The rapid determination of chemical oxygen demand in waste waters and effluents by flow injection analysis

Ultrasound-assisted method for determination of chemical oxygen demand

“…the overall process is too long -2-4 h is required for digestion plus additional time for the titration; 2. handling is also considerable, so the likelihood of errors is high and a skilled analyst is required; 3. large amounts of expensive and toxic chemicals are required; 4. straight-chain carboxylic acids are not completely oxidized in the absence of a catalyst (Ag 2 SO 4 ) and might not be completely oxidized even in the presence of this compound; 5. volatile compounds are only oxidized to the extent with which they stay in contact with the liquid media and the heat generated by addition of sulfuric acid to the flask might drive volatile compounds from the solution; and 6. low selectivity, because some inorganic species (Cl -, N O − Several modifications have been proposed to circumvent these drawbacks [2, 3,4,5,6]. In most of these methods the bottleneck continues to be the digestion time required, sometimes 2 h. To reduce the total analysis time, and hence to increase sample throughput, some automatic methods have been suggested, both in flow-injection analysis (FIA) and in segmented flow analysis (SFA) [7,8,9,10,11,12,13]. All these methods for determination of COD use conventional convective-conductive heating devices.…”

Disposable Chemical Oxygen Demand Sensor Using a Microfabricated Clark-Type Oxygen Electrode with a TiO2 Suspension Solution

“…The conventional method presents several disadvantages [7,8], including the long analysis time and the manual processes dependent upon operator skill.…”

Putting the chemistry back into analytical chemistry

“…There is no reason why flow analytical method ologies have to be restricted to the pressures and temperatures typically encoun tered in open-vessel laboratory procedures and thus developments in "high per formance" (HP) FI are to be expected. Liquid and gas chromatographic equip ment is already available for such experiments and the use of on-line heating with thermal ovens (52,53) and microwave ovens (54) is already attracting some at tention. The potential of ultrasound (55) as a means of coupling energy into chem ical systems is yet to be fully exploited (this comment also applies to microwave energy) and there are many possibilities in this area.…”