Over decades the majority of analytical chemists have focused on the development of new analytical techniques and on improving the limits of detection in various matrices. Analytical chemistry therefore today plays a key role in almost every aspect of life—environment, food, pharmaceuticals and health, quality determination, improvement of various technical processes—and in numerous scientific disciplines, e.g. biology, biotechnology, chemistry and physics. Many of the successes achieved in the aforementioned areas would not have materialized without analytical chemistry.

Particularly since the early 1990s the focus on speciation analysis and the human genome project has led to outstanding developments in the hyphenation of separation techniques and spectroscopy. In these and in other cases analytical tools and other technologies have been integrated, enabling a higher level of interdisciplinary research to understand complex relationships within life and its environment. The pictures gained, however, were often of “static” nature.

Currently, one of the major general trends in science is the increasing interest of researchers in the understanding of process dynamics, forcing particularly analytical chemists to move closer to the origin of the sample and its surroundings. This leads to the increasing importance of process analytical chemistry (PAC). The surroundings of the sample may be the production process, the environment in general or human beings themselves. A well-known example of process control where the shift from off-line sample analysis in the laboratory via at-line monitoring at the location of interest to real on-line or in-line, respectively, has been sucessfully achieved is blood glucose monitoring. In terms of feedback control, recent developments even directly couple the “in-line” blood glucose sensor to an insulin pump.

Another strong trend is miniaturization. The synergies of semiconductor fabrication and communication technology enable innovative instrumentation concepts also in the field of PAC. The process micro-GC and miniaturized ion mobility spectrometers are a few of the impressive outcomes of this trend. The integration of microchip, laser and optical fibre technology makes new applications possible. Outstanding achievements are anticipated in the field of microreaction technology, accelerating in turn new developments within PAC. Within the technological trends high-throughput technologies have to be mentioned. In this field a huge number of reactions is performed, which has to be analysed and evaluated in parallel to the on-going reaction/process development. For this kind of in-time monitoring mainly spectroscopic techniques and laboratory automation have been applied.

The huge potential of PAC still appears to be buried in production processes, for instance, in the chemical and pharmaceutical industry as well as in biotechnology. Non-regulated areas like chemical manufacuring, the polymer industry or food manufacturing often develop convincing solutions. Besides the effects triggering the trends mentioned before, cost reduction, quality enhancement (process analytical technology PAT initiative), environmental protection and safety play a key role. These factors in turn are interrelated: if, for example, an in-line sensor allows optimization of a production process, while performing on-line quality control, the amount of the products which needs to be re-worked is minimized, as well as by-products and energy consumption. Therefore, PAC is a dominating part of process-integrated environmental protection (benign-by-design rather than end-of-pipe approach). In conjunction with process optimization, multivariate data treatment, process modelling and statistical-numerical approaches, for example robust design (Taguchi method), are becoming more and more important. Nevertheless, without “analytical hard facts” the validity of such models cannot be proven, no matter whether the analytical results stem from on-line/in-line sensors or are attained through at-line/off-line analysis.

A crucial step of further introducing more PAC technology in the producing industries clearly depends on whether the sensor being introduced is going to pay off. Plant managers very often are hesitant and often refuse approval, once they get to know the often necessary high up-front investment and the costs of routine quality checks. A total cost-of-ownership analysis remains necessary of course. New concepts of financing, for example risk sharing between users and suppliers (vendors of PAC solutions to a specific process), might help to raise the rate of conviction and to increase the willingness to implement PAC. In any event, a plant manager and his or her staff in particular need a robust and reliable solution and not—with few exceptions—a highly sophisticated technique which needs to be pampered continuously so-to-say.

Overall PAC has become an increasingly important niche within analytical chemistry. In the USA organisations like CPAC (http://www.cpac.washington.edu) and IFPAC (http://www.ifpacnet.org) as well as CPACT (http://www.cpact.com) in the UK have become aware comparatively early of the significance of PAC. In Germany though, PAC activities have not been aligned, but are scattered. In order to help to improve this dilemma a sub-group (Arbeitskreis Prozessanalytik) within the working group Analytical Chemistry of the Society of German Chemists (GDCh) was recently founded focussing on PAC (http://www.analyticjournal.de/aj_navigation/ak_pat.htm). There is no need to say that many developments in PAC are and will remain the intellectual property of the specific companies. However, a platform serving to exchange know-how to a certain degree, organizing project co-operation and eventually succeeding in coming up with necessary standards will further enhance the acceptance of PAC as an important discipline within analytical chemistry and as essential to understand process dynamics. At this point, we would like to mention one successful example regarding an interindustry standard: the New Sampling and Sensor Initiative (NeSSI) co-developed by CPAC.

Recent trends show that the importance of PAC is finally being recognized in academia, which will hopefully result in an increase of training in the field of PAC.

With the trend article on “Process analytical chemistry—future trends in industry” (Anal. Bioanal. Chem. 376:313–315, 2003) we tried to review the most recent technological developments in PAC. With this special issue an attempt is made to update the developments in more depth, to show current trends and to give an outlook of PAC as anticipated for the near future.