COLUMN FILLER FOR LIQUID CHROMATOGRAPHY

Abstract

The present invention provides a column filler for liquid chromatography that has a great adsorption capacity, adjustable adsorption selectivity, and high shape retainability and therefore is usable for measurement of various substances and capable of achieving excellent separation performance and a high filling rate in a column when used as a column filler for liquid chromatography. Provided is a column filler for liquid chromatography including carbon-coated porous particles, the carbon-coated porous particles including porous particles each having a coating layer containing an amorphous carbon on a surface.

Claims

1-7. (canceled)

8. A production method of a column filler for liquid chromatography comprising carbon-coated porous particles, the carbon-coated porous particles comprising porous particles each having a coating layer containing an amorphous carbon on a surface, and the method comprising a step of forming an oxazine resin layer on the surface of the porous particles, and a step of heat-treating the oxazine resin to form the coating layer containing an amorphous carbon.

9. The production method of a column filler for liquid chromatography according to claim 8, wherein the carbon-coated porous particles have a specific surface area of 10 to 4,000 m.sup.2/g.

10. The production method of a column filler for liquid chromatography according to claim 8, wherein the porous particles have an average particle size of 10 nm to 500 μm.

11. The production method of a column filler for liquid chromatography according to claim 8, wherein the porous particles have an average pore size of 1 to 200 nm.

12. The production method of a column filler for liquid chromatography according to claim 8, wherein the porous particles and the carbon-coated porous particles have a relationship defined by the following formula:
((average pore size of the porous particles)−(average pore size of the carbon-coated porous particles))×100/(average pore size of the porous particles)=less than 30%.

13. The production method of a column filler for liquid chromatography according to claim 8, wherein the porous particles comprise an inorganic material.

14. The production method of a column filler for liquid chromatography according to claim 13, wherein the inorganic material contains at least one selected from the group consisting of silica, alumina, zirconia, and titania.

Description

DESCRIPTION OF EMBODIMENTS

[0101] Embodiments of the present invention are more specifically described with reference to, but not limited to, the following examples.

Example 1

[0102] To 256.43 g of ethanol were sequentially added 7,054 mg of porous silica particles (available from YMC Co., Ltd., average particle size: 4.4 μm, average pore size: 12.0 nm, specific surface area: 330 m.sup.2/g) and 781 mg of 1,5-dihydroxy naphthalene (available from Tokyo Chemical Industry Co., Ltd.). Thus, a mixed ethanol solution was prepared.

[0103] Next, the obtained mixed solution was treated in an ultrasonic bath for two minutes, and 630 mg of hexahydro-1,3,5-trimethyl-1,3,5-triazine (available from Tokyo Chemical Industry Co., Ltd.) was added thereto. The mixture was stirred under heating at 80° C. for four hours. The solution was filtered, and the resulting solids were washed three times with ethanol and vacuum dried at 25° C. for 24 hours. Thus, carbon-coated porous silica particles (carbon-coated porous particles) were obtained.

[0104] The average particle size, average pore size, specific surface area, and carbon content of the obtained carbon-coated porous silica particles were measured by the following methods. The average particle size was 4.7 μm, the average pore size was 9.69 nm, and the specific surface area was 228.6 m.sup.2/g.

Average Particle Size

[0105] A FE-SEM image of the obtained particles was analyzed using image analysis software (WINROOF available from Mitani Corporation) to measure the average particle size.

Average Pore Size and Specific Surface Area

[0106] The average pore size and specific surface area were measured using a gas-adsorbing type pore size distribution analyzer.

Example 2

[0107] The carbon-coated porous silica particles obtained in Example 1 were fired in a nitrogen atmosphere at 560° C. for two hours. Thus, carbon-coated porous silica particles were obtained.

[0108] The obtained carbon-coated porous silica particles had an average particle size of 4.4 μm, an average pore size of 12.52 nm, and a specific surface area of 281.6 m.sup.2/g.

Example 3

[0109] The carbon-coated porous silica particles obtained in Example 1 were fired in a nitrogen atmosphere at 200° C. for two hours. Thus, carbon-coated porous silica particles were obtained.

[0110] The obtained carbon-coated porous silica particles had an average particle size of 4.5 μm, an average pore size of 9.70 nm, and a specific surface area of 234.4 m.sup.2/g.

Example 4

[0111] The carbon-coated porous silica particles obtained in Example 1 were fired in a nitrogen atmosphere at 400° C. for two hours. Thus, carbon-coated porous silica particles were obtained.

[0112] The obtained carbon-coated porous silica particles had an average particle size of 4.5 μm, an average pore size of 9.78 nm, and a specific surface area of 277.1 m.sup.2/g.

Comparative Example 1

[0113] Commercially available octadecylated silica particles (available from GL Science, particles filled in Inertsil ODS-3) were used.

[0114] The octadecylated silica particles had an average particle size of 5.0 μm.

Comparative Example 2

[0115] Commercially available porous silica particles (available from YMC) were used. The silica particles had an average particle size of 5.0 μm, an average pore size of 12.0 nm, and a specific surface area of 330 m.sup.2/g. cl Evaluation Method

(1) HPLC Separation Test

[0116] The particles of Examples 1 and 2 and Comparative

[0117] Example 1 were separately filled in a stainless-steel column (inner diameter: 4.6 mm, length: 150 mm). Thus, filled columns were prepared. Using these filled columns, the separation states under the measurement conditions of a column temperature of 20° C., a flow rate of 1.0 ml/min, and a measurement time of 60 minutes were observed, and retention factors (k) and separation factors (α) were calculated.

[0118] Two types of test samples including test sample A (benzene, naphthalene, anthracene, cis-stilbene, trans-stilbene, butyl benzene, 1,2,3,4-tetrahydro-naphthalene) and test sample B (naphthalene, anthracene, cis-stilbene, trans-stilbene) were used in the test. In the case of the test sample A, the mobile phase used was ethanol. In the case of the test sample B, the mobile phase used was a solvent mixture containing ethanol and tetrahydrofuran (EtOH/THF=50/50).

[0119] Here, the retention factor k can be calculated by the equation: k=(t.sub.R−t.sub.0)/t.sub.0 (t.sub.R: retention time, t.sub.0: time between introduction of test sample and appearance of peak of component not retained in the column). The separation factor α means the ratio of the retention factors, and is specifically calculated by the equation: α=k.sub.2/k.sub.1 (k.sub.1: retention factor of substance eluted first, k.sub.2: retention factor of substance eluted later). Commonly, “α=1” means that the elution times are the same and the substances are not separated.

[0120] The separation factors a were calculated in relation to “naphthalene and anthracene”, “cis-stilbene and trans-stilbene”, “butyl benzene and 1,2,3,4-tetrahydro-naphthalene”.

[0121] The term “adsorbed” in Table 1 refers to a case where the measurement was not completed in the measurement time (60 minutes). In the case where the retention factor k.sub.2 is “adsorbed”, the separation factor α was infinite.

(2) Column Filling Rate

[0122] In the step of producing filled columns in “(1) HPLC separation test”, the column filling rate was calculated using the following equation in which VO represents the volume of the column before filling and V represents the void volume of the column after filling.

Column filling rate=100×(V0−V)/V0

[0123] The void volume V of the column after filling can be estimated from the volume of the solvent that is not retained in “(1) HPLC separation test”.

(3) G/D Band Peak Intensity Ratio

[0124] The peak ratio between G band and D band of the obtained particles was measured by Raman spectroscopy using Almega XR (available from Thermo Fisher Scientific Inc.), and the peak intensity ratio between G band and D band was calculated. The laser light used had a wavelength of 530 nm.

(4) TOF-SIMS Measurement

[0125] The mass spectrum derived from the benzene ring (at around 77.12) and the mass spectrum derived from the naphthalene ring (at around 127.27) of the coating layer of the obtained particles were confirmed by time-of-flight secondary ion mass spectrometry (TOF-SIMS) using TOF-SIMS 5 (available from ION-TOF GmbH). The TOF-SIMS measurement was performed under the following conditions. For avoiding contamination derived from the air or the storage case as far as possible, the produced sample was stored in a clean case for storing silicon wafers.

Primary ion: 209Bi+1

[0126] Ion voltage: 25 kV
Ion current: 1 pA
Mass range: 1 to 300 mass
Analysis area: 500×500 μm
Charge prevention: Neutralization by electronic irradiation Random raster scan

(5) X-Ray Diffraction

[0127] The diffraction data was obtained using an X-ray diffractometer (SmartLab Multipurpose available from Rigaku Corporation) under the measurement conditions including the X-ray wavelength of CuKα 1.54A, measurement range of 2θ=10° to 70°, scanning speed of 4°/min, and step of 0.02°.

[0128] Whether or not the peak was detected at a position where 2θ is 26.4° in the obtained diffraction data was determined.

TABLE-US-00001 TABLE 1 Example Example Example Example Comparative Comparative 1 2 3 4 Example 1 Example 2 Particles Material Silica Silica Silica Silica Silica Silica before Average particle size (μm) 4.4 4.4 4.4 4.4 5.0 5.0 coating Average pore size (nm) 12.0 12.0 12.0 12.0 — 12.0 Specific surface area (m.sup.2/g) 330 330 330 330 — 330 Coating Material Amor- Amor- Amor- Amor- Chemically — layer phous phous phous phous modified carbon carbon carbon carbon with Measure- G/D band peak intensity ratio — 1.5 1.7 2.2 octadecylsilyl — ment TOF-SIMS Benzene ring Detected Detected Detected Detected group Not detected measurement Naphthalene Detected Detected Detected Detected Not detected ring X-ray diffraction Not Not Not Not Not detected detected detected detected detected Coated Firing temperature (° C.) — 560 200 400 — — particles Firing time (hour) — 2 2 2 — — Average particle size (μm) 4.7 4.4 4.5 4.5 — — Average pore size (nm) 9.69 12.52 9.70 9.78 — — Specific surface area (m.sup.2/g) 228.6 281.6 234.4 277.1 — — Difference in specific surface area before 101.4 48.4 95.6 52.9 — — and after coating (m.sup.2/g) Eval- Separation Test Benzene Retention factor 0.11 0.45 — — 0.24 — uation test sample Naphthalene Retention factor 0.40 Adsorbed — — 0.33 — A Anthracene Retention factor 1.25 Adsorbed — — 0.48 — Separation factor 3.13 — — — 1.45 — cis-stilbene Retention factor 0.29 4.90 — — 0.35 — trans-stilbene Retention factor 0.58 Adsorbed — — 0.40 — Separation factor 2.00 Infinite — — 1.14 — Butylbenzene Retention factor 0.11 1.07 — — 0.38 — 1,2,3,4- Retention factor 0.20 0.58 — — 0.44 — tetrehydro- nephthalene Separation factor 1.82 1.84 — — 1.16 — Test Naphthalene Retention factor — 1.05 — — — — sample Anthracene Retention factor — 13.60 — — — — B Separation factor — 12.95 — — — — cis-stilbene Retention factor — 0.20 — — — — trans-stilbene Retention factor — 1.96 — — — — Separation factor — 9.80 — — — — Column filling rate 25.0 15.8 — — 27.8 —

INDUSTRIAL APPLICABILITY

[0129] The present invention can provide a column filler for liquid chromatography that has a great adsorption capacity, adjustable adsorption selectivity, and high shape retainability and therefore is usable for measurement of various substances and capable of achieving excellent separation performance and a high filling rate in a column when used as a column filler for liquid chromatography.