Proper collection of a drinking water sample for total coliform/ E.Coli testing is critical to ensure accurate and reliable results. Because total coliform bacteria are used as indicators of potential contamination, even minor sampling errors can lead to false positive results. The sample must be collected in a sterile bottle provided by Princeton Analytical Labs, which contains a preservative (typically sodium thiosulfate) if the water is chlorinated. Do not rinse the bottle prior to sampling, and avoid touching the inside of the cap or bottle.
Select a cold-water tap that is free of attachments such as aerators, screens, filters, or hoses. If possible, choose a tap that is directly connected to the main plumbing line rather than a swivel or leaking faucet. Disinfect the end of the faucet using alcohol or a dilute bleach solution, and allow it to sit briefly. Ordinary 70% rubbing alcohol (iso-propanol) is sufficient. Turn on the cold water and let it run at a steady, moderate flow for 2–4 minutes to flush the plumbing and obtain a representative sample. Reduce the flow to avoid splashing and carefully fill the sterile bottle to at least the indicated line without overfilling. Immediately replace the cap securely.
Label the bottle with the required information (See Chain of Custody Form- location, date, and time of collection) and keep the sample refrigerated at approximately ≤10°C (on ice, but not frozen). The sample should be delivered to the laboratory within 24 hours of collection, preferably as soon as possible. Delays, improper storage, or contamination during sampling can compromise results. Following these steps helps ensure that total coliform testing accurately reflects the microbiological quality of the drinking water.
Proper collection of a drinking water sample for metals testing is important to ensure the results accurately reflect the water quality. Princeton Analytical Labs routinely tests Metal samples for elements such as lead, copper, arsenic, iron, manganese, harness (calcium and magnesium) and others using various analytical methods and instrumentation. The sampling method may differ depending on whether the goal is to measure system water quality or plumbing-related exposure (e.g., lead and copper compliance sampling).
For routine metals analysis (non-lead/copper compliance), select a cold-water tap that does not have a filter attached. Remove any aerator or screen if possible. Allow the cold water to run for at least 2 minutes to flush the plumbing and obtain a representative sample from the distribution system or well. Reduce the flow to avoid splashing and fill the laboratory-provided bottle to the shoulder without overflowing. Do not rinse the bottle prior to sampling, as it may already contain preservative (Nitric Acid).
For lead and copper compliance sampling, the procedure is different: the water must be collected as a first-draw sample after the water has remained unused in the plumbing for at least 6 hours. Do not flush the tap. Place the bottle under the faucet, turn on the cold water at a normal flow, and collect the first liter (or as specified by the Princeton Analytical Labs procedures) immediately.
Metals samples are preserved with nitric acid (HNO₃) to a pH of <2. Laboratory-supplied bottles typically contain the required preservative. If preservative is not pre-added, concentrated nitric acid must be added by trained laboratory personnel immediately after collection. Do not add acid yourself unless specifically instructed and trained to do so, as nitric acid is corrosive and hazardous. After collection, securely cap the bottle and invert gently to mix if preservative is present. Store the sample at ≤6°C (on ice, not frozen) and transport to the laboratory as soon as possible.
Proper collection of a drinking water sample for the tests listed above is important to ensure accurate measurement and regulatory compliance. To collect the sample, use a clean laboratory-supplied plastic bottle (typically polyethylene). Select a cold-water tap and remove any aerators, filters, or attachments if possible. Turn on the cold water and allow it to run for at least 2 minutes to flush the plumbing and obtain a representative sample from the well or distribution system. Reduce the flow to avoid splashing and fill the bottle to the indicated level, leaving minimal headspace in the bottle. Cap the bottle tightly. Do not rinse the bottle if it has been provided by the laboratory for this test.
Nitrate (NO₃⁻) / Nitrite (NO₂⁻) Because nitrite can oxidize to nitrate and microbial activity can alter concentrations, proper sampling, preservation, and storage are essential. There are no preservatives used in the collection of a Nitrate/ Nitrite sample and the holding time is 48 hours. Be sure to schedule a collection when the sample can be brought to the laboratory within the 48 hour hold time. Keep samples on ice or refrigerated until transport to the laboratory.
Total Dissolved Solids (TDS) and Total Suspended Solids (TSS) testing is straightforward, but correct technique is important to ensure representative results. TDS measures the total concentration of dissolved inorganic and organic substances in water while TSS measures the total concentration of dissolved inorganic and organic substances in water and is commonly determined by gravimetric analysis or estimated by conductivity testing. There are no preservatives used in the collection of a TDS and TSS sample and the holding time is 14 days. Keep samples on ice or refrigerated until transport to the laboratory.
Alkalinity testing is important because alkalinity can change over time due to carbon dioxide exchange with the atmosphere or biological activity. Alkalinity measures the water’s buffering capacity, primarily from bicarbonate, carbonate, and hydroxide ions, and is typically analyzed by titration. There are no preservatives used in the collection of an Alkalinity sample and the holding time is 28 days. Keep samples on ice or refrigerated until transport to the laboratory.
Conductivity testing is important to ensure that the measurement accurately reflects the ionic content of the water at the time of sampling. Conductivity measures the ability of water to conduct electrical current, which depends on the concentration of dissolved ions (such as salts, minerals, and inorganic compounds). Because conductivity can change due to contamination, evaporation, or temperature effects, careful sampling and storage are necessary. There are no preservatives used in the collection of a Conductivity sample and the holding time is 28 days. Keep samples on ice or refrigerated until transport to the laboratory.
Proper collection of a drinking water sample for pH testing is important because pH can change rapidly after collection due to temperature shifts, loss or absorption of carbon dioxide, and biological activity. For the most accurate results, pH should ideally be measured in the field at the time of sampling using a calibrated meter. If laboratory analysis is required, special care must be taken during collection and transport. There are no preservatives use in pH sample collection and it is recommended that if the sample is being transported to the laboratory for analysis that the pH measurement be done as soon as possible.
Chloride testing is important to ensure accurate measurement of dissolved chloride ions. Because chloride is a stable inorganic ion, sampling requirements are straightforward, but proper technique is still necessary to obtain representative results. There are no preservatives used in the collection of a Chloride sample and the holding time is 28 days.
Proper collection of a drinking water sample for volatile organic compounds (VOCs) is critical because these compounds can easily evaporate or degrade if samples are not handled correctly. VOCs (such as benzene, toluene, MTBE, TCE, PCE, and others) are by definition, volatile and evaporate into the air very readily. Even small sampling errors—such as trapping air bubbles—can significantly affect results.
To collect the sample, use the 40-mL laboratory-supplied glass vials with Teflon-lined septa caps. These vials are pre-preserved and must not be rinsed prior to use. Select a cold-water tap that does not have an aerator, screen, hose, or filter attached. Remove any attachments if possible. Turn on the cold water and allow it to run for at least 2 minutes to flush the plumbing and obtain a representative sample. Reduce the flow to a gentle stream to avoid turbulence. Fill each vial by allowing water to flow gently down the side of the vial until a convex meniscus forms at the top. Carefully cap the vial so that no air bubbles remain inside. Invert the vial and tap it lightly to check for trapped air; if bubbles are present, discard and recollect the sample. The absence of headspace is essential for valid VOC results. Hydrochloric Acid (HCl) is used as a preservative in the collection of a VOC samples and the holding time, when properly collected, preserved and stored is 14 days.
