S1
Supporting Information for:
1
2
Electrochemical Transformation of Trace Organic
3
Contaminants in Latrine Wastewater
4
5
6
7
8
Justin T. Jasper,
Oliver S. Shafaat, Michael R. Hoffmann
9
10
42 pages
11
13 figures
12
2 tables
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
S2
Reaction Rate Constants for FAC and NH
2
Cl.
Test compound (100 nM) removal was
35
followed in buffered solutions (pH 8.7; 20 mM
borate) with excess FAC (0.03-5.0 mM) or
36
NH
2
Cl (0.3-3.0 mM). NH
2
Cl solutions were prepared by adding stock solution
s of FAC
37
dropwise to excess NH
4
Cl (1.2:1 NH
4
Cl:HOCl). Samples were quenched (45 mM Na
2
S
2
O3)
38
prior to analysis. Solution pH values and total ch
lorine concentrations did not change
39
significantly over the course of the experiments.
Rate constants were calculated based on first-
40
order removal kinetics of the test compounds using
measured steady-state total chlorine
41
concentrations. For ciprofloxacin, rate constants
were measured at multiple NH
2
Cl and FAC
42
concentrations to verify that observed ciprofloxaci
n transformation rates were not dependent on
43
oxidant concentrations, but rather represented deca
y of the rapidly formed N-chlorinated
44
ciprofloxacin intermediate as previously reported.
1
First-order ciprofloxacin decay rates were
45
therefore reported.
46
S3
Reaction Rate Constants for the Chlorine Radical An
ion, ·Cl
2
-
.
Second-order rate
47
constants for the reaction of test compounds with t
he dichlorine radical anion (4Cl
2
-
) were
48
measured by nanosecond transient absorption laser f
lash photolysis of solutions containing
49
Na
2
S
2
O
8
(25 mM), NaCl (100 mM), and test compounds (0-100
μM). Excitation at 266 nm (8 ns
50
FWHM, 10 Hz repetition rate) produced 4SO
4
-
that rapidly reacted with Cl
-
to produce 4Cl
2
-
51
(~1 ;M). Solution pH values ranged from 5.5 to 6.0.
The decay of 4Cl
2
-
was monitored at 340
52
nm over 10 ms, and data was averaged over 10 shots.
4Cl
2
-
decay was log-normalized and
53
plotted versus test compound concentrations to dete
rmine second-order rate constants. 4Cl
2
-
54
decay was log-normalized and fit according to:
55
A
340
= fe
+ h
(S1)
56
where A(340) is the absorbance at 340 nm, f is the
initial absorbance, g is the decay rate, and h is
57
an offset due to a longer lived species formed afte
r 4Cl
2
-
decay.
2
4Cl
2
-
decay rates were plotted
58
versus test compound concentrations to determine se
cond-order rate constants:
59
g = k
,∙
[cmpd] + b
(S2)
60
where
k
,∙
is the second-order rate constant for the reaction
of a test compound with 4Cl
2
-
,
61
[cmpd] is the test compound concentration, and b is
the y-intercept that represents loss of 4Cl
2
-
62
due to other reactions (e.g., quenching by H
2
O). Under these conditions 4Cl is predicted to
63
contribute less than 5% to measured second-order ra
te constants greater than 10
7
M
-1
s
-1
.
64
S4
Chronoamperometric Experiments.
Chronoamperometric experiments were
65
performed to verify direct electron transfer for co
mpounds that underwent transformation in the
66
absence of Cl
-
and were soluble enough dissolve rapidly (i.e., ra
nitidine and cimetidine). About
67
5 mM of a solid test compound was added to a soluti
on of Na
2
SO
4
(20 mM) undergoing
68
potentiostatic electrolysis (3.5 V cathode vs. anod
e), and the current response was observed. A
69
spike in the current upon test compound addition im
plied that the compound could be oxidized
70
directly at the anode.
3,4
The possibility that current increased due to a c
hange in electrolyte
71
strength was eliminated based on the current’s retu
rn to near baseline values after test compound
72
oxidation was complete.
73
S5
Transformation Product Identification.
Test compound transformation product
74
formulae were calculated based on accurate masses a
nd typically had a mass error of less than 2
75
mDa (Table SI 2). Transformation product halogen c
ontent was confirmed by characteristic
76
isotopic patterns using the m/z+2, m/z+4, etc. peak
s. Isotopic peak ratios were typically within
77
10% of theoretical values for the proposed formulae
. Transformation product structures were
78
proposed based on the literature when possible (see
bold references in Table SI 2), by comparing
79
exact mass values and fragment ions. In other case
s, structures were proposed simply based on
80
determined formulae. In these cases, the exact pos
ition of certain functional groups (e.g.,
81
hydroxyl and chlorine) could not be determined. Wh
en possible, proposed structures were
82
verified with authentic standards, as specified in
Table SI 2.
83
S6
Analytical Methods.
Dissolved organic carbon and dissolved inorganic ca
rbon were
84
measured by persulfate digestion using an Aurora TO
C analyzer.
5
NO
3
-
, Cl
-
, PO
4
3-
, SO
4
2-
, and
85
NH
4
+
were analyzed by ion chromatography (Dionex ICS 20
00; AS19G anions, CS12A
86
cations).
5
87
Test compounds were separated by an Acquity BEH C18
column (2.1x50 mm; 1.7 ;m
88
particles), eluted at 0.5 mL min
-1
using acetonitrile and water with 0.1% formic acid
and 1%
89
acetonitrile. The following gradient was used: 0 m
in, 5% acetonitrile; 0.2 min, 5% acetonitrile;
90
3.2 min, 95% acetonitrile; 3.5 min, 95% acetonitril
e; 3.6 min, 5% acetonitrile; 5 min, 5%
91
acetonitrile. Column temperature was held at 35 °C
. pCBA were detected by UV absorbance
92
(270 nm). Trace organic compounds were detected by
positive electrospray ionization (ESI+) in
93
resolution mode with a capillary voltage of 0.2 kV,
a cone voltage of 50 V, and a source offset of
94
80 V. Source temperature was 120 °C and desolvatio
n temperature was 400 °C. Cone gas was
95
40 L/h and desolvation gas was 800 L/h. Scan time
was 0.3 s in continuum mode. A collision
96
energy of 1.0 eV was used. A second acquisition ch
annel scanned collision energy from 0-30 eV
97
for fragment identification. Accurate mass values
were corrected by the software using a leucine
98
lock-mass.
99
100
S7
Calculation of ·Cl
2
-
Reaction with Propranolol.
The fraction of 4Cl
2
-
reacting with
101
propranolol (
F
∙#$
,%&'%&()'$'$
in latrine wastewater (100 mg L
-1
TOC) was calculated using 4Cl
2
-
102
measured second-order reaction rate constants with
propranolol (
k
∙#$
,%&'%&()'$'$
and TOC
103
(
k
∙#$
,*+#
to be:
104
F
∙#$
,%&'%&()'$'$
=
k
∙#$
,%&'%&()'$'$
[propranolol]
k
∙#$
,%&'%&()'$'$
[propranolol] + k
∙#$
,*+#
[TOC]
=
1.9x10
8
M
;
s
;
∗ 1x10
>
M
1.9x10
8
M
;
s
;
∗ 1x10
>
M + 1.9x10
?
mg L
;
;
s
;
∗ 100 mg L
;
= 0.0099
105
S8
Test Compound Transformation Products.
Carbamazepine’s predominant
106
transformation products were confirmed to be acridi
ne, hydroxyacridine, and acridine-9-
107
carboxaldehyde (Table SI 2; Figures SI 12a and 13),
based on authentic standards. No
108
chlorinated transformation products were identified
during latrine wastewater or buffered Cl
-
109
solution electrolysis. Transformation products wer
e similar to those previously observed during
110
oxidation and chlorination of carbamazepine.
6–10
111
Metoprolol and propranolol were predominantly trans
formed to chlorinated products that
112
underwent further transformation to form products n
ot detected by LCMS (Figures SI 12b,c and
113
9). Hydroxylated and multiply halogenated transfor
mation products were also identified (Table
114
SI 2). Most metoprolol transformation products wer
e identified previously during reverse
115
osmosis retentate electrolysis
11
or other treatment processes.
12,13
Some propranolol
116
transformation products observed in this study have
been reported previously,
14–17
but others
117
have not, including the predominant chlorinated pro
duct (m/z 294.1276 amu; m/z+2 amu
118
observed at ~33%).
119
Identified ciprofloxacin transformation products we
re typically transformed at the
120
piperazine group rather than chlorinated (Figures S
I 12d, 13), as previously observed during
121
ciprofloxacin reaction with FAC and ClO
2
.
1,18
122
Trimethoprim was transformed into a variety of hydr
oxylated and chlorinated
123
transformation products, some of which have been id
entified during treatment using ferrate,
19
124
activated sludge,
20
and FAC.
21
125
Only a few significant acetaminophen and cimetidine
transformation products were
126
observed (Figures SI 12f and 13), all of which are
produced by reaction with FAC.
22–24
As with
127
S9
trimethoprim, different acetaminophen transformatio
n products were observed in the absence of
128
NH
4
+
, including formation of dichlorinated acetaminophe
n.
129
Ranitidine transformation products were chlorinated
, demethylated, and oxidized, with
130
the latter two transformations likely occurring at
the furan group.
25
Although a few of the
131
identified products have previously been observed d
uring chloramination of ranitidine,
25
further
132
work is needed to confirm transformation product st
ructures (Table SI 2). Many transformation
133
products observed during latrine wastewater electro
lysis were not observed during electrolysis of
134
buffered Cl
-
solutions (Figures SI 12g and 13; see main text).
135
S10
Table SI 1. Comparison of Measured Test Compound R
eaction rates with HOCl and NH
2
Cl to Literature Values.
136
137
138
139
140
141
142
143
144
145
146
147
148
149
a
Measured or calculated at pH 8.7.
b
FAC=[HOCl]+[OCl
-
].
c
n.a.: not available.
d
Calculated at pH 1.3 based on reported acid cataly
zed reactions with HOCl.
150
e
First-order transformation rate is reported due to
rapid quenching of the N-chlorinated ciprofloxacin
intermediate by Na
2
S
2
O
3
.
f
Reaction rate between HOCl
151
and the predominant fully protonated form of ciprof
loxacin at pH 1.3.
g
Estimated based on complete removal within 10 s.
152
compound
property
A
BCD
(M
-
1
s
-
1
)
a
,
b
measured literature
A
E
F
G
DH
(M
-
1
s
-
1
)
a
measured literature
A
D
H
G
(M
-
1
s
-
1
)
measured literature
carbamazepine
8.9(±1.0)x10
-
2
2.7×10
-
2 (
10
)
<3x10
-
3
n.a.
c
~1x10
5
6.7×10
4
(
10
)
metoprolol
1.9(±1.0)x10
-
2
2×10
-
2 (
16
)
<4x10
-
3
<0.1
(
16
)
~4x10
3
0.6-1.4×10
3
(
16,26
)
d
propranolol
0.27(±0.02)
0.3
(
16
)
<6x10
-
3
<0.1
(
16
)
~2x10
5
3.3×10
5
(
16
)
d
ciprofloxacin
5.6(±0.4)×10
-4
s
-1
e
7×10
-
4
s
-
1
(
1
)
e
9×10
-
4
s
-
1
e
7×10
-
4
s
-
1
(
1
)
e
~6x10
3
4.3×10
3 (
1
)
f
trimethoprim
6.7(±0.2)
8
(
21
)
<1x10
-
3
negligible
(
21
)
~3x10
6
2x10
5
-2×10
6 (
21
)
acetaminophen
7.0(±0.4)×10
2
0.7-1.4×10
2
(
16,23,27
)
0.9(±0.1)
1.1x10
-
2 (
16
)
~3x10
4
n.a.
c
ranitidine
>8×10
3
n.a.
c
11(±1)
12
(
25
)
~8x10
4
n.a.
c
cimetidine
>6.5×10
3
>1×10
3
(
24
)
g
47(±1)
48
(
24
)
~4x10
6
n.a.
c
S11
Table SI 2. Test Compound Transformation Products
(TPs).
153
Parent
Test
compound
TP m/z
a
(ID)
Major
Fragment
ions m/z
RT
(min)
Calculated
Formula
Mass
Error
(mDa)
Proposed Molecular Ion Structure
b
Refs.
c
Carbamazepine
224.0715
(Cbz 224)
164.920,
167.073,
180.081,
196.076
0.58
C
14
H
10
NO
2
0.3
6,7
180.0812
d
(Cbz 180)
152.0621 1.17
C
13
H
10
N
0.3
6,8
275.0800
(Cbz 275)
180.0800,
210.0919,
236.0712,
253.0976
1.58
C
14
H
13
NO
5
0.6
253.0974
d
(Cbz 253)
1.59
C
15
H
13
N
2
O
2
0.3
6,10
196.0759
e
(Cbz 196)
167.073,
180.0810
1.65
C
13
H
10
NO
0.3
6
–
9
208.0761
d
(Cbz 208)
152.062,
180.082,
196.0760
2.07
C
14
H
10
NO
0.1
8,9
Metoprolol
226.1436
(Met 226)
116.1067,
121.0636,
149.0583
0.82
C
12
H
20
NO
3
0.7
11,13
284.1853
(Met 284)
116.1063,
226.1420,
268.141
0.85
C
15
H
26
NO
4
0.9
11,13
254.1393
(Met 254)
105.0692,
151.0381,
177.0540,
212.0911,
236.1275
0.93
C
13
H
20
NO
4
<0.1
O
NH
O
H
O
OH
238.1439
(Met 238)
105.0696,
133.0642,
149.0590
161.0589,
196.0962
1.04
C
13
H
20
NO
3
0.4
O
NH
O
H
O
12
282.1706
(Met 282)
105.0696,
133.0642,
149.0590
161.0589,
196.0962
1.05
C
15
H
24
NO
4
<0.1
11
N
H
O
O
N
N
N
H
2
O
O
N
OH
N
H
O
N
O
O
NH
2
O
H
O
O
NH
O
H
O
OH
O
NH
O
O
O
H
S12
Parent
Test
compound
TP m/z
a
(ID)
Major
Fragment
ions m/z
RT
(min)
Calculated
Formula
Mass
Error
(mDa)
Proposed Molecular Ion Structure
b
Refs.
c
Metoprolol
(cont.)
302.1515
(Met 302)
98.0963,
116.1066,
167.0249,
193.0407,
260.1044,
284.1411
1.51
C
15
H
25
NO
3
Cl
0.8
11
336.1121
(Met 336)
72.0817,
98.0965,
116.1064,
276.0549,
294.0649,
318.102
1.62
C
15
H
24
NO
3
Cl
2
1.2
11
Propranolol
276.1599
(Pro 276)
116.1074 1.0-
1.3
f
C
16
H
22
NO
3
<0.1
O
NH
O
H
OH
17
292.1545
(Pro 292)
116.107,
123.092,
150.128,
274.144,
272.128,
1.29
C
16
H
22
NO
4
0.4
15
218.1180
(Pro 218)
116.1071,
183.0804
1.45
C
13
H
16
NO
2
0.1
16
310.1210
(Pro 310)
72.0816,
116.1071,
135.1038,
260.1653
1.53
C
16
H
21
NO
3
Cl
<0.1
294.1276
(Pro 294)
150.128,
260.165
1.85
C
16
H
21
NO
2
Cl
1.5
338.0739
(Pro 338)
116.1070,
182.0725,
217.0417
1.94
C
16
H
21
NO
2
Br
1.7
328.0868
(Pro 328)
72.0819,
116.1068,
219.1751
1.98
C
16
H
20
NO
2
Cl
2
0.3
O
NH
O
H
O
Cl
O
NH
O
H
O
Cl
Cl
O
NH
O
H
OH
OH
O
NH
2
O
H
O
NH
O
H
Cl
OH
O
NH
O
H
Cl
O
NH
O
H
Br
O
NH
O
H
Cl
Cl
S13
Parent
Test
compound
TP m/z
a
(ID)
Major
Fragment
ions m/z
RT
(min)
Calculated
Formula
Mass
Error
(mDa)
Proposed Molecular Ion Structure
b
Refs.
c
Ciprofloxacin
306.1246
(Cfx 306)
217.0404,
268.1077,
288.1142
1.09
C
15
H
17
N
3
O
3
F
0.8
1,18
366.1012
(Cfx 366)
225.0213,
245.1079,
279.0695,
322.1108
1.22 C
17
H
18
N
3
O
3
FCl
0.9
1
362.1141
(Cfx 362)
344.1037 1.29
C
17
H
17
N
3
O
5
F
1.1
18
291.0773
(Cfx 291)
245.0709,
273.0671
1.42
C
14
H
12
N
2
O
4
F
0.8
263.0828
(Cfx 263)
204.032,
245.0724
1.49
C
13
H
12
N
2
O
3
F
0.4
18
298.0287
(Cfx 298)
280.0184 1.63
C
13
H
10
NO
4
FCl
0.5
1
289.0981
(Cfx 289)
271.0876 1.74
C
15
H
14
N
2
O
3
F
0.8
Trimethoprim
Trimethoprim
342.1327
(Tmp 342)
273.0978,
307.1397
0.98
C
14
H
21
N
5
O
3
Cl
0.6
307.1391
(Tmp 307)
209.1644,
212.0686,
240.0634,
258.0742,
273.0975
0.98
C
14
H
19
N
4
O
4
1.5
19
322.1508
(Tmp 322)
1.04
C
14
H
20
N
5
O
4
0.7
325.1499
(Tmp 325a)
173.0813,
219.0872,
233.1043,
293.1229
1.05
C
14
H
21
N
4
O
5
1.3
20
343.1164
(Tmp 343)
181.0852 1.08
C
14
H
20
N
4
O
4
Cl
0.9
N
NH
NH
2
O
OH
O
F
N
N
N
H
O
OH
O
F
Cl
N
N
N
H
O
OH
O
F
O
O
N
NH
O
OH
O
F
O
N
N
H
2
O
OH
O
F
N
N
C
H
2
O
OH
O
F
H
N
N
N
H
2
NH
2
O
O
O
OH
N
N
H
N
H
2
NH
2
O
O
O
O
OH
N
N
H
N
H
2
NH
2
O
O
O
O
Cl
S14
Parent
Test
compound
TP m/z
a
(ID)
Major
Fragment
ions m/z
RT
(min)
Calculated
Formula
Mass
Error
(mDa)
Proposed Molecular Ion Structure
b
Refs.
c
(cont.)
359.1125
(Tmp 359a)
215.0465,
240.0414,
236.0905
1.19
C
14
H
20
N
4
O
5
Cl
0.3
323.1345
(Tmp 323)
1.26
C
14
H
19
N
4
O
5
1.0
377.0773
(Tmp 377)
217.0435,
236.0913,
255.0416,
257.0388,
314.0898
1.26
C
14
H
19
N
4
O
4
Cl
2
1.0
21
393.0719
(Tmp 393)
100.0503,
126.0529,
249.0075,
270.0524
1.32
C
14
H
19
N
4
O
5
Cl
2
1.4
N
N
H
N
H
2
NH
2
O
O
O
O
OH
2 Cl
325.1059
(Tmp 325b)
145.0267,
271.0918,
249.008
1.39
C
14
H
18
N
4
O
3
Cl
0.8
21
411.0391
(Tmp 411)
249.0080,
366.0616
1.39
C
14
H
18
N
4
O
4
Cl
3
0.3
21
369.0558
(Tmp 369)
255.0886,
273.092,
325.1078,
339.0081
1.42
C
14
H
18
N
4
O
3
Br
0.4
359.0672
(Tmp 359b)
181.0854,
199.097,
289.0480,
298.0371,
329.0196
1.55
C
14
H
17
N
4
O
3
Cl
2
0.6
21
403.0174
(Tmp 403)
140.0686,
180.8981,
257.1478,
359.0669
1.58 C
14
H
17
N
4
O
3
BrCl
0.1
Acetaminophen
186.0312
(Ace 186)
109.0515,
144.0201,
155.9838
1.17
C
8
H
9
NO
2
Cl
1.0
O
NH
O
H
Cl
22,23
219.9919
(Ace 219)
143.0123,
177.9810
1.42
C
8
H
8
NO
2
Cl
2
1.3
O
NH
O
H
Cl
Cl
22,23
Ranitidine
338.0561
(Rnt 338)
109.0278,
186.0565,
202.9997,
214.0240,
292.0612
0.63 C
11
H
17
N
3
O
5
SCl
1.6
NH
NH
S
O
H
O
N
+
O
-
O
Cl, OH
25
N
N
H
N
H
2
NH
2
O
O
O
O
OH
Cl
N
N
N
H
2
NH
2
O
O
O
OH
OH
N
N
H
N
H
2
NH
2
O
O
O
O
Cl
Cl
N
N
N
H
2
NH
2
O
O
O
Cl
N
N
H
N
H
2
NH
2
O
O
O
O
Cl
2 Cl
N
N
N
H
2
NH
2
O
O
O
Br
N
N
N
H
2
NH
2
O
O
O
2 Cl
N
N
N
H
2
NH
2
O
O
O
Cl, Br
S15
Parent
Test
compound
TP m/z
a
(ID)
Major
Fragment
ions m/z
RT
(min)
Calculated
Formula
Mass
Error
(mDa)
Proposed Molecular Ion Structure
b
Refs.
c
336.0419
(Rnt 336)
125.0600,
181.0201,
203.0023,
214.0259,
290.0497
0.66 C
11
H
15
N
3
O
5
SCl
0.2
NH
NH
S
O
N
+
O
-
O
O
Cl, OH
364.1194
(Rnt 364)
109.0278,
163.0854,
189.1012,
258.0579
0.76 C
13
H
23
N
5
O
3
SCl
1.6
NH
NH
S
N
+
O
N
+
O
-
O
N
H
2
Cl
25
335.0928
(Rnt 335)
0.85 C
12
H
20
N
4
O
3
SCl
1.6
NH
NH
S
NH
O
N
+
O
-
O
Cl
349.1083
(Rnt 349)
124.075,
132.0438,
164.0159,
210.0092,
223.0893
0.88 C
13
H
22
N
4
O
3
SCl
1.8
NH
NH
S
N
O
N
+
O
-
O
Cl
25
270.0903
(Rnt 270)
97.0759,
165.1013,
191.1167,
224.0971
1.02
C
11
H
16
N
3
O
3
S
0.9
322.061
(Rnt 322)
165.0236,
240.1152
1.08 C
11
H
17
N
3
O
4
SCl
1.8
NH
NH
S
O
H
O
N
+
O
-
O
Cl
320.0459
(Rnt 320)
109.028,
165.0238,
208.0392,
234.0191,
274.0529
1.12 C
11
H
15
N
3
O
4
SCl
1.3
NH
NH
S
O
O
N
+
O
-
O
Cl
294.12575
(Rnt 294)
109.0294,
150.1284,
177.0489,
188.0054,
275.053
1.85
C
13
H
25
NO
2
SCl
3.7
Cimetidine
117.0210
(Cmt 117)
90.0104
0.53
C
4
H
6
N
2
Cl
1.0
Cl
N
N
H
24
189.0435
(Cmt 189)
82.0403
1.06
C
5
H
9
N
4
O
2
S
1.1
S N
O
O
N
NH
N
24
a
Compounds with m/z ratios in bold exhibited isotop
ic patterns consistent with the halogen atoms speci
fied in the
154
calculated formula (i.e., m/z+2, m/z+4, etc. peaks)
.
b
Structure of unprotonated TP. Structure based on
calculated
155
formula, fragments, and literature.
c
References in bold proposed compound structure show
n. References in italics
156
observed similar major fragment ions.
d
TP identity confirmed based on authentic standard
retention time and mass
157
spectrum.
e
Authentic acridone standard (ketone product shown)
retention time differed by ~0.03 min and had
158
different fragmentation pattern, suggesting that hy
droxyacridone was formed during electrolysis.
f
Multiple peaks
159
observed.
160
161
S16
162
Figure SI 1. Schematic of electrochemical reactor
used in this study.
163
164
S17
0.0E+00
2.5E-04
5.0E-04
7.5E-04
1.0E-03
0
0.25
0.5
k' (s
-1
)
[NH
2
Cl] (mM)
0.0E+00
2.5E-04
5.0E-04
7.5E-04
1.0E-03
0
0.5
1
1.5
[FAC] (mM)
Figure SI 2. Measured first-order rate constants f
or the reaction of ciprofloxacin with various
165
concentrations of NH
2
Cl and FAC. Error bars represent ± one standard de
viation.
166
S18
167
Figure SI 3. Pseudo-first order test compound elec
trolysis rates (k; top) and rates normalized for
168
charge (k′; bottom). Solutions were electrolyzed a
t an applied potential of 3.5 V in 0-75 mM
169
NaCl solution buffered at pH 8.7 (20 mM borate). A
verage current densities: 0 mM, 0.6 A L
-1
;
170
15 mM, 0.7 A L
-1
; 30 mM, 0.9 A L
-1
; 75 mM, 1.3 A L
-1
. FAC production rates: 15 mM,
171
0.9 μM s
-1
; 30 mM, 1.6 μM s
-1
; 75 mM, 3 μM s
-1
. Error bars represent ± one standard deviation.
172
173