Method and apparatus for mass injection of sample

To enable the mass injection of a sample in a gas chromatography and prevent occurrence of residue or decomposition of a desired constituent during analysis. The invention calls for providing the injection port with a liner, connecting the column and the liner to a press-fit, evaporating the solvent introduced into the liner, and discharging the evaporated solvent from a discharge port formed at the upper part of the liner.

FIELD OF THE INVENTION
 The present invention relates to a method and an apparatus for mass
 injection of a sample.
 BACKGROUND OF THE INVENTION
 One of typical methods of injecting a large quantity of sample during gas
 chromatography is a PTV (programmed temperature vaporizer) method with or
 without a split for discharging the solvent. This method calls for a liner
 disposed at the injection port, and filling the liner with a filler in
 order to introduce as much sample as possible into the injection port.
 When in use, the temperature in the injection port has to be maintained so
 as not to exceed the boiling point of the solvent for the sample. Said
 method then calls for injecting a great quantity of sample into the
 injection port so that the sample is retained in the filler; introducing a
 great quantity of carrier gas in the state where the temperature is still
 maintained low so that most of the solvent is discharged through a vent
 line and that the system becomes a splitless state; and introducing the
 desired constituent that is trapped in the filler in the liner into a
 column while increasing the temperature in the injection port. Other than
 the PTV method, various methods on which research and investigations have
 conventionally been conducted include the on-column mass injection method,
 which calls for increasing the temperature of the oven and causing
 pressure equilibrium of the sample in the column in order to remove only
 the solvent.
 A method which calls for filling a split liner with glass wool, a collector
 or the like to discharge the solvent presents the possibility of the
 desired constituent remaining in the filler or being decomposed during the
 thermal desorption process. It is a common knowledge that decomposition
 actually occurs with some agricultural chemicals. On the other hand, the
 on-column mass injection method presents a problem in that it takes a long
 period of time to remove the solvent. Furthermore, as it is difficult to
 fulfill the conditions for attaining equilibrium in the column, the
 desired constituent tends to spread into a wide area, thereby
 necessitating re-condensation.
 SUMMARY OF THE INVENTION
 In order to solve the above problems, an object of the present invention is
 to provide a sample injection method and an apparatus for mass injection
 of a sample, wherein the time required by elimination of a solvent can be
 reduced by using a splitless liner which is capable of split-purging and
 by discharging the solvent through the opening of a split purge; no filler
 is used so that occurrence of residue or decomposition of the desired
 constituent is prevented; the manner of concentration is at-column
 concentration conducted at a point in the column so that there is no need
 of a separate process of re-concentration; there is virtually no influence
 of the injection rate; and mass injection of a sample is possible. The
 first feature of the invention lies in providing the injection port with a
 liner, connecting the column and the liner to a press-fit, evaporating the
 solvent introduced into the liner, and discharging the evaporated solvent
 from a discharge port formed at the upper part of the liner. The second
 feature of the invention lies in providing the injection port with a
 liner, connecting the column and the liner to a press-fit, introducing a
 solvent and a sample into the liner and controlling the respective
 temperatures in the injection port and the oven so as to discharge the
 evaporated solvent from a discharge port formed at the upper part of the
 liner while accumulating and concentrating the desired constituent in the
 sample at the entrance of the column. The third feature of the invention
 lies in limiting the temperature in the injection port to no higher than
 the boiling point of the solvent and the temperature of the oven to no
 lower than the boiling point of the solvent. The fourth feature of the
 invention lies in providing the injection port with a liner, connecting
 the column and the liner to a press-fit, providing the body of the
 injection port with a split, and forming a discharge port for discharging
 vapor of evaporated solvent at the upper part of the liner.
 DETAILED DESCRIPTION OF THE INVENTION

An embodiment of the present invention is explained hereunder.
 Numeral 1 denotes the body of an injection port in the shape of a hollow
 cylinder. Injection port body 1 is made of glass or quartz and liner 6 is
 made of glass, quartz or metal for example steel, stainless steel. The top
 of the injection port body 1 is provided with a septum 2 and communicates
 with a carrier gas inlet 3 and a septum purge 4. Numeral 5 denotes a split
 purge, which is formed at the upper part of the injection port body 1.
 Numeral 6 represents a liner, which is inserted through the injection port
 body 1 and fastened therein with a cap nut 8. An O-ring 7 is disposed
 between the liner 6 and the cap nut 8. An opening 61 is formed at the top
 of the liner 6, while the bottom of the liner 6 is formed into a press-fit
 62 so that a pre-column 9 may snugly be inserted thereinto. Although the
 pre-column 9 is used with a main column connected thereto under normal
 circumstances, it is possible to omit the pre-column 9 so that the main
 column alone may be inserted and fastened directly in the press-fit 62.
 Therefore, the term `column` refers to a combination of a pre-column and a
 main column, or, in case no pre-column is used, the main column. The
 bottom of the injection port body 1 is immovably attached to an oven 10.
 The liner 6 is also provided with a discharge port 63, which is located at
 the upper part of the liner 6. Although the discharge port 63 may have any
 desired shape, examples of which include, but not limited to, a through
 hole, a slit and a gap, it is required to have such a shape as to enable
 the discharge of vapor resulting from evaporation of the solvent.
 Furthermore, it is advisable to form the discharge port 63 at a location
 where the solvent may vaporize and be discharged, desirably above the
 surface of the solvent and below the opening 61. Although it is convenient
 to form the split purge 5 and the discharge port 63 at the same height, it
 is not a requirement.
 Instead of specifically providing the liner 6 with a discharge port 63, the
 opening 61 at the upper end of the liner 6 may be used as a discharge
 port. In this case, a liner 6 having no special solvent discharge port is
 installed on a septum purge line 4, and elimination of the solvent is
 conducted by purging solvent vapor from the septum purge line 4. A tapered
 narrow portion 64 may be formed immediately above the press-fit 62 of the
 liner 6, and a resistance member 65 made of a glass bead or other
 appropriate material may be placed in the narrow portion 64. (See FIG. 4)
 In cases where a mass spectrometer is used as the detector, the carrier
 gas flows at a constant rate (0.5 ml/min.), because the entrance of the
 capillary column is in a vacuum. Should a sample be injected in this
 state, the sample in the state of a liquid tends to flow toward the column
 before the solvent is sufficiently heated. The above configuration shown
 in FIG. 4, wherein a glass bead is inserted to create resistance against
 the liquid sample, is capable of preventing the sample in the state of a
 liquid from flowing into the column. The above configuration has another
 benefit in that it provides resistance against the vertical vibration of
 the solvent after the solvent is injected.
 It is recommended to provide an apparatus having any one of the
 configurations described above with a back-flush line 11 as shown in FIG.
 5. To be more specific, the portion where the back-flush line 11 is
 connected to the pre-column 9 or the pre-column 9 and the main column is
 formed into a T-connection 111. The back-flush line 11 is formed by
 connecting a gas supply 112, which is adapted to feed the carrier gas or
 the like, to the T-connection 111 through a pressure regulator 113
 comprised of a back pressure valve or the like, and a valve 114, which may
 be an electromagnetic valve. Although the T-connection 111 may be disposed
 in the oven 10, the back-flush line 11 has to be positioned outside the
 oven 10. The apparatus tends to become dirty when mass injection is
 conducted, and the above configuration, wherein the portion where the
 pre-column and the main column are connected is formed into a T-connection
 and connected to a back-flush line, is particularly effective in removing
 the contaminants. After the elimination of the solvent and the
 introduction of the desired constituent into the main column are
 completed, back-flushing is conducted to remove the contaminants.
 EXAMPLE
 Next, a detailed explanation is given of a method according to the
 invention, which uses an apparatus structured as described above.
 A solvent and a sample are injected into the liner in a conventional
 manner. At that time, it is necessary that the temperature in the liner 6
 be lower than the boiling point of the sample solvent and that the boiling
 point of the sample be higher than that of the solvent. The temperature of
 the interior of the oven 10 has to have been set higher than the boiling
 point of the solvent in order to prevent the solvent from flowing into the
 pre-column. For example, if acetone is used as the solvent in the state
 where the pressure of the carrier gas is 100 kPa, the solvent is in the
 state of a liquid with its vapor pressure being 72 kPa, when the
 temperature is 73.degree. C. When the temperature is 78.degree. C., the
 solvent is in the boiling state, i.e. a mixture of liquid and gas, with
 its vapor pressure being 100 kPa. At a temperature of 78.degree. C., the
 solvent is in the gaseous state with its vapor pressure being 125 kPa. In
 other words, when the temperature in the injection port is maintained at
 73.degree. C., the acetone is in the state of a liquid and will not boil.
 However, the acetone evaporates so that its vapor pressure reaches 72 kPa.
 The acetone vapor exits from the discharge opening 63 and is discharged
 through the split purge 5 of the injection port body 1.
 The acetone is discharged in a dispersed state with the vapor pressure of
 72 kPa at 73.degree. C. Therefore, given that split purge 5 has a
 discharge flow rate of 50 ml/min. and that the carrier gas is helium (He),
 the acetone is discharged at a rate of 10 ml/min. in the form of gas, even
 if He:acetone=8:2. When 100 .mu.l of acetone completely vaporizes, it is
 calculated that its volume is increased to 33 ml. Therefore, it takes
 three minutes to complete the discharge. At a pressure of 100 kPa and a
 temperature of 78.degree. C., the pressure reaches equilibrium between the
 liquid acetone and the part where the acetone is boiling. While this
 equilibrium is maintained, the acetone is discharged at a rate equivalent
 to the flow rate of the column, e.g. 1.5 ml/min. until the desired
 constituent, i.e. the component that is desired to be obtained, finally
 remains in the pre-column and becomes concentrated. Then, thermal
 desorption of the concentrated desired constituent is conducted by
 increasing the temperature of the oven 10.
 The state described above is explained in detail, referring to FIGS. 2A-2D.
 Because of the pressure equilibrium, the injected sample, which is still in
 the form of a liquid, remains in the liner and becomes concentrated, while
 the solvent alone vaporizes.
 When the solvent is on the point of flowing toward the column, where the
 oven is installed, the solvent is pushed back by the vapor pressure,
 because the temperature of the oven is higher than the boiling point of
 the solvent. Should the solvent be pushed back too further, it is then
 pushed toward the oven, because the pressure of the carrier gas exceeds
 the pressure of the solvent vapor due to the low temperature in the
 injection port. Thus, the liquid (the sample) is retained at a point in
 the column, i.e. a location where its temperature is such that the
 pressure of the carrier gas is balanced with the pressure of the solvent
 vapor. The removal of the solvent is underway also at each portion
 enclosed with a circle and identified by the letter B. Turning to FIGS. 2A
 and 2B, although the solvent does not boil in the injection port, there is
 constant evaporation of the solvent. The solvent vapor resulting from the
 evaporation is removed through the split purge. The removal of the solvent
 at this portion, each of which portion is enclosed with a circle and
 identified by the letter A in these figures, is roughly several times more
 efficient than the removal of the solvent at the location B. As indicated
 in FIG. 2D, the desired constituent accumulated and concentrated here
 undergoes thermal desorption by increasing the temperature of the oven.
 Next, another embodiment shown in FIG. 6 is explained hereunder.
 Although the temperature of the oven has to be higher than the boiling
 point of the solvent according to the embodiments described above, using a
 back-flush line 11 enables the elimination of the solvent even when the
 temperature of the oven is not higher than the boiling point of the
 solvent.
 The liner 6 includes a middle chamber 67, which is defined by a narrow
 portion 64 formed above the press-fit 62 and a second narrow portion 66
 tapered upward and located at an appropriate distance from the narrow
 portion 64. A resistance member 65 made of a glass bead or other
 appropriate material is placed in the middle chamber 67. It is recommended
 to form the second narrow portion 66 in two or more parts so as to enable
 the positioning of the resistance member. The second narrow portion 66 may
 then be formed by insertion or screwing.
 The back-flush line 11 shown in FIG. 6 may have the same structure as that
 shown in FIG. 5. According to the present embodiment, the pressure of
 back-flush causes the resistance member 65 to move into the second narrow
 portion 66 and close the same, thereby blocking off the middle chamber 67
 and the portion located underneath the middle chamber 67 so that the
 sample can be retained therein.
 When the apparatus described above is used, it is not always necessary to
 control the temperature of the oven, and the solvent is prevented from
 flowing into the oven by a physical means, i.e. action of the resistance
 member 65. Therefore, the temperature of the oven may be set low.
 Referring to FIG. 16, the resistance member 65 is comprised of a core 651,
 which is formed of iron or other metal, and a coated layer 652 formed by
 coating the surface of the core 651 with an inert material, such as glass
 or quartz or ceramic precursor polysilazane.
 Numeral 653 denotes a magnet, which may be an electromagnet. The magnet 653
 is disposed outside the injection port body 1, at a location corresponding
 to the resistance member 65. The magnet 653 is either immovably positioned
 or is capable of moving up and down so that the resistance member 65 can
 be used for opening or closing the second narrow portion 66 and the
 press-fit 62; in other words, the second narrow portion 66 and the
 press-fit 62 can be opened or closed by using vertical movement or turning
 on and off of the magnet 653 of the resistance member 65.
 Sample can be retained in liner 6 and the solvent is underway. Therefore,
 it is not always necessary to install a back-flush line 11 to open or
 close the second narrow portion 66.
 Examples of G.C. Criteria
 Pre-column: inactive silica capillary tube (a product of G.L. Science)
 having a length of 0.5 m.times.0.53 mm inside diameter
 Main column: NB-5 (a product of G. L. Science) having a length of 30
 m.times.0.40 mm inside diameter
 Oven temperature: 82.degree. C. (5 min.).fwdarw.(20.degree.
 C./min.).fwdarw.300.degree. C. (6 min.)
 Temperature in injection port: 73.degree. C. (5 min.).fwdarw.(30.degree.
 C./min.).fwdarw.250.degree. C. (6 min.)
 Pressure in injection port: 100 kPa (5 min.).fwdarw.160 kPa (6 min.)
 Method of injection: split method (1:50 ml) 100 .mu.l
 The G.C. criteria for the present experiment have to be set so as to
 condense the desired constituent by evaporating only the solvent while
 maintaining the position of the solvent in the 0.53 mm ID pre-column as
 much as possible. Therefore, the program of the injection temperature, the
 pressure in the injection port and the temperature of the oven is
 explained hereunder, wherein the process to conduct evaporation of the
 solvent and concentration of the desired constituent is referred to as the
 first stage, and the separation measurement process is referred to as the
 second stage.
 Injection Temperature Program
 In the first stage, the temperature in the injection port is set lower than
 the boiling point of the solvent which corresponds to the current pressure
 in the injection port and the current temperature of the oven in order to
 prevent the solvent from boiling and enable it to remain in the liner in
 the form of a liquid when the solvent is injected into the liner. However,
 if the temperature in the injection port is set too low, it takes an
 exceedingly long period of time for the temperature in the injection port
 to decrease to the set temperature when the subsequent analysis is
 conducted. In the second stage, the temperature in the injection port is
 set higher than the temperature of the oven.
 Program of Pressure in Injection Port
 The pressure in the injection port in the first stage is set slightly
 higher than the pressure of the solvent vapor in order to prevent the
 solvent from boiling. In the second stage, the pressure is set so that the
 column flow rate is approximately 1 ml/min. in accordance with the
 temperature of the oven and that the linear velocity is in the range from
 25 to 50 cm/sec.
 Oven Temperature Program
 In the first stage, the temperature of the oven is set higher than the
 boiling point of the solvent at the current pressure in the injection port
 in order to permit the solvent alone to evaporate while maintaining the
 position of the solvent in the 0.53 mm ID pre-column as steadily as
 possible by using the pressure. In the second stage, the temperature of
 the oven is increased in accordance with the column and the desired
 constituent.
 Next, results of test conducted on various solvents are as follows:
 Acetone
 Criteria for Measurement Using GC/MS and Optic2-300
 Apparatus for PTV Injection: Optic2-300
 Gas chromatograph: HP5890 II FID
 Pre-column: inactivated capillary column 0.53 mm I.d.times.0.5 m
 Main column: NB-5 0.25 mm I.d.times.30 m, 0.4 .mu.m
 Carrier gas: He, 40 kPa (3 min.)-8 kPa/min.-200 kPa
 Oven temperature: 70.degree. C. (3.5 min.)-15.degree. C./min.-300.degree.
 C. (4 min.)
 Injection temperature: 65.degree. C. (3 min.)-60.degree.
 C./min.-280.degree. C. (4 min.)
 Injection mode: Split 30 ml/min.
 Based on the above criteria, a test was conducted, using 1 ng/.mu.l (1 ppm)
 of straight chain hydrocarbon C10-30 (even numbers only) as the sample.
 The results of the test are shown in FIG. 7.
 Dichloromethane
 Criteria for Measurement Using GC/MS and Optic2-300
 Apparatus for PTV Injection: Optic2-300
 Gas chromatograph: HP5890 II FID
 Pre-column: inactivated capillary column 0.53 mm I.d.times.0.5 m
 Main column: NB-5 0.25 mm I.d.times.30 m, 0.4 .mu.m
 Carrier gas: He, 40 kPa (3 min.)-8 kPa/min.-200 kPa
 Oven temperature: 54.degree. C. (3.5 min.)-15.degree. C./min.-300.degree.
 C. (4 min.)
 Injection temperature: 48.degree. C. (3 min.)-60.degree.
 C./min.-280.degree. C. (4 min.)
 Injection mode: Split 30 ml/min.
 Based on the above criteria, a test was conducted, using 1 ng/.mu.l (1 ppm)
 of straight chain hydrocarbon C10-30 (even numbers only) as the sample.
 The results of the test are shown in FIG. 8.
 Ethyl acetate
 Criteria for Measurement Using GC/MS and Optic2-300
 Apparatus for PTV Injection: Optic2-300
 Gas chromatograph: HP5890 II FID
 Pre-column: inactivated capillary column 0.53 mm I.d.times.0.5 m
 Main column: NB-5 0.25 mm I.d.times.30 m, 0.4 .mu.m
 Carrier gas: He, 40 kPa (3 min.)-8 kPa/min.-200 kPa
 Oven temperature: 92.degree. C. (3.5 min.)-15.degree. C./min.-300.degree.
 C. (4 min.)
 Injection temperature: 86.degree. C. (3 min.)-60.degree.
 C./min.-280.degree. C. (4 min.)
 Injection mode: Split 30 ml/min.
 Based on the above criteria, a test was conducted, using 1 ng/.mu.l (1 ppm)
 of straight chain hydrocarbon C10-30 (even numbers only) as the sample.
 The results of the test are shown in FIG. 9.
 Test 1 according to the invention
 Criteria for Measurement Using GC/MS and Optic2-300
 Apparatus for PTV Injection: Optic2-300
 Gas chromatograph: HP5890 II FID
 Main Spectrometer: HP5791
 Pre-column: inactivated capillary column 0.53 mm I.d.times.0.5 m
 Main column: NB-5 0.25 mm I.d.times.30 m, 0.4 .mu.m
 Carrier gas: He, 40 kPa (3 min.)-8 kPa/min.-200 kPa
 Oven temperature: 80.degree. C. (4 min.)-20.degree. C./min.-230.degree. C.
 (1 min.)-30.degree. C./min.-300.degree. C. (6 min.)
 Injection temperature: 72.degree. C. (3 min.)-60.degree.
 C./min.-280.degree. C. (4 min.)
 Injection mode: Split 30 ml/min.
 Surface temperature: 300.degree. C.
 Method: SIM
 Sample: standard sample (pollutants in the air in the room) 100 .mu.l
 Solvent: acetone
 A test on the embodiment resulted in extremely precise analysis, which is
 shown in FIG. 10.
 Test 2 according to the invention
 Criteria for Measurement Using GC/MS and Optic2-300
 Apparatus for PTV Injection: Optic2-300
 Gas chromatograph: HP5890 II FID
 Main Spectrometer: HP5791
 Pre-column: inactivated capillary column 0.53 mm I.d.times.0.5 m
 Main column: NB-5 0.25 mm I.d.times.30 m, 0.2 .mu.m
 Carrier gas: He, 30 kPa (3 min.)-60 kPa (0.5 min.)-7 kPa
 Oven temperature: 70.degree. C. (3.5 min.)-15.degree. C./min.-200.degree.
 C. (3 min.)-5.degree. C./min.-235.degree. C.-15.degree.
 C./min.-280.degree. C. (3 min.)
 Injection temperature: 62.degree. C. (3 min.)-60.degree.
 C./min.-280.degree. C. (4 min.)
 Injection mode: Split 30 ml/min.
 Surface temperature: 300.degree. C.
 Method: SCAN
 Sample: standard sample (agricultural pesticide prone to thermal
 decomposition) 100 .mu.l
 Solvent: acetone
 Test results verify that the above embodiment enables the precise analysis
 even on a substance which would be decomposed by heat in cases where the
 analysis is conducted according to a method using a filler. Test results
 are shown in FIG. 11.
 Next, tests were conducted on identical samples in accordance with
 different injection methods, i.e. an on-column method, a solvent discharge
 PTV method using a filler, and a method according to the invention.
 Test
 Samples were produced by adding C.sub.20 serving as an internal standard to
 each chemical selected from the group consisting of DEP, .alpha.-BHC,
 .beta.-BHC, TPN, iprodione, EPN and phosalone, all of which are
 agricultural chemicals that are easy to decompose during analysis, and
 diluting each mixture with acetone. By using a PTV injection port (Optic
 2-300) as the injection port for each test, 2 .mu.l, 100 .mu.l and 100
 .mu.l of each sample was analyzed according to the on-column method, the
 PTV mass injection method using a filler, and the method according to the
 invention respectively, and a comparative evaluation was conducted
 regarding decomposition characteristics resulting from these methods. 48 g
 of Tenax TA 60-80 mesh was used as the PTV filler.
 Test Results and Evaluation
 The chromatograms obtained by the methods specified above are respectively
 shown in FIGS. 12, 13 and 14.
 The on-column injection method shown in FIG. 12 calls for introducing a
 sample directly into a capillary column. As the temperature in the
 injection port is set low, no decomposition occurs in the injection port.
 On the other hand, mass injection is not possible, because the quantity of
 the sample that can be injected according to this method is limited to
 only 1 to 2 .mu.l. As it is evident from comparison with C.sub.20, the
 tests by the conventional PTV mass injection method shown in FIG. 13
 resulted in complete decomposition of DEP, EPN and iprodione, and
 semi-decomposition of .alpha.-BHC, .beta.-BHC and TPN. As shown in FIG.
 14, the tests conducted by the injection method according to the invention
 not only produced results similar to those in FIG. 12, i.e. the analysis
 obtained through the on-column method or the like, but also enabled the
 injection of a large quantity of sample, i.e. 100 .mu.l. Comparison of
 characteristics of decomposition of the agricultural chemicals resulting
 from said injection methods is shown in FIG. 15.
 These results show that the PTV mass injection method using a filler brings
 about decomposition of samples. However, results of the tests conducted by
 the injection method according to the present invention were similar to
 those obtained through the on-column method and caused virtually no
 decomposition. This is probably because the injection method according to
 the invention is the same as the on-column method in principle, except for
 the process of elimination of the solvent. Therefore, the injection method
 according to the invention has proved to be suitable for mass injection
 sensitive analysis of agricultural chemicals, which are easy to decompose
 during analysis.
 As described above, on aspect of the invention calls for providing the
 injection port with a liner, connecting the column and the liner to a
 press-fit, evaporating the solvent introduced into the liner, and
 discharging the evaporated solvent from a discharge port formed at the
 upper part of the liner. As the evaporated solvent is thus discharged
 quickly from the discharge port of the liner, the solvent can be removed
 in a short period of time, even if a great quantity of solvent is
 injected. Therefore, the invention is capable of coping with high speed
 injection and mass injection of samples.
 Another aspect of the invention is also directed to providing the injection
 port with a liner, connecting the column and the liner to a press-fit,
 introducing a solvent and a sample into the liner and controlling the
 respective temperatures in the injection port and the oven so as to
 discharge the evaporated solvent from a discharge port formed at the upper
 part of the liner while accumulating and concentrating the desired
 constituent in the sample at the entrance of the column. As the method
 according to the invention is adapted to concentrate a sample without
 using a filler, it is free from the possibility of occurrence of residue
 or decomposition of the desired constituent. The invention also enables
 the reduction of the time required by elimination of the solvent by using
 a splitless liner which is capable of split-purging, or by discharging the
 solvent through a split purge. Furthermore, the invention is adapted to
 conduct at-column concentration at a point in the column, there is no need
 of a special, separate process of re-concentration. Furthermore, when a
 sample or other necessary substance is injected into the liner, there is
 virtually no influence of the injection rate. Yet another benefit of the
 method according to the invention lies in its efficiency: it permits
 injection to be conducted in several times and is easy to conduct mass
 injection and therefore free from the problems that are inevitable with
 the at-column method. In addition, it permits mass injection of samples.
 Another aspect of the invention may limit the temperature in the injection
 port to no higher than the boiling point of the solvent and the
 temperature of the oven to no lower than the boiling point of the solvent,
 retaining the sample in the liner and the column causes the solvent in the
 sample to evaporate at a constant vapor pressure so that the solvent in
 the liner is removed through the split purge.
 In the invention, the injection port may be provided with a liner; the
 column and the liner are connected to the press-fit; the body of the
 injection port is provided with a split; and a discharge port for
 discharging vapor of evaporated solvent is formed at the upper part of the
 liner. Therefore, there is no need of a liner having a special shape or
 dimensions, and a liner having normal dimensions is sufficient. In
 addition, the invention ensures steady positioning of the liner and easy
 insertion of a syringe, and provides an apparatus which is easy to produce
 and convenient to handle.
 Also according to the invention, a resistance member 65 comprised of a
 glass bead or the like creates resistance against the liquid sample and is
 thus capable of preventing the sample in the state of a liquid from
 flowing into the column. The resistance member 65 also provides resistance
 against the vertical vibration of the solvent after the solvent is
 injected. Therefore, the invention as claimed in claim 4 or claim 8 is
 also applicable to cases where a mass spectrometer is used as the
 detector.
 Also in the invention, contaminants accumulated in the pre-column, the
 liner, etc. due to mass injection of a sample or other substance can be
 removed by means of the back-flush line.
 Also according to the invention, the pressure of back-flush causes the
 resistance member 65 to move into the second narrow portion 66 and close
 the same, so that the sample is retained therein. Therefore, it is not
 always necessary to control the temperature of the oven. As the solvent is
 prevented from flowing into the oven by the resistance member 65, the
 temperature of the oven is permitted to be set low.