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Method development for the identification and quantitative analysis of seven nitrosamines using gas chromatography mass spectrometry
Chemical Data Collections 21 (2019) 100231
Contents lists available at ScienceDirect
Chemical Data Collections journal homepage: www.elsevier.com/locate/cdc
Data Article
Method development for the identification and quantitative analysis of seven nitrosamines using gas chromatography mass spectrometry Abdulrazaq Yahaya Department of Chemistry, Kogi State University, Anyigba Kogi State, Nigeria
a r t i c l e
i n f o
a b s t r a c t
Article history: Received 22 March 2019 Revised 2 May 2019 Accepted 7 May 2019 Available online 10 May 2019
Nitrosamines (NAms) are emerging organic pollutants formed as by-products of chemical treatment of water, environmental samples as well as in foods at low concentrations. They are potentially carcinogenic and because of their hydrophilic and volatile nature, they are highly soluble in water. They fragment at high temperatures thus, they require appropriate oven temperature and gas flow rate in gas chromatography mass spectrometry (GC-MS) for their quantitative analysis. The analytical method for the identification and quantitation of seven volatile and thermally un-stable nitrosamines namely, (N-nitrosodimethylamine (NDMA), N-nitrosomethylethylamine (NMEA) N-nitrosodiethylamine (NDEA), N-nitrosopyrrolidine (NPYR), N-nitrosodi-n-propylamine (NDPA), N-nitrosopiperidine (NPIP) and N-nitrosodi-n-butylamine (NDBA) is presented in this work. The GC-MS with a DB-5 (30 m × 0.25 mm × 0.25 μm) capillary column (5% phenyl-95% dimethyl polysiloxane) was used in selective ion monitoring (SIM) mode. The target and reference ions ranged between 70–114 and 41–57 correspondingly, produced accurate mass measurement and sharper and clearly defined chromatogram. The relative standard deviation, RSD < 20%, correlation coefficient, r (from +0.9914 to +0.9993) and the linearity was in accordance with the standard analytical method. The NDBA RSD value of 23. 66% notwithstanding, a correlation coefficient (r) +0.9914) is an improvement over what we have had. © 2019 Elsevier B.V. All rights reserved.
Keywords: Nitrosamines DB-5 Column Oven temperature GCMS Correlation coefficient
Subject area Compounds Data category Data acquisition format Data type Procedure
Data accessibility
Analytical chemistry Nitrosamines Spectral Mass spectra Raw and analyzed Nitrosamine standard mixture was prepared in methanol and diluted into different concentrations between 0.1 to 500 μg/L. Suitable oven condition and analytical column were used on GC–MS. NAms standard was transferred into vials for GC–MS analysis. The injection volume and flow rate were optimized for high quality chromatogram Data are enclosed in this article
E-mail address: [email protected] https://doi.org/10.1016/j.cdc.2019.100231 2405-8300/© 2019 Elsevier B.V. All rights reserved.
2
A. Yahaya / Chemical Data Collections 21 (2019) 100231
1. Rationale The use of chloramine as chemical oxidant for water treatment leads to the formation of nitrosamines (NAms) which includes: (N-nitrosodimethylamine (NDMA), N-nitrosomethylethylamine (NMEA) N-nitrosodiethylamine (NDEA), N-nitrosopyrrolidine (NPYR), N-nitrosodi-n-propylamine (NDPA), N-nitrosopiperidine (NPIP), N-nitrosodi-nbutylamine (NDBA), (N-nitrosodimethylamine (NDMA), N-nitrosomethylethylamine (NMEA) N-nitrosodiethylamine (NDEA), N-nitrosopyrrolidine (NPYR), N-nitrosodi-n-propylamine (NDPA), N-nitrosopiperidine (NPIP), N-nitrosodi-n-butylamine (NDBA), N-nitrosomorpholine (NMor), as nitrogen containing disinfection by-products (N-DBPs [1,2]. However, it has been reported that some of these disinfection by-products (DBPs) are formed in chlorinated water in the presence of organic matter containing precursors such as nitrite and nitrate [3–5]. The most commonly detected nitrosamines in drinking water is NDMA and could be as a result of pollutants released from industrial effluents and anthropogenic activities into the water source [6–8]. Other factors that influence the formation of NDMA and all NAms are the pH and the ratio of chlorine to ammonia used as disinfectants. In addition, their distribution in water increases with increase in water retention time [5,9,10]. Also, formation of NDMA is favored by colder temperature [11,12]. NDMA was first detected in 1989 and 1999 in drinking water in Ontario province (Canada) and California (USA) respectively [1]. Since then, it has also been detected in Australia, Northern American and other places around the world [2]. NAms are always reported at low concentrations in water either in microgram or nanogram per liter. NDBA, NDPhA, NMor, NPyr and NPiP have been reported at lower concentrations than NDMA (180 ng/L) [5,9,13]. Nitrosamine in water is a threat to human health, in view of its perceived carcinogenicity [14]. Different countries have their regulatory bodies in maintaining standard water quality e.g. the maximum contaminants limit for NDMA is 9 ng/L in Canada and 7 ng/L in California (USA) [1,2]. To date, few analytical methods have been published for the determination of nitrosamine in water. For instance, Boyd et al. and Brisson et al. [13,14] reported the use of liquid chromatography mass spectrometry (LC-MS) and GC-MS for analysis of seven nitrosamines in water respectively. Herrmann et al. [15] reported RSD (2–23%) with liquid chromatography tandem mass spectrometry (LC/TS/MS/MS) for both chemical ionization and electrospray ionization mode for the analysis of eight NAms. Nitrosamines are not only detected in drinking water but also presents in foods such as meat and sausage. These seven nitrosamines NDMA, NMEA, NDEA, NPYR, NDPA, NPIP and NDBA were selected because they are frequently detected in the drinking water and are probably carcinogenic [1,2]. NAms decompose at high temperature and resolution of peaks in chromatographic techniques is always a challenge to the analyst. An analytical method capable of surmounting this challenge is in dire need for the adequate determination of NAms concentration in drinking water and environmental samples. Thus, this paper presents a protocol that may be suitable for the chromatographic separation of NAs. 2. Procedure 2.1. Sample preparation All glassware, amber glass bottles and vials were washed with detergent and dried in the oven at 180 °C for 24 h, allowed to cool and rinsed with acetone before used. The standard nitrosamine mixture (20 0 0 μg/mL) was prepared in methanol and diluted into different concentrations from 0.1 to 500 μg/L. This is then transferred into vial (1.5 ml) for the calibration of gas chromatography mass spectrometry [16]. 2.2. Analytical method A Shimadzu GC-MS QP2010 Plus with a DB-5 (30 m × 0.25 mm × 0.25 μm) capillary column (5% phenyl-95% dimethyl polysiloxane) operated in selective ion monitoring mode (Table 1) for proper quantification of nitrosamine. Helium was used as a carrier gas at flow rate of 1.25 ml/min and in splitless mode. Injection temperature and volume were 200 °C and
Table 1 The studied nitrosamines (target and reference ions). Compound
Abbreviation
Formula
Molecular mass
Target ion
Reference ion
N-nitrosodimethylamine N-nitrosomethylethylamine N-nitrosopyrrolidine N-nitrosodiethylamine N-nitrosopiperidine N-nitrosodi-n-propylamine N-nitrosodi-n-butylamine
NDMA NMEA NPYR NDEA NPIP NDPA NDBA
C2 H6 N2 O C3 H8 N2 O C4 H8 N2 O C4 H10 N2 O C5 H10 N2 O C6 H14 N2 O C8 H18 N2 O
74.04801 88.06366 100.06366 102.07931 114.07931 130.11061 158.14191
74 88 100 102 114 70 84
42 42 41 44 55 43 57
A. Yahaya / Chemical Data Collections 21 (2019) 100231
3
Fig. 1. (a). The chromatogram of nitrosamine standard mixture. The mass spectra of the seven nitrosamines standard mixture are shown in (b–h).
Fig. 1. Continued
4 μL respectively. Oven temperature; 40 °C held for 1 min, programmed at 10 °C/min for 110 °C, then, at 15 °C/min for 180 °C and finally at 40 °C/min at 260 °C is used. The temperature of the transfer line was 200 °C and MS was set at 240 °C in electron ionization (EI) mode. The total run time was 13.17 min [3].
4
A. Yahaya / Chemical Data Collections 21 (2019) 100231
Fig. 1. Continued
Fig. 1. Continued
Fig. 1. Continued
A. Yahaya / Chemical Data Collections 21 (2019) 100231
5
Fig. 1. Continued
Fig. 1. Continued
Fig. 1. Continued
3. Data, value and validation Separation of nitrosamines does not only depend on the composition of the column materials and flow rate of mobile phase (Helium gas used in GC) but also on the oven temperature. NAms decompose at high temperature and so the starting oven temperature should be kept at isothermal condition [1,17,18]. Oven conditioned was optimized at different run time (17 min, 16 min, 15 min, 14 min and 13.17 min). High quality chromatogram and mass spectral were observed at 13.17 min
6
A. Yahaya / Chemical Data Collections 21 (2019) 100231
Fig. 2. Peak areas of nitrosamines obtained at the indicated helium flow rates (1.00–1.55 ml/min) and at an injection volume of 4 μL of the NAms standard solution are presented in (a–g).
Fig. 2. Continued
Fig. 2. Continued
A. Yahaya / Chemical Data Collections 21 (2019) 100231
Fig. 2. Continued
Fig. 2. Continued
Fig. 2. Continued
7
8
A. Yahaya / Chemical Data Collections 21 (2019) 100231
Fig. 2. Continued
Fig. 3. Calibration curve (0.1–500 μg/L) of nitrosamines standard mixture shown in (a–h).
as shown in Fig. 1a and (b–h) respectively. Also, injection volume was varied from 1–5 μL. The chromatograms are well separated at 4 μL, fairly separated at 5 μL and poor resolution at 1–3 μL due to high instrumental base noise. A good gas flow rate increases the efficiency of the column and adequate transfer of the analyte to the detector but high flow rate prevents interaction between the stationary phase and component mixture, reduces retention time and results in poor peak separation. Therefore, the increase in the total response could be used to observe the quality of peaks [19]. A flow rate of 1.0–1.3 ml/min is suitable for an excellent peak separation [1,9,20]. The effect of flow rate on the peak area of the analyte are shown in Fig. 2(a – g) and better resolution of peaks was observed at 1.25 ml/min. Acceptable value of linearity, correlation coefficient (r) and RSD (Fig. 3[a–g] and Table 2) have been documented [9,15,20].
A. Yahaya / Chemical Data Collections 21 (2019) 100231
Fig. 3. Continued
Fig. 3. Continued
Fig. 3. Continued
9
10
A. Yahaya / Chemical Data Collections 21 (2019) 100231
Fig. 3. Continued
Fig. 3. Continued
Table 2 The linear equations, correlation coefficient (r), relative standard deviation (RSD) of nitrosamines standard mixture (0.1–500 μg/L). Nitrosamines
Linear equation
(r)
RSD (%)
NDMA NMEA NDEA NPYR NDPA NPIP NDBA
Y = 273.8349 x −4454.45 Y = 166.99 x −269.77 Y = 158.08 x −104.78 Y = 92.87 x −1241.65 Y = 244.43 x +2794.39 Y = 94.1337 x +727.051 Y = 77.177 x –1465.249
0.9981 0.9984 0.9978 0.9919 0.9956 0.9993 0.9914
15.43 19.27 18.50 13.29 10.46 8.80 23.66
A. Yahaya / Chemical Data Collections 21 (2019) 100231
11
Fig. 3. Continued
Acknowledgments The author thank Prof. Okonkwo, O.J, EARChem Research group and Rand Water Chair for their support and input during this research work at Tshwane University of Technology, Pretoria. Supplementary materials Supplementary material associated with this article can be found, in the online version, at doi:10.1016/j.cdc.2019.100231. References [1] G.A. Kim, H.-J. Son, C.-W. Kim, S.-H. Kim, Nitrosamine occurrence at Korean surface water using an analytical method based on GC/LRMS, Environ. Monit. Assess. 185 (2) (2013) 1657–1669. [2] A.D. Ngongang, S.V. Duy, S. Sauvé, Analysis of nine N-nitrosamines using liquid chromatography-accurate mass high resolution-mass spectrometry on a Q-Exactive instrument, Anal. Methods 7 (14) (2015) 5748–5759. [3] Y. Yuan, W. Meng, M. Yutian, C. Fang, H. Xiaosong, Determination of eight volatile nitrosamines in meat products by ultrasonic solvent extraction and gas chromatography-mass spectrometry method, Int. J. Food Prop. 18 (6) (2015) 1181–1190. [4] Y.Y. Zhao, X. Liu, J.M. Boyd, F. Qin, J. Li, X.-F. Li, Identification of N-nitrosamines in treated drinking water using nanoelectrospray ionization high-field asymmetric waveform ion mobility spectrometry with quadrupole time-of-flight mass spectrometry, J. Chromatogr. Sci. 47 (1) (2009) 92–96. [5] Y.-Y. Zhao, J. Boyd, S.E. Hrudey, X.-F. Li, Characterization of new nitrosamines in drinking water using liquid chromatography tandem mass spectrometry, Environ. Sci. Technol. 40 (Dec. (24)) (2006) 7636–7641. [6] M.B. Scheeren, H. Sabik, C. Gariépy, N.N. Terra, J. Arul, Determination of N- nitrosamines in processed meats by liquid extraction combined with gas chromatography-methanol chemical ionisation/mass spectrometry, Food Addit. Contam. 32 (9) (2015) 1436–1447. [7] C.G. Russell, N.K. Blute, Steve via X. Wu, Z. ChoWdhury, Nationwide assessment of nitrosamine occurrence and trends, Am. Water Work. Assoc. 48 (2) (2012) 205–215. [8] W. Wang, J. Yu, W. An, M. Yang, Occurrence and profiling of multiple nitrosamines in source water and drinking water of China, Sci. Total Environ. 551 (2016) 489–495. [9] J.W.A. Charrois, M.W. Arend, K.L. Froese, S.E. Hrudey, Detecting N-nitrosamines in drinking water at nanogram per liter levels using ammonia positive chemical ionization, Environ. Sci. Technol. 38 (18) (2004) 4835–4841. [10] J. Choi, R.L. Valentine, Formation of N-nitrosodimethylamine (NDMA) from reaction of monochloramine: a new disinfection by-product, Water Res. 36 (4) (2002) 817–824. [11] W.A. Mitch, J.O. Sharp, R.R. Trussell, R.L. Valentine, L. Alvarez-Cohen, D.L. Sedlak, N -Nitrosodimethylamine (NDMA) as a drinking water contaminant: a review, Environ. Eng. Sci. 20 (5) (Sep. 2003) 389–404. [12] D.L. Sedlak, R.A. Deeb, E.L. Hawley, W.A. Mitch, T.D. Durbin, S. Mowbray, S. Carr, Sources and fate of nitrosodimethylamine and its precursors in municipal wastewater treatment plants, Water Environ. Res. 77 (1) (2005) 32–39. [13] I.J. Brisson, P. Levallois, H. Tremblay, J. Sérodes, C. Deblois, J. Charrois, V. Taguchi, J. Boyd, X. Li, M.J. Rodriguez, Spatial and temporal occurrence of N-nitrosamines in seven drinking water supply systems, Environ. Monit. Assess. 185 (9) (2013) 7693–7708. [14] J.M. Boyd, S.E. Hrudey, S.D. Richardson, X.F. Li, Solid-phase extraction and high-performance liquid chromatography mass spectrometry analysis of nitrosamines in treated drinking water and wastewater, Trends Anal. Chem. 30 (9) (2011) 1410–1421. [15] S.S. Herrmann, L. Duedahl-Olesen, K. Granby, Simultaneous determination of volatile and non-volatile nitrosamines in processed meat products by liquid chromatography tandem mass spectrometry using atmospheric pressure chemical ionisation and electrospray ionisation, J. Chromatogr. A 1330 (2014) 20–29. [16] H. Dong, X. Guo, Y. Xian, H. Luo, B. Wang, Y. Wu, A salting out-acetonitrile homogeneous extraction coupled with gas chromatography-mass spectrometry method for the simultaneous determination of thirteen N-nitrosamines in skin care cosmetics, J. Chromatogr. A 1422 (2015) 82–88. [17] J.B. Phillips, J. Beens, Comprehensive two-dimensional gas chromatography: a hyphenated method with strong coupling between the two dimensions, J. Chromatogr. A 856 (1–2) (1999) 331–347.
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[18] A. Gratzfeld-Hüsgen, R. Schuster, in: HPLC for Food Analysis-Aprimer A Primer The fundamentals of an Alternative Approach to Solving Tomorrow’s Measurement Challenges Angelika, Agile Technologies Company, 2001, p. 146. [19] R.E. Ardrey, Liquid Chromatography-Mass Spectrometry: An Introduction (Vol. 2), John Wiley & Sons, 2003. [20] J.A. McDonald, N.B. Harden, L.D. Nghiem, S.J. Khan, Analysis of N-nitrosamines in water by isotope dilution gas chromatography-electron ionisation tandem mass spectrometry, Talanta 99 (2012) 146–154.
Contents lists available at ScienceDirect
Chemical Data Collections journal homepage: www.elsevier.com/locate/cdc
Data Article
Method development for the identification and quantitative analysis of seven nitrosamines using gas chromatography mass spectrometry Abdulrazaq Yahaya Department of Chemistry, Kogi State University, Anyigba Kogi State, Nigeria
a r t i c l e
i n f o
a b s t r a c t
Article history: Received 22 March 2019 Revised 2 May 2019 Accepted 7 May 2019 Available online 10 May 2019
Nitrosamines (NAms) are emerging organic pollutants formed as by-products of chemical treatment of water, environmental samples as well as in foods at low concentrations. They are potentially carcinogenic and because of their hydrophilic and volatile nature, they are highly soluble in water. They fragment at high temperatures thus, they require appropriate oven temperature and gas flow rate in gas chromatography mass spectrometry (GC-MS) for their quantitative analysis. The analytical method for the identification and quantitation of seven volatile and thermally un-stable nitrosamines namely, (N-nitrosodimethylamine (NDMA), N-nitrosomethylethylamine (NMEA) N-nitrosodiethylamine (NDEA), N-nitrosopyrrolidine (NPYR), N-nitrosodi-n-propylamine (NDPA), N-nitrosopiperidine (NPIP) and N-nitrosodi-n-butylamine (NDBA) is presented in this work. The GC-MS with a DB-5 (30 m × 0.25 mm × 0.25 μm) capillary column (5% phenyl-95% dimethyl polysiloxane) was used in selective ion monitoring (SIM) mode. The target and reference ions ranged between 70–114 and 41–57 correspondingly, produced accurate mass measurement and sharper and clearly defined chromatogram. The relative standard deviation, RSD < 20%, correlation coefficient, r (from +0.9914 to +0.9993) and the linearity was in accordance with the standard analytical method. The NDBA RSD value of 23. 66% notwithstanding, a correlation coefficient (r) +0.9914) is an improvement over what we have had. © 2019 Elsevier B.V. All rights reserved.
Keywords: Nitrosamines DB-5 Column Oven temperature GCMS Correlation coefficient
Subject area Compounds Data category Data acquisition format Data type Procedure
Data accessibility
Analytical chemistry Nitrosamines Spectral Mass spectra Raw and analyzed Nitrosamine standard mixture was prepared in methanol and diluted into different concentrations between 0.1 to 500 μg/L. Suitable oven condition and analytical column were used on GC–MS. NAms standard was transferred into vials for GC–MS analysis. The injection volume and flow rate were optimized for high quality chromatogram Data are enclosed in this article
E-mail address: [email protected] https://doi.org/10.1016/j.cdc.2019.100231 2405-8300/© 2019 Elsevier B.V. All rights reserved.
2
A. Yahaya / Chemical Data Collections 21 (2019) 100231
1. Rationale The use of chloramine as chemical oxidant for water treatment leads to the formation of nitrosamines (NAms) which includes: (N-nitrosodimethylamine (NDMA), N-nitrosomethylethylamine (NMEA) N-nitrosodiethylamine (NDEA), N-nitrosopyrrolidine (NPYR), N-nitrosodi-n-propylamine (NDPA), N-nitrosopiperidine (NPIP), N-nitrosodi-nbutylamine (NDBA), (N-nitrosodimethylamine (NDMA), N-nitrosomethylethylamine (NMEA) N-nitrosodiethylamine (NDEA), N-nitrosopyrrolidine (NPYR), N-nitrosodi-n-propylamine (NDPA), N-nitrosopiperidine (NPIP), N-nitrosodi-n-butylamine (NDBA), N-nitrosomorpholine (NMor), as nitrogen containing disinfection by-products (N-DBPs [1,2]. However, it has been reported that some of these disinfection by-products (DBPs) are formed in chlorinated water in the presence of organic matter containing precursors such as nitrite and nitrate [3–5]. The most commonly detected nitrosamines in drinking water is NDMA and could be as a result of pollutants released from industrial effluents and anthropogenic activities into the water source [6–8]. Other factors that influence the formation of NDMA and all NAms are the pH and the ratio of chlorine to ammonia used as disinfectants. In addition, their distribution in water increases with increase in water retention time [5,9,10]. Also, formation of NDMA is favored by colder temperature [11,12]. NDMA was first detected in 1989 and 1999 in drinking water in Ontario province (Canada) and California (USA) respectively [1]. Since then, it has also been detected in Australia, Northern American and other places around the world [2]. NAms are always reported at low concentrations in water either in microgram or nanogram per liter. NDBA, NDPhA, NMor, NPyr and NPiP have been reported at lower concentrations than NDMA (180 ng/L) [5,9,13]. Nitrosamine in water is a threat to human health, in view of its perceived carcinogenicity [14]. Different countries have their regulatory bodies in maintaining standard water quality e.g. the maximum contaminants limit for NDMA is 9 ng/L in Canada and 7 ng/L in California (USA) [1,2]. To date, few analytical methods have been published for the determination of nitrosamine in water. For instance, Boyd et al. and Brisson et al. [13,14] reported the use of liquid chromatography mass spectrometry (LC-MS) and GC-MS for analysis of seven nitrosamines in water respectively. Herrmann et al. [15] reported RSD (2–23%) with liquid chromatography tandem mass spectrometry (LC/TS/MS/MS) for both chemical ionization and electrospray ionization mode for the analysis of eight NAms. Nitrosamines are not only detected in drinking water but also presents in foods such as meat and sausage. These seven nitrosamines NDMA, NMEA, NDEA, NPYR, NDPA, NPIP and NDBA were selected because they are frequently detected in the drinking water and are probably carcinogenic [1,2]. NAms decompose at high temperature and resolution of peaks in chromatographic techniques is always a challenge to the analyst. An analytical method capable of surmounting this challenge is in dire need for the adequate determination of NAms concentration in drinking water and environmental samples. Thus, this paper presents a protocol that may be suitable for the chromatographic separation of NAs. 2. Procedure 2.1. Sample preparation All glassware, amber glass bottles and vials were washed with detergent and dried in the oven at 180 °C for 24 h, allowed to cool and rinsed with acetone before used. The standard nitrosamine mixture (20 0 0 μg/mL) was prepared in methanol and diluted into different concentrations from 0.1 to 500 μg/L. This is then transferred into vial (1.5 ml) for the calibration of gas chromatography mass spectrometry [16]. 2.2. Analytical method A Shimadzu GC-MS QP2010 Plus with a DB-5 (30 m × 0.25 mm × 0.25 μm) capillary column (5% phenyl-95% dimethyl polysiloxane) operated in selective ion monitoring mode (Table 1) for proper quantification of nitrosamine. Helium was used as a carrier gas at flow rate of 1.25 ml/min and in splitless mode. Injection temperature and volume were 200 °C and
Table 1 The studied nitrosamines (target and reference ions). Compound
Abbreviation
Formula
Molecular mass
Target ion
Reference ion
N-nitrosodimethylamine N-nitrosomethylethylamine N-nitrosopyrrolidine N-nitrosodiethylamine N-nitrosopiperidine N-nitrosodi-n-propylamine N-nitrosodi-n-butylamine
NDMA NMEA NPYR NDEA NPIP NDPA NDBA
C2 H6 N2 O C3 H8 N2 O C4 H8 N2 O C4 H10 N2 O C5 H10 N2 O C6 H14 N2 O C8 H18 N2 O
74.04801 88.06366 100.06366 102.07931 114.07931 130.11061 158.14191
74 88 100 102 114 70 84
42 42 41 44 55 43 57
A. Yahaya / Chemical Data Collections 21 (2019) 100231
3
Fig. 1. (a). The chromatogram of nitrosamine standard mixture. The mass spectra of the seven nitrosamines standard mixture are shown in (b–h).
Fig. 1. Continued
4 μL respectively. Oven temperature; 40 °C held for 1 min, programmed at 10 °C/min for 110 °C, then, at 15 °C/min for 180 °C and finally at 40 °C/min at 260 °C is used. The temperature of the transfer line was 200 °C and MS was set at 240 °C in electron ionization (EI) mode. The total run time was 13.17 min [3].
4
A. Yahaya / Chemical Data Collections 21 (2019) 100231
Fig. 1. Continued
Fig. 1. Continued
Fig. 1. Continued
A. Yahaya / Chemical Data Collections 21 (2019) 100231
5
Fig. 1. Continued
Fig. 1. Continued
Fig. 1. Continued
3. Data, value and validation Separation of nitrosamines does not only depend on the composition of the column materials and flow rate of mobile phase (Helium gas used in GC) but also on the oven temperature. NAms decompose at high temperature and so the starting oven temperature should be kept at isothermal condition [1,17,18]. Oven conditioned was optimized at different run time (17 min, 16 min, 15 min, 14 min and 13.17 min). High quality chromatogram and mass spectral were observed at 13.17 min
6
A. Yahaya / Chemical Data Collections 21 (2019) 100231
Fig. 2. Peak areas of nitrosamines obtained at the indicated helium flow rates (1.00–1.55 ml/min) and at an injection volume of 4 μL of the NAms standard solution are presented in (a–g).
Fig. 2. Continued
Fig. 2. Continued
A. Yahaya / Chemical Data Collections 21 (2019) 100231
Fig. 2. Continued
Fig. 2. Continued
Fig. 2. Continued
7
8
A. Yahaya / Chemical Data Collections 21 (2019) 100231
Fig. 2. Continued
Fig. 3. Calibration curve (0.1–500 μg/L) of nitrosamines standard mixture shown in (a–h).
as shown in Fig. 1a and (b–h) respectively. Also, injection volume was varied from 1–5 μL. The chromatograms are well separated at 4 μL, fairly separated at 5 μL and poor resolution at 1–3 μL due to high instrumental base noise. A good gas flow rate increases the efficiency of the column and adequate transfer of the analyte to the detector but high flow rate prevents interaction between the stationary phase and component mixture, reduces retention time and results in poor peak separation. Therefore, the increase in the total response could be used to observe the quality of peaks [19]. A flow rate of 1.0–1.3 ml/min is suitable for an excellent peak separation [1,9,20]. The effect of flow rate on the peak area of the analyte are shown in Fig. 2(a – g) and better resolution of peaks was observed at 1.25 ml/min. Acceptable value of linearity, correlation coefficient (r) and RSD (Fig. 3[a–g] and Table 2) have been documented [9,15,20].
A. Yahaya / Chemical Data Collections 21 (2019) 100231
Fig. 3. Continued
Fig. 3. Continued
Fig. 3. Continued
9
10
A. Yahaya / Chemical Data Collections 21 (2019) 100231
Fig. 3. Continued
Fig. 3. Continued
Table 2 The linear equations, correlation coefficient (r), relative standard deviation (RSD) of nitrosamines standard mixture (0.1–500 μg/L). Nitrosamines
Linear equation
(r)
RSD (%)
NDMA NMEA NDEA NPYR NDPA NPIP NDBA
Y = 273.8349 x −4454.45 Y = 166.99 x −269.77 Y = 158.08 x −104.78 Y = 92.87 x −1241.65 Y = 244.43 x +2794.39 Y = 94.1337 x +727.051 Y = 77.177 x –1465.249
0.9981 0.9984 0.9978 0.9919 0.9956 0.9993 0.9914
15.43 19.27 18.50 13.29 10.46 8.80 23.66
A. Yahaya / Chemical Data Collections 21 (2019) 100231
11
Fig. 3. Continued
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