Abstract:
It is disclosed a method for making SPME fibers. The SPME fibers consist of metal-oxide coatings on fused-silica fibers. The coatings are prepared from a water-based solution containing a predetermined amount of metal ion and a predetermined amount of a reactant. The water based solution and the fused-silica fibers are kept at the temperatures below 100° C. for a predetermined time to obtain SPME fibers. The SPME fibers are applied for extraction of pesticides and other organic compounds such as 1,4-dichloro-2-nitrobenzene; Biphenyl; and Acenaphthene in the water based solution and cooling gas of a power generator respectively.

Description:
SPONSORSHIP STATEMENT 
       [0001]    The present invention for international filing is sponsored by The Iranian Nanotechnology initiative Council. 
       FIELD OF INVENTION 
       [0002]    The present invention relates to a stationary phase for Solid Phase Micro Extraction (SPME). 
       BACKGROUND OF THE INVENTION 
       [0003]    Solid-phase micro extraction (SPME) is based on the partition/adsorption of analytes to a stationary phase coated on a fused-silica fiber. SPME is an attractive alternative to traditional sample treatment and preparation methods, because it combines sample extraction, pre-concentration following by sample introduction, altogether into one step and can be readily combined with gas chromatography (GC) or high performance liquid chromatography (HPLC). This method has gained increasing application in many areas including environmental, food and drug analysis. 
         [0004]    Almost all commercially available SPME fibers are based on fused-silica fiber. The coating techniques include pasting with adhesives, electrochemical polymerization or deposition, direct-pasting, chemical corrosion, and the sol-gel technique. 
         [0005]    In general, organic polymers are the most widely used coatings for the extraction of organic compounds. However, some inorganic coatings based on graphite materials and metallic compounds have also exhibited good performance in SPME. 
         [0006]    Adsorption of compounds depends on the functional groups on the stationary phase and surface area. Increasing the surface area increases the sensitivity of analysis and lowers the limit of detection. In this way, metal oxides such as Al 2 O 3 , ZnO, ZrO 2 , and nanostructure PbO 2  prepared by electro-oxidizing or electro-deposition techniques have been used as SPME coatings. Metal oxide-based SPME coatings made of a mixture of Al 2 O 3  on a polyvinylchloride matrix dispersed in tetrahydrofuran and Nb 2 O 5  coating using a metallo-organic decomposition technique have also been successfully used. 
         [0007]    By applying an inexpensive and effective aqueous growth technique at mild temperatures functionalized coating of metal oxide materials on fused silica is achieved. Such a technique allows the generation of advanced nano/micro particulate coatings without using any template, membrane, surfactant, applied external fields, or specific requirements in fused silica activation, thermal stability, or crystallinity. Such a process avoids the safety hazards of organic solvents and their eventual evaporation and potential toxicity. In addition, because no organic solvents or surfactants are present, the purity of the materials is substantially improved. The residual salts are easily washed out by water due to their high solubility. In most cases, no additional heat or chemical treatments are necessary, which represents a significant improvement compared with surfactant, template, membrane base, corrosion or electrochemical synthesis methods. 
         [0008]    The present invention method is applicable to all water-soluble metal ions likely to precipitate in solution. 
         [0009]    Therefore, it would be advantageous to provide a method to overcome the above shortcomings. 
       SUMMARY OF THE INVENTION 
       [0010]    The primary object of the present invention is to provide a method for making SPME fibers. 
         [0011]    Yet another object of the present invention is to provide a method in which by developing 1-D nano structures such as nano-rods and nano-wires of metal oxides, a higher surface area can be achieved. 
         [0012]    Yet another object of the present invention is to provide a method for making nanostructure SnO 2  and ZnO nano-rods grown on fused silica, as a new fiber for solid phase micro extraction (SPME). 
         [0013]    Yet another object of the present invention is to provide a method for preparation of nano stationary phase of SPME with high surface area and high adsorption power of compounds such as pesticides and drugs. 
         [0014]    Yet another object of the present invention is to provide a method for preparation of nano stationary phase of SPME by developing nano structures of metal oxide like nano-rods. 
         [0015]    Yet another object of the present invention is to provide a method for making SPME in which a high pre-concentration and proper clean-up of samples are achieved. 
         [0016]    Yet another object of the present invention is to provide a method for making SPME in which by applying an inexpensive and effective aqueous growth technique at mild temperatures functionalized coating of metal oxide materials on fused silica is achieved. 
         [0017]    Yet another object of the present invention is to provide a method which allows the generation of advanced nano/micro particulate coatings without using any template, membrane, surfactant, applied external fields, or specific requirements in fused silica activation, thermal stability, or crystallinity. 
         [0018]    Yet another object of the present invention is to provide a method which avoids the safety hazards of organic solvents and their eventual evaporation and potential toxicity. 
         [0019]    Yet another object of the present invention is to provide a method to improve the purity of the materials. The residual salts are easily washed out by water due to their high solubility. In most cases, no additional heat or chemical treatments are necessary, which represents a significant improvement compared with surfactant, template, membrane base, corrosion or electrochemical synthesis methods. 
         [0020]    Yet another object of the present invention is to provide a method to improve repeatability and stability of stationary phase. 
         [0021]    Yet another object of the present invention is to provide a stationary phase which consists of metal-oxide (bulk as well as nanostructured) coated fiber for the adsorption of volatile and semi-volatile compounds. 
         [0022]    Yet another object of the present invention is to provide a method for making SPME fibers which extracts the compounds at trace levels. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Example 1 
     Materials and Apparatus 
       [0023]    1,4-dichloro-2-nitrobenzene (DCNB), Biphenyl (BPh), Acenaphthene (ANPh), Tin (IV) chloride pentahydrate and Urea were purchased from Fluka. Zinc nitrate tetrahydrate and Hexamethylenetetramine (HMT) were purchased from Fluka. The SPME Syringe was purchased from Azar Electrode Company (Tabriz, Iran). Fused Silica optical fibers were purchased from Polymicro Technologies Inc (Phoenix, Ariz.). Hydrochloric acid, Methanol and acetone were purchased from Merck. GC-MS separations were carried out by an Agilent Technologies 6890N Network GC System and Agilent Technologies 5973 Network Mass spectrometer. The pyrolyzer was made at the Niro Research Institude (NRI). The insulators were supplied from shahid rajaee Power house (Qazvin, Iran). 
         [0000]    Preparation of SnO 2  SPME fibers
   1) The fused silica fibers were cut into 35 mm lengths and the 15 mm of polymeric cover were removed by immersing to the acetone for 10 min. They were thoroughly rinsed by sonification in diluted hydrochloric acid, acetone and water respectively.   2) The Nanostructured SnO 2  solution was prepared according to Vayssiers method. Briefly, A typical synthesis involved the preparation of a 100 mL aqueous solution (MilliQ+, 18.2 MWcm) consisting of 0.034 g of SnCl 4 .5H2O and 0.920 g of (NH 2 ) 2 CO in presence of 5 mL of fuming HCl (37%) in a closed pyrex bottle with autoclavable screw cap.   3) The prepared fibers were hanged into the mentioned solution for 48 h at the 95° C.   4) After two days, nanostructured SnO 2  SPMEs (NSS-SPME) were washed by MilliQ water at the cleaner Ultrasonic. Conditioning of NSS-SPMEs was performed at the injector of GC-MS with 290° C. temperature for 30 min.   
 
       Extraction Conditions of DCNB, BPh and ANPh 
       [0028]    Extraction of DCNB, BPh and ANPh were performed via Head Space extraction method simultaneously. In this method, percentage of salt (NaCl), extraction temperature, adsorption time and desorption time were optimized. After optimization, 30% (W/V) NaCl were added into a 4 ml of sea water as sample. 10 ml vial containing a magnetic stirrer bar was used in this aim. After addition of an appropriate volume of stock solution, the vial was sealed with a silicon-rubber septum and an alumina cap. The fiber was exposed to the head space of solution by piercing the septum with the SPME needle assembly and then depressing the plunger. The vial was put into the oil bath with 60° C. temperature for 30 min. After extraction, the fiber was withdrawn into the needle and removed from sample vial. The analytes were then thermally desorbed in the GC injector at 250° C. for 20 min. The Caspian Sea water was selected as real sample. 
       Results 
       [0029]    A nanostructure SnO 2  solid phase micro extraction (NSS-SPME) fiber was performed to extract some pesticides such as DCNB, BPh and ANPh from sea water. For the linear study eight concentration solution including: 0.001, 0.01, 10, 1000, 10000, 1×105, 1×106, 1×107, 5×107 ng 1-1, were evaluated and four of them were in the linear range. The linear dynamic ranges (LDR) are 0.1-100 μg1-1 for measurement of all pesticides. The linear regression values, limit of detections (LOD) and relative standard deviations (RSD, n=5) for DCNB, BPh and ANPh were evaluated (Table 1). Also, the RSD values for the separation and measurement of analytes (repeatability for one fiber and fiber-to-fiber RSD) were shown in Table 1 which are quite acceptable. The limits of detection of all pesticides are too low (at the ng1 −1  level). It is due to high surface area for adsorption of pesticides. 
         [0000]    
       
         
               
             
               
               
               
               
             
               
               
               
               
               
               
               
               
             
               
               
               
               
               
               
               
               
             
           
               
                 TABLE 1 
               
             
             
               
                   
               
               
                 Analytical performance of the method for the analysis of DCNB, BPh and ANPh by 
               
               
                 NSS-SPME. 
               
             
          
           
               
                   
                 RSD % 
                   
                   
               
               
                   
                 (n = 5) 
                   
                 Caspian Sea water 
               
             
          
           
               
                   
                 LDR 
                   
                   
                 Fiber-to- 
                 LOD 
                   
                 Recovery 
               
               
                 Analyte 
                 (μgl −1 ) 
                 R 2   
                 One fiber 
                 Fiber 
                 (ngl −1 ) 
                 Found 
                 (%)** 
               
               
                   
               
             
          
           
               
                 1,4-dichloro-2- 
                 0.1-100 
                 0.999 
                 9.8 
                 12.5 
                 10 
                 n.d.* 
                 93 
               
               
                 nitrobenzene 
               
               
                 Biphenyl 
                 0.1-100 
                 0.998 
                 7.7 
                 7.8 
                 0.1 
                 n.d. 
                 97 
               
               
                 Acenaphthene 
                 0.1-100 
                 0.999 
                 4.9 
                 8.9 
                 0.001 
                 n.d. 
                 98 
               
               
                   
               
               
                 *Not detected 
               
               
                 **Recoveries were determined by spiking of 10 μgl −1  of standard solutions. 
               
             
          
         
       
     
       Example 2 
     Monitoring of Insulator Degradation Products of Generator via NSS-SPME 
       [0030]    Generators are most important at the electrical distribution system. Temperature affect on the production power and life time of generator. Cooling fluid is used for decreasing of insulator temperature at the generator. Air and hydrogen are common cooling fluid. Because of some electrical errors, the insulators are pyrolized and produce volatile organic compounds. Accurate determination of these compounds can help to distinguish the life time of generator. In this aim, we tried to develop an off line method to denote volatile organic compounds resulted from pyrolysis of insulator. 
       Sampling Method 
       [0000]    
       
         1) 0.5 gr of insulator was put inside the pyrolyzer and the NSS-SPME was set at the end of the pyrolyzer. 
         2) After 10 min that pyrolyzer reached to 700° C., Helium as carrier gas carried out all of the volatile organic compounds on the NSS-SPME fiber for 5 min. 
         3) After that, The NSS-SPME was taken from pyrolyzer and injected to the GC-MS via SPME syringe. 
       
     
       Results 
       [0034]    There are some volatile organic compounds resulted from pyrolysis of insulator, adsorption of these compounds on the NSS-SPME is related to compound and fiber structures. Analysis by GC-MS showed that the NSS-SPME is capable to adsorb all of the polar and nonpolar compounds. Table 2 shows the list of most compound which resulted from insulator pyrolysis. 
         [0000]    
       
         
               
             
               
               
             
               
               
             
           
               
                 TABLE 2 
               
             
             
               
                   
               
               
                 The list of compounds adsorbed by NSS-SPME 
               
             
          
           
               
                   
                 Compounds name 
               
               
                   
                   
               
             
          
           
               
                 1 
                 Cyclotrisiloxane, hexamethyl 
               
               
                 2 
                 2-Propenoic acid, 2-methyl-, butyl ester 
               
               
                 3 
                 Phenol 
               
               
                 4 
                 Cyclotetrasiloxane, octamethyl 
               
               
                 5 
                 Phenol, 2-methyl- 
               
               
                 6 
                 Hexanoic acid, 2-ethyl- 
               
               
                 7 
                 Cyclopentasiloxane, decamethyl- 
               
               
                 8 
                 Ethanol, 2-phenoxy- 
               
               
                 9 
                 Phenol, 2-ethyl- 
               
               
                 10 
                 O-DIMETHYLAMINOBENZALDEHYDE 
               
               
                 11 
                 Benzene, 2,4-diisocyanato-1-methyl 
               
               
                 12 
                 Tetrasiloxane, decamethyl- 
               
               
                 13 
                 Cyclohexene, 4-methyl- 
               
               
                 14 
                 4-Methoxy-3-(3-methoxyphenyl)-4- 
               
               
                   
                 methylpentan-1-ol 
               
               
                 15 
                 Dibutyl phthalate 
               
               
                 16 
                 N-ethyl-1,3-dithioisoindoline 
               
               
                 17 
                 Cyclohexasiloxane, dodecamethyl- 
               
               
                 18 
                 Benzene, 1,2,4,5-tetramethyl- 
               
               
                   
               
             
          
         
       
     
       Example 3 
     Preparation of Nanorod ZnO-SPME Fibers 
       [0000]    
       
         1) The fused silica fibers were prepared according to instruction described in example 1. 
         2) The nanorod ZnO solution was prepared according to Vayssiers method. Briefly, a typical synthesis involved the preparation of 100 mL aqueous solution (MilliQ+, 18.2 MWcm) 0.005 M of Zn(NO 3 ) 2 .4H 2 O and HMT in a closed pyrex bottle with autoclavable screw cap. 
         3) The prepared fibers were hanged into the mentioned solution for several hours at the 95° C. 
         4) The Nanorod ZnO SPMEs (NRZ-SPME) were washed by MilliQ water at the cleaner Ultrasonic. Conditionings of NRZ-SPMEs were performed at the injector of GC-MS with 290° C. temperature for 30 min. 
       
     
       Extraction Conditions of DCNB, BPh and ANPh 
       [0039]    Extraction of DCNB, BPh and ANPh were performed via Head Space extraction method simultaneously according to the process described in Example 1. 
       Results 
       [0040]    Some nanostructure metal oxides such as nanobelts, nanoribbons, nanodisks, nanosheets, and nanodendrites have low area to extract materials such as pesticides, insecticides and drugs. Development of nanostructure materials to 1-D and 3-D nanomaterials such as nanorods, and nanotubes lead to high surface area to determine trace analysis. In addition to the economical manufacturing of nanomaterials, a better fundamental knowledge of their electronic structure, physical, interfacial, and structural properties, as well as their stability is required to fully exploit their fascinating physical and chemical potential. 
         [0041]    A nanorod ZnO solid phase microextraction (NRZ-SPME) fiber was performed to extract mentioned pesticides from sea water. 
         [0042]    For the linear study eight concentration solution including: 0.001, 0.01, 10, 1000, 10000, 1×105, 1×106, 1×107, 5×107 ng 1-1, were evaluated. The linear dynamic range (LDR) is 100-10000 μg1-1 for DCNB while it is too broader for BPh and ANPh (0.1-10000 μg1-1) than DCNB. LDR for analysis of all pesticides by NRZ-SPME are broader when compare to those of NSS-SPME. The linear regression values, limit of detections (LOD) and relative standard deviations (RSD, n=5) for DCNB, BPh and ANPh were evaluated (Table 3). Also, the RSD values for the separation and measurement of analytes (repeatability for one fiber and fiber-to-fiber RSD) were shown in Table 3. The limit of detection of measurement of BPh by NRZ-SPME is lower than that of NSS-SPME, while the limit of detection of measurement of the other pesticides are the same for both of the fibers. The RSD of measurements by NRZ-SPME for one fiber and fiber to fiber analysis in the same sample are much lower than those of NSS-SPME in the same condition. 
         [0000]    
       
         
               
             
               
               
               
               
             
               
               
               
               
               
               
               
               
             
               
               
               
               
               
               
               
               
             
           
               
                 TABLE 3 
               
             
             
               
                   
               
               
                 Analytical performance of the method for the analysis of DCNB, BPh and ANPh by 
               
               
                 NRZ-SPME. 
               
             
          
           
               
                   
                 RSD % 
                   
                   
               
               
                   
                 (n = 5) 
                   
                 Caspian Sea water 
               
             
          
           
               
                   
                 LDR 
                   
                   
                 Fiber- 
                 LOD 
                   
                 Recovery 
               
               
                 Analyte 
                 (μgl −1 ) 
                 R 2   
                 One fiber 
                 to-Fiber 
                 (ngl −1 ) 
                 Found 
                 (%)** 
               
               
                   
               
             
          
           
               
                 1,4-dichloro-2- 
                   1-10000 
                 0.995 
                 6.5 
                 11.4 
                 10 
                 n.d.* 
                 91 
               
               
                 nitrobenzene 
               
               
                 Biphenyl 
                 0.1-10000 
                 0.999 
                 4.3 
                 7.6 
                 0.001 
                 n.d. 
                 102 
               
               
                 Acenaphthene 
                 0.1-10000 
                 0.999 
                 4.9 
                 7.3 
                 0.001 
                 n.d. 
                 98 
               
               
                   
               
               
                 *Not detected 
               
               
                 **Recoveries were determined by spiking of 10 μgl −1  of standard solutions. 
               
             
          
         
       
     
       Example 4 
     Monitoring the Insulator Degradation Products of Generator by NRZ-SPME 
     Sampling Method 
       [0043]    The sampling process is completely like to example 2. Briefly, 0.5 gr of insulator was sat at the pyrolyzer and the NRZ-SPME was stood at the end of the pyrolyzer. After 10 min that pyrolyzer reached to 700° C., Helium as carrier gas carried out all of the volatile organic compounds on the NRZ-SPME fiber for 5 min. After that, The NRZ-SPME was taken from pyrolyzer and injected to the GC-MS via SPME syringe. 
       Results 
       [0044]    There are only ten volatile organic compounds resulted from pyrolysis of insulator that can be adsorbed by both NRZ-SPME and NSS-SPME. However, both of these fibers are made up of metal oxide, therefore, the capability of adsorption of compounds by these two fibers are different and are due to the type-nanostructure. Adsorption of these compounds on these two fibers depend on compound and fiber structures. Analysis by GC-MS showed that both these SPME fibers are capable to adsorb all of the polar and nonpolar compounds. Table 4 shows the compounds resulted from pyrolysis of insulator and adsorbed by NRZ-SPME. 
         [0000]    
       
         
               
             
               
               
             
               
               
             
           
               
                 TABLE 4 
               
             
             
               
                   
               
               
                 The list of compounds adsorbed by NRZ-SPME 
               
             
          
           
               
                   
                 Compounds name 
               
               
                   
                   
               
             
          
           
               
                 1 
                 2-Propanone 
               
               
                 2 
                 Cyclotrisiloxane, hexamethyl- 
               
               
                 3 
                 Phenol, 4-methyl- 
               
               
                 4 
                 2-Propenoic acid, 2-methyl-, 2- 
               
               
                   
                 methylpropyl ester 
               
               
                 5 
                 Phenol 
               
               
                 6 
                 Cyclotetrasiloxane, octamethyl- 
               
               
                 7 
                 Phenol, 2-methyl- 
               
               
                 8 
                 Phenol, 3-ethyl- 
               
               
                 9 
                 Tetrasiloxane, decamethyl- 
               
               
                 10 
                 Cyclopentasiloxane, decamethyl- 
               
               
                 11 
                 Ethanol, 2-phenoxy- 
               
               
                 12 
                 2,4-DI-(P-HYDROXYPHENYL)-4- 
               
               
                   
                 METHYLPENT-1-ENE 
               
               
                 13 
                 Cyclohexasiloxane, dodecamethyl- 
               
               
                 14 
                 Cyclohexene, 4-methyl- 
               
               
                 15 
                 cis-2-ethyl-3-methyl-6-[(E)-4- 
               
               
                   
                 methylpent-2-en-2-yl]-5,6-dihydro-2H- 
               
               
                   
                 pyran 
               
               
                 16 
                 6-methylthio[1]benzothieno[2,3-c]quinoline 
               
               
                 17 
                 21-(trimethylsilyloxy)medroxyprogesterone-3-methoxime 
               
               
                 18 
                 2-Propenoic acid, 2-methyl-, butyl ester 
               
               
                   
               
             
          
         
       
     
         [0045]    The invention has been described in connection with its preferred embodiments. However, it is not limited thereto. Changes, variations and modifications to the basic design may be made without departing from the inventive concepts in this invention. In addition, these changes, variations and modifications would be obvious to those skilled in the art having the benefit of the foregoing teachings. All such changes, variations and modifications are intended to be within the scope of the invention which is limited only by the following claims.