Metrohm 797VA User Manual
797 VA Computrace
Hardware Manual
8.797.8001EN
Metrohm AG
CH-9101 Herisau
Switzerland
Phone +41 71 353 85 85
Fax +41 71 353 89 01
info@metrohm.com
www.metrohm.com
797 VA Computrace
Hardware Manual
8.797.8001EN 08.2009 zst
Teachware
Metrohm AG
CH-9101 Herisau
teachware@metrohm.com
This documentation is protected by copyright. All rights reserved.
Although all the information given in this documentation has been
checked with great care, errors cannot be entirely excluded. Should you
notice any mistakes please send us your comments using the address
given above.
Documentation in additional languages can be found on
http://products.metrohm.com under Literature/Technical documenta-
tion.
Inhaltsverzeichnis
Table of contents
1 Introduction ..........................................................1
1.1 Instrument description.................................................................. 1
1.2 Parts and controls......................................................................... 2
1.3 Information about the Instructions for Use................................... 7
1.3.1 Organization............................................................................ 7
1.3.2 Notation and pictograms......................................................... 8
1.4 Support documentation................................................................ 9
1.4.1 Application-Bulletins................................................................ 9
1.4.2 Application Notes .................................................................. 10
1.4.3 Monographs.......................................................................... 11
1.4.4 Reprints................................................................................. 11
2 Installation..........................................................12
2.1 Setting up the instrument ........................................................... 12
2.1.1 Packaging.............................................................................. 12
2.1.2 Check .................................................................................... 12
2.1.3 Location ................................................................................ 12
2.2 Installation of the 797 VA Computrace Stand............................. 12
2.2.1 Mains cable and mains connection ........................................ 12
2.2.2 Switching the instrument on/off ............................................ 13
2.2.3 Connection to the PC............................................................. 13
2.2.4 Equipping the measuring head .............................................. 14
2.2.5 Inert gas connection.............................................................. 17
2.3 Multi-Mode Electrode (MME)...................................................... 20
2.3.1 Construction and operating characteristics of the MME......... 20
2.3.2 Filling the MME with mercury................................................ 22
2.3.3 Mounting the capillary........................................................... 23
2.3.4 Filling capillary without vacuum............................................. 23
2.3.5 Filling the capillary using vacuum .......................................... 25
2.3.6 Storing the MME ................................................................... 29
2.3.7 Replenishing the mercury (without changing capillary) .......... 29
2.3.8 Changing capillary ................................................................. 29
2.3.9 Cleaning the MME................................................................. 31
2.4 Rotating disk electrode (RDE) ..................................................... 34
2.4.1 Construction and startup of the RDE...................................... 34
2.4.2 Regeneration of RDE ............................................................. 34
2.5 Reference electrode .................................................................... 36
2.5.1 Construction.......................................................................... 36
2.5.2 Startup procedure.................................................................. 37
2.6 Auxiliary electrode ...................................................................... 38
2.6.1 Construction.......................................................................... 38
2.6.2 Startup procedure.................................................................. 38
2.7 Stirrer ......................................................................................... 39
2.8 Connection of Dosing devices..................................................... 40
2.8.1 Electrical Connection ............................................................. 40
2.8.2 Tubing connection................................................................. 40
2.8.3 Change Dosing-/Exchange unit .............................................. 44
2.9 Connection of 863 Compact Autosampler .................................. 46
2.9.1 Electrical connection.............................................................. 47
2.9.2 Tubing connections ............................................................... 48
2.9.3 Software settings................................................................... 51
2.9.4 Operation of the 863 Compact Autosampler ......................... 52
2.10 Connection of 838 Advanced Sample Processor ......................... 53
797 VA Computrace / Hardware-Manual 8.797.8001EN
I
Inhaltsverzeichnis
2.10.1 General composition.............................................................. 55
2.10.2 System description for a combined system for Brightener and
Suppressor.............................................................................
2.10.3 System description for Suppressor determination .................. 59
2.10.4 System description for Brightener determination with MLAT. 61
2.10.5 System description for Brightener determination with LAT .... 65
56
2.11 Control lines................................................................................ 67
2.12 Connection of peripherals ........................................................... 67
2.13 Communication diagrams for automation .................................. 68
2.13.1 Communication diagram VA.................................................. 69
2.13.2 Communication diagram LAT................................................. 70
2.13.3 Communication diagram MLAT ............................................. 71
2.13.4 Communication diagram DT .................................................. 72
2.13.5 Communication diagram "RC Record response curve" ........... 73
2.13.6 Communication diagram "RC Sample with response curve"... 74
3 Safety ................................................................. 75
3.1 Electrical safety ...........................................................................75
3.2 Change fuses .............................................................................. 76
3.3 Cabinet temperature ................................................................... 76
3.4 Safety considerations concerning mercury ..................................77
3.4.1 Properties of mercury ............................................................ 77
3.4.2 Toxicity of mercury and its compounds.................................. 78
3.4.3 Handling of mercury .............................................................. 78
3.4.4 References dealing with mercury ........................................... 80
4 Appendix ............................................................ 82
4.1 Technical data............................................................................. 82
4.2 Scope of delivery.........................................................................88
4.2.1 VA Computrace 2.797.0010 .................................................. 88
4.2.2 VA Computrace 2.797.0020 .................................................. 93
4.2.3 VA Computrace 2.797.0030 .................................................. 95
4.3 Options .......................................................................................99
4.3.1 General options ..................................................................... 99
4.3.2 6.5327.000 MVA-Hg: Equipment for Hg-determination....... 102
4.3.3 6.5327.010 MVA-As: Equipment for As-determination ........ 104
4.3.4 6.5327.020 MVA-CVS: Equipment for CVS/CPVS ................. 106
4.3.5 Accessories for the automated addition of auxiliary solutions108
4.3.6 Automation for trace analysis .............................................. 109
4.3.7 Automation for electroplating bath analysis ........................ 110
4.4 Validation / GLP.................................................................. 112
4.5 Warranty and certificates.......................................................... 113
4.5.1 Warranty ............................................................................. 113
4.5.2 Declaration of Conformity ................................................... 114
4.5.3 Quality Management Principles ........................................... 115
4.6 Index......................................................................................... 115
797 VA Computrace / Hardware-Manual 8.797.8001EN
II
Inhaltsverzeichnis
List of figures
Fig. 1: Front of the 797 VA Computrace Stand ..................................... 2
Fig. 2: Rear of the 797 VA Computrace Stand ......................................3
Fig. 3: Right side view of the 797 VA Computrace Stand (fully
equipped)..................................................................................
Fig. 4: Left side view of the 797 VA Computrace Stand (fully
equipped)..................................................................................
Fig. 5: Connection to PC ....................................................................14
Fig. 6: Measuring head arm................................................................15
Fig. 7: Scheme showing the inert gas connections at the 797 VA
Computrace Stand...................................................................
Fig. 8: Multi-Mode-Electrode.............................................................. 21
Fig. 9: Adding the mercury.................................................................22
4
4
19
Fig. 10: Setting up the filling station.....................................................26
Fig. 11: Filling the capillary...................................................................26
Fig. 12: Measuring head arm with rotating disk electrode (RDE) ...........35
Fig. 13: Construction of the reference electrode...................................36
Fig. 14: Construction of the auxiliary electrode.....................................39
Fig. 15: Electrical connection of the 863 Compact Autosampler ...........47
Fig. 16: Tubing connections for operation of the 863 Compact
Autosampler............................................................................
Fig. 17: Installation of accessories for rinsing and siphoning off............48
Fig. 18: Adjusting the pipetting needle.................................................49
Fig. 19: Complete system for automation with the 838 Advanced
Sample Processor ....................................................................
Fig. 20: Tubing connections for the rinsing equipment with the 838
Advanced Sample Processor ....................................................
Fig. 21: Electrical connection for a combined system with the 838
Advanced Sample Processor ....................................................
Fig. 22: Tubing connections for Suppressor determination with the
838 Advanced Sample Processor (and DT) with a combined
system.....................................................................................
47
55
55
56
57
Fig. 23: Tubing connections for Brightener determination with the
838 Advanced Sample Processor with a combined system .......
Fig. 24: Measuring head for a combined system with the 838
Advanced Sample Processor ....................................................
Fig. 25: Electrical connection for Suppressor determination with the
838 Advanced Sample Processor .............................................
797 VA Computrace / Hardware-Manual 8.797.8001EN
57
58
59
III
Inhaltsverzeichnis
Fig. 26: Tubing connections for Suppressor determination (with DT)
with the 838 Advanced Sample Processor ...............................
60
Fig. 27: Tubing connections for Suppressor determination (with RC)
with the 838 Advanced Sample Processor ...............................
60
Fig. 28: Measuring head for Suppressor determination with the 838
Advanced Sample Processor....................................................
61
Fig. 29: Electrical connection for Brightener determination with the
838 Advanced Sample Processor and MLAT ............................
62
Fig. 30: Tubing connections for Brightener determination for
samples>10mL with the 838 Advanced Sample Processor
and MLAT...............................................................................
63
Fig. 31: Tubing connections for Brightener determination for
samples<10mL with the 838 Advanced Sample Processor
and MLAT...............................................................................
63
Fig. 32: Measuring head for Brightener determination for
samples>10mL with the 838 Advanced Sample Processor
and MLAT...............................................................................
64
Fig. 33: Measuring head for Brightener determination for
samples>10mL with the 838 Advanced Sample Processor
and MLAT...............................................................................
64
Fig. 34: Electrical connection for Brightener determination with the
838 Advanced Sample Processor and LAT ...............................
65
Fig. 35: Tubing connections for Brightener determination with the
838 Advanced Sample Processor and LAT ...............................
66
Fig. 36: Tubing connections for Brightener determination with the
838 Advanced Sample Processor and LAT ...............................
66
Fig. 37: Communication diagram for VA.............................................. 69
Fig. 38: Communication diagram for LAT............................................. 70
Fig. 39: Communication diagram for MLAT ......................................... 71
Fig. 40: Communication diagram for DT .............................................. 72
Fig. 41: Communication diagram for "RC Record response curve"........ 73
Fig. 42: Communication diagram for "RC Sample with response
curve".....................................................................................
74
797 VA Computrace / Hardware-Manual 8.797.8001EN
IV
1.1 Instrument description
1 Introduction
1.1 Instrument description
797 VA Computrace is a PC controlled system for voltammetry, which consists of the
following parts:
1.797.0010 VA Computrace Stand with accessories
6.2151.020 Connecting Cable
6.6053.030 797 VA Computrace Software (current version)
For a detailed description of the PC software «797 VA Computrace Software» see the
797 Software Manual.
This 797 Hardware Manual describes the installation and maintenance of the 797
VA Computrace Stand and its accessories. The central element of this Stand is the
Multi-Mode Electrode (MME), which combines the dropping mercury electrode
(DME/SMDE) and the stationary hanging mercury drop electrode (HMDE) in a single
construction. The rotating disk electrode (RDE) can also be used in the stand.
The 797 VA Computrace Stand is controlled with the PC-Software «797 VA Computrace Software», parameters necessary for the VA measurement are sent from the PC
to the VA Computrace via USB connection. The data acquisition at the 797 VA Computrace Stand is started and controlled by the PC-Software «797 VA Computrace
Software», which receives and stores the measurement data. At the end of the determination, the recorded data are sent back to the PC where they are evaluated and
saved in a determination file.
Operation of the 797 VA Computrace Stand follows the potentiostatic 3-electrode
principle in which the voltage of the working electrode is controlled by means of a virtually currentless reference electrode to the preset desired value and the current flows
across a separate auxiliary electrode.
797 VA Computrace / Hardware-Manual 8.797.8001EN
1
1 Introduction
1.2 Parts and controls
In this section you will find the numbers and designations of the parts
and controls of the 797 VA Computrace Stand. The numbering applies
throughout the instructions for use, i.e. bold numbers in the text (e.g.
7 ) refer to the parts and controls illustrated here.
2
3
4
1
Fig. 1: Front of the 797 VA Computrace Stand
Mains pilot lamp
1
lit up when instrument switched on
Cover of measuring head arm
2
hinged
Release slide
3
to release fixture of the lifted measuring
head arm
Stopper (6.2709.080)
4
to close the pipetting opening
Gas wash bottle (6.2405.030)
6
for inert gas supply (filling with dist.
water, see section
Measuring vessel
7
when measuring head arm is fully raised, the measuring vessel can be pulled
forward out of the holder
Drip pan (6.2711.040)
8
2.2.5)
5
5
6
7
8
Holder for measuring vessel
5
2
797 VA Computrace / Hardware-Manual 8.797.8001EN
1.2 Parts and controls
12 9 13
16 10 11
Type: 1.797.0010
Nr.:___________
MSB 1
14
15
MSB 2 MSB 3
USB 2
USB 1
19
PC
Made by Metrohm Herisau Switzerland
18
Fig. 2: Rear of the 797 VA Computrace Stand
Connection for inert
9
gas lead-off
Connection for optional waste
10
solution lead-off
Connection for inert gas supply
11
required pressure:
p = 1 ± 0.2 bar
MSB1 – MSB3
12
(Metrohm Serial Bus)
Connections for Dosing devices
Remote
17
Fuse
100 - 240 V: 1.6 A(TH)
f = 50-60 Hz
S= 120 VA
WARNING - Fire Hazard -
For continued protection replace only
with the same type and rating of fuse
Fuse cover
15
Changing the fuses, see section
Mains connection plug
16
mains connection, see section
Remote
17
Connection for Sample Changer and
Rinsing Equipment
PC
18
Connection socket for connection cable
6.2151.020 to PC, see section
3.2
2.1.1
2.2.3
Serial number
13
USB1 and USB2
19
Connections for peripherals like
Mains switch (on/off)
14
printer, ..., see section
2.12
on/off switching of instrument (the pilot
1 is lit up when the instrument is
lamp
on)
797 VA Computrace / Hardware-Manual 8.797.8001EN
3
1 Introduction
22 23 24 25
26 27
42
20
21
4
28 29 26 30 31
Fig. 3: Right side view of the 797 VA Computrace Stand (fully equipped)
38 39 40 41 20
32 6 33 34 30 35 36 37
21
4
43
23
24
53 52 51 50 49 35
47 32 43
4648
29 45 44
Fig. 4: Left side view of the 797 VA Computrace Stand (fully equipped)
4
797 VA Computrace / Hardware-Manual 8.797.8001EN
1.2 Parts and controls
4
Stopper (6.2709.080)
to close the pipetting opening
6
Gas wash bottle (6.2405.030)
for inert gas supply
(must be filled halfway with dist. H
see section
Electrode cable ”WE”
20
2.2.5)
connection for working electrode
2
O,
Electrode cable ”RE”
31
connection for reference electrode
Drive belt (6.1244.020)
32
connection between drive wheel
stirrer 28
PTFE tube (6.1819.000)
33
for inert gas delivery to gas wash bottle
6 (attached)
26
35 and
(MME or RDE)
FEP tubing (6.1805.180)
34
Multi-Mode Electrode (MME)
21
for inert gas supply to MME
21
(6.1246.020)
details, see section
FEP tubing (6.1805.180)
22
for inert gas supply to measuring vessel
(attached)
2.3
Drive wheel of drive motor
35
FEP tubing (6.1805.040)
36
for inert gas delivery to gas wash bottle
6 attached.
Measuring head arm
23
carrier plate with permanently attached
measuring head, raisable
Measuring head
24
measuring vessel upper half made of
PTFE; with openings for electrodes,
stirrer, gas and liquid supply lines
Dummy stopper (6.1446.040)
25
Reference electrode
26
comprising 6.0728.020 Ag/AgCl Reference system and 6.1245.010 Electrolyte
vessel (details, see section
Nipple (6.2730.030)
27
2.5)
for mounting the 4-way microtip
dummy stopper
Stirrer (6.1204.200)
28
30 or a
Slotted screw for controlling the
37
inert gas flow
: The factory setting of ca. 20 L/h
Note
should not be changed without good
reason!
FEP tubing (6.1805.020)
38
for inert gas lead-off (attached)
FEP tubing (6.1805.090)
39
for inert gas lead-off (attached)
FEP tubing (6.1805.180)
40
for inert gas supply to tapping mechanism (attached)
Electrode cable ”AE”
41
connection for auxiliary electrode
FEP tubing (6.1805.180)
42
for inert gas supply to MME
43
21
PTFE tube (6.1819.000)
29
(attached)
4-way microtip (6.1824.000)
30
Auxiliary electrode
43
for details see section
Dummy stopper (6.1446.040)
44
2.6
for delivery of solutions; with 4 lengths
of PTFE tubing with connecting nipples
for Dosing devices
797 VA Computrace / Hardware-Manual 8.797.8001EN
Dummy stopper (6.1446.040)
45
5
1 Introduction
PTFE tube (6.1819.010)
46
for optional supply of the waste solution
to gas wash bottle
Gas wash bottle (6.2405.030)
47
47 (attached)
for separating mercury from the waste
solution (attached)
PTFE tube (6.1819.010)
48
for optional siphoning off the waste
solution from gas wash bottle
47
(attached)
Dummy cell connection ”WE-D”
49
differential mode simulation (peak/wave)
Dummy cell connection ”WE-L”
50
linear mode simulation (RC element)
Dummy cell connection ”RE”
51
Dummy cell connection ”AE”
52
Slotted screw for controlling the
53
tapping power in the DME or SMDE
case
: The factory setting should not be
Note
changed without good reason!
6
797 VA Computrace / Hardware-Manual 8.797.8001EN
1.3 Information about the Instructions for Use
1.3 Information about the Instructions for Use
Please read through these Instructions for Use carefully before you put
the 797 VA Computrace Stand into operation. The Instructions for Use
contain information and warnings to which the user must pay attention in order to assure safe operation of the instrument.
1.3.1 Organization
This 8.797.8001EN Hardware Manual for the 797 VA Computrace Stand provides a
comprehensive overview of the installation, operation, and technical specifications of
these instruments. The Instructions for Use are divided into the following 4 sections:
Section
Section
1 Introduction
2 Installation
General instrument description
Numbers and designations of the parts and controls
Safety instructions
Installation of 797 VA Computrace Stand
Installation of working, reference and auxiliary electrodes
Attachment of 700 and 800 Dosinos
Attachment of 685 and 805 Dosimats
Attachment of the 863 Compact Autosampler
Attachment of the 838 Advanced Sample Processor
Section
Section
To find the required information on the instrument please use either the Table of
contents or the Index at the back.
3 Safety
Electrical safety
Safety considerations in the handling of mercury
4 Appendix
Scope of delivery, options, validation, warranty, certification, index
797 VA Computrace / Hardware-Manual 8.797.8001EN
7
1 Introduction
1.3.2 Notation and pictograms
The following notations and pictograms (symbols) are used in these Instructions for
Use:
Mode Parameter or entry value
15 Part or control
Hazard
This symbol draws attention to a
possible danger to life or of injury if
the associated directions are not
followed correctly.
Warning
This symbol draws attention to
possible damage to instruments or
instrument parts if the associated
directions are not followed correctly.
Caution
This symbol marks important information. First read the associated
directions before you continue.
Comment
This symbol marks additional
information and tips.
8
797 VA Computrace / Hardware-Manual 8.797.8001EN
1.4 Support documentation
1.4 Support documentation
1.4.1 Application-Bulletins
The «Application Bulletins» is a collection of analytical methods, application examples
and literature references. Of Metrohm's approximately 200 Application Bulletins, ca.
60 refer to Polarography and Voltammetry. All these Application Bulletins are available
on request free of charge from your Metrohm supplier.
The examples listed here substantiate the versatility of the polarographic and voltammetric methods for a range of applications including both inorganic and organic substances. At any time you will find an updated list of the Application Bulletins with the
option for download in the Internet under «
Most of the methods required to run the applications described in the Application Bulletins are installed when the 797 VA Computrace software is installed.
No. Title
36 Polarographic analysis – Half-wave potentials of inorganic substances
50 Polarographic determination of lead in petrochemical products
57 Polarographic determination of nicotine
www.metrohm.com ».
60 Polarographic determination of fructose
70 Polarographic nitrate determination in water samples, soil and plant extracts,
vegetable juices, meat and sausage products, fertilizers, liquid manure etc.
73 Polarographic analysis – Half-wave potentials of organic substances
74 Polarographic and stripping voltammetric analysis methods for thallium, antimony,
bismuth and iron (copper, vanadium)
76 Polarographic determination of nitrilotriacetic acid (NTA) and ethylenediamine-
tetraacetic acid (EDTA)
96 Stripping voltammetric analysis of mercury
97 Voltammetric determination of tocopherols (vitamin E) in edible oils and fats
98 Determination of ascorbic acid (vitamin C) and its compounds
105 Determination of permissible lead and cadmium levels in crockery and glassware
110 Polarographic determination of free cyanide
113 Determination of lead, cadmium and copper in foodstuffs, waste water and
sewage sludge by anodic stripping voltammetry after digestion
114 Polarographic determination of five metal ions (copper, cobalt, nickel, zinc and
iron) in a single operation
116 Polarographic determination of chromium in small quantities
117 Determination of selenium by stripping voltammetry
123 Voltammetric determination of iron and manganese in water samples
126 Polarographic determination of quinine
127 Polarographic determination of nitrite in water samples, meat and sausages
131 Voltammetric determination of aluminum
132 Polarographic determination of molybdenum in strongly ferruginous substances
and ferrous metals
136 Polarographic determination of styrene in polystyrenes and copolymers
141 Analysis of edible fats and oils
797 VA Computrace / Hardware-Manual 8.797.8001EN
9
1 Introduction
No. Title
146 Direct polarographic determination of trace amounts of molybdenum in water
147 Simultaneous trace determination of seven metal ions (Zn, Cd, Pb, Cu, Ni, Co, Fe) in
«electronic grade» materials with the aid of stripping voltammetry
176 Simultaneous determination of lead and tin by anodic stripping voltammetry
179 Polarographic determination of maleic and fumaric acid alone or in mixtures
186 Determination of aluminum in water samples by adsorptive stripping voltammetry
190 Polarographic determination of 4-carboxybenzaldehyde in terephthalic acid
191 Polarographic determination of cystine and cysteine simultaneously
192 Determination of thiourea in the lower ppm and ppb range by polarography and
stripping voltammetry
196 Polarographic determination of formaldehyde
199 Polarographic determination of sulphide and sulphite
207 Stripping voltammetric analysis of silver
213 Polarographic determination of nicotinamide
215 Polarographic determination of folic acid (vitamin B9, vitamin BC)
218 Polarographic determination of thiamine (vitamin B1)
219 Polarographic determination of riboflavin (vitamin B2)
220 Voltammetric determination of platinum and rhodium in the ultratrace range
221 Standard methods in water analysis – use of Metrohm instruments
224 Polarographic determination of pyridoxine (vitamin B6)
226 Determination of arsenic by anodic stripping voltammetry at the rotating gold
electrode
231 Voltammetric determination of zinc, cadmium, lead, copper, thallium, nickel and
cobalt in water samples according to DIN 38406 E 16
241 Determination of cadmium and lead at the «Ultra Trace» graphite electrode by
anodic stripping voltammetry
242 Determination of tungsten at the «Ultra Trace» graphite electrode by anodic
stripping voltammetry
243 Determination of chromium at the «Ultra Trace» graphite electrode by cathodic
stripping voltammetry
250 Polarographic determination of diazepam in body fluids and pharmaceutical
preparations
251 Polarographic determination of cinchocaine (dibucaine) in pharmaceutical prepara-
tions
254 Determination of zinc, cadmium, lead and copper by anodic stripping voltammetry
using carbon electrodes
266 Voltammetric determination of titanium and uranium
276 Validation of Metrohm VA instruments using Standard Operating Procedures
1.4.2 Application Notes
The «Application Notes» present application information in concentrated form. In the
field of voltammetry, there are at present approximately 120 Application Notes (in
English), which can be viewed in the Internet under «
10
797 VA Computrace / Hardware-Manual 8.797.8001EN
www.metrohm.com » and cop-
1.4 Support documentation
ied from there. All these Application Notes are printed in the 8.757.2003 VA Applications Collection supplied with the instrument. All methods required to run the ap-
plications described in the Application Notes are installed when the 797 VA Computrace software is installed.
1.4.3 Monographs
The «Metrohm Monographs» listed below impart theoretical fundamentals and general information on measurement techniques and sample preparation of polarography
and voltammetry. All these monographs are available on request free of charge from
your Metrohm supplier.
Title
First aid for polarography and voltammetry (8.693.1071)
Sample preparation techniques in voltammetric trace analysis
Inorganic Adsorptive Stripping Analysis
Organic Stripping Analysis
Stripping Voltammetry
Electrode Reaction Kinetics determined by Cyclic Voltammetry
The Application of VA Techniques to the Galvanic/Plating Industry
Practical voltammetry (8.757.5003)
Introduction to Polarography and Voltammetry (8.027.5003)
Voltammetric analysis methods in electroplating (8.108.5002EN)
1.4.4 Reprints
The following reprints reporting on practical applications are available on request free
of charge from your Metrohm supplier.
Title
Investigations of oxidative UV photolysis:
I. Sample preparation for the voltammetric determination of Zn, Cd, Pb, Cu, Ni and Co in
waters
Investigations of oxidative UV photolysis:
II. Sample preparation for the voltammetric determination of mercury in water samples
Determination of Zn, Cd, Pb, and Cu in soils and sewage sludges by microprocessorcontrolled voltammetry in comparison with AAS
Voltammetric instrument for training and trace analysis
797 VA Computrace / Hardware-Manual 8.797.8001EN
11
2 Installation
2 Installation
This section offers a full description of the 797 VA Computrace Stand
and provides detailed information on the various electrodes and the
stirrer. Reliable operation of the instrument is assured only if you
follow the instructions in this section exactly.
2.1 Setting up the instrument
2.1.1 Packaging
The 797 VA Computrace Stand is supplied together with the separately packed accessories in special packages designed to ensure excellent protection. These contain
shock-absorbing foam linings. The instrument itself is packed in an evacuated polyethylene bag. As only these special packaging guarantees indemnified transport of the
instrument, it is essential you store it in a safe place.
2.1.2 Check
After recipt, immediately check whether the shipment is complete and has arrived
without damage (compare with delivery note and list of accessories in sections
the case of transport damage, see instructions in section
4.5.1 "Warranty".
2.1.3 Location
Place the 797 VA Computrace on a laboratory bench in a position suitable for operation and which is free from vibrations, protected against corrosive atmospheres and
contamination by chemicals. The drip pan
front side of the 797 VA Computrace Stand to catch drops (see
8 (6.2711.040) has to be placed at the
Fig. 1).
2.2 Installation of the 797 VA Computrace Stand
If the 797 VA Computrace Stand is connected to the power supply,
the instrument may not be opened or parts removed, as there is a
danger of contact with live components. Before you open the 797 VA
Computrace Stand to change components or for maintenance or
repair work, always switch off the instrument by setting the mains
switch
from the mains connection plug
14 to the OFF position and then disconnect the mains cable
16 of the 797 VA Computrace Stand.
4.2). In
2.2.1 Mains cable and mains connection
The instrument is supplied with one of three mains cables:
• 6.2122.020 with plug SEV 12 (Switzerland, …)
• 6.2122.040 with plug CEE(7), VII (Germany, …)
• 6.2133.070 with plug NEMA 5-15 (USA, …)
which are three-cored and fitted with a plug with a grounding pin. If a different plug
has to be fitted, the yellow/green lead (IEC standard) must be connected to protective
earth (protection class 1).
12
797 VA Computrace / Hardware-Manual 8.797.8001EN
2.2 Installation of the 797 VA Computrace Stand
Any break in the grounding inside or outside the instrument can make
it a hazard!
Plug the mains cable into mains connection plug
(see
16 of the 797 VA Computrace Stand
Fig. 2).
2.2.2 Switching the instrument on/off
The 797 VA Computrace Stand is switched on and off using mains switch 14. When
the instrument is switched on, the pilot lamp
1 lights up.
2.2.3 Connection to the PC
The 797 VA Computrace Stand is connected to the PC via USB Cable 6.2151.020.
Proceed as follows:
The 797 VA Computrace Stand must not be connected until the Software is installed.
1 Software installation
• Switch on PC and start operating system (Windows™ 2000, XP Professional
or Vista Professional)) without connection of the 797 VA Computrace via
USB cable.
• Insert installation CD into CD drive.
• If the autorun option for the CD drive is disabled, select
Browse for the
• Click on "
Setup.exe file on the installation CD and click on <OK>.
797" and follow the instructions given in the setup program. The
software package will be installed in the desired directory (the default directory is
Program Files/Metrohm/797 VA Computrace).
2 Connection of the 797 VA Computrace
• Connect 797 VA Computrace to the PC using the 6.2151.020 USB cable
and switch on the 797 VA Computrace. The PC detects a new USB device
and starts the setup wizard. Insert installation CD into CD drive and follow
the wizard instructions always selecting the recommended default options.
• Start the 797 VA Computrace Software.
<Start> and Run.
The setup wizard is started three times when installing the instrument
driver. All three installation steps must be conducted to ensure proper
operation.
797 VA Computrace / Hardware-Manual 8.797.8001EN
13
2 Installation
797
PC
6.2151.020 USB Cable
Fig. 5: Connection to PC
In case your computer does not start if the 797 VA Computrace stand
is switched on, it might is due to an older version of the BIOS. These
BIOS versions are not able to handle USB Hubs in a correct way.
In that case, start the computer first, and switch on 797 VA Computrace stand as soon as Windows booting is finished.
2.2.4 Equipping the measuring head
The fixtures inserted in the openings and connections of the measuring head 24 in
the 797 VA Computrace Stand depend on the working electrode selected (MME or
RDE) (see
Electrode is illustrated in section
tating disk electrode in section
When equipping the measuring head for the first time, the best procedure is as follows:
1 Preparations
2 Insert dummy stoppers
Fig. 6). The fully equipped measuring head for operation with a Multi-Mode
1.2 (Fig. 3 und Fig. 4), that for operation with a ro-
2.4 (Fig. 12).
• Prepare Multi-Mode Electrode MME 21 (details, see section 2.3) or rotating
disk electrode RDE (details, see section
• Prepare reference electrode
• Tilt back cover
2 of measuring head arm.
• Screw dummy stopper 45 (6.1446.040) into opening 55.
• Screw dummy stopper
44 (6.1446.040) into opening 56.
2.4) for operation.
26 (details, see section 2.5.2) for operation.
14
797 VA Computrace / Hardware-Manual 8.797.8001EN
2.2 Installation of the 797 VA Computrace Stand
3 Insertion of 4-way microtip (option)
For automatic solution addition with Dosinos or Dosimats, the 6.1824.000 4way microtip has to be installed. Proceed as follows:
• Remove stopper from nipple
27 and insert 4-way microtip 30 into nipple as
far as it will go.
• Tighten nipple using a 6.2739.010 Wrench until the 4-way microtip can no
longer move.
• Pull the 4 lengths of PTFE tubing of the 4-way microtip in succession from
above through the opening
2.8).
tion
68 (connection of Dosinos or Dosimats see sec-
4 Install stirrer or RDE
in operation with MME:
• Insert stirrer (6.1204.200) in opening
• Stretch drive belt
of the stirrer
32 (6.1244.020) between drive wheel 35 and drive shaft
.
63 as far as it will go.
in operation with RDE:
• Screw electrode tip
also section
2.4).
• Insert RDE in opening
• Stretch drive belt
98 (6.1204.XXX) to drive shaft 99 (6.1204.210) (see
63 as far as it will go.
32 (6.1244.020) between drive wheel 35 and drive shaft
99 of the RDE.
• Attach electrode cable
20 (WE) to the RDE: push cable lug under the screw
and then tighten screw firmly.
54
55
56
24
57
58
23
59 60 61 62 65 66 67 68 69 70
Fig. 6: Measuring head arm
23
Measuring head arm
24
Measuring head
6463
Opening
54
for auxiliary electrode
43 (6.0343.000 Pt
- auxiliary electr. or optional GC electr.
comprising 6.1241.020 Electrode holder
and 6.1247.000 GC tip)
797 VA Computrace / Hardware-Manual 8.797.8001EN
15
2 Installation
Threaded opening
55
for dummy stopper
Threaded opening
56
for dummy stopper
Pipetting opening
57
45 (6.1446.040)
44 (6.1446.040)
for the manual addition of solutions,
closed with stopper
Opening
58
4 (6.2709.080)
in operation with MME:
for Multi-Mode Electrode
21
(6.1246.020)
in operation with RDE:
for 6.2709.040 Stopper
Threaded opening
59
for FEP tubing
22 (6.1805.180, already
permanently attached); inert gas supply
to measuring vessel
Threaded opening
60
for dummy stopper
Opening
61
for reference electrode
7
25 (6.1446.040)
26 (Ag/AgCl
reference system and 6.1245.010
Electrolyte vessel)
Threaded opening
62
for nipple
stopper or 4-way microtip
27 (6.2730.030) with dummy
30
(6.1824.000)
Threaded opening
64
for FEP tubing
40 ((6.1805.180, already
permanently attached); inert gas supply
for tapping mechanism
Threaded opening
65
for FEP tubing
39 (6.1805.090, already
perm. attached); inert gas lead-off
Threaded opening
66
for FEP tubing
22 (6.1805.180, already
permanently attached); inert gas supply
from gas wash bottle
vessel
67
7
Threaded opening
for FEP tubing
36 (6.1805.040, already
6 to measuring
permanently attached); inert gas supply
to gas wash bottle
Opening
68
6
for feed-through of tubing connections
of 4-way microtip
Threaded opening
69
30 (6.1824.000)
for FEP tubing (6.1805.180); optional
waste solution lead-off
Threaded opening
70
for FEP tubing
38 (6.1805.090, already
permanently attached); optional waste
solution supply from gas wash bottle to
waste
Opening
63
in operation with MME:
for stirrer
28 (6.1204.200)
in operation with RDE:
for rotating disk electrode, comprising
drive shaft
trode tip
99 (6.1204.210) and elec-
98 (6.1204.XXX)
5 Install reference electrode
• Insert reference electrode 26 in opening 61.
• Attach electrode cable
under the screw and then tighten screw firmly.
• Turn reference electrode so that the electrode cable points to the rear and
not to the side (in the latter position it may become kinked and damaged
when cover
31 (RE) to reference electrode: push cable lug
2 is closed).
16
797 VA Computrace / Hardware-Manual 8.797.8001EN
2.2 Installation of the 797 VA Computrace Stand
6 Install auxiliary electrode
• Insert auxiliary electrode 43 (6.0343.000 Pt auxiliary electrode or GC auxil-
iary electrode, see section
• Attach electrode cable
2.6) in opening 54.
41 (AE) to auxiliary electrode: push cable lug under
the screw and then tighten screw firmly.
• Turn auxiliary electrode 39 so that the electrode cable 37 points to the rear
and not to the side (in the latter position it may become kinked and damaged when cover
2 is closed).
7 Install MME or dummy stopper
in operation with MME:
• Carefully insert Multi-Mode Electrode
21 (6.1246.020) in opening 58 (the
underside of the capillary must not touch the measuring head during insertion) and push in as far as it will go.
• Screw FEP tubing
34 (6.1805.180) for inert gas supply into connection 71
of the MME.
• Screw FEP tubing
42 (6.1805.180) for inert gas supply into connection 72
of the MME.
• Attach electrode cable
20 (WE) to screw connection 88 of the MME: push
cable lug under the screw and then tighten screw firmly.
in operation with RDE:
• Insert stopper
97 (6.2709.040, option) into opening 58 as far as it will go
so that the two blind holes point to the rear of the stand.
• Screw FEP tubing
• Screw FEP tubing
34 (6.1805.180) into upper hole of stopper 97.
42 (6.1805.180) into lower hole of stopper 97.
8 Install measuring vessel
• Tilt back measuring head arm 23.
• Slide measuring vessel
solution or dist. H
the reference electrode are immersed in the liquid.
• Lower measuring head arm
2.2.5 Inert gas connection
Nitrogen (N2) is generally used as the inert gas to de-aerate the analyte solution and
for operation of the MME. The nitrogen must be of sufficient purity.
w(N
) ≥ 0.99996 (= 99.996%)
2
for general polarography/voltammetry
w(N
) ≥ 0.99999 (= 99.999% = "5 × 9")
2
for analyses in organic solvents; for determinations involving very high
current amplification (e.g. in the determination of very low concentrations without preceding enrichment)
For electroplating bath applications, using CVS or CPVS, no inert gas connection is required.
The scheme for de-aeration of the analyte solution and the inert gas connections at
the 797 VA Computrace Stand needed for operation of the MME is shown in
The inert gas connections are established as follows:
7 into holder 5 from the front and fill with analyte
O (storage solution) until the tips of the MME or RDE and
2
23 and cover 2.
Fig. 7.
797 VA Computrace / Hardware-Manual 8.797.8001EN
17
2 Installation
1 Fill gas wash bottle
• Unscrew gas wash bottle 6 from measuring head arm 23.
• Fill gas wash bottle half full with dist. H
O (for long-term measurements
2
with supporting electrolytes such as Acetic acid / Acetate buffer or Ammonia / Ammonium chloride buffer, fill with supporting electrolyte; for measurements in organic solvents fill with the used solvent).
• Screw gas wash bottle back on measuring head arm.
2 Connect inert gas supply
• Attach one end of 6.1801.080 PVC tubing to connection 11 of the 797 VA
Computrace Stand.
• Attach the other end of the 6.1801.080 PVC tubing to connection of the
inert gas bottle.
• Set inert gas pressure at gas bottle using the reducing valve to
p = 1 ± 0.2 bar.
• Open gas supply line at gas bottle.
3 Connect inert gas lead-off (option)
• Attach a length of suitable tubing (e.g. Metrohm 6.1805.030, length
150 cm) to connection
9 for inert gas lead-off.
• Route the other end of the lead-off tubing to a fume cupboard.
18
797 VA Computrace / Hardware-Manual 8.797.8001EN
2.2 Installation of the 797 VA Computrace Stand
V
2
V
3
N
2
V
1
71
V
4
72
6
53
Fig. 7: Scheme showing the inert gas connections at the 797 VA Com-
putrace Stand
37
6 Gas wash bottle (6.2405.030)
for inert gas supply (must be filled only halfway with dist. H
O or
2
supporting electrolyte, see also Fig. 3)
37 Slotted screw for controlling the inert gas flow for de-aeration
(see also Fig. 3)
Note
: The factory setting of ca. 20 L/h should not be changed
without good reason!
53 Slotted screw for controlling the tapping power in the DME
case (see also
Note
: The factory setting should not be changed without good
Fig. 4)
reason!
Connection for inert gas supply
71
of the MME
for raising and lowering the sealing needle in the MME (see also
section
Connection for inert gas supply
72
2.3.1 and Fig. 8)
of the MME
for pressurizing the mercury (see also section
2.3.1 and Fig. 8)
V1, V2, V3, V4 Valves
797 VA Computrace / Hardware-Manual 8.797.8001EN
19
2 Installation
2.3 Multi-Mode Electrode (MME)
The Multi-Mode Electrode combines the most important polarographic and voltammetric mercury electrodes in a single construction:
• HMDE Hanging mercury drop electrode
Mercury is forced through a glass capillary until a drop
forms at the capillary tip and the entire voltage sweep
performed on this single stationary drop; in general with
preceding enrichment (stripping voltammetry).
• DME Dropping mercury electrode
The classical electrode, the mercury drops fall from the
glass capillary at a controlled rate.
• SMDE Static mercury drop electrode
The latest electrode, it combines the features of the
DME and the HMDE: during the measurement, the drop
surface is constant and stationary (as with the HMDE);
however, for the complete voltage sweep several drops
are needed (renewal as with the DME).
2.3.1 Construction and operating characteristics of the MME
The construction of the 6.1246.020 Multi-Mode Electrode is shown in Fig. 8. The
mercury in the reservoir
end. The mercury flow is controlled by the sealing needle
lowered pneumatically. The different types of electrodes (HMDE, DME, SMDE) are implemented by timed opening or closing of the mercury flow using this sealing needle.
The operating characteristics of the MME are illustrated by
V1 (inert gas supply) is opened, the mercury in the reservoir 81 is pressurized. In
valve
the standby mode, a back pressure is built up in the interior of the slotted screw
which causes the built-in spring to press the sealing needle
opening of the glass capillary
the valve
gas pressure in the mercury reservoir
PTFE membrane of the slotted screw
The tapping mechanism of the DME and SMDE is triggered by brief opening and closing of valve
The mercury drops formed at the end of the capillary are very small and stable and
thus afford a very good signal/noise ratio. The mercury hermetically sealed in the reservoir comes into contact only with inert gas and other inert materials and suffices
for around 200'000 drops.
V3 allows the inert gas to escape thus releasing the back pressure. The inert
V4.
81 flows through the glass capillary 87 forming a drop at its
75 which can be raised or
Fig. 7 and Fig. 8. After
75 onto the capillary
87 thus preventing the outflow of mercury. Switching
81 presses the sealing needle 74 fixed to the
75 upwards and the mercury can now flow out.
74
20
797 VA Computrace / Hardware-Manual 8.797.8001EN
2.3 Multi-Mode Electrode (MME)
73
74
75
76
72
77
78
79
80
81
82
83
84
85
71 88
71 Connection for inert gas supply
72 Connection for inert gas supply
(for all MME operating modes)
Locking ring (4.420.2920)
73
for slotted screw
Slotted screw (6.1247.040)
74
with PTFE membrane and built-in spring
Sealing needle (6.1247.020)
75
Screw thread for slotted screw 74
76
Unused connection
77
Screw thread for slotted screw 79
78
Slotted screw (4.420.2960)
79
74
for replenishing the mercury with capillary fitted
86
87
Fig. 8: Multi-Mode-Electrode
797 VA Computrace / Hardware-Manual 8.797.8001EN
Electrical contact pin for mercury
80
Mercury reservoir
81
Screw thread for retaining nut 86
82
Insert ring (4.420.3011)
83
Sealing ring (4.420.2800)
84
made of silicone rubber
Locking ring (4.420.2870)
85
Retaining nut (4.420.2850)
86
Glass capillary (6.1226.030 or
87
6.1226.050)
Screw connection
88
electrical contact for "WE" electrode
cable
21
2 Installation
2.3.2 Filling the MME with mercury
When handling mercury, it is necessary to take special precautionary
measures. These are described in detail in section
All actions involving the electrode and mercury vessels must be performed in or over the drip pan
91 supplied (see Fig. 9 - Fig. 11).
The Hg reservoir
81 of the Multi-Mode Electrode 21 is filled with mercury of the hig-
hest degree of purity (mass fraction w ≥ 0.99999) as follows:
1 Prepare Multi-Mode Electrode
• Unscrew locking ring 73 from slotted screw 74 (this gray PVC ring is nee-
ded only to remove the slotted screws
2.3.9).
tion
• Turn slotted screw
74 in or out of the screw thread 76 using a suitable
74 or 79, see section 2.3.7 and sec-
coin until the contact surface of the black O-ring at the Plexiglas wall (thin,
black stripe) is just visible below the metal thread
• Remove the plastic cap used as a transport safeguard from the retaining
86.
nut
• Undo retaining nut
• Place Multi-Mode Electrode
in the electrode holder
86 fully and remove from screw thread 82.
21 with the capillary opening facing upwards
92 (see Fig. 9).
3.4.
76.
89
90
Fig. 9: Adding the mercury
21
Multi-Mode Electrode (6.1246.0020)
Syringe (6.2816.020)
89
Needle (6.2816.030)
90
Hg
92
Drip pan (6.2711.030)
91
Electrode holder (6.2615.030)
92
21
91
22
797 VA Computrace / Hardware-Manual 8.797.8001EN
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