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Table 1 Performance characteristics of existing methods of LNP

From: Development of membrane electrodes for selective determination of lisinopril in pharmaceuticals

Sl. no.Reagent(s)Technique and methodologyRangeRemarksReference
1NaOHPotentiometric titration of LNP with 0.1 M NaOH350 mgLess sensitive methodBritish Pharmacopoeia, 1998
2Mixture of phosphate: acetronitrile (96:4 v/v)Chromatographic assay using C8 (octylsilyl-silane) column at 50 °C with UV detection at 215 nm-Sophisticated instrument requiredUS Pharmacopoeia, 2000
3NaOH, NaOMe, methanolic KOH, CH3COOH, HClO4Titration of LNP with
(a) HClO4
2–20 mgLarge sample size (in milligramme levels) requiredBasavaiah et al., 2010
(b) NaOH1–10 mg
(c) NaOMe and2–20 mg
(d) KOH5–15 mg
4N-BromosuccinimideUltraviolet spectrophotometric determination by measuring absorbance at 353 nm10–200 μg ml−1Less sensitive, use of organic solvents, measure at shorter wavelengthRahman et al., 2007
Chloranil-24–600 μg ml−1
5ChloranilSpectrometric detection of LNP at 346 nm4–20 μg ml−1pH dependent, use of toxic reagentsEl-Yazbi et al., 1999
DichloneMeasurement of absorbance of LNP-Dichlone at 580 nm40–120 μg ml−1
AcAc and HCHOSpectrometric detection of LNP at (a) 356 nm6–42 μg ml−1
(b) 475 nm (fluorescence intensity)0.03–0.27 μg ml−1
67,7,8,8-TetracyanoquinodimethaneSpectrometric assay of LNP using TCQD by measuring absorbance at 743 nm2–26 μg ml−1Expensive chemicals and organic solvent requiredRahman et al., 2005
p-ChloranilSpectrophotometric assay of LNP using p-chloranil by measurement of C-T complex at 525 nm25–300 μg ml−1
7(a) NaClO4- phenyl hydrazineMeasurement of absorbance of condensation product of lisiniopril with NaClO4− phenyl hydrazine at 362 nm40–200 μg ml−1Shorter wavelength employed for measurement of absorbanceEl-Gindy, Ashour, Abdel-Fattah, and Shabana, 1991
o-PhthalaldehydeSpectrofluorimetric measurments at 340 and 455 nm of excitation and emission wavelengths20–180 ng ml−1Less cost-effective technique
Mobile phase of methanol, water, and triethylamine in a ratio of 50:50:0.1 v/v and (pH 2.6)HPLC analysis using 250 × 4.6 mm (i.d.) ILS Hypersil Silica (5 μm particle size) column and with UV detection at 210 nm4–28 μg ml−1Sophisticated analytical technique required
o-Phthalaldehyde, 2-mercaptoethanol, borate buffer pH 9.5The fluorescence of the reaction product measured upon excitation at a maximum of 340 nm with emission wavelength at 455 nm20–180 ng ml−1Sophisticated analytical technique required
81-Fluoro-2,4-dinitrobenzene (FDNB)Measurement of absorbance at 356.5 and 405.5 nm20–120 μg ml−1Less sensitive methodParaskevas et al., 2002
9(a). Ninhydrin
i. Initial rate
Measurement of absorbance of product at 595 nm10–50 μg ml−1Kinetic studies; organic solvent used, rate is critically dependent on experimental variablesNafisur et al., 2005
ii. Rate-constant
(b) Ascorbic acidMeasurement of absorbance of product at 530 nm5–50 μg ml−1
10NinhydrinMeasurement of absorbance at 600 nm10–150 μg ml−1Organic solvent requiredAsad et al., 2005
11NinhydrinMeasurement of absorbance at 410 nm10–40 μg ml−1Rajasekaran and Udayavani, 2001
12NinhydrinMeasurement of absorbance of LNP-ninhydrin reaction product at 420 nm5–50 μg ml−1Less sensitive methodBasavaiah et al., 2009
13Dimethylsulphoxide, methanol, and 2,4-dinitrofluorobenzeneMeasurement of coloured product formed between lisinopril and 2,4-dinitrofluorobenzene in methanolic medium at 400 nm4–24 μg ml−1Less sensitive and toxic solvents usedRazak et al. 2003
 The differential pulse polarographic measurement was performed with a – 50-mV pulse amplitude. The polarograms were recorded from − 500 to − 1200 mV vs Ag/AgCl reference electrode at a scan rate of 10 mV s−14–14 μg ml−1Less cost-effective, less robust, and rugged method
14(a) 0.1 M Phosphate buffer (pH 2.8)– methanol (75:25 v/v)Measurement of absorption by
A. 1st derivative spectrometry at
(a) 268 nm
0.604–2.402 mg ml−1Derivative spectrometry and less sensitive methodsBonazzi et al., 1997a, b
(b) 267.2 nm
B. 2nd derivative absorption spectrometry at
(a) 270.4 and
(b) 271.6 nm
(b) Acetonitrile–20 mM sodium heptansulfonate (pH 2.5, 1:1 v/v)HPLC analysis with UV detection at 215 nm using enalapril as internal standard0.024–0.056 μg ml−1Sophisticated analytical technique required
15NaOHSecond derivative absorption spectrophotometric determination at 220 and 340 nm30-2000 μg ml−1Less sensitive methodDurisehvar and Hulya, 1999
16LNP in waterMeasurement of drug by
(a) UV spectrophotometry at 206 nm
3.2–35.2 μg ml−1Derivative spectrometric technique, less cost-effective methodBeata, 2005
(b) first derivative spectrometry at 204 and 217 nm
(c) second derivative spectrometry at 209 and 221 nm
(d) third-order spectrometry at 211, 217, and 223 nm
17MethanolFirst derivative spectrometric measurement of LNP and 269.6 nm25.6–129.5 μg ml−1Derivative spectrometric technique, less sensitive, less cost-effective methodErk, 1998
180.1 M HClSecond derivative spectrometric measurement at 219.4 nm5–15 μg ml−1Derivative spectrometric technique, less cost-effective methodPrasad et al., 1999
19LNP solutionDerivative spectrometric measurements at 300, 271, 242, and 213 nm5–30 μg ml−1Less cost-effective methodJain and Agrawal, 2000
20LNP solutionDerivative spectrometric measurement of LNP-Less cost-effective methodMashru and Parikh, 2000
21Mobile phase of 7:93 (v/v) Acetonitrile–25 mM potassium dihydrogen phosphate (pH 5)HPLC analysis using a 4.6 mm × 20 mm, 3.5 μm particle size, C18 column, and UV detection at 215 nm0.08–1 mg ml−1Sophisticated instrument, less cost-effective methodIvanoic et al., 2007
22Mobile phase of acetonitrile:water (20:80 v/v) (pH 3.8)HPLC analysis using LiChrosorb RP -C18 column (5 μ, 20 cm × 4.6 mm) with UV detection at 213 nm1.5–56 μg ml−1Sophisticated instrument, less cost-effective, and less sensitive methodNevin and Murat, 1999
23-Reversed phase HPLC analysis-Sophisticated instrument, less cost-effective methodSane et al. 1992
24Mobile phase of potassium phosphate buffer (pH 2.2, 30 mM):acetonitrile (91:9, v/v) flow rate 1.0 ml min-1HPLC analysis using platinum EPS C8 (250mm × 4.6 mm i.d.5 μm column, with UV detection at 215 nm12.5–37.5 μg ml−1Sophisticated instrument, less cost-effective methodChristopher et al., 2004
25Mobile phase: methanol–dichloromethane–glacial acetic acid (9.0:1.0:0.1, v/v/v)HPTLC analysis with aluminium-backed layer of silica gel 60 F254400–2000 ng/bandSophisticated instrument, less cost-effective methodPandya et al., 2017
26-Gas chromatographic separation performance-Sophisticated instrument, less cost-effective methodAvadhanulu and Pantulu, 1993
27Sodium cholate and 40 mM sodium dodecyl sulphate in 25 mM phosphate buffer (pH 9)Capillary electrophoretic separation of lisinopril isomers-Applicable for separation of isomersQin et al., 1993
28Borate buffer (50 mM) pH 8.5Capillary electrophoretic separation with fused-silica ‘bubble’ capillary 58.5 cm (50 cm effective length) × 50 mm I.D.; applied voltage, 25 kV; detection 220 nm; temperature 50 °C; injection time 10 s.-Sophisticated instrument, less cost-effective methodGotti et al. 2000
297-Chloro-4-nitrobenzofurazan and ethyl acetateThe fluorescence intensity of the lisinopril derivative with 7-chloro-4-nitrobenzofurazan in ethyl acetate measured at 528 nm with excitation at 465 nm50–1000 ng ml−1Sophisticated instrument requiredEsra et al., 2003
30o-Phthalaldehyde, 2-mercaptoethanol borate buffer medium, pH = 10.6Spectrofluorimetric measurement of reaction product of lisinopril with o-phthalaldehyde in the presence of 2-mercaptoethanol in borate buffer medium (pH = 10.6) at 455 nm with excitation at 346 nm0.3–10.0 mg l−1Sophisticated instrument requiredZacharis et al. 2004
31Sodium nitrite, ammonium sulphamate, hydrochloric acid sodium hydroxide, Britton-Robinson Buffers of pH range 1.0–8.0, dichloromethaneThe polarographic analysis at potential scan rate of 10 mV/s using DME, Ag-AgCl, and a graphite rod as electrodes. The polarographic modes over the potential range − 0.2–1.6 V versus Ag-AgCl were by
(a) Direct current polarographic method
2–24 μg ml−1Sophisticated instrument requiredEl-Enany, Belal, and Al-Ghannam, 2003
(b) Direct potential polarographic method1–20 μg ml−1
320.5 M Acetic acid and 10 mM copper sulphatePolarographic analysis at potential range from +200 to − 1 V at scan rate of 100 mV s−1 using calomel reference electrode.Up to 20 μg ml−1Sophisticated instrument requiredRajasekaran and Murugesan, 2001
33Phosphotungstic acid (PTA), PVC, and THFConstruction, validation, and use of ion-selective electrode for potentiometric determination of lisinopril5 × 10−5–2.4 × 10−3 mol l−1Wide linear range, cost-effective, and highly skilful operator not requiredPresent methods
Phosphomolybdic acid, PVC, and THF