBS) has been recommended as a suitable buffer solution to maintain the appropriate pH for cell storage [16, 17]. In addition, DMSO can be used as a sample extractant and cryoprotectant of cultured cells in biochemistry and cell biology [18].

Reportedly, the calibration results of target compounds can differ depending on the solvent effect due to the use of liquid samples [19, 20]. For example, Campos et al. [21] examined the reaction of an imidazole derivative with organic solvents by analyzing the imidazole samples derivatized from diethyl 2,4-dinitrophenyl phosphate and DMSO or distilled water as a solvent. As a result, they found that the imidazole derivative reaction increases in DMSO and decreases in distilled water, which indicates that the reactivity of derivation is different depending on the solvent type and that the reliability results can affect the quantitative analysis.

In this study, we investigated the solvent effect of toxic compounds in relation to their calibration characteristics. Methanol (MeOH), hexane, PBS, and DMSO, which are commonly used in the chemical and biological analysis, were selected as target solvents, while benzene, toluene, and methylisothiazolinone (MIT) were selected as target analytes (Table 1). From these, benzene and toluene are generally identified as carcinogenic, as they have the potential to damage the generative functions in humans upon transmission [22], whereas MIT is commonly known as the main component in humidifier disinfectants. The standard solutions containing the target analytes and solvents were analyzed using a gas chromatography (GC) equipped with a mass spectrometry (MS), which provided the calibration data to assess the solvent effects.


Chemical groupFull nameShort nameMolecular formulaMolecular weight (g·mol−1)Density (g·mL−1)m/zaCAS numberChemical structure

Target compoundBenzeneC6H678.110.8747871-43-2
TolueneC6H5CH392.1410.8679150643-04-4
MethylisothiazolinoneMITC4H5NOS115.11.351152682-20-4

Solvent compoundMethanolMeOHCH3OH32.040.7923167-56-1
HexaneC6H1486.180.660657110-54-3
Phosphate buffered salinePBSCl2H3K2Na3O8P2411.0290.0648NANA
Dimethyl sulfoxideDMSOC2H6OS78.131.100445,63,7867-68-5

aMain spectra of the target compounds. NA, not available.

2. Materials and Methods

2.1. Preparation of the Working Standards (WSs)

A total of three target compounds (benzene, toluene, and MIT) and four solvents (MeOH, hexane, PBS, and DMSO) were selected to investigate the solvent effect. WSs of these three target compounds were prepared in the same way using each solvent. Reagent grade chemicals (RGCs) were purchased at ≥95% purity: (1) 99.5% (benzene and toluene), (2) 95% (MIT), and (3) 99.9% (MeOH, hexane, and DMSO) (Sigma-Aldrich, USA). PBS (1x, pH 7.4, Gibco BRL) was purchased from Life Technologies (Frederick, MD, USA). Primary standards (PSs) were prepared (PS-1 and PS-2) by mixing the RGCs with benzene and toluene or with MIT, respectively, with concentrations of 8,736 ng·μL−1 (benzene), 8,627 ng·μL−1 (toluene), and 90,000 ng·μL−1 (MIT). The first working standards (1st-WSs) were prepared by mixing 100 μL of PS-1 and PS-2 each and 1800 μL of the respective solvent in a 2 mL vial, resulting in final concentrations (ng·μL−1) of 416 (benzene), 411 (toluene), and 4,286 (MIT). Four different solvents were used to form the 1st-WSs: MeOH (1st-WS-M), hexane (1st-WS-H), PBS (1st-WS-P), and DMSO (1st-WS-D). The final working standards (F-WS-M, F-WS-H, F-WS-P, and F-WS-D) for the five-point calibrations were prepared by diluting each 1st-WS with the respective solvent to prepare five different concentrations: (1) benzene: 8.32, 20.8, 41.6, 83.2, and 208 ng·μL−1, (2) toluene: 8.22, 20.5, 41.1, 82.2, and 205 ng·μL−1, and (3) MIT: 85.7, 214, 429, 857, and 2,143 ng·μL−1 (Figure 1(a)). Detailed information on the preparation of the WSs is shown in Table 2.


(a) Reagent grade chemical (RGC)
Compound nameBenzeneTolueneMIT
Concentration (%)99.599.595
Density (g·mL−1)0.8780.8671.35

(b-1) The first primary standard (PS-1)
CompoundBenzeneTolueneMeOH
Volume (μL)20201,960
Dilution fraction0.0100.010
Concentration (ng·μL−1)8,7368,627

(b-2) The second primary standard (PS-2)
CompoundMIT
Mass (mg)180
Volume (mL)2.000
Concentration (ng·μL−1)90,000

(c) The first working standard (WS)
Working standardPS-1PS-2Solventa
CompoundBenzeneTolueneMIT
Volume (μL)1001001,800
Dilution fraction0.050.05
Concentration (ng·μL−1)4164114,286

(d) The final working standard at 5 concentration levels
OrderMixing volume (μL)Dilution fractionConcentration (ng·μL−1)
1st L-WSSolventBenzeneTolueneMIT
1401,9600.0208.328.2285.7
21001,9000.05020.820.5214
32001,8000.10041.641.1429
44001,6000.2083.282.2857
51,0001,0000.502082052,143

aFour solvents were used in this study: (1) MeOH, (2) DMSO, (3) hexane, and (4) PBS.
2.2. Instrumental System

A GC (GC-2010, Shimadzu, Japan) equipped with an MS (GCMS-QP2010 ultra, Shimadzu, Japan) was employed to quantify the toxic compounds in the solvents (Figure 1(b)). Since the F-WSs contained different solvents, the calibration characteristics of the toxic compounds according to the solvent effects were assessed.

In the analysis, 1 µL samples from the F-WSs were injected into the GC injector (at 250°C) using the autosampler (AOC-5000, Shimadzu, Japan). The target analytes were then transferred to the Rtx-5MS column (diameter: 0.25 mm, length: 60 m, and thickness: 0.25 µm, Restek Corporation, USA) for separation using a carrier gas (He > 99.999%, flow rate of 2.41 mL·min−1 (constant flow)). The oven temperature of the GC was initially set to 40°C for 4 min, after which it was ramped at 15°C·min−1 to 145°C, and finally ramped at 70°C·min−1 to 285°C, thereby giving a total run time of 13 min.

The target analytes separated by the GC system were then detected by the MS system. Both the interface and ion source temperatures were set to 250°C. The target analytes were quantified in a total ion chromatogram (TIC) mode in a mass range of 30–500 m/z. Extracted ion chromatographic (EIC) mode was subsequently applied to the minimized interfaces using significant ions identified from the spectrum of each target analyte (Table 1). Detailed setting information of the analysis instrument is presented in Table 3.


(a) Carrier gas settings
Injection temperature250°C
Injection modeSplit
Carrier gasHelium (>99.999%)
Pressure132.9kPa
Column flow2.41mL·min−1 (constant flow)
Purge flow3.0mL·min−1
Split ratio20

(b) Gas chromatography (model: GC-2010, Shimadzu, Japan)
ColumnRtx-5MS (Shimadzu, Japan)
(length: 60 m, diameter: 0.25 nm, and film thickness: 0.25 μm)
Oven setting40°C (4 min) ⟶ 145°C (15°C/min) ⟶ 285°C (70°C/min)
(Total program time = 13 min)

(c) Mass spectrometry (model: GCMS-QP2010 ultra, Shimadzu, Japan)
Ionization modeEI (70 eV)
Ion source temperature250°C
Interface temperature250°C
TIC30∼500m/z
Scan speed1000

3. Result and Discussion

3.1. Calibration Characteristics of the Toxic Compounds According to the Solvent Type

The calibration results of the target analytes obtained by GC-MS analysis were provided in terms of the response factor (RF, ng−1), coefficient of determination (R2), relative standard error (RSD, %), and limit of detection (LOD, ng) (Table 4).


SolventFactorsTarget compound
BenzeneTolueneMIT

MeOHRF (ng−1)26,16443,6187,877
N-RFa (ng−1/ng−1)0.790.550.87
R20.99780.99840.9994
RSD (%)0.830.725.56
LOD (ng)0.020.010.07

HexaneRF (ng−1)33,67478,6041,117
N-RF (ng−1/ng−1)110.12
R20.96300.99690.0562
RSD (%)4.222.3510.6
LOD (ng)0.010.000.18

PBSRF (ng−1)11,28621,0269,067
N-RF (ng−1/ng−1)0.340.271
R20.97880.98010.9997
RSD (%)16.214.62.41
LOD (ng)0.010.010.01

DMSORF (ng−1)31,93260,1478,148
N-RF (ng−1/ng−1)0.950.770.90
R20.99840.99950.9998
RSD (%)7.6910.46.19
LOD (ng)0.020.010.08

aNormalized-RF (N-RF): RF value/maximum RF among four different solvents.

Notably, the RF value of each target analyte was different, depending on the solvent type. The obtained RF values were normalized against the highest RF value in the following way: normalized-RF (N-RF) = RF/RF(max) (Table 4). Benzene and toluene had relatively high N-RF values (above 0.77) in hexane and DMSO, while in PBS (highly polar solvent), their N-RF values were significantly lower (0.34 and 0.27, respectively). In contrast, MIT exhibited the highest N-RF value in PBS (N-RF = 1), whereas in hexane, the N-RF value of MIT was low (N-RF = 0.12).

The calibration results derived in terms of R2 and RSD (%) were similar to the patterns observed in the RF values (Figure 2). In particular, the R2 values of benzene, toluene, and MIT in MeOH and DMSO were fairly high (>0.99). In MeOH, the RSD values of all target compounds exhibited the best reproducibility (below 6% for all target analytes), while in DMSO, the RSD values were slightly higher (mean RSD () = 8.09 ± 2.13%). When PBS and hexane were used as solvents, the R2 and RSD values of the target compounds differed upon changing the solvent types. In hexane, the R2 values of benzene and toluene exhibited a strong linearity (>0.96), while that of MIT was low (0.0562). Also, benzene and toluene showed good RSD values in hexane (<5%), whereas MIT had a high RSD (10.6%). In contrast, the RSD and R2 values when PBS was used as a solvent were contrary to those obtained in the case of hexane. In particular, the R2 and RSD values of MIT in PBS were 0.9997 and 2.41%, respectively, while the RSD values of benzene and toluene showed low reproducibility with above 14%. The LOD values of all target analytes were below 0.18 ng, which is sufficient to detect the lowest calibration points of all the types of final working standards (F-WSs) (Table 4).

Based on these results, we concluded that the instrument responsivity and reproducibility of the target compounds differed, depending on their physicochemical properties. Moreover, the responsivity and analytical reliability was found to be especially affected by the solvent type. Therefore, in order to achieve an accurate quantitation, it is important to select the solvent by considering the physicochemical properties (i.e., polarity) of the target analytes.

3.2. Comparison of Previous Research Data

Diverse solvents have been previously used in chemical and biological analyses for the pretreatment of target samples and the preparation of standard solutions. In this study, we confirmed that the calibration results were different depending on the solvent type, although the same target compounds were analyzed by the same analytical methods. However, many researchers do not fully consider the solvent effect in their quantitative analyses (Table 5).


OrderField of scienceTarget compound or materialPretreatment or standard solventSample solventInstrument or assay methodaReference

1Chemistry13 aldehydes and 4 ketonesWater and acetonitrileWater and methanolHPLC-UVBrandão et al. [23]
2Formaldehyde in bovine milkUltrapure waterAcetonitrileHPLC-UVRezende et al. [24]
3Sodium ferrocyanide in 801 Salt0.02 M NaOH0.02 M NaOHHPLC-UVLim et al. [25]

4BiologyGinkgo biloba L. (EGB)MethanolIsopropanol-ethanol-water (3 : 2 : 1)HPLC-UV/DAD/MSYang et al. [26]
5Vitamin C (ascorbic acid and dehydroascorbic acid)10% meta-phosphoric acid10% meta-phosphoric acidHPLC or UPLCKlimczak & Gliszczyńska-Świgło [27]
6Sugars content in sunflower oil0.005 N H2SO4Ethanol and distilled waterHPLCBaumler et al. [28]
737 raw vegetablesAcetone, methanol, ethanol, and distilled water2,2-Diphenyl-1-picrylhydrazyl (DPPH) in ethanolDPPH free radical scavenging assaySulaiman et al. [29]
Distilled waterTotal phenolic content

aHPLC, high-performance liquid chromatography; UV, ultraviolet/visible; DVD, diode array detection; UPLC, ultraperformance liquid chromatography.

For example, Rezende et al. [24] analyzed formaldehyde in bovine milk using high-performance liquid chromatography-ultraviolet/visible (HPLC-UV) by employing ultrapure water as a standard solvent and acetonitrile as a sample solvent. Moreover, Baümler et al. [28] analyzed sugars in sunflower oil samples using HPLC by extracting them with ethanol and subsequently diluting the samples with distilled water. Additionally, a 0.005 N H2SO4 solution was used as a standard solvent. In both of these cases, there could be a quantitative error due to the solvent difference between the standards and samples.

Furthermore, there are also studies that use the same solvent for both standard and sample preparation. For instance, Lim et al. [25] analyzed ferrocyanide ions using HPLC-UV by employing the same solvent (0.02 M NaOH solution) for the preparation of the standard solution and pretreatment of the sample. In addition, Klimczak and Gliszczyńska-Świgło [27] quantified vitamin C (ascorbic acid and dehydroascorbic acid) using HPLC and ultraperformance liquid chromatography (UPLC) systems by using 10% meta-phosphoric acid solvent to both extract the samples and dilute the standard solutions. In both of these cases, the solvent effects could be minimized by using the same solvent for the quantitative analysis.

4. Conclusion

In order to conduct a toxicity testing, one needs to be able to obtain reliable quantitation data of the target toxic compounds. In this study, we assessed the effect of the solvent type on the quantitative results by analyzing three toxic compounds using four different solvents. Benzene, toluene, and MIT, which are well-known toxic compounds, were selected as target analytes. Liquid working standards of the target analytes were prepared using four different solvents (MeOH, hexane, PBS, and DMSO), which are commonly used for extraction and dilution of sample solutions. These working standards were analyzed using GC-MS, thereby providing the calibration results of the target compounds according to the solvent type. The solvent effect was then assessed by comparing these results (Figure 3). The RF values of nonpolar compounds (benzene and toluene) were the highest (33,674 ng−1 (benzene) and 78,604 ng−1 (toluene)) in nonpolar solvents such as hexane and the lowest (11,286 ng−1 (benzene) and 21,026 ng−1 (toluene)) in the polar solvent such as PBS. Unlike benzene and toluene, MIT had the highest RF value (9,067 ng−1) in a polar solvent (PBS), while it dropped dramatically to 1,117 ng−1 in a nonpolar solvent (hexane). Additionally, in MeOH, all target compounds showed fairly good reproducibilities with RSDs below 6% and linearity above 0.99. In contrast, hexane induced a low R2 value of MIT (0.0562), and PBS led to high RSD values of benzene and toluene (above 14%).

All in all, the results of this study confirmed that the quantitative results were affected by the solvent effect. Since quantitative results can differ depending on the solvent type, it is important to select the solvent by considering the physicochemical properties (i.e., polarity) of the target compounds. In addition, the use of different solvents in the quantitative analysis, such as in the extraction and dilution processes, could lead to difficulties in obtaining reliable quantitative data.

Data Availability

The data used to support the findings of this study are included within the article.

Conflicts of Interest

The authors declare that they have no conflicts of interest.

Acknowledgments

This work was supported by the Korea Institute of Toxicology, Republic of Korea (KK-1803 and KK-1904).

References

  1. D. Lithner, Å. Larsson, and G. Dave, “Environmental and health hazard ranking and assessment of plastic polymers based on chemical composition,” Science of the Total Environment, vol. 409, no. 18, pp. 3309–3324, 2011. View at: Publisher Site | Google Scholar
  2. I. Silins and J. Högberg, “Combined toxic exposures and human health: biomarkers of exposure and effect,” International Journal of Environmental Research and Public Health, vol. 8, no. 12, pp. 629–647, 2011. View at: Publisher Site | Google Scholar
  3. R. Kroes, C. Galli, I. Munro et al., “Threshold of toxicological concern for chemical substances present in the diet: a practical tool for assessing the need for toxicity testing,” Food and Chemical Toxicology, vol. 38, no. 2-3, pp. 255–312, 2000. View at: Publisher Site | Google Scholar
  4. G. E. Walsh, “Principles of toxicity testing with marine unicellular algae,” Environmental Toxicology and Chemistry, vol. 7, no. 12, pp. 979–987, 1988. View at: Publisher Site | Google Scholar
  5. S. Zhang, S. Ali, Y. Kong et al., “Evolution of chemical structure of polydichlorophosphazene in various solvents and ways to prolong its stability,” Journal of Molecular Liquids, vol. 225, pp. 536–543, 2017. View at: Publisher Site | Google Scholar
  6. B. Quinn, R. Gagne, and C. Blaise, “An investigation into the acute and chronic toxicity of eleven pharmaceuticals (and their solvent) found in wastewater effluent on the cnidarian, Hydra attenuata,” Science of The Total Environment, vol. 389, no. 2-3, pp. 306–314, 2008. View at: Publisher Site | Google Scholar
  7. B.-S. Kim, Y.-K. Park, Y.-J. Yang et al., “Comparison of toxic response of cladocerans to organic solvents to establish the standard test guidelines using Korean native species,” The Korean Journal of Pesticide Science, vol. 14, no. 1, pp. 10–15, 2010. View at: Google Scholar
  8. J. L. Pereira, S. C. Antunes, B. B. Castro et al., “Toxicity evaluation of three pesticides on non-target aquatic and soil organisms: commercial formulation versus active ingredient,” Ecotoxicology, vol. 18, no. 4, pp. 455–463, 2009. View at: Publisher Site | Google Scholar
  9. K.-H. Chang, J.-M. Park, C. H. Lee et al., “NADPH oxidase (NOX) 1 mediates cigarette smoke-induced superoxide generation in rat vascular smooth muscle cells,” Toxicology in Vitro, vol. 38, pp. 49–58, 2017. View at: Publisher Site | Google Scholar
  10. S. J. Choi, S. H. Lee, S. J. Lee, M. J. Yang, and K. Lee, “Subchronic inhalation toxicity study of 3R4F reference cigarette smoke in rats,” Molecular & Cellular Toxicology, vol. 12, no. 3, pp. 313–325, 2016. View at: Publisher Site | Google Scholar
  11. G. L. Baker, A. Gupta, M. L. Clark et al., “Inhalation toxicity and lung toxicokinetics of C60 fullerene nanoparticles and microparticles,” Toxicological Sciences, vol. 101, no. 1, pp. 122–131, 2008. View at: Publisher Site | Google Scholar
  12. Y.-S. Yang, J.-T. Kwon, I. Shim et al., “Evaluation of toxicity to triclosan in rats following 28 days of exposure to aerosol inhalation,” Regulatory Toxicology and Pharmacology, vol. 71, no. 2, pp. 259–268, 2015. View at: Publisher Site | Google Scholar
  13. J.-H. Lee, H.-J. Kang, H.-S. Seol et al., “Refined exposure assessment for three active ingredients of humidifier disinfectants,” Environmental Engineering Research, vol. 18, no. 4, pp. 253–257, 2013. View at: Publisher Site | Google Scholar
  14. K.-I. Lee, J.-H. Cho, and B.-S. Pyo, “Cytotoxicity and antioxidative activity of Artemisiae argi folium alcoholic extracts and their fractions,” Korean Journal of Medicinal Crop Science, vol. 19, no. 6, pp. 421–425, 2011. View at: Publisher Site | Google Scholar
  15. B. Boonkaew, M. Kempf, R. Kimble, and L. Cuttle, “Cytotoxicity testing of silver-containing burn treatments using primary and immortal skin cells,” Burns, vol. 40, no. 8, pp. 1562–1569, 2014. View at: Publisher Site | Google Scholar
  16. K. Reineke, R. Sevenich, C. Hertwig et al., “Comparative study on the high pressure inactivation behavior of the Shiga toxin-producing Escherichia coli O104:H4 and O157:H7 outbreak strains and a non-pathogenic surrogate,” Food Microbiology, vol. 46, pp. 184–194, 2015. View at: Publisher Site | Google Scholar
  17. T. Hovav, S. Yedgar, N. Manny, and G. Barshtein, “Alteration of red cell aggregability and shape during blood storage,” Transfusion, vol. 39, no. 3, pp. 277–281, 1999. View at: Publisher Site | Google Scholar
  18. H. Kim, Y. M. Cho, Y.-G. Seong, and H.-H. Seong, “Effects of acetamide and lactamide on the viability of frozen-thawed mammalian cells,” Journal of Life Science, vol. 24, no. 11, pp. 1252–1257, 2014. View at: Publisher Site | Google Scholar
  19. M.-H. Lee and K.-H. Kim, “A study of calibration bias in the analysis of airborne carbonyl compounds between gaseous and liquid-phase standards by high performance liquid chromatography (HPLC),” Journal of Korean Society for Atmospheric Environment, vol. 28, no. 1, pp. 52–58, 2012. View at: Publisher Site | Google Scholar
  20. M. A. Ullah, K.-H. Kim, J. E. Szulejko, and D. W. Choi, “Quantitative approaches for the determination of volatile organic compounds (VOC) and its performance assessment in terms of solvent types and the related matrix effects,” Asian Journal of Atmospheric Environment, vol. 11, no. 1, pp. 1–14, 2017. View at: Publisher Site | Google Scholar
  21. R. B. Campos, E. H. Santos, A. R. M. Oliveira et al., “Reactivity of imidazole derivatives toward phosphate triester in DMSO/water mixtures: a comprehensive study on the solvent effect,” The Journal of Organic Chemistry, vol. 80, no. 15, pp. 7572–7580, 2015. View at: Publisher Site | Google Scholar
  22. R. Bono, E. Scursatone, T. Schilirò, and G. Gilli, “Ambient air levels and occupational exposure to benzene, toluene, and xylenes in northwestern Italy,” Journal of Toxicology and Environmental Health, Part A, vol. 66, no. 6, pp. 519–531, 2003. View at: Publisher Site | Google Scholar
  23. P. F. Brandão, R. M. Ramos, P. J. Almeida, and J. A. Rodrigues, “Determination of carbonyl compounds in cork agglomerates by GDME-HPLC-UV: identification of the extracted compounds by HPLC-MS/MS,” Journal of Agricultural and Food Chemistry, vol. 65, no. 5, pp. 1037–1042, 2017. View at: Publisher Site | Google Scholar
  24. F. B. d. F. Rezende, A. M. d. S. S. Cheibub, A. D. P. Netto, and F. F. d. C. Marques, “Determination of formaldehyde in bovine milk using a high sensitivity HPLC-UV method,” Microchemical Journal, vol. 134, pp. 383–389, 2017. View at: Publisher Site | Google Scholar
  25. H. S. Lim, J. Y. Hwang, E. Choi et al., “Development and validation of HPLC method for the determination of ferrocyanide ion in food grade salts,” Food Chemistry, vol. 239, pp. 1167–1174, 2018. View at: Publisher Site | Google Scholar
  26. J. Yang, A.-Q. Wang, X.-j. Li, X. Fan, S.-S. Yin, and K. Lan, “A chemical profiling strategy for semi-quantitative analysis of flavonoids in Ginkgo extracts,” Journal of Pharmaceutical and Biomedical Analysis, vol. 123, pp. 147–154, 2016. View at: Publisher Site | Google Scholar
  27. I. Klimczak and A. Gliszczyńska-Świgło, “Comparison of UPLC and HPLC methods for determination of vitamin C,” Food Chemistry, vol. 175, pp. 100–105, 2015. View at: Publisher Site | Google Scholar
  28. E. R. Baümler, M. E. Carrín, and A. A. Carelli, “Extraction of sunflower oil using ethanol as solvent,” Journal of Food Engineering, vol. 178, pp. 190–197, 2016. View at: Publisher Site | Google Scholar
  29. S. F. Sulaiman, A. A. B. Sajak, K. L. Ooi, Supriatno, and E. M. Seow, “Effect of solvents in extracting polyphenols and antioxidants of selected raw vegetables,” Journal of Food Composition and Analysis, vol. 24, no. 4-5, pp. 506–515, 2011. View at: Publisher Site | Google Scholar

Copyright © 2019 Young-Ji An et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


More related articles

782 Views | 323 Downloads | 0 Citations
 PDF  Download Citation  Citation
 Download other formatsMore
 Order printed copiesOrder

Related articles

We are committed to sharing findings related to COVID-19 as quickly and safely as possible. Any author submitting a COVID-19 paper should notify us at help@hindawi.com to ensure their research is fast-tracked and made available on a preprint server as soon as possible. We will be providing unlimited waivers of publication charges for accepted articles related to COVID-19. Sign up here as a reviewer to help fast-track new submissions.