Sensing Application — Diazo-reaction based dual-mode colorimetric-electrochemical sensing of nitrite in pickled food

6 measurement groups · 35 results

Reported values remain attached to the sample, method, conditions, extraction quality and source location that produced them.

UV-vis optimisation of colorimetric sensing conditions

UV-visible and optical absorption spectroscopy

Cu-MOFs/EGP · Electrode

Optimised TMB concentration, Cu-MOFs/EGP area, incubation time, pH, temperature and diazotization time using Fig. S1.

Context: Composite sensing platform.
Measurement source: 2 · Supporting information · Fig. S1

Property	Reported value	Normalised value	Uncertainty	Origin and quality	Source
Optimal Cu-MOFs/EGP geometric areaMarked as a best value within this paper	0.75 cm2	—	—	Text Exact Reported	4 · 3.2 Colorimetric sensing performance study · Fig. S1B
Optimal diazotization timeMarked as a best value within this paper	8 min	0.1333333333 h	—	Text Exact Reported	4 · 3.2 Colorimetric sensing performance study · Fig. S1F
Optimal TMB incubation timeMarked as a best value within this paper	15 min	0.25 h	—	Text Exact Reported	4 · 3.2 Colorimetric sensing performance study · Fig. S1C
Optimal pHMarked as a best value within this paper	pH 3.5	—	—	Text Exact Reported	4 · 3.2 Colorimetric sensing performance study · Fig. S1D
Optimal reaction temperatureMarked as a best value within this paper	37 deg C	310.15 K	—	Text Exact Reported	4 · 3.2 Colorimetric sensing performance study · Fig. S1E
Optimal TMB concentrationMarked as a best value within this paper	1.0 mM	0.001 mol L-1	—	Text Exact Reported	4 · 3.2 Colorimetric sensing performance study · Fig. S1A

Ratiometric colorimetric nitrite sensing by UV-vis absorbance ratio A445/A652

UV-visible and optical absorption spectroscopy

Cu-MOFs/EGP · Electrode

Cu-MOFs/EGP-TMB system with nitrite addition; TMB oxidation followed by diazotization at room temperature for 8 min.

Geometry: 0.75 cm2 optimal Cu-MOFs/EGP geometric area
Context: Composite sensing platform.
Measurement source: 4-5 · 3.2 and 3.4 · Fig. 5A-B

Property	Reported value	Normalised value	Uncertainty	Origin and quality	Source
Colorimetric linear range lower bound	1.2 x 10-5 mol L-1	12 umol L-1	—	Text Exact Reported	5 · 3.4 The analytical performances of the dual-mode sensor · Fig. 5B
Colorimetric linear range upper bound	3.0 x 10-4 mol L-1	300 umol L-1	—	Text Exact Reported	5 · 3.4 The analytical performances of the dual-mode sensor · Fig. 5B
Colorimetric nitrite LOD	8.5 x 10-6 mol L-1	8.5 umol L-1	S/N = 3	Text Exact Reported	5 · 3.4 The analytical performances of the dual-mode sensor · Fig. 5B
Colorimetric calibration R2	R2 = 0.991	—	—	Text Exact Reported	5 · 3.4 The analytical performances of the dual-mode sensor · Fig. 5B
Colorimetric calibration slope	A445/A652 = 0.60 log cNO2- - 0.40	—	—	Text Exact Reported	5 · 3.4 The analytical performances of the dual-mode sensor · Fig. 5B
New absorbance peak after nitrite addition	445 nm	—	—	Text Exact Reported	4 · 3.2 Colorimetric sensing performance study · Fig. 3C

UV-vis oxidase-like activity assay with TMB

UV-visible and optical absorption spectroscopy

Cu-MOFs/EGP · Electrode

0.5 cm x 1.5 cm Cu-MOFs/EGP incubated at 37 deg C in 0.1 M acetate buffer, pH 3.5, with 1.0 mM TMB for 15 min; absorbance at 652 nm recorded.

Temperature: 310
Atmosphere: air unless otherwise stated; N2-saturated buffer used as comparison
Geometry: 0.5 cm x 1.5 cm Cu-MOFs/EGP area
Context: Composite compared with EGP control.
Measurement source: 3-4 · 2.4 Oxidase-like activity of Cu-MOFs/EGP; 3.2 Colorimetric sensing performance study · Fig. 3A-B

Property	Reported value	Normalised value	Uncertainty	Origin and quality	Source
oxTMB absorption peak after Cu-MOFs/EGP incubation	652 nm	—	—	Text Exact Reported	4 · 3.2 Colorimetric sensing performance study · Fig. 3A
EGP control oxidase-like activity toward TMB	no obvious changes in color and UV-vis spectrum	—	—	Text Qualitative	4 · 3.2 Colorimetric sensing performance study · Fig. 3A

Colorimetric nitrite recovery in real food samples

Pickled-food nitrite test system using Cu-MOFs/EGP · Unknown

Pretreated food samples analysed by colorimetric mode with standard additions of 0, 25 and 50 umol L-1 nitrite.

Geometry: Cu-MOFs/EGP colorimetric sensor.
Context: Application test of composite sensor.
Measurement source: 6 · 3.5 Analysis of real samples · Table 2

Property	Reported value	Normalised value	Uncertainty	Origin and quality	Source
Cantonese sausage found nitrite by colorimetric mode, added 0 umol L-1	ND	—	—	Table Qualitative	6 · Table 2 · Table 2
Cantonese sausage found nitrite by colorimetric mode, added 25 umol L-1	24.64 umol L-1	0.000024639999999999998 mol L-1	RSD 1.3%	Table Exact Reported	6 · Table 2 · Table 2
Cantonese sausage found nitrite by colorimetric mode, added 50 umol L-1	49.17 umol L-1	0.00004917 mol L-1	RSD 1.0%	Table Exact Reported	6 · Table 2 · Table 2
Salted duck eggs found nitrite by colorimetric mode, added 0 umol L-1	ND	—	—	Table Qualitative	6 · Table 2 · Table 2
Salted duck eggs found nitrite by colorimetric mode, added 25 umol L-1	25.96 umol L-1	0.00002596 mol L-1	RSD 0.31%	Table Exact Reported	6 · Table 2 · Table 2
Salted duck eggs found nitrite by colorimetric mode, added 50 umol L-1	49.20 umol L-1	0.0000492 mol L-1	RSD 0.92%	Table Exact Reported	6 · Table 2 · Table 2
Ham sausage found nitrite by colorimetric mode, added 0 umol L-1	ND	—	—	Table Qualitative	6 · Table 2 · Table 2
Ham sausage found nitrite by colorimetric mode, added 25 umol L-1	25.13 umol L-1	0.000025129999999999998 mol L-1	RSD 0.72%	Table Exact Reported	6 · Table 2 · Table 2
Ham sausage found nitrite by colorimetric mode, added 50 umol L-1	49.73 umol L-1	0.00004972999999999999 mol L-1	RSD 0.93%	Table Exact Reported	6 · Table 2 · Table 2
Pickled vegetables found nitrite by colorimetric mode, added 0 umol L-1	ND	—	—	Table Qualitative	6 · Table 2 · Table 2
Pickled vegetables found nitrite by colorimetric mode, added 25 umol L-1	25.71 umol L-1	0.00002571 mol L-1	RSD 0.74%	Table Exact Reported	6 · Table 2 · Table 2
Pickled vegetables found nitrite by colorimetric mode, added 50 umol L-1	49.63 umol L-1	0.00004963 mol L-1	RSD 0.18%	Table Exact Reported	6 · Table 2 · Table 2

Selectivity, 7-day stability and reproducibility tests

Cu-MOFs/EGP · Electrode

Interferents at 100 times NO2- concentration; daily detection for 7 days; five independently prepared sensors tested.

Context: Composite sensing platform.
Measurement source: 6 · 3.4 The analytical performances of the dual-mode sensor · Fig. S2

Property	Reported value	Normalised value	Uncertainty	Origin and quality	Source
Interferent concentration relative to NO2-	100 times that of NO2-	—	—	Text Exact Reported	6 · 3.4 The analytical performances of the dual-mode sensor · Fig. S2A-B
Colorimetric reproducibility RSD across five sensors	0.44%	—	—	Text Exact Reported	6 · 3.4 The analytical performances of the dual-mode sensor · Fig. S2D
Electrochemical reproducibility RSD across five sensors	0.69%	—	—	Text Exact Reported	6 · 3.4 The analytical performances of the dual-mode sensor · Fig. S2D
7-day colorimetric stability RSD	0.75%	—	—	Text Exact Reported	6 · 3.4 The analytical performances of the dual-mode sensor · Fig. S2C
7-day electrochemical stability RSD	1.1%	—	—	Text Exact Reported	6 · 3.4 The analytical performances of the dual-mode sensor · Fig. S2C

Literature comparison table for nitrite detection

Cu-MOFs/EGP · Electrode

Table S1 reports analytical performance of Cu-MOFs/EGP and prior methods in umol L-1.

Context: Composite sensing platform compared with literature.
Measurement source: 3 · Supporting information · Table S1

Property	Reported value	Normalised value	Uncertainty	Origin and quality	Source
SI Table S1 this-work colorimetric linear range lower bound	12.5 umol L-1	0.0000125 mol L-1	—	SI Table Exact Reported	3 · Table S1 · Table S1
SI Table S1 this-work colorimetric linear range upper bound	261 umol L-1	0.000261 mol L-1	—	SI Table Exact Reported	3 · Table S1 · Table S1
SI Table S1 this-work electrochemical linear range lower bound	0.625 umol L-1	6.25e-7 mol L-1	—	SI Table Exact Reported	3 · Table S1 · Table S1
SI Table S1 this-work electrochemical linear range upper bound	196 umol L-1	0.000196 mol L-1	—	SI Table Exact Reported	3 · Table S1 · Table S1