Table 2.

Electrochemical sensors based on carbon nanotubes SPEs.

Analyte	Electrode *	Technique *	Linear Range (µmol L−1)	LOD (µmol L−1)	Samples	Reference
8-hydroxyguanine	MWCNTs-COOH/SPCE	DPV	3.0 × 10−1–12	5.7 × 10−1	Electrochemical monitoring of stability of 8-hydroxyguanine	[125]
Antihistamine drug bilastine (BIL)	MWCNTs-SPCE	CV and LSV	2.29 × 10−1–4.58	1.3 × 10−1	Pharmaceutical formulations and urine	[119]
Bilirubin	MWCNTs-SPCE and GO-SPCE	CV	MWCNTs 0.5–500 and graphene 0.1–600	MWCNTs (3.0 ± 0.22) × 10−4 and Graphene (1.0 ± 0.18) × 10−4	Blood serum	[120]
Catechol	f-MWCNTs/SPCE	CV	8.0 × 10−2–725	3.0 × 10−2	Water	[113]
Caffeic acid	MWCNT/SPEs	DPV	2.0–50.0	0.2	Tea	[124]
Cd(II)	CuF/GCE and CuF/CN/SPE	ASV	5 × 10−4–5 × 10−1 for CuF/GCE and 3 × 10−4–3 × 10−1 for CuF/CN/SPE	CuF/GCE: 1.7 × 10−4 and CuF/CN/SPE: 1.3 × 10−4	Water	[126]
Cd(II) and Pb(II)	RGO-MWCNT-AuNP/SPE	SWSV	8.90 × 10−3–7.12 × 10−1 for Cd(II) and 4.83 × 10−3–3.86 × 10−1 for Pb(II)	6.23 × 10−3 for Cd(II) and 1.45 × 10−3 for Pb(II)	Soil	[114]
Diclofenac	SPCE/MWCNTs-COOH	DPAdSV	1.0 × 10−4–1.0 × 10−2	2.8 × 10−5	Water	[127]
Dopamine	mMWCNTs/SPE	CV	5–8	4.3 × 10−1	Spiked human blood serum	[121]
Dopamine	Modified GCE and SPCE with sodium bis[N-2-oxyphenyl-5-bromosalicylideneiminato-ONO] ruthenate(III), MWCNTs and Nafion	CV, DPV, and flow injection amperometry	up to 326	(7.18 ± 2.61) × 10−1	Ampoules of dopamine hydrochloride	[128]
Estriol	CNT-SPCE	Amperommetry; CV	1–1.0 × 103	5.3 × 10−1	Commercial pharmaceutical formulation	[123]
H2O2	SPCE/PAKB NPs/CNTs	CV and amperometry	20–6.48 × 103	2.7	Milk and water	[129]
Imidacloprid	IL-SWCNT/SPC	LSV; CV	11–5.75	8.2 × 10−1	Spiked commercial honey	[130]
Indole	MWCNTs-CS/SPCE	CV; DPV	4.27 × 10−2–8.54 × 10−1	4.27 × 10−3	Plasma	[131]
K4FeCN6, H2O2 and nicotinamide adenine dinucleotide (NAD+/NADH)	MWCNT/GP/SPCE	CV	10–1.0 × 103	3.1 for K4FeCN6, 7.1 × 106 for H2O2 and 3.6 for NADH	---	[132]
Kojic acid	MWCNTs-CS/SPCE	DPV	20–5.0 × 103	16	Apple vinegar and Rice vinegar	[133]
Levothyroxine (LT4)	SPCEs, containing CNTs, graphene, and AuNPs individually	DPV	5.0 × 10−4–3.0 × 10−3 (for CNT)	1.5 × 10−1	Diluted fetal bovine serum	[134]
Methyldopa	AuNPs/CNT/SPCE	Flow injection amperometry	2.0 × 10−1–100	1.0 × 10−1	Pharmaceutical and urine	[135]
Ochratoxin	SPE on PET and PDMS, coated with SWCNTs and immobilized with anti-OTA antibodies.	CV	2.48 × 10−5–2.48 × 10−3	PET 1.98 × 10−4 and PDMS 3.22 × 10−4	Grape juice and wine	[136]
Paracetamol, Ibuprofen and Caffeine	SPCE, SPCNTE, SPCNFE, and SPGPHE	DPV	1.32 × 10−2–6.62 × 10−1 for PA, 9.70 × 10−3–4.85 × 10−1 for IB and 1.03 × 10−2–5.15 × 10−1 for CF	5.95 × 10−1 for PA, 10.7 for IB, and 1.03 for CF	Spikes tap water and hospital wastewater	[137]
Paraquat	SPCE-CNT/Nafion	CV; DPV	5.4 × 10−1–4.3	1.7 × 10−1	Natural water	[118]
Piperazine	CNTs-Nafion/GCE and SPCE	LSV; DPV	4.0 × 10−1–12	1.1 × 10−1	Human Plasma	[138]
Polyphenols content	GCE and SWCNTs-SPCE	SWV	---	---	Red wines	[139]
Secretion of electroactive metabolite(s) in the extracellular matrix	MWCNTs/SPE	CV	1.0 × 105–1.1 × 106 OD600	1.0 × 105 OD600	Bacterial cell suspensions	[140]
Stimulant modafinil	SPE-CNT	AdSWV	7.5–300	2	Saliva	[122]
Tl(I)	SPCE/MWCNTs/BiF	ASV	1.0 × 10−2–1	2.8 × 10−3	Spiked water from the Vistula River	[115]
Thrombin	SWCNTs/SPCE	CV	1.0 × 10−1–1	2.0 × 10−5	---	[141]
U(VI)	MWCNTs/SPE (electrode III) and IL-MWCNTs/SPE (electrode VII)	Potentiometry	10–1.0 × 105 for electrode III and 4.7 × 10−1–1.0 × 105 for electrode VII	10 for electrode III and 4.7 × 10−1 for electrode VII	Water	[116]
Zn(II), Pb(II) and Cu(II)	SPCE/CNTs/AuNP	DPASV	Zn2+: 1.51 × 10−2–1.84; Pb2+: 4.78 × 10−2–5.79 × 10−1, and Cu2+: 1.56 × 10−2–1.89 × 10−1	Zn2+: 1.53 × 10−2–5.35 × 10−2; Pb2+: 7.24 × 10−3–2.41 × 10−2; Cu2+: 1.57 × 10−3–5.19 × 10−3 for Cu2+	---	[117]

* The explanations of the abbreviations in Table 2 can be found in the Supplementary Materials.