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Two new simple and accurate methods for determination of quetiapine in tablets-normal phase (NP) and reversed-phase (RP) high performance thin layer chromatography (HPTLC), each with densitometric and videodensitometric detection, were developed and validated. NP-HPTLC was developed with HPTLC silica F 254 plates and hexane-dioxane-propylamine 1:9:0.4 ( v/v ) as mobile phase. RPHPTLC was carried out using HPTLC RP8 F 254 plates with tetrahydrofuran-phosphate buffer, pH 9.0, 5:5 ( v/v ) as mobile phase. The silica gel plates were developed to a distance of 9 cm and RP8 plates to a distance of 4.5 cm. Both analyses were performed in horizontal chambers and scanned with a densitometer at 243 nm and a video-densitometer at 254 nm. Calibration plots were linear in the range 0.2–1.2 μg quetiapine per spot for NP-HPTLC and in the range 0.1–1.1 μg for RP-HPTLC. The precision and accuracy of the four methods were fully compared and no significant differences were observed. The methods can be used in routine pharmaceutical analysis.

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Two new simple and accurate HPTLC methods for analysis of ziprasidone in capsules have been developed and validated. The first method was normal phase chromatography on silica gel F 254 HPTLC plates with hexane-dioxane-propylamine 1:9:0.4 ( v/v ) as mobile phase. The second method was reversed phase chromatography on RP8 F 254 HPTLC plates with tetrahydrofuran-pH 9.0 phosphate buffer 5:5 ( v/v ) as mobile phase. The silica gel plates were developed to a distance of 9 cm and the RP8 plates to a distance of 4.5 cm. Both analyses were performed in horizontal chambers and the plates were scanned by videodensitometry at 254 nm. The calibration plots were linear in the ranges 0.2–1.2 μg and 0.1–1.1 μg ziprasidone (per spot) for the NP-HPTLC and RP-HPTLC methods, respectively. The precision and accuracy of the methods were fully compared between themselves and also with the control method — classical densitometry at 243 nm. No significant differences were observed. The NP-HPTLC method was also used for study of the stability of ziprasidone in solutions. The methods can be used for routine quality-control analysis.

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A new, simple, and accurate TLC method, using normal- and reversed-phase techniques and densitometric detection, has been developed for measurement of quinapril and hydrochlorothiazide in combination tablets. UV detection at λ = 210 nm was used to quantify the analytes. The drugs were chromatographed on silica gel 60 F 254 HPTLC plates and on octadecilsilane (RP-18) TLC plates, in horizontal chambers, with ethyl acetate-acetone-acetic acid, 8 + 2 + 0.5 ( v/v ) and methanol-0.07 m phosphate buffer, pH 2.5, 6 + 4 ( v/v ), respectively, as mobile phases. The active substances were extracted from tablets with methanol (96% < mean recovery < 104%). Calibration curves were constructed in the range 0.4 to 2.4 μg μL −1 for quinapril and 0.25 to 1.5 μg μL −1 for hydrochlorothiazide, with good correlation ( r ≥ 0.998). The precision ( RSD < 4.4%) and accuracy (2.91 < RE < 3.92) were satisfactory for TLC-densitometric determination of quinapril in combination with hydrochlorothiazide in commercial tablets.

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Recently, considerable numbers of poisoning cases have been reported owing to the ingestion of three structurally related organophosphorus pesticides (OPPs): chlorpyrifos (C), quinalphos (Q), and triazophos (T). Normal-phase high-performance thin-layer chromatography (NP-HPTLC) on silica gel 60 F254 and reversed-phase (RP)-HPTLC on silica gel 60 RP-18 W F254 were used to evaluate the retention and separation data for these three pesticides. Optimum separation of pesticides has been achieved on NP-TLC layer with n-hexane—acetone 9:1 (v/v) and on RP-TLC layer using acetonitrile—water 8:2 (v/v) as the mobile phases. The R F values of pesticides increased with increasing acetone content in the case of NP-HPTLC and decreasing water content in RP-HPTLC. Under the chromatographic conditions used, in regard to changes in the mobile phase composition, C adsorbed most strongly on the silica gel RP-18 plate. A linear relationship between R M values and mobile phase composition was established. Densitometric detection was performed at the respective λ max value of the pesticide. The peak resolution (RS) was greater than 1.25 for all compound pairs (C-Q, Q-T, and C-T). The pesticide samples are stable on plate and in solution at room temperature as well as at 4°C. The ultraviolet (UV) spectra (λ max) of the OPPs were apparently unaffected by changes in pH. No significant chromatographic interference was noticed from other OPPs of forensic relevance.

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