Two chromatographic methods were developed and validated for the simultaneous
determination of Mometasone furoate (MO) and Formoterol fumarate dihydrate (FOR). Combination
of MO and FOR is used for the treatment of asthma in patients suffering from reversible
obstructive airway disease. The first chromatographic method was based on using aluminum
TLC plates pre-coated with silica gel GF254 as the stationary phase and chloroform:ethyl acetate:
methanol:toluene:formic acid (5:2:2:2:0.1, by volume) as the mobile phase followed by densitometric
measurement of the separated bands at 233 nm. The second method is a high performance liquid
chromatographic method for the separation and determination of MO and FOR using reversed
phase C18 column with isocratic elution. The mobile phase composed of methanol: 0.5% ammonium
acetate pH adjusted with acetic acid (80:20, v/v) at a flow rate of 1.0 mL/min. Quantitation
was achieved with UV detection at 220 nm. The specificity of the developed methods was investigated
by analyzing the pharmaceutical dosage form. The validity of the proposed methods was
assessed using the standard addition technique. The obtained results were statistically compared
with those obtained by the reported methods, showing no significant difference with respect to accuracy
and precision at p = 0.05.

Realistic implementation of ion selective electrodes (ISEs) into environmental monitoring programs has always been a challenging task. This could be largely attributed to difficulties in validation of ISE assay results. In this study, the electrochemical response of amoxicillin trihydrate (AMX), ciprofloxacin hydrochloride (CPLX), trimethoprim (TMP), and norfloxacin (NFLX) was studied by the fabrication of sensitive membrane electrodes belonging to two types of ISEs, which are polyvinyl chloride (PVC) membrane electrodes and glassy carbon (GC) electrodes. Linear response for the membrane electrodes was in the concentration range of 10-10 mol/L. For the PVC membrane electrodes, Nernstian slopes of 55.1, 56.5, 56.5, and 54.0 mV/decade were achieved over a pH 4-8 for AMX, CPLX, and NFLX, respectively, and pH 3-6 for TMP. On the other hand, for GC electrodes, Nernstian slopes of 59.1, 58.2, 57.0, and 58.2 mV/decade were achieved over pH 4-8 for AMX, CPLX, and NFLX, respectively, and pH 3-6 for TMP. In addition to assay validation to international industry standards, the fabricated electrodes were also cross-validated relative to conventional separation techniques; high performance liquid chromatography (HPLC), and thin layer chromatography (TLC)-densitometry. The HPLC assay was applied in concentration range of 0.5-10.0 μg/mL, for all target analytes. The TLC-densitometry was adopted over a concentration range of 0.3-1.0 μg/band, for AMX, and 0.1-0.9 μg/band, for CPLX, NFLX, and TMP. The proposed techniques were successfully applied for quantification of the selected drugs either in pure form or waste water samples obtained from pharmaceutical plants. The actual waste water samples were subjected to solid phase extraction (SPE) for pretreatment prior to the application of chromatographic techniques (HPLC and TLC-densitometry). On the other hand, the fabricated electrodes were successfully applied for quantification of the antibiotic residues in actual waste water samples without any pretreatment. This finding assures the suitability of the fabricated ISEs for environmental analysis.