Several mathematical formulas were proposed to estabilish the acceptable residual limit.[3�C5] Duloxetine hydrochloride is a selective serotonin and norepinephrine selleck chemicals reuptake inhibitor for oral administration, used for depressive disorders. Its chemical designation is (+)-(S)-N-methyl-��-(1-naphthyloxy)2 thiophenepropylamine hydrochloride [Figure 1]. Its empirical formula is C18H19NOS ? HCl, which corresponds to a molecular weight of 333.38. Its solid oral dosage form is available as a capsule which contains enteric-coated pellets of 22.4 mg, 33.7 mg, and 67.3 mg of duloxetine hydrochloride equivalent to 20 mg, 30 mg, and 60 mg of duloxetine, respectively.[6] Figure 1 Structure of duloxetine hydrochloride Several LC methods have been published for determination of duloxetine in pharmaceutical preparation[7�C11] and human plasma.

[12,13] Reported HPLC methods are not enough sensitive to quantitate the trace level amount of duloxetine HCl present in swab samples. A literature survey revealed that no validated cleaning method for duloxetine is to be found. Due to their high sensitivity and selectivity, analytical methods such as liquid chromatography were previously used for the determination of residues to control cleaning procedures.[14,15] In liquid chromatography, the analysis time can be reduced by using small columns packed with sub-2 ��m particles. In addition, with sub-2 ��m particles, due to the higher efficiency and smaller retention volume, sensitivity is also improved, compared to convetional HPLC.

A dedicated low dispersion system for ultra-high pressure separation (UPLC) with the particle size of the stationary phase reduced down to 1.7 ��m, small dwell and extra column volume is able to work up to 1000 bar (15,000 psi). In such a way, the analysis time could be reduced down to 2�C3 min.[16] The aim of this study was to demostrate the applicability of UPLC to these purposes by developing and validating an UPLC/UV method to determine the residue duloxetine in cleaning control samples. Hence, we have developed a RP-UPLC method for the estimation of trace level residues of duloxetine on swab collected from manufacturing surfaces after production of duloxetine capsules and cleaning of the equipment. The developed analytical method was validated with respect to specificity, linearity, precision, accuracy, robustness, limit of detection (LOD) and quantification (LOQ). The stability of duloxetine samples was also studied. These studies were performed in accordance with established ICH Batimastat guidelines. MATERIALS AND METHODS Chemicals and reagents The certified duloxetine hydrochloride, the working standard was supplied by Dr. Reddy’s Laboratories limited, Hyderabad, India.