Phthalic acid esters (PAEs), known as phthalates, are a group of
plasticizers used in plastic manufacture (Fujii et al., 2003) to
increase flexibility. They are also used as solubilizing or stabilizing
agents in other applications such as building products (flooring,
furniture, and electric cables) (Butte & Heizow, 2002), personal
care and cosmetic products (deodorants, hair products and perfumes)
(Cao, 2010; Shen et al., 2007), textile industry and pesticide
formulation (Koch, Rossbach, Drexler, & Angerer, 2003). However,
they are not chemically bonded to polymers, and can easily
migrate into foods (Moskovkin, 2002). The toxicity of PAEs to
human being has been reported for a long time (Martino-andrade
& Chahoud, 2009; Okamoto, Ueda, & Kojima, 2011), and contamination
of foods has occurred in recent years (Li & Ko, 2012). Thus
research on PAE analysis in different kinds of foods and packing
materials is very important.
Gas chromatography (GC) is the most widely used method to
determine PAEs, and is always combined with mass spectrometry
(MS) (Ezˇerskis, Morkunas, Suman, & Simoneau, 2007; Nanni
et al., 2011). High performance liquid chromatography (HPLC) is
also a suitable method to determine PAEs (Li et al., 2011; Ma,
Hashi, Ji, & Lin, 2010). However, GC–MS and HPLC are veryexpensive to run, and HPLC consumes a lot of organic solvents.
Some reports showed that analysis of PAEs with HPLC would need
a long analysis time, even up to 90 min (Shi et al., 2011).
Furthermore, it is necessary to add a clean-up purification step in
pretreatment procedure when PAEs are determined by GC and
HPLC, since the matrixes in samples are easily adsorbed on the
packing, and pollute the columns. Capillary electrokinetic chromatography
(EKC) is an important separation technology for its
speed, efficiency, reproducibility, and minimal consumption of solvent.
Furthermore, there is no packing in the capillary, and the
pseudostationary phase (PSP) is fresh in each run. Thus, the sample
pretreatment is simpler in EKC than in GC or HPLC. However, EKC
is limited by lower sensitivity due to narrow path with ultraviolet
(UV) detector. In recent reports, EKC had been used to separate
PAEs (Guo, Wen, Shan, Zhang, & Lin, 2005; Ong, Lee, & Li, 1991).
However, the PAEs measured in these reports were few in number,
especially for the highly hydrophobic PAEs. The best work for PAEs
separation with EKC was reported by Pérez-fernández, González,
García, and Marina (2013). They used a running buffer containing
25 mM b-cyclodextrin and 100 mM sodium deoxycholate modified
with 10% (v/v) acetonitrile to separate 10 kinds of PAEs, dimethyl
phthalate (DMP), diethyl phthalate (DEP), diallyl phthalate (DAP),
dipropyl phthalate (DPP), dibutyl phthalate (DBP), dipentyl phthalate
(DNPP), dicyclohexyl phthalate (DCHP), benzyl butyl phthalate
(BBP), bis(2-ethylhexyl) phthalate (DEHP), di-n-octyl phthalate
(DNOP). However, the more lipophilic dinonyl phthalate (DNP)
was not involved, the baseline separation between DEHP and
DNOP could not be obtained, and the quantitative analysis of
DNOP could not be done. Because of the similar hydrophobicity,
DEHP and DNOP were retained strongly on the pseudostationary
phase (PSP). Just like in reversed phase liquid chromatography,
the weak or nonpolar analytes could not be separated by a polar
solvent eluent such as water. Highly lipophilic DEHP and DNOP
would not be separated with EKC in aqueous running buffer.
Thus, addition of weak polar organic solvent in the running buffer
would be beneficial for the elution of highly hydrophobic PAEs
from PSP. Unfortunately, the organic solvents are not allowed
above 20%, otherwise, the micelle would be destroyed. Thus, the
normal micelles as pseudostationary phase in EKC were limited
to the separation of the highly hydrophobic analytes.
Polymer surfactants were firstly used as PSP by Palmer in 1992
(Palmer, Khaled, & Mcnair, 1992; Palmer & Mcnair, 1992). Poly
(sodium undecylenate) was used as PSP in EKC to separate
hydrophobic analytes, such as, polycyclic aromatic hydrocarbons
(PAHs), with methanol and acetonitrile as organic additives. The
content of organic solvent could be added up to 45%. A typical comparison
between polymeric micelles and normal micelle was
reported by Otsuka, Wada, Ishisaka, and Terabe (2002). Poly
(sodium 10-undecylenyl sulfate) micelles could tolerate 60% acetonitrile
but SDS micelles could not when separating 11 kinds of
PAHs. Micelles formed by polymer surfactant is referred to as
molecule micelle since the micelle is formed by single molecule,
the critical micelle concentration (CMC) is essentially zero.
Additionally, the molecule micelle is steady due to the covalent
linkage among hydrophobic moieties. Thus, polymer surfactants
as PSPs have potential advantages including a much lower polymer
concentration required, ignorable variance of ionic strength and
viscosity introduced by the polymers, micelle stability in the presence
of high concentration of organic additives.
Our group have developed novel PSPs using polymeric aggregates
formed by self-assembly of random amphiphilic copolymers.
The random amphiphilic copolymer poly (methyl methacrylateco-
methacrylic acid) (P(MMA-co-MAA)) with the monomer ratio
of MMA to MAA of 7:3 was used as PSP in EKC to separate 8 kinds
of corticosteroids in cosmetics (Xu et al., 2014). Poly (stearyl
methacrylate-co-methacrylic acid) (P(SMA-co-MAA)) with the
monomer ratio of SMA to MAA of 0.5:9.5 was used as PSP to separate
11 kinds of water- and fat-soluble vitamins simultaneously
(Ni, Xing, Cao, & Cao, 2014). The advantage of polymeric aggregate
PSP is that the selectivity could be adjusted by changing the type of
hydrophobic and hydrophilic monomer, or varying the molar ratio
of the hydrophobic monomer to the hydrophilic monomer. Though
the PSP for simultaneous analysis of water- and fat-soluble vitamins
in our previous work was not suitable to separate more
hydrophobic PAEs, more lipophilic copolymer (P(SMA-co-MAA))
with the monomer ratio of SMA to MAA of 1:9 was synthesized.
The polymeric aggregate was self-assembled with selective solvent
approach, and the polymeric PSP was used in EKC to separate 15
kinds of PAEs in the present work.
Esters phthalic กรด (PAEs), เรียกว่า phthalates คือ กลุ่มของplasticizers ที่ใช้ในการผลิตพลาสติก (ฟูจิอิ et al., 2003)เพิ่มความยืดหยุ่น พวกเขายังใช้เป็น solubilizing หรือ stabilizingตัวแทนในโปรแกรมประยุกต์อื่นเช่นสร้าง (พื้น ผลิตภัณฑ์เฟอร์นิเจอร์ และสายไฟฟ้า) (Butte & Heizow, 2002), ส่วนบุคคลผลิตภัณฑ์เครื่องสำอางและการดูแล (deodorants ผลิตภัณฑ์ผม และน้ำหอม)(Cao, 2010 เชิน et al., 2007), ยาฆ่าแมลงและอุตสาหกรรมสิ่งทอกำหนด (คอ Rossbach, Drexler, & Angerer, 2003) อย่างไรก็ตามพวกเขาจะไม่สารเคมีพันธะกับโพลิเมอร์ และสามารถย้ายลงในอาหาร (Moskovkin, 2002) ความเป็นพิษของ PAEs เพื่อมนุษย์มีการรายงานเป็นเวลานาน (andrade มาร์ติโน& Chahoud, 2009 Okamoto ดะ และ มะ 2011), และการปนเปื้อนของอาหารที่เกิดในปีที่ผ่านมา (Li และเกาะ 2012) ดังนั้นงานวิจัยวิเคราะห์แพในชนิดของอาหารและบรรจุภัณฑ์วัสดุเป็นสิ่งสำคัญมากก๊าซ chromatography (GC) เป็นวิธีการที่ใช้กันอย่างแพร่หลายกำหนด PAEs และพร้อมเสมอกับโตรเมทรี(MS) (Ezˇerskis หมอก unas สุมาน & Simoneau, 2007 Nanniร้อยเอ็ด al., 2011) มีประสิทธิภาพสูงของเหลว chromatography (HPLC)นอกจากนี้ยังวิธีเหมาะสมเพื่อกำหนด PAEs (Li et al., 2011 MaHashi จิ และ หลิน 2010) อย่างไรก็ตาม GC – MS และ HPLC จะ veryexpensive ทำ และ HPLC ใช้มากอินทรีย์บางรายงานพบว่า จะต้องวิเคราะห์ด้วย HPLC PAEsเวลาวิเคราะห์นาน ได้ถึง 90 นาที (Shi et al., 2011)นอกจากนี้ จำเป็นต้องเพิ่มขั้นตอนฟอกล้างในกระบวนการ pretreatment เมื่อ PAEs ถูกกำหนด โดย GC และHPLC เนื่องจาก matrixes ในตัวอย่างจะได้ adsorbed บนบรรจุ และก่อให้เกิดมลพิษคอลัมน์ เส้นเลือดฝอย electrokinetic chromatography(EKC) คือ เทคโนโลยีการคัดแยกที่สำคัญสำหรับการความเร็ว ประสิทธิภาพ reproducibility และปริมาณการใช้น้อยที่สุดของตัวทำละลายนอกจากนี้ มีไม่บรรจุในหลอดเลือดฝอย และระยะ pseudostationary (PSP) ในแต่ละรันได้ ดังนั้น ตัวอย่างpretreatment เป็นวิธีที่ง่ายกว่าใน EKC กว่าใน GC HPLC อย่างไรก็ตาม EKCถูกจำกัด โดยความไวต่ำเนื่องจากเส้นทางที่แคบด้วยรังสีอัลตราไวโอเลต(UV) จับ ในรายงานล่าสุด EKC ที่ได้ถูกใช้เพื่อแยกPAEs (กัว Wen ซาน จาง และ หลิน 2005 อ๋อง Lee, & Li, 1991)อย่างไรก็ตาม PAEs วัดในรายงานเหล่านี้ได้ไม่กี่หมายเลขโดยเฉพาะอย่างยิ่งสำหรับ PAEs hydrophobic สูง งานดีที่สุดสำหรับ PAEsรายงาน โดย Pérez fernández, González แยกกับ EKCGarcía และมารีน่า (2013) พวกเขาใช้การใช้บัฟเฟอร์ที่ประกอบด้วย25 มม. 100 มม.และบี-cyclodextrin โซเดียม deoxycholate ปรับเปลี่ยนกับ 10% (v/v) acetonitrile เพื่อแยกชนิด 10 ของ PAEs, dimethylพทาเลท (DMP), diethyl พทาเลท (DEP), diallyl พทาเลท (DAP),dipropyl พทาเลท (DPP), dibutyl พทาเลท (DBP), พทาเลท dipentyl(DNPP), dicyclohexyl พทาเลท (DCHP), benzyl พทาเลทด...(BBP), bis(2-ethylhexyl) phthalate (DEHP), di-n-octyl phthalate(DNOP). However, the more lipophilic dinonyl phthalate (DNP)was not involved, the baseline separation between DEHP andDNOP could not be obtained, and the quantitative analysis ofDNOP could not be done. Because of the similar hydrophobicity,DEHP and DNOP were retained strongly on the pseudostationaryphase (PSP). Just like in reversed phase liquid chromatography,the weak or nonpolar analytes could not be separated by a polarsolvent eluent such as water. Highly lipophilic DEHP and DNOPwould not be separated with EKC in aqueous running buffer.Thus, addition of weak polar organic solvent in the running bufferwould be beneficial for the elution of highly hydrophobic PAEsfrom PSP. Unfortunately, the organic solvents are not allowedabove 20%, otherwise, the micelle would be destroyed. Thus, thenormal micelles as pseudostationary phase in EKC were limitedto the separation of the highly hydrophobic analytes.Polymer surfactants were firstly used as PSP by Palmer in 1992(Palmer, Khaled, & Mcnair, 1992; Palmer & Mcnair, 1992). Poly(sodium undecylenate) was used as PSP in EKC to separatehydrophobic analytes, such as, polycyclic aromatic hydrocarbons(PAHs), with methanol and acetonitrile as organic additives. Thecontent of organic solvent could be added up to 45%. A typical comparisonbetween polymeric micelles and normal micelle wasreported by Otsuka, Wada, Ishisaka, and Terabe (2002). Poly(sodium 10-undecylenyl sulfate) micelles could tolerate 60% acetonitrilebut SDS micelles could not when separating 11 kinds ofPAHs. Micelles formed by polymer surfactant is referred to asmolecule micelle since the micelle is formed by single molecule,the critical micelle concentration (CMC) is essentially zero.Additionally, the molecule micelle is steady due to the covalentlinkage among hydrophobic moieties. Thus, polymer surfactantsas PSPs have potential advantages including a much lower polymerconcentration required, ignorable variance of ionic strength andviscosity introduced by the polymers, micelle stability in the presenceof high concentration of organic additives.Our group have developed novel PSPs using polymeric aggregatesformed by self-assembly of random amphiphilic copolymers.The random amphiphilic copolymer poly (methyl methacrylateco-methacrylic acid) (P(MMA-co-MAA)) with the monomer ratioof MMA to MAA of 7:3 was used as PSP in EKC to separate 8 kindsof corticosteroids in cosmetics (Xu et al., 2014). Poly (stearylmethacrylate-co-methacrylic acid) (P(SMA-co-MAA)) with themonomer ratio of SMA to MAA of 0.5:9.5 was used as PSP to separate11 kinds of water- and fat-soluble vitamins simultaneously(Ni, Xing, Cao, & Cao, 2014). The advantage of polymeric aggregatePSP is that the selectivity could be adjusted by changing the type ofhydrophobic and hydrophilic monomer, or varying the molar ratioof the hydrophobic monomer to the hydrophilic monomer. Thoughthe PSP for simultaneous analysis of water- and fat-soluble vitaminsin our previous work was not suitable to separate morehydrophobic PAEs, more lipophilic copolymer (P(SMA-co-MAA))with the monomer ratio of SMA to MAA of 1:9 was synthesized.The polymeric aggregate was self-assembled with selective solventapproach, and the polymeric PSP was used in EKC to separate 15kinds of PAEs in the present work.
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