Reciprocating cylinder method

Apparatus III reciprocating cylinder method, inner tube (5-40dips/min), outer tube (300 mL)... 

The reciprocating cylinder was proposed by Beckett and coworkers (13) and its incorporation into the USP followed in 1991. The idea to generate a new test method came from a... 

Hanson WA. Handbook of Dissolution Testing. Alternative Methods—reciprocating cylinder. Vol.2. Eugene, OR Aster Publishing Corporation, 1991 42-45. 

USP Dissolution Apparatus 1 (basket) and 2 (paddle) are commonly used for immediate-release formulations. USP Apparatus 3 (reciprocating cylinders) is the system of choice for testing extended-release products or a dosage form that requires release profiling at multiple pH levels and time points. Low-dose products may require the use of flow-through analysis or other low-volume test techniques (noncompendial 100- or 200-mL dissolution vessels). Once the apparatus is selected and has been shown to be suitable during method development, no further evaluation of another apparatus is required during validation. 

USPApparatus III (bio-dis dissolution method with reciprocating cylinder) useful forthe bead-type dosage forms... 

Apparatus IV flow-through method 4-16mL/min Apparatus V paddle over disc Apparatus VI cylinder method Apparatus VII reciprocating holder method... 

Numerous dissolution methods (not limited to those officially prescribed) must be available to ensure proper discrimination as well as the use of various media. The preferred dissolution apparatus is USP I (basket), II (paddle), or IV (flow through cell). USP apparatus III (reciprocating cylinder) could be considered in some cases. An aqueous medium, either water or a buffered solution preferably not exceeding pH 6.8 (or 7.2), is recommended, other pH must be justified. For poorly soluble drugs, the addition of a surfactant may be necessary. 

USP XXIV and the EP describe four additional apparatuses mainly intended for trans-dermal or dermal delivery the paddle over disc (USP V, EP), the extraction cell method (EP), the cylinder method (USP VI, EP) and the reciprocating holder method (USP VII). A large number of other non-compendial methods have been described. Most of them could be categorised as... 

The first method is used most frequently. The next preference is for the last method, mostly used in small compressors due to problems with speed control of electrical motors. Other means of capacity control are very seldom utilized due to thermodynamic inefficiencies and design difficulties. Energy losses in a compressor, when capacity regulation is provided by lifting the suc tion valves, are due to fric tion of gas flowing in and out the unloaded cylinder. This is shown in Fig. 11-84 where the comparison is made for ideal partial load operation, reciprocating, and screw compressors. 

Reciprocating compressor capacity may easily be adjusted by changing compressor speed, changing compressor cylinder clearance, unloading compressor cylinder inlet valves, recycling gas from unit discharge to unit suction, or a combination of these methods. All these methods may be accomplished either manually by the operator or automatically by the control panel. 

A Debye-Scherrer camera consists of a metal cylinder provided with a photographic film. The primary beam is perpendicular to its axis. The distance between two symmetrical lines, produced by the intersection of a cone with the cylinder, is 46R, 6 being the Bragg angle (in radians) and R the radius of the camera. The interval is derived from Bragg s law. The powder method gives us only the norms of the reciprocal vectors. The set of norms corresponds to the projection of the reciprocal lattice onto a straight line. 

Where conventional lubricants cannot be applied for reasons of incompatibility with the working fluid at operational conditions of temperature and pressure, it has been found necessary to develop alternative methods, and dry lubrication" using solid lubricants has been adopted for cryogenic applications. Components that lend themselves to.this treatment are bearings and seals for rotating shafts and pistons and cylinders in reciprocating systems. 

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