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An open C4D for capillary electrophoresis
Kelliton José Mendonça Francisco and Claudimir Lucio do Lago
Department of Fundamental Chemistry, Institute of Chemistry, University of São Paulo, Brazil
Email: [email protected]
Summary
• The capacitively coupled contactless conductivity detection (C4D)
• The openC4D
• Serine Protocol
• openC4D at GitHub
• Perspectives
Conductivity, Admittance, and Impedance
𝑅 =𝑙
𝑎∙1
𝜅
𝑌 =1
𝑍
𝑌 - admittance𝐶- capacitance𝑓- frequency
𝑗 - −1
DC
AC
𝑌 =1
𝑅+ 2𝜋𝑓𝐶𝑗
𝑌 =𝑎
𝑙𝜅 + 2𝜋𝑓𝐶𝑗
𝑅 - resistance 𝜅 - conductivity𝑙 - distance between𝑎 - electrode area𝑍 - impedance
𝑌 =𝑎
𝑙𝜅
2
+ 2𝜋𝑓𝐶 2
magnitude of the admittanceLegend:
𝑓 = 1 𝑘𝐻𝑧
𝑓 > 100 𝑘𝐻𝑧
Make the connections as short as possible.
For a real BGE and frequency < 10 MHz, this capacitor is not important.
For a low output impedance oscillator, this capacitor is not important.
For frequency < 10 MHz and a well-designed ground plane, this capacitor is not important.
∆ 𝑌 ∝ ∆𝜅
Keep everything steady!• Frequency and amplitude• Temperature• Positioning
The admittance detector becomes a conductivity detector.
Anal. Chem. 70 (1998) 4339.
sig
na
l vo
lta
ge
time
sig
na
l vo
lta
ge
time
sig
na
l vo
lta
ge
time
co
nd
uctivity
time
sig
na
l vo
lta
ge
time
∆𝜅
∆ 𝑌
∆ 𝑌 ∝ ∆𝜅
openC4D landmarks
• 1998 – The oscillometric detector
• 2002 – The first revision
• 2005 – The tutorial about C4D
• 2009 – The openC4D is published
• 2010 – openC4D.com is launched
• 2012 – The project is moved to https://sites.google.com/site/openc4d/home
• 2016 – openC4D version 2
• 2018 – The project is moved to https://github.com/claudimirlago/openC4D
C4D: The Second Generation
silica capillary
electrodes18 mm
J. Chromatogr. A 942 (2002) 249.
function generator
power source, baseline compensation, and analog output
Electroanalysis 17 (2005) 1198.
Electroanalysis 17 (2005) 1207.
Which frequency?
Bad contact
Electrodes
What we've learned
The steadiness of the electrode
0.00 0.02 0.04 0.06 0.08 0.10 0.120.00
0.02
0.04
0.06
0.08
0.10
0.12
0.14
0.16
ca
pa
cita
nce
/
p
F
capillary position / mm
A 360-μm o.d. silica capillary inside a electrode made of a 600-μm i.d. metal needle:
The capacitance is 36% higher!
The electrode should be as tight as possible, and the capillary should not be able to shake.
IC 6
Vref
Vss
+Vin
-Vin
Vdd
SCK
CS
SDOIC 5IC 4 D1
R9
C16R10 R11C11
C20 C21
C12
C18
C19
C17
+5V
+5V
C15
R21
R22
R20
R15 R18 R19
R17
R16
R13
R14
R12
GND
SDO
CS
SCK
C13Electrodes
IC 1-AIC 2
+5V
R5
GND
+9V
IC 1-B
C1
R4C3
C2
R6
R3
R2
R1
+2.5V
+2.5V
IC 3OutIn
GND
+2.5V
C4C5 C6
C8
C9
C10L1
L2
R7
R8
+5V
+5V
+5V
C7 C14
GB PB
Electrophoresis 30 (2009) 3458.
22-bit analog-to-digital
converter
serial
interface
(SPI)
triangular-wave oscillator
low-pass filter
9-V
power
supply
openC4D
sig
na
l vo
lta
ge
time
sig
na
l vo
lta
ge
time
sig
na
l vo
lta
ge
time
sig
na
l vo
lta
ge
time
*
*
* *
* This OpAmp may be different.
polyethylene
insulator
openC4D
copper
ground
plane
generator
boardshield
pickup
boardshieldpolyethylene
insulator
silica capillarypower and
interface cable
openC4D
2 3 4 5 60
1 000 000
2 000 000
3 000 000
4 000 000
time / min
2 3 4 5 6
2 540 000
2 560 000
2 580 000
time / min
2 3 42 578 000
2 579 000
2 580 000
2 581 000
time / min
Sample:
K+, Ba2+, Ca2+, Na+, Mg2+, and Li+
16 µmol/L
2 500 000 3 000 000 3 500 000
0
1
2
3
4
5
100 m
75 m20 m
50 m / m
S c
m-1
ADC reading
0.2 ~ 1.2 mS cm-1
The most common BGEs used in CE
𝜅 𝑟 =𝑟 + 𝑎
𝑏0 + 𝑏1 𝑟 + 𝑎 + 𝑏2 𝑟 + 𝑎 2
𝑎, 𝑏0, 𝑏1, 𝑏2 are obtained by non-linear fitting.
FR04
35 µm copper layer
post-drilled hole
capillary
stainless steel needle
weld
a – the new C4D pickup boardb – the old C4D pickup boardc – silica capillarye – gold-plated viad – stainless steel electrode
gold-plated vias as electrodes
PCB 1.6 mm2.0 mm
Electrophoresis 37 (2016) 1718.
via
A brief history of the openC4D project
C4D• 1998 – The oscillometric detector
• 2002 – The first revision
• 2005 – The tutorial about C4D
• 2009 – The openC4D is published
• 2010 – openC4D.com is launched
• 2012 – The project is moved to https://sites.google.com/site/openc4d/home
• 2016 – openC4D version 2
• 2018 – The project is moved to https://github.com/claudimir-lago/openC4D
CE-C4D instruments
• 1995 – Zé 1
• 1998 – Zé 2
• 2004 – Homer (with 2 C4Ds)
• 2005 – Acquaplay
• 2007 – Sponge Bob (with 8 C4Ds)
• 2009 – Darth Vader (with 2 C4Ds)
Luke, Michael Jackson, Coyote, CEC4D
• 2011 – LOAR3
a b e f c d
g h
j
i
a
b
c
f
g
hh
e
i
jk
d
electrophoresis reservoir electrolysis reservoir
Homer
• Electrolysis separated
• Two C4D
• Double thermal marker
R. M. Saito et al., “Ionic Mobility of the Solvated
Proton and Acid-Base Titration in a Four-Compartment
Capillary Electrophoresis System”, Anal. Methods 2
(2010) 164.
Darth Vader
1st C4D2nd C4D
injection side
LOAR3
Electrophoresis 33 (2012) 2650.
Electrophoresis 37 (2016) 1718.
Talanta 185 (2018) 37.
CE-(C4D)2-ESI-MS/MS
Serine Protocol
• Serine Protocol is a light communication protocol for small microcontrollers
• Communication channels: UART, RS232, I2C, USB, etc.
• Some headlines:– The exchanged messages should be easily and
unequivocally interpreted by a simple microcontroller.
– The messages should resist, as originally generated, to all hardware and software protocols used over the network.
– The messages should be as readable and writable as possible by humans.
• https://github.com/claudimir-lago/Serine-Protocol
Darth Vader
injectordetector
HV power source
thermostat
manager master
virtual device
computer
ATmega328ATmega168
Teensy 2.0
processor
Darth Vader
injectordetector
HV power source
thermostat
manager master
virtual device
computer
ATmega328ATmega168
Teensy 2.0
processor
USBI2C
Darth Vader
injector (i)
detector(d)
HV(h)
thermostat(t)
manager(g)
master(m)
virtual device
processor
USBI2C
dispatcher
Darth Vader
injector (i)
detector(d)
HV(h)
thermostat(t)
manager(g)
master(m)
USBI2C
dmG;
“Detector, Master is requesting an ADC reading.”
Darth Vader
injector (i)
detector(d)
HV(h)
thermostat(t)
manager(g)
master(m)
USBI2C
“Master, Detector says t = 31.063 s, C4D0 = 2,153,383, C4D1 = 2,271,005.”
mdgA003106321533832271005;
https://github.com/claudimir-lago/openC4D
USB and I2C interface
The Java frontend
The Java frontend
Perspectives
• New versions of openC4D– Microchip
– Adjustable frequency
– Even smaller and cheaper
– New electronics
• New software– New stuff in Java and Python
– Coupling to Agilent, Sciex…
– Coupling to OpenChrom
• New version of a CE-C4D– 3D-based version for 2019 (?)
– GitHub
Acknowledgements
Institute of ChemistryUniversity of São Paulo
Carlos A. Neves, Carlos Garcia, Eric T. da Costa, Fernando S. Lopes, Guilherme M. Hotta, Ivano G. R. Gutz, José A. Fracassi da Silva, José G. A. Brito-Neto, Kelliton Francisco, Lucas Blanes, Marcelo F. Barros, Norberto A. Guzman, …
Email: [email protected]