More on the ISO 9001:2000
The requirements cover a wide range of topics, including top management commitment to quality, customer focus, adequacy of its resources, employee competence, process management (for production, service delivery and relevant administrative and support processes), quality planning, product design, review of incoming orders, purchasing, monitoring and measurement of its processes and products, calibration of measuring equipment, processes to resolve customer complaints, corrective/preventive actions and a requirement to drive continual improvement of the QMS. Last but not least, there is a requirement to monitor customer perceptions about the quality of the analytical services you provide.
ISO 9001:2000 does not specify requirements for the analytical services you are selling. That is up to your costumers to define, by making clear their own needs and expectations for the analytical service. As an example, if you provide XRF instruments and consumables, they might refer to product specifications, drawings, national or international product standards, supplier's catalogues or other documents as appropriate.