Table 2.

Analytical characteristics of selected CE/HPCE methods for analysis of L-arginine/NO pathway metabolites in biological samples

Analytes	Matrix	Sample dilution, derivatization	Detection mode	capillary	Separation buffer	Determined concentrations, comments	LOD or LOQa, comments	Ref.
L-Arg, L-Cit, L-Arginino-succinate	isolated neurons, ganglia, and hemolymph from molluscs.	1:104; fluorescamine	LIF 350–6 nm; PMT	FC	30 mM borate buffer 20 mM SDS, pH 9.5	L-Cit/L-Arg ratios 2.5 (NO-positive B2 cell) and 0.1–0.2 (NO-naive cells).	LODs Arg/Cit 11/15 nM	[101]
3-ntY; nitrosated and chlorinated amino acids	standard mixture	native fluorescence	UVF 200 nm	FC	50 mM borate buffer, variable pH, and EOFM spermine	large volume sample stacking	LOD 2.5–10 nM	[179]
ADMA, and other arginines	human serum control vs. hemodialysed subjects	FITC	LIF	FC	50 mM boric acid 20 mM 3-(cyclohexylamino)1-propanesulfonic acid pH 9.5, 10 or 11.5;	ADMA control 0.3μM, coronary stenosis 1.2 μM	LOD 50 nM (Plasma)	[204]
ADMA, and other arginines	human blud plasma	4-fluoro-7-nitrobenz ofurazan	LIF	FC	borate buffer at pH 9.4; MEKC	includes a MEKC optimization	LOQ 20 μM (UV) 100 nM (LIF); LOQ plasma 125 nM	[205]
NO3−	human urine	1:50	UV 254 nm	FC	chromate, Nice-Pak OFM Anion-BT, pH8.0		ND	[244]
NO2−, NO3−	human serum, urine, brain tissue homogenate	1:10, 1:100	UV 214 nm	FC	10 mM sodium sulfate, 2.5% OFM-OH		LOD25 μg/l	[245]
NO2−, NO3−	rat dorsal root ganglia, biopsy, tissue homogenate	1:103; 1:104 SPME Cl− cleanup	CD	FC	81.5 mM sodiumborate, 25 mM arginine, 0.5 mM TTAH, pH 9.5; ITP injection	NO2−/NO3− were 96-24/231±29 nM;	LOD = 8.9/3.54 nM	[247]
NO2−, NO3−	pheochromocy toma cell line PC12	cell culture supernat ant	UV 214 nm	FC	150 mM Tris-phosphate, 6 μm hexadecyltrimethy-ammonium chloride, pH 7.0	synergistic stimulation of tumor necrosis	LOD NO2− ~25 pM	[254]
NO2−, NO3−	rat brain perfusate	microdia lysis 50 nl/min	UV 214 nm	FC	20 mM phosphate buffer; 2 mM CTAC, pH 3.5	Brain perfusate[NO2−/NO3−] = 3.4/15.5 μM; 1.5 min separation	LOD0.96/2.86μM	[256]
NO2−, NO3−	human serum	1:10	UV 214; LPA	MCE	2 mM Na2HPO4, 12 mM KCL, 412 mM NaCl, 5.43 mM urea, 4,72 mM glucose	6.5 sec separation	LOD NO2−/NO3− = 24/12 μM	[264]
3-ntY	diabetic and control rat urine	1:1 acetonirile	UV 214 nm	FC	150 mM phosphoric acid, 0.5 mM CTAB, pH 6.4	large volume sample stacking	LOD normal/stac King = 1.77/0.08μM	[292]
NO2−, NO3−	identified molluscan neurons, ganglia, and hemolymph	1:1, 1:10, 1:50	UV 214 nm	FC	100 mM NaCI, 2 mM CTAC	highest NO2−/NO3− found in NO positive neurons 2–12 μM	LODs < 4μM	[387]
NO2−, NO3−	rat ASF, plasma	1:1	CD ConCap	FC	100 mM CHES, 40 mM LiOH, pH 9.3, 80 mM spermine; 8% propan-2-ol	Repeatability range5.3–9.8% for various ions	ND	[400]
NO2−, NO3−	human serum	1:10	UV 214 nm	FC	25 mM sodium sulfate, 5% Nice-Pak (OFM) Anion-BT	Repeatability, 6.4–10%; reproducibility, 9–11%; capillaries are stable for over 300 analyses	ND	[406]
NO2−, NO3− NOx	CSF from MS and control subjects, lumbar puncture	1:10;	UV 214 nm	FC	25 mM sodium sulfate 5% NICE-Pak (OFM) Anion-BT	SCF NO2−/NO3− level 304/82 and 34/134 % in active and inactive MS respectively vs. control	ND	[421]
NO2−, NO3−	human saliva	1:100	CD suppressed	CFS	2 mM sodium tetraborate	repeatability, ≤5%; reproducibility, ≤10%	LOD=8–10 μg/l	[429]
NO3−	human serum, urine	1:25, 1:50	UV 250 nm	FC	2.25 mM pyromellitic acid, 6.5 mM NaOH, 0.75 mM HMH, 1.6 mM triethanolamine, pH 7.7	repeatability, 7–11%; reproducibility, 10–15%	LOD=1–2 mg/l	[430]
NO3−	rat urine	1:40	UV 214 nm	FC	25 mM sodium phosphate, 0.5% DMMAPS, 1% Brij-35	repeatability, <3%; no deterioration of capillaries was observed for over300 analyses	LOD=0.5 mg/l	[431]
NO2−, NO3−	human serum	NA	UV 214 nm	FC	750 mM sodium chloride, 5% Nice-Pak OFM Anion-BT	repeatability, <5%; reproducibility, <8%; recovery, 97–114%	LOD=0.1 mg/l	[432]
NO3−	human serum, milk	ion-exchange	UV 235 nm	FC	50 mM DoTAB, 18 mM sodium tetraborate, 30 mM Na2HPO4, 10% propan-2-ol, pH 7.0	repeatability, 1.8–13.5%	LOD=55.8, 2.5 and 8.7 mg/l	[433]
NO2−, NO3−	human serum	NA	UV 200 nm	FC	200 mM lithium chloride, 0.7 mM TTAH, 5 mM triethylamine	repeatability, ≤ 7.3%; reproducibility, ≤6.4%	ND	[434]
NO2−, NO3−	human serum, urine, CSF, human, plant tissue	1:5	UV 214 nm	FC	8 mM Na2HPO4, 4 mM NaH2PO4, 1.4% NaCl, 0.1% poly-ethylene glycol	repeatability, <6%; urinary nitrate analysis was compared with enzymatic assay	LOD=0.3 mg/l	[435]
NO2−, NO3−	human serum, urine	1:100	UV 214 nm	FC	15 mM sodium sulfate, 2.5% (OFM)-OH, pH 8.0	repeatability, 3.0–3.3%; reproducibility, 4.6–5.0%; recovery, 92–113%	LOD=1 μM	[436]
NO2−, NO3− xanthine oxidase, NAD+, NADH	human plasma, serum	NA	UV 214 nm	FC	150 mM sodium chloride, 5 mM Tris-HCl, 2 mM TTAB, pH 7.4	linearity 0.2–1 mM; repeatability ≤3%RSD; reproducibility ≤1%	ND	[437]
GSH, GSSG, GSNO	human erythrocyte extract	1:2	UV 200 nm	CFS	40 mM sodium phosphate, 0.1 mM diethylenetriaminepent aacetic acid, pH 2.2	mobility GSSG, GSH and GSNO was reported	ND	[438]
NO2−, NO3−	rat ASF, plasma sub-microliter samples	1:1	UV 214 nm	FC	50 mM sodium phosphate, 0.5 mM spermine, pH 3	[NO2−/NO3−] = basal ASF 83/102, plasma undetectable/70 μM; lipopolysaccharide induced ASF=103/386 plasma 138/377 μM	LOD=30/10μM	[439]

^aLOD and LOQ values listed here are presented as reported in the original publications cited.

Abbreviations: AA, amino acids; ADMA, asymmetric dimethylarginine; ASF, airway surface fluid; CSF, cerebrospinal fluid; CFS, coated fused silica; CTAC, cetyltrimethylammonium chloride; DMMAPS, 3-(N,N-dimethylmyristylammonio)propanesulfonate; FS, fused silica; LPA, linear photodiode array; MCE, microchip capillary electrophoresis; ND, not determined; PMT, photomultiplier.