GB2189597A - Helical-flow analytical module - Google Patents

Abstract

A helical-flow analytical module has a chemical resistant plastic cylinder 1 with a helical V-shaped channel 2 with internal striations sealed by a sleeve of heat-shrink plastic 3 for spectrophotometric reactions. Reagents are introduced into the module through inlet ports 21. Samples are introduced either by a manual two-way valve which measures a constant volume, or a sample diffuser which has no moving parts and is used with timer-based automatic samplers. Both means of introducing samples are directly attached to the top of the plastic cylinder and so form an integral part 20 thereof. Battery or mains operated spectrophotometers and peristaltic pumps may be used so that analyses may be carried out in the laboratory and in a portable field system. <IMAGE>

Description

SPECIFICATION Helical-flow analytical module GENERAL DESCRIPTION The helical-flow analytical module is a miniaturized flow system for colour development (spectrophotometric) reactions. The module provides a matrix for the introduction of reagents and for the subsequent colour development that occurs. Therefore, the helical-flow module provides an alternative to the tubing and coils of conventional automatic flow systems. The module is simple to set up and gives rapid reproducible results at a fraction of the cost of the conventional coils. The sample requirement is smaller compared to conventional systems, which is of importance there sample availability is restricted. Therefore, the amount of reagents required is reduced so that running costs are also lowered.

The module can perform all types of colour development analysis by simply changing reagents, or several modules can be used simulstaneously for a multi-reaction apparatus.

The helical-flow analytical module can be used in a semi-permanent apparatus set up for daily analysis, or connected temporarily to a spectrophotometer for occasional analyses after which it can be packed away to save bench space. As the module is small and compact it can be connected to, or disconnected easily from, other equipment within minutes. The size and flexibility of the module can enable its use with portable battery operated equipment in field situations. Therefore, it is possible to carry out accurate quantitative analyses immediately samples have been taken. This could have important implications in agriculture and horticulture for predicting the fertilizer requirements of field grown crops. A portable analytical system may also be of use to the Water Authorities and brewing industry.

The helical-flow module would be ideal for used in Third World. It can be envisaged that the helicai-fow module would be of use to experimenters in biological sciences e.g.

botany, ecology, soil science, agriculture, horticulture, food science etc. Schools and colleges would benefit from the module for teaching quantitiative chemistry, environmental studies etc. Hospitals and other institutes with analytical facilities could use the helical-flow modules for daily routine, or occasional analyses for a fraction of the cost of present conventional systems.

CONSTRUCTION AND MODE OF OPERATION The helical-flow analytical module comprises a cylinder of chemically resistant plastic 1 (25 to 50mm diameter) eg. perspex, nylon, PVC or PTFE with a narrow V-shaped channel 2 (approximateiy 1 mum deep) running around the circumference like a screw thread with internal striations to assist reagent mixing. The channel is sealed with a sleeve of heat-shrink plastic 3. The sample introduction system 4 is attached to the top of the module thus forming an integral part thereof. However, in the simplest version no sample introduction system is included.

The helical channel may be separated into a series of segments as shown in Fig. 1, or may a continuous helix, or may be longitudinal running the length of the plastic cylinder and doubling back around the circumference as illustrated in Fig. 2. Before and after each helical segment a circular groove 5 allows the secure fitting of the heat-shrink plastic sleeve.

The segmented channel format allows the attachment of an external reaction column 6.

For example, the column may contain zinc for the analysis of nitrate, where nitrate is reduced to nitrite before coupling with naphthylethylenediamine dihydrochloride which forms a coloured azo-dye. Extended channel path lengths can be obtained by connecting several segments in series. This is achieved by connecting an external reactor column or tubing between outlets 19 and inlets 20. The reagent flow is connected to a spectrophotometer through outlet 19 of the last segment of the previous connected or single segments. Reagents are introduced into the channel by inlets 21 which enter the channel directly. Several such inlets may be provided that can be plugged when not in use. Inlet and outlet ports to the module may be of a diameter smaller than of the tubes which carry the reagents to the module so that they may be push-fitted into the ports.Alternatively, more sophisticated screw-in fittings and ferrules of nylon, PTFE or stainless steel may be employed to attach tubing to the module.

Figs. 3, 4 and 5 illustrate a two-way sample valve that forms an integral part of the helicalflow module. The body 7 of the valve is constructed from chemically resistant plastic and has a similar diameter to that of the plastic cylinder. The valve is rotated on the top of the plastic cylinder over a PTFE backed silicone rubber seal 8 with four ducts. The combined use of both these materials in the seal has the advantage that the critical tolerances required to produce a leak-free valve are broadened. In Figs. 3 and 4 the valve is shown in the open position. Reagent is introduced through inlet 9, through duct 10 in the seal, across the valve by means of an internal channel 14 (Fig. 3), back through the seal by duct 11 and into the beginning of the helical channel 15.In this position sample solution is injected into a sample loop 16 through inlet 17, duct 12 and exits to waste through duct 13 by outlet 18. The sample loop may be changed to increase or decrease the sample volume introduced. The valve is manually turned to the closed position, illustrated in Fig.

5, and a reproducible volume of sample is introduced into the helical channel as the sam ple loop 16 is placed in the direct reagent flow between ducts 10 and 11. The valve position can be located by a pin and groove system (not shown). The module and rotating body of the valve are secured together by means of a corrosion resistant spring 22 loaded metal bolt 23, wing nut 24 and nylon bush 25 as illustrated in Fig. 6.

Fig. 7 illustrates an internal two-way sample valve as an integral component of a segmented helical-flow module. The body of the valve 7 is constructed from PTFE. The uppermost part is cylindrical and the lower part is conical. The body is inserted into the top of the module in a recess 27 of similar dimension and is secured in place with a screwed cap 28 and a silicone rubber 29 and PTFE 30 seal. The valve is located and positioned in the module by a lever 31 which is screwed into the valve body 32 through a locating hole 33. The position of the lever when the valve is open (A) or closed (B) is illustrated in Fig.

8. In the open position A, shown in Fig. 9, reagent is introduced by inlet 9 and flows through duct 34 of the valve into duct 35 of the module and enters the helical channel 15.

In this position the sample solution is injected into the sample duct 36 of the valve through inlet 17 and exits to waste by outlet 18. Fig.

10 illustrates different sample duct configurations that may be used to increase or decrease the sample volume introduced. The valve is manually rotated to the closed position B, illustrated in Fig. 11, and a reproducible volume of sample is introduced into the helical channel as the sample duct 36 is placed in the direct reagent flow between inlet 18 and duct 35. Other reagents are introduced into the channel by inlets 21 that enter the channel directly from the top of the module.

Fig. 12 illustrates the new sample diffuser.

The sample diffuser is designed for use with conventional timer-based automatic sampler units. There are no moving components employed in this system of introducing a sample into the helical channel. The body of the diffuser 37 is constructed from chemically resistant plastic, which is preferably transparent eg perspex, and has a similar diameter to that of the plastic cylinder. The body of the diffuser is separated from the plastic cylinder with a glass fibre membrane 38, eg. GF/A grade Whatman filter. When this sample introduction system is employed the reagent flow is drawn through an outlet 19 under suction with a flow rating just greater than the total flow entering the module. The sample, with air bubbles, is pumped into an incomplete circular channel 39 through inlet 40.The sample diffuses through the glass fibre membrane into a similar incompiete circular channel 41 on the top of the plastic cylinder, beneath the membrane. The bubbles pass over the top of the membrane and exit through outlet 42. Pressure is equalized as reagent is drawn into the channel 41 under suction through inlet 43.

Therefore, bubbles are eliminated and the sample and reagent enter the helical channel through inlet 15. This process also filters particulate matter from the sample solutions. The body of the diffuser 37 is secured to the plastic cylinder with a corrosion resistant screw 44, threaded directly into the top of the p[astic cylinder.

Fig. 13 illustrates a multiple component series of helical-flow modules with an external cone valve of the type illustrated in Figs. 9, 10 and 11. In the open position reagent is introduced through the valve at inlet 9, by duct 34 and enters the module by connecting tube 45. Sample solution is injected into the sample duct 36 through inlet 17 and exists to waste by outlet 18. The valve is manually rotated to the closed position and the sample is introduced into the helical channel as the sample duct 36 is placed in the direct reagent flow between inlet 9 and connecting tube 45.

The valve body is secured by a screw thread 46 and nut 47, with a silicone rubber 29 and PTFE 30 washer. Other reagents are introduced into the helical channel by inlets 21 that enter the channel directly. Several such inlets may be provided for each module and these can be plugged when not in use. The reagent outflow through outlet 19 may be connected directly to a spectrophotometer for a single module reaction system, or may be attached to one or more modules in series. The modules may be connected by tubing or a reaction column 6.

Fig. 14 illustrates an oil heating jacket. Certain colour development reactions require a high temperature for the reaction to proceed.

The heating jacket is constructed from alloy metal 48 with a recess 49 which is filled with silicone oil. Reagent flow from the module is connected to a length of tubing 50 emersed in the oil, before entering the spectrophotometer. However, if high temperatures are required for colour development the reagent flow temperature may require stabilization before entry into the spectrophotometer. A simple reagent flow cooler-stabilizer is illustrated in Fig. 15. The cooler-stabilizer is constructed from alloy metal and has an internal conduit 51. Mains water supply is connected to one end of the conduit and thus lowers the temperature of the alloy metal. Reagent flow from the heater is connected to tubing 52 which is wound tightly around the cooler-stabilizer to allow good heat transfer, before the flow enters the spectrophotometer.

Claims (1)

1. A helical-flow analytical module comprising a cylinder of chemically resistant plastic, a helical V-shaped channel with internal striations sealed by heat-shrink sleeving, means for introducing reagents into the channel, means for introducing a sample into the channel by a manually operated integral two-way valve or a sample diffuser, means of attaching external reaction column facilities and exitting the reagent flow to a spectrophotometer.

2. A helical-flow analytical module as claimed in Claim 1, constructed from chemically resistant plastic, for example, perspex, nylon PVC or PTFE.

3. A helical-flow analytical module as claimed in Claim 1 or Claim 2, wherein the channel may be separated into a series of segments, or may be a continuous helix, or may be longitudinal running the length of the plastic cylinder doubling back around the circumference.

4. A helical-flow analytical module as claimed in Claim 2 or Claim 3,-wherein an external reaction column may be attached.

5. A helical-flow analytical module as claimed any preceding Claim, wherein reagents are introduced into the channel through pushfit connections or chemically resistant screw-in tube fittings and ferrules.

A helical-flow analytical module as claimed in any preceding Claim, wherein sample solutions may be introduced by an integral or unattached manual two-way valve whereby a reproducible volume of sample is measured by a sample loop, the volume of which may be increased or decreased, while reagent passes through in the first position and second position in which the sample is introduced into the reagent flow.

7. A helical-flow analytical module as claimed in Claim 6, wherein the valve body is rotated over a PTFE backed silicone rubber seal or any other chemically inert materials with similar coefficients of friction.

8. A helical-flow analytical module as claimed in Claim 5 or Claim 6, wherein the sample volume is measured by means of tubing.

9. A helical-flow analytical module as claimed in Claim 5 or Claim 6, wherein the sample volume is measured by means of a cone constructed from PTFE, or any other chemically inert material with a similar coefficient of friction.

10. A helical-flow analytical module as claimed in any preceding Claim, wherein sample may be introduced by a directly attached sample diffuser whereby an amount of sample is automatically introduced from a timer-based automatic sampler, where the air bubbles are filtered off over a glass fibre membrane that also acts as a sample filter and the sample diffuses through the membrane into a reagent stream fed by suction beneath the membrane.

11. A helical-flow analytical module as claimed in any preceding Claim, wherein reagent outflow may be passed through tubing in an oil jacketed heater and then a temperature cooler-stabilizer before entering the spectrophotometer.

12. A helical-flow analytical module as claimed in any preceding Claim, wherein the pressure for feeding the reagents is produced by a mains or battery operated peristaltic pump or any other fliud-flow system.

13. A helical-flow analytical module as claimed in any preceding Claim, wherein the colorimetric determination is carried out with a mains or battery operated spectrophotometer.

14. A helical-flow analytical module as claimed in Claim 12 or Claim 13, wherein spectrophotometric analysis is carried out in any laboratory or portable system.

15. A helical-flow analytical module substantially as described herein with reference to Figs. 1-15 of the accompanying drawing.

Amendments to the claims have been filed, and have the following effect: Claims 1 and 13 above have been deleted or textually amended.

New or textually amended claims have been filed as follows: CLAIMS

1. A helical-flow analytical module comprising a cylinder of chemically resistant material, a helical channel sealed by tight fitting nonreactive material or heat-shrink plastic sleeving, means for introducing reagents into the channel, means for introducing a sample into the channel by a manually operated integral two-way valve or a sample diffuser, means of attaching external reaction column facilities and exitting the reagent flow to a spectrophotometer.