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                        Make a µ-PLC Instrument

Here are adresses, necessary tools, materials, HINTS and tricks how to make your own µ-PLC “instrument”.
 
For economical reasons there will be no company (in 2009) which would produce and sell complete systems or at least the most critical part:
the mobile phase micro bottle “system”. 
This chapter here will be replaced by a GREEN CLICKWORD
if the author is wrong with his forecast of NO commercial availability.

BUT
it is really very easy to make it yourself.
This way the author and colleagues made all their first own
GC detectors, integrators,
GC-, µ-GC-, GCGC-, LC-, HPLC-, µ-HPLC-, HPPLC- instruments....
This was NOT so easy as compared with the make of
µ-PLC “instruments”.

Micro bottles:
As long as there is no producer for a > PTFE-plus-tube screw cup < available, the following pharmacy micro bottles are irreplaceable: Volume 1.5 ml, upper glass inlet diameter inside = 5.25 mm, brown quality glass, quite flexible black plastic screw cup, order number 467 in packages of 32, available at
www.holle-webshop.de
NOTE: by now holle-webshop has not the proper plastic screw cup available. We try to solve the problem. A way out is a PTFE tube-plus-tightener insert fed through a 5.01 mm hole in the screw cup cover. This makes the micro boittle tight and holds the phase transfer wick in stable position but there is a solution to this problem - see under “PTFE-insert-and-tube-part” below in this chapter.

For filling and phase mixing :
The Hamilton Syringe no. 1750, gas tight, worked good in our hands.

PTFE Tube:
For the mobile phase micro bottle system you need a precision PTFE tube which fits optimal in the cover glass hole. Therefore the outer diameter of 5.0 mm accuracy must be guaranteed. This worked with company Reichelt Chemietechnik GmbH+Co Heidelberg, Gerrmany. You may need 1 to 3 meter tube of 5.0 mm o.d., 3 mm i.d.. Click on Reichelt .

Phase transfer wick:
Best long time behavior under all tested mobile phases is given with viscose felt fabric. A soft, white 100 % viscose felt fabric which is not in easy reach at fabric shops. Therefore here is a photo which may help to get this best material for an optimally functioning wick. 

ms-cottonfabric

figure 1:
viscose felt fabric, this figure corresponds to a 20 x 20 mm piece. This material is about 2 mm thick.
We cut it in a size of 8 x 18 mm = 20 mg weight - see figure 2 - and roll it between dry clean fingers quite strong to a wick with a thickness of short below 3 mm o.d.. This fits into the 16 mm long 5.0 mm o.d., 3 mm i.d. PTFE tube by rotating the wick wire into the tube. It is necessary to smooth the tube edges inside and outside. using fine sandpaper for the outside smoothing and the 10 mm glass drill for the inside edge smoothing. The raw wick will look for 2..3 mm out off the 16 mm long PTFE tube. With a sharp nail scissors the over length part is cutted off remaining about 0.5 to 1 mm wick outside the tube. With fine sandpaper we smooth the wick end surface with fine sandpaper uniform enough. It will touch the HPTLC layer surface uniformly flat. viscose hairs looking out of the 3 mm tube diameter are also cutted off.

Finer details you may see on figure 2 below. Here all critical parts for the µ-PLC hardware are collected including the special drills: the 5.0 mm and the 10 mm o.d. glass drills with four cutting edges numbered a) and g). A 10 mm wood drill = b). A combination of a 16 mm x 5.0 mm o.d. / 3 mm i.d. PTFE tube piece with a 16.5 mm long 3.0 mm o.d. / 1.5 or 0.5 mm i.d. PTFE tube which sits inside the
5 mm tube = d). A 24 mm long x 10 mm o.d. aluminium rod with at least one end well machined for good contact by an UV adhesive as handle on the cover glass plate = f). Figure parts c)- f) and the black plastic screw cup plus the glass drill g) show parts, tools and a production order for the micro glass tube screw connection: first drill a 4.5 mm hole with a wood drill of 4.5 mm size. The drilling starts from the screw cup inside. Then widen the hole in the plastic with the 5.0 mm glass drill from the other side towards the inside screw. But only as deep as a finally strong tight connection of the 16 mm 5.0 o.d. PTFE tube part e) is possible. Move the PTFE tube against quite strong resistance into the conical hole in the plastic cup.
The cup drilling is not too simple, it needs a good stable mounting plate.
A 10 mm i.d. hole in a piece of wooden board acts as a mounting plate. A drill press with fine adjustable height and fine movement is needed. This is the only larger technical equipment you need for all mechanical jobs to be done. The tool is shown in figure 3 and 4 below. It even can be used when drilling extra holes into the cover glass plate, but there is a glass company which does the cover glass plate plus all holes for you, as glass drilling through a 5 mm thick cover glass plate needs some training, big patience and a good natural oil (droplets do it) - see next instruction below. The glass company even has the proper UV adhesive or knows the source. Problem: you need a droplet, but the adhesive producer has only large portions available. Part h) in figure 2 shows again a part of the viscose felt fabric used for the wick with a part showing the thickness of the material which looks like felt but is made of 100% viscose felt. Part i) is what we finally need for µ-PLC and mass volume sampling for trace analysis of extracts. To keep the wick in perpendicular position when it touches the TLC layer a short angle of a 0.2 mm thin steel wire is jammed in the PTFE tube end to hold the wick in position.

ms fig-2
msonlymachine-2
msonlymachine1

Figure 2

Figure 3 and 4
METABO tool; drill machine holder

µ-PLC Glass Cover Plate:
It is about 5 mm thick, size 100 x 100 with smoothed edges. It holds the mobile phase micro bottle upside down with the viscose felt wick touching the HPTLC layer surface. It builds a virtual TLC chamber but with vapor phase only. It holds the flush gas tube to dry off mobile phases, sample solvents, focus liquids and the mobile phases used after the separation. The 5 mm o.d. PTFE tube filled with the wick must move gently up and down but still keeps the phase bottle exactly enough perpendicular. Thus there is a precision hole necessary in the glass plate center. The center hole must have an i.d. of 5 mm i.d. with a tolerance of plus 0.05 mm. By ordering a 5 mm i.d. hole exactly in the plate center the final hole dimension has the necessary plus tolerance. The best address to order the cover plate with correctly positioned and dimensioned holes is THIS one because they have already enough cover plates produced. Contact Mr. Hofmann.
Up to now the author has fixed himself the four 1 mm thick 5 x 5 mm glass squares onto the corners. See as an example figure 2 click HERE .
I used CAMAG exchange glass parts from their flat HPTLC chamber and cutted the 5 x 5 mm square parts. The UV adhesive reacts under a CAMAG UV lamp directly within 10 minutes.
 

Working Board:
A 400 x 300 x 18 mm wooden book shelf board with a solvent stable hard surface does it. A good furniture shop cuts the board into the needed length and width. Now we need holes for the three aluminium rods for an exact positioning of the HPTLC plate and the cover glass plate. The holes can be made by the 10 mm wood drill in the positions xa = 100 mm, ya = 100 mm, xb = 120 mm,
xc = 180 mm, yb = 80 mm, yc = 80 mm. Start the measure for x and y positions from the left side lower edge of the wooden board and drill about 15 mm deep with the 10 mm wood drill - part b) in figure 2 above. Necessary is an exact horizontal position of the working board. A qualified spirit level tool will help to position correctly. It is visible in several photos in the chapter “Micro PLC”.

Gas Pump:
We use the system “Air Pump model A 120” which pumps 2 L air from around - or pumps carbon dioxid in a deep enough plastic tub at maximum 0.24 bar, 2.5 watt, article no. 86300. We got it HERE . The flush gas flow is also used when checking the flow resistance of the mobile phase wick and when drying this wick after each use. Figure 7 in the Micro PLC section shows the used interface to have a flush gas flow through a used wick. The connection to the cover glass plate is made by the soft clean plastic tube 6 mm o.d. with a short 16 mm PTFE tube 5.0 mm o.d. so, that this piece stands 0.5 mm above the HPTLC layer surface. A narrow rubber band of the soft plastic connection tube about 5.5 mm away from the PTFE tube end holds the position when the flush gas comes in contact with the virtual TLC chamber. The flush gas tube can sit constantly on a second cover glass plate which allows to exchange cover glass plates instead of the mobile phase bottle with the flush gas tube.

UV-Lamp:
We use the UV lamp CAMAG catalogue no. 022.9120, series 1401, 12 VDC / VAC 50/60 Hz and use a holder which is light tight by black cloth - see figure 6 in chapter micro PLC. The top board uf this Photo chamber has a maximum possible opening for the UV filter glass and takes care for the best uniform UV light transmission to the plate. The cover glass plate must be removed prior to the photo shut when under UV- see the figures in this SITE.

Micro Brushes:
We use brushes of the size no. 00, 1, 3, 5, 7. A qualified type is available as “da Vinci Harbin Kolinsky series 12526Y or Milan 310 055. Careful: these are soft brushes made of animal hairs.

Digital Camera:
The problem is, that a few days after you left a camera shop after your decision which model to take there is a next model available, much better and more clever for daily family photos. What µ-PLC needs is an optical resolution of more than 7 MPixel , top in focus from 50 cm to 5 cm distance to the plate surface, programmable in quite some technical details including slight out-of-focus positions. To this not so easily available special characteristic information in a later issue of this book. We need a camera MODEL WITH high light sensitivity, optimal position flash light source and well selectable other light source programs. A 1-4, better 10 GBite SDHC data storage capacity is advisable. In the minute we have payable IR and UV digital cameras the author will publish this break through in green. Already 20 years earlier we showed that circular multi sample PLC could be quantitized by UV sensitive photography including plate structure removal. Despite the fact that the co authors
M. Prosek, A. Medja and R. E. Kaiser made in the presence of technical witnesses a video report about this technical quantum jump in PLC quantitation we have been told that this does not work in practice for theoretical reasons.
Back to most economical digital quality cameras today: Good data we got from a Sanyo Model VPC EGE X Xasti; or NIKON Coolpix S 600 (10 MPixel). But the number of µ-PLC qualified digital cameras is still growing and the lifetime of a selected camera model still short. The final photo data must be adapted to the multi integration software. Reduction from a size of 2 to 3 MB into a picture of 60 to 100 KB and 640 x 480 pixel standard resolution with 72 pixel per inch is a question of seconds using the proper graphics software.
A latest personal / technical digital camera is the RICOH R10 digital system. 28-200 mm wide zoom (based on a 35 mm equiv.) and an 7.1 X optical zoom lets optimize the light for the PLC plate. 10 MPixel and a very wide range of specific equipment programming allowed immediately good photos for 100 x 100 mm plates. The camera allows sharp pictures down to 10 mm distance of the optics from the plate. To get fully uniform light onto the complete layer a larger distance is to be optimized, The camera programming is easy. See www.ricoh.com . The lifetime is forcasted for 6 months.

Graphics Software:
All needed adaptation is possible with Photo Impact XL ( www.ulead.com ) but there are many other well designed photo software packages available. Most of them however have for multi integration many never usable further sub programs on board.

Multi Integration software:
There is only one package available. It is optimized for µ-PLC analyses in the young development age. It can do too much in case we ask for. All data shown in this book and other info sources about µ-PLC quantitation have been done with the MI-software version 2.0.
As no software is ever finished there might soon be a version 2.1 available. Click on MI-SOFTWARE and go first to NEWS in the www.SORBFIL.com site.

PTFE-insert-and-tube-part:
In case there are no thick walled and chemically inert - solvent stable and plasticizer free screws for the micro bottle available, any plastic screw with the proper dimensions for the bottle can be used. They get a 5.1 mm hole drilled exactly in the center. From enough hard and clean PTFE the insert-and-tube part according to the figure below is machined. This part offers an inert, solvent resistant and plasticizer free connection to the HPTLC plate. The tube is packed with viscose felt fabric. This offers a perfect wick. The round part with a diameter of 8.5 mm acts as a flat O ring seal. Therefore it should be as thin as possible for complete tightness. For water samples the felt measure should be 6x20 mm and softly turned into the PTFE-5.0 mm tube. The lower end of the wick should stay a littel bit outside the 5.0 outside 3 mm inside tube. Cleaning by the gas flow only from the tube side.

 

ptfe-part

Figure PTFE-insert-and-tube-part
The figure is not top on scale but the measures given are correct. The 5.0 mm outside measure of the thick walled PTFE wick holding tube part needs outside precision, tolerance smaller than 0.02 mm. One measure is missing in this drwaing . see the figure below.

FE-part-1
resisttester

Figure Permeability measurement of the phase- transfer wick.
The as thick line drawn tube is the one which normally connects the air flow from the gas pump into the center hole of the cover glass plate.

Meanwhile by 2009 the producer of the micro bottle changed the srew-type cap. Now the material is too thin for a solid insertion of the 5.0 mm o.d., 3 mm i.d. PTFE tube, which holds the wick. Therefore it was necessary to alter the construction of the mobile phase feeding part of the µ-PLC instrument. The now available cap gets a 5 mm hole drilled accurately in its round center - see the srew right hand in the photo left. The PTFE-insert-and-tube-part is inserted. By strong enough screwing onto the glass thread the bottle is closed perfectly - so no loss of mobile phase nor a false air connection into the liquid. This tool keeps the whole mobile phase volume top clean inside a glass / PTFE wall.

Dr. F. Eisenbeiss had the necessary small turning lathe with which he could produce the
PTFE-insert-and-tube-part shown as technical drawing in the figure above. Already the very first piece worked fine. One measure in the drawing above is missing. It turned out, that the tightening part is flexible enough with a thickness of between 1.0 and 1.5 mm.
Thank you, Friedhelm.

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