In the present work a new HPLC method for the determination of mercury species in biological samples with ICP-MS detection was developed. Separation of inorganic (Hg 21 ) and methylmercury (CH 3 Hg 1 ) was accomplished on a Hamilton PRP-X200 polymer-based cationexchange column with a mobile phase of 50 mmol l À1 pyridine, 0.5% w/w L-cysteine and 5% v/w MeOH, at pH 2, within 8 min. The influence of chromatographic parameters, such as pH, salt concentration, organic modifier, and ion-pair reagent on the retention behaviour was evaluated. Based on peak areas, the experimental detection limits for inorganic and methylmercury were 0.05 and 0.08 mg Hg l À1 , which corresponds to an absolute detection limit of 1.0 and 1.6 pg of mercury (20 ml injection volume). The liquid chromatographic method was successfully applied to the determination of inorganic and methylmercury in the two certified reference materials DORM-2 and DOLT-3, after a rapid and simple sample preparation procedure using hydrochloric acid.

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The polymer pilot test performed in the 8 TH sandstone reservoir in Austria shows incremental oil production. Soon after increasing oil cuts were detected, polymer was back-produced from the wells which were showing the oil production response. The polymer concentration increased to about 100 ppm in the back-produced water.Size Exclusion Chromatography was used to determine the molecular weight distribution of the back-produced high molecular weight polymers (HPAM). The results showed that careful sampling is required to avoid degradation of polymers during the sampling procedure. Analyzing pressurized samples revealed that some degradation of polymers from the original average molecular weight of 20 MDa to 8 MDa occurred.To investigate where in the surface facility-injection-reservoir-production system degradation took place, specific field tests and laboratory experiments were performed.Chemical and biological degradation was excluded as reservoir conditions are benign (50°C, 20,000 ppm) and nitrogen blanketing and biocides are used.At the surface facilities, no degradation was detected. Swabbing and laboratory experiments showed that severe mechanical degradation occurs in injection wells if injection is performed under matrix injection conditions owing to high flow velocities in the near-wellbore. However, induces fractures are substantially decreasing mechanical degradation. To avoid severe degradation of HPAM, the flow velocities in the near-wellbore and related mechanical degradation have to be evaluated and the injection designed accordingly.In the reservoir, polymers are not degraded as the flow velocities are low. Sucker Rod Pumps as used in the production wells in the polymer pilot area do not lead to polymer degradation. This means surface polymer samples can be taken to investigate the degradation in the injection well.Surface sampling has to be performed pressurized to avoid high shear rates and oxygen in the samples.

Four main areas of uncertainty can be described in polymer-injection projects:1. Are we able to deliver the polymer solutions at the required quality to the wellhead? 2. Are we able to inject polymers at the required quantity and quality? 3. Are we producing sufficient incremental oil? 4. Are we able to separate and treat oil and water cost-effectively after polymer breakthrough? The monitoring program that was developed for the polymerinjection pilot aims to reduce the uncertainty and quickly identify operational difficulties, as described in the following:• Polymer quality at the wellhead: The polymer concentration and viscosity of the "source" solution and injected polymer solution were measured at various locations in the surface facilities. A quality check of the delivered polymer (including a filter ratio test of the dissolved polymer) was performed, the biological activity monitored, iron content measured, and polymer solution investigated for "fish eyes." The monitoring program enabled us to identify challenges related to shearing the polymers after changing the operating envelope, to identify problems related to biological activity, and to ensure data quality for interpretation of the pilot. • Injectivity and degradation: Monitoring involved wellheadand bottomhole-pressure measurements, repeated falloff tests, and visual observation of the polymer solutions in the well. The results showed the mobility reduction of the polymer solutions and an indication of induced fractures. Combining the various measurements led to identification of an operational issue-the injectivity decreased more than expected from polymer rheology and prepilot water-quality assessment. The reason was the combination of fines and small oil droplets existing in the injection water with polymer-and biologicalgenerated mass that plugged the pores during injection.