AQA - Quality Assurance for your analysis addista® - AQA for cuvette tests Confidence in Your Analysis with HACH LANGE Glossary - In other words

AQA stands for Analytical Quality Assurance. It embraces all measures that corroborate and document your analysis. Why is AQA necessary? AQA gives you confidence in your analysis. It examines and checks it. We will be pleased to help you achieve AQA with the HACH LANGE range of products and services!

All you need to get started with AQA is a pencil and an addista® package. The addista® system means there's no need to carry out any preparations. The set contains:

85 ml standard solution for up to 8 different parameters. 2 Ring Test solutions of different concentrations - participation in HACH LANGE Ring Tests is free of charge. Instructions and evaluation method for sample spiking with a standard solution to enable matrix effects to be detected.

Every day you make decisions about process controls, investments and direct and indirect discharges on the basis of your analysis results. Clearly your analysis must be safe and reliable. We guide you along the path to quality assurance. The package includes:

Please contact us on 0161 872 1487.

The aim of analytical quality assurance (AQA) is to ensure constant high quality and far-reaching acceptance of continuously recorded analytical measured values by regulatory authorities. The elements of AQA include:

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Abbreviation of Analytical Quality Assurance

An exact and unambiguous result is characterized by precise and accurate measurement results. This means that the individual results have a low range of scatter and clearly bracket an average value.

Sum of all analysis results of a multiple determination divided by the number of determinations. Adding an exact amount of a known standard to a sample of unknown composition. An analysis is then carried out to check whether the standard is accurately detected or whether the measurement is distorted by substances in the sample (i.e. by the matrix). The standard and the sample are brought together. 1 part sample and 1 part standard are mixed. For example, 5 ml sample are mixed with 5 ml standard. The sample is thus diluted in a ratio of 1:2 and the dilution factor is 2. Example using figures: Result of the sample analysis: 20 mg NH4-N Concentration of the standard: 22 mg/l NH4-N, spiking rate: 11 mg/l NH4-N (The spiking rate is equal to half the standard concentration if the sample and the standard are present in equal volumes, as the sample dilutes the standard by a factor of 2.) Result of analysis of sample/standard mixture: 19,5 mg/l NH4-N Spiking rate = Sample/Standard mixture - (Sample / 2) Spiking rate = 19.5 mg/l - (20 mg/l / 2) = 9.5 mg/l The spiking rate is close to the actual value and the sample matrix therefore contains no interferences.

Operational analysis methods often offer a good alternative to the usually more complex standard methods. The question of comparability to the reference method is always in the foreground. At regular intervals samples are divided and analysed in parallel by independent accredited DIN laboratories.

Measurement tolerances determined over the total measurement range of a test in field tests.

The measurement result is close to the correct value. The individual measurement results of multiple determinations may be scattered around the correct result but their average is close to the correct value.

Documentation of Analytical Quality Assurance. Software from Hach Lange for the documentation of all AQA activities.

It must at all times be possible for third parties to interpret analysis findings, analysis procedures and analysis intervals. This can only be achieved if detailed and consistent analysis documentation is available. The necessary documentation measures include:

Dilutions are prepared in a measuring flask. A defined sample volume is introduced into the flask and made up to the mark with distilled water.

Dilution factor F = 2 F = 4 F = 5 F = 10

Sample volume introduced into 50 ml measuring flask 25 ml 12,5 ml 10 ml 5 ml

Dilution factor F = 2 F = 4 F = 5 F = 10

Proportions 1 part sample + 1 part dist. water 1 part sample + 3 part dist. water 1 part sample + 4 part dist. water 1 part sample + 9 part dist. water

F = Final volume (measuring flask) / sample volume NB: The dilution ratio 1:1 is often wrongly taken to be the ratio for 1 part sample + 1 part distilled water. In fact it refers to the undiluted sample.

The matrix of a sample is the sum of all substances in the sample: dissolved compounds, solids/turbidities, colorants. The analysis may be influenced by the sample matrix. Interference by ions and colorants may cause high or low-bias results to be obtained. Matrix effects can be detected by carrying out plausibility checks.

Maximum acceptable variation coefficient compatible with a predefined level of quality of the analysis.

Analysis of a sample at least twice in accordance with the working procedure. The result is documented as the average of the two analyses.

Samples may contain substances (matrix) that falsify an analysis. This can be checked by means of dilution or spiking. 1. Dilution: (see also Dilution) The results obtained from at least two successive dilution steps must be plausible relative to each other. Example:

Dilution No dilution 1 : 2 1 : 4 1: 8

Result 17 mg/l NH4-N 9,5 mg/l NH4-N 5,3 mg/l NH4-N 2,5 mg/l NH4-N

Dilution No dilution 1 : 2 1 : 4 1: 8

Calculated result 17 mg/l NH4-N 19 mg/l NH4-N 21 mg/l NH4-N 20 mg/l NH4-N

In this example the analysis results obtained after successive dilutions are only plausible relative to each other when the sample is diluted by 1:4 and 1:8. Such a step is only meaningful if the dilution does not reduce the sample concentration below the lower limit of the measurement range. 2. Spiking (see also Spiking) An exact volume of a known standard is added to a sample of unknown composition. An analysis is then carried out to check whether the standard is accurately detected or whether the measurement is distorted by substances in the sample (i.e. by the matrix). Example: 1 part sample is mixed with 1 part standard. Analysis of the sample: 20 mg NH4 Concentration of the standard: 22 mg/l NH4 spiking rate: 11mg/l NH4 Sample/standard mixture: 19,5mg/l NH4-N The spiking rate is close to the actual value and the sample matrix therefore contains no interferences.

The individual measurement results correlate closely and exhibit a low level of scatter. The average of the results may differ considerably from the correct result. Precision is not an indicator of accuracy.

This is an external quality control tool. An identical sample is analysed by all participants independently under similar conditions. The individual results are statistically evaluated. Each participant receives an evaluation of his results, including information about the accuracy and precision of his analysis.

Documentation of the correct spiking rate, the confidence interval and the individually measured spiking rate for a given cuvette test.

Documentation of the differences between the highest and lowest measurement results of a multiple determination.

Tool for documenting the analysis of standard solutions. The correct value and acceptable tolerances are entered, as is the analysis result and all relevant data

Analysis of a sample with a known parameter concentration. The concentration should detected within the acceptable confidence interval. This serves as an internal quality control measure for checking the analysis procedure, the reagents used and the accessories.

The results of a multiple determination and the results obtained by all participants in a Round Robin test differ to a greater or lesser degree from the correct value. This is referred to as scatter. Scatter is due to differences in the way people work, measurement fluctuations in the instrument and other resources used, and differences in the working environment. The quality of an analysis is good if the scatter is within a defined zone around the correct value. This is referred to as the scatter width or confidence interval.

Measure of the scatter in % over the total measurement range of a given cuvette test and over all instrument types used.