THE 1993 QUASIMEME LABORATORY-PERFORMANCE STUDY - NUTRIENTS IN SEA-WATER AND STANDARD SOLUTIONS

The 1993 QUASIMEME nutrients laboratory-performance study is presented . The three parts were intended to test various analytical ranges or a spects. Part 1 was a single exercise at three concentration levels, wh ile Part 2 addressed the problem of long-term repeatability testing, b oth using natural seawater samples. Part 3 was also a long-term repeat ability exercise but using nutrient concentrates which required diluti on (by participants) in low nutrients seawater. The results show that at medium and high concentration levels the relative standard deviatio n is about 10% for nitrate + nitrite, nitrite and phosphate, and 30-40 % for ammonia, which is evidently a problem for most analysts. Calcula tions of Z- and P-scores show that 80-90% of the participants meet the target performance at the high concentration level and that the major ity of errors are systematic and consequently should be readily correc table by strict application of reliable procedures.