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A simple and sensitive method for analysis of 1-OHP-G in urine to evaluate PAHs exposure was established. The urine was extracted with a OASIS PRiME HLB column, and the eluent was directly injected into HPLC–FLD for analysis. The separation was carried out on a ACQUIIY UPLC BEH C18 column (2.1 × 50 mm, 1.7 μm), using methanol–1.5% formic acid water (60:40, v:v) as mobile phase at the flow rate of 0.2 mL/min. 1-OHP-G was detected at the excitation wavelength of 338 nm and the emission wavelength of 379 nm. Good linearity was obtained from 0.010 to 5.0 ng/mL for 1-OHP-G. The limit of detection of 1-OHP-G was 0.0032 ng/mL and the limit of quantification was 0.010 ng/mL. The intra-day and the inter-day precisions were 1.68, 4.98 and 1.81%, 5.00% at the concentrations of 0.010 ng/mL and 5.0 ng/mL, respectively. The proposed method was applied for urine sample analysis and the whole procedure could be completed within 8 min with the recoveries of 91.9–109%, 92.7–107% and 94.5–107% at the concentrations of 0.010 ng/mL, 1.0 ng/mL and 5.0 ng/mL, respectively. The results of 41 urine samples from non-professionals measured with the proposed method and UPLC–MS/MS were compared by Bland–Altman test and Passing–Bablok regression, showing a good agreement between the two methods. Moreover, dynamic change of urinary 1-OHP-G after eating barbecued food was detected by the proposed method and the results were consistent with the reported researches about 1-OHP. The proposed method was simple and rapid, and it could also to meet the assessment of population exposure to PAHs with high sensitivity and accuracy.

Maternal exposure to benzene and related compounds, trichloroethylene, and polycyclic aromatic hydrocarbons has been suggested as risk factors for reproductive and developmental problem. In different countries and groups, there are differences in socioeconomic circumstances, consumer products, dietary habits, lifestyles, and so on, resulting in different exposure risks from these chemicals. This study investigated the correlation between their metabolite concentrations and socioeconomic, demographic, and dietary factors to explore the possible exposure source of the concerned pollutants in pregnant women. We conducted biological monitoring to assess the exposure of these chemicals using urine samples from 590 to 639 pregnant women during 2nd or 3rd trimester of pregnancy in six cities of China. Socioeconomic and demographic characteristics and dietary habits were collected from questionnaires. The detection rate was over 74% of the urine samples for all metabolites. Compared with the Fourth National Report on Human Exposure to Environmental Chemical concentrations for females (FNRHEEC, the US Centers for Disease Control and Prevention), the metabolite concentrations of benzene compounds and trichloroethylene, excluding MA reported here, were higher. Principal component analysis results showed that SBMA and MHA could be proxy of the principal sources of metabolites for benzene compounds. The concentrations of SBMA and MA were higher in Fuzhou and Wuhan, respectively. The concentration of DCVMA was higher in Shenzhen, Xi'an, and Nanning, and the concentration of PGA was higher in Fuzhou, Wuhan, and Xi'an. Also, the 1-OHPG concentration in Wuhan is higher than that in Fuzhou and Shenzhen. Unhealthy dietary habits, using cosmetics and indoor exposure, contacting chemical solvent during pregnancy were associated with increased benzene compounds, trichloroethylene, and PAH exposure. There were significant positive associations between 1-OHPG level and maternal BMI, low education status, and cooking without a range hood. Pregnant women in China may be at a greater risk of exposure to most of the target compounds than US females, and their exposure levels varied in different regions. Some adverse environmental and behavioral factors may increase the exposure of environmental toxins, which can urge people to take measures to reduce the health risk to pregnant women during pregnancy.

Bisphenol analogues, amphenicol antibiotics, and phthalate have widely aroused public concerns due to their adverse effects on human health. In this study, a rapid and sensitive method for determination of nine bisphenol analogues, three amphenicol antibiotics, and six phthalate metabolites in the urine based on ultra-high-performance liquid chromatography coupled with triple quadrupole tandem mass spectrometry was developed and validated. The sample pretreatment condition on the base of mixed-mode anion-exchange (Oasis MAX) SPE was optimized to separate bisphenol analogues and amphenicol antibiotics from phthalate metabolites: the former were detected with a mobile phase of 0.1% ammonium water solution/methanol containing 0.1% ammonium water solution in negative mode, whereas the latter were determined with a mobile phase of 0.1% acetic acid solution/acetonitrile containing 0.1% acetic acid in negative mode. The limits of detection were less than 0.26 ng/mL for bisphenol analogues, 0.12 ng/mL for amphenicol antibiotics, and 0.14 ng/mL for phathalate metabolites. The recoveries of all target analytes in three fortification levels ranged from 72.02 to 117.64% with the relative standard deviations of no larger than 14.51%. The matrix effect was adjusted by isotopically labeled internal standards. This proposed method was successfully applied to analyze 40 actual urines and 13 out of 18 studied compounds were detected. Graphical abstract Simultaneous determination of nine bisphenol analogues, three amphenicol antibiotics, and six phthalate metabolites in human urine samples.

Perfluorooctanoic acid (PFOA) in environmental media contains numerous isomers/enantiomers because of the PFOA manufacturing process and biological degradation of PFOA precursors. Few methods for analyzing PFOA enantiomers have been described. A simple derivatization method using (S)-1-phenethyl chloride that was developed to allow PFOA isomers/enantiomers to be separated by gas chromatography and analyzed by electron-capture negative ionization mass spectrometry is described here. PFOA standards were analyzed, and enantiomers of the chiral isomers perfluoro-3-methyl-heptanoic acid, perfluoro-4-methyl-heptanoic acid, and perfluoro-3,5-dimethyl-hexanoic acid were separated using an HP-5MS column. Linear PFOA and perfluoro-6-methyl-heptanoic acid were chromatographically separated from these enantiomers. The linear ranges (giving correlation coefficients r > 0.997) of the calibration curves for the isomers were 0.010–3.00 ng/mL. PFOA isomer/enantiomer concentrations in river water were determined using the method. The method separated the enantiomers of perfluoro-3-methyl-heptanoic acid and perfluoro-4-methyl-heptanoic acid, the isomers of perfluoro-6-methyl-heptanoic acid, and linear PFOA in river water. No significant differences were found between the PFOA enantiomer/isomer compositions of the sample and technical PFOA. Enantiomer ratios can provide information about the sources and transport of pollutant isomers/enantiomers in the environment. Enantiomeric separation requires effective separation techniques. Our method achieved chiral separation using a non-chiral GC column that is often used in general analytical laboratories. The method could be used to investigate the sources and fates of PFOA and the isomers/enantiomers of other potentially toxic persistent pollutants in the environment and the risks posed to humans.

Phosphodiesterase type 5 (PDE5) inhibitors are first-line therapy for pulmonary arterial hypertension (PAH) and erectile dysfunction. As a continuing work to improve the terminal half-lives and oral bioavailabilities of our previously reported 4(3 H)-pyrimidones, a pharmacokinetics-driven optimization focusing on the terminal substituent is described. Two major congeneric series of 4(3 H)-pyrimidones, the aminosulfonylphenylpyrimidones and acylaminophenylpyrimidones, were designed, synthesized, and pharmacologically assessed in vitro and in vivo. Among them, compound 15 (TPN171) with subnanomolar potency for PDE5 and good selectivity over PDE6 was finally recognized as a potential drug candidate, and its pharmacokinetic profiles in rats and dogs are significantly improved compared to the starting compound (3). Moreover, TPN171 was proven to exert a longer lasting effect than sildenafil in animal models, providing a foundation for a once-daily oral administration for its clinical use. TPN171 is currently being investigated in a phase II clinical trial for the treatment of PAH.

Urinary cotinine and NNAL are the biomarkers of tobacco smoke exposure and tobacco specific nitrosamines (TSNAs), respectively. A new method for the simultaneous analysis of them by hydrophilic interaction liquid chromatography tandem mass (HILIC-MS/MS) combined with PRiME HLB solid phase extraction (SPE) was developed. The sample matrix was removed effectively with PRiME HLB SPE and HILIC separation. The linearities were good in a range of 5.00-3.00 × 103 ng/L for NNAL and 0.200-4.00 × 102 μg/L for cotinine. The method detection limit of NNAL (0.0580 ng/L) was better than that in other literatures, and 0.0240 μg/L for cotinine. Recoveries were 91.6-110% and 88.7-113% with relative standard deviations of 3.78-9.12% and 0.120-1.15% for NNAL and cotinine, respectively. 29 urine samples were detected by the established method. The contents of NNAL and cotinine were 0.590-66.7 ng/g·Cr and 2.86-1.34 × 103 μg/g·Cr, respectively. Moreover, the results showed that urinary NNAL and cotinine were significantly positive correlation, even in passive smokers.

A method of binary mixed solvent-based solvent demulsification dispersive liquid-liquid microextraction coupled with gas chromatography-tandem mass spectrometry (GC-MS/MS) was developed for the determination of polycyclic aromatic hydrocarbons (PAHs) in water samples. A binary mixed solvent of methylene chloride and n-hexane (v/v = 1 : 1) which has a lower density than water was used as the extraction solvent, obtaining satisfactory extraction efficiencies for PAHs, and also allowing convenient operation. Acetonitrile as the dispersive solvent was injected into the water sample solution to form an emulsion. The extraction can be completed in 5 min and ethanol was used as the demulsification solvent to bring about successful phase separation without centrifugation. Coupled with GC-MS/MS analysis, the method was simple, sensitive, accurate and suitable for batch analysis of PAHs in water samples. Good linearity was obtained within the linear range for 16 PAH compounds, with determination coefficients from 0.9980 to 0.9998. This method can be used to effectively evaluate the situation of PAH pollution in water intended for human consumption and environmental water, the method detection limits (MDLs) of which were 2.1 to 13.6 ng L−1 and only 20 mL of water samples were used for analysis. The proposed method was applied to determine PAHs in actual water samples including tap water, and the upper, middle and lower reaches of the Jinjiang river in Chengdu city. Meanwhile, spiked samples and procedural blanks were used for quality control measurements according to ISO/TS 13530-2009 to guarantee the accuracy of this method. The average spiked recoveries of PAHs were in the range of 85.0–104% with RSDs in the range of 5.8–10.9%. Naphthalene, acenaphthylene, acenaphthene, fluorene, phenanthrene, fluoranthene and pyrene were predominantly measured, and PAH pollution was found at the total concentrations of 0.162–0.206 μg L−1 in the Jinjiang river of Chengdu city of P. R. China. Considering their toxicity, attention should be paid to water pollution by PAHs and necessary monitoring should be done.

The glucuronide conjugate of 1-hydroxypyrene (1-OHP-G) is a sensitive and reliable index biomarker for assessing low exposure to polycyclic aromatic hydrocarbons (PAHs). A simple method for determining 1-OHP-G in human urine with ultra performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) was established and applied to evaluate the exposure level of PAHs of pregnant women in a large sample size. After the urine sample was extracted with ethyl acetate, 0.2 mL of the aqueous phase was diluted to 1.0 mL with 5 mmol/L ammonium acetate before injection. The chromatographic separation was performed on a C18 column with a gradient elution and identification was conducted on a tandem mass spectrometry with electrospray ionization in negative mode. 1-OHP-d9-G was used as an internal standard to improve precision. The method was validated and good linearity was obtained in the range of 0.1∼2.0 ng/mL. The limit of detection (LOD) and the limit of quantification (LOQ) of 1-OHP-G were 0.015 and 0.051 ng/mL. Intra-day and inter-day precision were 4.3 and 6.7 %, respectively. The spiked recoveries were 79.4∼106 % for urine samples. This method was rapid, sensitive, and very suitable for batch analysis of urine. Six hundred seventy-five urine samples of pregnant women from the cities of Fuzhou, Shenzhen, and Nanning of P.R. China were analyzed with the proposed method. The medians of 1-OHP-G concentration were 0.27 μg/g.cr (n = 201), 0.30 μg/g.cr (n = 212), and 0.51 μg/g.cr (n = 262) for the cities of Fuzhou, Shenzhen, and Nanning, respectively. 1-OHP-G concentrations in urine samples of pregnant women from the cities of Fuzhou and Shenzhen in coastal areas were both significantly lower than that of Nanning City in inland region (p < 0.001).

Effective decomposition of antibiotic sulfadiazine (SD) in a Fe0-catalyzed sonochemical Fenton like system (Sono-FL) was demonstrated. By using the response surface methodology (RSM), an optimized experimental condition of pH 7.00, 0.94 mM Fe0, 1.90 mM persulfate (PS) and 20 W ultrasound (US) power was concluded, which could reach the predicted SD degradation efficiency of 90%. Afterwards, effects of wastewater matrix (five inorganic anions and two chelating agents) on the SD degradation were investigated in the system, respectively. It was found that the SD degradation could be inhibited by SO42−, NO3−, HCO3−/CO32− and H2PO4− to different extents. Cl− would lead to an enhancement with a low dosage (5 mM), but an inhibition with a high dosage (100 mM). Unexpectedly, chlorinated organic intermediates were also found as SD decomposed. Appropriate dosages of oxalic acid (OxA) or EDTA could benefit the SD degradation in the Sono-FL system, while excessive chelating agents would play as competitive pollutants. It was summarized that inorganic anions would mainly react with SO4 − and/or OH to form sub-radicals of less oxidative potential. OxA and EDTA would not only participate in complexing dissolution of Fe0 but also provide additional oxidants such as H2O2 and [FeIVO]2+, through the electron transfer reactions caused by the iron-ligands species.

The abasic site is one the most common DNA lesions formed in cells; it induces a severe blockage of DNA replication and is highly mutagenic. We continue to use Gp90 exo–, the sole DNA polymerase from Pseudomonas aeruginosa phage PaP1, to study DNA replication upon encountering an abasic site lesion. Gp90 exo– can incorporate dNTPs opposite the abasic site, but extension past this site is extremely slow. Among the four dNTPs, dATP is preferentially incorporated opposite the abasic site, consistent with the A-rule. The incorporation is independent of the identity of the nucleotide 5′ of the abasic site. The incorporation of dATP opposite the abasic site occurs by direct incorporation of dNTP opposite the abasic site without a −1 frameshift deletion. Extension from an A:abasic site pair by Gp90 exo– is slightly unfavorable relative to those from other abasic site pairs. Incorporation of dATP opposite the abasic site is preferential and shows a biphasic shape, indicating that this incorporation is much faster...

The analytical method of nicotine and cotinine in human urine with hydrophilic interaction chromatography-tandem mass spectrometry (HILIC-MS/MS) was established. After the urine sample containing nicotine-d4 and cotinine-d3 isotope internal standards being diluted with water, the filtrate was introduced into ultra performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) for analysis. Separation was performed on an ACQUITY UPLC® BEH HILIC column (50 mm×3.0 mm, 1.7 μ m), in which methanol and 0.1% (v/v) ammonia were used as the mobile phases with isocratic elution at 0.2 mL/min of flow rate. Positive ion scan mode was used for mass spectrometry measurement and calibration curves were plotted for quantification determination. A good linearity could be obtained in the range of 1.0-1000 μ g/L for nicotine and cotinine with the linear coefficients of 0.9949 and 0.9958, respectively. The limits of detection of nicotine and cotinine were 0.082 μ g/L and 0.077 μ g/L, and the limits of quantification were 0.27 μ g/L and 0.26 μ g/L, respectively. The recoveries of the spiked urine samples were 90.4%-103.5% and 93.0%-104.6%, and the relative standard deviations (RSDs) were 4.80%-6.21% and 4.22%-7.15% for nicotine and cotinine respectively. The established method was applied to the analyis of 200 urine samples. Based on the investigation information of the urine of the smoking people, the nicotine contents were 26.68-854.30 μ g/L, and the cotinine contents were 36.66-1191.18 μ g/L (n=86, Mnicotine=76.00 μ g/L, Mcotinine=83.52 μ g/L, M:median); of the nonsmoking people, the nicotine contents were 5.08-69.66 μ g/L, and the cotinine contents were 3.16-28.21 μ g/L (n=114, Mnicotine=7.53 μ g/L, Mcotinine=3.79 μ g/L). The method is simple, sensitive and rapid. It is suitable for batch analysis of nicotine and cotinine in urine, and it can meet the requirement of evaluating the human tobacco exposure.

A method of vortex-assisted dispersive liquid-liquid extraction coupled with gas chromatography and tandem mass spectrometry for the determination of nicotine and cotinine in urine was developed. Response surface methodology was applied to obtain the optimum extraction conditions. In this method, Plackett-Burman design was utilized to evaluate the impact of five selected factors on pretreatment procedure. Then, three main factors were optimized using a Box-Behnken design. The optimized method showed good linearities at 1-2000 μg/L with correlation coefficients of 0.9998 for nicotine and 0.9986 for cotinine. Recovery was 91.4-106 and 91.7-108% for nicotine and cotinine, respectively. The intraday relative standard derivations of determination were 1.47-4.06% for nicotine and 0.41-3.16% for cotinine, and interday relative standard derivations were 3.03-6.70% for nicotine and 1.64-6.38% for cotinine. The method detection limits for nicotine and cotinine were 0.33 and 0.34 μg/L, respectively. A total of 87 urine samples from smokers and nonsmokers were tested with the proposed method. Urinary nicotine and cotinine were 23.0-6.67 × 103 and 18.4-4.17 × 103 μg/(g·cr) for smokers and 1.31-286 and 1.39-131 μg/(g·cr) for nonsmokers, respectively. The method is sensitive, suitable and reliable for the determination of nicotine and cotinine in urine and meets the requirements for evaluating short-term tobacco exposure.

In this study, a novel ultrasound-enhanced heterogeneous Fe 0 /persulfate (US/Fe 0 /PS) system was developed and investigated for the degradation of an antibiotic sulfadiazine (SD). It was demonstrated that the US/Fe 0 /PS system could achieve a significant synergy in the degradation efficiency of SD, as compared to its corresponding comparative systems. The SD degradation in the US/Fe 0 /PS system could be applied by the pseudo-first-order kinetic with a k obs (SD) value of 3.4 ± 0.20 h −1 . Affecting factors such as initial pH, dosage ratio of [Fe 0 ]:[PS], US input power and reaction temperature were further studied. SD could be effectively degraded with a relatively low PS dosage at a broad pH range of 3–7. Simultaneous evolution of soluble iron species and PS was evaluated in three comparative systems (US/Fe 0 , Fe 0 /PS and US/Fe 0 /PS) during the reaction. It could be concluded that the promotional role of US would be dual in the US/Fe 0 /PS system, i.e. enhancement in the heterogeneous iron corrosion reactions and acceleration in the bulk radical reactions. Identification of the degradation intermediates indicated that sulfate radical (SO 4 − ) oxidation was the main SD degradation pathway. Attacking of the amine group in the benzene ring would be its first step, followed by cleavage of C–N bonds in the heterocyclic ring. Another degradation pathway, i.e. direct cleavage of the S–N bond should be also present.

Li-rich layered cathode materials Li1.13[Ni0.233Mn0.534Co0.233]0.87O2 are successfully synthesized by a co-precipitation method with hexadecyl trimethyl ammonium bromide (CTAB) as a surfactant. The structural and electrochemical feature changes of the resulting cathode materials have been studied thoroughly. When CTAB is considered as a surfactant, well-crystallized Li-rich layered cathode materials are obtained with Li2CO3 treatment for the festoon-like precursor hierarchically assembled by nanoplates. Among these oxides, the sample synthesized with CTAB shows a stable mixed phase on the edge of the powder particles and exhibits excellent electrochemical performance. The product delivers the highest initial discharge capacity of 394 mA h g−1 at 0.1 C (1 C = 200 mA g−1) between 2.5 and 4.8 V and 84.1% capacity is retained after 100 cycles. It is considered that the higher capacity and superior rate capability would be ascribed to the activation effect of CTAB, which can form a stable mixed structure and thus effectively alleviate the layered/spinel structure change during cycling.

A method of reversed phase high performance liquid chromatography (RP-HPLC) coupled with a diode array detector (DAD) was developed for the simultaneous determination of 10 common flavonoids in propolis-rich functional foods. Flavonoids in a sample were extracted with methanol in an ultrasonic bath for 15 min and then chromatographically separated on a C 18 column. The binary mobile phase, composed of water with 1% tetrahydrofuran (pH = 2.5) and acetonitrile, was used for gradient elution. The proposed method revealed a good linearity between the peak area of each analyte and its concentration. The intra- and inter-day relative standard deviations (RSDs) were less than 1.90% and 4.91%, respectively. Recoveries were within the range of 84.2–118.7%. LODs and LOQs were 0.043–0.232 μg mL −1 ( S / N = 3) and 0.007–0.039 mg g −1 ( S / N = 10), respectively. The proposed method provided a simple and rapid routine analysis of common flavonoids in propolis-rich functional foods which are popular on the market nowadays.

A novel method for simultaneous determination of eight organochlorine pesticides in aqueous samples by solvent demulsification-dispersive liquid-liquid microextraction based on solidification of floating organic drop coupled with gas chromatography-mass spectrometry (GC-MS) was established. A mixture of extractant (n-hexadecane) and dispersive agent (ace-tone) at the ratio of 1/5 (v/v) was injected into aqueous sample to form an emulsion and an extraction process was accomplished. The demulsifier (750μL acetone) was then injected to break up the emulsion. The two phases were separated quickly without centrifugation. After being solidified in an ice-bath, the upper layer (n-hexadecane) was transferred into an Eppendorf tube and analyzed by GC-MS after melted at room temperature. Factors affecting extraction efficiency such as the type and volume of extractant, dispersive agent and demulsifier, also ionic strength and pH value of extraction system were studied. Under the optimized conditions, the working curve of the proposed method provided a good linearity in the range of 0.025-2.00μg/L (r = 0.999 5-0.999 9). The detection limits of the organochlorine pesticides calculated by Hubaux-Vos method were 0.012-0.024μg/L and the relative standard deviations (RSDs) ranged from 3.15% to 4.53%. The enrichment factors (EF) were 96-101. When the method was applied to the determination of farmland water, the average spiked recoveries were 96.77%-102.93% with the relative standard deviations of 2.68%-4.86%. The proposed method is sensitive and fast. It also has the advantage of little organic solvent consumption so that it is friendly to environment and suitable for batch analysis of organochlorine pesticides in aqueous samples. Meanwhile, it provides technical and methodological support for achieving the automation of sample pretreatment.

Five Asian willow species (Salix jiangsuensis J172, Salix matsudana, Salix integra Yizhibi, Salix integra Weishanhu, and Salix mongolica) were evaluated for their potential for phytofiltration of arsenic (As) from synthetically contaminated waters. Arsenic accumulation, tolerance, uptake influx, and phytofiltration ability of the five willow species were examined under hydroponic conditions in a glasshouse. Short-term exposure (2 weeks) to solutions containing 80 μmol L−1 arsenate (As(V)), resulted in significant accumulation of As in all willow species. Arsenic concentration in plant roots ranged from 322 mg kg−1 dry weight (DW) for S. matsudana to 604 mg kg−1 (DW) for S. integra Yizhibi. S. integra Yizhibi decreased As(V) concentration in water from 3.87 to 1.89 μmol L−1 (290 to 142 μg L−1) over 168 h, which is 50 % of the total As(V) in the solution. The results suggested that even though Asian willow was not a traditional aquatic species, it still had significant potential for phytofiltration of As from contaminated waters. Of the five willow species studied, S. integra Yizhibi had the greatest capacity to remove As from As-contaminated waters. Thus, Asian willow has significant potential for the phytofiltration of As and may also be suitable for practical phytoremediation of As in highly water-logged areas. Refereed/Peer-reviewed

A fast, simple and environmentally friendly method to determine nicotine and cotinine in urine has been developed using dispersive liquid–liquid microextraction based on solidification of floating organic droplet (DLLME-SFO) with a binary mixed extractant as the pretreatment method and high performance liquid chromatography with an ultraviolet detector (HPLC-UVD) as the analysis system. The nicotine and cotinine in urine samples were extracted using the binary mixed solvent of undecanol and CHCl3 (v/v = 1 : 1) during the DLLME-SFO procedure. The employment of the mixed solvent had significantly improved the extraction efficiency of cotinine. Several crucial experiment parameters were evaluated, including the type and volume of extract solvent, type of dispersive solvent, pH of the aqueous phase, concentration of sodium chloride in the urine samples and extraction time. Under the optimal conditions, good linearity was observed in the range of 0.01–5.00 μg mL−1 for nicotine and cotinine with correlation coefficients of 0.9993 and 0.9996 respectively, and the method detection limit (MLD) was 0.002 μg mL−1 for both analytes. The proposed method was applied to urine sample analysis and the spiked recoveries of nicotine and cotinine were in the range of 78.0–105.0% and 72.0–86.7% respectively, with the relative standard deviations (RSDs) in the range of 6.02–7.28% and 2.94–8.43% respectively.