Method for preparing a monolithic stationary phase, associated method for producing a chromatography column and associated separation method

Abstract

The invention relates to a method for preparing a monolithic stationary phase in the interior volume of a chromatography column made of thermoplastic polymer. This method comprises the following steps: (i) modifying the inner wall of the chromatography column by implementing the following steps: (a) preparing a polymerizable anchoring composition comprising at least one particular methacrylate monomer, one or more solvents and 2,2-dimethoxy-2-phenylacetophenone, (b) depositing, on the inner wall of the column, the polymerizable anchoring composition prepared in step (a), and (c) polymerizing the polymerizable anchoring composition by irradiation with ultraviolet radiation; (ii) introducing, into the interior volume of the column, a polymerizable monolith synthesis composition comprising first and second particular (meth)acrylate monomers, one or more pore-forming agents and a free-radical polymerization initiator; and (iii) polymerizing the polymerizable monolith synthesis composition. The invention also relates to a method for producing a chromatography column comprising such a monolithic stationary phase and to a chromatographic separation method using such a column.

Claims

1. A method for producing a chromatography column, the method comprising: (1) preparing a monolithic stationary phase within the interior volume of the chromatography column, the chromatography column comprising a thermoplastic polymer, by implementing the following successive steps (i) to (iii): (i) modifying an inner wall of the chromatography column by implementing the following successive steps (a) to (c): (a) preparing a polymerizable anchoring composition comprising: at least one (meth)acrylate monomer selected from the group consisting of ethylene glycol dimethacrylate, 1,4-butanediol diacrylate, triethylene glycol dimethacrylate, and trimethylolpropane trimethacrylate, one or more solvents, and 2,2-dimethoxy-2-phenylacetophenone, (b) depositing, on the inner wall of the chromatography column, the polymerizable anchoring composition prepared at step (a), and (c) polymerizing the polymerizable anchoring composition via ultraviolet radiation: (ii) placing a polymerizable monolith synthesis composition in the interior volume of the chromatography column, the polymerizable monolith synthesis composition comprising: a first (meth)acrylate monomer selected from the group consisting of ethylene glycol dimethacrylate, 1,4-butanediol diacrylate, triethylene glycol dimethacrylate, and trimethylolpropane trimethacrylate, a second meth(acrylate) monomer selected from the group consisting of methacrylate, methacrylate, lauryl methacrylate, butyl methacrylate, 2-hydroxyethyl methacrylate, polyethylene glycol di(meth)acrylate, bisphenol A-glycidyl methacrylate, and hexyl acrylate, one or more pore-forming agents, and a radical polymerization initiator; and (iii) polymerizing the polymerizable monolith synthesis composition, and (2) functionalizing the monolithic stationary phase prepared at (1) by at least one extractant.

2. The production method according to claim 1, wherein the thermoplastic polymer of the chromatography column is selected from the group consisting of a poly(methyl methacrylate), a polyethylene, a polypropylene, and a cyclic olefin copolymer.

3. The production method according to claim 1, wherein, at step (a), the at least one (meth)acrylate monomer is ethylene glycol dimethacrylate.

4. The production method according to claim 1, Wherein, at step (a), the one or more solvent is at least one selected from the group consisting of methanol, ethanol, 1-propanol, 1,4-butanediol, cyclohexanol, 1-decanol, acetonitrile, toluene, and iso-octane.

5. The production method according to claim 1, wherein, at step (a), the mass proportion of the one or more solvents relative to the total mass of the polymerizable anchoring composition is between 50 mass % and 90 mass %.

6. The production method according to claim 1, wherein, at step (a), the mass proportion of 2,2-dimethoxy-2-phenylacetophenone relative to the total mass of the polymerizable anchoring composition is between 5 rims % and 15 mass %.

7. The production method according to claim 1, wherein the wavelength of ultraviolet radiation applied at step (c) is between 320 nm and 400 nm.

8. The production method according to claim 1, wherein, at step an ultraviolet irradiation time is between 5 min and 80 min.

9. The production method according to claim 1, wherein step (b) is implemented by at least one circulation of the polymerizable anchoring composition prepared at step (a) within the interior volume of the chromatography column.

10. The production method according to claim 1, wherein the polymerizable anchoring composition used at step (i) and the polymerizable monolith synthesis composition used at step (ii) comprise one same (meth)acrylate monomer.

11. The production method according to claim 1, Wherein the inner diameter of the chromatography column is smaller than or equal to mm.

12. The production method according to claim 1, wherein the functionalization step (2) is implemented by contacting the monolithic stationary phase prepared at step (1) with the at least one extractant in liquid from whereby impregnation of the monolithic stationary phase with the at least one extractant is obtained.

13. The production method according to claim 1, wherein the functionalization step (2) is performed by covalent grafting of the at least one extractant the monolithic stationary phase prepared at step (1).

14. A method for chromatographic separation of elements of an acid aqueous solution S, the method comprising: (A) performing at least one circulation of a mobile phase consisting of the acid aqueous solution S over a monolithic stationary phase of a chromatography column produced by implementing the method according to claim 1; and (B) performing at least one elution, with a mobile phase consisting of an eluting aqueous solution, of the monolithic stationary phase obtained after step (A), whereby some or all of the elements are recovered in the eluting aqueous solution.

15. The chromatographic separation method according to claim 14, wherein the aqueous solution S has a concentration of H.sup.+ ions lower than or equal to 10.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 corresponds to an image obtained with a scanning electron microscope (SEM) of the monolithic stationary phase prepared in accordance with the protocol described below.

(2) FIG. 2 gives the curves translating the changes in concentrations of europium, thorium and uranium found in the recovered eluates, respectively denoted [Eu], [Th] and [U] and expressed in ppm, as a function of the number of circulated dead volumes denoted Vm of eluting phases, after depositing the sample of aqueous solution S in the chromatography column conforming to the invention denoted Col.sub.inv..

DETAILED DESCRIPTION OF PARTICULAR EMBODIMENTS

(3) 1. Surface Modification of a COC Plate

(4) A polymerizable anchoring composition was prepared by mixing 160 mg of ethylene glycol dimethacrylate (EGDMA), 80 mg of 2,2-dimethoxy-2-phenylacetophenone (DMPA) and 850 mg of ethanol.

(5) The polymerizable anchoring composition thus prepared was deposited on a substrate formed by a plate in cyclic olefin copolymer, this COC being marketed under reference Topas® 6013 by Topas Advanced Polymers GmbH. This plate having a width of 21 cm, a length of 29.7 cm and a thickness of 381 μm, was previously rinsed with ethanol.

(6) The plate thus coated was placed in an oven under ultraviolet radiation (UV) at a wavelength of 365 nm for 20 min to obtain polymerization of the composition. FIG. 1 gives the image such as obtained with a scanning electron microscope (SEM) of this monolithic stationary phase thus prepared and then deposited, this image having been processed using ImageJ software. Surface modification of the substrate formed by the COC plate can be clearly seen, with the presence on this surface of nodules forming a monolithic stationary phase.

(7) 2. Preparation of Monolithic Stationary Phases within the Interior Volume of a COC Column

(8) 2.1. Monolithic Stationary Phase Prepared in Accordance with the Method of the Invention

(9) The polymerizable anchoring composition prepared in accordance with paragraph 1. above was injected at a flow rate of 1.2 mL/h and for 10 min, into a microchannel in COC, this microchannel having an outer diameter of 4 mm, a length of 25 mm and a depth of 360 μm.

(10) After the 10 min, the excess polymerizable anchoring composition was evacuated so as only to leave behind a film of polymerizable anchoring composition on the inner wall of the microchannel.

(11) Polymerization of this film of polymerizable anchoring composition was then carried out via photochemical route under UV radiation at a wavelength of 365 nm for 1 h. The microchannel thus obtained comprises a modified inner wall.

(12) A polymerizable monolith synthesis composition was then prepared comprising: 20 mass % allyl methacrylate (AMA), 20 mass % ethylene glycol dimethacrylate (EGDMA), 33 mass % 1-propanol, 24 mass % 1,4-butanediol, 2 mass % water, and 1 mass % 2,2-dimethoxy-2-phenylacetophenone (DMPA).

(13) This polymerizable monolith synthesis composition was injected into the microchannel having the modified inner wall.

(14) After polymerization of this polymerizable monolith synthesis composition under UV radiation at a wavelength of 365 nm for 10 min, a chromatography column was obtained denoted Col.sub.inv.

(15) 2.2. Monolithic Stationary Phase Prepared in Conformity with the Method Described in Publication [1]

(16) A polymerizable composition of the type described for preparing the second monolith described on page 1682, left column in publication [1], was prepared from a mixture comprising the following compounds in the volume percentages specified below: 30% glycidyl methacrylate (GMA), 10% ethylene glycol dimethacrylate (EGDMA), 35% 1-propanol, 20% 1,4-butanediol, and 5% water.

(17) To the mixture thus prepared, azobisisobutyronitrile (AIBN) was added as radical polymerization initiator in a mass proportion of 2.5% relative to the total mass of methacrylate monomers GMA and EGDMA.

(18) The polymerizable composition thus obtained was injected into the same microchannel in COC as the one described in paragraph 2.1. above.

(19) After polymerization of this polymerizable composition following a protocol similar to one described above for the coated COC plate (UV radiation at 365 nm wavelength for 30 min), a chromatography column was obtained denoted Col.sub.ref..

(20) 3. Chromatographic Separations

(21) The chromatography columns Col.sub.inv. and Col.sub.ref. were impregnated with tri-n-butyl phosphate (TBP).

(22) Impregnation of the monolithic stationary phases was obtained by circulating pure TBP in each of the columns Col.sub.inv. and Col.sub.ref. for 2 h at a flow rate of 0.3 mL/h (5 μL/min). The monolithic stationary phases impregnated with TBP were rinsed by circulating distilled water for 7 min at a flow rate of 1 mL/h (17 μL/min).

(23) In each of these columns Col.sub.inv. and Col.sub.ref., was introduced a sample formed of 72.8 μL of an aqueous solution S containing nitric acid at a concentration of 5 mol/L (5 M), and europium, thorium and uranium, in the following contents: [Eu]=2.5 ppm, [Th]=8.9 ppm, and [U]=10 ppm.

(24) After depositing the sample, the stationary phase of each of the columns was washed with a mobile phase formed by 5 mol/L nitric acid solution at a flow rate of between 0.15 and 0.2 mL/h.

(25) 3.1 Chromatographic Separation with Column Col.sub.Ref

(26) The eluate collected at the outlet of column Col.sub.ref. after the above-mentioned washing step, contained not only europium Eu, which is an element not having affinity for the stationary phase impregnated with TBP, but also thorium and uranium, which are two elements which should have been retained by the TBP-impregnated monolithic stationary phase.

(27) The presence of these two elements in the eluate translates the weak anchoring of the monolithic stationary phase on the wall of the microchannel, weak anchoring which allows leakage of the aqueous solution S, and hence of all the elements contained therein, along the inner wall of the microchannel.

(28) The separation of the three elements Eu, Th and U is of lesser quality or even becomes impossible.

(29) 3.2 Chromatographic Separation with Column Col.sub.inv.

(30) The eluate collected at the outlet of column Col.sub.inv. after the above-mentioned washing step contained europium Eu as sole eluted element, Eu not having affinity for the TBP-impregnated stationary phase.

(31) Elution of the element thorium Th was then obtained with a change in eluting phase which was replaced by an aqueous 4 mol/L nitric acid solution.

(32) Finally, elution of the uranium element was obtained by a further change in eluting phase which was replaced by an aqueous 1 mol/L nitric acid solution.

(33) The successive elutions and separations are illustrated in appended FIG. 2 in which the curves translate the changes in concentrations of europium [Eu], thorium [Th] and uranium [U] found in the successively collected eluates, as a function of the number of dead volumes denoted Vm of the different washing and eluting phases that had successively been circulated, it being specified that 1 Vm=11.14 μL.

(34) As shown in FIG. 2, the separation of the three elements Eu, Th and U is not only possible but also with high performance.

BIBLIOGRAPHY

(35) [1] Y. Ladner et al., Lab Chip, 2012, 12, pages 1680-1685 [2] FR 2 978 153 A1 [3] J. M. Burke et al., Biomicrofluidics, 2012, 6, 016506