GB2143442A

GB2143442A - Method of manufacturing pliable quartz capillary chromatographic columns

Info

Publication number: GB2143442A
Application number: GB08417997A
Authority: GB
Inventors: Ludek Vodicka; Jan Triska; Jiri Mostecky; Jiri Gotz; Milos Mayer; Gabriela Kuncova
Original assignee: Vysoka Skola Chemicko Technologicka V Praze
Current assignee: Vysoka Skola Chemicko Technologicka V Praze
Priority date: 1983-07-14
Filing date: 1984-07-16
Publication date: 1985-02-13
Also published as: DD244049A3; GB2143442B; DE3425924A1; CS530983A1; NL8402248A; FR2549228A1; FR2549228B3; GB8417997D0; CS240116B1

Abstract

A tube of quartz glass is drawn at temperatures of 1800 to 2100 DEG C to a capillary of accurate internal diameter using a contactless shadow measuring apparatus connected with a regulator of advance of the tube in an oven while maintaining an inert atmosphere within the tube and capillary, a coating of polyimide or polyesterimide lacquer is applied on the external surface, which lacquer is hardened at 250-350 DEG C and the stationary phase is then applied on the internal surface of the capillary. <IMAGE>

Description

SPECIFICATION Method of Manufacturing Pliable Quartz Capillary Chromatographic Columns and Arrangement for Execution of this Method The invention relates to a method of manufacturing pliable quartz capillary chromatographic columns with accurate internal diameter and to arrangement for execution of this method.

Glass capillary columns are more and more used for gas chromatography due to the high separation efficiency which can be achieved by their application, what is particularly important in case of separation of complicated mixtures of compound. One rather important feature for preparation of highly efficient columns is the achievement of an inert surface of the internal wall of the capillary, to which wall the stationary phase is applied. Active places on the surface of the capillary which are supposed to be the consequence of presence of silanol groups and of metal oxides in the glass, are causing due to increased adsorption of the analyzed materials a deformation of chromatographic zones, particularly if highly polar materials are analyzed, what makes difficult the evaluation of chromatograms and frequently distorts the results of the analysis.It is therefore necessary to perform at glass columns a rather time consuming desactivation of the internal surface prior to the proper filling by the stationary phase.

One of major drawbacks of glass columns is their reduced pliability causing their frequent rupture in the course of manipulation.

Due to the mentioned drawbacks of glass columns an increased attention has been recently paid to the development of quartz capillary columns. Quartz capillary columns described in the Journal for high resolution chromatographs and chromatography, Commun. 2 (1979) 2 and in the American Laboratory (1979) 61 have the advantage to be pliable and to contain only small amounts of metal oxides compared with glass capillary columns. They contain also smaller amounts of silanol groups than glass columns so that the deactivation of the internal surface by known methods is easier.

It is known that the desactivation of the internal surface of quartz capillaries is performed for instance by polyethylenoxide, dimethyldichlorsilan, trimethylchlorsilan and hexamethyldisalazan. It is also known to cover the external surface of quartz capillary columns by silicon rubber, polyimide, silicon nitride, by metal, possibly also by some of their mixtures.

It is also known to draw quartz capillary columns on a modified drawing device for glass capillaries (see H. D. Destry et al in Analytic Chemistry 32, 302, 1960) where the quartz tube is heated by an oxygen-hydrogen flame or by an oxygen-propane flame. The drawing of capillaries from a quartz tube heated by means of an electric resistance oven or of a high frequency induction oven is also known (Japan Kokai Tokkyo Koho Jp 82, 03, 723).

Drawbacks of known methods and arrangements are particularly in that it is not always possible to maintain an accurate internal diameter of the capillary in the course of drawing, that it is necessary to apply quartz tubes of high quality with a regular shape and that due to contact with air moisture, unwelcomed silanol groups can occur on the internal wall of the capillary.

Further drawbacks are both the presence of accompanying impurities (particularly metal oxides) on the internal wall of the capillary, which influence unfavourably the properties of the chromatographic column and also the difficulty of application of an external polymer layer of constant thickness. The application of the stationary phase on the internal surface of the capillary column is relatively complicated and time consuming (for instance in case of application of the so called static method, the anchoring of the stationary phase requires even several days).

It is an object of this invention to eliminate these drawbacks and to provide a method and an arrangement for manufacture quartz capillary chromatographic columns with accurate internal diameter. According to this invention the speed of feeding a tube heated to a temperature of 1800 to 2100 C, advantageously to 1850 to 1 9500C is controlled in dependence on readings of a contactless shadow measuring apparatus of the internal capillary diameter, whereafter a polyimide or polyesterimide lacquer is applied on the external capillary surface with a following hardening at temperatures of 280 to 3500C advantageously at 300 to 3200C and finally a coating of a stationary phase is applied on the internal capillary wall.

The surface of the quartz tube is prior to drawing to a capillary exposed to at least twice repeated repolishing in an oxygen-hydrogen flame, whereby at the first passage of the quartz tube the temperature of the oxygen-hydrogen flame amounts to 1800 to 19000C, advantageously 1850 to 1 8800C, the rotation speed of the tube is 40 to 60 rpm, advantageously 50 to 55 rpm and the advance speed of the burner with the oxygen-hydrogen flame is 30 to 50 mm per minute, advantageously 40 to 45 mm per minute and in the course of a further passage of the quartz tube at the same temperature and the same rotation speed, the advance speed of the burner amounts to 120 to 1 60 mm per minute, advantageously 140 to 160 mm per minute.Prior to the repolishing of the quartz tube a rinsing in hydrofluoric acid or in a solution of hydrofluoric and nitric acid is also accomplished for a time of 5 to 10 minutes with following rinsing in distilled water. According to a further feature a protective atmosphere is maintained within the tube and the drawn capillary in the course of drawing by introduction of dry gases such as oxygen, chlorine, helium, argon, advantageously argon. The harderning of the polyimide or polyesterimide lacquer is accomplished at subsequently increasing temperatures from 50 to 3500C at a speed of 1 to 1 00C per minute, advantageously 3 to 60C per minute.

According to a last feature, the application of the coating of the stationary phase on the internal surface is accomplished by winding on the capillary, with one end closed, filled with a solution of the stationary phase into a thermostat heated to a temperature from 1 50 to 2500C advantageously from 200 to 2200C.

The arrangement for execution of the method of manufacture of quartz capillary columns according to this invention comprises means for advance of the quartz tube, means for heating the tube, a shadow measuring apparatus of the internal capillary diameter, means for application of an internal polyimide or polyesterimide coating, a drying oven and a drawing device, the improvement consisting in that the means for application of the external polymer coating is accomplished by a soft nozzle of silicon rubber.

The arrangement for application of a layer of the stationary phase comprises a heated thermostat where a rotatable coil is situated, driven by an electric motor at constant rotating speed and beyond the thermostat another rotatable coil isosituated with the wound-on quartz capillary, from which coil the capillary is wound-off into the thermostat.

The effect of the method and arrangement according to this invention is particularly that by use of the contactless shadow measuring apparatus for measuring the internal diameter of the capillary connected with control means for advance of the quartz tube into the hot part of the oven, an accurate internal diameter of the capillary is obtained in the course of the whole drawing process with an accuracy of +4%.

By the method according to this invention the creation of silanol groups on the internal wall of the capillary is limited by maintenance of an inert atmosphere within the tube and capillary in the course of drawing. In order to suppress creation of active centers on the internal surface of the capillary, metal oxides and other residual impurities are removed by leaching with hydrofluoric or nitric acid or by their mixture.

Another advantage of the method according to this invention is the application of a uniform coating of polyimide or polyesterimide of an accurate constant thickness on the external surface of the capillary. An increased mechanical strength of quartz capillary columns is achieved by a method according to this invention consisting in that the worked quartz tube is prior to drawing of the capillary exposed to several repolishings in an oxygen-hydrogen flame and also in that the hardening of the external layer is accomplished at a gradually increasing temperature.

Another advantage of the method and arrangement according to this invention is a substantial reduction of time required for application of the stationary phase on the internal surface of the capillary and an improvement of the quality of chromatographic columns.

The method according to this invention will be in the following described in more detail on several exemplary embodiments and an arrangement for application of the stationary phase according to this invention shown in the attached drawing diagrammatically in elevation and side view.

Example 1 A tube of natural quartz having a content of impurities (in ppm): 2 Fe203, 5 TiO2, 10 AI2O3, 1 5 Na2O, 8 K2O, and 40 OH- of an external diameter of 9 mm, an internal diameter of 6 mm and with variations of the thickness of the tube of +8% has been fixed in a feeding device. The end of the tube situated in a chuck of the feeding device has been wrapped in an aluminium foil for intercepting radiated heat. In order to secure a uniform heating along the whole circumference, the tube has been carefully centered.The lower end of the tube has been thereafter situated 2 cm below the hot zone of a graphite resistance oven and the temperature of the hot zone has been increased to 21000C. At this temperature the end of the tube starts to drip and a capillary of a length of 3 m has been subsequently manually drawn. The temperature of the oven has been thereafter reduced to 1 9000C and the capillary drawn up to drawing rollers. The temperature of the oven has been thereafter increased to 21 000C and the capillary introduced between rotating drawing rollers and drawn at a speed of 6 m/min.The drawing speed and the feeding speed of the tube have been gradually increased at a simultaneous reduction of the temperature of the hot zone to 1 9000C until an internal diameter of 200 um has been obtained. The internal capillary diameter has been in the course of drawing measured by a shadow measuring apparatus and the internal capillary diameter has been by means of a regulator of the advance speed of the tube into the hot zone of the graphite oven maintained with an accuracy of +4%. A coating of polyesterimide lacquer has been applied on the drawn quartz capillary on the outlet from the graphite oven which has been dried by passage through a drying oven heated in its upper part to 4000C and in its lower part to 2500C. The hardening of the polyesterimide layer has been accomplished by heating the capillary in a thermostat at a temperature of 3300C for 3 hours. The thus prepared capillary has been filled by one third with a 10% solution of a stationary phase and the solution has been forced through the capillary by nitrogen at a pressure of 50 kPa.

After wetting the whole internal surface of the capillary column by the solution of the stationary phase, the surplus of the solvent has been removed from the column by a nitrogen stream and the column conditioned at 500C for one hour.

Example 2 A tube of synthetic quartz has been submerged for 10 minutes into a solution HF:HNO3:H2O of a ratio 1:1:1 and thereafter rinsed by distilled water, The tube hus been subsequently clamped in a feeding device and an opening of a diameter of 2 mm has been bored in the tube directly below the clamping place in the feeding mechanism. After adjustment of the tube exactly at the center of a hot zone of a circular burner, a capillary has been drawn in an oxygen-hydrogen flame, which capillary has been passed through a nozzle of silicon rubber of a diameter of 220 ym.

In order to facilitate the passage, 0,05 ml of dimethylpolysiloxan oil of a viscosity of 300 cP has been introduced into the nozzle prior to drawing. The capillary has been drawn while maintaining a constant drawing speed of 7 m/min and at a constant temperature of 1 9200C of the flame of the burner. A constant internal diameter of the capillary has been maintained by regulating the advance of the semiproduct into the hot zone using a contactless measuring apparatus of the internal capillary diameter. An inert atmosphere has been maintained in the tube and in the drawn capillary by means of argon in the course of drawing, the argon being supplied into the tube at a speed of 8 ml/min. The solvents from the polyimide coating have been evaporated by passage of the capillary through two drying ovens.The first has been 25 cm long, heated to 400"C, the second 50 cm long, heated in the upper part to 3000C, in the lower part to 3500C.

The thickness of the polyimide layer has been 1 5 Mm. The hardening of the lacquer has been accomplished in a thermostat, where the temperature has been gradually increased at a speed of 20C/min from a laboratory temperature up to 1 400C. At this temperature the column has been maintained for 30 minutes, whereafter it has been heated at a speed of 40C/min up to a temperature of 3000C and maintained at this temperature for 30 minutes.

The attached drawing shows in elevation and in side view diagrammatically a thermostat 1 where a coil 2 for winding-on of the capillary 5 is rotatably arranged, with another coil 4 on top of the thermostat 1. The coil 2 is driven by an electric motor 3.

Claims

1. Method of manufacture of pliable quartz capillary chromatographic columns with an accurate internal diameter by drawing from a quartz tube while controlling the speed of feeding of the tube, heated to a temperature of 1800 to 21000C, advantageously to a temperature of 1 850 to 1 9500C in dependence on readings of a contactless shadow measuring apparatus of the internal diameter of the capillary, whereafter a polyimide or polyesterimide lacquer is applied on the external surface of the capillary with a following hardening at a temperature of 250 to 3500C,advantageously 300 to 3200C and finally a coating of a stationary phase is applied on the internal surface of the capillary.

2. Method as in claim 1, the surface of the quartz tube being exposed prior to drawing to at least two repolishing operations in an oxygenhydrogen flame, whereby at the first passage of the quartz tube the temperature of the oxygenhydrogen flame is maintained at 1800 to 1 9000C, advantageously at 1850 to 1 8800C, the rotating speed at 40 to 60 rpm, advantageously at 50 to 55 rpm and the advance speed of the burner with the oxygen-hydrogen flame at 30 to 50 mm/min, advantageously at 40 to 45 mm/min and at a further passage of the quartz tube at the same temperature and rotation speed, the advanced speed of the burner is maintained at the value of 120 to 160 mm/min, advantageously at 140to 160mm/min.

3. Method as in claim 1 or 2, where prior to the repolishing of the quartz tube a rinsing in hydrofluoric acid or in a mixture of hydrofluoric and nitric acid to 5 to 10 minutes is accomplished, with a following rinsing in distilled water.

4. Method as in claim 1,2 or 3, where in the course of drawing the capillary a protective atmosphere is maintained within the tube and the drawn capillary by passage of dry gases such as oxygen, chlorine, helium or argon, advantageously by argon.

5. Method as in one of claims 1 to 4, where the hardening of the polyimide or polyesterimide lacquer is accomplished at gradually increasing temperatures from 50 to 3500C at a speed of 1 to 1 00C per minute, advantageously 3 to 60C per minute.

6. Method as in one of claims 1 to 5, where the application of a stationary phase on the internal surface of the capillary is accomplished by winding-on the capillary, sealed on one end and filled with a solution of a stationary phase into a thermostat heated to a temperature of 1 50 to 2500C advantageously 200 to 2200C.

7. Arrangement for execution of the method as in claim 1 comprising means for advance of a quartz tube, means for heating the tube, a shadow measuring apparatus of the internal diameter of the capillary, means for application of an external polyimide or polyesterimide coating, a drying oven and a drawing device, the means for application of an external polymer coating being a soft nozzle of silicon rubber.

8. Arrangement for execution of the method as in claim 6, comprising a thermostat with a rotatable coil driven by an electric motor at constant rotating speed inside the thermostat and with another rotatable coil for winding-on the quartz capillary outside the thermostat.

9. Method of manufacture of pliabile quartz capillary chromatographic columns substantially as hereinbefore described with reference to the foregoing Examples 1 or 2.

1 0. Apparatus for the manufacture of pliable quartz capillary chromatographic columns substantially as hereinbefore described with reference to the accompanying drawings.