Metrohm 785DMP User Manual

CH-9101 Herisau/Switzerland Tel. +41 71 353 85 85 Fax +41 71 353 89 01 CompuServe 100031,3703 Internet http://www.metrohm.com

785 DMP Titrino

Instructions for Use

8.785.1003

99.07 Ti

Table of contents

1 Overview...................................................................................................................1

2 Manual operation .....................................................................................................4

2.1 Keypad.......................................................................................................................... 4

2.2 Principle of data input .................................................................................................. 5

2.3 Text input......................................................................................................................6

2.4 Configuration, key <CONFIG>................................................................................... 7

2.5 Selection of the mode, key <MODE>...................................................................... 13

2.6 Parameters, key <PARAM> ..................................................................................... 14

2.6.1 Parameters for DET and MET.............................................................................14

2.6.2 Parameters for SET ............................................................................................. 24

2.6.3 Parameters for MEAS.......................................................................................... 33

2.6.4 Parameters for CAL............................................................................................. 35

2.6.5 Parameters for TIP............................................................................................... 37

2.7 Result calculations.....................................................................................................38

2.8 Statistics calculation...................................................................................................41

2.9 Common variables..................................................................................................... 43

2.10 Data output...............................................................................................................44

2.10.1 Reports for the output at the end of a determination....................................... 44

2.10.2 Display of the titration curve..............................................................................47

2.11 User name, key <USER>....................................................................................... 48

2.12 TIP, Titration procedure............................................................................................49

2.13 Method memory, keys <USER METH> and <CARD>........................................ 53

2.13.1 Key <USER METH>......................................................................................... 53

2.13.2 Key <CARD> ................................................................................................... 55

2.14 Calibration data, key <CAL.DATA>........................................................................ 58

2.15 Current sample data, key <SMPL DATA>............................................................. 59

2.16 Silo memory for sample data...................................................................................60

2.17 Storing determination results and silo calculations ................................................ 63

2.17.1 Storing determination results............................................................................ 63

2.17.2 Silo calculations................................................................................................. 64

3 Operation via RS232 Interface (green part)............................................................67

3.1 General rules..............................................................................................................67

3.1.1 Call up of objects................................................................................................. 68

3.1.2 Triggers................................................................................................................ 69

3.1.3 Status messages.................................................................................................70

3.1.4 Error messages...................................................................................................73

3.2 Remote control commands.......................................................................................77

3.2.1 Overview..............................................................................................................77

3.2.2 Description of the remote control commands....................................................97

3.3 Properties of the RS 232 Interface........................................................................... 126

3.3.1 Handshake ........................................................................................................ 126

3.3.2 Pin Assignment.................................................................................................. 129

3.3.3 What can you do if the data transfer does not work?....................................... 131

785 DMP Titrino

Table of contents

4 Error messages, Troubleshooting...................................................................... 133

4.1 Error and special messages....................................................................................133

4.2 Diagnosis..................................................................................................................138

4.3 Initialize RAM............................................................................................................ 148

4.4 Releasing a locked spindle with inserted Exchange Unit....................................... 149

5 Preparations.........................................................................................................150

5.1 Setting up and connecting the instruments ............................................................ 150

5.1.1 Titrino with Stirrer or Titration Stand.................................................................. 150

5.1.2 Connection of a printer......................................................................................151

5.1.3 Connection of a balance...................................................................................152

5.1.4 Connection of a Sample Changer ....................................................................153

5.1.5 Connection of a computer.................................................................................154

5.1.6 Connection of a Remote Box............................................................................ 155

5.2 Connection of electrodes, preparing titration vessel...............................................158

6 Appendix ..............................................................................................................161

6.1 Technical specifications...........................................................................................161

6.2 Pin assignment of the "Remote" socket................................................................... 164

6.2.1 Lines of the "Remote" socket during the titration.............................................. 166

6.2.2 Possible configurations of the activate pulse in SET and CAL........................ 167

6.3 Titrino validation........................................................................................................ 168

6.3.1 Electronic tests .................................................................................................. 168

6.3.2 Wet tests............................................................................................................ 168

6.3.3 Maintenance and adjustment of the Titrino...................................................... 168

6.4 Warranty and certificates.......................................................................................... 169

6.4.1 Warranty.............................................................................................................169

6.4.2 Certificate of Conformity and System Validation..............................................170

6.5 Scope of delivery and ordering designations.......................................................... 172

Index ........................................................................................................................ 175

785 DMP Titrino

Overview

Herisau Switzerland

f = 50 - 60 Hz

S = 15 W

Pol

Ref

Ind I

Ind II

Key-

board

RS 232

1 Overview

Front view of instrument: Rear view of instrument:

Remote

1.785 Nr.

100 - 240 V

Pt 100/1000

Made by Metrohm

785 DMP Titrino

Overview

Front view of instrument:

1 Exchange Unit

2 Display

3 Control keys and indicator lamps on the Titrino

Key < > Power switch

Key < 4 > Switching stirrer ON/OFF

Key <DOS> Dosing key. Dispensing is performed as long as

<DOS> is being pressed. Used e.g. to prepare the Exchange Unit. The dispensing rate can be set with potentiometer (5).

Key <STOP/FILL> - Stops procedures, e.g. titrations, conditioning.

- Filling after manual dosing with <DOS>.

Key <START> Starts procedures, e.g. titrations, conditioning.

Identical with key <START> of the separate

keypad. Indicator lamps: "COND." Lamp flashes when conditioning is performed

and the titration vessel is still wet. It is on if con-

ditioning is ok. "STATISTICS" Lamp is on when the "statistics" function

(calculation of mean and standard deviation) is

on. "SILO" Lamp is on when silo memory (for sample data)

is on.

4 Setting of display contrast

5 Controls the dosing rate during manual dosing with <DOS> and

subsequent filling

6 Opening for the memory card

785 DMP Titrino

Rear view of instrument:

7 RS232 interfaces

2 separate interfaces for the connection of printer, balance, and computer

8 Remote lines (input/output)

for the connection of the Remote Box, Sample Changers, robots etc.

9 Connection of electrodes and temperature sensor

• 2 high-impedance measuring inputs for pH and U measurements. They can either be used separately or for differential potentiometry, see page 158. Important: If you work with both measuring inputs in the same vessel, the same reference electrode must be used.

• 1 measuring input for polarized electrodes, e.g. KF electrode

• 1 measuring input for PT100 or Pt1000 temperature sensor

Overview

10 Connection for separate keypad

11 Connection for power cable

With power supplies where the voltage is subject to severe HF disturbances, the Titrino should be operated via an additional power filter, e.g. Metrohm 615 model.

12 Connection for stirrer

728 Magnetic Stirrer, 722 Rod Stirrer, 703 or 727 Ti Stand Supply voltage: 10 VDC (I ≤ 200 mA)

13 Rating plate

with fabrication, series and instrument number

785 DMP Titrino

2.1. Keypad

SILO

–9STATISTICS

MEAS/HOLD

+8USER

→↑←

↓

STOP

START

CARD

/6CAL.DATA

USER METH

)3DEF

(2C-FMLA

MODE

REPORTS

CURVE

2 Manual operation

2.1 Keypad

PARAMCONFIG

SMPL DATA

QUIT

ABC

–

6.2132.070

CLEAR ENTER

CONFIG Configuration. PARAM Parameters. SMPL DATA Sample data. STATISTICS ON/OFF switching of statistics calcu-

lations of consecutive determination, see page 41.

MEAS/HOLDON/OFF switching of measurements

between titrations and hold during titrations.

SILO ON/OFF switching of silo memory for

sample data, see page 60. CAL.DATA Calibration data, see page 58. CARD Management of memory card, see

;

page 55. C-FMLA Calculation values, see page 40. DEF Formulas, data output, sequence for

TIP, see page 38ff. USER METH Management of internal method mem-

ory, see page 53. PRINT Printing of reports, see page 45. REPORTS Result output. MODE Mode selection, see page 13. USER User name, see page 48. CURVE Switching result/curve display. ←,→ Selection of special values (dialog

marked with ":") ↑,↓ Cursor key for navigation. CLEAR Clears values, set special values. ENTER Stores values. STOP Stops methods. QUIT Quits inquiries, waiting times, printing. START Starts methods.

The third functions (inscriptions in the triangle) on the keys of the keypad are used for formula entry, see page 38.

785 DMP Titrino

2.2 Principle of data input

remote box: OFF

• If you press a key you will find a group of inquiries in the display.

configuration >monitoring >peripheral units >auxiliaries >RS232 settings COM1 >RS232 settings COM2 >common variables

configuration >peripheral units send to COM1: IBM send to COM2: IBM man.reports to COM: 1 balance: Sartorius stirrer control: OFF

configuration >monitoring >peripheral units >auxiliaries >RS232 settings COM1 >RS232 settings COM2 >common variables

Example key <CONFIG>:

In the first line you see where you are: You pressed

key <CONFIG> and you are now in the inquiries "configuration".

• The cursor is inverted. In our example the cursor is on the inquiry ">monitoring". You can move the cursor up and down with keys <↑> and <↓>.

• If a dialog text is marked with ">", it contains a group of inquiries itself. You go to this group pressing <ENTER>. Example inquiries of "peripheral units":

The first two lines indicate again where you are.

Then you find the inquiries. If a dialog text of an inquiry is marked with ":", you can select a value with keys <←> and <→> (forward/backward).

• A value is stored with <ENTER> and the cursor moves to the next inquiry.

• With key <QUIT> you move one level up, in our example you go back to ">peripheral units".

If you press <QUIT> once more you quit the in-

quiries in "configuration" altogether.

• If you can scroll, ↓ or ↑ appear in the right lower or upper corner of the display.

2.2 Principle of data input

785 DMP Titrino

2.3. Text input

REPORTS

2.3 Text input

Example storing a method:

user methods >store method method name: ********

<CLEAR>

ABC

user methods >store method: method name:

ABCDEFGHIJKLMNOPQRSTUVWXYZ abcdefghijklmnopqrstuvwxyz µ°!"#$&'()*+,-./ 0123456789

<QUIT>

user methods >store method method name: Text

<ENTER>

• Press key <USER METH>. Place the cursor to ">store method" and press <ENTER>. The name of the method which is currently in the working memory is displayed.

• Delete this name with <CLEAR>.

• Open the "text writing mode" with key <ABC>.

You can now select the desired character by means of the cursor keys, then confirm this character. Select the next character... When you confirmed the last character, i.e. your name is complete, you quit the text writing mode with <QUIT>. Confirm now the name with <ENTER>.

• During text input you can correct typing errors with <CLEAR>: <CLEAR> deletes the characters one by one.

• If you wish to modify an existing name (e.g. if you have names like Text 1, Text 2, Text 3), do not delete the existing name before you start the text input mode. Proceed then as follows:

1. Press <USER METH>, place the cursor to ">store method" and press <ENTER>.

2. Open the text writing mode directly: Press key <ABC>.

3. <CLEAR> now deletes the characters one by one or you can add additional characters.

4. If your text is complete, leave the text writing mode with <QUIT> and confirm the text with <ENTER>.

785 DMP Titrino

2.4 Configuration, key <CONFIG>

Key <CONFIG> serves to enter device specific data.

CONFIG

configuration >monitoring >peripheral units >auxiliaries >RS232 settings COM1 >RS232 settings COM2 >common variables

The set values apply to all modes.

monitoring:

Monitoring of instrument validation, pH calibration, service interval and printout of diagnostic report. peripheral units: Selection of printer, balance, stirrer control and COM for manual report output. auxiliaries: e.g. setting of dialog language, date time, type of result display. RS232 settings COM1 and 2: RS parameters for the COM's. common variables: Values of common variables.

The display texts of the Titrino are shown to the left. The values are the default values.

2.4 Configuration, key <CONFIG>

>monitoring

validation: OFF

time interval 365 d

time counter 0 d

calibration: OFF

Monitoring functions

Monitoring the validation interval (ON, OFF)

Monitoring is carried out at the end of the titrations and when the Titrino is switched on. If the monitoring responds the message "validate instrument" appears. The message vanishes with <CLEAR>. At the same time the counter is reset to zero.

If "on" has been set:

Time interval for validation (1...9999 d)

see also page 126. Identical for COM2.

Baud rate (300, 600, 1200, 2400, 4800, 9600, 19200, 38400, 57600, 115200)

Data bit (7, 8)

Stop bit (1, 2)

Parity (even, odd, none)

Handshake (HWs, SWline, SWchar, none)

see page 126.

Values of the common variables

C30 0.0 etc.

Common variables C30...C39 (0.. ± 999 999)

The values of all common variables are displayed. For creating of common variables see page 43.

785 DMP Titrino

2.4 Configuration, key <CONFIG>

Settings with key <CONFIG> and power ON

Proceed as follows:

1. Switch the Titrino OFF.

2. Press <CONFIG> and keep it pressed during switching the Titrino ON. The display shows the following:

Setup >lock >curve

>lock

<configuration>: OFF

<parameters>: OFF <smpl data>: OFF

recall method: OFF store method: OFF delete method: OFF

lock:

Locking keys <CONFIG>, <PARAM> and <SMPL DATA>, and the functions "recall method", "store method" and "delete method" of the internal method memory in the Titrino. curve: Changes the appearance of the curve printout.

lock

"ON" means that the corresponding function is not accessible anymore.

The corresponding key is locked.

The corresponding function in the internal method memory of the Titrino is locked.

785 DMP Titrino

2.4. Configuration, key <CONFIG>

>curve

grid: ON

frame: ON

scaling: Full

width 0.75

length 0.1

curve

The settings are valid for COM1 and COM2. If you change the printer type, the following settings are initialized according to the printer.

Grid drawing (ON, OFF)

Frame drawing (ON, OFF)

Type of scaling (Full, Auto)

Full: The scaling goes from the greatest to the smallest value. auto: The scaling from tick to tick, e.g. the smallest/greatest values lie in between the first/last tick.

Width (0.2...1.00)

1 is greatest width. If you set 1 you may loose the label at the right margin.

Length (0.01...1.00) Volume axis

Curve length per cylinder volume

0.01 100 cm

0.1 10 cm

0.5 2 cm 1 1 cm Time axis:

Curve length

0.01 100 cm

0.1 10 cm

0.5 2 cm 1 1 cm

785 DMP Titrino

2.5 Selection of the mode, key <MODE>

MODE

2.5 Selection of the mode, key <MODE>

;

–

mode mode: DET measured quantity: pH

Press key <MODE> until the desired mode is displayed and confirm with <ENTER>. Select the measured quantity pH, U, Ipol, Upol, (T) with <←> or <→> and confirm it also with <enter>.

The following modes can be selected:

• DET: Dynamic Equivalence-point Titration

• MET: Monotonic Equivalence-point Titration

• SET: Set Endpoint Titration.

• CAL: pH Calibration.

• MEAS: Measuring.

• TIP: Titration Procedure. Linking of various

commands and methods to a titration procedure.

These standard modes are equipped with a set of standard parameters. They only need few settings in order to be ready to work. TIP is an empty "shell". The TIP sequence has to be defined with <DEF>, see page 49.

You will find a survey of the modes in the short Instructions for use, page 10.

785 DMP Titrino

2.6. Parameters, key <PARAM>

2.6 Parameters, key <PARAM>

The key <PARAM> is used for the entry of values that

PARAM

2.6.1 Parameters for DET and MET

determine the modes. Values marked with "cond." are accessible during the conditioning in the SET mode. "**titr." means that these values can be changed during the titration. They influence the ongoing determination. Other values can only be changed in the inactive state. The display texts of the Titrino are shown to the left. The values are the default values.

parameters >titration parameters >stop conditions >statistics >evaluation >preselections

>titration parameters

meas.pt.density 4

DET

titration parameters

determine the course of the titration and measured value acquisition.

stop conditions:

Parameters for the automatic termination of the titration. statistics: Calculation of mean values and standard deviation, see page 41. evaluation: Parameters for the evaluation of EP's, fix EP's, and pK/HNP. preselections: ON/OFF of various auxiliary functions such as automatic requests after the start and activate pulse.

General titration parameters

Measuring point density (0...9)

0 means highest density, 9 lowest. Selection of the meas.pt.density, see page 20.

min.incr. 10.0 ul

DET

V step 0.10 ml

MET

Minimum increment (0...999.9 uL)

The increment is dispensed at the beginning of the titration and in the region of the equivalence point.

Size of volume increment (0...9.999 mL)

Dosing step. Small volume increments are needed to determine blank values or to assure accuracy with highly unsymmetrical curves. Selection of size of the increment, see page 20.

785 DMP Titrino

2.6 Parameters, key <PARAM>

dos.rate max. ml/min **titr.

signal drift 50 mV/min **titr.

equilibr.time 26 s **titr.

Dosing rate for volume increments (0.01...150 mL/min, max.)

<CLEAR> sets "max.". The maximum rate depends on the Exchange Unit: Exchange Unit max.

5 mL 15 mL/min 10 mL 30 mL/min 20 mL 60 mL/min 50 mL 150 mL/min

Drift criterion for measured value acquisition. (input range depends on the measured quantity: pH, U, Ipol: 0.5...999 mV/min, OFF Upol: 0.05...99.9 uA/min, OFF)

<CLEAR> sets "OFF". This type of measured value acquisition is often called an equilibrium titration. "OFF" means that the measured value is acquired after an equilibration time. This may be useful for slow titration reactions or when the response of the electrode assembly is slow.

Waiting time for measured value acquisition. (0...9999 s, OFF)

<CLEAR> sets "OFF". If no new equilibration time has been entered, the Titrino calculates an equilibration time appropriate to the drift, see page 19. The measured value is acquired as soon as the first criterion (drift or time) has been met.

start V: OFF

start V 0.0 ml

factor 0

dos.rate max. ml/min **titr.

Type of start volume (OFF, abs., rel.)

"OFF": start volume switched off "abs": absolute start volume in mL "rel.": relative start volume to sample size.

If "abs." is set:

Absolute start volume (0...999.99 mL)

If "rel." is set:

Factor for relative start volume (0...±999 999).

Calculated as: start V in mL = factor * sample size

Dosing rate for start volume (0.01...150 mL/min, max.)

<CLEAR> sets "max.". Maximum rate depends on the Exchange Unit: Exchange Unit max.

5 mL 15 mL/min 10 mL 30 mL/min 20 mL 60 mL/min 50 mL 150 mL/min

785 DMP Titrino

2.6. Parameters, key <PARAM>

pause 0 s **titr.

meas.input: 1

I(pol) 1 uA

U(pol) 400 mV

electrode test: OFF

temperature 25.0 °C

Waiting time (0...999 999 s)

Waiting time, e.g. for equilibration of the electrode after the start or reaction time after dosing of start volume. The pause can be aborted with <QUIT>.

Measuring input for pH and U (1, 2, diff.)

Request for measuring input for pH and U. Measuring input 1 or 2 or differential amplifier; connection of electrodes, see page 158.

With polarized electrodes, instead of the measuring input the

polarization current (-127...127 uA)

or the

polarization voltage (-1270...1270 mV, in steps of 10 mV)

is inquired.

Electrode test (OFF, ON)

Test for polarized electrodes. Performed on changeover from the inactive standby state to a measurement. "OFF" means that the test is not performed.

Titration temperature (-170.0...500.0 °C)

The temperature is continuously measured if a T sensor is connected. This parameter is used for temperature compensation in pH titrations.

>stop conditions

stop V: abs. **titr.

stop V 99.99 ml **titr.

factor 999999 **titr.

stop pH OFF **titr.

Stop conditions for the titration

If several stop conditions have been set, the criterion which is met first applies.

Type of stop volume (abs., rel., OFF)

"abs.": absolute stop volume in mL. "rel.": relative stop volume to sample size. "OFF": stop volume switched off. Stop volume is not

monitored.

If "abs." is set:

Absolute stop volume (0...9999.99 mL)

If "rel." is set:

Factor for relative stop volume (0...±999 999)

Calculated as: Stop V in mL = factor * sample size

Stop at measured value (input range dependent on measured variable:

pH: 0... ± 20.00, OFF U, Ipol: 0... ± 2000 mV, OFF Upol: 0... ± 200.0 uA, OFF)

<CLEAR> sets "OFF". "OFF" means that the criterion is not monitored.

785 DMP Titrino

2.6 Parameters, key <PARAM>

stop EP 9 **titr.

filling rate max. ml/min **titr.

>evaluation

EPC 5

Stop after a number of EP's have been found (1...9, OFF)

<CLEAR> sets "OFF". "OFF" means that the criterion is not monitored.

Filling rate (0.01...150 mL/min, max.)

<CLEAR> sets "max.". The maximum rate depends on the Exchange Unit: Exchange Unit max.

5 mL 15 mL/min 10 mL 30 mL/min 20 mL 60 mL/min 50 mL 150 mL/min

EP evaluation/recognition

See page 20 ff.

Equivalence point criterion (input range depends on mode. For DET:

0...200 For MET: pH: 0.10...9.99 U, Ipol: 1...999 mV Upol: 0.1...99.9 uA)

Threshold for the size of the jump, see page 22.

EP recognition: all

low lim.1 pH -20.00

up lim.1 pH 20.00

Recognition of EP's which fulfill the EP criterion. (all, greatest, last, window, OFF)

Selection of equivalence point recognition: "all": All equivalence points are recognized. "greatest": Only the greatest (steepest) equivalence

point is recognized.

"last": Only the last equivalence point is

recognized.

"window": Only EP's in specified windows are

recognized. "OFF": Evaluation switched off. If "window" is selected, lower and upper limits of windows are inquired.

Lower limit of window 1

and

upper limit of window 1 (Input ranges for both inquiries depend on the measured quantity): pH: 0...±20.00, OFF U, Ipol: 0...±2000 mV, OFF Upol: 0...±200.0 uA, OFF)

<CLEAR> sets "OFF". Only equivalence points are recognized which lie within the set lower and upper limits. The equivalence point numbering is defined with the windows, see page 22. Window inquiries continue until the lower limit is set to "OFF". Up to 9 possible windows. Always set both limits to ≠ OFF for a valid window.

785 DMP Titrino

2.6. Parameters, key <PARAM>

fix EP1 at pH OFF

pK/HNP: OFF

>preselections

req.ident: OFF

Interpolation of volumes at fixed times (input range depends on the measured quantity: pH: 0...±20.00, OFF U, Ipol: 0...±2000 mV, OFF Upol: 0...±200.0 uA, OFF)

<CLEAR> sets "OFF". If a fix end point has been set, the volume value for the input measured value is interpolated from the curve, see also page 23. The volume values are available as C5X. Fix EP's are inquired until "OFF" is set. Up to 9 fix EP's.

Evaluation of pK or HNP (ON, OFF)

pK evaluation in case of pH titrations and half neutralization potential for U, see page 23.

Preselections for the sequence

Request of identifications after start of titration. (id1, id1&2, all, OFF)

After start, sample identifications can be inquired automatically: Only id1, id1 & id2, all three id's or no inquiries.

req.smpl size: OFF

limit smpl size: OFF

low lim. 0.0 up lim. 999999

activate pulse: OFF

Request of sample size after start of titration (value, unit, all, OFF)

"all" requests the value, then the unit.

Limiting value check for sample size (ON, OFF)

With "on" the error message "sample size out." appears if the entry is outside the set limits. The limiting values are shown in the display window. The absolute value of the limit is checked during sample size input and during the calculation of the results. If "on" has been set:

Lower limit for sample size (0.0...999 999) Upper limit for sample size (0.0...999 999)

Pulse output on I/O line "activate" (L6, pin 1) of the remote socket (ON, OFF)

see page 166.

785 DMP Titrino

Titration sequence of DET and MET

<START>

(Start delay)

(Start conditions)

Stop conditions

Calculations

(Stirrer OFF)

Data output

2.6 Parameters, key <PARAM>

(Activate pulse)

(Stirrer ON)

(Request ident.)

(Request smpl size)

Titration: Dispense increments Acquire meas.values

After the start, the activate pulse is outputted and the stirrer switched on.

The start delay time is waited off. The sample identifications and the sample size are re-

quested. The start volume is dispensed (no meas.value acquisition)

and the pause is waited off. During the titration the volume increments are dispensed

and after each increment a measured value is acquired. Meas.values are either acquired drift controlled ("equilibrium titration") or a after a fixed waiting time. If you have not intentionally changed the equilibration time, it is calculated according to the formula:

150

equilibr.time in s = —————— + 5

ûDrift + 0.01 The criterion (drift or equilibration time) which is first met applies. This avoids "infinite" titrations. If the parameter "signal drift" is set "OFF", the measured values are acquired after a fixed equilibration time.

The titration is terminated according to the first criterion which is met.

The stirrer is switched off. Evaluations and calculations are carried out. Data are outputted.

785 DMP Titrino

2.6. Parameters, key <PARAM>

Reagent feeding and EP evaluation of DET

The reagent feeding of DET is similar to the controlling, a human being would apply in manually controlled titrations: Great volume increments are dosed far away from the EP, small increments in the region of the equivalence point. The size of the volume increments dosed by the Titrino is determined by the following parameters:

meas.pt.density The measuring point density is entered as a relative

value from 0...9. Input of a low number means small volume increments, i.e. a large measuring point density on the curve. A curve results which reproduces all fine details. "Fine details", however, also include signal noise, which can easily lead to unwanted equivalence points. A high number, i.e. low measuring density, on the other hand, allows a more rapid titration. The standard value of 4 is suitable for most cases. If you work with small cylinder volumes (1 or 2 ml), a small measuring point density may be advisable. In these cases you should also lower the drift for meas.value acquisition and set a higher EPC.

min.incr. Defines the minimum possible increment. This minimum

increment is dosed at the beginning of the titration and in the region of the equivalence point (for steep curves). Use low minimum increments only, if small volumes of titrant consumption are expected, e.g. in micro titrations; otherwise unwanted equivalence points may arise. The standard value of 10.0 uL is suitable for most cases.

EPC

The EP's are evaluated according to a special METROHM procedure which is so sensitive that even weak equivalence points are determined correctly.

Equivalence Point Criteria. The preset EPC is compared to the found ERC (Equivalence point Recognition Criteria) for each evaluated equivalence point. The size of the ERC is displayed in the titration curve, see page 47. The ERC is the first derivative of the titration curve overlaid with a mathematical function so that small maxima become higher and great maxima smaller. EP's whose ERC is below the preset EPC will not be recognized. For most cases the standard value of 5 is suitable. The evaluation can be repeated at any time after the titration in a "dry run" with changed evaluation criteria. The old titration data are not deleted until a new titration is started.

785 DMP Titrino

2.6 Parameters, key <PARAM>

Reagent feeding and EP evaluation of MET

In monotonic titrations, the volume increment is constant over the whole titration curve.

V step Volume increment.

A prerequisite for good accuracy is the correct size of the volume increments. A good value is given by V step = 1/20 VEP (VEP = volume of the EP). In any case, the increment size should always be between 1/10 VEP and 1/100 VEP; with steep jumps preferably in the region of 1/100 and with flat jumps preferably in the region of 1/10. The accuracy of the evaluation can not be increased by dispensing small increments as the changes in the measured value can then be of the same order of magnitude as the noise. This can produce "ghost EP's"!

The EP's are localized with an algorithm which is based on Fortuin and has been adapted by METROHM for numeric procedures. (METROHM Bulletin 2, No. 10,

1971). Here, the greatest change in the measured value is sought (∆n). The exact equivalence point is determined with an interpolation factor, which depends on the delta values before and after ∆n:

VEP = V0 + ρ ∆V VEP: EP volume V0: Total dispensed volume before ∆

∆V: Volume increment ρ : Interpolation factor (Fortuin)

EPC

∆

+∆

n-2

+∆n+∆

n-1

n+1

+∆

n+2



(In certain cases there are only 3 or 1 summand). EP's whose ERC is below the preset EPC will not be recognized. For most titrations the standard value is suitable. The evaluation can be repeated at any time after the titration in a "dry run" with changed evaluation criteria. The old titration data are not deleted until a new titration is started.

785 DMP Titrino

2.6. Parameters, key <PARAM>

U/mV

V/ml

U/mV

V/ml

EP recognition criteria for DET and MET

The parameter "EP recognition" offers you a range of possibilities to ensure selection of the EP you are interested in: If the desired jump is very large, you can select the "greatest" jump (with DET the steepest jump will be evaluated). Thus you always obtain just one EP per titration (EP1). If you wish to determine the sum of different components (e.g. acid or base numbers), the "last" jump can be the correct one. And finally you can set a "window" for each expected EP.

EP windows EP windows are used

• to suppress disturbing influences and EP's which are not needed.

• to increase the liability for the calculation of the results. The EP windows make an

unequivocal assignment of the EP's possible: per window one EP is recognized; the numbering of EP's is defined by the windows so that even if EP's are missing, the calculations are still performed with the correctly assigned EP volumes.

An EP window defines the range in which an EP is expected. EP's outside these ranges are not recognized. Windows are defined on the measured value axis.

EP window 2

EP window 1

EP 1

upper lim. 1

lower lim. 1

EP 1

+EP window 1

EP 2

2 EP's are recognized. Their numbering is defined by the windows: Window 1 ⇒ EP1 Window 2 ⇒ EP2

If more than 1 EP is expected, a window must be set for each EP.

Windows must not overlap. They may only touch each another.

Rule: If there are more than 1 EP in a window, the first jump is recognized as EP1, the second is not recognized. EP1 is marked as EP1 + to indicate that more than one EP has been found in the window

785 DMP Titrino

2.6 Parameters, key <PARAM>

Fix EP's

Fix EP's allow determination of the associated volume value for every inputted measured value on the titration curve. This function is useful for performing standard methods such as TAN/TBN determinations. For the evaluation of fix EP's, the pH calibration is advisable. The volume values of the fix EP's are available for the calculation as C5X: Fix EP1 ⇒ C51 : Fix EP9 ⇒ C59 Maximum 9 fix EP's are possible.

pK and HNP evaluation

The following relation (Henderson-Hasselbach), derived from the law of mass action, exists between the activities of a conjugate acid-base pair in aqueous solutions:

pH = pK + log (aB/aA) When the activities aB = aA, then pH = pK is valid. This value corresponds to the pH at the half neutralization point and can be taken from the titration curve. For pK determinations, a careful pH calibration is necessary. The pK value determined is an approximate value owing to the fact that the ionic strength of the solution has not been taken into account. For more exact values, titrations must be performed with decreasing ionic strength and the results extrapolated to zero ionic strength. The evaluation of pK's in aqueous solutions is limited to pK>3.5 due to the leveling effect of strong acids in aqueous solutions pK<10.5 because for weaker acids no inflection points can be found aqueous

solutions.

pK evaluation for polybasic acids and for acid mixtures is also possible. In non-aqueous solutions, the half neutralization potential (HNP) is often used instead of

pK. The HNP is evaluated accordingly. A start volume must be smaller than half of the equivalence point volume of the first EP. The pK/HNP values are available for calculation as C6X.

Minimum/maximum evaluation

Volumes at minimum or maximum voltage values are extrapolated. These volumes are accessible as variables C49 and C48 resp. and can be used in formulas.

785 DMP Titrino

2.6. Parameters, key <PARAM>

2.6.2 Parameters for SET

parameters >SET1 >SET2 >titration parameters >stop conditions >statistics >preselections

>SET1

EP at pH OFF **titr.

SET1, SET2:

Control parameters for EP1 and EP2.

titration parameters

are valid for the global titration sequence.

stop conditions:

Parameters for the termination of the titration. statistics: Calculation of mean values and standard deviation, see page 41. preselections: ON/OFF of various auxiliary functions such as automatic requests after the start and activate pulse.

Control parameters for EP1 or EP2, resp.

Preset EP1 (input range depends on the measured quantity: pH: 0...±20.00, OFF U, Ipol: 0...±2000 mV, OFF Upol: 0...±200.0 uA, OFF)

<CLEAR> sets "OFF". If EP1 is "OFF", no further inquiries under SET1 appear.

dynamics OFF **titr.

max.rate 10.0 ml/min **titr.

Distance from EP where constant dosing should stop and controlling begins. (control range, input range depends on the measured quantity: pH: 0.01...20.00, OFF U, Ipol: 1...2000 mV, OFF Upol: 0.1...200.0 uA, OFF)

<CLEAR> sets "OFF". "OFF" means largest control range, i.e. low titration. Outside the control range, dispensing is performed continuously, see also page 30.

Maximum dosing rate (0.01...150 mL/min, max.)

<CLEAR> sets "max.". This parameter determines primarily the addition rate outside the control range, see also page 30. The maximum rate depends on the Exchange Unit: Exchange Unit max.

5 mL 15 mL/min 10 mL 30 mL/min 20 mL 60 mL/min 50 mL 150 mL/min

785 DMP Titrino

2.6 Parameters, key <PARAM>

min.rate 25.0 ul/min **titr.

stop crit: drift **titr. stop drift 20 ul/min **titr.

t(delay) 10 s **titr.

stop time OFF s **titr.

Minimum dosing rate (0.01...999.9 uL/min)

This parameter determines the addition rate right at the start and the end of the titration, see also page 30. This parameter influences the titration speed and therefore its accuracy very strongly: A smaller min.rate results in a slower titration.

Type of stop criteria (drift, time)

Titration stops if EP is and stop drift is reached. (1...999 uL/min)

Titration stops if there is no dosing during t(delay). (0...999 s, INF)

<CLEAR> sets "INF" Switch off when the end point is reached and the set time after the last dispensing has elapsed. If "INF" is set, an inquiry regarding the stop time appears. If t(delay) is "INF"

Stop after a time (0...999 999 s, OFF)

<CLEAR> sets "OFF". Stop after the set time after the start of the titration. "OFF" means no stop, i.e. titration for an "infinitely" long time.

>titration parameters

titr.direction: auto

pause 1 0 s **titr.

start V: OFF cond.

start V 0.0 ml cond.

General titration parameters

Direction is set automatically (+, -, auto)

auto: The direction is set automatically by the Titrino

(sign [U

- EP]).

first

+: Direction of higher pH, higher voltage (more

"positive"), larger currents.

- : Direction of lower pH, lower voltage, smaller currents.

The titration direction is fixed if two EP's are set. In this case, an input for titration direction has no meaning.

Pause 1 (0...999 999 s)

Waiting time before start volume, e.g. for equilibration of the electrode after the start. The waiting time can be aborted with <QUIT>.

Type of start volume (OFF, abs., rel.)

"OFF": start volume switched off "abs.": absolute start volume in mL "rel.": relative start volume to sample size.

If "abs." is set:

Absolute start volume (0...999.99 mL)

factor 0 cond.

785 DMP Titrino

If "rel." is set:

Factor for relative start volume (0...±999 999).

Calculated as: start V in mL = factor * sample size

2.6. Parameters, key <PARAM>

dos.rate max. ml/min **titr.

pause 2 0 s **titr.

extr.time 0 s **titr.

meas.input: 1

Dosing rate for start volume (0.01...150 mL/min, max.)

<CLEAR> sets "max.". The maximum rate depends on the Exchange Unit: Exchange Unit max.

5 mL 15 mL/min 10 mL 30 mL/min 20 mL 60 mL/min 50 mL 150 mL/min

Pause 2 (0...999 999 s)

Waiting time after start volume, e.g. reaction time after dosing of a start volume. The waiting time can be aborted with <QUIT>.

Extraction time (0...999 999 s)

During this time the titration is already running. It will be not stopped (also if the EP is already reached) before the extraction time is terminated. The extraction time can be aborted with <QUIT>.

Measuring input (1, 2, diff.)

Inquiry only with measured quantities pH and U. Measuring input 1 or 2 or differential amplifier; connection of electrodes, see page 158.

I(pol) 1 uA

U(pol) 400 mV

electrode test: OFF

temperature 25.0 °C cond.

time interval 2 s cond.

With polarized electrodes, instead of the measuring input the

polarization current (-127...127 uA)

or the

polarization potential (-1270...1270 mV, in steps of 10 mV)

is inquired.

Electrode test (OFF, ON)

Test for polarized electrodes. Performed on changeover from the inactive state to a measurement. "OFF" means that the test is not performed.

Titration temperature (-170.0...500.0°C).

Temperature is measured at the start of the titration if a T sensor is connected. The value is used for temperature compensation in pH titrations.

Time interval (1...999 999 s)

Time interval for acquisition of a measured value into the measuring point list.

785 DMP Titrino

2.6 Parameters, key <PARAM>

>stop conditions

stop V: abs. **titr.

stop V 99.99 ml **titr.

factor 999999 **titr.

filling rate max. ml/min

Stop conditions for titration

If this is not "normal", i.e. after reaching the EP.

Type of stop volume (abs., rel., OFF)

"abs.": absolute stop volume in mL. "rel.": relative stop volume to sample size. "OFF": stop volume switched off. Stop volume

is not monitored.

If "abs." is set:

Absolute stop volume (0...9999.99 mL)

If "rel." is set:

Factor for relative stop volume (0...±999 999)

Calculated as: Stop V in mL = factor * sample size

Filling rate after the titration (0.01...150 mL/min, max.)

<CLEAR> sets "max.". The maximum rate depends on the Exchange Unit: Exchange Unit max.

5 mL 15 mL/min 10 mL 30 mL/min 20 mL 60 mL/min 50 mL 150 mL/min

>preselections

conditioning: OFF

display drift: ON cond.

drift corr: OFF cond.

drift value 0.0 ul/min cond.

req.ident: OFF cond.

Preselections for the sequence

Automatic conditioning of titration vessel. (ON, OFF)

If conditioning is "on", between the titrations the titration solution is constantly maintained at the (1st) end point. When conditioning is performed, the volume drift can be displayed during the conditioning:

Display of drift during conditioning (ON, OFF).

Volume drift.

Type of drift correction (auto, man. OFF)

auto: The value of the drift will be stored automatically at the start of the titration.

Value for manual drift correction (0...99.9 ul/min)

Request of identifications after start of titration (id1, id1&2, all, OFF)

After start, sample identifications can be requested automatically: Only id1, id1 & id2, all three id's or no inquiries.

785 DMP Titrino

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